Methods for preparing silicon microparticles, apparatus for preparing silicon microparticles, and silicon microparticles prepared therefrom.

Abstract

This invention relates to a method for preparing silicon microparticles, an apparatus for preparing silicon microparticles, and silicon microparticles prepared therefrom. More specifically, it relates to a method, an apparatus, and silicon microparticles prepared therefrom that can prepare silicon particles with controlled grain size, spherical shape, and a size of several micrometers (μm).

Description

Technical Field

[0001] This invention relates to a method for preparing silicon microparticles, an apparatus for preparing silicon microparticles, and silicon microparticles prepared therefrom. More specifically, it relates to a method, an apparatus, and silicon microparticles prepared therefrom that can prepare silicon particles with controlled grain size, spherical shape, and a size of several micrometers (μm). Background Technology

[0002] The performance improvement of secondary batteries is based on the structural elements of positive electrode materials, negative electrode materials, and electrolytes.

[0003] Among the structural elements, graphite-based materials, which are mainly used as negative electrode materials, have been commercialized in the market due to their excellent electrochemical performance and low cost. However, their application in high-capacity secondary batteries is limited because their theoretical capacity is limited to 370 mAh / g.

[0004] To overcome these limitations, non-graphite anode materials such as silicon, tin, and germanium have been proposed as alternatives. Among them, silicon has a theoretical capacity of 4000–4200 mAh / g, exhibiting almost 10 times higher capacity than graphite, thus attracting considerable attention as a potential graphite replacement. However, compared to its high theoretical capacity, silicon undergoes a significant volume expansion of approximately 400% during charge and discharge, leading to structural damage and a short lifespan.

[0005] To address these limitations, methods have been developed to reduce the size of silicon particles to the micrometer to nanometer scale. Typically, this involves preparing polycrystalline silicon particles or pulverizing silicon materials such as silicon chunks obtained from other industrial sectors or processes.

[0006] Specifically, methods for preparing polycrystalline silicon particles include the Siemens method using a bell-shaped reactor and the FBR method using a fluidized bed reactor.

[0007] The Siemens process involves reacting a silicon rod in a reactor with a silicon source gas to deposit silicon on the surface of the rod. However, due to the limited surface area required for silicon deposition and the limited diameter of the silicon rod resulting from the deposition reaction, continuous processing is not possible. Furthermore, the power consumption per unit weight of silicon is relatively high, leading to limitations in productivity.

[0008] The FBR method involves placing a silicon seed crystal in a crucible filled with hydrogen gas and injecting silicon source gas, causing silicon particles with a diameter of about 1 cm to be deposited around the seed crystal as it falls. Compared with the Siemens method, although silicon production is faster, it suffers from poor silicon quality.

[0009] Previously, to obtain micron-sized silicon from polycrystalline silicon particles prepared in this way, a separate pulverization process was required, followed by an additional sieving process. This resulted in complex processes and reduced efficiency. Furthermore, the pulverization process generates unexpected impurities and fine powder, and it is almost impossible to control the sphericity of micron-sized particles.

[0010] Furthermore, as mentioned above, since the impurity content is also high during the contact process between the silicon seed crystal and the inner wall of the reactor in the fluidized bed reactor, the FBR method also requires an additional purification process.

[0011] Developed methods for the direct preparation of silicon nanoparticles include: methods that prepare silicon nanoparticles by irradiating a target silicon metal with a laser beam; methods that prepare silicon nanoparticles by pyrolyzing a silicon-containing precursor in a solvent using ultraviolet light; and plasma methods that prepare silicon nanoparticles by generating plasma to decompose the silicon precursor.

[0012] On the other hand, if silicon nanoparticles are used as the active material for secondary batteries, there are drawbacks such as reduced dispersibility during the preparation and coating of the negative electrode slurry due to the small size of the silicon particles, which reduces the lifespan and capacity retention of the secondary battery. Conversely, if the size of the silicon particles is too large, there is a problem of degradation due to mechanical stress during the charging and discharging process of the secondary battery.

[0013] Therefore, it is necessary to prepare silicon particles with a size of micrometers. However, it is difficult to prepare silicon particles with a size of micrometers using existing methods for preparing silicon nanoparticles, and there are limitations in controlling sphericity and grain size.

[0014] Furthermore, existing methods for preparing silicon nanoparticles, such as laser methods and plasma methods, are limited in terms of large-scale production due to their high costs. Therefore, it is expected that technologies for preparing silicon microparticles using laser methods and plasma methods will ultimately be difficult to mass-produce.

[0015] As mentioned above, considering the dispersibility of silicon particles and the activity resulting from the specific surface area of ​​silicon particles, the demand for silicon microparticles is increasing in many fields. Therefore, it is necessary to develop technologies that can directly and effectively prepare micron-sized silicon particles. Furthermore, it is still necessary to develop preparation methods that can ensure the grain size and sphericity of silicon microparticles, as well as preparation apparatus for implementing such methods. Summary of the Invention

[0016] Technical issues The purpose of this invention is to provide silicon microparticles with a grain size of less than 40 nm, high sphericity, and a particle size of several hundred nm to several μm.

[0017] Furthermore, the purpose of this invention is to provide a method for preparing silicon microparticles and an apparatus for implementing the method, which is economical and efficient in preparing silicon microparticles with a grain size of less than 40 nm, high sphericity, and a particle size of several hundred nm to several μm, without the need for additional processes such as crushing and sieving, and is therefore suitable for mass production.

[0018] The objectives of this invention are not limited to those described above. Other objectives and advantages of this invention not mentioned can be understood through the following description and will become more apparent through embodiments of the invention. Furthermore, it is obvious that the objectives and advantages of this invention can be achieved through the means and combinations thereof pointed out in the claims.

[0019] Technical solution To achieve the aforementioned objective, according to a first embodiment of the present invention, A method for preparing silicon microparticles can be provided, comprising: step (S1), adding a silicon source gas mixture containing two or more silicon source gases with different decomposition temperatures and hydrogen gas into a reactor; and step (S2), in the reactor, the silicon source gas mixture decomposes to generate silicon microparticles, wherein the average grain size of the generated silicon microparticles is less than 40 nm and the average particle size (D) is less than 40 nm. 50 The size ranges from 100 nm to 10 μm, and the sphericity is above 80%.

[0020] The silicon source gas mixture can be a mixture of two or more silicon source gases selected from those represented by chemical formula 1 or chemical formula 2 below.

[0021] Chemical formula 1: SiH x Cl 4-x (x is an integer from 0 to 4) Chemical formula 2: Si2H y Cl 6-y (y is an integer from 0 to 6) The silicon source gas represented by chemical formula 1 or chemical formula 2 can be selected from silane (SiH4) gas, dichlorosilane (SiH2Cl2) gas, trichlorosilane (SiHCl3) gas, tetrachlorosilane (SiCl4) gas, hexachlorosilane (Si2Cl6) gas, and silane (Si2H6) gas.

[0022] The silicon source gas mixture includes a first silicon source gas and a second silicon source gas, wherein the decomposition temperature of the first silicon source gas is lower than that of the second silicon source gas.

[0023] The decomposition temperature of the first silicon source gas is 350°C to 600°C, and the decomposition temperature of the second silicon source gas can be 600°C to 1000°C.

[0024] The first silicon source gas and the second silicon source gas can be added in a molar ratio of 1:0.2 to 1:6.

[0025] The silicon source gas mixture and hydrogen gas can be added in a molar ratio of 1:0.5 to 1:10.

[0026] The temperature of the reactor can be between 700°C and 1000°C, and the temperature gradient can be such that the temperature at the top of the reactor is higher than the temperature at the bottom of the reactor.

[0027] In the reactor, the generation of silicon seed crystals and the growth of silicon particles on the generated silicon seed crystals can occur simultaneously.

[0028] In step (S2), the reaction time of the silicon source gas mixture in the reactor used to prepare silicon microparticles can be from 5 minutes to 3 hours.

[0029] In the method for preparing silicon microparticles, a carrier gas may be further added inside the reactor.

[0030] According to a second embodiment of the present invention, an apparatus for preparing silicon microparticles can be provided, comprising: a raw material gas injection unit; a raw material gas mixing unit; a pyrolysis reactor; a heating unit surrounding the reactor; and a gas discharge unit, wherein a turbulent region formed at the top of the pyrolysis reactor and a laminar region formed at the bottom of the pyrolysis reactor coexist.

[0031] The interior of the pyrolysis reactor includes an internal structure that forms turbulent and laminar flow regions. The material of the internal structure is heat-resistant to 700°C to 1000°C and may include one or more selected from graphite, quartz, and ceramic.

[0032] The apparatus for preparing silicon microparticles can be an apparatus for implementing the method for preparing silicon microparticles according to the first embodiment.

[0033] The temperature of the pyrolysis reactor can be between 700°C and 1000°C, and the temperature gradient can be such that the temperature at the top of the pyrolysis reactor is higher than the temperature at the bottom of the reactor.

[0034] In the volume of the pyrolysis reactor, the ratio of the volume of the turbulent region to the volume of the laminar region can be from 1:9 to 9:1.

[0035] The silicon microparticles can have a grain size of less than 40 nm and an average particle size (D). 50 The size can range from 100 nm to 10 μm, and the sphericity can be above 80%.

[0036] According to a third embodiment of the present invention, a silicon microparticle can be provided, which is prepared by the silicon microparticle preparation method according to the first embodiment of the present invention.

[0037] The average grain size of the silicon microparticles can be below 40 nm, and the average particle size (D) can be below 40 nm. 50 The size can range from 100 nm to 10 μm, and the sphericity can be above 80%.

[0038] Invention Effects According to the present invention, silicon microparticles with a grain size of less than 40 nm and a sphericity of more than 80% can be provided.

[0039] The method for preparing silicon microparticles of the present invention eliminates the need for further processing such as crushing and sieving after preparing polycrystalline silicon particles, and can directly control the grain size and sphericity to prepare silicon microparticles.

[0040] The method for preparing silicon microparticles of the present invention does not require the addition of silicon rods or silicon seed crystals. It simultaneously achieves the generation of silicon seed crystals and the growth of silicon particles in a single reactor, thereby directly preparing silicon microparticles. Therefore, it has the advantages of being economical, efficient, and suitable for mass production.

[0041] In addition to the effects described above, the specific effects of the present invention will be described in detail below in conjunction with specific embodiments of the invention. Attached Figure Description

[0042] Figure 1 The flowchart below briefly illustrates a method for preparing silicon microparticles according to an example of the present invention.

[0043] Figure 2 A cross-sectional view of an apparatus for preparing silicon microparticles according to an example of the present invention is shown for brevity.

[0044] Figure 3 A pyrolysis reactor of an apparatus for preparing silicon microparticles according to an example of the present invention is briefly shown.

[0045] Figure 4 This is a visualization simulation of the gas residence time distribution inside the pyrolysis reactor of a silicon microparticle preparation apparatus according to an example of the present invention.

[0046] Figure 5 This is a visualization simulation of the gas velocity distribution inside the pyrolysis reactor of a silicon microparticle preparation apparatus according to an example of the present invention.

[0047] Figure 6 The visualization results show the temperature gradient at the top and bottom of the reactor adjusted according to Embodiment 1 of the present invention.

[0048] Figure 7SEM images of the microparticles prepared according to Example 1 of the present invention are shown.

[0049] Figure 8 SEM images of the microparticles prepared according to Example 2 of the present invention are shown.

[0050] Figure 9 SEM images of the microparticles prepared according to Example 3 of the present invention are shown.

[0051] Figure 10 SEM images of the microparticles prepared according to Example 4 of the present invention are shown.

[0052] Figure 11 SEM images of the microparticles prepared according to Example 5 of the present invention are shown. Detailed Implementation

[0053] The advantages, features, and implementation methods of the present invention will become clear from the detailed embodiments described below with reference to the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but can be implemented in various different forms. These embodiments are provided only to ensure the completeness of the disclosure of the present invention and to fully inform those skilled in the art of the scope of the invention. The invention is defined only by the scope of the claims. Throughout this specification, the same reference numerals denote the same structural elements.

[0054] For any content not described in this specification, if it can be fully derived by a person skilled in the art through technical deduction, its description shall be omitted.

[0055] In this specification, although terms such as "first," "second," etc., are used to describe various structural elements, these structural elements are not limited to these terms. These terms are used only to distinguish one structural element from other structural elements, and unless otherwise specifically stated to the contrary, a first structural element may also be a second structural element.

[0056] In this specification, unless otherwise stated otherwise, the structural elements may be singular or plural.

[0057] In this specification, when any structure is provided on the "upper (or lower) part" or "upper (or lower) part" of a structural element, it can not only indicate that the arbitrary structure is in contact with the upper (or lower) part of the structural element, but also indicate that other structures can be inserted between the structural element and any structure provided on (or below) the structural element.

[0058] In this specification, when the relationship between a structural element and another structural element is described as "connection", "combination" or "linkage", it should be understood that the structural elements can be directly connected or linked to each other, or that each structural element "intervenes" in other structures, or that each structural element can also be "connected", "combined" or "linked" through other structural elements.

[0059] Unless the context clearly implies otherwise, the singular form used in this specification includes the plural form. In this application, terms such as “containing,” “comprising,” and “constituting” should not be construed as necessarily including all structural elements or steps described in the specification, but should be construed as excluding some structural elements or steps, or including additional structural elements or steps.

[0060] In this specification, when “A and / or B” is mentioned, it means A, B or A and B unless otherwise stated to the contrary. When “C to D or C to D” is mentioned, it means C and above and D and below unless otherwise stated to the contrary.

[0061] In this specification, when the ratio of the first component to the second component is described as a:b to c:d, it means "first component:second component = a:b" to "first component:second component = c:d".

[0062] In this specification, the "average grain size" is determined using XRD (Panalytical, Empyrean XRD).

[0063] In this specification, "average particle size (D)" 50 The particle size distribution was determined using a laser diffraction particle size analyzer (LS13 320, Beckman Coulter) via laser diffraction.

[0064] In this specification, "sphericity" is the value obtained by setting the horizontal and vertical axes at 90° to each other at the center of the silicon particle, and converting the ratio of the length of the vertical axis to the length of the horizontal axis within the particle into a percentage.

[0065] In this specification, microparticles refer to particles with an average particle size (D). 50 The particles are 100 nm to 10 μm in size and may include an error range.

[0066] In this specification, unless otherwise stated otherwise, “reactor” should be understood to mean “pyrolysis reactor”.

[0067] The present invention will now be described in detail.

[0068] Preparation method of silicon microparticles refer to Figure 1 The method for preparing silicon microparticles of the present invention will be described.

[0069] The method for preparing silicon microparticles of the present invention is used to prepare silicon microparticles with an average grain size of less than 40 nm and an average particle size (D). 50 Silicon microparticles ranging from 100 nm to 10 μm with a sphericity of 80% or higher, including: Step (S1): A mixture of silicon source gases containing two or more silicon source gases with different decomposition temperatures and hydrogen gas are added to the reactor. In step (S2), the silicon source gas mixture decomposes in the reactor to generate silicon microparticles.

[0070] The silicon source gas mixture is the gas used as a raw material in the preparation of silicon particles. According to an example of the present invention, it can be a mixture of two or more silicon source gases selected from those represented by chemical formula 1 or chemical formula 2.

[0071] Chemical formula 1: SiH x Cl 4-x (x is an integer from 0 to 4) Chemical formula 2: Si2H y Cl 6-y (y is an integer from 0 to 6) According to an example of the present invention, the silicon source gas represented by the chemical formula 1 or chemical formula 2 may be selected from silane (SiH4) gas, dichlorosilane (SiH2Cl2) gas, trichlorosilane (SiHCl3) gas, tetrachlorosilane (SiCl4) gas, hexachlorosilane (Si2Cl6) gas, and silane (Si2H6) gas, but is not limited thereto.

[0072] The silicon source gas mixture of the present invention comprises a first silicon source gas and a second silicon source gas, wherein the first silicon source gas and the second silicon source gas may be selected from the silicon source gas represented by the chemical formula 1 or chemical formula 2.

[0073] According to one embodiment of the present invention, the decomposition temperature of the first silicon source gas is lower than that of the second silicon source gas. The decomposition temperature of the first silicon source gas can be between 350°C and 600°C, and the decomposition temperature of the second silicon source gas can be between 600°C and 1000°C. In this case, the decomposition temperatures of the first and second silicon source gases are different. As a specific example, the first silicon source gas can be dichlorosilane (SiH2Cl2) gas, and the second silicon source gas can be trichlorosilane (SiHCl3) gas.

[0074] As described in this invention, in the method for preparing silicon microparticles using a mixture of silicon source gases with different decomposition temperatures, the silicon source gas with the lower decomposition temperature first forms silicon seed particles, and simultaneously or continuously, the formed silicon seed particles are grown, thereby preparing silicon microparticles. Specifically, the decomposition temperature of the first silicon source gas is lower than that of the second silicon source gas, therefore the first silicon source gas undergoes pyrolysis first, thereby forming silicon seed particles within the reactor. Simultaneously, the second silicon source gas undergoes pyrolysis and deposits on the formed silicon seed particles, thus allowing silicon microparticles to be prepared in a single reactor.

[0075] As described above, the method for preparing silicon microparticles of the present invention does not require the addition of silicon rods or silicon seed crystals, nor does it require contact with the reactor during the production process. Therefore, it has high purity due to the low content of metal impurities, and can effectively prepare micron-sized silicon particles without additional crushing or particle size sieving processes.

[0076] The first and second silicon source gases added to the reactor can be added at a molar ratio of 1:0.2 to 1:6, or for example, at a molar ratio of 1:0.5 to 1:4. The addition ratio of the first and second silicon source gases can be specifically set to adjust the formation rate and growth of the silicon seed crystal particles. For example, if the proportion of the first silicon source gas is less than the specified range, silicon seed crystal particles may not form successfully; if the proportion of the first silicon source gas is greater than the specified range, only a large number of insufficiently grown small particles may form, potentially resulting in the inability to form silicon particles of the target size.

[0077] In the method for preparing silicon microparticles of the present invention, hydrogen (H2) gas, which serves as a growth reaction gas, is added together with the silicon source gas mixture. The added hydrogen gas undergoes a reduction reaction with the silicon source gas mixture, thereby enabling the growth of silicon microparticles.

[0078] The silicon source gas mixture and hydrogen gas added to the reactor can be added at a molar ratio of, for example, 1:0.5 to 1:10, 1:1 to 1:5, or 1:2 to 1:3. If the proportion of hydrogen gas added is less than the range described above, the growth reaction may not proceed smoothly. If the proportion of hydrogen gas added is greater than the range described above, the amount of silicon source gas mixture will be relatively reduced, leading to limitations in the production of silicon particles at the target yield.

[0079] The method for preparing silicon microparticles according to the present invention includes step (S2), in which a silicon source gas mixture decomposes and generates silicon microparticles in the pyrolysis reactor. In one reactor, the silicon source gas mixture is grown simultaneously with the decomposition and generation of silicon seed crystals, thereby enabling the preparation of silicon microparticles.

[0080] Specifically, in the silicon source gas mixture added to the reactor, the first silicon source gas, which has a lower decomposition temperature, first undergoes pyrolysis to form silicon seed crystal particles, while the second silicon source gas undergoes pyrolysis and deposits on the formed silicon seed crystal particles, thereby enabling the preparation of silicon microparticles using chemical vapor synthesis (CVS).

[0081] Therefore, silicon microparticles can be prepared at a faster speed without additional crushing and sieving processes, thus enabling the preparation of high-purity silicon microparticles.

[0082] In this invention, when the silicon source gas mixture decomposes and prepares silicon microparticles, the internal temperature of the reactor can be 700°C to 1000°C, and the temperature gradient can be formed such that the temperature at the top of the reactor is higher than the temperature at the bottom of the reactor. Matters concerning the reactor will be described in detail in the following section on the preparation apparatus for silicon microparticles.

[0083] The internal pressure of the reactor can be from 1 bar to 10 bar. In the reaction step, from the perspective of adjusting the pyrolysis rate of the silicon source gas mixture and the size of the silicon particles, and improving the reaction yield, the reactor having a temperature and pressure within this range is likely preferred. Since the internal temperature of the reactor needs to initiate pyrolysis, it is preferably the same as or slightly higher than the pyrolysis temperature of the second silicon source gas with a higher decomposition temperature, while the pressure can be adjusted according to process conditions. The reactor can be heated to the specified temperature using a heating device.

[0084] According to one embodiment of the present invention, the time for preparing silicon microparticles in the reactor using the silicon source gas mixture can be approximately 5 minutes to 3 hours, but this can be adjusted according to the size of the reactor, the amount of raw material gas added, and the target yield. However, if the reaction time of the silicon source gas mixture is too short, there may be insufficient time for silicon seed crystal formation and particle growth. If the reaction time of the silicon source gas mixture is too long, the size of the silicon particles may exceed the target range, and the silicon particles may overgrow, resulting in excessively large grain sizes.

[0085] According to an embodiment of the present invention, the method for preparing silicon microparticles may further include a step of recovering the prepared silicon microparticles, and a cooling step may be included before recovery.

[0086] According to one embodiment of the invention, a carrier gas can be further added to the reactor, for example, the carrier gas can be argon (Ar) gas or nitrogen (N2) gas. The carrier gas can be added to maintain the flow rate of the gas injected from the bottom of the reactor. The reaction apparatus of the present invention has a structure where gas flows in from the bottom; therefore, a carrier gas can be used to easily adjust the gas flow rate.

[0087] According to another embodiment of the present invention, silicon microparticles prepared according to the method for preparing said silicon microparticles are provided. The silicon microparticles prepared in this way can be used as silicon nitride raw materials, materials for solar cells, negative electrode materials for secondary batteries, etc.

[0088] Specifically, the average particle size (D) of the silicon particles prepared according to the present invention 50 For example, the particle size distribution can be from 100 nm to 10 μm, from 1 μm to 5 μm, or from 1.5 μm to 3 μm. Therefore, no separate pulverization process is required, and since there is no pulverization process, no fine powder is generated, and no sieving process is needed, resulting in a significantly low content of metal impurities. When the silicon microparticles of the present invention, having a particle size distribution within the aforementioned range, are used as a negative electrode material for secondary batteries, they can help improve the lifespan and capacity retention of the secondary battery.

[0089] Furthermore, the silicon microparticles prepared in this invention can have smaller grains than previously possible. Larger grain sizes of silicon particles reduce the lifespan of secondary batteries when used as a negative electrode material; conventionally used silicon particles have a grain size of approximately 100 nm. Therefore, according to an example of this invention, the average grain size of the silicon microparticles can be 40 nm or less, and by adjusting the process conditions, silicon microparticles with an average grain size of, for example, 30 nm or less, or even 25 nm or less, can be prepared. As described above, smaller grain sizes reduce particle damage caused by volume changes during the charging and discharging process of the secondary battery, thereby contributing to improved battery lifespan.

[0090] Furthermore, the silicon microparticles prepared in this invention differ from those obtained through conventional pulverization. Because they do not undergo a pulverization process, they exhibit very high sphericity. When non-spherical silicon particles are used as the negative electrode material in a secondary battery, there is a decrease in dispersibility and a higher probability of side reactions occurring during the charging and discharging process, ultimately leading to a decline in the battery's performance. Therefore, when the spherical silicon microparticles of this invention are used as the negative electrode material in a secondary battery, they can help improve the battery's performance. According to an example of this invention, the sphericity of the silicon microparticles can be, for example, 80% or more, 90% or more, 95% or more, or 99% or more.

[0091] apparatus for preparing silicon microparticles refer to Figure 2 An apparatus for preparing silicon microparticles for implementing the method for preparing silicon microparticles of the present invention can be provided.

[0092] The silicon microparticle preparation apparatus 100 includes: a raw material gas injection unit 10; a raw material gas mixing device 20; a pyrolysis reactor 30; a heating unit 40 surrounding the reactor; and a gas discharge unit 50. The pyrolysis reactor 30 is characterized in that it includes an internal structure 60, thereby simultaneously forming a turbulent flow region and a laminar flow region during the reaction.

[0093] The pyrolysis reactor 30 can be used without restriction, as long as it is a reactor capable of chemical vapor phase synthesis (CVS).

[0094] The pyrolysis reactor 30 can be the reactor used in the method for preparing silicon microparticles of the present invention.

[0095] For example, the pyrolysis reactor 30 can be a chemical vapor deposition reactor, a chemical vapor condensation reactor, or a fluidized-bed reactor, preferably a chemical vapor deposition reactor.

[0096] The internal structure 60 is an open structure at both the top and bottom. Depending on the structure of the pyrolysis reactor 30, it can be a cylindrical structure, a cubic structure, etc., and can have the same shape as the pyrolysis reactor 30, but is not necessarily limited to this.

[0097] The heating section 40 surrounding the pyrolysis reactor 30 is not particularly limited, as long as it is a heating section applicable in this technical field, but it is required to be able to heat to 700°C to 1000°C, which is the temperature required by the present invention. For example, it can be operated by inserting a hot wire into the wall of the pyrolysis reactor 30 and applying a power source for heating, or by equipping a tubular furnace formed around the pyrolysis reactor 30 for heating.

[0098] Furthermore, as described below, since the temperatures of the bottom 30a and the top 30b of the pyrolysis reactor 30 are different, the heating section 40 is preferably designed so that the temperatures of the bottom 30a and the top 30b can be adjusted to be different.

[0099] Figure 2 Not shown, but may include bag filters for collecting the final silicon particles, various pressure and temperature controllers, valves, etc.

[0100] refer to Figure 3 To explain, reaction gases are supplied to the raw material gas injection unit 10, and the supplied reaction gases (raw material gases) are mixed in the raw material gas mixing device 20 and injected into the pyrolysis reactor 30 through the internal structure 60.

[0101] Figure 3 The arrow marked "IN" indicates the injection direction of the feed gas from the feed gas injection section 10 into the internal structure 60 (integrated with the pyrolysis reactor 30). The feed gas injected through the internal structure 60 diffuses through the top of the internal structure 60 into the pyrolysis reactor 30.

[0102] Figure 3 The arrow marked "OUT" indicates the direction in which gas is discharged from the gas discharge section 50 after the reaction in the pyrolysis reactor 30, which includes the internal structure 60.

[0103] Not specifically shown in the accompanying drawings, but according to one embodiment of the present invention, it can also be designed as follows: Figure 3 The injection direction and the exhaust direction of the feed gas are opposite. Based on... Figure 3 To explain, the reactor can be designed to supply raw material gas from the gas discharge section 50 and discharge gas from the raw material gas injection section 10. This can be achieved by altering the gas flow inside and outside the reactor.

[0104] According to a preferred embodiment of the present invention, such as Figure 3 As shown, one raw material gas injection section 10 can be provided at the center of the internal structure 60, and two gas discharge sections 50 can be provided on the outside of the pyrolysis reactor 30 not occupied by the internal structure 60.

[0105] A turbulent region is formed at the top of the pyrolysis reactor 30, and a laminar region is formed at the bottom of the pyrolysis reactor 30.

[0106] Furthermore, the pyrolysis reactor 30 is characterized by adjusting the temperatures at the top and bottom to be different.

[0107] Specifically, the area from the raw material gas injection section 10 to about 1 / 3 of the height of the pyrolysis reactor 30 is divided into the bottom 30a, and the area from the top of the bottom 30a to the top of the reactor is divided into the top 30b. The temperature of the top 30b is set to be about 50 to 100°C higher than that of the bottom 30a.

[0108] According to one embodiment of the present invention, the temperature of the bottom 30a of the pyrolysis reactor can be approximately 700°C to 1000°C, or 800°C to 900°C. Therefore, the temperature of the top 30b of the pyrolysis reactor can be heated to a temperature approximately 50°C to 100°C higher.

[0109] As a result, in the bottom 30a of the pyrolysis reactor where the temperature is set to be relatively low, the main reaction is the generation of silicon source gas to silicon seed crystals at a relatively low pyrolysis temperature.

[0110] Furthermore, in the top 30b of the pyrolysis reactor, where the temperature is set relatively high, a silicon source with a relatively high pyrolysis temperature grows particles on the silicon seed crystal generated at the bottom 30a through a chemical deposition reaction, thereby forming micron-sized silicon particles.

[0111] Importantly, as detailed below, a laminar flow region is mainly formed at the bottom 30a of the pyrolysis reactor, and a turbulent flow region is mainly formed at the top 30b. Thus, as this invention relates to, the bottom 30a can mainly carry out the silicon seed crystal generation reaction, and the top 30b can mainly carry out the chemical deposition reaction, thereby exhibiting high efficiency and controllability in the preparation of silicon microparticles.

[0112] refer to Figure 4 and Figure 5 The turbulent and laminar flow regions are described in detail.

[0113] Figure 4 To visualize the simulation of the gas flow trajectory at the top of the reactor, the data is differentiated using a color spectrum based on the gas residence time (Particle RT).

[0114] Blue indicates a residence time of 0; therefore, the closer to blue, the shorter the residence time of the gas particles. A short residence time means that the gas particles are rapidly discharged from the reactor due to linear flow, indicating good laminar flow development.

[0115] Conversely, a redder color indicates a longer residence time. A longer residence time for gas particles means that the reactant gases injected from the bottom of the reactor are in a mixed state at the top, thus indicating good turbulence development.

[0116] from Figure 4 a to Figure 4 d. The internal structure 60 has the same cross-sectional diameter, but its height gradually decreases relative to the height of the pyrolysis reactor 30. That is, the proportion of the inactive turbulent region at the top of the reactor can be adjusted according to the height of the internal structure.

[0117] Right now, Figure 4The height of the internal structure 60 is shown as a factor for adjusting the volume of the turbulent and laminar regions formed according to the residence time of the gas particles. The height of the internal structure 60 is designed to be different from the height of the pyrolysis reactor 30, thereby adjusting the volume of the inactive turbulent region at the top of the reactor.

[0118] The laminar flow region is conducive to the formation of silicon seed crystals, while the turbulent flow region is conducive to particle growth. Therefore, by adjusting factors such as the height of the internal structure 60, the optimal combination of the volumes of the laminar flow region and the turbulent flow region as described above can be obtained.

[0119] Figure 5 This is a simulation diagram that visualizes the flow velocity (vector value) of the gas at the top of the reactor using the direction and length of arrows, and distinguishes the flow velocity using different color spectra. The closer to blue, the slower the flow velocity; the closer to red, the faster the flow velocity.

[0120] Figure 5 The explanation is the same as above. Figure 4 The explanation is the same. That is, the more or shorter the blue arrows, the laminar flow region, where the gas particles have a short residence time. The more or longer the arrows that are close to red, the turbulent flow region, where the flow is inactive, the gas particles have a long residence time, and they are in a state of high mixing.

[0121] Figure 5 a to Figure 5 d is the same as Figure 4 a to Figure 4 Simulation results for the same reactor (d) can also be confirmed through flow velocity analysis, indicating that the occupancy of the inactive turbulent region at the top of the reactor can be adjusted according to the height of the internal structure. As mentioned above, the volume and residence time of the turbulent region formed at the top 30b of the pyrolysis reactor can be adjusted by modifying the design of the internal structure 60, thereby controlling the size and growth of the final silicon particles to be prepared.

[0122] According to an embodiment of the present invention, in the volume of the pyrolysis reactor, the volume ratio of the turbulent region to the laminar region can be, for example, 1:9 to 9:1, 2:8 to 8:2, 3:7 to 7:3, 4:6 to 6:4, or 5:5.

[0123] According to one embodiment of the present invention, the material of the internal structure 60 can be heat-resistant to 700°C to 1000°C, and may include one or more selected from graphite, quartz, and ceramic. By adjusting the ratio of the diameter of the pyrolysis reactor 30 to the diameter of the internal structure 60, and the ratio of the reactor height to the height of the internal structure, the turbulent and laminar flow regions can be designed with a desired volume ratio, and the method is not particularly limited.

[0124] Embodiments of the present invention The present invention will now be described in more detail through embodiments. However, the following embodiments are merely examples of the present invention, and the scope of the present invention is not limited to the following embodiments.

[0125] Example 1 The reactor conditions were set to pressurize to 0.5 bar, and the bottom temperature of the reactor was set to 800°C and the top temperature of the reactor was set to 900°C for heating.

[0126] Then, silane (SiH4, decomposition temperature approximately 600°C) as the first silicon source gas, trichlorosilane (SiHCl3, decomposition temperature approximately 800°C) as the second silicon source gas, and hydrogen gas are mixed in a molar ratio of 0.5:1:3. All of the first silicon source gas, the second silicon source gas, and hydrogen gas are then added to the reactor. The amount of trichlorosilane added is 2056 sccm.

[0127] The mixture is then reacted in a reactor for approximately 60 minutes to carry out a pyrolysis reaction, thereby preparing micron-sized silicon particles. The prepared silicon particles are then cooled and recovered.

[0128] Example 2 The pressurization and heating were performed in the same manner as in Example 1, but the reactor temperature conditions were changed to those shown in Table 1 below. Then, silane (SiH4, decomposition temperature approximately 600°C) as the first silicon source gas, trichlorosilane (SiHCl3, decomposition temperature approximately 800°C) as the second silicon source gas, and hydrogen gas were mixed in a molar ratio of 0.5:1:1.6, and all of the first silicon source gas, second silicon source gas, and hydrogen gas were added to the reactor. The amount of trichlorosilane added was 4134 sccm.

[0129] The mixture is then reacted in a reactor for approximately 45 minutes to carry out a pyrolysis reaction, thereby preparing micron-sized silicon particles. The prepared silicon particles are then cooled and recovered.

[0130] Example 3 The pressurization and heating were performed in the same manner as in Example 1, but the reactor temperature conditions were changed to those shown in Table 1 below. Then, silane (SiH4, decomposition temperature approximately 600°C) as the first silicon source gas, trichlorosilane (SiHCl3, decomposition temperature approximately 800°C) as the second silicon source gas, and hydrogen gas were mixed in a molar ratio of 0.5:1:3, and all of the first silicon source gas, second silicon source gas, and hydrogen gas were added to the reactor. The amount of trichlorosilane added was 4961 sccm.

[0131] The mixture is then reacted in a reactor for approximately 35 minutes to carry out a pyrolysis reaction, thereby preparing micron-sized silicon particles. The prepared silicon particles are then cooled and recovered.

[0132] Example 4 The pressurization and heating were performed in the same manner as in Example 1, but the reactor temperature conditions were changed to those shown in Table 1 below. Then, silane (SiH4, decomposition temperature approximately 600°C) as the first silicon source gas, trichlorosilane (SiHCl3, decomposition temperature approximately 800°C) as the second silicon source gas, and hydrogen gas were mixed in a molar ratio of 0.5:1:3, and all of the first silicon source gas, second silicon source gas, and hydrogen gas were added to the reactor. The amount of trichlorosilane added was 2756 sccm.

[0133] The mixture is then reacted in a reactor for approximately 60 minutes to carry out a pyrolysis reaction, thereby preparing micron-sized silicon particles. The prepared silicon particles are then cooled and recovered.

[0134] Example 5 The pressurization and heating were performed in the same manner as in Example 1, but the reactor temperature conditions were changed to those shown in Table 1 below. Then, silane (SiH4, decomposition temperature approximately 600°C) as the first silicon source gas, trichlorosilane (SiHCl3, decomposition temperature approximately 800°C) as the second silicon source gas, and hydrogen gas were mixed in a molar ratio of 0.5:1:3, and all of the first silicon source gas, second silicon source gas, and hydrogen gas were added to the reactor. The amount of trichlorosilane added was 3859 sccm.

[0135] The mixture is then reacted in a reactor for approximately 60 minutes to carry out a pyrolysis reaction, thereby preparing micron-sized silicon particles. The prepared silicon particles are then cooled and recovered.

[0136] Experimental Example SEM images of the silicon particles prepared in Examples 1 to 5 are shown respectively. Figures 7 to 11 middle.

[0137] D was determined using a laser diffraction particle size analyzer (LS13320, Beckman Coulter). 50 .

[0138] The average grain size of silicon particles was determined by XRD (Panalytical, Empyrean XRD) analysis using X-ray diffraction.

[0139] Through the Figures 7 to 11 The SEM images were analyzed, 20 particles were randomly selected, the sphericity was measured and the average value was calculated, which was then determined as the sphericity value.

[0140] The process conditions of Examples 1 to 5 and the measured D 50 The average grain size and sphericity are shown in Table 1 below.

[0141] Table 1

[0142] The meanings of the terms used in Table 1 are as follows.

[0143] "TCS" refers to trichlorosilane (SiHCl3).

[0144] "sccm" refers to standard cubic centimeter per minute (based on 0°C and 1 atm), which is a unit of flow rate per unit time.

[0145] "Retention time" refers to the time required for the reactant gas to be released from the reactor after it has been injected into the reactor.

[0146] "Process time" refers to the time required until the deposition reaction is complete.

[0147] As shown in Table 1, the silicon particles prepared according to the present invention can achieve the indicated micron-level particle size (D). 50 The material exhibits excellent sphericity and high grain size. Furthermore, the preparation method of this invention can be efficiently prepared via chemical vapor phase synthesis (CVS) without additional pulverization processes, thus demonstrating excellent processability.

[0148] The embodiments and accompanying drawings described above have been presented in more detail with reference to the present specification. However, this specification is not necessarily limited to these embodiments and drawings, and various modifications can be made without departing from the technical spirit of this specification. Therefore, the embodiments disclosed in this specification are not intended to limit the technical spirit of the invention but are for illustration, and the scope of the technical spirit of the invention is not limited to these embodiments. Therefore, the embodiments described above should be understood as exemplary and not restrictive in all respects. The scope of protection of this specification and the invention should be interpreted in accordance with the claims, and all technical ideas within the same scope should be interpreted as being included within the scope of protection of the claims of this specification and the invention.

Claims

1. A method for preparing silicon microparticles, characterized in that, include: Step (S1): A mixture of silicon source gases containing two or more silicon source gases with different decomposition temperatures and hydrogen gas are added to the reactor. as well as In step (S2), the silicon source gas mixture decomposes in the reactor to generate silicon microparticles. The generated silicon microparticles have an average grain size of less than 40 nm and an average particle size D. 50 The size ranges from 100 nm to 10 μm, and the sphericity is over 80%.

2. The method for preparing silicon microparticles according to claim 1, characterized in that, The silicon source gas mixture is a mixture of two or more silicon source gases selected from those represented by chemical formula 1 or chemical formula 2 below: Chemical formula 1: SiH x Cl 4-x Where x is an integer from 0 to 4, Chemical formula 2: Si2H y Cl 6-y , where y is an integer from 0 to 6.

3. The method for preparing silicon microparticles according to claim 2, characterized in that, The silicon source gas represented by chemical formula 1 or chemical formula 2 is selected from silane gas, dichlorosilane gas, trichlorosilane gas, tetrachlorosilane gas, hexachlorosilane gas, and silane gas.

4. The method for preparing silicon microparticles according to claim 1, characterized in that, The silicon source gas mixture includes a first silicon source gas and a second silicon source gas, wherein the decomposition temperature of the first silicon source gas is lower than that of the second silicon source gas.

5. The method for preparing silicon microparticles according to claim 4, characterized in that, The decomposition temperature of the first silicon source gas is 350°C to 600°C. The decomposition temperature of the second silicon source gas is 600°C to 1000°C.

6. The method for preparing silicon microparticles according to claim 4, characterized in that, The first silicon source gas and the second silicon source gas are added in a molar ratio of 1:0.2 to 1:

6.

7. The method for preparing silicon microparticles according to claim 4, characterized in that, The silicon source gas mixture and hydrogen gas are added in a molar ratio of 1:0.5 to 1:

10.

8. The method for preparing silicon microparticles according to claim 1, characterized in that, The temperature of the reactor is 700℃ to 1000℃. A temperature gradient is formed such that the temperature at the top of the reactor is higher than the temperature at the bottom of the reactor.

9. The method for preparing silicon microparticles according to claim 1, characterized in that, In the reactor, the generation of silicon seed crystals and the growth of silicon particles on the generated silicon seed crystals occur simultaneously.

10. The method for preparing silicon microparticles according to claim 1, characterized in that, In step (S2), the reaction time of the silicon source gas mixture in the reactor used to prepare silicon microparticles is from 5 minutes to 3 hours.

11. The method for preparing silicon microparticles according to claim 1, characterized in that, Further carrier gas is added into the reactor.

12. An apparatus for preparing silicon microparticles, characterized in that, include: Raw material gas injection section; Raw material gas mixing device; Pyrolysis reactor; Heating section, surrounding the reactor; as well as Gas exhaust section, In the pyrolysis reactor, a turbulent region formed at the top of the pyrolysis reactor and a laminar region formed at the bottom of the pyrolysis reactor coexist.

13. The apparatus for preparing silicon microparticles according to claim 12, characterized in that, The pyrolysis reactor includes internal structures that form turbulent and laminar flow regions. The material of the internal structure is heat-resistant to 700°C to 1000°C, including one or more selected from graphite, quartz and ceramics.

14. The apparatus for preparing silicon microparticles according to claim 12, characterized in that, The temperature of the pyrolysis reactor is 700℃ to 1000℃. The temperature gradient is such that the temperature at the top of the pyrolysis reactor is higher than the temperature at the bottom of the pyrolysis reactor.

15. The apparatus for preparing silicon microparticles according to claim 12, characterized in that, In the volume of the pyrolysis reactor, the ratio of the volume of the turbulent region to the volume of the laminar region is 1:9 to 9:

1.

16. The apparatus for preparing silicon microparticles according to claim 12, characterized in that, The silicon microparticles have a grain size of less than 40 nm and an average particle size D. 50 The size ranges from 100 nm to 10 μm, and the sphericity is over 80%.

17. A silicon microparticle, characterized in that, Prepared by the method for preparing silicon microparticles according to any one of claims 1 to 11.

18. The silicon microparticles according to claim 17, characterized in that, The average grain size of the silicon microparticles is less than 40 nm, and the average grain diameter is D. 50 The size ranges from 100 nm to 10 μm, and the sphericity is over 80%.

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