Carbon-silicon composite, manufacturing method therefor, and negative electrode active material and all-solid-state battery including same

Abstract

The present invention relates to a carbon-silicon / carbon composite in which a silicon / carbon composite matrix is formed on the surface of and / or inside the pores of a porous carbon support having controlled pore properties, and to a manufacturing method therefor. When used as an anode active material, the carbon–silicon / carbon composite according to an embodiment of the present invention provides excellent electrical conductivity and can alleviate stress caused by the volume expansion of silicon.

Description

Carbon-silicon composite, method for producing the same, negative electrode active material and all-solid-state battery containing the same

[0001] The present invention relates to a carbon-silicon composite, and more particularly, to a carbon-silicon composite, a method for producing the same, a negative electrode active material including the same, and an all-solid-state battery.

[0002] Carbon materials are materials made of carbon, one of the most abundant resources on Earth. Carbon materials are extremely lightweight, strong, and possess excellent electrical and thermal conductivity, making them a key material widely used in fields such as hydrogen vehicles, aviation, secondary batteries, and high-end consumer goods.

[0003] Carbon materials can be manufactured from various raw materials such as palm shell, polyacrylonitrile, rayon, and pitch. Among these, it is difficult to control the molecular weight and composition of carbon materials manufactured from solid raw materials such as palm shell (Republic of Korea Patent Application Publication No. 10-2019-0093960).

[0004] On the other hand, pitch, a viscoelastic solid polymer extracted from crude oil or plants, has the advantages of high yield when converted into carbon materials, low cost of raw materials, and its molecular structure is closer to the graphite structure than other raw materials, which can reduce the energy required for heat treatment (U.S. Patent Nos. 4,242,196 and 4,340,464).

[0005] In particular, pyrolysis fuel oil (PFO), naphtha cracking bottom oil (NCB), vacuum residue (VR), and fluid catalytic cracking decant oil (FCC-DO), which are obtained as by-products in the petroleum refining process, have a high content of aromatic compounds and a low content of impurities such as sulfur and nitrogen, and therefore pitch manufactured from them is attracting attention as a material for carbon materials.

[0006] Meanwhile, attempts are being made to use silicon-based anode active materials to improve the capacity of secondary batteries. Silicon, with its theoretically very high energy density, is attracting attention as a next-generation battery anode material to replace graphite. However, its volume increases by up to 300% during charge and discharge, leading to fragmentation of the silicon anode active material and severely reduced mechanical stability.

[0007] Accordingly, research has been conducted to solve these problems, but in the case of conventional negative active materials, there was a problem in that problems such as fragmentation due to volume expansion and decreased electrochemical performance were not sufficiently resolved.

[0008] The present invention provides a carbon-silicon composite coated with a film-shaped silicon layer including the surface of a carbon support.

[0009] Another object of the present invention is to provide a method for producing the carbon-silicon composite.

[0010] Another object of the present invention is to provide a negative electrode active material comprising the carbon-silicon composite.

[0011] In order to solve the above-described problem, the present invention provides a method for manufacturing a carbon-silicon composite, including a step of manufacturing a carbon-silicon composite by forming a film-shaped silicon layer including the surface of a carbon support.

[0012] According to one embodiment of the present invention, the step of manufacturing the carbon-silicon composite can be performed by applying a silicon source to the carbon support by chemical vapor deposition (CVD).

[0013] Additionally, the supply flow rate of the silicon source may be 50 to 300 sccm per 10 g of the carbon support.

[0014] Additionally, the chemical vapor deposition can be performed for 40 to 120 minutes.

[0015]

[0016] In addition, the present invention provides a carbon-silicon composite comprising a carbon support and a silicon layer in a film shape disposed including a surface of the carbon support.

[0017] According to one embodiment of the present invention, the carbon support may include a non-porous carbon support including at least one of hard carbon and soft carbon.

[0018] Additionally, the carbon support may include a porous carbon support, and the silicon layer may be disposed on the surface and inside the pores of the porous carbon support.

[0019] Additionally, the carbon-silicon composite may have a specific surface area of ​​200 m2 / g or less.

[0020] Additionally, the porous carbon support may have a volume ratio of mesopores having a pore size of 2 to 50 nm of 10 to 80% based on the total pore volume.

[0021] In addition, the porous carbon support may have a BET specific surface area of ​​300 to 3,000 m2 / g and a tap density of 0.05 to 0.5 g / ㎖.

[0022] In addition, the carbon support may have a particle size distribution D50 of 2 to 15 μm and a particle size distribution Dmax of 25 μm or less.

[0023] Additionally, the average thickness of the silicon layer may be 0.5 to 50% of the radius of the carbon support.

[0024] Additionally, the silicon layer may be 10 to 80 wt% of the total weight of the carbon-silicon composite.

[0025]

[0026] In addition, the present invention provides a negative electrode active material comprising the above-described carbon-silicon composite.

[0027]

[0028] In addition, the present invention provides an all-solid-state battery comprising the above-described carbon-silicon composite.

[0029] The carbon-silicon composite according to an embodiment of the present invention may have excellent electrochemical performance because it includes a film-shaped silicon layer on the surface and inside the pores of the porous carbon support.

[0030] In addition, the manufacturing method according to the embodiment of the present invention can easily manufacture a carbon-silicon composite having the above characteristics.

[0031] Figure 1 is a cross-sectional schematic diagram of a carbon-silicon composite according to one embodiment of the present invention.

[0032] Figure 2 is a surface SEM image of Example 1 of the present invention.

[0033] Figure 3 is a surface SEM image of Comparative Example 2 of the present invention.

[0034] Figure 4 is a cross-sectional SEM image of Example 1 of the present invention.

[0035] Figure 5 is a cross-sectional SEM image of Comparative Example 2 of the present invention.

[0036] The present invention is not limited to the contents disclosed below, and may be modified in various forms as long as the gist of the invention is not changed.

[0037] As used herein, the term “comprising” means that other components may be included unless otherwise stated.

[0038] All numbers and expressions indicating the amounts of components, reaction conditions, etc. described in this specification are to be understood as being modified in all cases by the term “about” unless otherwise stated.

[0039] The present invention will be described in more detail below.

[0040] carbon-silicon composites

[0041] As illustrated in FIG. 1, the carbon-silicon composite (100) according to the present invention is implemented by including a carbon support (10) and a film-shaped silicon layer (20) disposed including the surface of the carbon support (10).

[0042] Meanwhile, the carbon-silicon composite may have a BET surface area of ​​200 m2 / g or less, preferably 100 m2 / g or less, and more preferably 55 m2 / g or less. If the BET surface area of ​​the carbon-silicon composite exceeds 200 m2 / g, a large number of SEI layers may be formed due to the reaction with the electrolyte due to the high BET, resulting in poor electrochemical performance.

[0043] Hereinafter, each component of a carbon-silicon composite (100) according to one embodiment of the present invention will be described.

[0044] carbon support

[0045] A carbon-silicon composite (100) according to an embodiment of the present invention includes a carbon support (10).

[0046] The above carbon support may be used without limitation as long as it is a carbon support that can be commonly used in the art, but preferably, at least one of a non-porous carbon support and a porous carbon support may be used, and more preferably, at least one of graphite, hard carbon, soft carbon, and porous carbon support may be used, and even more preferably, using at least one of hard carbon, soft carbon, and porous carbon support may be more advantageous in achieving the purpose of the present invention.

[0047] According to one embodiment of the present invention, the carbon support may be a porous carbon support, and in this case, the silicon layer may be disposed on the surface and inside the pores of the porous carbon support.

[0048] The porous carbon support (10) may have a volume ratio of mesopores having a pore size of 2 to 50 nm based on the total pore volume of 10 to 80%, preferably 30 to 60%, and more preferably 40 to 50%. If the volume ratio of the mesopores of the porous carbon support is less than 10%, the number of micropores may be too large, so that a silicon layer may be formed relatively in large amounts on the outside of the particles, and if the volume ratio of the mesopores of the porous carbon support exceeds 80%, the hardness of the particles is insufficient, so that when an electrode is manufactured using the same, there is a concern that the structure of the electrode may collapse.

[0049] In addition, the porous carbon support (10) may have a BET specific surface area of ​​300 to 3,000 m2 / g. Preferably, the porous carbon support (10) may have a BET specific surface area of ​​300 to 1,500 m2 / g, more preferably, a BET specific surface area of ​​500 to 1,500 m2 / g. When the BET specific surface area of ​​the porous carbon support is less than 300 m2 / g, there may be too many macropores and thus insufficient effective pores, and when the BET specific surface area of ​​the porous carbon support exceeds 3,000 m2 / g, there may be too many micropores and thus a relatively large silicon layer may be deposited on the outside of the particles.

[0050] In addition, the porous carbon support (10) may have a tap density of 0.05 to 0.5 g / ml. Preferably, the porous carbon support (10) may have a tap density of 0.05 to 0.45 g / ml, more preferably, a tap density of 0.1 to 0.453 g / ml. When the tap density of the porous carbon support is less than 0.05 g / ml, process control may be difficult during silicon layer formation, resulting in a decrease in yield. When the tap density of the porous carbon support exceeds 0.5 g / ml, uniform layer formation may be difficult during silicon layer formation.

[0051] And, the carbon support (10) may have a particle size distribution D50 of 2 to 15 ㎛. Preferably, the carbon support (10) may have a particle size distribution D50 of 3 to 10 ㎛. When the particle size distribution D50 of the porous carbon support is less than 2 ㎛, the silicon layer is not sufficiently formed within the pores and is formed relatively more only on the outside of the particles, and when the particle size distribution D50 of the porous carbon support exceeds 15 ㎛, it is difficult for the silicon layer to be sufficiently formed within the pores.

[0052] In addition, the carbon support (10) may have a particle size distribution Dmax of 25 ㎛ or less, and preferably 20 ㎛ or less. If the particle size distribution Dmax of the carbon support exceeds 25 ㎛, there may be a problem of coating with an uneven thickness when coating the negative electrode plate.

[0053] When a carbon-silicon composite (100) according to an embodiment of the present invention includes a porous carbon support (10) having the above characteristics, when such a carbon-silicon composite (100) is used as a negative electrode active material, it has excellent electrical conductivity and can relieve stress due to volume expansion of silicon.

[0054]

[0055] Silicon layer on film

[0056] A carbon-silicon composite (100) according to an embodiment of the present invention includes a silicon layer (20) on a film disposed including the surface of the carbon support (10).

[0057] In a specific example of the present invention, as described below, a silicon source is applied to a porous carbon support (10) by chemical vapor deposition (CVD), thereby forming a film-shaped silicon layer (20) including the surface of the carbon support (10), thereby obtaining a carbon-silicon composite (100).

[0058] Meanwhile, the silicon included in the silicon layer (20) may be crystalline or amorphous, and preferably, may be amorphous or a similar phase. When the silicon is crystalline, the smaller the crystallite size, the more dense the composite can be obtained, and thus the initial efficiency or cycle life characteristics of the secondary battery can be improved.

[0059] In a specific embodiment of the present invention, the silicon disposed including the surface of the carbon support may be crystalline silicon, and at this time, the size of the silicon crystals may be on the nanoscale. Specifically, the average crystal size of the crystalline silicon may be 10 nm or less, and preferably, 8 nm or less, 5 nm or less, 3 nm or less, or 2 nm or less. When the average crystal size of the crystalline silicon satisfies the above range, the size of the stress due to the volume expansion of the silicon is reduced, so that the life characteristics of the negative electrode active material can be improved.

[0060] In addition, the average thickness of the silicon layer (20) may be 0.5 to 50% of the radius of the carbon support. If the average thickness of the silicon layer is less than 0.5% of the radius of the carbon support, the electric capacity may be reduced, and if the average thickness exceeds 50% of the radius of the carbon support, the problem caused by the volume expansion of silicon may not be resolved, which may cause structural damage to the negative electrode material and deteriorate the cycle characteristics.

[0061] Meanwhile, the silicon layer may be 10 to 80 wt% of the total weight of the carbon-silicon composite according to the present invention, and preferably 10 to 50 wt%. If the silicon layer is less than 5 wt% of the total weight of the carbon-silicon composite, the electric capacity may decrease, and if the silicon layer is more than 80 wt%, the problem caused by volume expansion of silicon during charge and discharge may not be solved, which may cause structural damage to the negative electrode material and deteriorate the cycle characteristics.

[0062] Meanwhile, the silicon layer (20) may further include a silicon oxide compound. The silicon oxide compound has the general formula SiO x It can be expressed as (0.5≤x≤2). Here, when the value of x is less than 0.5, expansion and contraction may increase and the life characteristics may deteriorate during charging and discharging of the secondary battery, and when x exceeds 2, the initial efficiency of the secondary battery may decrease as the amount of inactive oxide increases.

[0063] The content of the silicon oxide compound in the silicon included in the silicon layer (20) may be 50 wt% or less based on the total weight of the silicon. If the content of the silicon oxide compound in the silicon exceeds 50 wt%, the initial efficiency of the secondary battery may be reduced.

[0064]

[0065] Method for manufacturing carbon-silicon composites

[0066] A carbon-silicon composite (100) according to one embodiment of the present invention is manufactured by a manufacturing method including a step of manufacturing the carbon-silicon composite (100) by forming a film-shaped silicon layer (20) including the surface of a carbon support (10).

[0067] Hereinafter, in the description of the method for manufacturing the carbon-silicon composite, the same content as the description of the carbon-silicon composite described above will be omitted and described.

[0068] As described above, the carbon support may be any carbon support commonly used in the art without limitation, but preferably, at least one of a non-porous carbon support and a porous carbon support may be used, more preferably, at least one of graphite, hard carbon, soft carbon, and porous carbon support may be used, and even more preferably, using at least one of hard carbon, soft carbon, and porous carbon support may be more advantageous in achieving the purpose of the present invention.

[0069] When the carbon support is a porous carbon support, the porous carbon support can be manufactured by performing the steps of (1) synthesizing pitch by thermal decomposition and condensation polymerization of a petroleum-based raw material, (2) solidifying and pelletizing the pitch to obtain a pellet-like pitch or solidifying, pelletizing, and pulverizing the pitch to obtain a powder-like pitch, and (3) stabilizing the pellet-like pitch or the powder-like pitch, (4) carbonizing the stabilized pitch to obtain a carbonized body, and (5) activating the carbonized body to obtain a porous carbon support.

[0070] In the above step (1), pitch can be synthesized by thermal decomposition and polycondensation of petroleum-based raw materials.

[0071] In a specific embodiment of the present invention, the petroleum-based raw material may include at least one selected from the group consisting of pyrolysis fuel oil (PFO), naphtha cracking residue (NCB), ethylene cracker bottom oil (EBO), vacuum residue (VR), de-asphalted oil (DAO), atmospheric residue (AR), fluid catalytic cracking (FCC-DO) oil, residue fluid catalytic cracking decant oil (RFCC-DO), and heavy aromatic oil. In a preferred specific embodiment of the present invention, the petroleum-based raw material may include pyrolysis fuel oil.

[0072] In a specific embodiment of the present invention, the petroleum-based raw material may contain an aromatic compound in an amount of 10 to 90 wt%. Preferably, the petroleum-based raw material may contain an aromatic compound in an amount of 20 to 80 wt%, more preferably 30 to 70 wt%. When the content of the aromatic compound in the petroleum-based raw material satisfies the above range, even if the solid pitch pellets described below are stabilized, carbonized, and activated without separately pulverizing, a porous carbon support having controlled pore characteristics can be obtained.

[0073] In a specific embodiment of the present invention, the aromatic compound may be a compound having 1 to 4 aromatic rings. Specifically, the aromatic compound may include at least one selected from the group consisting of substituted or unsubstituted benzene, naphthalene, phenanthrene, indene, biphenyl, anthracene, tetralin, and fluorene. In this case, even if the solid pitch pellets described below are stabilized, carbonized, and activated without separately pulverizing, a porous carbon support having controlled pore characteristics can be obtained.

[0074] In a specific embodiment of the present invention, the thermal decomposition and polycondensation of the petroleum-based raw material can be carried out at a temperature of 350 to 500°C. In a preferred specific embodiment of the present invention, the thermal decomposition and polycondensation of the petroleum-based raw material can be carried out at a temperature of 400 to 500°C. In a more preferred specific embodiment of the present invention, the thermal decomposition and polycondensation of the petroleum-based raw material can be carried out at a temperature of 430 to 470°C. When the temperature of the thermal decomposition and polycondensation of the petroleum-based raw material is 350 to 500°C, a pitch containing a large amount of relatively low molecular weight components can be produced, and in the activation process of step (5) described below, components having relatively small molecular weights are vaporized first, thereby sufficiently forming mesopores in the carbon support. If the thermal decomposition and polycondensation temperature of petroleum-based raw materials is less than 350°C, it is difficult to manufacture pitch that is solid at room temperature, and if this temperature exceeds 500°C, the pitch contains a lot of relatively high molecular weight components, making it difficult to manufacture a carbon support having mesopores.

[0075] In a specific embodiment of the present invention, the thermal decomposition and polycondensation of the petroleum raw material may be performed under an atmosphere of an oxidizing gas, an inert gas, or a mixture thereof. In a preferred specific embodiment of the present invention, the oxidizing gas may be oxygen, ozone, or a combination thereof, the inert gas may be nitrogen, helium, neon, argon, or a combination thereof, and the mixture thereof may be air, but is not particularly limited thereto.

[0076] When an oxidizing gas is used during the thermal decomposition and polycondensation of petroleum-based raw materials, a pitch with a high softening point can be produced, but it is difficult to perform the thermal decomposition and polycondensation at high temperatures. When an inert gas is used during the thermal decomposition and polycondensation of petroleum-based raw materials, thermal decomposition and polycondensation can be performed at high temperatures, but it is difficult to produce a pitch with a relatively high softening point. When a mixed gas of an oxidizing gas and an inert gas is used during the thermal decomposition and polycondensation of petroleum-based raw materials, thermal decomposition and polycondensation can be performed at relatively high temperatures, thereby producing a pitch with a relatively high softening point.

[0077] In a specific embodiment of the present invention, the gas may be supplied at a flow rate of 10 to 800 ml / min during the thermal decomposition and polycondensation of a petroleum-based raw material. In a preferred specific embodiment of the present invention, the gas may be supplied at a flow rate of 100 to 500 ml / min during the thermal decomposition and polycondensation of a petroleum-based raw material. When the flow rate of the gas is less than 10 ml / min, the yield of the pitch increases, but the low molecular weight component increases too much, which is disadvantageous for subsequent processes (e.g., stabilization). When the flow rate of the gas exceeds 800 ml / min, the yield of the pitch may decrease.

[0078] In a specific embodiment of the present invention, the thermal decomposition and polycondensation of the petroleum-based raw material can be carried out for 1 to 10 hours. In a preferred embodiment of the present invention, the thermal decomposition and polycondensation of the petroleum-based raw material can be carried out for 2 to 8 hours. In a more preferred embodiment of the present invention, the thermal decomposition and polycondensation of the petroleum-based raw material can be carried out for 2 to 7 hours. If the thermal decomposition and polycondensation time of the petroleum-based raw material is less than 1 hour, it is difficult to produce a pitch having a high softening point, and if the thermal decomposition and polycondensation time of the petroleum-based raw material exceeds 10 hours, an excessive amount of quinoline-insoluble components may be produced.

[0079] In a specific embodiment of the present invention, the thermal decomposition and polycondensation of the petroleum-based raw material may be performed under stirring. The stirring conditions for the petroleum-based raw material are not particularly limited, but, for example, a stirrer rotating at 10 to 500 rpm may be used.

[0080] In a specific embodiment of the present invention, the pitch synthesized in step (1) may have a softening point of 200 to 350°C. In a preferred embodiment of the present invention, the pitch may have a softening point of 200 to 330°C. In a more preferred embodiment of the present invention, the pitch may have a softening point of 200 to 300°C. Since the pitch manufactured according to the present invention has a high softening point, when used as a precursor for manufacturing a carbon support, the stabilization process is easy, and a high yield can be obtained after carbonization and activation.

[0081] In a specific embodiment of the present invention, the yield of the pitch synthesized in step (1) may be 10 to 50 wt%. In a preferred embodiment of the present invention, the yield of the pitch may be 10 to 40 wt%. In a more preferred embodiment of the present invention, the yield of the pitch may be 20 to 30 wt%.

[0082] In a specific embodiment of the present invention, a step of pretreating the petroleum-based raw material may be performed prior to step (1) above. By removing low-boiling-point components contained in the petroleum-based raw material through the pretreating step, a pitch having a higher softening point can be produced.

[0083] In a specific embodiment of the present invention, the pretreatment step may be performed at a temperature equal to or lower than the thermal decomposition and polycondensation temperature of the petroleum-based raw material in step (1), but is not particularly limited to this condition. Specifically, the pretreatment step may be performed at 250 to 450°C, preferably 250 to 400°C, and more preferably 300 to 400°C.

[0084] In a specific embodiment of the present invention, the pretreatment step may be performed for a time equal to or shorter than the thermal decomposition and polycondensation time of the petroleum-based raw material in step (1), but is not particularly limited to this condition. Specifically, the pretreatment step may be performed for 1 to 8 hours, preferably 1 to 6 hours, and more preferably 1 to 5 hours.

[0085] In addition, in the step (2), the pitch can be solidified and pelletized to obtain a pellet-like pitch, or the pitch can be solidified, pelletized, and pulverized to obtain a powder-like pitch.

[0086] First, in the case of the pellet-shaped pitch, the liquid pitch obtained in step (1) is solidified, for example, by extrusion and cooling, and then pelletized into a desired size to obtain a solid pitch pellet (pellet-shaped pitch). The process of extruding, cooling, and pelletizing the liquid pitch to obtain a solid pitch pellet can be performed using commercially available equipment. For example, this process can be performed using IPCO's Double Belt Cooler & Flaker, but is not particularly limited to this equipment.

[0087] (2) The pitch pellets obtained in step (2) have an average particle size (particle size distribution D50) of 1 to 30 mm, preferably 5 to 25 mm. When the average particle size (particle size distribution D50) of the pitch pellets is within this range, a porous carbon support can be manufactured through stabilization, carbonization, and activation described below without separately pulverizing the pitch pellets.

[0088] In addition, in the case of the above-mentioned powdered pitch, the pitch pellets (pellet-shaped pitch) can be further crushed or pulverized and classified. The pitch pellets can be further finely divided through crushing or pulverization, and the particle size distribution of the pitch pellets can be made uniform through classification. Here, the classification can be dry classification, wet classification, or classification using a sieve. By crushing or pulverizing and classification, a powdered pitch having an average particle size (particle size distribution D50) of 50 to 500 μm can be obtained.

[0089] And, in step (3), a step of stabilizing the pellet-shaped pitch or powder-shaped pitch can be performed.

[0090] First, the pitch obtained in step (2) is subjected to primary oxidation to stabilize the carbon structure of the pitch.

[0091] In a specific embodiment of the present invention, the stabilization of the pitch may be performed in an oxidizing gas atmosphere. In a preferred embodiment of the present invention, the stabilization of the pitch may be performed in an air atmosphere, but is not particularly limited thereto.

[0092] In a specific embodiment of the present invention, the stabilization of the pitch may be performed at a temperature of 100 to 500°C, preferably 150 to 300°C. When the stabilization of the pitch is performed at this temperature, the carbon structure within the pellet-shaped pitch or powder-shaped pitch changes from thermoplastic to thermosetting, so that the structure can be stably maintained during the subsequent carbonization process. At this time, the heating rate may be 2 to 10°C / min. If the heating rate is too slow, productivity may be poor, and if the heating rate is excessively fast, uniform stabilization treatment may be difficult.

[0093] In a specific embodiment of the present invention, the stabilization may be performed at a pressure of 0.1 to 10 bar, preferably 0.5 to 5 bar. When the stabilization is performed at this pressure, the structure of the carbon inside the pellet-shaped pitch or the powder-shaped pitch can be sufficiently stabilized.

[0094] In a specific embodiment of the present invention, the stabilization can be performed under conditions of a flow rate of an oxidizing gas, preferably air, of 0.1 to 500 ml / min, preferably 1 to 300 ml / min. When the stabilization is performed under these oxidizing gas flow rates, the structure of the carbon inside the pellet-shaped pitch or the powder-shaped pitch can be sufficiently stabilized.

[0095] In a specific embodiment of the present invention, the stabilization may be performed for 1 to 10 hours, preferably 2 to 8 hours. If the stabilization is performed for this period of time, the structure of the carbon within the pellet-shaped pitch or the powder-shaped pitch can be sufficiently stabilized.

[0096] And, in step (4), the stabilized pitch can be carbonized to obtain a carbonized body. Through carbonization of the stabilized pitch, other functional groups contained in the pitch are removed, and a carbonized body composed of substantially pure carbon can be obtained.

[0097] In a specific embodiment of the present invention, the carbonization may be performed under an inert gas atmosphere. In a preferred embodiment of the present invention, the carbonization may be performed under a nitrogen or argon atmosphere, but is not particularly limited thereto.

[0098] In a specific embodiment of the present invention, the carbonization may be performed at a temperature of more than 700°C and less than or equal to 1,000°C, preferably 800 to 900°C. If the temperature during carbonization is lower than this range, carbonization may not be sufficiently achieved, and if the temperature during carbonization of the stabilized pitch is higher than this range, the carbonization yield may decrease.

[0099] In a specific embodiment of the present invention, the carbonization may be performed under conditions of a flow rate of an inert gas, preferably nitrogen, of 0.1 to 30 ml / min, preferably 0.1 to 10 ml / min. When the carbonization is performed under these inert gas flow rates, the stabilized pitch can be sufficiently carbonized.

[0100] In a specific embodiment of the present invention, carbonization of the pitch may be performed for 0.5 to 5 hours, preferably 1 to 3 hours. If carbonization of the pitch pellet is performed for this period of time, the pitch can be sufficiently carbonized.

[0101] And, in step (5), the carbonized body (carbonized pitch) is activated to obtain a porous carbon support. By activating the carbonized body, pores are formed in the pitch pellets, thereby obtaining a porous carbon support.

[0102] In a specific embodiment of the present invention, the activation of the carbonized body may be performed in an oxidizing gas atmosphere. In a preferred embodiment of the present invention, the activation of the carbonized body may be performed in a steam atmosphere, but is not particularly limited thereto.

[0103] In a specific example of the present invention, the activation of the carbonized body can be performed at a temperature of more than 700°C and less than or equal to 1,000°C, preferably 800 to 900°C. When the activation of the carbonized body is performed at this temperature, a porous carbon support in which micropores and mesopores are sufficiently formed can be obtained.

[0104] In a specific embodiment of the present invention, the activation of the carbonized body can be performed at a pressure of 0.1 to 10 bar, preferably 0.1 to 5 bar. When the activation of the carbonized body is performed at this pressure, a porous carbon support in which micropores and mesopores are sufficiently formed can be obtained.

[0105] In a specific embodiment of the present invention, the activation of the carbonized body can be performed under conditions of a flow rate of an oxidizing gas, preferably water vapor, of 0.1 to 100 ml / min, preferably 0.1 to 50 ml / min. When the activation of the carbonized body is performed under these oxidizing gas flow rates, a porous carbon support in which micropores and mesopores are sufficiently formed can be obtained.

[0106] In a specific embodiment of the present invention, the activation of the carbonized body may be performed for 0.5 to 5 hours, preferably 1 to 3 hours. When the activation of the carbonized body is performed for this period of time, a porous carbon support in which micropores and mesopores are sufficiently formed can be obtained.

[0107] In a specific embodiment of the present invention, the stabilization, carbonization, and activation of steps (3) to (5) above can each be performed in a heating furnace using microwaves. In a preferred specific embodiment of the present invention, the stabilization, carbonization, and activation of steps (3) to (5) above can all be performed in a heating furnace using microwaves. A heating furnace using microwaves is preferred because it can increase the temperature of the pitch itself without increasing the external temperature of the pitch, but is not particularly limited thereto.

[0108] In a specific embodiment of the present invention, the stabilization, carbonization, and activation of steps (3) to (5) above can be performed continuously in one device. In a preferred embodiment of the present invention, the stabilization, carbonization, and activation of steps (3) to (5) above can be performed continuously in one rotary kiln, but the device is not particularly limited thereto. By performing the stabilization, carbonization, and activation of steps (3) to (5) above continuously in one device, process optimization can be achieved.

[0109] In a specific embodiment of the present invention, the porous carbon support obtained in step (5) can be further pulverized or ground and classified. The porous carbon support can be further finely divided through pulverization or grounding, and the particle size distribution of the porous carbon support can be made uniform through classification. Here, the classification can be dry classification, wet classification, classification using a sieve, etc. By the pulverization or grounding and classification treatment, a porous carbon support powder having a particle size distribution D50 of 2 to 15 ㎛, a BET specific surface area of ​​300 to 3,000 m2 / g, and a tap density of 0.05 to 0.5 g / ㎖ can be obtained. In addition, the porous carbon support powder can have a volume ratio of mesopores having a pore size of 2 to 50 nm based on the total pore volume of 10 to 80%.

[0110] Meanwhile, in the case where the porous carbon support is obtained by stabilizing, carbonizing, and activating the pitch without further pulverizing in the above step (2), the carbon support may be pulverized (or further classified) to have a particle size distribution D50 of 2 to 15 ㎛, but is not limited thereto.

[0111]

[0112] In addition, when the carbon support is hard carbon, the hard carbon can be manufactured by a method including the steps of (1') synthesizing pitch by thermal decomposition and condensation polymerization of petroleum-based raw materials, (2') solidifying and pelletizing the pitch to obtain pellet-like pitch, or solidifying, pelletizing, and pulverizing the pitch to obtain powder-like pitch, (3') stabilizing the pellet-like pitch or powder-like pitch, and (4') carbonizing the stabilized pitch to obtain hard carbon.

[0113] At this time, since the description of the above steps (1') to (4') may be the same as the description of the above steps (1) to (4), a detailed description will be omitted.

[0114] Meanwhile, the pitch for manufacturing the hard carbon may be at least one of an isotropic pitch and an anisotropic pitch, and it is more advantageous to achieve the purpose of the present invention to be an isotropic pitch.

[0115]

[0116] In addition, when the carbon support is soft carbon, the soft carbon can be manufactured by a method including the steps of (1) synthesizing pitch by thermal decomposition and condensation polymerization of petroleum-based raw materials, (2) solidifying and pelletizing the pitch to obtain pellet-like pitch, or solidifying, pelletizing, and pulverizing the pitch to obtain powder-like pitch, (3) stabilizing the pellet-like pitch or powder-like pitch, and (4) carbonizing the stabilized pitch to obtain soft carbon.

[0117] At this time, the description of the above steps (1”) and (2”) may be the same as the description of the above steps (1) and (2), so a detailed description will be omitted.

[0118] The above step (3”) and the step (4”) described below may be performed as a series of steps in a rotary kiln, as in the above-described steps (3) and (4), or may be performed as a series of steps by placing the material in a crucible and placing it in an oven. Preferably, it may be advantageous to achieve the purpose of the present invention to perform the series of steps by placing the material in a crucible and placing it in an oven.

[0119] Meanwhile, since the description of the contents other than the above step (3”) may be the same as the description of the above step (3), a detailed description will be omitted.

[0120] In addition, the above step (4”) is a step of carbonizing the stabilized pitch to obtain soft carbon, and through carbonization of the stabilized pitch, other functional groups included in the pitch are removed, and soft carbon composed of substantially pure carbon can be obtained.

[0121] In a specific embodiment of the present invention, the carbonization in step (4”) may be performed under an inert gas atmosphere. In a preferred specific embodiment of the present invention, the carbonization in step (4”) may be performed under a nitrogen or argon atmosphere, but is not particularly limited thereto.

[0122] In a specific example of the present invention, the carbonization in step (4”) may be performed at a temperature of 1,000°C to 2,700°C, preferably 1,200°C to 2,200°C. If the temperature during the carbonization in step (4”) is lower than this range, carbonization may not be sufficiently performed, and if the temperature during the carbonization is higher than this range, the carbonization yield may decrease.

[0123] In a specific embodiment of the present invention, the carbonization in step (4”) can be performed under a flow condition of an inert gas, preferably argon, of 0.1 to 30 ml / min, preferably 0.1 to 10 ml / min. When the carbonization is performed under this inert gas flow condition, the stabilized pitch can be sufficiently carbonized.

[0124] In a specific example of the present invention, the carbonization in step (4”) can be performed for 0.5 to 5 hours, preferably 1 to 3 hours. When the carbonization in step (4”) is performed for this period of time, the stabilized pitch can be sufficiently carbonized.

[0125] Meanwhile, since the description of the contents other than the above step (4”) may be the same as the description of the above step (d), a detailed description will be omitted.

[0126] Meanwhile, the pitch for manufacturing the soft carbon may be at least one of an isotropic pitch and an anisotropic pitch, and preferably, an anisotropic pitch may be more advantageous in achieving the purpose of the present invention.

[0127]

[0128] Hereinafter, the steps for manufacturing the carbon-silicon composite will be described.

[0129] As described above, the carbon-silicon composite (100) is manufactured by forming a film-shaped silicon layer (20) including the surface of the carbon support (10).

[0130] At this time, the formation of the film-shaped silicon layer (20) can be accomplished by supplying a silicon source to the carbon support (10) and performing CVD to form a film-shaped silicon layer (20) including the surface of the carbon support.

[0131] In a specific embodiment of the present invention, the silicon source may include at least one selected from silane (SiH4), dichlorosilane (SiH2Cl2), silicon tetrafluoride (SiF4), silicon tetrachloride (SiCl4), methylsilane (CH3SiH3), and disilane (Si2H6), but is not particularly limited thereto.

[0132] The silicon source may include at least one selected from silane (SiH4), dichlorosilane (SiH2Cl2), silicon tetrafluoride (SiF4), silicon tetrachloride (SiCl4), methylsilane (CH3SiH3), and disilane (Si2H6), but is not particularly limited thereto.

[0133] The supply flow rate of the silicon source may be 50 to 300 sccm per 10 g of the carbon support, preferably 60 to 280 sccm per 10 g of the carbon support, more preferably 70 to 250 sccm per 10 g of the carbon support, and even more preferably 70 to 200 sccm per 10 g of the carbon support. If the supply flow rate of the silicon source is less than 50 sccm per 10 g of the carbon support, silicon deposition may not occur smoothly, resulting in a problem of partial coating rather than a silicon layer or silicon deposition not occurring. In addition, if the supply flow rate exceeds 300 sccm per 10 g of the carbon support, it is difficult to form a film-shaped silicon layer, and thus, silicon in the form of particles may be formed, resulting in a decrease in initial efficiency and cycle maintenance rate.

[0134] In addition, the chemical vapor deposition can be performed for 40 to 120 minutes, preferably for 50 to 115 minutes, and more preferably for 55 to 110 minutes. If the chemical vapor deposition time is less than 40 minutes, it is difficult to form a film-shaped silicon layer, and thus, silicon in the form of particles may be formed, which may lower the initial efficiency and cycle maintenance rate. In addition, if the chemical vapor deposition time exceeds 120 minutes, large silicon particles may be formed due to excessive silicon deposition, which may cause a problem of lowering the initial efficiency and cycle maintenance rate.

[0135] In particular, when the supply flow rate of the silicon source is increased for rapid deposition and the time of chemical vapor deposition is reduced, the formation of a film-shaped silicon layer becomes more difficult, and thus, the initial efficiency and cycle maintenance rate may be reduced as silicon in the particle form is formed.

[0136] The CVD of the above silicon source can be performed at a temperature of 300 to 700°C. For example, the CVD of the silicon source can be performed at a temperature of 400 to 600°C, 400 to 500°C, or 400 to 450°C, but is not particularly limited to this range.

[0137]

[0138] Negative active material

[0139] According to another embodiment of the present invention, a negative active material comprising the carbon-silicon composite is provided.

[0140] The negative active material according to an embodiment of the present invention may include a carbon-silicon composite.

[0141] Additionally, the negative electrode active material according to an embodiment of the present invention may further include a carbon-based negative electrode material, specifically a graphite-based negative electrode material, in addition to the carbon-silicon composite. For example, the negative electrode active material may be obtained by mixing the carbon-silicon composite according to an embodiment of the present invention with a carbon-based negative electrode material, such as a graphite-based negative electrode material.

[0142] Here, the carbon-based negative electrode material may include, but is not particularly limited to, at least one selected from the group consisting of natural graphite, artificial graphite, soft carbon, hard carbon, mesocarbon, carbon fiber, carbon nanotube, pyrolytic carbon, coke, organic polymer compound sintered body, and carbon black.

[0143] The content of the carbon-based negative electrode material in the negative electrode active material according to an embodiment of the present invention may be 2 to 80 wt%, preferably 5 to 70 wt%, and more preferably 30 to 70 wt%, based on the total weight of the negative electrode active material.

[0144] The negative active material according to an embodiment of the present invention can be effectively used in manufacturing a secondary battery, specifically, a negative electrode of a lithium secondary battery and a negative electrode of an all-solid-state battery.

[0145]

[0146] All-solid-state batteries

[0147] According to another embodiment of the present invention, an all-solid-state battery comprising the carbon-silicon composite is provided.

[0148] The above-described all-solid-state battery may be an all-solid-state battery including a positive electrode, a negative electrode, and a solid electrolyte between the positive electrode and the negative electrode, and the negative electrode may include a negative electrode active material layer, and may include the carbon-silicon composite described above at least in part.

[0149] Meanwhile, the above-described negative electrode active material particles may be carbon-based negative electrode materials, and in this case, since the content may be the same as that described in the content of the above-described negative electrode active material, the related description will be omitted.

[0150] In addition, since the configuration of the cathode, anode, and solid electrolyte of the above-mentioned all-solid-state battery can be applied to the configuration of a known all-solid-state battery, the present invention does not specifically limit it.

[0151]

[0152] The present invention is described in more detail by the following examples. The following examples are merely illustrative of the present invention and are not intended to limit the scope of the present invention.

[0153] [Example]

[0154] <Example 1>

[0155] 300 g of petroleum residual oil (YNCC, HTC PFO (pyrolysis fuel oil)) was placed in a reactor equipped with a stirrer, and pyrolysis and polycondensation were performed at 450°C for 3 hours while supplying nitrogen at a flow rate of 100 ml / min. During this time, the stirrer was rotated at a speed of 200 rpm to mix the reactants. The polymerized pitch was solidified and pelletized to obtain solid pitch pellets with an average particle size (particle size distribution D50) of 1–30 mm.

[0156] The solid pitch pellets obtained above were pulverized to produce pitch particles with an average particle size (particle size distribution D50) of 200 μm, and then placed in a rotary kiln with three zones to sequentially perform stabilization, carbonization, and activation. The conditions for stabilization, carbonization, and activation are as shown in Table 1 below.

[0157] The specific surface area of ​​the carbon support was measured using a Belsorp mini II according to ASTM D4820-93. The tap density of the carbon support was measured using a tap density analyzer (Electrolab, ETD-1020x) according to ASTM B527. The particle size distribution of the carbon support was measured using a particle size analyzer (Horiba, Laser Particle Analyzer, LA-960V2) according to ASTM E112. The results are shown in Table 1.

[0158] Step Condition Standard Example Stabilization temperature (℃) 300 hours (hr) 3 Atmospheric air Carbonization temperature (℃) 900 hours (hr) 1 Atmospheric nitrogen Activation temperature (℃) 900 hours (hr) 3 Water vapor flow rate (㎖ / min) 200 Support physical properties Particle size distribution Dmax (㎛) 200 Particle size distribution D50 (㎛) 75 Specific surface area (㎡ / g) 1409.1 Tap density (g / ㎖) 0.44

[0159] A carbon support of the reference example was pulverized with a pulverizer (NETZSCH, air jet mill) to obtain a porous carbon support having a particle size distribution D50 of 5.6 ㎛. Next, 15 g of the fine powder of this porous carbon support was placed in a rotary kiln, and silane (SiH4) gas was injected to perform chemical vapor deposition (CVD) to form a film-like silicon layer on the surface and inside the pores of the porous carbon support, thereby producing a carbon-silicon composite.

[0160] The silicon layer formation conditions are shown in Table 3 below.

[0161]

[0162] <Example 2 and Comparative Examples 1 to 4>

[0163] The same procedure as Example 1 was followed, but the silane gas flow rate and deposition time were changed to produce a carbon-silicon composite as shown in Table 3 below.

[0164]

[0165] <Experimental Example 1: Electrochemical Evaluation>

[0166] Half coin cells were manufactured using each carbon-silicon composite according to the examples and comparative examples.

[0167] Carbon-silicon composite: Conductive material: Binder was mixed in a ratio of 8:1:1 to prepare a slurry. At this time, the conductive material used was super-P, and the binder used was a mixture of styrene butadiene rubber (SBR) and sodium carboxymethyl cellulose (CMC) in a weight ratio of 5:5.

[0168] Next, the slurry was uniformly applied to copper foil and dried in an 80°C oven for 1 hour. After the primary drying, the slurry was roll-pressed and dried in a 120°C vacuum oven for 6 hours and 30 minutes to manufacture a negative electrode plate.

[0169] A half coin cell was manufactured using the above-mentioned negative electrode and lithium foil as a counter electrode. A porous polyethylene film was used as a separator, and a CR2032 half coin cell (half cell) was manufactured under the conditions shown in Table 2 below.

[0170] The electrolyte was prepared by dissolving 1.3 M LiPF6 in a solvent containing ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) in a volume ratio of 3:5:2, and dissolving 10 wt% fluoro-ethylene carbonate (FEC), 0.2 wt% lithium tetrafluoroborate (LiBF4), 0.5 wt% vinylene carbonate (VC), and 1 wt% propane sulton (PS) additives (see Table 2).

[0171] Composition (AM:CM:BM) 8:1:1 Area capacity (mAh / cm 2 )1 Electrolyte 1.3M LiPF6 EC / EMC / DMC 3:5:2, FEC 10%, LiBF4 0.2%, 0.5% VC, 1% PS Cut-off voltage (V) Formation: 0.005 ~ 1.5, Cycle test: 0.005 ~ 1.5 C-rate (C) Formation: 0.1 ~ 0.1. 0.01 C cut-off (CV) at 0.005 V

[0172] In Table 2 above, AM, CM, and BM represent active material (carbon-silicon composite), conductor (Super P carbon black), and binder (styrene-butadiene rubber / carboxymethyl cellulose 5:5), respectively, and EC, EMC, DMC, FEC, VC, and PS represent ethylene carbonate, ethyl methyl carbonate, dimethyl carbonate, fluoroethylene carbonate, vinylene carbonate, and propane sultone, respectively.

[0173] Electrochemical analysis was performed on the manufactured half coin cell under the following conditions.

[0174] Cut off voltage (V): 0.005 - 1.5V (Formation), 0.005 - 1.2V(Cycle)

[0175] Formation C-rate (C): 0.1C lithiation, 0.1C delithiation

[0176] Cycle C-rate (C): 0.5C lithiation, 0.5C delithiation

[0177] Additionally, the cycle maintenance rate was measured after 50 cycles of operation.

[0178] The electrochemical evaluation results are shown in Table 3 below.

[0179] ClassificationExample 1Example 2Comparative Example 1Comparative Example 2Comparative Example 3Comparative Example 4Silicone layer formation conditionsBatch (g)15PressureAtmospheric pressureTemperature (℃)475Silane flow rate per 10g of carbon support (sccm)120180360500300600Time (min)1006733241060Silicon content (wt%)47.044.244.042.59.661.0Particle size (D50, ㎛)6.67.07.66.25.66.1Specific surface area (m 2 / g)51.853.6296.1493.5890.6218.4Silicon deposition layer thickness (nm)12672--11-Ratio of the thickness of the silicon layer to the radius of the carbon support (%)3.822.06--0.39-Electrochemical evaluation charge capacity (mAh / g)19391958200020901045Evaluation non-discharge capacity (mAh / g)1751171316041643418Initial efficiency (%)90.387.580.278.640.0Cycle retention rate (%)62.554.040.221.751.2

[0180] As can be seen from Table 3 above, it was confirmed that Examples 1 and 2, which satisfy the silicon supply source supply flow rate and deposition time according to the present invention, have significantly superior initial efficiency and cycle maintenance rate compared to Comparative Examples 1 to 4, which do not satisfy the above.

[0181] Meanwhile, in Comparative Examples 1 and 2, silicon was deposited in a particle shape rather than a film shape due to excessive silane flow rate and rapid deposition, which significantly reduced the initial efficiency and cycle maintenance rate. In addition, as the cycle was repeated, it was found that the SEI layer was continuously formed due to the presence of silicon in the particle shape, which reduced the amount of lithium and rapidly reduced the capacity.

[0182] Additionally, in the case of Comparative Example 3, the cycle maintenance rate showed a certain value, but the initial capacity and initial efficiency were significantly low.

[0183] In addition, in the case of Comparative Example 4, although the production of a carbon-silicon composite was possible, a lumping phenomenon occurred, and a carbon-silicon composite was formed at a level that could not be evaluated, making electrochemical evaluation impossible.

[0184]

[0185] <Experimental Example 2: SEM Image Analysis>

[0186] Surface and cross-sectional (BSE mode) SEM analyses were performed for Example 1 and Comparative Example 2, respectively.

[0187] As a result, as shown in Fig. 2, Example 1 was able to confirm that silicon was formed in the form of a film on the surface, and as shown in Fig. 3, Comparative Example 2 was able to confirm that silicon was formed in the form of small particles on the surface.

[0188] In addition, as shown in Fig. 4, Example 1 confirmed that the silicon layer was formed in a film shape and was formed very uniformly, and accordingly, it was found that a uniform SEI layer could be formed and the capacity retention rate could be high in cycle repetition.

[0189] In addition, as shown in Fig. 5, in Comparative Example 2, it was confirmed that silicon was formed in the form of large particles and that silicon was formed in an uneven particle form, and accordingly, it was found that the capacity retention rate could be rapidly reduced due to the formation of an uneven SEI layer, etc.

[0190] (Figures 4 and 5 were measured in BSE mode, and the higher the element number, the brighter it appears. Therefore, in the case of Figure 4, it was found that the bright layer formed on the surface of the carbon support was a silicon layer.)

[0191]

[0192] <Example 3>: Preparation of hard carbon and carbon-silicon composites

[0193] 300 g of petroleum residual oil (YNCC, HTC PFO (pyrolysis fuel oil)) was placed in a reactor equipped with a stirrer, and pyrolysis and polycondensation were performed at 430°C for 3 hours while supplying air at a flow rate of 100 ml / min. During this time, the stirrer was rotated at a speed of 200 rpm to mix the reactants. The polymerized pitch was solidified and pelletized to obtain solid pitch pellets with an average particle size (particle size distribution D50) of 1 to 30 mm.

[0194] After crushing the solid pitch pellets obtained above (powdered pitch), 100 g was placed in a rotary kiln with two zones, where stabilization and carbonization were performed sequentially. The stabilization and carbonization conditions and the properties of the carbon support (hard carbon) are as shown in Table 4 below.

[0195] Afterwards, the carbon support was pulverized using a pulverizer (NETZSCH, air jet mill).

[0196] At this time, the specific surface area of ​​the carbon support (hard carbon) was measured using Belsorp mini II according to ASTM D4820-93. The tap density of the carbon support was measured using a tap density analyzer (Electrolab, ETD-1020x) according to ASTM B527. The average particle size (particle size distribution D50) of the carbon support was measured using a particle size analyzer (Horiba, laser particle analyzer, LA-960V2) according to ASTM E112.

[0197] Then, a carbon-silicon composite was manufactured using the hard carbon support manufactured above. 15 g of the carbon support was placed in a rotary kiln, and silane (SiH4) gas was injected to deposit silicon on the carbon support. The silicon deposition conditions and the physical properties of the carbon-silicon composite are shown in Table 4 below.

[0198]

[0199] <Example 4>: Preparation of soft carbon and carbon-silicon composites

[0200] 300 g of petroleum residue oil (YNCC, HTC PFO (pyrolysis fuel oil)) was placed in a reactor equipped with a stirrer, and pyrolysis and polycondensation were performed at 450°C for 3 hours while supplying air at a flow rate of 100 ml / min. During this time, the stirrer was rotated at a speed of 200 rpm to mix the reactants. The polymerized pitch was solidified and pelletized to obtain solid pitch pellets with an average particle size of 1 to 30 mm.

[0201] After crushing the solid pitch pellets obtained above (powdered pitch), 100 g was placed in a crucible and placed in an oven for stabilization and carbonization. The stabilization and carbonization conditions and the properties of the carbon support (soft carbon) are shown in Table 4 below.

[0202] Afterwards, the carbon support was pulverized using a pulverizer (NETZSCH, air jet mill).

[0203] At this time, the specific surface area of ​​the carbon support (soft carbon) was measured using Belsorp mini II according to ASTM D4820-93. The tap density of the carbon support was measured using a tap density analyzer (Electrolab, ETD-1020x) according to ASTM B527. The average particle size of the carbon support was measured using a particle size analyzer (Horiba, laser particle analyzer, LA-960V2) according to ASTM E112.

[0204] Furthermore, a carbon-silicon composite was prepared using the soft carbon support prepared above. 15 g of the carbon support was placed in a rotary kiln, and silane (SiH4) gas was injected to deposit silicon on the carbon support. The silicon deposition conditions and the physical properties of the carbon-silicon composite are shown in Table 4 below.

[0205] Step Conditions Example 3 Example 4 Stabilization temperature (℃) 300 300 Hours (hr) 33 Atmosphere Air Air Carbonization temperature (℃) 900 1600 Hours (hr) 11 Atmosphere Nitrogen Argon Carbon Support Properties Average particle size (㎛) 49.7 5 0.1 Specific surface area (㎡ / g) 2.0 4.0 Tap density (g / ml) 0.66 4 0.88 2 Particle size distribution after grinding D50 (㎛) 4.9 5.6 Silicon deposition conditions Pressure Normal pressure Normal pressure Temperature (℃) 475 475 Silane flow rate (sccm) 200 200 Hours 60 60 Carbon-silicon composite particles Silicon content (wt%) 34.9 3 1.4 Particle size distribution D50 (㎛) 11.6 10.7 Specific surface area (㎡ / g) 0.5 1.4 Silicon layer thickness (nm) 8 4 1 1

[0206]

[0207] Experimental Example 3: Electrochemical Evaluation

[0208] Electrochemical evaluation was performed using the same method as in Experimental Example 1, but the carbon-silicon composites of Examples 3 and 4 were used as the carbon-silicon composites, respectively. The results are shown in Table 5 below.

[0209] Classification Example 3 Example 4 Electrochemical evaluation Charge capacity (mAh / g) 1692 1528 Discharge capacity (mAh / g) 1509 1401 Initial efficiency (%) 89.1 91.7 Cycle maintenance rate (%) 50.1 52.7

[0210] As can be seen from Table 5 above, it was confirmed that the coin cell applying Examples 3 and 4 that satisfy the carbon support type of the present invention has excellent initial efficiency and cycle maintenance rate.

[0211]

[0212] Although one embodiment of the present invention has been described above, the spirit of the present invention is not limited to the embodiment presented in this specification, and a person skilled in the art who understands the spirit of the present invention will be able to easily propose other embodiments by adding, changing, deleting, or adding components within the scope of the same spirit, but this will also be considered to fall within the spirit of the present invention.

Claims

1. A method for manufacturing a carbon-silicon composite, comprising the steps of: forming a film-shaped silicon layer including the surface of a carbon support to manufacture a carbon-silicon composite; 2. In paragraph 1, A method for manufacturing a carbon-silicon composite, wherein the step of manufacturing the carbon-silicon composite is performed by chemical vapor deposition (CVD) of a silicon source onto the carbon support.

3. In paragraph 2, A carbon-silicon composite having a supply flow rate of the silicon source of 50 to 300 sccm per 10 g of the carbon support.

4. In paragraph 2, The above chemical vapor deposition is performed for 40 to 120 minutes, carbon-silicon composite.

5. Carbon support; and A carbon-silicon composite comprising a film-shaped silicon layer disposed including the surface of the carbon support.

6. In paragraph 5, A carbon / silicon composite, wherein the carbon support comprises a nonporous carbon support comprising at least one of hard carbon and soft carbon.

7. In paragraph 5, The above carbon support comprises a porous carbon support, A carbon / silicon composite in which the silicon layer is disposed on the surface and inside the pores of the porous carbon support.

8. In paragraph 5, The above carbon-silicon composite is a carbon-silicon composite having a specific surface area of ​​200㎡ / g or less.

9. In paragraph 5, A carbon-silicon composite, wherein the average thickness of the silicon layer is 0.5 to 50% of the radius of the carbon support.

10. In paragraph 5, A carbon-silicon composite, wherein the silicon layer is 10 to 80 wt% of the total weight of the carbon-silicon composite.

11. In paragraph 7, The above porous carbon support is a carbon-silicon composite having a volume ratio of mesopores with a pore size of 2 to 50 nm of 10 to 80% based on the total pore volume.

12. In paragraph 7, The above porous carbon support is a carbon-silicon composite having a BET specific surface area of ​​300 to 3,000 m2 / g and a tap density of 0.05 to 0.5 g / ㎖.

13. In paragraph 5, The above carbon support is a carbon-silicon composite having a particle size distribution D50 of 2 to 15 μm and a particle size distribution Dmax of 25 μm or less.

14. A lithium ion battery comprising a carbon-silicon composite according to any one of claims 5 to 13.

15. An all-solid-state battery comprising a carbon-silicon composite according to any one of claims 5 to 13.

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