Method for preparing silicon microparticles and silicon microparticles prepared by method

Abstract

The present invention provides a method for preparing silicon microparticles and silicon microparticles prepared by the method, the method comprising: a step of flowing a silane gas mixture into a reactor; and a step for preparing silicon microparticles by decomposing the silane gas mixture in the reactor, the silane gas mixture containing a first silane gas and a second silane gas, the decomposition temperature of the first silane gas being lower than the decomposition temperature of the second silane gas.

Description

Technical Field

[0001] The invention relates to a method for preparing silicon microparticles and silicon microparticles prepared by the method. Background Art

[0002] Silicon is used in a variety of industrial fields such as solar energy and semiconductors, and its demand is growing by leaps and bounds.

[0003] Silicon is typically produced by a Siemens method using a bell-jar type reactor and a fluidized bed reactor (FBR) method.

[0004] Among them, the Siemens method is a method of precipitating silicon from the surface of a silicon rod (rod) arranged in a bell-jar reactor. Since the surface area required for the precipitation of silicon is limited and the diameter of the silicon rod increased by the precipitation reaction is limited, a continuous process cannot be carried out. In addition, the power consumption per unit weight of silicon is large, and it has the limitation of low productivity.

[0005] Moreover, the FBR method is a method of growing seed particles by precipitating silicon from the surface of silicon seed particles heated at high temperature. The silicon prepared by this method is usually prepared to a size of more than a millimeter. Therefore, in order to obtain tiny silicon, an additional crushing process is required, and fine powder is produced during the crushing process. A sieving process is also required, which is complicated and increases time and cost, and therefore has the problem of inefficiency. Moreover, in the production process of growing seed particles in a fluidized bed reactor, there is a problem of increasing the impurity content during the contact between silicon and the inner wall of the reactor.

[0006] Therefore, in order to solve the above problems, it is necessary to develop a method for efficiently preparing and producing silicon microparticles having a controlled particle size while minimizing the impurity content.

[0007] Then, the present inventors confirmed that silicon microparticles can be prepared by simultaneously forming silicon seed particles and growing ions in one reactor without silicon rods or seed particles, thereby completing the present invention. Summary of the invention

[0008] Technical issues

[0009] An object of the present invention is to provide a method for efficiently and continuously preparing and producing silicon microparticles having a controlled particle size while minimizing the impurity content.

[0010] An object of the present invention is to provide an economical and efficient method for preparing silicon microparticles without requiring an additional pulverization process or screening process.

[0011] The purpose of the present invention is not limited to the purpose mentioned above, and other purposes and advantages of the present invention not mentioned can be understood through the following description, and will be more clearly understood through the embodiments of the present invention. Moreover, it is obvious that the purposes and advantages of the present invention can be achieved by the means and combinations thereof shown in the scope of the invention claims.

[0012] Technical Solution

[0013] In order to achieve the above-mentioned purpose, according to the present invention, a method for preparing silicon microparticles can be provided, comprising: a step of allowing a silane gas mixture to flow into a reactor; and a step of decomposing the silane gas mixture in the reactor to prepare silicon microparticles, wherein the silane gas mixture comprises a first silane gas and a second silane gas, and the decomposition temperature of the first silane gas is lower than the decomposition temperature of the second silane gas.

[0014] Furthermore, according to the present invention, silicon fine particles having a low impurity content produced by the method for producing silicon fine particles can be provided.

[0015] Effects of the Invention

[0016] The method for preparing silicon microparticles of the present invention can prepare silicon microparticles without silicon rods or silicon seed particles, thereby avoiding unnecessary contact and reducing the content of metal impurities without additional additional steps.

[0017] The method for preparing silicon microparticles of the present invention can realize the generation of silicon seed particles and the growth of ions in one reactor at the same time, and is therefore more economical and efficient.

[0018] The method for preparing silicon microparticles of the present invention does not require an additional pulverization process, does not generate fine powder, and does not require a sieving process, so silicon microparticles can be prepared more economically and efficiently.

[0019] The specific effects of the present invention will be described together with the above-mentioned effects in the following description of the specific embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a scanning electron microscope (SEM) image of silicon microparticles prepared according to Example 1 of the present invention. DETAILED DESCRIPTION

[0021] The following content will describe the aforementioned objects, features and advantages in detail with reference to the accompanying drawings, and a person skilled in the art of the present invention can easily implement the technical ideas of the present invention accordingly. In the process of describing the present invention, if it is determined that the specific description of the related known technology of the present invention will confuse the gist of the present invention, its detailed description will be omitted. Below, the preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the accompanying drawings, the same reference numerals indicate the same or similar structural elements.

[0022] In this specification, descriptions of unexplained parts that can be sufficiently technically inferred by a person skilled in the art to which the present invention belongs will be omitted.

[0023] Hereinafter, when referring to the "upper part (or lower part)" of a structural element or an arbitrary structure being arranged "above (or below)" a structural element, it not only indicates that the arbitrary structure is arranged in contact with the upper side (or lower side) of the structural element, but also may indicate that other structures may be interposed between the structural element and the arbitrary structure arranged above (or below) the structural element.

[0024] Furthermore, when it is recorded that a certain structural element is “connected”, “combined” or “joined” with other structural elements, it not only indicates that the structural elements can be directly connected or joined to each other, but should also be interpreted as a situation where other structural elements are “interposed” between the structural elements, or a situation where the structural elements can be “connected”, “combined” or “joined” through other structural elements.

[0025] In this specification, “<X” and “≤X” represent a case of being less than X and being less than X, respectively, and “>X” and “≥X” represent a case of being greater than X and being greater than X, respectively.

[0026] In various embodiments of the present specification, the terms "first", "second", "third" and the like are used to describe various structural elements, but these structural elements should not be limited by the terms. These terms are only used to distinguish a certain structural element from other structural elements.

[0027] The terms used in this specification are used to illustrate the embodiments, rather than to limit the present invention. In this specification, unless otherwise specified, the singular sentence also includes the plural form. The descriptions such as "comprising" and "containing" used in this specification do not exclude the existence of the structural element or the addition of one or more other structural elements.

[0028] Hereinafter, the method for producing silicon fine particles of the present invention will be described in detail.

[0029] A method for preparing silicon microparticles according to an embodiment of the present invention comprises: a step of allowing a silane gas mixture to flow into a reactor; and a step of decomposing the silane gas mixture in the reactor to prepare silicon microparticles, wherein the silane gas mixture comprises a first silane gas and a second silane gas, and the decomposition temperature of the first silane gas is lower than the decomposition temperature of the second silane gas.

[0030] Considering the activity caused by the dispersibility of silicon particles and the specific surface area of ​​silicon particles, the demand for silicon microparticles is increasing in many fields.

[0031] The fluidized bed reactor method is a method in which silicon seed particles are placed in a reactor and then silane gas is injected to grow the seed particles. Silicon particles of a size of millimeters or more are usually prepared. Therefore, in order to obtain tiny silicon, an additional crushing process is required, and fine powder is generated during the crushing process. A sieving process is also required, which is complicated and increases time and cost, and thus has the problem of inefficiency. In addition, there is a problem of increasing the impurity content during the contact between silicon and the inner wall of the reactor during the production process.

[0032] The method for preparing silicon microparticles does not use silicon rods or silicon seed particles, and does not require a process of contacting a reactor during production. Therefore, the content of metal impurities can be reduced even without an additional additional process.

[0033] Specifically, the method for preparing the silicon microparticles includes the step of flowing a silane gas mixture into a reactor. The silane gas mixture is a gas used as a raw material in the preparation of silicon particles, and can be a mixture of two or more silane gases selected from chemical formula 1 or chemical formula 2. For example, the silane gas mixture can be selected from two or more of the group consisting of monosilane (SiH4), chlorosilane (SiH3Cl), dichlorosilane (SiH2Cl2), trichlorosilane (SiHCl3), tetrachlorosilane (SiCl4), hexachlorodisilane (Si2Cl6), disilane (Si2H6) and combinations thereof.

[0034] Chemical formula 1: SiH x Cl 4-x (0≤x≤4, x is an integer).

[0035] Chemical formula 2: Si2H y Cl 6-y (0≤y≤6, y is an integer).

[0036] The method for preparing silicon microparticles can prepare silicon microparticles using the silane gas mixture containing the first silane gas and the second silane gas having different decomposition temperatures without using silicon seed particles. The first silane gas and the second silane gas can be selected from the silane gas represented by Chemical Formula 1 or Chemical Formula 2.

[0037] The decomposition temperature of the first silane gas is lower than that of the second silane gas, the first silane gas may be a silane gas having a decomposition temperature of 350° C. to 600° C., and the second silane gas may be a silane gas having a decomposition temperature of 600° C. to 1000° C. For example, the first silane gas may be dichlorosilane (SiH2Cl2), and the second silane gas may be trichlorosilane (SiHCl3).

[0038] The method for preparing silicon microparticles can form silicon seed particles and simultaneously grow particles by adjusting the decomposition rate using the silane gas mixture having different decomposition temperatures.

[0039] For example, the decomposition temperature of the first silane gas is lower than that of the second silane gas, and the first silane gas can be thermally decomposed to form seed particles in the reactor. At the same time, as the second silane gas is thermally decomposed, it is evaporated on the formed seed particles, so that it can be prepared in one reactor.

[0040] The first silane gas and the second silane gas flowing into the reactor can flow in simultaneously at a molar ratio of 1:30 to 1:2. Preferably, they can flow in simultaneously at a molar ratio of 1:20 to 1:2. Thus, the formation speed of the seed particles and the growth of the ions can be well adjusted. For example, if the proportion of the first silane gas is less than the range, the problem of not being able to smoothly form silicon seed particles will occur. If the proportion of the first silane gas is greater than the range, a large number of small-sized particles that are not fully grown will be formed, thereby causing a problem of not being able to form silicon particles of the target size.

[0041] The silane gas mixture may flow into the reactor together with hydrogen. The hydrogen may undergo a reduction reaction with the silane gas mixture to prepare silicon.

[0042] The hydrogen gas may flow into the reactor in an amount of 50 mol % to 90 mol % relative to the total amount of the hydrogen gas mixed with the silane gas.

[0043] The method for preparing silicon microparticles may include the step of decomposing the silane gas mixture in the reactor to prepare silicon microparticles.

[0044] In one of the reactors, the silane gas mixture is decomposed to generate silicon seed particles and the silicon seed particles are simultaneously grown to prepare silicon fine particles.

[0045] Specifically, in the silane gas mixture put into the reactor, the first silane gas with a lower decomposition temperature is thermally decomposed to form seed particles, and at the same time, the second silane gas is thermally decomposed and evaporated on the seed particles, so that silicon microparticles can be prepared by a homogeneous reaction using a chemical vapor synthesis (CVS) method. Accordingly, silicon microparticles can be prepared at a faster speed and can have smaller grains.

[0046] In this way, the generation of silicon seed particles and the growth of ions are simultaneously achieved in one reactor. Since no additional crushing process is required, no fine powder is generated, and no sieving process is required, silicon microparticles can be continuously prepared more economically and efficiently.

[0047] When preparing silicon microparticles by decomposing the silane gas mixture, the temperature inside the reactor can be 700° C. to 1000° C., and the pressure inside the reactor can be 1 bar to 10 bar. From the viewpoint of regulating the thermal decomposition rate of the silane gas mixture and the size of the silicon particles and improving the reaction yield, it can be said that the reactor in the reaction step preferably has a temperature and pressure within the above range. The reactor can be brought to the above temperature by a heating device.

[0048] Moreover, the silicon microparticles can be prepared by allowing the silane gas mixture to be retained in the reactor for 5 minutes to 60 minutes. The target silicon microparticles can be prepared more effectively by adjusting the retention time of the silane gas mixture to the range. For example, if the retention time of the silane gas mixture is less than the range, there will be a problem of insufficient particle formation and particle growth time. If the retention time of the silane gas mixture is greater than the range, the size of the silicon particles will exceed the target range, and the problem of excessive grain size will result due to excessive growth of silicon particles.

[0049] The method for preparing the silicon microparticles may further include a step of recovering the silicon microparticles, and may further include a cooling step before the recovery.

[0050] Another embodiment of the present invention provides silicon microparticles prepared according to the method for preparing silicon microparticles. The silicon microparticles prepared in this way can be used as silicon nitride raw materials, solar cell materials, lithium ion battery negative electrode materials, etc.

[0051] Specifically, according to the method for preparing silicon microparticles of the present invention, the silicon microparticles may have a diameter of 1 μm. <d 10 <4μm, 2μm <d 50 <7μm and 4μm <d 90 The particle size is less than 13 μm. Therefore, no additional crushing process is required. Moreover, since there is no crushing process, no fine powder is generated, and no sieving process is required.

[0052] Furthermore, the silicon microparticles having the particle size distribution in the above range are preferably used as raw materials for silicon nitride and battery negative electrode materials, etc. The size of the silicon microparticles can be measured by laser diffraction method using LS13320, Beckman Coulter.

[0053] The silicon microparticles may have a spherical particle shape.

[0054] While having a particle size within the range, the total metal impurity content of the silicon microparticles can be less than 2000 ppm. In this specification, "metal of metal impurities" refers to metal elements that affect the quality when silicon particles are used in secondary batteries, etc., and representatively, it can refer to 24 metal elements from aluminum (Al) to zinc (Zn) recorded in Table 2 in this specification, but is not limited thereto.

[0055] The silicon microparticles can be used to prepare powders using a silane gas mixture without silicon rods or silicon seed particles, and can better reduce the content of metal impurities without unnecessary contact.

[0056] If metal impurities remain in the silicon particles, side reactions caused by the metal impurities will occur, which will reduce the physical properties. Therefore, an additional process is required to remove the metal impurities contained in the silicon particles. On the contrary, the silicon particles prepared by the preparation method can contain metal impurities at a low level even without additional additional processes. Specifically, the silicon particles can contain the above-mentioned metal impurities at a content of less than 2000ppm. For example, the content can be less than 1000ppm or less than 500ppm.

[0057] The silicon microparticles may be polycrystalline silicon (polycrystalline silicon), and the average grain size may be less than 60nm. The silicon particles prepared by the preparation method may have grains less than 60nm while having the aforementioned micron-sized particles. Excellent effects can be shown in multiple fields accordingly. For example, the silicon microparticles may be used as negative electrode materials for lithium-ion batteries, in which case the capacity retention rate can be improved by reducing particle damage caused by volume changes during battery charging and discharging.

[0058] The present invention will be described in more detail below by way of examples. However, the following examples are only for illustrating the present invention, and the content of the present invention is not limited to the following examples.

[0059] Example 1

[0060] Argon (Ar) gas was introduced into the reactor to make the reactor have a pressure of 5 bar and a temperature of 900° C. Then, 67 mol % of hydrogen (H2) and a silane gas mixture of 3 mol % of dichlorosilane (SiH2Cl2, the first silane gas, decomposition temperature = 599° C.) and 30 mol % of trichlorosilane (SiHCl3, the second silane gas, decomposition temperature = 648° C.) were simultaneously flowed into one reactor.

[0061] Furthermore, the silane gas mixture was reacted in the reactor for 40 minutes and decomposed to prepare micrometer-sized silicon particles. In this case, the internal temperature of the reactor was 900° C. and the internal pressure was 5 bar. Then, the prepared silicon particles were cooled and recovered.

[0062] Comparative Example 1

[0063] According to the existing fluidized bed reactor method, silicon seed particles with a particle size of 600 μm are placed in the reactor, and 67 mol% hydrogen (H2) and 33 mol% trichlorosilane (SiHCl3) are flowed into the reactor together and reacted for 2 hours to prepare silicon particles. In this case, the internal temperature of the reactor is 900° C. and the internal pressure is 5 bar.

[0064] Comparative Example 2

[0065] Metal silicon (MG-Si, Elpion, particles smaller than 45 μm classified using a sieve) was pulverized to have a size similar to that of Example 1 using a ball mill (Zirconia).

[0066] Experimental Example 1: Silicon Particle Size

[0067] The sizes of the silicon particles of Example 1 and Comparative Example 2 were measured using a laser diffraction particle size analyzer (LS13320, Beckman Coulter). The millimeter-sized particles of Comparative Example 1 were measured using a digital caliper (Mitutoyo). The results are shown in Table 1 below.

[0068] Table 1

[0069]

[0070] As shown in Table 1, it was confirmed that the silicon particles prepared according to Example 1 had a micrometer size. In contrast, it was confirmed that the silicon particles of Comparative Example 1 prepared using seed particles were large silicon particles of millimeter size.

[0071] Experimental Example 2: Metal impurity content

[0072] The contents of metal impurities in the silicon particles of Example 1 and Comparative Example 2 are shown in the following Table 2. In this case, the contents of metal impurities were measured using an "iCAP 7600" apparatus manufactured by Thermo Fisher.

[0073] Table 2

[0074]

[0075]

[0076] As shown in Table 2, it was confirmed that Comparative Example 2 contained about 12,700 metal impurities.

[0077] As described above, silicon particles can be crushed to have a similar size as in Example 1, but in this case, there is a problem of a large content of impurities. Example 1 can prepare silicon microparticles without including an additional crushing process, and in this case, the content of impurities can also be reduced.

[0078] Experimental Example 3: Grain Size

[0079] The average size of the crystallites included in the silicon particles prepared in the examples and comparative examples was measured by X-ray diffraction (XRD, Panalytical Company, Empyrean XRD). The results are shown in Table 3 below.

[0080] Table 3

[0081] Example 1 Comparative Example 1 Comparative Example 2 Average grain size 41.7nm 58.6nm 151.9nm

[0082] As shown in Table 3, it was confirmed that the silicon particles of Example 1 include small crystal grains.

[0083] The above is described in more detail with reference to the embodiments and drawings of this specification, but this specification is not limited to the embodiments and drawings, and various modifications can be implemented without departing from the technical ideas of this specification. Therefore, the embodiments disclosed in this specification are not used to limit the technical ideas of the present invention, but are used for explanation, and the scope of the technical ideas of the present invention is not limited to the embodiments. Therefore, no matter from which aspect, the embodiments described above are only illustrative and should not be interpreted as limiting. The protection scope of this specification and the present invention should be interpreted by the scope of protection of the invention claims, and all technical ideas within the same scope should be interpreted as included in the scope of rights of this specification and the present invention.

Claims

1. A method for preparing silicon microparticles, characterized in that: include: the step of flowing a silane gas mixture into the reactor; and a step of decomposing the silane gas mixture in the reactor to prepare silicon microparticles, The silane gas mixture comprises a first silane gas and a second silane gas, The decomposition temperature of the first silane gas is lower than the decomposition temperature of the second silane gas.

2. The method for preparing silicon microparticles according to claim 1, characterized in that: The silane gas mixture is two or more selected from the silane gases represented by Chemical Formula 1 or Chemical Formula 2, Chemical formula 1: SiH x Cl 4-x , where 0≤x≤4, x is an integer, Chemical formula 2: Si2H y Cl 6-y , where 0≤y≤6 and y is an integer.

3. The method for preparing silicon microparticles according to claim 1, characterized in that: The first silane gas has a decomposition temperature of 350° C. to 600° C., The second silane gas has a decomposition temperature of 600°C to 1000°C.

4. The method for preparing silicon microparticles according to claim 1, characterized in that: The first silane gas and the second silane gas flow into the reactor at a molar ratio of 1:30 to 1:

2.

5. The method for preparing silicon microparticles according to claim 1, characterized in that: In one of the reactors, the silane gas mixture is decomposed to generate silicon seed particles, which are then grown to prepare silicon fine particles.

6. The method for preparing silicon microparticles according to claim 1, characterized in that: No silicon rods or silicon seed particles are used.

7. The method for preparing silicon microparticles according to claim 1, characterized in that: The silicon fine particles are prepared by allowing the silane gas mixture to reside in the reactor for 5 to 60 minutes.

8. The method for preparing silicon microparticles according to claim 1, characterized in that: The temperature of the reactor is 700° C. to 1000° C., and the pressure is 1 bar to 10 bar.

9. A silicon microparticle, characterized in that: The silicon microparticles are prepared according to the method for preparing the silicon microparticles according to any one of claims 1 to 8.

10. The silicon microparticles according to claim 9, characterized in that The silicon microparticles have a size of 1 μm <d 10 <4μm, 2μm <d 50 <7μm and 4μm <d 90 <13μm particle size, The total metal impurity content is less than 2000ppm.

11. The silicon microparticles according to claim 9, characterized in that The average crystal size of the silicon fine particles is 60 nm or less.

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