Silicon-carbon composite for anode material of secondary battery and method for preparing same

Abstract

The present invention relates to a silicon-carbon composite for an anode material of a secondary battery and a method for preparing same and, more particularly, to a silicon-carbon composite for an anode material of a secondary battery and a method for preparing same, the silicon-carbon composite being capable of improving processability and improving the characteristics of a secondary battery by suppressing the generation of hydrogen gas (H2) due to contact between silicon and water when an aqueous slurry is prepared using a silicon-based anode material.

Description

Silicon-carbon composite for secondary battery anode material and method for manufacturing the same

[0001] The present invention relates to a silicon-carbon composite for use as a secondary battery anode material and a method for producing the same, and more specifically, to a silicon-carbon composite for use as a secondary battery anode material and a method for producing the same, which can improve processability and enhance the characteristics of a secondary battery by suppressing the generation of hydrogen gas (H2) due to contact between silicon and water when producing an aqueous slurry using a silicon-based anode material.

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

[0003] Among the above components, graphite-based materials, which are mainly used as cathode materials, are commercially available due to their excellent electrochemical performance and low cost, but their theoretical capacity is limited to 370 mAh / g, which limits their application to high-capacity secondary batteries.

[0004] To overcome the above limitations, non-graphite anode materials such as silicon, tin, and germanium are emerging as alternative materials. Among them, silicon has a theoretical capacity of 4,000–4,200 mAh / g, can store a very large amount of lithium per unit weight, and exhibits a high capacity of nearly 10 times that of graphite, so it is attracting attention as a material to replace graphite. However, compared to its high theoretical capacity, it has the problem of a large volume expansion of approximately 400% during the charge and discharge process.

[0005] Furthermore, during the secondary battery manufacturing process, when an aqueous slurry is prepared using silicon-based anode materials, hydrogen gas (H2) is generated when the silicon within the anode material comes into contact with water. This hydrogen gas can pose a problem not only during the mass production process of secondary batteries, but also can cause performance degradation during charge and discharge after battery manufacturing.

[0006] To solve the above hydrogen generation problem, a technology has been used to introduce a carbon coating layer onto the silicon surface of the cathode material.

[0007] However, most conventional technologies form a single coating layer on the silicon surface or the surface of an anode material containing silicon. This single coating layer is difficult to coat closely, increasing the likelihood of poorly formed layers. Furthermore, it is prone to damage during repeated charging and discharging of secondary batteries, ultimately exposing the silicon surface again and making it susceptible to water contact, making it difficult to address the hydrogen generation issue. Furthermore, even if the carbon layer is damaged just once, this damage allows water to penetrate deep into the silicon, limiting the generation of large amounts of hydrogen gas.

[0008] The present invention provides a silicon-carbon composite for use as a negative electrode material for a secondary battery, which can improve processability by suppressing the phenomenon of hydrogen gas generation due to contact between silicon and water even when producing an aqueous slurry, and can prevent contact between silicon and water in the negative electrode material during the charging and discharging process of a secondary battery, and a method for producing the same.

[0009] The purpose of the present invention is to provide a silicon-carbon composite and a method for manufacturing the same, which can improve the initial discharge capacity, initial efficiency, and lifespan characteristics of a secondary battery manufactured by including the composite as an anode material for a secondary battery.

[0010] The purpose of the present invention is not limited to the aforementioned purposes, and other unmentioned purposes and advantages of the present invention can be understood through the following description and will be more clearly understood through the embodiments of the present invention. Furthermore, it will be readily apparent that the purposes and advantages of the present invention can be realized by the means and combinations thereof set forth in the claims.

[0011] In order to achieve the above purpose, according to the first aspect of the present invention,

[0012] A carbon structure containing pores;

[0013] n silicon layers stacked within the pores of the carbon structure; and

[0014] comprising n carbon layers stacked on the silicon layer,

[0015] The above n silicon layers and n carbon layers have a structure in which silicon layers and carbon layers are alternately laminated, and the outermost layer is a carbon layer.

[0016] The above n is an integer from 3 to 30, and a silicon-carbon composite can be provided.

[0017] The thickness of one of the above carbon layers may be 0.5 nm to 5 nm, and the thickness of one of the above silicon layers may be 1 nm to 10 nm.

[0018] When the total weight of the above silicon-carbon composite is 100 wt%, the total content of silicon included in the silicon-carbon composite may be 50 wt% or more.

[0019] The above carbon structure includes first pores having a pore diameter of 2 nm or less, second pores having a pore diameter of more than 2 nm and less than 50 nm, and third pores having a pore diameter of more than 50 nm and less than 100 nm.

[0020] The pore volume of the first pore and the second pore is 0.15㎤ / g to 0.4㎤ / g, and the pore volume of the third pore is 0.2㎤ / g to 0.8㎤ / g,

[0021] The total pore volume of the above carbon structure may be 0.6 cm3 / g to 1.2 cm3 / g.

[0022] The total thickness of the silicon layer and the carbon layer may be 30 nm to 150 nm or less.

[0023] The silicon in the above silicon-carbon composite may suppress the phenomenon of hydrogen gas generation due to contact with water.

[0024] According to a second aspect of the present invention, a negative electrode material for a secondary battery comprising a silicon-carbon composite according to the first aspect of the present invention can be provided.

[0025] According to a third aspect of the present invention, a secondary battery including a negative electrode material for a secondary battery including a silicon-carbon composite according to the first aspect of the present invention can be provided.

[0026] According to a fourth aspect of the present invention, there is provided a method for producing a silicon-carbon composite according to the first aspect of the present invention,

[0027] (S1) A step of placing a carbon structure including pores in a chemical vapor deposition (CVD) reactor;

[0028] (S2) A step of injecting purge gas into the chemical vapor deposition reactor and raising the temperature to atmospheric pressure and 400°C to 550°C;

[0029] (S3) A step of depositing a silicon layer on the carbon structure by simultaneously supplying silicon source gas and hydrogen gas;

[0030] (S4) Flushing step of removing gases other than purge gas by injecting only purge gas;

[0031] (S5) A step of simultaneously supplying a carbon source gas and a carrier gas to deposit a carbon layer on the silicon layer;

[0032] (S6) Flushing step of removing gases other than purge gas by injecting only purge gas; and

[0033] (S7) a step of cooling the resultant of (S6) to obtain a silicon-carbon composite;

[0034] By repeating the above steps (S3) to (S6) n times or more, n silicon layers and n carbon layers are alternately stacked in the carbon structure,

[0035] The above n is selected from an integer from 1 to 30,

[0036] A method for manufacturing a silicon-carbon composite can be provided.

[0037] The above purge gas and carrier gas may each include an inert gas.

[0038] The above carbon source gases are methane (CH4) gas, ethane (C2H6) gas, propane (C3H8) gas, butane (C4H 10 ) gas, acetylene (C2H2) gas, and ethylene (C2H4) gas.

[0039] The above silicon source gas may include at least one selected from the group consisting of monosilane (SiH4) gas, disilane (Si2H6) gas, monochlorosilane (SiH3Cl) gas, dichlorosilane (SiH2Cl2) gas, trichlorosilane (SiHCl3) gas, and trimethylsilane (SiH(CH3)3) gas.

[0040] The above chemical vapor deposition (CVD) reactor may be a chemical vapor deposition reactor having a rotary kiln.

[0041] The above carbon structure includes first pores having a pore diameter of 2 nm or less, second pores having a pore diameter of more than 2 nm and less than 50 nm, and third pores having a pore diameter of more than 50 nm and less than 100 nm.

[0042] The pore volume of the first pore and the second pore is 0.15㎤ / g to 0.4㎤ / g,

[0043] The pore volume of the third pore is 0.2 cm3 / g to 0.8 cm3 / g,

[0044] The total pore volume of the above carbon structure may be 0.6 cm3 / g to 1.2 cm3 / g.

[0045] In the above step (S3), the silicon source gas and hydrogen gas may be supplied at a ratio of 1:2 to 1:20 (unit: sccm).

[0046] The silicon-carbon composite of the present invention can improve processability (process efficiency and process stability) by suppressing the phenomenon of hydrogen gas generation due to contact between silicon and water in the process of manufacturing an aqueous slurry by applying it as a cathode material.

[0047] When the silicon-carbon composite of the present invention is applied as an anode material to manufacture a secondary battery, it can prevent contact between silicon and water in the anode material during the charging and discharging process of the secondary battery, thereby suppressing the phenomenon of hydrogen gas generation occurring during the charging and discharging process.

[0048] When the silicon-carbon composite of the present invention is applied as an anode material for a secondary battery, it can secure the charge / discharge stability of the secondary battery and improve the discharge capacity, efficiency, and life characteristics of the secondary battery.

[0049] In addition to the effects described above, the effects of the present invention are described together with the description of matters for carrying out the invention below.

[0050] Figure 1 is a schematic diagram of a silicon-carbon composite according to one embodiment of the present invention.

[0051] Figure 2 is a graph showing the change in volume of a cathode slurry according to storage time according to an experimental example of the present invention.

[0052] The above-described objects, features, and advantages will be described in detail below with reference to the accompanying drawings, so that those skilled in the art can easily practice the technical idea of ​​the present invention. In describing the present invention, if it is determined that a detailed description of known technologies related to the present invention may unnecessarily obscure the gist of the present invention, a detailed description thereof will be omitted. Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the drawings, the same reference numerals are used to indicate the same or similar components.

[0053] In this specification, when the terms "includes," "contains," "has," "consists of," "arranges," and "provides" are used for a component, other parts may be added unless "only" is used. When a component is expressed in the singular, it includes the plural unless otherwise explicitly stated.

[0054] Unless there is a specific limitation on the unit in this specification, the standard for the unit is interpreted as weight (wt).

[0055] In interpreting the components in this specification, even if there is no separate explicit description, it is interpreted to include the range of error.

[0056] Hereinafter, the present invention will be described in more detail.

[0057] silicon-carbon composites

[0058] According to one embodiment of the present invention, a silicon-carbon composite is

[0059] A carbon structure containing pores;

[0060] n silicon layers stacked within the pores of the carbon structure; and

[0061] comprising n carbon layers stacked on the silicon layer,

[0062] The above n silicon layers and n carbon layers have a structure in which silicon layers and carbon layers are alternately laminated, and the outermost layer is a carbon layer.

[0063] The above n is an integer from 3 to 30.

[0064] The present invention is characterized in that silicon layers and carbon layers are alternately laminated, and unlike the structure disclosed in the prior art in which one or two layers are laminated, three or more layers are laminated. When a structure in which silicon layers and carbon layers are alternately laminated is formed in this way, the area and possibility of silicon and water coming into contact during the manufacture of a negative electrode material slurry for a secondary battery are reduced, so there is an advantage in that the problem of hydrogen gas being generated due to contact between silicon and water can be resolved.

[0065] In the present invention, since the silicon layer and the carbon layer are each laminated in the same number, the number of such layers is represented as n. If n is too small, the effect of preventing contact between silicon and water as intended in the present invention is reduced, and if n is too large, the complexity and inefficiency of the process increase. It was experimentally confirmed that when n is a certain number or more, the effect of suppressing hydrogen gas generation is almost the same. For example, if n is 3, it means that 3 silicon layers and 3 carbon layers are laminated.

[0066] For example, n may be 3 or greater, n may be 4 or greater, n may be 8 or greater, and n may be 12 or greater.

[0067] In order to exhibit the gas generation reduction effect targeted in the present invention, it is preferable that n is 3 or more, and when n is 4 or more, the gas generation reduction effect can be further increased. Meanwhile, because the preferable content of silicon to be deposited (appropriate ratio of the entire cathode material) is determined due to the discharge capacity of the cathode material, and depositing silicon in 16 or more layers reduces efficiency in terms of process time and cost, greatly increases process difficulty, and may reduce deposition yield, it is preferable that n is 30 or less, for example, n may be 20 or less, or for example, n may be 15 or less.

[0068] As one embodiment of the present invention, a structure in which four silicon layers and four carbon layers are each stacked within the pores of a carbon structure (when n is 4) is schematically illustrated in Fig. 1.

[0069] In addition, the outermost layer of the coating layer structure of the silicon-carbon composite of the present invention is characterized by being a carbon layer, which can effectively prevent contact between silicon and water by allowing the outermost carbon layer to function as a type of coating layer. In addition, the outermost carbon layer can secure electrical conductivity as an anode material and, when applied to secondary batteries, can exhibit effects such as improved lifespan.

[0070] It is preferable that the thickness of one carbon layer is formed to be 0.5 nm to 5 nm, and the thickness of one silicon layer is formed to be 1 nm to 10 nm.

[0071] The total thickness of the structure in which the n silicon layers and n carbon layers are alternately laminated may be 30 nm to 150 nm or less, and preferably 50 nm to 100 nm or less.

[0072] In the present invention, it is important to control the total thickness of the structure in which silicon layers and carbon layers are alternately laminated to 100 nm or less, so that the silicon layers and carbon layers can be laminated within pores of the carbon structure of 100 nm or less.

[0073] While laminating the silicon layer and the carbon layer, a portion of the silicon layer and / or the carbon layer may be laminated outside the pores of the carbon structure by chemical vapor deposition, but preferably, by controlling the lamination to occur within the pores, the silicon layer can be protected from the electrolyte, thereby preventing the limitation of volume expansion, the problem of hydrogen gas generation, and the resulting deterioration of the performance of the secondary battery.

[0074] The average particle size of the silicon particles included in the silicon-carbon composite of the present invention is preferably 20 nm or less, and more preferably 10 nm or less. This allows silicon particles controlled to be maintained intact without breaking during volume expansion and contraction, and when applied as an anode material for an actual secondary battery, it can contribute to improving the efficiency and lifespan characteristics of the secondary battery.

[0075] According to one embodiment of the present invention, when the total weight of the silicon-carbon composite is 100 wt%, the total content of silicon contained in the silicon-carbon composite is preferably 50 wt% or more, and preferably 95 wt% or less. This is to improve capacity when applied as an anode material for secondary batteries. In addition, in the silicon-carbon composite of the present invention, since most of the silicon exists in a large amount inside the carbon structure, it can be protected from the electrolyte, and thus has the advantage of exhibiting a higher capacity.

[0076] The first pore and the second pore of the carbon structure including the pores of the present invention satisfy that the pore diameter is 50 nm or less, and includes micropores having a pore diameter of 2 nm or less and mesopores having a pore diameter of 2 nm to 50 nm.

[0077] In the present invention, silicon particles can be impregnated or deposited into the first pore and the second pore, which are micropores of a carbon structure including pores. The first pore and the second pore can increase the surface area of ​​the carbon substrate to contain a large amount of silicon nanoparticles having a high energy density, and as a result, can realize high-capacity characteristics of a secondary battery as an anode active material of the secondary battery.

[0078] Therefore, when a certain amount of first and second pores are secured, it can contribute to improving the capacity of the secondary battery when applied as a negative electrode active material of the secondary battery.

[0079] Meanwhile, if the number of first and second pores is too large, a surface is left unfilled with silicon, and a large amount of SEI (solid electrolyte interphase layer) is generated there, which may cause a problem of reduced initial efficiency of the secondary battery when applied as an anode material in a secondary battery.

[0080] From this point of view, the pore volume of the first pore and the second pore is preferably 0.15 to 0.4 cm3 / g, and in the present invention, the pore volume of the first pore and the second pore is measured by a nitrogen adsorption method and analyzed by density-functional theory (DFT).

[0081] The third pore of the carbon structure including the pores of the present invention is a macropore having a pore diameter exceeding 50 nm, and in the present invention, a pore having a pore diameter of 50 nm to 100 nm is referred to as the third pore.

[0082] In the present invention, the third pore of the carbon structure including pores is a relatively large pore, and must be included in a certain amount or more to provide a space in which the silicon layer and the carbon layer can be laminated. From this perspective, the pore volume of the third pore is preferably 0.2 cm3 / g to 0.8 cm3 / g. In the present invention, the pore volume of the third pore is measured by mercury porosimetry.

[0083] According to one embodiment of the present invention, the total pore volume occupied by the first pore, the second pore, and the third pore in the carbon structure including the pores is preferably 0.6 cm3 / g to 1.2 cm3 / g, which is to provide sufficient pores in the carbon structure including the pores to achieve the above-described effects, including appropriate impregnation of silicon particles.

[0084] Method for manufacturing silicon-carbon composites

[0085] According to one embodiment of the present invention, a method for producing a silicon-carbon composite is provided, and the produced silicon-carbon composite can satisfy the characteristics of the silicon-carbon composite of the present invention described above.

[0086] According to one aspect of the present invention,

[0087] (S1) A step of placing a carbon structure including pores in a chemical vapor deposition (CVD) reactor;

[0088] (S2) A step of injecting purge gas into the chemical vapor deposition (CVD) reactor and raising the temperature to atmospheric pressure and 400°C to 550°C;

[0089] (S3) A step of depositing a silicon layer on the carbon structure by simultaneously supplying silicon source gas and hydrogen gas;

[0090] (S4) Flushing step of removing gases other than purge gas by injecting only purge gas;

[0091] (S5) A step of simultaneously supplying a carbon source gas and a carrier gas to deposit a carbon layer on the silicon layer;

[0092] (S6) Flushing step of removing gases other than purge gas by injecting only purge gas; and

[0093] (S7) a step of cooling the resultant of (S6) to obtain a silicon-carbon composite;

[0094] By repeating the above steps (S3) to (S6) n times or more, n silicon layers and n carbon layers are alternately stacked in the carbon structure,

[0095] The above n is selected from an integer from 3 to 30,

[0096] A method for manufacturing a silicon-carbon composite is provided.

[0097] In conventional technology, fine silicon particles are known to be primarily formed through chemical vapor deposition. However, controlling silicon particles to less than 10 nm requires a very complex technology. Currently known methods include depositing silicon within the micropores of carbon structures with a fine pore distribution to control the silicon size, or coating the surface of carbon particles, such as graphite, with a silicon thin film thickness of less than 10 nm.

[0098] However, unlike the prior art, the present invention is characterized in that silicon layers and carbon layers are alternately laminated within the pores of a carbon structure having a porous structure, i.e., including pores, so that most of the silicon layers are present within the pores of the carbon structure.

[0099] Accordingly, the silicon-carbon composite of the present invention can contain a large amount of silicon, thereby realizing a high capacity, and since the silicon exists within the pores of the carbon structure, the amount and frequency of contact with the electrolyte are reduced, thereby providing an advantage in alleviating and eliminating volume expansion and problems caused by it.

[0100] In addition, when the silicon-carbon composite of the present invention is applied as an anode material to manufacture a secondary battery, it can prevent contact between silicon and water in the anode material during the charging and discharging process of the secondary battery, thereby suppressing the phenomenon of hydrogen gas generation occurring during the charging and discharging process.

[0101] According to one embodiment of the present invention, the reactor used in the step (S1) may be a CVD reactor equipped with a tube furnace or a rotary tube furnace.

[0102] The carbon structure including pores used in the above step (S1) is the same as that described in the above silicon-carbon composite.

[0103] According to one embodiment of the present invention, in order to control the overall reaction rate and obtain a uniform homogeneous reaction product, the step (S2) is performed under a purge gas atmosphere, such that a purge gas is injected together with the temperature of the reactor when the temperature of the reactor is increased. The purge gas may be an inert gas, and may include, for example, one or more of helium gas, neon gas, krypton gas, xenon gas, radon gas, nitrogen gas, and argon gas, but is not necessarily limited thereto.

[0104] According to one embodiment of the present invention, the temperature conditions of the step (S2) are for performing a deposition reaction, and may be, for example, 400°C to 550°C, for example, 450°C to 500°C, and the temperature raised in the step (S2) is maintained until the end of the reaction.

[0105] In the above step (S3), a silicon source gas and hydrogen gas are supplied simultaneously to deposit a silicon layer on the carbon structure.

[0106] The above silicon source gas may include at least one selected from the group consisting of monosilane (SiH4) gas, disilane (Si2H6) gas, monochlorosilane (SiH3Cl) gas, dichlorosilane (SiH2Cl2) gas, trichlorosilane (SiHCl3) gas, and trimethylsilane (SiH(CH3)3) gas; however, if it is for depositing a silicon layer, another type of silicon source gas may be used.

[0107] In order to suppress the reactivity of Si radicals generated when Si-H bonds are broken during the silicon deposition reaction and obtain a uniform Si-C composite, hydrogen (H2) gas is supplied together in the step (S3). If hydrogen gas is not supplied, the thermal decomposition products of the silicon gas may be mostly concentrated at the front of the reactor, which may cause a problem of uneven Si distribution.

[0108] In order to satisfy the characteristics of the silicon particles, particularly the characteristics of crystallinity and crystallite size, in the silicon-carbon composite according to one embodiment of the present invention, the ratio of the silicon source and the hydrogen gas can be controlled. For example, in the step (S3), the silicon source gas and the hydrogen gas can be supplied at a ratio (unit: sccm) of 1:2 to 1:20, preferably, the silicon source gas and the hydrogen gas can be supplied at a ratio (unit: sccm) of 1:5 to 1:15, and more preferably, the silicon source gas and the hydrogen gas can be supplied at a ratio (unit: sccm) of 1:7 to 1:10, but is not necessarily limited thereto.

[0109] The above step (S4) is a flushing step that removes gases other than the purge gas by injecting only the purge gas. In the silicon-carbon composite targeted in the present invention, silicon particles having an average size of 20 nm or less must be contained in an amount of at least 50 wt%, and the silicon layer and carbon layer must be laminated without interference with each other to be advantageous in suppressing hydrogen gas generation.

[0110] That is, if the silicon layer and the carbon layer are not laminated without interference, the silicon-carbon bond is deposited in a silicon carbide (SiC) state, which reduces the reactivity with lithium ions, and as a result, the lifespan and efficiency of the secondary battery are reduced. Therefore, it is important that the silicon layer and the carbon layer are laminated without interference, as in the present invention. If the silicon layer and the carbon layer are laminated with interference, a connection path may be created between the silicon layers, which results in moisture coming into contact on the particle surface being transferred to the inside of the silicon, making it difficult to suppress hydrogen gas generation. If the silicon layer and the carbon layer are laminated without interference, as in the present invention, the generation of hydrogen gas can be suppressed, and there is an advantage in that it is advantageous in the mass production process.

[0111] Therefore, in order to laminate a pure silicon layer and a pure carbon layer without interference between the silicon layer and the carbon layer, a flushing step is absolutely necessary, which is a process of removing the silicon source gas, hydrogen gas, etc. that were injected to laminate the silicon layer remaining in the reactor by injecting only purge gas.

[0112] The above purge gas may include an inert gas, and may be selected from at least one of helium gas, neon gas, krypton gas, xenon gas, radon gas, nitrogen gas, or argon gas.

[0113] In the above step (S5), a carbon source gas and a carrier gas can be supplied simultaneously to deposit a carbon layer on the silicon layer of the carbon structure.

[0114] The above carbon source gases are methane (CH4) gas, ethane (C2H6) gas, propane (C3H8) gas, butane (C4H 10 ) gas, acetylene (C2H2) gas and ethylene (C2H4) gas, but other types of carbon source gases may be used if the purpose is to deposit a carbon layer.

[0115] The above carrier gas plays a role in moving the carbon source gas by itself depending on the type of gas when the deposition source gas is introduced into the reactor.

[0116] The carrier gas may be selected from nitrogen gas or argon gas.

[0117] In the above step (S5), the carbon source gas and the carrier gas may be supplied at a ratio (unit: sccm) of 1:2 to 1:20 for the carbon source gas and the carrier gas, preferably at a ratio (unit: sccm) of 1:5 to 1:15 for the carbon source gas and the carrier gas, and more preferably at a ratio (unit: sccm) of 1:7 to 1:10 for the carbon source gas and the carrier gas, but is not necessarily limited thereto.

[0118] The carrier gas may include an inert gas, and may be selected from at least one of helium gas, neon gas, krypton gas, xenon gas, radon gas, nitrogen gas, or argon gas.

[0119] The above step (S6) is the same as step (S4), and is a flushing step that injects only purge gas to remove gases other than the purge gas. As intended in the present invention, the silicon-carbon composite must contain at least 50 wt% of silicon particles having an average size of 20 nm or less, and it is preferable that the silicon layer and the carbon layer are laminated without interference with each other.

[0120] Therefore, in order to laminate a pure silicon layer and a pure carbon layer without interference between the silicon layer and the carbon layer, a flushing step is absolutely necessary, which is a process of removing the carbon source gas, hydrogen gas, etc. that were injected to laminate the carbon layer remaining in the reactor by injecting only purge gas.

[0121] By repeating the above steps (S3) to (S6) 6 or more times, each of 6 or more silicon layers and 6 or more carbon layers are alternately laminated within the carbon structure, and preferably, each of 6 to 15 silicon layers and 6 to 15 carbon layers can be alternately laminated.

[0122] At this time, since the carbon structure contains large pores, a silicon layer or a carbon layer is first laminated inside the pores, and after the inside of the pores is filled with the silicon layer or the carbon layer, a portion of the silicon layer or the carbon layer may be laminated outside the carbon structure. In the present invention, the thickness of each carbon layer is controlled to be 10 nm or less, and the deposition conditions of steps (S3) and (S5) are controlled so that the thickness of each silicon layer is controlled to be 20 nm or less, and the flushing steps of steps (S4) and (S6) are performed, so that pure silicon layers and carbon layers can be alternately laminated.

[0123] In the above step (S7), the final result can be cooled to room temperature of 15°C to 25°C and deposited in a crucible.

[0124] Hereinafter, the present invention will be described in more detail through examples and experimental examples. However, the following examples and experimental examples are merely illustrative of the present invention, and the content of the present invention is not limited to the following examples and experimental examples.

[0125] Example 1

[0126] (a) Approximately 5 g of a carbon structure satisfying the conditions in Table 1 below was placed on a crucible in a chemical vapor deposition reactor equipped with a rotary kiln as a reaction device, and argon gas was purged at 450 sccm as a purge gas for 1 hour. Then, the rotary kiln was heated to a temperature of 455°C at a rate of 10°C / min while rotating at a rotation speed of 0.5 rpm.

[0127] (b) In a reaction device heated to 455°C, at atmospheric pressure, a mixture of SiH4 gas and hydrogen gas (SiH4 gas: hydrogen gas = 50 sccm: 450 sccm) was injected to deposit a silicon layer with a thickness of 10 nm by chemical vapor deposition for 15 minutes.

[0128] (c) With all gas inlet valves closed, only argon gas was injected at 450 sccm for 10 minutes to flush out any remaining gas.

[0129] (d) A mixture of C2H2 gas and argon gas (C2H2 gas: argon gas = 50 sccm: 450 sccm) was injected to deposit a carbon layer with a thickness of 2 nm through chemical vapor deposition for 15 minutes.

[0130] (e) With all gas inlet valves closed, only argon gas was injected at 450 sccm for 10 minutes to flush out any remaining gas.

[0131] The above processes (b) to (e) were repeated three more times to alternately stack a total of four silicon layers and a total of four carbon layers, and then cooled at room temperature to obtain a final silicon-carbon composite (a structure having a total of eight silicon layers and carbon layers).

[0132] [Table 1]

[0133]

[0134] Example 2

[0135] The same procedure as in Example 1 was repeated, but the processes (b) to (e) were repeated 7 more times to alternately stack a total of 8 silicon layers and a total of 8 carbon layers, and then cooled at room temperature to obtain a final silicon-carbon composite (a structure having a total of 16 silicon layers and carbon layers).

[0136] Example 3

[0137] The same procedure as in Example 1 was repeated, but the processes (b) to (e) were repeated 11 more times to alternately stack a total of 12 silicon layers and a total of 12 carbon layers, and then cooled at room temperature to obtain a final silicon-carbon composite (a structure having a total of 24 silicon layers and carbon layers).

[0138] Comparative Example 1

[0139] The same procedure as in Example 1 was followed, but the processes (b) to (e) were not repeated any more, and the final silicon-carbon composite (having a structure with a total of two silicon layers and a carbon layer) was obtained by cooling at room temperature.

[0140] Experimental Example - Hydrogen Gas Generation Experiment

[0141] Slurry manufacturing

[0142] The silicon-carbon composites manufactured in Example 1 and Comparative Example 1 were used as a cathode material. Specifically, the following materials 1) to 6) were added to deionized water (DI water) and mixed using a thinky mixer to manufacture a slurry having a solid content of 45% based on deionized water (DI water).

[0143] 1) Silicon-carbon composite cathode material: 0.6 g

[0144] 2) Graphite: 2.4 g

[0145] 3) Conductive carbon black (Super-P): 0.313 g

[0146] 4) Carboxymethyl cellulose: 0.0532 g

[0147] 5) Styrene-butadiene rubber (50 wt% in H2O): 0.0939 g

[0148] 6) Carbon nanotube conductive agent (SWCNT) (0.4 wt% in H2O): 0.783 g

[0149] Gas generation measurement

[0150] 4.16 g of the slurry prepared above was placed in an aluminum pouch foil, sealed, and the amount of gas generated was measured using the Archimedes method as follows. Specifically, the measuring cylinder was filled with water and the initial reading was checked.

[0151] The pouch volume was measured by completely submerging the pouch foil containing the slurry in water and measuring the increased volume.

[0152] After storing the measuring cylinder in a constant temperature chamber at 60℃, the volume was measured every day to determine the increased volume.

[0153] The experimental results of Examples 1 to 3 and Comparative Example 1 are each shown graphically in Fig. 2.

[0154] The amount of gas generated was calculated using the following equation (1) and shown in Table 2 below.

[0155] <Formula 1> Gas generation amount (cc / g) = Increased volume / Slurry weight

[0156] [Table 2]

[0157]

[0158] As can be seen in Table 2 and Fig. 2, the silicon-carbon composite of Comparative Example 1 containing only one outer carbon layer continuously generated hydrogen gas, but it was confirmed that the silicon-carbon composites of Examples 1 to 3 containing multiple carbon layers hardly generated hydrogen gas, and in particular, it was confirmed that hydrogen gas hardly generated when there were 8 or more silicon layers and carbon layers.

[0159] Although the embodiments of the present specification have been described in more detail with reference to the attached drawings, the present specification is not necessarily limited to these embodiments, and various modifications may be implemented without departing from the technical spirit of the present specification. Therefore, the embodiments disclosed in this specification are not intended to limit the technical spirit of the present specification, but to explain, and the scope of the technical spirit of the present specification is not limited by these embodiments. Therefore, it should be understood that the embodiments described above are illustrative in all respects and not restrictive. The scope of protection of this specification should be interpreted by the claims, and all technical ideas within a scope equivalent thereto should be interpreted as being included in the scope of rights of this specification.

Claims

1. Carbon structure containing pores; n silicon layers stacked within the pores of the carbon structure; and comprising n carbon layers stacked on the silicon layer, The above n silicon layers and n carbon layers have a structure in which silicon layers and carbon layers are alternately laminated, and the outermost layer is a carbon layer. The above n is an integer from 3 to 30, Silicon-carbon composite.

2. In paragraph 1, The above n is an integer from 8 to 15, Silicon-carbon composite.

3. In paragraph 1, The thickness of one of the above carbon layers is 0.5 nm to 5 nm, The thickness of one of the above silicon layers is 1 nm to 10 nm, Silicon-carbon composite.

4. In paragraph 1, When the total weight of the above silicon-carbon composite is 100 wt%, the total content of silicon included in the silicon-carbon composite is 50 wt% or more. Silicon-carbon composite.

5. In paragraph 1, The above carbon structure includes first pores having a pore diameter of 2 nm or less, second pores having a pore diameter of more than 2 nm and less than 50 nm, and third pores having a pore diameter of more than 50 nm and less than 100 nm. The pore volume of the first pore and the second pore is 0.15㎤ / g to 0.4㎤ / g, and the pore volume of the third pore is 0.2㎤ / g to 0.8㎤ / g, The total pore volume of the above carbon structure is 0.6 ㎤ / g to 1.2 ㎤ / g, Silicon-carbon composite.

6. In paragraph 1, The total thickness of the silicon layer and the carbon layer is 30 nm to 150 nm or less. Silicon-carbon composite.

7. In paragraph 1, The silicon in the above silicon-carbon composite suppresses the phenomenon of hydrogen gas generation due to contact with water. Silicon-carbon composite.

8. A negative electrode material for a secondary battery comprising a silicon-carbon composite according to any one of claims 1 to 7.

9. A secondary battery comprising a negative electrode material for a secondary battery comprising a silicon-carbon composite according to any one of claims 1 to 7.

10. A method for manufacturing a silicon-carbon composite according to any one of claims 1 to 7, (S1) A step of placing a carbon structure including pores in a chemical vapor deposition (CVD) reactor; (S2) A step of injecting purge gas into the chemical vapor deposition reactor and raising the temperature to atmospheric pressure and 400°C to 550°C; (S3) A step of depositing a silicon layer on the carbon structure by simultaneously supplying silicon source gas and hydrogen gas; (S4) Flushing step of removing gases other than purge gas by injecting only purge gas; (S5) A step of simultaneously supplying a carbon source gas and a carrier gas to deposit a carbon layer on the silicon layer; (S6) Flushing step of removing gases other than purge gas by injecting only purge gas; and (S7) a step of cooling the resultant of (S6) to obtain a silicon-carbon composite; By repeating the above steps (S3) to (S6) n times or more, n silicon layers and n carbon layers are alternately stacked in the carbon structure, The above n is selected from an integer from 1 to 30, Method for producing a silicon-carbon composite.

11. In paragraph 10, The above purge gas and carrier gas each contain an inert gas, Method for producing a silicon-carbon composite.

12. In paragraph 10, The above carbon source gases are methane (CH4) gas, ethane (C2H6) gas, propane (C3H8) gas, butane (C4H 10 ) gas, acetylene (C2H2) gas and ethylene (C2H4) gas, comprising at least one selected from the group consisting of Method for producing a silicon-carbon composite.

13. In paragraph 10, The above silicon source gas includes at least one selected from the group consisting of monosilane (SiH4) gas, disilane (Si2H6) gas, monochlorosilane (SiH3Cl) gas, dichlorosilane (SiH2Cl2) gas, trichlorosilane (SiHCl3) gas, and trimethylsilane (SiH(CH3)3) gas. Method for producing a silicon-carbon composite.

14. In paragraph 10, The above chemical vapor deposition (CVD) reactor is a chemical vapor deposition reactor equipped with a rotary kiln. Method for producing a silicon-carbon composite.

15. In paragraph 10, The above carbon structure includes first pores having a pore diameter of 2 nm or less, second pores having a pore diameter of more than 2 nm and less than 50 nm, and third pores having a pore diameter of more than 50 nm and less than 100 nm. The pore volume of the first pore and the second pore is 0.15㎤ / g to 0.4㎤ / g, The pore volume of the third pore is 0.2 cm3 / g to 0.8 cm3 / g, The total pore volume of the above carbon structure is 0.6 ㎤ / g to 1.2 ㎤ / g, Method for producing a silicon-carbon composite.

16. In paragraph 10, In the above step (S3), the silicon source gas and hydrogen gas are supplied at a ratio of 1:2 to 1:20 (unit: sccm). Method for producing a silicon-carbon composite.

Images