Low-expansion silicon-carbon composite with improved electrical conductivity, method for manufacturing same, negative electrode material including same, and lithium ion battery and all-solid-state battery including same

Abstract

The present invention relates to a silicon-carbon composite used as a negative electrode material of a secondary battery, a method for manufacturing same, and a negative electrode material using same. More specifically, the present invention relates to a low-expansion silicon-carbon composite, a method for manufacturing same, and a negative electrode material using same, wherein a carbon coating layer is formed on the surface of carbon-silicon composite particles to minimize a volume increase of the composite when the composite is applied as an anode material of a secondary battery, thereby increasing long-term stability, and electrical conductivity is improved by doping a heterogeneous element into the carbon coating layer of the composite.

Description

Low-expansion silicon-carbon composite with improved electrical conductivity, method for producing the same, and anode material comprising the same, lithium-ion battery and all-solid-state battery comprising the same

[0001] The present invention relates to a low-expansion silicon-carbon composite that minimizes volume expansion and side reactions with electrolyte components by forming a carbon coating layer while minimizing volume expansion and side reactions with electrolyte components in an anode material of a lithium-ion battery and / or an all-solid-state battery due to repeated operation of the battery, and improves the problem of reduced electrical conductivity due to the formation of a carbon coating layer, a method for producing the same, an anode material comprising the same, and a lithium-ion battery and an all-solid-state battery comprising the same.

[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 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 silicon, one of the anode components, to fragment during charging and discharging, resulting in significantly reduced mechanical stability.

[0005] Additionally, the introduction of carbon materials as a support for the above silicon-based negative electrode material is being attempted and developed.

[0006] Carbon materials are materials composed of carbon, one of the most abundant resources on Earth. Carbon materials are extremely lightweight, strong, and possess excellent electrical and thermal conductivity, making them a key material widely used in fields such as hydrogen vehicles, aviation, secondary batteries, and high-end consumer goods. Carbon materials can be manufactured from a variety of raw materials, including coconut shells, polyacrylonitrile, rayon, and pitch. However, carbon materials manufactured from solid raw materials like coconut shells are difficult to control in terms of molecular weight and composition (Korean Patent Application Publication No. 10-2019-0093960).

[0007] On the other hand, pitch, a viscoelastic solid polymer extracted from crude oil or plants, has the advantages of high yield when converted into carbon materials, low cost of raw materials, and its molecular structure is closer to the graphite structure than other raw materials, which can reduce the energy required for heat treatment (U.S. Patent Nos. 4,242,196 and 4,340,464).

[0008] In particular, pyrolysis fuel oil (PFO), naphtha cracking bottom oil (NCB), vacuum residue (VR), and fluid catalytic cracking decant oil (FCC-DO), which are obtained as by-products in the petroleum refining process, have a high content of aromatic compounds and a low content of impurities such as sulfur and nitrogen, and therefore pitch manufactured from them is attracting attention as a material for carbon materials.

[0009] However, carbon supports based on pitch derived from fuel oil (PFO) have a relatively high content of metal impurities, making them unsuitable for use as anode materials in secondary batteries. If these residual metal impurities are high, they can react with the electrolyte of a secondary battery to generate gases, increasing the risk of fire and explosion. Furthermore, various chemical side reactions caused by the metal impurities can increase the irreversible capacity, thereby reducing charge-discharge efficiency. Consequently, their application as anode materials in secondary batteries is limited.

[0010] The negative electrode material of a lithium-ion battery and / or an all-solid-state battery has a problem in that volume expansion occurs due to lithium ions being inserted into the negative electrode material by repeated operation of the battery, and the lifespan of the battery is shortened due to side reactions with the electrolyte components. The present invention aims to provide a silicon-carbon composite that achieves minimization of volume expansion and side reactions by forming a carbon-silicon composite particle and a specific carbon coating layer on the surface of the composite particle with an optimal thickness so as to minimize such volume expansion and side reactions, and improves electrical conductivity lowered by the carbon coating layer, a method for manufacturing the same, an negative electrode material using the same, and a lithium-ion battery and / or an all-solid-state battery to which the negative electrode material is applied.

[0011] In order to solve the above problem, the present invention provides a low-expansion silicon-carbon composite with improved electrical conductivity, characterized in that the carbon-silicon composite particle has a carbon coating layer doped with a heterogeneous element formed on the outermost surface of the carbon-silicon composite particle, the carbon-silicon composite particle includes a carbon support including a surface portion and a core portion, and silicon (Si) arranged including the surface of the carbon support, and the heterogeneous element includes nitrogen (N) or nitrogen and boron (B).

[0012] As a preferred embodiment of the present invention, the carbon coating layer includes a carbide of a coating agent including a heterogeneous element doping agent and pitch, and the heterogeneous element doping agent may include a nitrogen precursor, or a nitrogen precursor and a boron precursor.

[0013] As a preferred embodiment of the present invention, the nitrogen precursor may include at least one selected from melamine, NH3, dopamine, and hexamethylenetetramine.

[0014] As a preferred embodiment of the present invention, the boron precursor may include at least one selected from boric acid, boron oxide, and phenylboronic acid.

[0015] As a preferred embodiment of the present invention, the pitch may be manufactured based on petroleum residue.

[0016] As a preferred embodiment of the present invention, the carbon coating layer may have an average thickness of 10 to 190 nm.

[0017] As a preferred embodiment of the present invention, the carbon coating layer doped with the heterogeneous element of the silicon-carbon composite of the present invention can have a heterogeneous element content that satisfies the following equation 1 or equation 2 when analyzed by XPS.

[0018] [Formula 1]

[0019] 0.2% ≤ (A / C)×100(%) ≤ 2%

[0020] In Equation 1, A is the atomic% value of nitrogen (N) in the carbon support analyzed by XPS, and C is the atomic% value of carbon (C) in the carbon support analyzed by XPS.

[0021] [Formula 2]

[0022] 0.2% ≤ ((A+B) / C)×100(%) ≤ 2%

[0023] In Equation 2, A is the atomic% value of nitrogen (N) in the carbon support analyzed by XPS, B is the atomic% value of boron (B), and C is the atomic% value of carbon (C) in the carbon support analyzed by XPS.

[0024] As a preferred 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.

[0025] As a preferred embodiment of the present invention, 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.

[0026] As a preferred embodiment of the present invention, the porous carbon support includes mesopores having a diameter of 2 nm to 50 nm, and the ratio of the volume of the mesopores of the surface layer to the volume of the entire mesopores of the porous carbon support may be 0.5 to 0.76.

[0027] As a preferred embodiment of the present invention, the porous carbon support may have a ratio of the volume of mesopores to the volume of the total pores of 0.1 or more.

[0028] As a preferred embodiment of the present invention, the porous carbon support may have a surface porosity greater than a deep porosity.

[0029] As a preferred embodiment of the present invention, the low-expansion silicon-carbon composite of the present invention can satisfy a volume expansion reduction rate of 100% or less calculated based on the following equation 3.

[0030] [Formula 3]

[0031] Volume expansion reduction rate (%) = {(DE) / D} × 100(%)

[0032] In Equation 3, D is the volume of the carbon-silicon composite particles without a carbon coating layer, E is the volume of the low-expansion silicon-carbon composite doped with a heterogeneous element, and the volumes of D and E are the volumes of the negative electrode materials measured after the carbon-silicon composite particles without a carbon coating layer and the low-expansion silicon-carbon composite doped with a heterogeneous element were applied as negative electrode materials for a half-cell for a lithium-ion battery, respectively, and the half-cell was operated for 50 cycles. At this time, the negative electrode materials of the carbon-silicon composite particles without a carbon coating layer and the low-expansion silicon-carbon composite doped with a heterogeneous element have the same size before the half-cell operation.

[0033] As a preferred embodiment of the present invention, in the silicon-carbon composite of the present invention, the change rate (%) of the fluorine atom content in the negative electrode material measured by the volume expansion reduction rate can satisfy the following equation 4.

[0034] [Formula 4]

[0035] 5% ≤ {(HG) / G}×100(%) ≤20%

[0036] In Equation 4, G is the fluorine (F) content (in wt%) in the surface of the negative electrode material manufactured from carbon-silicon composite particles without a carbon coating layer for which the volume expansion reduction rate was measured, and H is the fluorine content (in wt%) in the surface of the negative electrode material manufactured from a low-expansion silicon-carbon composite doped with a heterogeneous element for which the volume expansion reduction rate was measured.

[0037]

[0038] In addition, the purpose of the present invention relates to a method for producing a low-expansion silicon-carbon composite doped with a heterogeneous element as described above, wherein the low-expansion silicon-carbon composite can be provided by performing a process including: a first step of preparing carbon-silicon composite particles; a second step of performing dry coating or wet coating of a coating agent including a heterogeneous element precursor and pitch on the surface of the carbon-silicon composite particles to produce carbon-silicon composite particles coated with the coating agent; and a third step of performing a carbonization treatment on the carbon-silicon composite particles coated with the coating agent to produce a composite in which a carbon coating layer doped with a heterogeneous element is formed on the outermost surface of the carbon-silicon composite particles.

[0039] As a preferred embodiment of the present invention, the amount of pitch coated on the carbon-silicon composite particles in the second step may be 4.0 to 30.0 parts by weight based on 100 parts by weight of the carbon-silicon composite particles.

[0040] As a preferred embodiment of the present invention, the two-step dry coating can be performed using a mechanofusion method.

[0041] As a preferred embodiment of the present invention, the mechanofusion method can perform coating for 5 to 30 minutes under conditions of a blade rotation speed of 500 to 5000 rpm of the mechanofusion equipment.

[0042] As a preferred embodiment of the present invention, the wet coating in the second step can be performed by mixing the coating solution containing the coating agent and THF with the carbon-silicon composite particles, and then removing the THF.

[0043] As a preferred embodiment of the present invention, THF removal can be performed by a method such as reduced pressure drying.

[0044] As a preferred embodiment of the present invention, the first step may include a step of depositing silicon (Si) including the surface of the carbon support.

[0045] As a preferred embodiment of the present invention, the deposition in steps 1 and 2 can be performed at a temperature of 300°C to 600°C and in an atmosphere supplying silane (SiH4) gas.

[0046] As a preferred embodiment of the present invention, silane gas can be supplied at 50 sccm to 500 sccm per 10 g of carbon support.

[0047]

[0048] Another object of the present invention is to provide a cathode material characterized by including the low-expansion silicon-carbon composite described above.

[0049] In addition, another object of the present invention is to provide a lithium ion battery and / or an all-solid-state battery including a negative electrode material.

[0050] The low-expansion silicon-carbon composite doped with a heterogeneous element of the present invention has low expansion properties by suppressing volume expansion due to insertion of lithium ions into the composite due to the presence of a carbon coating layer with an optimal thickness, and also has the effect of suppressing and preventing the formation of a side-reaction layer by minimizing side reactions with electrolyte components. In addition, the electrical conductivity is improved by doping the carbon coating layer with a heterogeneous element, so that the reduction in electrical conductivity due to the formation of the carbon coating layer can be prevented or improved. When the silicon-carbon composite with such characteristics is applied as an anode material of a secondary battery, a secondary battery (lithium ion battery and / or all-solid-state battery) using the same can secure increased charge-discharge efficiency and high long-term stability.

[0051] In this specification, expressions such as “has”, “may have”, “includes”, or “may include” indicate the presence of a feature (e.g., a component such as a number, function, operation, or part), and do not exclude the presence of additional features.

[0052] In this specification, expressions such as "A or B," "at least one of A and / or B," or "one or more of A or / and B" can include all possible combinations of the listed items. For example, "A or B," "at least one of A and B," or "at least one of A or B" can all refer to (1) including at least one A, (2) including at least one B, or (3) including both at least one A and at least one B.

[0053] 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.

[0054] Hereinafter, the present invention will be described in more detail.

[0055] The low-expansion silicon-carbon composite doped with a heterogeneous element of the present invention (hereinafter referred to as the "silicon-carbon composite") comprises carbon-silicon composite particles; and a carbon coating layer doped with a heterogeneous element (N, or N and B) is formed on the outermost surface of the carbon-silicon composite particles. In addition, the carbon coating layer is formed of a carbide of a coating agent including a heterogeneous element doping agent and pitch.

[0056] The coating agent may contain 0.5 to 30 wt% of the heterogeneous element doping agent and the remaining balance of 100 wt% of the pitch, and preferably may contain 1 to 20 wt% of the heterogeneous element doping agent and the remaining balance of 100 wt% of the pitch. At this time, if the content of the heterogeneous element doping agent is less than 1 wt%, the amount of the heterogeneous element doped into the carbon coating layer may be too small, so the effect of improving the electrical conductivity of the carbon coating layer may be insufficient, and if the content of the heterogeneous element doping agent exceeds 30 wt%, there may be a problem in which the electrical conductivity is reduced because the carbon is not sufficiently aligned.

[0057] And, among the coating agent components, the heterogeneous element doping agent includes a nitrogen precursor; or a nitrogen precursor and a boron precursor.

[0058] And, the nitrogen precursor may include at least one selected from melamine, NH3, dopamine, and hexamethylenetetramine, and preferably may include at least one selected from melamine and dopamine.

[0059] In addition, the boron precursor may include at least one selected from boric acid, boron oxide, and phenylboronic acid, and preferably may include at least one selected from boric acid and boron oxide.

[0060] In addition, when using a mixture of a nitrogen precursor and a boron precursor, it is appropriate to use the nitrogen precursor and the boron precursor in a weight ratio of 1:0.1 to 10, preferably 1:0.2 to 5, and if the boron precursor content is less than 0.1 weight ratio, the boron doping amount is small, so the effect of improving the electrical conductivity of the carbon coating layer may be minimal.

[0061] In addition, among the coating ingredients, the pitch may be a pitch derived from petroleum residue oil, manufactured using petroleum residue oil.

[0062] The carbon coating layer doped with the above heteroatom serves to minimize the volume expansion of the silicon-carbon composite due to lithium ion insertion when the silicon-carbon composite is used as the negative electrode material of a secondary battery, and to minimize the formation of a side reaction layer formed by the reaction between F in the electrolyte and the negative electrode material component. The carbon coating layer may have an average thickness of 10 to 190 nm, preferably an average thickness of 15 to 170 nm, and more preferably an average thickness of 20 to 150 nm. At this time, if the average thickness of the carbon coating layer is less than 10 nm, the thickness is insufficient, and the effect of suppressing the increase in the expansion rate of the silicon-carbon composite as the negative electrode material may be insufficient. On the other hand, if the average thickness of the carbon coating layer exceeds 190 nm, it is advantageous in terms of low expansion rate and suppression of the formation of side reaction layers, but the effect of increasing the electrical efficiency of the secondary battery may decrease. Therefore, it is appropriate to form the carbon coating layer with a thickness within the above range.

[0063] The carbon coating layer doped with the heterogeneous element of the silicon-carbon composite of the present invention can have a heterogeneous element content satisfying Equation 1 or Equation 2 below when analyzed by XPS. By satisfying Equation 1 or Equation 2 below, it can be more advantageous in achieving the purpose of the present invention.

[0064] [Formula 1]

[0065] 0.2% ≤ (A / C)×100(%) ≤ 2%

[0066] In Equation 1, A is the atomic% value of nitrogen (N) in the carbon support analyzed by XPS, and C is the atomic% value of carbon (C) in the carbon support analyzed by XPS.

[0067] [Formula 2]

[0068] 0.2% ≤ ((A+B) / C)×100(%) ≤ 2%

[0069] In Equation 2, A is the atomic% value of nitrogen (N) in the carbon support analyzed by XPS, B is the atomic% value of boron (B), and C is the atomic% value of carbon (C) in the carbon support analyzed by XPS.

[0070]

[0071] The silicon-carbon composite of the present invention described above can be manufactured by performing a process including: a first step of preparing carbon-silicon composite particles; a second step of performing dry or wet coating of a coating agent on the surface of the carbon-silicon composite particles to manufacture carbon-silicon composite particles coated with a coating agent; and a third step of performing a carbonization treatment on the carbon-silicon composite particles coated with the coating agent to manufacture a composite in which a carbon coating layer is formed on the outermost surface of the carbon-silicon composite particles.

[0072] The characteristics, physical properties and manufacturing method of the carbon-silicon composite particles of step 1 will be described later.

[0073] The coating agent of the second step includes a heterogeneous element doping agent and pitch as described above.

[0074] And, the coating amount of the coating agent coated on the carbon-silicon composite particles of the second step may be 4.0 to 30.0 parts by weight, preferably 5.0 to 28.0 parts by weight, and more preferably 10.0 to 25.0 parts by weight, based on 100 parts by weight of the carbon-silicon composite particles, and the amount of coated pitch is proportional to the thickness of the carbon coating layer. If the coating amount of the coating agent is less than 4 parts by weight based on 100 parts by weight of the carbon-silicon composite particles, the thickness of the carbon coating layer may not be sufficient, so that the effect of suppressing the increase in the expansion rate of the silicon-carbon composite as an anode material may be insufficient, and if the coating amount exceeds 30 parts by weight, it is advantageous in terms of low expansion rate and suppression of the formation of side reaction layers, but the effect of increasing the electrical efficiency of the secondary battery may decrease.

[0075] The above dry coating in step 2 can be performed using the mechanofusion method.

[0076] As a preferred embodiment of the above mechanofusion method, after the prepared carbon-silicon composite particles and coating agent are introduced into a mechanofusion device, coating can be performed for 5 to 30 minutes, preferably 8 to 25 minutes, under the condition of the blade rotation speed of the mechanofusion device being 500 to 5,000 rpm, preferably 900 to 4,500 rpm. By satisfying the conditions of the above mechanofusion method, it can be more advantageous to achieve the purpose of the present invention.

[0077] Additionally, the two-step wet coating can be performed by mixing the carbon-silicon composite particles with a coating solution containing the coating agent and THF (Tetrahydrofuran), and then removing the THF. At this time, the amount of pitch mixed in the coating solution is added and mixed so as to satisfy the coating amount described above, thereby preparing the coating solution. In addition, the THF removal can be performed by a method such as reduced pressure drying.

[0078] The silicon-carbon composite of the present invention manufactured with the composition and method described above can satisfy a volume expansion reduction rate of 100% or less, preferably a volume expansion reduction rate of 90% or less, and more preferably 10 to 70%, calculated based on the following equation 3.

[0079] [Formula 3]

[0080] Volume expansion reduction rate (%) = {(DE) / D} × 100(%)

[0081] In Equation 3, D is the volume of the carbon-silicon composite particles without a carbon coating layer, E is the volume of the low-expansion silicon-carbon composite doped with a heterogeneous element, and the volumes of D and E are the volumes of the negative electrode materials measured after the carbon-silicon composite particles without a carbon coating layer and the low-expansion silicon-carbon composite doped with a heterogeneous element were applied as negative electrode materials for a half-cell for a lithium-ion battery, respectively, and the half-cell was operated for 50 cycles. At this time, the negative electrode materials of the carbon-silicon composite particles without a carbon coating layer and the low-expansion silicon-carbon composite doped with a heterogeneous element have the same size before the half-cell operation.

[0082] In addition, in the silicon-carbon composite of the present invention, the change rate (%) of the fluorine atom content in the negative electrode material measured by the volume expansion reduction rate can satisfy the following equation 4.

[0083] [Formula 4]

[0084] 5% ≤ {(HG) / G}×100(%) ≤20%, preferably 6% ≤ {(HG) / G}×100(%) ≤19%

[0085] In Equation 4, G is the fluorine (F) content (in wt%) in the surface of the negative electrode material manufactured from carbon-silicon composite particles without a carbon coating layer for which the volume expansion reduction rate was measured, and H is the fluorine content (in wt%) in the surface of the negative electrode material manufactured from a low-expansion silicon-carbon composite doped with a heterogeneous element for which the volume expansion reduction rate was measured.

[0086]

[0087] Below, the carbon-silicon composite particles provided in the low-expansion silicon-carbon composite are described in detail.

[0088] [Carbon-silicon composite particles]

[0089] In the low-expansion silicon-carbon composite of the present invention, the carbon-silicon composite particles include a carbon support including a surface portion and a core portion; and silicon (Si) arranged including the surface of the carbon support.

[0090] In this specification, the core of the carbon support may mean an area within a distance of 1 / 2 of the radius of the support from the center of the support, and the surface may mean the remaining area of ​​the support excluding the core.

[0091] 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.

[0092] When the carbon support is a porous carbon support, the porous carbon support can be manufactured by a method including (1) a step of synthesizing pitch by thermal decomposition and condensation polymerization of a petroleum-based raw material, (2) 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, (3) a step of stabilizing the pellet-like pitch or the powder-like pitch, (4) a step of carbonizing the stabilized pitch to obtain a carbonized body, and (5) a step of activating the carbonized body to obtain a porous carbon support.

[0093] Step (1) of the method for manufacturing a porous carbon support according to the present invention may be a step of synthesizing pitch by thermal decomposition and polycondensation of petroleum-based raw materials.

[0094] 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.

[0095] 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.

[0096] 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 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.

[0097] In a specific embodiment of the present invention, the thermal decomposition and polycondensation of the petroleum-based raw material can be carried out at a temperature of 350 to 500°C. In a preferred specific embodiment of the present invention, the thermal decomposition and polycondensation of the petroleum-based raw material can be carried out at a temperature of 400 to 500°C. In a more preferred specific embodiment of the present invention, the thermal decomposition and polycondensation of the petroleum-based raw material can be carried out at a temperature of 430 to 470°C. When the temperature of the thermal decomposition and polycondensation of the petroleum-based raw material is 350 to 500°C, a pitch containing a large amount of relatively low molecular weight components can be produced, and in the activation process of step (5) described below, components having relatively small molecular weights are vaporized first, thereby sufficiently forming mesopores in the carbon support. If the thermal decomposition and polycondensation temperature of petroleum-based raw materials is less than 350°C, it is difficult to manufacture pitch that is solid at room temperature, and if this temperature exceeds 500°C, the pitch contains a large amount of relatively high molecular weight components, making it difficult to manufacture a carbon support having mesopores.

[0098] 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.

[0099] 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.

[0100] 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.

[0101] 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.

[0102] 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.

[0103] In a specific embodiment of the present invention, the pitch synthesized in step (1) may have a softening point of 200 to 350°C. In a preferred embodiment of the present invention, the pitch may have a softening point of 200 to 330°C. In a more preferred embodiment of the present invention, the pitch may have a softening point of 200 to 300°C. Since the pitch manufactured according to the present invention has a high softening point, when used as a precursor for manufacturing a carbon support, the stabilization process is easy, and a high yield can be obtained after carbonization and activation.

[0104] In a specific embodiment of the present invention, the yield of the pitch synthesized in step (1) may be 10 to 50 wt%. In another specific embodiment of the present invention, the yield of the pitch may be 10 to 40 wt%. In yet another specific embodiment of the present invention, the yield of the pitch may be 20 to 30 wt%.

[0105] In a process for producing a porous carbon support from a petroleum-based raw material according to one embodiment of the present invention, a step of pretreating the petroleum-based raw material may be performed prior to step (1) above. By removing low-boiling-point components contained in the petroleum-based raw material through the pretreatment step, a pitch having a higher softening point can be produced.

[0106] In a specific embodiment of the present invention, the pretreatment step may be performed at a temperature equal to or lower than the thermal decomposition and polycondensation temperature of the petroleum-based raw material in step (1), but is not particularly limited to this condition. Specifically, the pretreatment step may be performed at 250 to 450°C, preferably 250 to 400°C, and more preferably 300 to 400°C.

[0107] In a specific embodiment of the present invention, the pretreatment step may be performed for a time equal to or shorter than the time for thermal decomposition and polycondensation of the petroleum-based raw material in step (1), but is not particularly limited to this condition. Specifically, the pretreatment step may be performed for 1 to 8 hours, preferably 1 to 6 hours, and more preferably 1 to 5 hours.

[0108] In addition, in the above step (2), the pitch can be solidified and pelletized to obtain a pellet-like pitch, or the pitch can be solidified, pelletized, and pulverized to obtain a powder-like pitch.

[0109] First, in the case of the pellet-shaped pitch, the liquid pitch obtained in step (1) is solidified, for example, by extrusion and cooling, and then pelletized into a desired size to obtain a solid pitch pellet (pellet-shaped pitch). The process of extruding, cooling, and pelletizing the liquid pitch to obtain a solid pitch pellet can be performed using commercially available equipment. For example, this process can be performed using IPCO's Double Belt Cooler & Flaker, but is not particularly limited to this equipment.

[0110] The pitch pellets (pellet-shaped pitch) obtained in step (2) have an average particle size of 1 to 30 mm, preferably 5 to 25 mm. When the average particle size of the pitch pellets (pellet-shaped pitch) is within this range, a porous carbon support can be manufactured through stabilization, carbonization, and activation described below without separately pulverizing the pitch pellets (pellet-shaped pitch).

[0111] 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. Through crushing or pulverization, the pitch pellets (pellet-shaped pitch) can be further finely divided, and through classification, the particle size distribution of the pitch pellets (pellet-shaped pitch) can be made uniform. Here, classification can be performed by dry classification, wet classification, or classification using a sieve. Through crushing or pulverization and classification, a powdered pitch having a diameter of 50 to 500 μm can be obtained.

[0112] In addition, in the step (3), a step of stabilizing the pellet-shaped pitch or powder-shaped pitch may be performed. Specifically, the step (3) may be a step of stabilizing the structure of the pitch by first oxidizing the pellet-shaped pitch or powder-shaped pitch.

[0113] 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 350°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.

[0114] 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.

[0115] 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 or oxygen, 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.

[0116] 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.

[0117] And, in step (4), the stabilized pitch can be carbonized to obtain a carbonized body. Through carbonization of the stabilized pitch, other functional groups contained in the pitch are removed, and a carbonized body composed of substantially pure carbon can be obtained.

[0118] 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 of the pitch may be performed under a nitrogen or argon atmosphere, but is not particularly limited thereto.

[0119] In a specific embodiment of the present invention, the carbonization may be performed at a temperature of 700°C to 1,000°C, preferably 800°C to 1,000°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.

[0120] 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.

[0121] 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.

[0122] And, in step (5), a porous carbon support can be obtained by activating the carbonized body (carbonized pitch). By activating the carbonized body (carbonized pitch), pores are formed in the pitch, thereby obtaining a porous carbon support.

[0123] In a specific embodiment of the present invention, the activation of the carbonized body may be performed under an oxidizing gas atmosphere. In a preferred embodiment of the present invention, the activation of the carbonized body may be performed under a steam atmosphere, but is not particularly limited thereto.

[0124] In a specific example of the present invention, the activation of the carbonized body can be performed at a temperature of 700°C to 1,000°C, or 800°C to 1,000°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.

[0125] 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.

[0126] In a specific example 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.

[0127] 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.

[0128] In a specific embodiment of the present invention, the stabilization, carbonization, and activation of steps (3) to (5) above can each be performed in a heating furnace using microwaves. In a preferred specific embodiment of the present invention, the stabilization, carbonization, and activation of steps (3) to (5) above can all be performed in a heating furnace using microwaves. A heating furnace using microwaves is preferred because it can increase the temperature of the pitch itself without increasing the external temperature of the pitch, but is not particularly limited thereto.

[0129] In a specific embodiment of the present invention, the stabilization, carbonization, and activation of steps (3) to (5) above can be performed continuously in a single device. In a preferred embodiment of the present invention, the stabilization, carbonization, and activation of steps (3) to (5) above can be performed continuously in a single rotary kiln, but this device is not particularly limited. Since the stabilization, carbonization, and activation are performed continuously in a single device, process optimization can be easily achieved.

[0130] In a specific embodiment of the present invention, the porous carbon support (or porous carbon support powder) obtained in step (5) may be further pulverized or ground and classified. Through pulverization or grounding, the porous carbon support powder can be further finely divided, and through classification, the particle size distribution of the porous carbon support can be made uniform. Here, classification may be dry classification, wet classification, or classification using a sieve. Through pulverization or grounding and classification, a powdered porous carbon support having a diameter of 1 to 20 μm can be obtained.

[0131] The porous carbon support manufactured by performing the above steps (1) to (5) includes mesopores having a diameter of 2 nm to 50 nm, and the ratio of the volume of the mesopores of the surface layer to the volume of the entire mesopores may be 0.5 or more, preferably 0.5 to 0.76. When the ratio of the mesopores of the surface layer to the total mesopores of the porous carbon support is 0.5 or more, the mesopores formed in the surface layer may act as passages through which pores may be formed deep into the porous carbon support, so that silicon may be deposited into the interior of the support. In addition, the volume of the total mesopores of the porous carbon support may refer to the volume of the total mesopores arranged in the interior of the porous carbon support, and the volume of the mesopores of the surface layer may refer to the volume of the total mesopores arranged in the surface layer of the porous carbon support. In addition, the volume of the mesopores of the surface layer may mean the volume of the area corresponding to the surface layer with respect to the entire mesopores arranged in the porous carbon support.

[0132] At this time, if the ratio of the surface mesopores to the entire mesopores of the carbon-silicon composite particles is outside the above range, the charge / discharge capacity may decrease and the cycle characteristics may deteriorate.

[0133] In one example of the present invention, the porous carbon support of the carbon-silicon composite particles according to the present invention may have a ratio of mesopore volume to total pore volume of 0.1 or more. The pores of the porous carbon support can be classified into micropores with a diameter of less than 2 nm, mesopores with a diameter of 2 nm to 50 nm, and macropores with a diameter of more than 50 nm, depending on their size. Such porous supports have been studied in the direction of increasing the ratio of micropores to increase the specific surface area or increasing the ratio of macropores to increase the amount of material supported inside the pores. However, when there are many micropores, there is a problem that silicon (Si) is difficult to deposit inside the pores, resulting in a decrease in electrical capacity. In addition, when there are many macropores, silicon agglomeration occurs, which can generate stress during repeated charge and discharge processes, which can mechanically damage the negative electrode material.

[0134] On the other hand, in the case of mesopores, silicon can be sufficiently deposited deep within the pores during deposition. The carbon-silicon composite particles according to the present invention can deposit a sufficient amount of silicon within the pores of the porous support by including mesopores within a predetermined range.

[0135] In addition, the porous carbon support may have a higher porosity in the surface layer than in the deep layer, and thus may be more advantageous in achieving the purpose of the present invention.

[0136] The ratio of the volume of the mesopores to the volume of the entire pores of the porous carbon support may be, but is not limited to, 0.10 or more, 0.12 or more, 0.14 or more, or 0.15 or more. The upper limit of the ratio of the volume of the mesopores to the volume of the entire pores of the porous carbon support is not particularly limited, but may be, for example, 0.7 or less. When the ratio of the volume of the mesopores to the volume of the entire pores of the porous carbon support satisfies the above range, the porous carbon support has excellent electrical properties while preventing excessive aggregation of silicon, thereby preventing damage due to volume expansion of silicon.

[0137] In one embodiment of the present invention, the tap density of the porous carbon support may be 0.7 g / ml or less. The tap density of the porous carbon support may be a value measured using PT-TD200 (Pharma Test). Specifically, 40 ml of the porous carbon support is loaded into a cylinder, tapped 1,000 times, and the primary volume is observed. After the observation, the process of performing another 1,000 taps and observing the volume is repeated three times until there is no difference from the previous volume, and then the tap density can be calculated using the final volume. The tap density of the porous carbon support may be 0.70 g / ml or less, 0.65 g / ml or less, or 0.60 g / ml or less, and may be 0.05 g / ml or more, 0.10 g / ml or more, 0.15 g / ml or more, 0.20 g / ml or more, or 0.22 g / ml or more, but is not limited thereto. If the tap density of the porous carbon support is too low, process control may be difficult during silane gas deposition, resulting in a decrease in yield. In addition, if the tap density of the porous carbon support is too high, uniform coating may be difficult during silane gas deposition.

[0138] In one example of the present invention, the BET specific surface area of ​​the porous carbon support according to the present invention is 300 m 2 / g ~ 3,000 m 2 / g range. The BET specific surface area of ​​the porous carbon support may be a value measured using ASAP 2420 (Micromeritics instrument (USA)). Specifically, analysis was performed after vacuum drying at 300°C for 5 hours, and the BET equation and the BJH equation can be calculated using the N2 / 77K Isotherm adsorption results according to ISO9277. The BET specific surface area of ​​the porous carbon support may be 300 ㎡ / g or more, 400 ㎡ / g or more, or 500 ㎡ / g or more, and may be 3,000 ㎡ / g or less, 2,800 ㎡ / g or less, 2,600 ㎡ / g or less, or 2,000 ㎡ / g or less, and preferably 1,900 ㎡ / g or less. If the BET surface area of ​​the porous carbon support is excessively low, the proportion of macropores may increase, which may lower the mechanical strength of the negative electrode material and result in a lack of effective pores. In addition, if the BET surface area of ​​the porous carbon support is excessively high, the proportion of micropores may increase, and silicon may not be sufficiently deposited deep into the porous carbon support.

[0139] The diameter of the above porous carbon support may be 20 μm or less. The diameter is D 50It may refer to the diameter, and may be a value measured using MICROTRAC S3500 equipment. Specifically, it may refer to an average value obtained by dispersing a porous carbon support in ethanol and then performing particle size analysis three times. The diameter of the porous carbon support may be 20 ㎛ or less, 18 ㎛ or less, 16 ㎛ or less, 14 ㎛ or less, 12 ㎛ or less, or 10 ㎛ or less, and may be 1 ㎛ or more, 2 ㎛ or more, 3 ㎛ or more, 4 ㎛ or more, or 4.5 ㎛ or more, but is not limited thereto. If the diameter of the porous carbon support is too small, when performing coating, silicon may be quickly filled inside and then additional coating may be performed on the surface, so that the surface coating layer may be formed thickly. In this case, deterioration may be accelerated during charge and discharge, and agglomeration of materials with small particle sizes may occur when manufacturing an electrode, and deterioration of the agglomerated portion may be significant. In addition, if the diameter of the porous carbon support is too large, it may be difficult for silane gas to diffuse into the interior of the porous carbon support, making it difficult to form a uniform silicon coating layer inside the support. In addition, if the diameter of the porous carbon support is too large, it may be difficult to uniformly coat the slurry on the current collector during electrode manufacturing, which may result in a decrease in capacity uniformity.

[0140] In one example, the porous carbon support of the carbon-silicon composite particles according to the present invention may include macropores having a diameter exceeding 50 nm. At this time, the ratio of the volume of the macropores to the total pore volume of the porous carbon support may be 0.4 or less. The ratio of the volume of the macropores to the total pore volume of the porous carbon support may be 0.40 or less, 0.35 or less, 0.30 or less, 0.25 or less, 0.20 or less, or 0.15 or less, but is not limited thereto. The lower limit of the ratio of the volume of the macropores to the total pore volume of the porous carbon support is not particularly limited, but may be, for example, 0 or more or greater than 0. When the ratio of the macropores of the porous carbon support of the carbon-silicon composite particles is too high, the mechanical strength of the negative electrode material manufactured from the carbon-silicon composite particles may be reduced. In addition, local agglomeration of silicon occurs inside the negative electrode material, which can cause damage to the negative electrode material by generating stress due to volume expansion during repeated charge and discharge processes.

[0141]

[0142] In addition, when the carbon support is hard carbon, the hard carbon can be manufactured by a method including the steps of (1') synthesizing pitch by thermal decomposition and condensation polymerization of petroleum-based raw materials, (2') solidifying and pelletizing the pitch to obtain pellet-like pitch, or solidifying, pelletizing, and pulverizing the pitch to obtain powder-like pitch, (3') stabilizing the pellet-like pitch or powder-like pitch, and (4') carbonizing the stabilized pitch to obtain hard carbon.

[0143] At this time, since the description of the above steps (1') to (4') may be the same as the description of the above steps (1) to (4), a detailed description will be omitted.

[0144] 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.

[0145]

[0146] In addition, when the carbon support is soft carbon, the soft carbon can be manufactured by a method including the steps of (1") synthesizing pitch by thermal decomposition and condensation polymerization of petroleum-based raw materials, (2") solidifying and pelletizing the pitch to obtain pellet-like pitch, or solidifying, pelletizing, and pulverizing the pitch to obtain powder-like pitch, (3") stabilizing the pellet-like pitch or powder-like pitch, and (4") carbonizing the stabilized pitch to obtain soft carbon.

[0147] At this time, the description of the above steps (1") and (2") may be the same as the description of the above steps (1) and (2), so a detailed description will be omitted.

[0148] The above step (3") and the step (4") described below may be performed as a series of steps in a rotary kiln, as in the above-described steps (3) and (4), or may be performed as a series of steps by placing the material in a crucible and placing it in an oven. Preferably, it may be advantageous to achieve the purpose of the present invention to perform the series of steps by placing the material in a crucible and placing it in an oven.

[0149] Meanwhile, since the description of the contents other than the above step (3") may be the same as the description of the above step (3), a detailed description will be omitted.

[0150] In addition, the above step (4") is a step of carbonizing the stabilized pitch to obtain soft carbon, and through carbonization of the stabilized pitch, other functional groups included in the pitch are removed, and soft carbon composed of substantially pure carbon can be obtained.

[0151] In a specific embodiment of the present invention, the carbonization in step (4") may be performed under an inert gas atmosphere. In a preferred specific embodiment of the present invention, the carbonization in step (4") may be performed under a nitrogen or argon atmosphere, but is not particularly limited thereto.

[0152] In a specific example of the present invention, the carbonization in step (4") may be performed at a temperature of 1,000°C to 2,700°C, preferably 1,200°C to 2,200°C. If the temperature during the carbonization in step (4") is lower than this range, carbonization may not be sufficiently performed, and if the temperature during the carbonization is higher than this range, the carbonization yield may decrease.

[0153] In a specific example of the present invention, the carbonization in step (4") can 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.

[0154] In a specific example of the present invention, the carbonization in step (4") can be performed for 0.5 to 5 hours, preferably 1 to 3 hours. When the carbonization in step (4") is performed for this period of time, the stabilized pitch can be sufficiently carbonized.

[0155] Meanwhile, since the description of the contents other than the above step (4") may be the same as the description of the above step (4), a detailed description will be omitted.

[0156] 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.

[0157]

[0158] The silicon (Si) of the carbon-silicon composite particles according to the present invention can be arranged including on the surface of the carbon support.

[0159] At this time, if the carbon support is a porous carbon support, the silicon may be arranged on the surface and / or inside the pores of the deep portion of the porous carbon support. The silicon may be formed by deposition as described below.

[0160] Since the carbon-silicon composite particles according to the present invention have the above structure, 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.

[0161] In another example, the silicon content of the carbon-silicon composite particles according to the present invention may be 10 wt% or more based on the total weight of the carbon-silicon composite particles. The silicon content of the carbon-silicon composite particles may be a value obtained by analysis using an energy dispersive spectrometer (EDS). The silicon content in the carbon-silicon composite particles may be 10 wt% or more, 15 wt% or more, 20 wt% or more, 25 wt% or more, or 30 wt% or more, but is not limited thereto. In addition, the silicon content of the carbon-silicon composite particles may be 60 wt% or less, 58 wt% or less, 56 wt% or less, 54 wt% or less, 52 wt% or less, or 50 wt% or less, but is not limited thereto. If the silicon content of the carbon-silicon composite particles is too low, the electric capacity may decrease, and if the silicon content is too high, the volume expansion rate of the silicon may increase during charge and discharge, which may cause structural damage to the negative electrode material and deteriorate the cycle characteristics.

[0162]

[0163] Meanwhile, the carbon-silicon composite particles described above are manufactured in the first step of preparing carbon-silicon composite particles including a carbon support including a surface portion and a core portion, and silicon arranged including the surface of the carbon support.

[0164] At this time, the first step may include a step of depositing silicon (Si) including the surface of the carbon support. The deposition may be performed at a temperature of 300°C to 600°C while supplying silane (SiH4) gas.

[0165] The above silane gas supply can be performed by supplying 50 sccm to 500 sccm per 10 g of the carbon support.

[0166] In a preferred embodiment, the carbon support may be deposited at a temperature of 300°C to 600°C and under conditions of 150 sccm to 500 sccm and a silane (SiH4) gas atmosphere. The deposition may be performed, for example, using chemical vapor deposition (CVD) and under atmospheric pressure, but is not limited thereto. Through the deposition, silicon may be deposited, including on the surface of the carbon support.

[0167]

[0168] [Silicon deposition]

[0169] The carbon support manufactured by the method described above can be provided as a silicon anode material, preferably as an anode material for a secondary battery, by silane coating or deposition treatment. If the carbon support is a porous carbon support, a sufficient amount of silicon (Si) can be deposited within the pores of the porous carbon support by including mesopores within a predetermined range.

[0170] The content of the deposited silicon may be 10 wt% or more based on the weight of the total particles. The content of the deposited silicon may be a value obtained by analysis using an energy dispersive spectrometer (EDS). The content of the deposited silicon may be 10 wt% or more, 15 wt% or more, 20 wt% or more, 25 wt% or more, or 30 wt% or more, but is not limited thereto. In addition, the content of the deposited silicon may be 60 wt% or less, 58 wt% or less, 56 wt% or less, 54 wt% or less, 52 wt% or less, or 50 wt% or less, but is not limited thereto. If the content of the deposited silicon is too low, the electric capacity may be reduced. In addition, if the content of the deposited silicon is too large, the problem caused by the volume expansion of the silicon during charge and discharge may not be solved, which may cause structural damage to the negative electrode material and deteriorate the cycle characteristics.

[0171]

[0172] Furthermore, the present invention provides an anode material comprising the above-described silicon-carbon composite. Since the anode material comprises the above-described low-expansion silicon-carbon composite, it can have improved mechanical strength along with high electrical capacity and excellent cycle characteristics.

[0173] The method for manufacturing the above-mentioned negative electrode material is not particularly limited, and can be manufactured using a general method for manufacturing negative electrode materials. For example, the above-mentioned negative electrode material can be manufactured by mixing a low-expansion silicon-carbon composite, an active material, a conductive material, a binder, etc., and coating / drying / rolling it onto a component such as an electrode current collector, but is not limited thereto.

[0174] Furthermore, the present invention provides a lithium ion battery comprising the above-described negative electrode material. Furthermore, the present invention provides an all-solid-state battery comprising the above-described negative electrode material.

[0175] The lithium ion battery may specifically include a positive electrode, a negative electrode, a separator, and an electrolyte. At this time, the negative electrode may include the above-described battery negative electrode material. The positive electrode may use a material usable in a lithium ion battery, and may include, for example, one or more positive electrode active materials selected from doped or undoped lithium nickel oxide, lithium cobalt oxide, lithium cobalt aluminum oxide, lithium nickel cobalt manganese oxide, lithium manganese oxide, and lithium nickel cobalt aluminum oxide, and a positive electrode current collector selected from aluminum, stainless steel, nickel, titanium, platinum, or an alloy thereof, but is not limited thereto. In addition, the separator may use a typical separator usable in a lithium ion battery. The separator may include, for example, one or more selected from glass fiber, polyester, Teflon, polyethylene, polypropylene, and polytetrafluoroethylene (PTFE), but is not limited thereto.

[0176] The negative electrode of the lithium ion battery may include the above-described negative electrode material. The negative electrode may include a negative electrode current collector and a negative electrode material, and the negative electrode current collector may include one or more selected from aluminum, stainless steel, nickel, titanium, platinum, or an alloy thereof, but is not limited thereto.

[0177] The electrolyte of the above lithium ion battery may include, but is not limited to, an organic liquid electrolyte, an inorganic liquid electrolyte, a polymer electrolyte, or a molten inorganic electrolyte usable in a lithium ion battery.

[0178] The above-mentioned all-solid-state battery may specifically include a positive electrode, a negative electrode, and a solid electrolyte, and may further include a separator as needed, but is not limited thereto. The positive electrode may include the above-mentioned positive electrode active material, and may include a positive electrode current collector as needed, but is not limited thereto.

[0179] The above negative electrode may include a negative electrode material according to the present invention. The negative electrode may have a single-layer structure including the battery negative electrode material, or may further include a negative electrode current collector as needed, but is not limited thereto.

[0180] The solid electrolyte may optionally use a solid electrolyte usable in an all-solid-state battery. The solid electrolyte may be, for example, at least one selected from the group consisting of a Garnet-type, a Nasicon-type, a LISICON-type, a perovskite-type, and a LiPON-type, but is not limited thereto.

[0181] Hereinafter, the present invention will be described in more detail through examples, but the following examples do not limit the scope of the present invention, and should be interpreted as helping to understand the present invention.

[0182] [Example]

[0183] Preparation Example 1: Preparation of a porous carbon support

[0184] 300 g of petroleum residue oil (YNCC, HTC PFO (pyrolysis fuel oil)) was placed in a reactor equipped with a stirrer, and pyrolysis and polycondensation were performed at 450°C for 3 hours while supplying 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 of 1–30 mm.

[0185] After crushing the solid pitch pellets obtained above, they were placed in a rotary kiln with three zones, where they were sequentially subjected to stabilization, carbonization, and activation. The conditions for stabilization, carbonization, and activation are shown in Table 1 below.

[0186] The activated carbonized body, after the above activation, was pulverized using a pulverizer (NETZSCH, air jet mill) to produce a porous carbon support.

[0187]

[0188] Preparation examples 2-3

[0189] A porous carbon support was manufactured in the same manner as Preparation Example 1, except that the carbonization and activation conditions were changed as shown in Table 1 below.

[0190] Step Condition Preparation Example 1 Preparation Example 2 Preparation Example 3 Stabilization temperature (℃) 310 310 310 Hours (hr) 222 Atmosphere Air Air Air Carbonization temperature (℃) 900 900 1000 Hours (hr) 111 Atmosphere Nitrogen Nitrogen Nitrogen Activation temperature (℃) 900 900 1000 Hours (hr) 323 Water vapor flow rate (ml / min) 10 10 10

[0191]

[0192] Table 2 below shows the measured physical properties of the manufactured porous carbon supports. The specific surface area of ​​the porous carbon supports was measured using a Belsorp mini II according to ASTM D4820-93. The tap density of the carbon supports was measured using a tap density analyzer (Electrolab, ETD-1020x) according to ASTM B527. 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.

[0193] Preparation Example 1 Preparation Example 2 Preparation Example 3 Particle size distribution D50 (㎛) 9.2 16.3 47.20 Specific surface area (m 2 / g)1240.91417.7988.6Tap density (g / ml)0.590.360.43Micropore (%)72.860.823.9Mesopore (%)25.131.162.1Macropore (%)2.48.12.5Mesopore ratio of surface layer0.660.630.51

[0194]

[0195] Example 1: Preparation of carbon-silicon composite particles and low-expansion silicon-carbon composites doped with heterogeneous elements

[0196] (1) Manufacturing of carbon-silicon (C-Si) composite particles

[0197] Carbon-silicon composite particles were prepared using the porous carbon support manufactured in Preparation Example 1. 15 to 20 g of the porous carbon support of Preparation Example 1 was placed in a rotary kiln, and silane (SiH4) gas was injected to deposit the porous carbon support.

[0198] During silane gas coating, the pressure was atmospheric pressure, and the deposition was performed for 1 hour at a temperature of 475°C and a flow rate of 300 sccm to produce carbon-silicon composite particles. The physical properties of the produced carbon-silicon composite particles are shown in Table 3 below.

[0199] (2) Manufacturing of low-expansion silicon-carbon (Si-C) composites doped with heterogeneous elements

[0200] A coating agent was prepared by mixing 3 wt% of melamine, a nitrogen precursor, and 97 wt% of pitch derived from petroleum residue.

[0201] For 100 parts by weight of the carbon-silicon composite particles manufactured previously, 22 parts by weight of the coating agent was introduced into the reactor of a mechanofusion device, and then coating was performed for 15 minutes under conditions of a blade rotation speed of 2,700 rpm to manufacture carbon-silicon composite particles coated with the coating agent.

[0202] Next, the carbon-silicon composite particles coated with the coating agent were placed in an electric furnace, heated at 5°C / min to 700°C, carbonization was performed at 700°C for 2 hours, and then slowly cooled to 25°C to form a carbon coating layer doped with nitrogen (N), a heterogeneous element, with a thickness of 150 nm on the surface of the carbon-silicon composite particles, thereby manufacturing a low-expansion silicon-carbon composite.

[0203]

[0204] Example 2: Low-expansion Si-C composite having N, B doped carbon coating layer

[0205] A low-expansion silicon-carbon composite was manufactured in the same manner as in Example 1, but a coating agent was prepared by mixing 2.5 wt% of melamine as a nitrogen precursor, 2.5 wt% of boric acid as a boron precursor, and 95 wt% of pitch derived from petroleum residue, to manufacture carbon-silicon composite particles coated with the coating agent, which were then carbonized to manufacture a low-expansion silicon-carbon composite having a carbon coating layer doped with heterogeneous elements nitrogen (N) and boron (B).

[0206]

[0207] Example 3: Preparation of carbon-silicon composite particles and low-expansion silicon-carbon composites doped with heterogeneous elements.

[0208] The above Example 3 is a commercial product (Ingevity) with a diameter of 4.28 ㎛ as a porous carbon support. ® C-Si composite particles were manufactured in the same manner as in Example 1, except that a commercially available (product name: BAX1500) was used.

[0209] And, each of the above C-Si composite particles was manufactured into a low-expansion Si-C composite having a carbon coating layer of the same thickness formed using a mechanofusion device in the same manner as in Example 1.

[0210] The values ​​in parentheses of Example 3 in Table 3 below are the physical properties of the porous carbon support (BAX1500) before Si deposition.

[0211]

[0212] Example 4

[0213] Example 4 produced C-Si composite particles in the same manner as Example 1, except that graphite having a diameter of 17.08 μm was used as a porous carbon support, and the deposition was performed for 47 minutes at a flow rate of 100 sccm during silane gas deposition.

[0214] And, each of the C-Si composite particles of Example 4 was manufactured into a low-expansion Si-C composite having a carbon coating layer of the same thickness formed using a mechanofusion device in the same manner as Example 1.

[0215] The values ​​in parentheses of Example 4 in Table 3 below are the physical properties of the carbon support (graphite) before Si deposition.

[0216] At this time, the thickness of the carbon coating layer was measured through TEM analysis after cutting the cross-section.

[0217]

[0218] Comparative Example 1: Low-expansion Si-C composite having an undoped carbon coating layer

[0219] A silicon-carbon composite was manufactured using the same method as in Example 1, but using only pitch derived from petroleum residue as a coating agent, a low-expansion silicon-carbon composite was manufactured under the same conditions.

[0220] Example 1 Example 2 Example 3 Example 4 Comparative Example 1 C-Si composite particles (after Si deposition) Average particle size (㎛) 6.2 6.10 4.28 17.08 6.14 Specific surface area (m 2 / g)81.882.794.25.498.7Tab density (g / ml)0.610.6130.210.960.62Si content (weight%)43.845.227.35.745.0Low expansion Si-C composite coating agentCoating amount9 parts by weight (based on 100 parts by weight of C-Si composite particles)Carbon coating layer thickness150 nm120 nm105 nm80 nm100 nm

[0221]

[0222] Examples 5 to 7 and Comparative Example 2

[0223] After manufacturing carbon-silicon (C-Si) composite particles in the same manner as in Example 1, a coating agent was coated and carbonized using the mechanofusion method under the same conditions to manufacture a silicon-carbon (Si-C) composite, but the coating amount was changed to form a low-expansion C-Si composite having a carbon coating layer having a thickness as shown in Table 4 below, and Examples 5 to 7 and Comparative Example 2 were performed, respectively.

[0224] Low-expansion Si-C composite Example 1 Example 5 Example 6 Example 7 Comparative Example 2 Coating amount (weight parts) based on 100 parts by weight of C-Si composite particles 227 14300 Carbon coating layer thickness 150 nm 100 nm 120 nm 200 nm 0 Average particle size (㎛) 6.2 6.0 5 5.9 7 10 5.90 Tap density (g / ml) 0.6 1 0.6 3 0 0.7 1 9 0.6 9 4 0.62

[0225]

[0226] Experimental Example 1: XPS Analysis

[0227] XPS analysis was performed on the carbon coating layer of the composites manufactured in Examples 1, 2, 5, and 7, and the results are shown in Table 5 below.

[0228] [Formula 1]

[0229] 0.2% ≤ (A / C)×100(%) ≤ 2%

[0230] In Equation 1, A is the atomic% value of nitrogen (N) in the carbon support analyzed by XPS, and C is the atomic% value of carbon (C) in the carbon support analyzed by XPS.

[0231] [Formula 2]

[0232] 0.2% ≤ ((A+B) / C)×100(%) ≤ 2%

[0233] In Equation 2, A is the atomic% value of nitrogen (N) in the carbon support analyzed by XPS, B is the atomic% value of boron (B), and C is the atomic% value of carbon (C) in the carbon support analyzed by XPS.

[0234] Element content (atomic%) in the carbon coating layer of the composite material Formula 1 or Formula 2 Nitrogen (N) Boron (B) Carbon (C) Example 1 0.460 47.81 Nitrogen / Carbon = 0.96% Example 2 0.37 0.33 45.75 (Nitrogen + Boron) / Carbon = 1.53% Example 5 0.070 52.4 Nitrogen / Carbon = 2.30% Example 7 0.90 39.13 Nitrogen / Carbon = 0.96%

[0235]

[0236] Experimental Example 2: Electrochemical Evaluation of Secondary Batteries

[0237] Half coin cells were manufactured using each of the Si-C composites manufactured in Examples 1 to 7 and Comparative Examples 1 to 2 (Manufacturing Examples 1 to 7 and Comparative Manufacturing Examples 1 to 2).

[0238] Low-expansion C-Si composite: A slurry was prepared by mixing a conductive material and a binder in a ratio of 8:1:1. At this time, the conductive material used was super-P, and the binder used was a mixture of styrene butadiene rubber (SBR) and sodium carboxymethyl cellulose (CMC) in a weight ratio of 5:5.

[0239] Next, the slurry was uniformly applied to copper foil and dried in an 80°C oven for approximately 1 hour. After the primary drying, the slurry was roll-pressed and dried in a 120°C vacuum oven for approximately 6 hours and 30 minutes to manufacture a negative electrode plate.

[0240] A half coin cell was manufactured using the above-mentioned negative electrode and lithium foil as a counter electrode. A porous polyethylene film was used as a separator, and a CR2032 half coin cell (half cell) was manufactured under the conditions shown in Table 6 below.

[0241] The electrolyte was prepared by dissolving 1.3 M LiPF6 in a solvent containing ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) in a volume ratio of 3:5:2, and dissolving 10 wt% fluoro-ethylene carbonate (FEC), 0.2 wt% lithium tetrafluoroborate (LiBF4), 0.5 wt% vinylene carbonate (VC), and 1 wt% propane sulton (PS) additives (see Table 6).

[0242] Composition (AM:CM:BM) 8:1:1 Area capacity (mAh / cm 2 )1 Electrolyte 1.3M LiPF6 EC / EMC / DMC 3:5:2, FEC 10%, LiBF4 0.2%, 0.5% VC, 1% PS Cut-off voltage (V) Formation: 0.005 ~ 1.5, Cycle test: 0.005 ~ 1.5 C-rate (C) Formation: 0.1 ~ 0.1. 0.01 C cut-off (CV) at 0.005 V

[0243]

[0244] In Table 6 above, AM, CM, and BM represent active material (silicon-carbon composite), conductor (Super P carbon black), and binder (styrene-butadiene rubber / carboxymethyl cellulose 5:5), respectively, and EC, EMC, DMC, FEC, VC, and PS represent ethylene carbonate, ethyl methyl carbonate, dimethyl carbonate, fluoroethylene carbonate, vinylene carbonate, and propane sultone, respectively.

[0245] Electrochemical analysis was performed on the manufactured half coin cell under the following conditions.

[0246] Cut off voltage (V): 0.005 - 1.5V (Formation), 0.005 - 1.2V(Cycle)

[0247] Formation C-rate (C): 0.1C lithiation, 0.1C delithiation

[0248] Cycle C-rate (C): 0.5C lithiation, 0.5C delithiation

[0249] In addition, the volume expansion rate of the low-expansion silicon-carbon composite after operating the half-cell for 40 cycles was measured based on Equation 3 below, and the change rate (%) of the fluorine atom content in the negative electrode material, which measured the volume expansion reduction rate, was measured using Equation 4 and is shown in Table 7 below.

[0250] [Formula 3]

[0251] Volume expansion reduction rate (%) = {(DE) / D} × 100(%)

[0252] In Equation 3, D is the volume of the carbon-silicon composite particles without a carbon coating layer, and E is the volume of the low-expansion silicon-carbon composite doped with a heterogeneous element. The volumes of D and E are the volumes of the negative electrode materials measured after the carbon-silicon composite particles without a carbon coating layer and the low-expansion silicon-carbon composite doped with a heterogeneous element were applied as negative electrode materials for a half-cell for a lithium-ion battery, respectively, and the half-cell was operated for 40 cycles. At this time, the negative electrode materials of the carbon-silicon composite particles without a carbon coating layer and the low-expansion silicon-carbon composite doped with a heterogeneous element have the same size before the half-cell operation.

[0253] [Formula 4]

[0254] Fluorine atom (F) content (%) in the cathode material = {(HG) / G}×100(%)

[0255] In Equation 4, G is the fluorine (F) content (weight %) in the surface of the negative electrode material manufactured from carbon-silicon composite particles without a carbon coating layer for which the volume expansion reduction rate was measured, and H is the fluorine content (weight %) in the surface of the negative electrode material manufactured from the silicon-carbon composite for which the volume expansion reduction rate was measured.

[0256] After initial 50 cycles of operation, half-cell low-expansion C-Si composite recharge capacity (mAh / g) discharge capacity (mAh / g) ICE (%) volume expansion reduction rate (%) change rate of F content in negative electrode material (%) initial capacity retention rate (%) manufacturing example 1 Example 1 18921570833211.933.5 manufacturing example 2 Example 2 1879156183.13112.336.6 manufacturing example 3 Example 3 1637135282.6337.629.6 manufacturing example 4 Example 4 1398126990.8214.823.6 manufacturing example 5 Example 5 1898154381.32710.331.8 manufacturing example 6 Example 61890155282.12911.132.7 Manufacturing Example 7 Example 71658132079.6369.636.8 Comparative Manufacturing Example 1 Comparative Example 11883151380.33210.136.7 Comparative Manufacturing Example 2 Comparative Example 21810149682.60021.7

[0257]

[0258] Experimental Example 3: Electrochemical Evaluation of All-Solid-State Batteries

[0259] Manufacturing Example 8 was performed by manufacturing an all-solid-state battery using the carbon-silicon composite manufactured in Example 1.

[0260] The solid electrolyte used was sulfide-based argyrodite with a diameter of 5 μm, and was manufactured into pellets by applying a pressure of 130 MPa.

[0261] The low-expansion silicon-carbon composite manufactured in Manufacturing Example 8: solid electrolyte: conductive material were mixed in a ratio of 50:40:10, applied onto the manufactured pellets, and a pressure of 440 MPa was applied to manufacture a laminate. The solid electrolyte used was an argyrodite sulfide-based solid electrolyte having a diameter of 1 μm, and the conductive material used was VGCF.

[0262] An all-solid-state battery compression cell was manufactured by using the above-manufactured laminate and a 1t (1mm) thick lithium metal as a counter electrode and applying a force of 50kgf using a torque wrench.

[0263] Electrochemical analysis was performed on the manufactured all-solid-state battery compression cell under the following conditions.

[0264] Cut off voltage (V): 0.005 - 1.5V (Formation), 0.005 - 1.0V(Cycle)

[0265] Formation C-rate (C): 0.1C lithiation, 0.1C delithiation

[0266] Cycle C-rate (C): 0.3C lithiation, 0.3C delithiation

[0267] After 50 cycles of operation, C-rate, charge capacity (mAh / g), discharge capacity (mAh / g), ICE (%), initial capacity retention rate (%), manufacturing example 80.1C1515123581.574.2

[0268]

[0269] While the embodiments of the present invention have been described in detail above, the present invention is not limited to the above-described embodiments and the attached drawings, but is intended to be defined by the appended claims. Accordingly, those skilled in the art will appreciate that various substitutions, modifications, and alterations may be made without departing from the technical spirit of the present invention as set forth in the claims, and such modifications are also within the scope of the present invention.

Claims

1. Carbon-silicon composite particles; and a carbon coating layer doped with a heterogeneous element is formed on the outermost surface of the carbon-silicon composite particles; The carbon-silicon composite particles include a carbon support including a surface portion and a core portion; and silicon (Si) arranged including the surface of the carbon support; A low-expansion silicon-carbon composite with improved electrical conductivity, characterized in that the above heterogeneous element comprises nitrogen (N) or nitrogen and boron (B).

2. In the first paragraph, the carbon coating layer includes a carbide of a coating agent including a heterogeneous element doping agent and pitch, A low-expansion silicon-carbon composite with improved electrical conductivity, characterized in that the heteroatom doping agent comprises a nitrogen precursor; or a nitrogen precursor and a boron precursor.

3. A low-expansion silicon-carbon composite with improved electrical conductivity, characterized in that the carbon coating layer in the first paragraph has an average thickness of 10 to 190 nm.

4. In the second paragraph, the pitch is a low-expansion silicon-carbon composite with improved electrical conductivity, characterized in that it is manufactured based on petroleum residue.

5. In the second paragraph, the nitrogen precursor includes at least one selected from melamine, NH3, dopamine, and hexamethylenetetramine, A low-expansion silicon-carbon composite with improved electrical conductivity, characterized in that the boron precursor comprises at least one selected from boric acid, boron oxide, and phenylboronic acid.

6. In the first paragraph, the carbon coating layer doped with the heterogeneous element is characterized in that the content of the heterogeneous element satisfies the following equation 1 or equation 2 when analyzed by XPS, and is a low-expansion silicon-carbon composite with improved electrical conductivity; [Formula 1] 0.2% ≤ (A / C)×100(%) ≤ 2% In Equation 1, A is the atomic% value of nitrogen (N) in the carbon support analyzed by XPS, and C is the atomic% value of carbon (C) in the carbon support analyzed by XPS. [Formula 2] 0.2% ≤ ((A+B) / C)×100(%) ≤ 2% In Equation 2, A is the atomic% value of nitrogen (N) in the carbon support analyzed by XPS, B is the atomic% value of boron (B), and C is the atomic% value of carbon (C) in the carbon support analyzed by XPS.

7. In paragraph 1, A low-expansion silicon-carbon composite with improved electrical conductivity, characterized in that the carbon support comprises a non-porous carbon support including at least one of hard carbon and soft carbon.

8. In paragraph 1, The above carbon support comprises a porous carbon support, A low-expansion silicon-carbon composite with improved electrical conductivity, characterized in that the silicon is arranged on the surface and inside the pores of the porous carbon support.

9. In the 8th paragraph, the porous carbon support includes mesopores having a diameter of 2 nm to 50 nm, A low-expansion silicon-carbon composite with improved electrical conductivity, characterized in that the ratio of the volume of mesopores in the surface layer to the volume of the entire mesopores of the porous carbon support is 0.5 to 0.

76.

10. In the 8th paragraph, the porous carbon support has a ratio of the volume of mesopores to the volume of the total pores of 0.1 or more, A low-expansion silicon-carbon composite with improved electrical conductivity characterized by a surface porosity greater than the deep porosity.

11. Step 1: Preparing carbon-silicon composite particles; Step 2: producing carbon-silicon composite particles coated with a coating agent by dry-coating or wet-coating a coating agent containing a heterogeneous element precursor and pitch on the surface of the carbon-silicon composite particles; and A method for manufacturing a low-expansion silicon-carbon composite with improved electrical conductivity, characterized by performing a process including: performing a third step of carbonizing carbon-silicon composite particles coated with the above coating agent to manufacture a composite in which a carbon coating layer doped with a heterogeneous element is formed on the outermost surface of the carbon-silicon composite particles.

12. In paragraph 11, A method for manufacturing a low-expansion silicon-carbon composite with improved electrical conductivity, characterized in that the coating amount of the coating agent coated on the carbon-silicon composite particles in the above 2 steps is 4.0 to 30.0 parts by weight per 100 parts by weight of the carbon-silicon composite particles.

13. In paragraph 11, the two-step dry coating is performed using the mechanofusion method, The above mechanofusion method is a method for manufacturing a low-expansion silicon-carbon composite with improved electrical conductivity, characterized in that coating is performed for 5 to 30 minutes under conditions of a blade rotation speed of 500 to 5000 rpm of a mechanofusion device.

14. In paragraph 11, the first step, A method for producing a low-expansion silicon-carbon composite with improved electrical conductivity, characterized by comprising a step of depositing silicon (Si) including the surface of the carbon support.

15. A cathode material characterized by comprising a silicon-carbon composite according to any one of claims 1 to 8.

16. A lithium ion battery comprising the negative electrode material of Article 15.

17. An all-solid-state battery comprising the negative electrode material of Article 15.