Porous carbon / silicon composite, processes for preparing the same, anode active material and all-solid-state battery comprising the same

Abstract

This invention relates to a carbon / silicon composite, a method for manufacturing the same, a negative electrode active material comprising the composite, and an all-solid-state battery. According to embodiments of the present invention, the carbon / silicon composite, by removing Si-H sites and dangling bond sites on the silicon surface, can reduce gas generation. Furthermore, during the formation of the negative electrode active material in a lithium-ion battery or the SEI (Solid Electrolyte Interphase) in an all-solid-state battery, it can improve the initial coulombic efficiency (ICE) by reducing side reactions with the electrolyte.

Description

[Technical Field]

[0001] This invention relates to a carbon / silicon composite, and more specifically, to a carbon / silicon composite, a method of manufacturing the composite, a negative electrode active material comprising the composite, and an all-solid-state battery. [Previous Technology]

[0002] Recently, with the development of the information and telecommunications industry, the demand for electronic devices has increased dramatically, and with the active electric vehicle market, the demand for batteries used in such electronic devices or electric vehicles has also grown significantly.

[0003] Secondary batteries, including lithium-ion batteries containing liquid electrolytes and all-solid-state batteries, are most widely used in such applications due to their high energy density and low self-discharge rate when not in use. Secondary batteries are mostly composed of an anode, a cathode, and an electrolyte (liquid or solid). Carbon-based materials such as graphite are widely used as cathode active materials in secondary batteries.

[0004] Recently, silicon-based cathode active materials have been used in an effort to improve the capacity of secondary batteries. Silicon has attracted much attention as a potential next-generation battery anode active material that can replace graphite due to its theoretically extremely high energy density. However, because silicon can expand up to 300% of its original volume when it reacts with lithium during charging and discharging, it suffers from extremely low mechanical stability, such as breakage, as it is used as an anode active material, as charging and discharging continues.

[0005] In order to solve the above problems, Japanese Patent No. 4393610 discloses that silicon and carbon are combined in a machining process and that a carbon layer is coated on the surface of silicon particles as a negative electrode active material using chemical vapor deposition (CVD). However, there are still limitations in suppressing its volume expansion and contraction during charging and discharging.

[0006] In addition, during the process of crushing silicon raw materials for micronization, the silicon-based negative electrode active material will generate an excessive solid electrolyte interphase (SEI) layer, which is unstable and thus also leads to problems such as reduced battery stability and electrical performance.

[0007] Advanced Technology Documents

[0008] Patent Documents

[0009] (Patent Document 0001) Japanese Patent Publication No. 4393610 [Summary of the Invention]

[0010] Solving the problem:

[0011] The purpose of this invention is to provide a carbon / silicon composite that reduces gas generation by removing the Si-H sites and dangling bond sites on the surface of the carbon / silicon composite. Furthermore, it can improve the initial coulombic efficiency (ICE) by reducing side reactions with the electrolyte during the formation of the negative electrode active material of a lithium secondary battery or the SEI (Solid Electrolyte Interphase) of an all-solid-state battery.

[0012] Another object of the present invention is to provide a method for manufacturing the carbon / silicon composite.

[0013] Another object of the present invention is to provide a negative electrode active material comprising the carbon / silicon composite and an all-solid-state battery.

[0014] The technical solution of the present invention is as follows:

[0015] To solve the above problems, the present invention provides a carbon / silicon composite comprising: a carbon support; and silicon, comprising silicon disposed on the surface of the carbon support; wherein the Si-H bonds and dangling bonds on the silicon surface are at least partially oxidized.

[0016] According to one embodiment of the present invention, the carbon support may comprise a non-porous carbon support, which comprises one or more of hard carbon and soft carbon.

[0017] In addition, the carbon support may include a porous carbon support, and the silicon may be disposed on the surface and inside the pores of the porous carbon support.

[0018] In addition, the volume ratio of mesopores with a pore size of 2 to 50 nm as a reference based on the total pore volume of the porous carbon support can be 10 to 80%.

[0019] In addition, the porous carbon support has a BET specific surface area of ​​300 to 3,000 m2 / g, a bulk density of 0.05 to 0.5 g / ml, and a particle size distribution D50 of 1 to 20 µm.

[0020] In addition, the silicon can be 5 to 80% by weight of the total weight of the carbon / silicon composite.

[0021] In addition, the present invention provides a method for manufacturing a carbon / silicon composite, which includes the following steps: (1) forming silicon on the surface containing a carbon support to manufacture a composite; and (2) at least partially oxidizing the Si-H bonds and dangling bonds on the silicon surface of the composite to manufacture a carbon / silicon composite.

[0022] According to one embodiment of the present invention, step (1) can be performed by chemical vapor deposition (CVD) of silicon supply source onto the carbon support.

[0023] In addition, step (2) can be performed by treating the composite with O2 plasma.

[0024] Furthermore, the O2 plasma treatment system can be carried out at an O2 gas flow rate of 10 to 100 sccm, a power of 50 to 200 W, and a time of 0.5 to 10 minutes.

[0025] In addition, step (2) can be performed by heat treatment of the composite.

[0026] In addition, the heat treatment can be carried out in an air atmosphere at a temperature of 350 to 600°C for 0.5 to 2 hours.

[0027] In addition, the present invention provides the above-mentioned negative electrode active material, comprising: a carbon / silicon composite; and a carbon-based negative electrode material.

[0028] In addition, the present invention provides the above-mentioned all-solid-state battery, comprising: an SEI (Solid Electrolyte Interphase) film, wherein the SEI film comprises a carbon / silicon composite.

[0029] [Effects of the Invention]

[0030] According to the embodiments of the present invention, the carbon / silicon composite can reduce gas generation by removing the Si-H sites and dangling bond sites on the silicon surface, and can improve the initial coulombic efficiency (ICE) by reducing the side reactions with the electrolyte during the formation of the negative electrode active material of the lithium secondary battery or the SEI (Solid Electrolyte Interphase) of the all-solid-state battery.

Implementation Method

[0032] The present invention is not limited to the contents disclosed below, and various modifications may be made as long as the essence of the present invention is not changed.

[0033] In this specification, "comprising" should be understood to mean, unless otherwise specified, that other constituent elements may also be included.

[0034] All numerical values ​​and descriptions used to indicate the amount of components, reaction conditions, etc. in this specification shall be understood to be modified by the term "about" unless otherwise stated.

[0035] In this specification, the description of a constituent element being formed on / under another constituent element, or being connected or combined with each other, includes the formation, connection or combination of such constituent elements directly or indirectly through other constituent elements.

[0036] The present invention will now be described in more detail.

[0037] Carbon / Silicon Complex

[0038] According to one embodiment of the present invention, a carbon / silicon composite is provided, comprising: a carbon support; and silicon, comprising silicon disposed on the surface of the carbon support; wherein the Si-H bonds and dangling bonds on the silicon surface are at least partially oxidized.

[0039] On the other hand, the BET specific surface area of ​​the carbon / silicon composite can be less than 200 m² / g, preferably less than 100 m² / g, and more preferably less than 50 m² / g. If the BET specific surface area of ​​the carbon / silicon composite exceeds 200 m² / g, due to the high BET value, a large amount of SEI layer will be generated in the reaction with the electrolyte, which may result in poor electrochemical performance.

[0040] Furthermore, in the carbon / silicon composite of the present invention, the Si-H bonds and dangling bonds on the silicon surface are at least partially oxidized, thereby reducing gas generation. When the negative electrode active material of a lithium secondary battery or the SEI (Solid Electrolyte Interphase) of an all-solid-state battery is formed, it is more advantageous in terms of improving the initial coulombic efficiency (ICE) by reducing the side reactions with the electrolyte.

[0041] The constituent elements of a carbon / silicon composite according to one embodiment of the present invention will be described below.

[0042] Carbon support

[0043] The carbon / silicon composite system according to an embodiment of the present invention comprises a carbon support.

[0044] If the carbon support is a carbon support commonly used in this technical field, it can be used without limitation. Preferably, any one or more of non-porous carbon supports and porous carbon supports can be used. More preferably, any one or more of graphite, hard carbon, soft carbon and porous carbon supports can be used. Even more preferably, using any one or more of hard carbon, soft carbon and porous carbon supports is beneficial to achieving the purpose of this invention.

[0045] According to one embodiment of the present invention, the carbon support may be a porous carbon support, in which case the silicon may be disposed on the surface and inside the pores of the porous carbon support.

[0046] Based on the total pore volume, the mesopore volume ratio of the porous carbon support with a pore size of 2 to 50 nm can be 10 to 80%, preferably 30 to 60%, and more preferably 40 to 50%. If the mesopore volume ratio of the porous carbon support is less than 10%, due to the excessive number of micropores, a relatively large amount may be formed on the outside of silicon. If the mesopore volume ratio of the porous carbon support exceeds 80%, the particle hardness is insufficient, and if it is used to prepare electrodes, there may be a risk of electrode structure collapse.

[0047] Furthermore, the porous carbon support may have a BET specific surface area of ​​300 to 3,000 m² / g. Preferably, the porous carbon support may have a BET specific surface area of ​​300 to 1,500 m² / g, and more preferably, it may have a BET specific surface area of ​​500 to 1,500 m² / g. If the BET specific surface area of ​​the porous carbon support is less than 300 m² / g, there may be insufficient effective pores due to excessive macropores. If the BET specific surface area of ​​the porous carbon support exceeds 3,000 m² / g, there may be a relatively large amount of micropores deposited on the exterior of silicon due to excessive micropores.

[0048] Furthermore, the porous carbon support may have a bulk density of 0.05 to 0.5 g / ml. Preferably, the porous carbon support may have a bulk density of 0.05 to 0.45 g / ml, more preferably, it may have a bulk density of 0.1 to 0.45 g / ml. If the bulk density of the porous carbon support is less than 0.05 g / ml, the yield may be reduced due to difficulties in process control during silicon source deposition. If the bulk density of the porous carbon support exceeds 0.5 g / ml, it may be difficult to form a uniform structure during silicon source deposition.

[0049] Furthermore, the porous carbon support may have a particle size distribution D50 of 1 to 20 µm. Preferably, the porous carbon support may have a particle size distribution D50 of 3 to 20 µm, and more preferably, it may have a particle size distribution D50 of 3 to 10 µm. If the particle size distribution D50 of the porous carbon support is less than 1 µm, the silicon supply source may not be able to fully penetrate into the pores, and will only form relatively large quantities on the outside of the particles. If the particle size distribution D50 of the porous carbon support exceeds 20 µm, silicon may be difficult to form sufficiently within the pores.

[0050] When the carbon / silicon composite of the present invention comprises a porous carbon support having the above-mentioned characteristics, when the carbon / silicon composite is used as a negative electrode active material, it can have excellent electrical conductivity and can alleviate the stress caused by the volume expansion of silicon.

[0051] Silicon

[0052] The carbon / silicon composite system according to an embodiment of the present invention comprises silicon, which is disposed on the surface of the carbon carrier.

[0053] In the carbon / silicon composite of the present invention, the carbon support and silicon are configured as described above, so the negative electrode material made from the carbon / silicon composite of the present invention can have a higher capacitance and can minimize the impact caused by the volume expansion of silicon.

[0054] Here, the silicon performs the function of filling lithium, so when the carbon / silicon composite of the present invention is used as the negative electrode active material, the silicon can play the role of the main negative electrode active material.

[0055] On the other hand, the Si-H bonds and dangling bonds on the silicon surface are at least partially oxidized, which can reduce gas generation and is more advantageous in terms of improving the initial coulombic efficiency (ICE) at the level of the negative electrode active material of lithium secondary batteries or the SEI (Solid Electrolyte Interphase) of all solid-state batteries.

[0056] The silicon can be crystalline or amorphous, preferably amorphous or a similar phase. If the silicon is crystalline, the smaller the crystal size, the denser the composite can be obtained, thereby enhancing strength and preventing crack formation. Therefore, the initial efficiency or cycle life characteristics of the secondary battery can be improved. On the other hand, if the silicon is amorphous or a similar phase, the expansion or contraction during charging and discharging of the secondary battery is smaller, thus improving battery performance such as capacity characteristics.

[0057] The silicon can be in the form of a thin film, and the average thickness of the silicon layer can be from 10 nm to 5 µm. If the average thickness of the silicon layer is less than 10 nm, it may lead to a decrease in capacitance. If the average thickness exceeds 5 µm, it may not be able to solve the problem caused by silicon volume expansion, which may cause structural damage to the negative electrode material and reduce cycle characteristics.

[0058] Furthermore, the silicon may be 5 to 80% by weight of the total weight of the carbon / silicon composite according to the present invention, preferably 10 to 50% by weight. If the silicon content in the total weight of the carbon / silicon composite is less than 5% by weight, it may lead to a decrease in capacitance. If the silicon content exceeds 80% by weight, it may not be able to solve the problem caused by silicon volume expansion during charging and discharging, which may cause structural damage to the negative electrode material and reduce cycle characteristics.

[0059] The silicon may further comprise silicon oxide compounds. The silicon oxide compounds may be represented by the general formula SiOₓ (0.5≤x≤2). Here, if the value of x is less than 0.5, it may cause increased expansion and contraction during charging and discharging, and the lifetime characteristics may deteriorate. If the value of x is greater than 2, it may lead to an increase in inactive oxides, thereby reducing the initial efficiency of the secondary battery.

[0060] The content of silicon oxide compounds contained in the silicon may be less than 50% by weight based on the total weight of the silicon. If the content of silicon oxide compounds in the silicon exceeds 50% by weight, the initial efficiency of the secondary battery may be reduced.

[0061] Method for manufacturing carbon / silicon composites

[0062] A carbon / silicon composite according to one embodiment of the present invention is manufactured by a manufacturing method comprising the following steps: (1) forming silicon on a surface containing a carbon support to manufacture the composite; and (2) at least partially oxidizing the Si-H bonds and dangling bonds on the silicon surface of the composite to manufacture the carbon / silicon composite.

[0063] The steps of a method for manufacturing a carbon-silicon composite according to one embodiment of the present invention will be described below.

[0064] Step (1)

[0065] In step (1) above, silicon is formed on the surface containing the carbon carrier to manufacture a composite.

[0066] On the other hand, if the carbon support is a porous carbon support, then step (1) can be a step of forming on the surface and in the pores of the porous carbon support to manufacture a carbon / silicon composite.

[0067] In a specific embodiment of the present invention, the step of forming silicon on the surface containing the carbon support can be performed using apparatus (e.g., rotary kiln) and methods (e.g., chemical vapor deposition (CVD)) known in the art to which this invention pertains. Specifically, a silicon source can be supplied to the carbon support and CVD can be performed to form silicon on the surface containing the carbon support.

[0068] In a specific embodiment of the present invention, the silicon supply 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.

[0069] The CVD of the silicon supply source can be performed at a temperature of 300 to 700°C. For example, the CVD of the silicon supply 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.

[0070] Step (2)

[0071] In step (2) above, the Si-H bonds and dangling bonds on the silicon surface of the composite are at least partially oxidized to produce a carbon / silicon composite.

[0072] In a specific embodiment of the present invention, the step of at least partially oxidizing the Si-H bonds and dangling bonds on the silicon surface of the composite can be performed by O2 plasma treatment of the composite.

[0073] The O2 plasma treatment system can be carried out at an O2 gas flow rate of 10 to 100 sccm, a power of 50 to 200 W, and a time of 0.5 to 10 minutes. By satisfying the O2 plasma flow rate, power, and time conditions, it is more advantageous to achieve the purpose of the present invention.

[0074] In another embodiment of the present invention, the step of at least partially oxidizing the Si-H bonds and dangling bonds on the silicon surface of the composite can be performed by heat treatment of the composite.

[0075] The heat treatment can be carried out in an air atmosphere at a temperature of 350 to 600°C for 0.5 to 2 hours, preferably in an air atmosphere at a temperature of 400 to 500°C for 0.5 to 1.5 hours. By meeting the temperature and time conditions, gas generation can be reduced, which is more conducive to achieving the purpose of the present invention.

[0076] Preliminary Steps

[0077] As described above, if the carbon support is a carbon support commonly used in this technical field, it can be used without limitation. Preferably, any one or more of non-porous carbon supports and porous carbon supports can be used. More preferably, any one or more of graphite, hard carbon, soft carbon and porous carbon supports can be used. Even more preferably, using any one or more of hard carbon, soft carbon and porous carbon supports is beneficial to achieving the purpose of this invention.

[0078] If the carbon support is a porous carbon support, the method for manufacturing the carbon / silicon-carbon composite may include the following steps before step (1): (a) thermally cracking and polycondensing petroleum-based raw materials to synthesize asphalt, (b) curing and granulating the asphalt to obtain granular asphalt, or curing, granulating and pulverizing the asphalt to obtain powdered asphalt, (c) stabilizing the granular or powdered asphalt, (d) carbonizing the stabilized asphalt to obtain a carbide, and (e) activating the carbide to obtain a porous carbon support.

[0079] In step (a), petroleum-based feedstocks can be thermally cracked and polycondensed to synthesize asphalt.

[0080] In specific embodiments of the present invention, the petroleum-based feedstock may be selected from the group consisting of pyrolysis fuel oil (PFO), naphtha cracking bottom oil (NCB), ethylene cracker bottom oil (EBO), vacuum residue (VR), deasphalted oil (DAO), atmospheric residue (AR), fluidized bed catalytic cracking decant oil (FCC-DO), RFCC-DO (residue fluid catalytic cracking decant oil), and heavy aromatic oil, and may include at least one of them. In a preferred embodiment of the present invention, the petroleum-based feedstock may include pyrolysis fuel oil.

[0081] In a specific embodiment of the present invention, the petroleum-based raw material may contain 10 to 90% by weight of aromatic compounds. Preferably, the petroleum-based raw material may contain 20 to 80% by weight of aromatic compounds, and more preferably, the content may be 30 to 70% by weight. If the content of aromatic compounds in the petroleum-based raw material meets the above range, a porous carbon support with controlled pore characteristics can be obtained even without further pulverizing the solid asphalt particles as described below, and by directly performing stabilization, carbonization, and activation.

[0082] In a specific embodiment of the present invention, the aromatic compound may have 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, tetrahydronaphthalene, and fluorene. In this case, a porous carbon support with controlled pore characteristics can be obtained even without further pulverizing the solid pitch particles as described below, but by directly performing stabilization, carbonization, and activation.

[0083] In a specific embodiment of the present invention, the thermal cracking and polycondensation of petroleum-based raw materials can be carried out at a temperature of 350 to 500°C. In a preferred embodiment of the present invention, the thermal cracking and polycondensation of petroleum-based raw materials can be carried out at a temperature of 400 to 500°C. In a more preferred embodiment of the present invention, the thermal cracking and polycondensation of petroleum-based raw materials can be carried out at a temperature of 430 to 470°C. If the thermal cracking and polycondensation temperature of the petroleum-based raw materials is 350 to 500°C, asphalt containing more relatively low molecular weight components can be produced, and during the activation process in step (e) as described later, the smaller relatively molecular weight components will first vaporize, thereby fully forming mesopores in the carbon support. If the thermal cracking and polycondensation temperature of the petroleum-based raw materials is below 350°C, it will be difficult to produce asphalt that is solid at room temperature; if the temperature exceeds 500°C, the asphalt will contain more relatively high molecular weight components, making it difficult to produce a carbon support with mesopores.

[0084] In a specific embodiment of the present invention, the thermal cracking and polycondensation of petroleum-based feedstocks can be carried out in an atmosphere of an oxidizing gas, an inert gas, or a mixture thereof. In a preferred embodiment of the present invention, the oxidizing gas can be oxygen, ozone, or a combination thereof, the inert gas can be nitrogen, helium, neon, argon, or a combination thereof, and the mixed gas can be air, but is not particularly limited thereto.

[0085] If oxidizing gases are used during the pyrolysis and polycondensation of petroleum-based feedstocks, asphalt with a higher softening point can be produced; however, it is difficult to carry out pyrolysis and polycondensation at high temperatures. If inert gases are used during the pyrolysis and polycondensation of petroleum-based feedstocks, pyrolysis and polycondensation can be carried out at high temperatures; however, it is difficult to produce asphalt with a relatively higher softening point. If a mixture of oxidizing and inert gases is used during the pyrolysis and polycondensation of petroleum-based feedstocks, pyrolysis and polycondensation can be carried out at relatively high temperatures to produce asphalt with a relatively higher softening point.

[0086] In a specific embodiment of the present invention, during the thermal cracking and polycondensation of petroleum-based feedstocks, the aforementioned gas can be supplied at a flow rate of 10 to 800 ml / min. In a preferred embodiment of the present invention, during the thermal cracking and polycondensation of petroleum-based feedstocks, the aforementioned gas can be supplied at a flow rate of 100 to 500 ml / min. If the flow rate of the aforementioned gas is less than 10 ml / min, the yield of asphalt can be increased; however, an excessive amount of low molecular weight components is detrimental to subsequent processes (e.g., stabilization). If the flow rate of the aforementioned gas exceeds 800 ml / min, the yield of asphalt may decrease.

[0087] In a specific embodiment of the present invention, the thermal cracking and polycondensation of petroleum-based raw materials can be carried out for 1 to 10 hours. In a preferred embodiment of the present invention, the thermal cracking and polycondensation of petroleum-based raw materials can be carried out for 2 to 8 hours. In a more preferred embodiment of the present invention, the thermal cracking and polycondensation of petroleum-based raw materials can be carried out for 2 to 7 hours. If the thermal cracking and polycondensation time of petroleum-based raw materials is less than 1 hour, it is difficult to produce asphalt with a high softening point, and if the thermal cracking and polycondensation time of petroleum-based raw materials exceeds 10 hours, excessive quinoline insoluble components may be generated.

[0088] In a specific embodiment of the present invention, the thermal cracking and polycondensation of petroleum-based feedstocks can be carried out under stirring. The stirring conditions for petroleum-based feedstocks are not particularly limited; for example, a stirrer rotating at a speed of 10 to 500 rpm can be used.

[0089] In a specific embodiment of the present invention, the asphalt synthesized in step (a) may have a softening point of 200 to 350°C. In a preferred embodiment of the present invention, the asphalt may have a softening point of 200 to 330°C. In a more preferred embodiment of the present invention, the asphalt may have a softening point of 200 to 300°C. Because the asphalt manufactured according to the present invention has a high softening point, when used as a precursor for preparing a carbon support, the stabilization process is easier to perform, and a higher yield can be obtained after carbonization and activation.

[0090] In a specific embodiment of the present invention, the yield of asphalt synthesized in step (a) can be 10 to 50% by weight. In a preferred embodiment of the present invention, the yield of asphalt can be 10 to 40% by weight. In a more preferred embodiment of the present invention, the yield of asphalt can be 20 to 30% by weight.

[0091] In a specific embodiment of the present invention, a pretreatment step may be performed on the petroleum-based raw material before step (a) above. By performing the pretreatment step to remove the low-boiling-point components contained in the petroleum-based raw material, asphalt with a higher softening point can be manufactured.

[0092] In a specific embodiment of the present invention, the pretreatment step may be performed at a temperature that is the same as or lower than the thermal cracking and polycondensation temperature of the petroleum-based raw material in step (a), but is not particularly limited to this condition. Specifically, the pretreatment step may be performed at 250 to 450°C, preferably at 250 to 400°C, and more preferably at 300 to 400°C.

[0093] In a specific embodiment of the present invention, the pretreatment step may be performed within the same or shorter time as the thermal cracking and polycondensation time of the petroleum-based raw material in step (a), but is not particularly limited to this condition. Specifically, the pretreatment step may be performed for 1 to 8 hours, preferably for 1 to 6 hours, and more preferably for 1 to 5 hours.

[0094] In addition, in step (b), the asphalt may be cured and granulated to obtain granular asphalt, or the asphalt may be cured, granulated and crushed to obtain powdered asphalt.

[0095] First, regarding the granular asphalt, the liquid asphalt obtained in step (a) can be solidified, for example, by extrusion and cooling, and granulated to the desired size to obtain solid asphalt particles (i.e., granular asphalt). The process of extruding, cooling, and granulating liquid asphalt to obtain solid asphalt particles can be performed using commercially available equipment. For example, this process can be performed using a dual-belt cooling pellet mill from IPCO, but is not particularly limited to this equipment.

[0096] The asphalt particles obtained in step (b) have an average particle size of 1 to 30 mm, preferably 5 to 25 mm (particle size distribution D50). When the average particle size (particle size distribution D50) of the asphalt particles is within this range, it is not necessary to further crush them, but a porous carbon carrier can be manufactured by stabilization, carbonization and activation as described later.

[0097] Furthermore, the powdered asphalt can be further crushed or pulverized and classified. Crushing or pulverizing can further refine the asphalt particles, and classification can make the particle size distribution of the asphalt particles uniform. Here, classification can be performed using dry classification, wet classification, or grading using sieves. Through crushing or pulverizing and classification, powdered asphalt with an average particle size (particle size distribution D50) of 50 to 500 µm can be obtained.

[0098] In addition, in step (c), a step of stabilizing the granular asphalt or powdered asphalt may be performed.

[0099] First, the asphalt obtained in step (b) is oxidized once to stabilize its carbon structure.

[0100] In a specific embodiment of the present invention, the stabilization of asphalt can be performed under an oxidizing gas atmosphere. In a preferred embodiment of the present invention, the stabilization of asphalt can be performed under an air atmosphere, but is not particularly limited thereto.

[0101] In a specific embodiment of the present invention, the stabilization of asphalt can be performed at a temperature of 100 to 500°C, preferably at a temperature of 150 to 300°C. When the asphalt is stabilized at this temperature, the carbon structure in the granular or powdered asphalt will change from thermoplastic to thermohardening, and its structure can be stably maintained during the subsequent carbonization process. At this time, the heating rate can be 2 to 10°C / min. If the heating rate is too slow, the production efficiency will be poor, and if the heating rate is too fast, it may be difficult to perform uniform stabilization treatment.

[0102] In a specific embodiment of the present invention, the stabilization can be performed at a pressure of 0.1 to 10 bar, preferably at a pressure of 0.5 to 5 bar. When the stabilization is performed at this pressure, the internal carbon structure of the granular or powdered asphalt can also be sufficiently stabilized.

[0103] In a specific embodiment of the present invention, the stabilization can be performed under an oxidizing gas flow rate of 0.1 to 500 ml / min, preferably under an oxidizing gas flow rate of 1 to 300 ml / min, and more preferably under an air flow rate. When the stabilization is performed under the oxidizing gas flow rate, the internal carbon structure of the granular or powdered asphalt can also be sufficiently stabilized.

[0104] In a specific embodiment of the present invention, the stabilization can be performed over a period of 1 to 10 hours, preferably over a period of 2 to 8 hours. When the stabilization is performed within this time period, the internal carbon structure of the granular or powdered asphalt can also be sufficiently stabilized.

[0105] Furthermore, in step (d), the stabilized asphalt can be carbonized to obtain a carbide. By carbonizing the stabilized asphalt, other functional groups contained in the asphalt can be removed, and a carbide that is substantially composed of pure carbon can be obtained.

[0106] 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.

[0107] In a specific embodiment of the present invention, the carbonization can be performed at a temperature exceeding 700°C to 1,000°C, preferably at a temperature of 800 to 900°C. During carbonization, if the temperature is below this range, the carbonization may not proceed sufficiently; if the temperature is above this range, the carbonization yield may decrease.

[0108] In a specific embodiment of the present invention, the carbonization can be performed under an inert gas flow rate of 0.1 to 30 ml / min, preferably under an inert gas flow rate of 0.1 to 10 ml / min. When the carbonization is performed under this inert gas flow rate condition, the stabilized asphalt can be fully carbonized.

[0109] In a specific embodiment of the present invention, the stabilization can be performed over a period of 0.5 to 5 hours, preferably over a period of 1 to 3 hours. When the carbonization is performed within this time, the stabilized asphalt can be fully carbonized.

[0110] Furthermore, in step (e), the carbide (carbonized bitumen) can be activated to produce a porous carbon support. By activating the carbide, pores can be formed in the bitumen particles, thereby producing a porous carbon support.

[0111] In a specific embodiment of the present invention, the activation of the carbide can be performed under an oxidizing gas atmosphere. In a preferred embodiment of the present invention, the activation of the carbide can be performed under a water vapor atmosphere, but is not particularly limited thereto.

[0112] In a specific embodiment of the present invention, the activation of the carbide can be performed at a temperature exceeding 700°C to 1,000°C, preferably at a temperature of 800 to 900°C. When the activation of the carbide is performed at this temperature, a porous carbon support with sufficiently formed micropores and mesopores can be obtained.

[0113] In a specific embodiment of the present invention, the activation of the carbide can be performed at a pressure of 0.1 to 10 bar, preferably at a pressure of 0.1 to 5 bar. When the activation of the carbide is performed at this pressure, a porous carbon support with sufficient micropores and mesopores can be obtained.

[0114] In a specific embodiment of the present invention, the activation of the carbide can be performed under an oxidizing gas flow rate of 0.1 to 100 ml / min, preferably under an oxidizing gas flow rate of 0.1 to 50 ml / min, and even more preferably under a water vapor flow rate. When the activation of the carbide is performed under the oxidizing gas flow rate, a porous carbon support with sufficiently formed micropores and mesopores can be obtained.

[0115] In a specific embodiment of the present invention, the activation of the carbide can be performed over a period of 0.5 to 5 hours, preferably over a period of 1 to 3 hours. When the activation of the carbide is performed within this time period, a porous carbon support with sufficiently formed micropores and mesopores can be obtained.

[0116] In a specific embodiment of the present invention, the stabilization, carbonization, and activation steps (c) to (e) described above can be performed in a microwave-heated furnace. In a preferred embodiment of the present invention, the stabilization, carbonization, and activation steps (c) to (e) described above can all be performed in a microwave-heated furnace. A microwave-heated furnace can prevent the external temperature of the asphalt from rising and can raise the temperature of the asphalt itself, therefore it is a preferred method, but not particularly limited thereto.

[0117] In a specific embodiment of the present invention, the stabilization, carbonization, and activation steps (c) to (e) described above can be performed continuously in a single device. In a preferred embodiment of the present invention, the stabilization, carbonization, and activation steps (c) to (e) described above can be performed continuously in a single rotary kiln, but are not particularly limited to this device. The continuous performance of the stabilization, carbonization, and activation steps (c) to (e) described above in a single device achieves process optimization.

[0118] In a specific embodiment of the present invention, the porous carbon support obtained in step (e) can be further crushed or pulverized and classified. Crushing or pulverizing can further refine the carbon support, and classification can ensure a uniform particle size distribution of the porous carbon support. Here, classification can be performed using dry classification, wet classification, or classification using a sieve, etc. Through crushing or pulverizing and classification, a porous carbon support powder with an average particle size (particle size distribution D50) of 1 to 20 µm, a BET specific surface area of ​​300 to 3,000 m² / g, and a bulk density of 0.05 to 0.5 g / mL can be obtained. Furthermore, based on the total pore volume, the volume ratio of mesopores with a pore size of 2 to 50 nm in this porous carbon support powder can be 10 to 80%.

[0119] On the other hand, if the asphalt does not need to be crushed separately in step (b) above, but is stabilized, carbonized and activated directly to produce a porous carbon carrier, the carbon carrier can be crushed (or further classified) to give it an average particle size of 1 to 20 µm (particle size distribution D50), but is not limited thereto.

[0120] If the carbon carrier is hard carbon, the hard carbon may include performing the following steps to obtain hard carbon: (a') thermally cracking and polycondensing petroleum-based feedstock to synthesize asphalt, (b') curing and granulating the asphalt to obtain granular asphalt, or curing, granulating and pulverizing the asphalt to obtain powdered asphalt, (c') stabilizing the granular or powdered asphalt, and (d') carbonizing the stabilized asphalt to obtain hard carbon.

[0121] At this time, since the explanation of steps (a') to (d') can be the same as that of steps (a) to (d), it will be explained in detail here.

[0122] On the other hand, the asphalt used to manufacture the hard carbon can be any one or more of isotropic asphalt and anisotropic asphalt, and is preferably isotropic asphalt, which is more conducive to achieving the purpose of the present invention.

[0123] If the carbon carrier is soft carbon, the soft carbon may include performing the following steps to obtain soft carbon: (a) thermally cracking and polycondensing petroleum-based feedstock to synthesize asphalt, (b) curing and granulating the asphalt to obtain granular asphalt, or curing, granulating and pulverizing the asphalt to obtain powdered asphalt, (c) stabilizing the granular or powdered asphalt, and (d) carbonizing the stabilized asphalt to obtain soft carbon.

[0124] At this point, since the explanation of step (a) and step (b) can be the same as that of step (a) and step (b), it will be explained in detail here.

[0125] Step (c) and step (d) described below can be performed in a rotary kiln as in step (c) and step (d), or they can be placed in a crucible and then placed in an oven to perform a series of steps. It is more advantageous to perform the series of steps by placing them in a crucible and then placing them in an oven.

[0126] On the other hand, since the explanation of the contents other than step (c) can be the same as the explanation of step (c), it will be explained in detail from now on.

[0127] In addition, step (d) is a step of carbonizing stabilized asphalt to obtain soft carbon. By carbonizing stabilized asphalt, other functional groups contained in asphalt can be removed, thereby obtaining soft carbon that is essentially composed of pure carbon.

[0128] In a specific embodiment of the present invention, the carbonization of step (d) can be carried out under an inert gas atmosphere. In a preferred embodiment of the present invention, the carbonization of step (d) can be carried out under a nitrogen or argon atmosphere, but is not particularly limited thereto.

[0129] In a specific embodiment of the present invention, the carbonization in step (d) can be carried out at a temperature of 1,000°C to 2,700°C, and preferably at a temperature of 1,200°C to 2,200°C. If the temperature is below this range when performing the carbonization in step (d), the carbonization may not be sufficient, and if the temperature is above this range, the carbonization yield may decrease.

[0130] In a specific embodiment of the present invention, the carbonization in step (d) can be performed under an inert gas flow rate of 0.1 to 30 ml / min, preferably under an inert gas flow rate of 0.1 to 10 ml / min, and more preferably under an argon flow rate. When the carbonization is performed under the inert gas flow rate, the stabilized asphalt can be fully carbonized.

[0131] In a specific embodiment of the present invention, the carbonization of step (d) can be performed over a period of 0.5 to 5 hours, preferably over a period of 1 to 3 hours. When the carbonization of step (d) is performed within this time, the stabilized asphalt can be fully carbonized.

[0132] On the other hand, since the explanation of the contents other than step (d) can be the same as the explanation of step (d), it will be explained in detail from now on.

[0133] On the other hand, the asphalt used to manufacture the soft carbon can be any one or more of isotropic asphalt and anisotropic asphalt, and is preferably anisotropic asphalt, which is more conducive to achieving the purpose of the present invention.

[0134] In an embodiment of the present invention, the carbon / silicon composite produced in the method for manufacturing the carbon / silicon composite can be crushed or pulverized and classified. By classification, the particle size distribution of the carbon / silicon composite can be made more uniform. Here, classification can be carried out by dry classification, wet classification, or classification using a sieve, etc.

[0135] Negative electrode active material

[0136] According to another embodiment of the present invention, a negative electrode active material comprising the carbon / silicon composite is provided.

[0137] According to embodiments of the present invention, in addition to the carbon / silicon composite, the negative electrode active material may also include a carbon-based negative electrode material, specifically, a graphite-based negative electrode material. For example, the negative electrode active material may be prepared by mixing the carbon / silicon composite according to embodiments of the present invention with a carbon-based negative electrode material, such as a graphite-based negative electrode material.

[0138] The carbon-based negative electrode material may include at least one of the group consisting of natural graphite, artificial graphite, soft carbon, hard carbon, mesophase carbon, carbon fiber, carbon nanotubes, thermally decomposed carbon, coke, sintered organic polymer compounds and carbon black, but is not particularly limited thereto.

[0139] According to an embodiment of the present invention, the content of carbon-based negative electrode material in the negative electrode active material can be 2 to 80% by weight relative to the total weight of the negative electrode active material, and preferably 5 to 70% by weight, more preferably 30 to 70% by weight.

[0140] According to embodiments of the present invention, the negative electrode active material can be effectively used to manufacture the negative electrode of a secondary battery. Specifically, it can be used to manufacture the negative electrode of a lithium secondary battery and the negative electrode of an all-solid-state battery.

[0141] All-solid-state battery

[0142] According to another embodiment of the present invention, an all-solid-state battery is provided, comprising: an SEI (Solid Electrolyte Interphase) film, the SEI film comprising a carbon / silicon composite.

[0143] The all-solid-state battery can be an all-solid-state battery comprising a positive electrode, a negative electrode and a solid electrolyte disposed between the positive electrode and the negative electrode. The negative electrode may comprise a negative electrode active material layer, and at least a portion of the negative electrode active material particles of the negative electrode active material layer may comprise the aforementioned SEI (Solid Electrolyte Interphase) film comprising a carbon / silicon composite.

[0144] On the other hand, the negative electrode active material particles can be carbon-based negative electrode materials. In this case, the description is the same as that for the negative electrode active material, so the relevant description will be omitted.

[0145] In addition, apart from the negative electrode active material particles and SEI film of the all-solid-state battery, the negative electrode structure, positive electrode structure and solid electrolyte structure can be applied to the structure of known all-solid-state batteries, so the present invention is not particularly limited thereto.

[0146] The present invention will be described in more detail below through embodiments. The following embodiments are for illustrative purposes only and are not intended to limit the scope of the present invention.

[0147] [Example]

[0148] [Preparation Example 1: Manufacturing of Porous Carbon Support]

[0149] 300 grams of petroleum-based residual oil (YNCC, HTC PFO (pyrolysis fuel oil)) was added to a reactor equipped with a stirrer, and a pyrolysis and polycondensation reaction was carried out at 450°C for 3 hours under a nitrogen supply flow rate of 100 ml / min. During this process, the stirrer was rotated at 200 rpm to mix the reactants. The polymerized asphalt was then cured and granulated to obtain solid asphalt particles with an average particle size (particle size distribution D50) of 1 to 30 mm.

[0150] The solid asphalt particles obtained above were crushed to obtain asphalt particles with an average particle size (particle size distribution D50) of 200µm. Then, they were fed into a rotary kiln with three sections for stabilization, carbonization and activation in sequence. The conditions for stabilization, carbonization and activation and the physical properties of the porous carbon support are shown in Table 1 below.

[0151] [Preparation Example 2: Manufacturing of Hard Carbon Carrier]

[0152] 300 grams of petroleum-based residual oil (YNCC, HTC PFO (pyrolysis fuel oil)) was added to a reactor equipped with a stirrer, and a pyrolysis and polycondensation reaction was carried out at 450°C for 3 hours under a nitrogen supply flow rate of 100 ml / min. During this process, the stirrer was rotated at 200 rpm to mix the reactants. The polymerized asphalt was then cured and granulated to obtain solid asphalt particles with an average particle size (particle size distribution D50) of 1 to 30 mm.

[0153] After crushing the solid asphalt particles obtained above (powdered asphalt), 100 grams were taken and put into a rotary kiln with two sections, and stabilization and carbonization were carried out in sequence. The stabilization and carbonization conditions and the physical properties of the carbon carrier (hard carbon) are shown in Table 1 below.

[0154] [Preparation Example 3: Manufacturing of Soft Carbon Carrier]

[0155] 300 grams of petroleum-based residual oil (YNCC, HTC PFO (pyrolysis fuel oil)) was added to a reactor equipped with a stirrer, and a pyrolysis and polycondensation reaction was carried out at 450°C for 3 hours under a nitrogen supply flow rate of 100 ml / min. During this process, the stirrer was rotated at 200 rpm to mix the reactants. The polymerized asphalt was then cured and granulated to obtain solid asphalt particles with an average particle size (particle size distribution D50) of 1 to 30 mm.

[0156] After crushing the solid asphalt particles obtained above (to form powdered asphalt), take 100 grams, place them in a crucible, and put them in an oven for stabilization and carbonization treatment. The stabilization and carbonization conditions and the physical properties of the carbon support (soft carbon) are shown in Table 1 below.

[0157] The specific surface area of ​​the carbon supports in Examples 1 to 3 was determined using a Belserp mini II according to ASTM D4820-93. Furthermore, the bulk density of the carbon supports was determined using a bulk density analyzer (Electrolab, ETD-1020x) according to ASTM B527. Additionally, the particle size distribution of the carbon supports was determined using a particle size analyzer (Horiba, laser particle analyzer, LA-960V2) according to ASTM E112. The results are shown in Table 1.

[0158] [Table 1] step condition Preparation Example 1 Preparation Example 2 Preparation Example 3 Stabilization Temperature (°C) 300 300 300 Time (hr) 3 3 3 atmosphere Air Air Air carbonization Temperature (°C) 900 900 1600 Time (hr) 1 1 1 atmosphere Nitrogen Nitrogen Argon activation Temperature (°C) 900 - - Time (hr) 3 - - Water vapor flow rate (ml / min) 200 - - Properties of carbon carriers Particle size distribution D50 (µm) 200 49.7 50.1 Specific surface area (m²) 2 / g) 1409.1 2 4 Bulk density (g / ml) 0.44 0.664 0.882

[0159] [Example 1: Manufacturing of carbon / silicon composite]

[0160] The porous carbon support of Preparation Example 1 was pulverized using a pulverizer (NETZSCH, airflow pulverizer) to obtain fine powder of the porous carbon support with a particle size distribution D50 of 7µm. Next, 15 grams of the fine powder of the porous carbon support was fed into a rotary kiln, and silane (SiH4) gas was injected to form a silicon layer on the porous carbon support, thereby manufacturing a composite. The silicon layer formation conditions and the physical properties of the carbon support after the silicon layer formation are shown in Table 2 below.

[0161] [Table 2] step condition Preparation Example 1 Silicon layer formation conditions Batch (g) 15 pressure Atmospheric pressure Temperature (°C) 475 Time (minutes) 120 Physical properties of the complex after the formation of silicon layers Particle size distribution D50 (µm) 8.9 Specific surface area (m²) 2 / g) 10.4 Bulk density (g / ml) 0.6

[0162] Subsequently, the composite is heat-treated in air at a temperature of 500°C for 1 hour to oxidize the Si-H bonds and dangling bonds on the silicon surface of the composite to produce a carbon / silicon composite.

[0163] [Examples 2 to 4]

[0164] The same procedure as in Example 1 was followed, except that the heat treatment temperature was changed from 500°C to 300°C (Example 2), 400°C (Example 3), and 650°C (Example 4) to prepare carbon / silicon composites.

[0165] [Comparative Example 1]

[0166] The carbon / silicon composite was prepared in the same manner as in Example 1, except that no heat treatment was performed.

[0167] [Experimental Example 1]

[0168] The thickness change due to gas generation was evaluated for the carbon / silicon composites according to Examples 1 to 4 and Comparative Example 1.

[0169] Specifically, as the positive electrode, a slurry containing 80 wt% positive electrode active material with the chemical formula LiNi0.8Mn0.1Co0.1O2, 10 wt% PAA binder, and 10 wt% carbon black, mixed with NMP solvent, is coated to a thickness of 40 µm onto an aluminum foil positive electrode current collector with a thickness of 12 nm and a purity of 99.99%. As the negative electrode, the carbon / silicon composite of Examples 1 to 4 and Comparative Example 1 is mixed as 96 wt% active material, 2 wt% CMC / SBR binder, and 2 wt% Super-P carbon black, respectively, and then mixed with Di... A water-dispersed slurry was coated to a thickness of 60µm, then vacuum-dried and rolled twice to create a negative electrode with an active material layer of 35µm thickness. A 12µm thick PE material was used as a separator between the two electrodes to cover all electrodes. Finally, 1.5ml of a mixed electrolyte (LiPF6 + EC:EMC:DEC = 3:5:2) + 5% FEC was injected into the battery, and it was encapsulated to manufacture a pouch cell. Furthermore, to evaluate electrochemical characteristics, a Neware BTS 4000 instrument was used to perform charge-discharge cycles at a current density of 0.3C at room temperature within a voltage range of 3.0V to 4.15V. Simultaneously, to measure the electrode volume expansion behavior, a high-precision on-site thickness measurement device with a thickness resolution of 0.01µm, an accuracy of ±0.1µm, and a pressure resolution of ±0.01kg was used. This measurement device was controlled and recorded using the GM5 (GaugeMonitor V5) program. The instantaneous expansion rate was measured in sync with the charge and discharge cycle, and data was collected at 1-second intervals. The thickness change was measured by calculating the average of the maximum thickness change in each cycle. The results are shown in Table 3 below.

[0170] [Table 3] distinguish Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Temperature (°C) 500 300 400 650 Unprocessed Thickness variation (mm) 0.01 0.05 0.02 0.07 0.05

[0171] As can be seen from Table 3 above, according to the present invention and satisfying the heat treatment temperature range, Examples 1 and 3, compared with Example 2 which does not reach the heat treatment temperature range, Example 4 which exceeds the temperature range, and Comparative Example 1 which does not undergo heat treatment, have significantly lower thickness changes because gas generation can be reduced.

[0172] [Example 4]

[0173] Based on the hard carbon support of Preparation Example 2, a pulverizer (NETZSCH, airflow pulverizer) was used to pulverize the carbon support to produce fine carbon support powder with a particle size distribution D50 of 4.9 µm. Furthermore, 15 g of the pulverized carbon support was fed into a rotary kiln, and silane (SiH₄) gas was injected to deposit silicon onto the soft carbon support, thereby creating a composite. The silicon deposition conditions and the physical properties of the composite are shown in Table 4 below.

[0174] Subsequently, the composite is heat-treated in an air atmosphere at a temperature of 300°C for 1 hour to oxidize the Si-H bonds and dangling bonds on the silicon surface of the composite to produce a carbon / silicon composite.

[0175] [Example 5]

[0176] Based on the soft carbon support of Preparation Example 3, a pulverizer (NETZSCH, airflow pulverizer) was used to pulverize the carbon support to produce fine carbon support powder with a particle size distribution D50 of 5.6 µm. Furthermore, 15 g of the pulverized carbon support was fed into a rotary kiln, and silane (SiH4) gas was injected to deposit silicon onto the soft carbon support to produce a composite. The silicon deposition conditions and the physical properties of the carbon composite are shown in Table 4 below.

[0177] Subsequently, the composite is heat-treated in an air atmosphere at a temperature of 300°C for 1 hour to oxidize the Si-H bonds and dangling bonds on the silicon surface of the composite, thereby producing a carbon / silicon composite.

[0178] [Table 4] distinguish condition Example 4 Example 5 Silicon deposition conditions pressure Atmospheric pressure Atmospheric pressure Temperature (°C) 475 475 Silane flow rate (sccm) 300 300 time 60 60 Complex Silicon content (by weight %) 34.9 31.4 Particle size distribution D50 (µm) 11.6 10.7 Specific surface area (m²) 2 / g) 0.5 1.4 Silicon layer thickness (nm) 84 111

[0179] An embodiment of the present invention has been described above, but the spirit of the present invention is not limited to the embodiment disclosed in this specification. Those skilled in the art can easily propose other embodiments by adding, changing, deleting, or adding constituent elements within the same spirit and scope, which should also fall within the spirit and scope of the present invention. [Simplified Explanation of the Diagram]

[0031] Figure 1 is a schematic diagram of removing the Si-H portion and dangling bond portion of the silicon surface of a carbon / silicon composite according to one embodiment of the present invention.

Claims

1. A carbon / silicon composite comprising: a carbon support; and a thin film of silicon, comprising silicon disposed on the surface of the carbon support; wherein, The Si-H bonds and dangling bonds on the silicon surface are at least partially oxidized, and the silicon accounts for 5 to 80% of the total weight of the carbon / silicon composite.

2. The carbon / silicon composite as described in claim 1, wherein, The carbon support includes a non-porous carbon support, which includes one or more of hard carbon and soft carbon.

3. The carbon / silicon composite as described in claim 1, wherein, The carbon support comprises a porous carbon support, and the silicon is disposed on the surface and inside the pores of the porous carbon support.

4. The carbon / silicon composite as described in claim 3, wherein, The porous carbon support has a total pore volume as a baseline and a mesopore volume ratio of 10% to 80% with a pore size of 2 to 50 nm.

5. The carbon / silicon composite as described in claim 3, wherein, The porous carbon support has a BET specific surface area of ​​300 to 3,000 m² / g, a bulk density of 0.05 to 0.5 g / ml, and a particle size distribution D50 of 1 to 20 µm.

6. A method for manufacturing a carbon / silicon composite, comprising the following steps: (1) forming a thin film of silicon on a surface containing a carbon support to manufacture the composite; and (2) at least partially oxidizing the Si-H bonds and dangling bonds on the silicon surface of the composite to manufacture the carbon / silicon composite, wherein, The silicon content is 5 to 80% of the total weight of the carbon / silicon composite.

7. The method for manufacturing a carbon / silicon composite as described in claim 6, wherein, Step (1) involves depositing silicon into the carbon support by chemical vapor deposition (CVD).

8. The method for manufacturing a carbon / silicon composite as described in claim 6, wherein, Step (2) is performed by treating the composite with O2 plasma.

9. The method for manufacturing a carbon / silicon composite as described in claim 8, wherein, The O2 plasma treatment is performed at an O2 gas flow rate of 10 to 100 sccm, a power of 50 to 200 W, and a time of 0.5 to 10 minutes.

10. The method for manufacturing a carbon / silicon composite as described in claim 6, wherein, Step (2) involves heat-treating the composite.

11. The method for manufacturing a carbon / silicon composite as described in claim 10, wherein, The heat treatment is carried out in an air atmosphere at a temperature of 350 to 600°C for 0.5 to 2 hours.

12. A negative electrode active material comprising: a carbon / silicon composite as described in any one of claims 1 to 5; and a carbon-based negative electrode material.

13. An all-solid-state battery comprising: an SEI (Solid Electrolyte Interphase) film comprising a carbon / silicon composite as described in any one of claims 1 to 5.

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