Carbon / silicon composite, preparation method therefor, anode active material comprising same, and all-solid-state battery

Abstract

The present invention relates to a carbon / silicon composite, a preparation method therefor, an anode active material comprising same, and an all-solid-state battery. The carbon / silicon composite according to an embodiment of the present invention can achieve the effects of: reducing gas generation according to the removal of Si-H portions and dangling bond portions on the surface of silicon; and improving initial coulombic efficiency (ICE) by a decreased side reaction with an electrolyte during the formation of an anode active material of a lithium secondary battery or a solid electrolyte interphase (SEI) of an all-solid-state battery.

Description

Carbon / silicon composite, method for manufacturing 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] With the recent development of the information and communication industry, demand for electronic devices has been rapidly increasing, and with the revitalization of the electric vehicle market, demand for batteries used in these electronic devices and electric vehicles has also increased significantly.

[0003] Secondary batteries, including lithium secondary batteries and all-solid-state batteries containing liquid electrolytes, are the most widely used for these applications due to their high energy density and minimal self-discharge when not in use. Secondary batteries generally consist of a positive electrode, a negative electrode, and an electrolyte (liquid or solid). Carbon-based materials such as graphite are widely used as the negative electrode active material.

[0004] Recently, attempts have been 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, it reacts with lithium during charging and discharging, increasing its volume by up to 300%. This causes the silicon anode material to fracture during charging and discharging, resulting in significantly reduced mechanical stability.

[0005] To solve these problems, Japanese Patent No. 4393610 discloses a negative electrode active material in which silicon is composited with carbon in a mechanical processing process and the surface of the silicon particles is covered with a carbon layer using a chemical vapor deposition (CVD) method. However, there is a limit to suppressing volume expansion and contraction during charge and discharge.

[0006] In addition, silicon-based negative electrode active materials have a problem in that the solid electrolyte interphase (SEI) layer that is excessively generated during the process of crushing and pulverizing silicon raw materials exhibits instability, which causes a decline in the stability and electrical performance of the battery.

[0007] The purpose of the present invention is to provide a carbon / silicon composite that can reduce gas generation by removing Si-H portions and dangling bond portions on the surface of the carbon / silicon composite, and can improve initial Coulombic efficiency (ICE) by reducing side reactions with electrolytes during formation of a negative electrode active material of a lithium secondary battery or a solid electrolyte interphase (SEI) of an all-solid-state battery.

[0008] Another object of the present invention is to provide a method for producing the carbon / silicon composite.

[0009] Another object of the present invention is to provide a negative electrode active material and an all-solid-state battery comprising the carbon / silicon composite.

[0010] In order to solve the above-described problem, the present invention provides a carbon / silicon composite including a carbon support and silicon arranged including a surface of the carbon support, wherein the silicon has at least a portion of Si-H bonds and dangling bonds on the surface oxidized.

[0011] 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.

[0012] Additionally, 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.

[0013] 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.

[0014] In addition, the porous carbon support may have a BET specific surface area of ​​300 to 3,000 m2 / g, a tap density of 0.05 to 0.5 g / ㎖, and a particle size distribution D50 of 1 to 20 ㎛.

[0015] Additionally, the silicon may be 5 to 80 wt% of the total weight of the carbon / silicon composite.

[0016]

[0017] In addition, the present invention provides a method for producing a carbon / silicon composite, comprising the steps of (1) producing a composite by forming silicon including the surface of a carbon support, and (2) producing a carbon / silicon composite by at least partially oxidizing Si-H bonds and dangling bonds of the silicon surface of the composite.

[0018] According to one embodiment of the present invention, the step (1) can be performed by applying a silicon source to the carbon support by chemical vapor deposition (CVD).

[0019] Additionally, the above step (2) can be performed by treating the complex with O2 plasma.

[0020] In addition, the above O2 plasma treatment can be performed under the condition of a flow rate of 10 to 100 sccm O2 gas, a power condition of 50 to 200 W, and a time condition of 0.5 to 10 min.

[0021] Additionally, the above step (2) can be performed by heat treating the complex.

[0022] Additionally, the above heat treatment can be performed by heat treatment in an air atmosphere at a temperature of 350 to 600°C for 0.5 to 2 hours.

[0023]

[0024] In addition, the present invention provides a negative electrode active material comprising the above-described carbon / silicon composite and a carbon-based negative electrode material.

[0025]

[0026] In addition, the present invention provides an all-solid-state battery including a SEI (Solid Electrolyte Interphase) film including the above-described carbon / silicon composite.

[0027] The carbon / silicon composite according to an embodiment of the present invention can reduce gas generation by removing the Si-H portion and dangling bond portion of the silicon surface, and can exhibit an effect of improving the initial coulombic efficiency (ICE) by reducing side reactions with the electrolyte when forming the negative active material of a lithium secondary battery or the solid electrolyte interphase (SEI) of an all-solid-state battery.

[0028] FIG. 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.

[0029] 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.

[0030] As used herein, the term “comprising” means that other components may be included unless otherwise stated.

[0031] 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.

[0032] In this specification, the description that one component is formed above / below another component or is connected or coupled to each other includes both the formation, connection or coupling between these components directly or indirectly through another component.

[0033] The present invention will be described in more detail below.

[0034] carbon / silicon composite

[0035] According to one embodiment of the present invention, a carbon / silicon composite is provided, which comprises a carbon support and silicon disposed on a surface of the carbon support, wherein the silicon has at least a portion of Si-H bonds and dangling bonds on the surface oxidized.

[0036] 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 50 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.

[0037] In addition, the carbon / silicon composite of the present invention can reduce gas generation by at least partially oxidizing Si-H bonds and dangling bonds on the silicon surface, and can be more advantageous in terms of improving the initial Coulombic efficiency (ICE) by reducing side reactions with the electrolyte when forming the negative active material of a lithium secondary battery or the solid electrolyte interphase (SEI) of an all-solid-state battery.

[0038] Hereinafter, each component of a carbon / silicon composite according to one embodiment of the present invention will be described.

[0039] carbon support

[0040] A carbon / silicon composite according to an embodiment of the present invention comprises a carbon support.

[0041] 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.

[0042] According to one embodiment of the present invention, the carbon support may be a porous carbon support, and in this case, the silicon may be disposed on the surface and inside the pores of the porous carbon support.

[0043] The porous carbon support 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 and relatively large numbers may be formed on the outside of the silicon, and if the volume ratio of the mesopores of the porous carbon support exceeds 80%, the hardness of the particles is insufficient, and there is a concern that the structure of the electrode may collapse when the electrode is manufactured using the same.

[0044] In addition, 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, 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 a lack of 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 number may be formed on the outside of the silicon.

[0045] In addition, the porous carbon support may have a tap density of 0.05 to 0.5 g / ml. Preferably, the porous carbon support may have a tap density of 0.05 to 0.45 g / ml, more preferably, a tap density of 0.1 to 0.45 g / ml. When the tap density of the porous carbon support is less than 0.05 g / ml, process control may be difficult during deposition of the silicon source, which may result in a decrease in yield, and when the tap density of the porous carbon support exceeds 0.5 g / ml, uniform formation may be difficult during deposition of the silicon source.

[0046] And, the porous carbon support may have a particle size distribution D50 of 1 to 20 ㎛. Preferably, the porous carbon support may have a particle size distribution D50 of 3 to 20 ㎛, more preferably, a particle size distribution D50 of 3 to 10 ㎛. When the particle size distribution D50 of the porous carbon support is less than 1 ㎛, the silicon source cannot sufficiently penetrate into the pores and is formed in large quantities only on the outside of the particles, and when the particle size distribution D50 of the porous carbon support exceeds 20 ㎛, it is difficult for silicon to be sufficiently formed in the pores.

[0047] When a carbon / silicon composite according to an embodiment of the present invention includes a porous carbon support having the above characteristics, when such a carbon / silicon composite is used as a negative electrode active material, it has excellent electrical conductivity and can relieve stress caused by volume expansion of silicon.

[0048] silicone

[0049] A carbon / silicon composite according to an embodiment of the present invention comprises silicon disposed including the surface of the carbon support.

[0050] By arranging the carbon support and silicon in the carbon / silicon composite according to the present invention as described above, the negative electrode material manufactured from the carbon / silicon composite according to the present invention can have a high electrical capacity while minimizing the influence due to volume expansion of silicon.

[0051] At this time, since the silicon plays a role in charging lithium, when the carbon / silicon composite according to the embodiment of the present invention is used as a negative electrode active material, the silicon can act as a main negative electrode active material.

[0052] Meanwhile, the silicon has at least some oxidized Si-H bonds and dangling bonds on its surface, and thus can reduce gas generation and be more advantageous in terms of improving the initial Coulombic efficiency (ICE) to the level of the negative active material of a lithium secondary battery or the solid electrolyte interphase (SEI) formation of an all-solid-state battery.

[0053] The silicon may be crystalline or amorphous, and preferably amorphous or amorphous in nature. If the silicon is crystalline, the smaller the crystallite size, the more dense the composite can be, thereby enhancing strength and preventing cracks. Accordingly, the initial efficiency or cycle life characteristics of the secondary battery can be improved. On the other hand, if the silicon is amorphous or amorphous in nature, the expansion or contraction during charge and discharge of the secondary battery is small, and battery performance such as capacity characteristics can be improved.

[0054] The above silicon may be in the form of a thin film, and the average layer thickness of the silicon may be 10 nm to 5 μm. If the average layer thickness of the silicon is less than 10 nm, the electric capacity may be reduced, and if the average thickness exceeds 5 μm, the problem caused by volume expansion of the silicon may not be resolved, which may cause structural damage to the negative electrode material and deteriorate the cycle characteristics.

[0055] In addition, the silicon may be 5 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 is less than 5 wt% of the total weight of the carbon / silicon composite, the electric capacity may decrease, and if the silicon is more than 80 wt%, the problem caused by the 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.

[0056] The above silicon 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.

[0057] The content of the silicon oxide compound in the silicon 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.

[0058]

[0059] Method for manufacturing carbon / silicon composites

[0060] A carbon / silicon composite according to one embodiment of the present invention is manufactured by a manufacturing method including the steps of (1) manufacturing a composite by forming silicon including the surface of a carbon support, and (2) manufacturing a carbon / silicon composite by at least partially oxidizing Si-H bonds and dangling bonds of the silicon surface of the composite.

[0061] Hereinafter, each step of a method for manufacturing a carbon-silicon composite according to one embodiment of the present invention will be described.

[0062] (1) Step

[0063] In step (1) above, a composite is manufactured by forming silicon including the surface of a carbon support.

[0064] Meanwhile, if the carbon support is a porous carbon support, the step (1) may be a step of manufacturing a carbon / silicon composite by forming it on the surface and inside the pores of the porous carbon support.

[0065] In a specific embodiment of the present invention, the step of forming silicon including the surface of a carbon support may be performed using a device (e.g., a rotary kiln) and a method (e.g., chemical vapor deposition (CVD)) known in the art to which the present invention pertains. Specifically, silicon including the surface of the carbon support may be formed by supplying a silicon source to the carbon support and performing CVD.

[0066] 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.

[0067] 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.

[0068] (2) Step

[0069] In step (2) above, a carbon / silicon composite is manufactured by at least partially oxidizing the Si-H bonds and dangling bonds on the silicon surface of the composite.

[0070] 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 complex can be performed by treating the complex with O2 plasma.

[0071] The above O2 plasma treatment can be performed under the conditions of a flow rate of 10 to 100 sccm of O2 gas, a power condition of 50 to 200 W, and a time condition of 0.5 to 10 min. By satisfying the flow rate, power, and time conditions of the O2 plasma, it can be more advantageous to achieve the purpose of the present invention.

[0072] In another embodiment of the present invention, the step of at least partially oxidizing the Si-H bonds and dangling bonds of the silicon surface of the complex can be performed by heat treating the complex.

[0073] The above heat treatment can be performed by heat treatment in an air atmosphere at a temperature of 350 to 600°C for 0.5 to 2 hours, and preferably by heat treatment in an air atmosphere at a temperature of 400 to 500°C for 0.5 to 1.5 hours. By satisfying the temperature and time conditions of the above heat treatment, it can be more advantageous in achieving the purpose of the present invention, such as by reducing gas generation.

[0074]

[0075] Preliminary stage

[0076] 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.

[0077] When the carbon support is a porous carbon support, the method for producing the carbon / silicon composite may further include, before step (1), (a) a step of synthesizing pitch by thermal decomposition and condensation polymerization of a petroleum-based raw material, (b) a step of solidifying and pelletizing the pitch to obtain a pellet-like pitch or a step of solidifying, pelletizing, and pulverizing the pitch to obtain a powder-like pitch, (c) a step of stabilizing the pellet-like pitch or the powder-like pitch, (d) a step of carbonizing the stabilized pitch to obtain a carbonized body, and (e) a step of activating the carbonized body to obtain a porous carbon support.

[0078] In the above step (a), pitch can be synthesized by thermal decomposition and polycondensation of petroleum-based raw materials.

[0079] 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.

[0080] 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.

[0081] 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.

[0082] 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 (e) 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.

[0083] 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.

[0084] 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.

[0085] 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.

[0086] 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.

[0087] 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.

[0088] In a specific embodiment of the present invention, the pitch synthesized in step (a) 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.

[0089] In a specific embodiment of the present invention, the yield of the pitch synthesized in step (a) 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%.

[0090] In a specific embodiment of the present invention, a step of pretreating the petroleum-based raw material may be performed prior to step (a). 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.

[0091] 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 (a), 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.

[0092] 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 (a), 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.

[0093] Additionally, in the step (b), the pitch may be solidified and pelletized to obtain a pellet-like pitch, or the pitch may be solidified, pelletized, and pulverized to obtain a powder-like pitch.

[0094] First, in the case of the pellet-shaped pitch, the liquid pitch obtained in step (a) is solidified, for example, by extrusion and cooling, and then pelletized into a desired size to obtain solid pitch pellets (pellet-shaped pitch). The process of extruding, cooling, and pelletizing the liquid pitch to obtain solid pitch pellets 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.

[0095] The pitch pellets obtained in step (b) 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.

[0096] 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.

[0097] And, in step (c), a step of stabilizing the pellet-shaped pitch or powder-shaped pitch can be performed.

[0098] First, the pitch of the pitch pellet obtained in step (b) is first oxidized to stabilize the carbon structure of the pitch.

[0099] 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.

[0100] 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.

[0101] 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 pellet-shaped pitch or the carbon inside the powder-shaped pitch can be sufficiently stabilized.

[0102] 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.

[0103] 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.

[0104] And, in step (d), 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.

[0105] 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.

[0106] 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 the carbonization 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.

[0107] 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.

[0108] In a specific embodiment of the present invention, the carbonization may be performed for 0.5 to 5 hours, preferably 1 to 3 hours. If the carbonization is performed for this period of time, the stabilized pitch can be sufficiently carbonized.

[0109] And, in step (e), 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.

[0110] 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.

[0111] 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.

[0112] 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.

[0113] 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.

[0114] 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.

[0115] In a specific embodiment of the present invention, the stabilization, carbonization, and activation of steps (c) to (e) above can each be performed in a microwave-assisted heating furnace. In a preferred embodiment of the present invention, the stabilization, carbonization, and activation of steps (c) to (e) above can all be performed in a microwave-assisted heating furnace. A microwave-assisted heating furnace 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.

[0116] In a specific embodiment of the present invention, the stabilization, carbonization, and activation of steps (c) to (e) above can be performed continuously in a single device. In a preferred embodiment of the present invention, the stabilization, carbonization, and activation of steps (c) to (e) above can be performed continuously in a single rotary kiln, but the device is not particularly limited thereto. By performing the stabilization, carbonization, and activation of steps (c) to (e) above continuously in a single device, optimization of the process can be achieved.

[0117] In a specific embodiment of the present invention, the porous carbon support obtained in step (e) can be further pulverized or ground and classified. The porous carbon support can be further finely divided through pulverization or ground, 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 ground and classification treatment, a porous carbon support powder having an average particle diameter (particle size distribution D50) of 1 to 20 ㎛, 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%.

[0118] 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 (b), the carbon support may be pulverized (or further classified) to have an average particle size of 1 to 20 ㎛ (particle size distribution D50), but is not limited thereto.

[0119]

[0120] In addition, when the carbon support is hard carbon, the hard carbon can be manufactured by a method including the steps of (a') synthesizing pitch by thermal decomposition and condensation polymerization of petroleum-based raw materials, (b') solidifying and pelletizing the pitch to obtain pellet-like pitch, or solidifying, pelletizing, and pulverizing the pitch to obtain powder-like pitch, (c') stabilizing the pellet-like pitch or powder-like pitch, and (d') carbonizing the stabilized pitch to obtain hard carbon.

[0121] At this time, since the description of the above steps (a') to (d') may be the same as the description of the above steps (a) to (d), a detailed description will be omitted.

[0122] 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.

[0123]

[0124] In addition, when the carbon support is soft carbon, the soft carbon can be manufactured by a method including the steps of (a) synthesizing pitch by thermal decomposition and condensation polymerization of a petroleum-based raw material, (b) solidifying and pelletizing the pitch to obtain a pellet-like pitch, or solidifying, pelletizing, and pulverizing the pitch to obtain a powder-like pitch, (c) stabilizing the pellet-like pitch or the powder-like pitch, and (d) carbonizing the stabilized pitch to obtain soft carbon.

[0125] At this time, since the description of the above steps (a”) and (b”) may be the same as the description of the above steps (a) and (b), a detailed description thereof will be omitted.

[0126] The above step (c”) and the step (d”) described below may be performed as a series of steps in a rotary kiln, as in the above-described steps (c) and (d), or may be performed as a series of steps by placing the product in a crucible and placing it in an oven. Preferably, it may be advantageous for achieving the purpose of the present invention to perform the series of steps by placing the product in a crucible and placing it in an oven.

[0127] Meanwhile, since the description of the contents other than the above step (c”) may be the same as the description of the above step (c), a detailed description will be omitted.

[0128] In addition, the above step (d”) 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.

[0129] In a specific embodiment of the present invention, the carbonization in step (d”) may be performed under an inert gas atmosphere. In a preferred embodiment of the present invention, the carbonization in step (d”) may be performed under a nitrogen or argon atmosphere, but is not particularly limited thereto.

[0130] In a specific embodiment of the present invention, the carbonization in step (d”) 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 (d”) 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.

[0131] In a specific embodiment of the present invention, the carbonization in step (d”) may be performed under a flow rate 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 rate condition, the stabilized pitch can be sufficiently carbonized.

[0132] In a specific example of the present invention, the carbonization in step (d”) may be performed for 0.5 to 5 hours, preferably 1 to 3 hours. When the carbonization in step (d”) is performed for this period of time, the stabilized pitch can be sufficiently carbonized.

[0133] Meanwhile, since the description of the contents other than the above step (d”) may be the same as the description of the above step (d), a detailed description will be omitted.

[0134] 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.

[0135]

[0136] In a method for manufacturing a carbon / silicon composite according to an embodiment of the present invention, the obtained carbon / silicon composite may be crushed or ground and classified. Classification can achieve a uniform particle size distribution of the carbon / silicon composite. Here, classification may be performed by dry classification, wet classification, or classification using a sieve.

[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 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, for example, a graphite-based negative electrode material.

[0141] 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.

[0142] 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.

[0143] 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.

[0144]

[0145] All-solid-state batteries

[0146] According to another embodiment of the present invention, an all-solid-state battery is provided comprising a solid electrolyte interphase (SEI) film including the carbon / silicon composite.

[0147] 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 a solid electrolyte interphase (SEI) film including the carbon / silicon composite described above on at least a portion of the negative electrode active material particles of the negative electrode active material layer.

[0148] 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.

[0149] In addition, in addition to the negative active material particles and SEI film of the above-mentioned all-solid-state battery, the negative electrode configuration, positive electrode configuration, and solid electrolyte configuration can be applied to known all-solid-state battery configurations, and thus the present invention does not specifically limit them.

[0150] 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.

[0151] [Example]

[0152] <Preparation Example 1: Preparation of a Porous Carbon Support>

[0153] 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.

[0154] 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, and the physical properties of the porous carbon support are as shown in Table 1 below.

[0155]

[0156] <Preparation Example 2: Preparation of Hard Carbon Support>

[0157] 300 g of petroleum residual oil (YNCC, HTC PFO (pyrolysis fuel oil)) was introduced into 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 to 30 mm.

[0158] 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 conditions for stabilization and carbonization, and the properties of the carbon support (hard carbon) are as shown in Table 1 below.

[0159]

[0160] <Preparation Example 3: Manufacturing of Soft Carbon Support>

[0161] 300 g of petroleum residual oil (YNCC, HTC PFO (pyrolysis fuel oil)) was introduced into 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 to 30 mm.

[0162] 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 1 below.

[0163]

[0164] The specific surface areas of the carbon supports of Preparation Examples 1 to 3 were measured using a Belsorp mini II according to ASTM D4820-93. In addition, the tap density of the carbon supports was measured using a tap density analyzer (Electrolab, ETD-1020x) according to ASTM B527. In addition, the particle size distribution of the carbon supports was measured using a particle size analyzer (Horiba, laser particle analyzer, LA-960V2) according to ASTM E112. The results are shown in Table 1.

[0165] Step Condition Preparation Example 1 Preparation Example 2 Preparation Example 3 Stabilization temperature (℃) 300 300 300 Hours (hr) 333 Atmosphere Air Air Air Carbonization temperature (℃) 900 900 1600 Hours (hr) 111 Atmosphere Nitrogen Nitrogen Argon Activation temperature (℃) 900--Time (hr) 3--Water vapor flow rate (㎖ / min) 200--Carbon support Physical properties Particle size distribution D50 (㎛) 200 49.75 0.1 Specific surface area (㎡ / g) 1409.124 Tap density (g / ㎖) 0.44 0.66 40.882

[0166]

[0167] <Example 1: Preparation of carbon / silicon composite>

[0168] The porous carbon support of Preparation Example 1 was pulverized with a pulverizer (NETZSCH, Air Jet Mill) to obtain a fine powder of the porous carbon support with a particle size distribution D50 of 7 ㎛. 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 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.

[0169] Step Condition Preparation Example 1 Silicon layer formation conditions Batch (g) 15 Pressure Normal pressure Temperature (℃) 475 Time (min) 120 After silicon layer formation Composite properties Particle size distribution D50 (㎛) 8.9 Specific surface area (㎡ / g) 10.4 Tap density (g / ㎖) 0.6

[0170]

[0171] Thereafter, the composite was heat-treated in an air atmosphere 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, thereby producing a carbon / silicon composite.

[0172]

[0173] <Examples 2 to 4>

[0174] Carbon / silicon composites were manufactured by performing the same procedure as in Example 1, but changing the heat treatment temperature from 500°C to 300°C (Example 2), 400°C (Example 3), and 650°C (Example 4).

[0175]

[0176] <Comparative Example 1>

[0177] A carbon / silicon composite was manufactured in the same manner as in Example 1 above, but without performing heat treatment.

[0178]

[0179] Experimental Example 1

[0180] The thickness change according to gas generation was evaluated for the carbon / silicon composites according to Examples 1 to 4 and Comparative Example 1.

[0181] Specifically, the anode current collector is a 99.99% aluminum foil with a thickness of 12 nm with the chemical formula LiNi. 0.8 Mn 0.1 Co 0.1 A slurry containing 80 wt% of a cathode active material having O₂, 10 wt% of a PAA binder, and 10 wt% of carbon black mixed in an NMP solvent was coated to a thickness of 40 μm, and a slurry containing 96 wt% of the active material, 2 wt% of a CMC / SBR binder, and 2 wt% of Super-P carbon black dispersed in Di Water, each of the carbon / silicon composites according to Examples 1 to 4 and Comparative Example 1, was applied to a thickness of 60 μm as an anode, followed by vacuum drying and rolling twice to manufacture a cathode having an active material layer with a thickness of 35 μm. Then, a PE material with a thickness of 12 μm was placed between the two electrodes so as to cover both electrodes, and then 1.5 ml of a mixed electrolyte of LiPF6+ EC:EMC:DEC (= 3:5:2) + FEC 5% was injected inside the cell and sealed to manufacture a pouch cell. And, to evaluate the electrochemical characteristics, charge and discharge cycling was performed at room temperature at a current density of 0.3C in the voltage range of 3.0 V to 4.15 V using a Neware BTS 4000 equipment. At the same time, to measure the volume expansion behavior of the electrode, a high-precision on-site thickness measurement device with a thickness detection resolution of 0.01 ㎛, an accuracy of ±0.1 ㎛, and a pressure resolution of ±0.01 kg was used, and the measurement device was controlled and recorded through the GM5 (GaugeMonitor V5) program. The real-time expansion rate was measured in synchronization with the charge and discharge, and the data were collected at 1-second intervals. The thickness change was measured by calculating the average value of the maximum thickness change for each cycle. The results are shown in Table 3 below.

[0182] Classification Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Heat treatment temperature (℃) 500 300 400 650 Untreated thickness change (mm) 0.01 0.05 0.02 0.07 0.05

[0183]

[0184] As can be seen from Table 3 above, Examples 1 and 3, which satisfy the heat treatment temperature range according to the present invention, were able to reduce gas generation compared to Example 2, which is below the heat treatment temperature range, Example 4, which is above the temperature range, and Comparative Example 1, which does not perform heat treatment, and thus it was confirmed that the thickness change was significantly lower.

[0185]

[0186] <Example 4>

[0187] The hard carbon support according to Preparation Example 2 was pulverized using a pulverizer (NETZSCH, Air Jet Mill) to produce fine powder of the carbon support with a particle size distribution D50 of 4.9 μm. Then, 15 g of the pulverized carbon support was placed in a rotary kiln, and silane (SiH4) gas was injected to deposit silicon on the hard carbon support to produce a composite. The silicon deposition conditions and the physical properties of the composite are shown in Table 4 below.

[0188] Thereafter, the above complex was 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 complex, thereby producing a carbon / silicon composite.

[0189]

[0190] <Example 5>

[0191] The soft carbon support according to Preparation Example 3 was pulverized using a pulverizer (NETZSCH, Air Jet Mill) to produce fine powder of the carbon support with a particle size distribution D50 of 5.6 μm. Then, 15 g of the pulverized carbon support was placed in a rotary kiln, and silane (SiH4) gas was injected to deposit silicon on the soft carbon support to produce a composite. The silicon deposition conditions and the physical properties of the composite are shown in Table 4 below.

[0192] Thereafter, the above complex was 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 complex, thereby producing a carbon / silicon composite.

[0193] Conditions for classificationExample 4Example 5Silicon deposition conditionsPressureAtmospheric pressureAtmospheric pressureTemperature (℃)475475Silane flow rate (sccm)300300Hour6060Composite silicon content (wt%)34.931.4Particle size distribution D50 (㎛)11.610.7Specific surface area (㎡ / g)0.51.4Silicon layer thickness (nm)84111

[0194]

[0195] 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. Carbon support; and Contains silicon arranged including the surface of the above carbon support; The above silicon is a carbon / silicon composite in which at least some of the Si-H bonds and dangling bonds on the surface are oxidized.

2. In paragraph 1, A carbon / silicon composite, wherein the carbon support comprises a non-porous carbon support comprising at least one of hard carbon and soft carbon.

3. In paragraph 1, The above carbon support comprises a porous carbon support, A carbon / silicon composite wherein the silicon is disposed on the surface and inside the pores of the porous carbon support.

4. In paragraph 3, 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.

5. In paragraph 3, The above porous carbon support is a carbon / silicon composite having a BET specific surface area of ​​300 to 3,000 m2 / g, a tap density of 0.05 to 0.5 g / ㎖, and a particle size distribution D50 of 1 to 20 ㎛.

6. In paragraph 1, A carbon / silicon composite, wherein the silicon is 5 to 80 wt% of the total weight of the carbon / silicon composite. 7.(1) A step of manufacturing a composite by forming silicon including the surface of a carbon support; and (2) A method for producing a carbon / silicon composite, comprising: a step of producing a carbon / silicon composite by at least partially oxidizing Si-H bonds and dangling bonds on the silicon surface of the composite; 8. In paragraph 7, The above step (1) is a method for manufacturing a carbon / silicon composite, which is performed by chemical vapor deposition (CVD) of a silicon source on the carbon support.

9. In paragraph 7, The above step (2) is a method for manufacturing a carbon / silicon composite, which is performed by treating the composite with O2 plasma.

10. In paragraph 9, A method for manufacturing a carbon / silicon composite, wherein the above O2 plasma treatment is performed under conditions of a flow rate of 10 to 100 sccm O2 gas, a power condition of 50 to 200 W, and a time condition of 0.5 to 10 min.

11. In paragraph 7, The above step (2) is a method for manufacturing a carbon / silicon composite, which is performed by heat-treating the composite.

12. In paragraph 11, A method for manufacturing a carbon / silicon composite, wherein the above heat treatment is performed in an air atmosphere at a temperature of 350 to 600°C for 0.5 to 2 hours.

13. A carbon / silicon composite according to any one of claims 1 to 6; and A negative electrode active material comprising a carbon-based negative electrode material.

14. An all-solid-state battery comprising a SEI (Solid Electrolyte Interphase) film comprising a carbon / silicon composite according to any one of claims 1 to 6.

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