Low-expansion silicon-carbon composite, manufacturing method therefor, negative electrode material comprising same, and lithium-ion battery and all-solid-state battery comprising same

Abstract

The present invention relates to a low-expansion silicon-carbon composite, which comprises: a carbon-silicon composite particle comprising a carbon support including a surface layer portion and a core portion and silicon disposed on the surface of the carbon support; and a carbon coating layer disposed on the outermost surface of the carbon-silicon composite particle.

Description

Low-expansion silicon-carbon composite, method for producing same, negative electrode material comprising same, lithium-ion battery and all-solid-state battery comprising same

[0001] The present invention relates to a low-expansion silicon-carbon composite capable of minimizing such volume expansion and side reactions with electrolyte components, a method for manufacturing the same, an anode material comprising the same, a lithium-ion battery, and an all-solid-state battery, which have a problem in that volume expansion occurs due to lithium ions being inserted into the anode material by repeated operation of the battery, and the lifespan of the battery is shortened due to side reactions with electrolyte components.

[0002]

[0003] 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.

[0004] 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.

[0005] 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.

[0006] Additionally, the introduction of carbon materials as a support for the above silicon-based negative electrode material is being attempted and developed.

[0007] 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).

[0008] 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 reduces the energy required for heat treatment (U.S. Patent Nos. 4,242,196 and 4,340,464).

[0009] 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.

[0010] 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.

[0011] 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 component. 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, 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.

[0012]

[0013] The present invention, which aims to solve the above problem, provides a low-expansion silicon-carbon composite comprising a carbon support including a surface portion and a deep portion, carbon-silicon composite particles including silicon arranged including the surface of the carbon support, and a carbon coating layer arranged on the outermost surface of the carbon-silicon composite particles.

[0014] According to one embodiment of the present invention, the carbon coating layer may include carbide of pitch, the carbon coating layer may have an average thickness of 10 to 400 nm, and the BET (Brunauer-Emmett-Teller) specific surface area of ​​the low-expansion silicon-carbon composite may be 200 m2 / g or less.

[0015] Additionally, the pitch may be manufactured based on petroleum residue.

[0016] Additionally, the carbon support may include a non-porous carbon support including at least one of hard carbon and soft carbon.

[0017] 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.

[0018] In addition, the porous carbon support may include 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.

[0019] 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 total pores of 0.09 or more, and the porosity of the surface portion of the porous carbon support may be greater than the porosity of the deep portion.

[0020]

[0021] In addition, the present invention provides a method for producing a low-expansion silicon-carbon composite, comprising the steps of: a first step of preparing a carbon-silicon composite particle including a carbon support including a surface portion and a core portion, and silicon disposed including a surface of the carbon support; a second step of coating a carbon coating layer-forming material on the surface of the carbon-silicon composite particle to produce a carbon-silicon composite particle coated with a carbon coating layer-forming material; and a third step of carbonizing the carbon-silicon composite particle coated with the carbon coating layer-forming material to form a carbon coating layer on the outermost surface of the carbon-silicon composite particle to produce a low-expansion silicon-carbon composite.

[0022] According to one embodiment of the present invention, the second step can be performed by dry-coating or wet-coating pitch on the surface of the carbon-silicon composite particles.

[0023] Additionally, in the above step 2, the carbon coating layer forming material can be coated in an amount of 4.0 to 30.0 parts by weight based on 100 parts by weight of the carbon-silicon composite particles.

[0024] Additionally, the above-mentioned two-step dry coating can be performed using a mechanofusion method. The rotation speed depends on the specific mechanofusion device, and the size of the processed batch, as well as the type of rotor and the number of associated paddles, can be appropriately adjusted by a person skilled in the art.

[0025] In addition, the above 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.

[0026] In addition, the wet coating of the second step can be performed by mixing the carbon-silicon composite particles with a coating solution containing the pitch and THF (Tetrahydrofuran), and then removing the THF. In a preferred example, the THF can be removed by a reduced pressure drying method.

[0027] Additionally, the above step 1 may include a step of depositing silicon (Si) including the surface of the carbon support.

[0028] In addition, the above deposition can be performed at a deposition temperature of 300°C to 600°C and in an atmosphere supplying silane (SiH4) gas of 50 sccm to 500 sccm per 10 g of porous carbon support.

[0029]

[0030] Another object of the present invention is to provide a cathode material characterized by including the low-expansion silicon-carbon composite described above.

[0031]

[0032] In addition, another object of the present invention is to provide a lithium ion battery and / or an all-solid-state battery including the above-described negative electrode material.

[0033] The low-expansion silicon-carbon composite 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 of optimal thickness, and further has the effect of suppressing and preventing the formation of a side-reaction layer by minimizing side reactions with electrolyte components. When such a low-expansion silicon-carbon composite is applied as an anode material for a secondary battery, the 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.

[0034]

[0035] Figure 1 shows a cross-section of the surface of a negative electrode material measured by SEM-EDS before operation of a half-cell in which a low-expansion silicon-carbon composite manufactured in Example 1 was introduced as a negative electrode material.

[0036] Figure 2 shows a cross-section of the surface of a negative electrode material measured by SEM-EDS after 50 cycles of operation of a half-cell in which a low-expansion silicon-carbon composite manufactured in Example 1 was introduced as a negative electrode material.

[0037] 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.

[0038] 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.

[0039] 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.

[0040] Hereinafter, the present invention will be described in more detail.

[0041] The low-expansion silicon-carbon composite of the present invention comprises: a carbon support including a surface portion and a core portion; carbon-silicon composite particles including silicon arranged including a surface of the carbon support; and a carbon coating layer arranged on the outermost surface of the carbon-silicon composite particles.

[0042] Meanwhile, the carbon coating layer may include carbide of pitch, and preferably may be formed of carbide of pitch derived from petroleum residue.

[0043] The above carbon coating layer 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 the 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 400 nm, preferably an average thickness of 30 to 200 nm, and more preferably an average thickness of 50 to 100 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 400 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.

[0044] Meanwhile, the BET specific surface area of ​​the low-expansion silicon-carbon composite may be 200 m2 / g or less, preferably 100 m2 / g or less, and more preferably 50 m2 / g or less. If the BET specific surface area of ​​the low-expansion silicon-carbon 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.

[0045]

[0046] The low-expansion silicon-carbon composite described above is manufactured by a manufacturing method including 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, the second step of coating a carbon coating layer-forming material on the surface of the carbon-silicon composite particles to manufacture carbon-silicon composite particles coated with the carbon coating layer-forming material, and the third step of carbonizing the carbon-silicon composite particles coated with the carbon coating layer-forming material to form a carbon coating layer on the outermost surface of the carbon-silicon composite particles to manufacture the low-expansion silicon-carbon composite.

[0047] The characteristics, physical properties and manufacturing method of the carbon-silicon composite particles of step 1 will be described later.

[0048] Meanwhile, the material for forming the carbon coating layer may preferably be pitch, and the second step may be performed by dry-coating or wet-coating pitch on the surface of the carbon-silicon composite particles.

[0049] The carbon coating layer forming material of the above-mentioned second step can be coated in an amount of 4.0 to 30.0 parts by weight, preferably 5.0 to 24.0 parts by weight, and more preferably 10.0 to 22.0 parts by weight, based on 100 parts by weight of the carbon-silicon composite particles, and the amount of the coated carbon coating layer forming material can be proportional to the thickness of the carbon coating layer. If the carbon coating layer forming material coated 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, and thus 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 carbon coating layer forming material coated exceeds 30 parts by weight, it is advantageous in terms of low expansion rate and suppression of side reaction layer formation, but the effect of increasing the electrical efficiency of the secondary battery may decrease.

[0050] The above-described two-step dry coating can be performed using a mechanofusion method. The rotation speed depends on the specific mechanofusion device, and the size of the processed batch, as well as the type of rotor and the number of associated paddles, can be appropriately adjusted by those skilled in the art.

[0051] As a preferred embodiment of the above mechanofusion method, after the prepared carbon-silicon composite particles are fed into a mechanofusion device, coating can be performed for 5 to 30 minutes, more 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. In addition, the rotation speed and time may be based on 15 g of silicon / carbon composite. By satisfying the conditions of the above mechanofusion method, it can be more advantageous to achieve the purpose of the present invention.

[0052] In addition, the wet coating of the above-mentioned second step can be performed by mixing the carbon-silicon composite particles with a coating solution containing the pitch 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, a preferred example of removing the THF is through reduced pressure drying, etc.

[0053] The low-expansion silicon-carbon composite of the present invention manufactured with the composition and method described above may have a thickness change rate of 30% or less, preferably 15 to 25%, measured according to the following measurement method 1.

[0054] [Measurement Method 1]

[0055] After applying a low-expansion silicon-carbon composite as an anode material of a half-cell for a lithium-ion battery, the thickness (㎛) of the anode material before operation was measured (A), and after operating the half-cell for 50 cycles, the thickness (㎛) of the anode material was measured (B), and the thickness change rate was measured according to the following equation 1.

[0056] [Formula 1]

[0057] Thickness change rate (%) = {(BA) / A} × 100(%)

[0058] In addition, the low-expansion silicon-carbon composite of the present invention may have a fluorine atom content of 15% or less, preferably 10% or less, as measured according to the following measurement method 2.

[0059] [Measurement Method 2]

[0060] After applying a low-expansion silicon-carbon composite as an anode material for a half-cell for a lithium-ion battery, the fluorine atomic content (weight %) of the anode material was measured after operating the half-cell for 50 cycles.

[0061]

[0062] Meanwhile, the carbonization treatment in the above three steps can be performed at a temperature of 600°C to 1,000°C, preferably 700°C to 900°C. If the temperature of the carbonization treatment is lower than this range, the carbonization treatment may not be sufficiently performed, and if the temperature of the carbonization treatment is higher than this range, it may be difficult to form a carbon coating layer having the desired uniform thickness, and the carbonization yield may decrease.

[0063] In addition, the above carbonization treatment can be performed without limitation by any method commonly used in the art, but is preferably performed by putting it into an electric furnace.

[0064] In addition, since the description of the above carbonization treatment may be the same as the description of the carbonization step (4) described below, a detailed description thereof will be omitted.

[0065]

[0066] Below, the carbon-silicon composite particles included in the low-expansion silicon-carbon composite are described in detail.

[0067] [Carbon-silicon composite particles]

[0068] The above 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.

[0069] In this specification, the core of the carbon support may mean an area within a distance of 1 / 2 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.

[0070] 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.

[0071]

[0072] 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.

[0073]

[0074] 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.

[0075] 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.

[0076] 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.

[0077] 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.

[0078] 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.

[0079] 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.

[0080] 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.

[0081] 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.

[0082] 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.

[0083] 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.

[0084] 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.

[0085] 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%.

[0086] 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.

[0087] 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.

[0088] 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.

[0089] 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.

[0090] 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.

[0091] 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).

[0092] 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.

[0093] And, in step (3), a step of stabilizing the pellet-shaped pitch or powder-shaped pitch can be performed. Specifically, step (3) may be a step of stabilizing the structure of the pitch by first oxidizing the pellet-shaped pitch or powder-shaped pitch.

[0094] 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.

[0095] 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.

[0096] 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.

[0097] 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.

[0098] 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.

[0099] 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.

[0100] 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.

[0101] 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.

[0102] 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.

[0103] 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.

[0104] 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.

[0105] 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.

[0106] 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.

[0107] 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.

[0108] 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.

[0109] 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.

[0110] 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.

[0111] 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, the classification may be dry classification, wet classification, or classification using a sieve. Through the pulverization or grounding and classification treatment, a powdered porous carbon support having a particle size distribution D50 of 1 to 20 μm can be obtained.

[0112] 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.

[0113] 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.

[0114] 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 the volume of mesopores to the total pore volume of 0.09 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.

[0115] 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.

[0116] 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.

[0117] 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.

[0118] 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.

[0119] In one example of the present invention, the BET (Brunauer-Emmett-Teller) 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, 2,000 ㎡ / g or less, or 1,900 ㎡ / g or less, but is not limited thereto. 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.

[0120] The diameter of the above porous carbon support may be 20 μm or less. The diameter is a particle size distribution 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.

[0121] 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 stress due to volume expansion during repeated charge and discharge processes, thereby causing damage to the negative electrode material.

[0122]

[0123] 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.

[0124] 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.

[0125] 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.

[0126]

[0127] 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.

[0128] 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.

[0129] 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.

[0130] 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.

[0131] 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.

[0132] 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.

[0133] 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, the crystal structure of carbon may not develop sufficiently, and if the temperature during the carbonization is higher than this range, the carbonization yield may decrease.

[0134] 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.

[0135] 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.

[0136] 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.

[0137] 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.

[0138]

[0139] 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.

[0140] At this time, if the carbon support is a porous carbon support, the silicon may be arranged within the pores of the surface and / or the deep portion of the porous carbon support. The silicon may be formed by deposition as described below.

[0141] 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.

[0142] 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 through X-ray fluorescence spectroscopy (XRF) or 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.

[0143]

[0144] 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.

[0145] At this time, the above step 1 may include a step of depositing silicon (Si) including the surface of the carbon support.

[0146] The above deposition can be performed at a deposition temperature of 300°C to 600°C and under an atmosphere supplying 50 sccm to 500 sccm of silane (SiH4) gas per 10 g of the carbon support.

[0147] The above deposition may be performed, for example, using chemical vapor deposition (CVD) and under atmospheric pressure conditions, but is not limited thereto. By the above deposition, silicon may be deposited, including on the surface of the carbon support according to the present invention.

[0148]

[0149] Furthermore, the present invention provides an anode material comprising the low-expansion silicon-carbon composite described above. Since the anode material comprises the low-expansion silicon-carbon composite described above, it can have improved mechanical strength along with high electrical capacity and excellent cycle characteristics.

[0150] 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.

[0151] 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.

[0152] 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.

[0153] 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.

[0154] 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.

[0155] 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.

[0156] 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.

[0157] 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.

[0158]

[0159] 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.

[0160] [Example]

[0161] Preparation Example 1: Preparation of porous carbon support and carbon-silicon composite particles

[0162] 300 g of petroleum residue 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 of 1 to 30 mm.

[0163] After crushing the solid pitch pellets obtained above (powdered pitch), they were placed in a rotary kiln with three zones to sequentially perform stabilization, carbonization, and activation. The conditions for stabilization, carbonization, and activation are as shown in Table 1 below.

[0164] The activated carbonized body, after the above activation, was pulverized using a pulverizer (NETZSCH, air jet mill) to produce a porous carbon support.

[0165] Step Condition Preparation Example 1 Stabilization temperature (℃) 310 hours (hr) 2 Atmosphere air carbonization temperature (℃) 900 hours (hr) 1 Atmosphere nitrogen activation temperature (℃) 900 hours (hr) 3 Water vapor flow rate (ml / min) 10

[0166]

[0167] 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 D50 of the carbon supports was measured using a particle size analyzer (Horiba, laser particle analyzer, LA-960V2) according to ASTM E112.

[0168] Example 1 of preparation for classification Particle size distribution D50 (㎛) 5.47 Specific surface area (m 2 / g)1665.9Tap density (g / ml)0.28Micropore (%)90.4Mesopore (%)9.4Macropore (%)0.2Mesopore ratio of surface layer0.68

[0169]

[0170] Carbon-silicon composite particles were prepared using the porous carbon support prepared above. 100 g of the porous carbon support was placed in a rotary kiln, and silane (SiH4) gas was injected to deposit the porous carbon support.

[0171] During silane gas coating, the pressure was atmospheric pressure, and the deposition was performed for 68 minutes at a temperature of 475°C and a flow rate of 1200 sccm, thereby producing carbon-silicon composite particles. The physical properties of the produced carbon-silicon composite particles are shown in Table 3 below.

[0172]

[0173] Example 1: Preparation of low-expansion silicon-carbon composites

[0174] For 100 parts by weight of the carbon-silicon composite particles manufactured in Preparation Example 1, 10 parts by weight of pitch derived from petroleum residue as a carbon coating layer forming material was introduced into the reactor of a mechanofusion device, and then coated for 15 minutes under conditions of a blade rotation speed of 900 rpm to manufacture pitch-coated carbon-silicon composite particles.

[0175] Next, after putting the pitch-coated carbon-silicon composite particles into an electric furnace, the temperature was increased to 700°C at 10°C / min, carbonization was performed at 700°C for 2 hours, and then slowly cooled to 25°C to form a 50 nm thick carbon coating layer (pitch carbonization layer) on the surface of the carbon-silicon composite particles, thereby manufacturing a low-expansion silicon-carbon composite.

[0176]

[0177] Examples 2-3

[0178] A low-expansion silicon-carbon composite having a carbon coating layer (pitch carbon layer) of the same thickness formed in the same manner as Example 1 was manufactured, but when manufacturing the carbon-silicon composite particles, the blade rotation speed of the mechanofusion equipment was changed as shown in Table 3 below, and Examples 2 and 3 were each performed.

[0179]

[0180] Comparative Example 1

[0181] Comparative Example 1 prepared carbon-silicon composite particles manufactured in Preparation Example 1 (excluding carbon coating layer).

[0182] ClassificationExample 1Example 2Example 3Comparative Example 1 Low-expansion Si-C composite carbon coating layer forming materialCoating amount 10 parts by weight (based on 100 parts by weight of C-Si composite particles)Carbon-silicon composite particles (Preparation Example 1)Rotation speed (rpm) 3000 3000 4000 Hours (min) 1520 20Carbon coating layer thickness (nm) 581 161 51Particle size distribution D50 (㎛) 7.80 8.12 8.10 7.81Specific surface area (m 2 / g)255138238Tab density (g / ml)0.610.630.600.58

[0183]

[0184] Experimental Example 1: Electrochemical Evaluation of Secondary Batteries

[0185] Half coin cells were manufactured by applying each of the low-expansion Si-C composites manufactured in Examples 1 to 3 and the C-Si composite particles of Comparative Example 1.

[0186] A slurry was prepared by mixing a sample (90 wt% graphite and 10 wt% each of the low-expansion Si-C composites of Examples 1 to 3 and the C-Si composite particles of Comparative Example 1): conductive agent: binder in a ratio of 8:1:1. At this time, the conductive agent used super-P, and the binder used a mixture of styrene butadiene rubber (SBR) and sodium carboxymethyl cellulose (CMC) in a weight ratio of 5:5.

[0187] 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 produce a negative electrode material.

[0188] A half coin cell was manufactured using the above-mentioned negative electrode material 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 4 below.

[0189] 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 4).

[0190] Composition (AM:CM:BM) 96:1:3 Area capacity (mAh / cm 2 )2 Electrolyte 1.3M LiPF6 EC / EMC / DMC 3:5:2, FFC 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

[0191]

[0192] In Table 4 above, AM, CM, and BM represent active materials (90 wt% graphite and 10 wt% each of the low-expansion Si-C composites of Examples 1 to 3 and the C-Si composite particles of Comparative Example 1), conductors (Super P carbon black), and binders (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.

[0193] Electrochemical analysis was performed on the manufactured half coin cell under the following conditions.

[0194] Cut off voltage (V): 0.005 - 1.5V (Formation), 0.005 - 1.2V(Cycle)

[0195] Formation C-rate (C): 0.1C lithiation, 0.1C delithiation

[0196] Cycle C-rate (C): 0.5C lithiation, 0.5C delithiation

[0197] In addition, the thickness (㎛) of the negative electrode material before driving the half-cell was measured (A), and the thickness (㎛) of the negative electrode material was measured after driving the half-cell for 50 cycles (B), and the thickness change rate was measured based on the following equation 1. After driving the half-cell for 50 cycles, the fluorine atom content (weight %) of the negative electrode material was measured and shown in Table 5 below.

[0198] At this time, the fluorine atom content of the negative electrode material was measured on a SEM-EDS at 1000x magnification after cutting the cross-section of the negative electrode material, and the fluorine atom content was measured based on a total of 100 wt% of C, O, F, and Si.

[0199] [Formula 1]

[0200] Thickness change rate (%) = {(BA) / A} × 100(%)

[0201] In addition, the cross-section of the surface of the negative electrode material before operation of Manufacturing Example 1 (Fig. 1) and the cross-section of the negative electrode material after 50 cycles of operation (Fig. 2) were measured by SEM-EDS and are shown in Figs. 1 and 2, respectively.

[0202] After the initial 50 cycles of operation, the half-cell sample was charged and discharged. The initial efficiency was %), and the thickness change rate was %). The fluorine atom content was %). The initial capacity was maintained %. Manufacturing Example 1: Example 155950690.5246.8101.4. Manufacturing Example 2: Example 255349689.7214.9100.7. Manufacturing Example 3: Example 355548487.22111.7101.9. Comparative Manufacturing Example 1: Comparative Example 155955293.45117.187.4.

[0203]

[0204] As can be seen in Table 5 above, Manufacturing Examples 1 to 3, which applied Examples 1 to 3 including a carbon coating layer, had lower thickness change rate and fluorine atom content and significantly better capacity retention rate than Comparative Manufacturing Example 1, which applied Comparative Example 1 not including a carbon coating layer.

[0205]

[0206] Preparation Example 2: Preparation of hard carbon and carbon-silicon composite particles

[0207] 300 g of petroleum residue 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 of 1 to 30 mm.

[0208] 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 6 below.

[0209] Afterwards, the carbon support was pulverized using a pulverizer (NETZSCH, air jet mill).

[0210] At this time, the specific surface area of ​​the carbon support (hard carbon) was measured using Belsorp mini II according to ASTM D4820-93. The tap density of the carbon support was measured using a tap density analyzer (Electrolab, ETD-1020x) according to ASTM B527. The average particle size of the carbon support was measured using a particle size analyzer (Horiba, laser particle analyzer, LA-960V2) according to ASTM E112.

[0211] Furthermore, carbon-silicon composite particles were manufactured using the hard carbon support manufactured above. 15 g of the carbon support was placed in a rotary kiln, and silane (SiH4) gas was injected to deposit silicon on the carbon support. The silicon deposition conditions and the physical properties of the carbon-silicon composite particles are shown in Table 6 below.

[0212]

[0213] Preparation Example 3: Preparation of soft carbon and carbon-silicon composite particles

[0214] 300 g of petroleum residue 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 of 1 to 30 mm.

[0215] 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 6 below.

[0216] Afterwards, the carbon support was pulverized using a pulverizer (NETZSCH, air jet mill).

[0217] At this time, the specific surface area of ​​the carbon support (soft carbon) was measured using Belsorp mini II according to ASTM D4820-93. The tap density of the carbon support was measured using a tap density analyzer (Electrolab, ETD-1020x) according to ASTM B527. The average particle size of the carbon support was measured using a particle size analyzer (Horiba, laser particle analyzer, LA-960V2) according to ASTM E112.

[0218] Furthermore, carbon-silicon composite particles were manufactured using the soft carbon support manufactured above. 15 g of the carbon support was placed in a rotary kiln, and silane (SiH4) gas was injected to deposit silicon on the carbon support. The silicon deposition conditions and the physical properties of the carbon-silicon composite particles are shown in Table 6 below.

[0219]

[0220] Step Condition Preparation Example 2 Preparation Example 3 Stabilization temperature (℃) 300 300 Hours (hr) 33 Atmosphere Air Air Carbonization temperature (℃) 900 1600 Hours (hr) 11 Atmosphere Nitrogen Argon Carbon Support Properties Average particle size (㎛) 49.7 5 0.1 Specific surface area (㎡ / g) 24 Tap density (g / ml) 0.66 4 0.88 2 Particle size distribution after grinding D50 (㎛) 4.9 5.6 Silicon deposition conditions Pressure Normal pressure Normal pressure Temperature (℃) 475 475 Silane flow rate (sccm) 300 300 Hours 60 60 Carbon-silicon composite particles Silicon content (wt%) 34.9 3 1.4 Particle size distribution D50 (㎛) 11.6 10.7 Specific surface area (㎡ / g) 0.5 1.4 Silicon layer thickness (nm) 84 1 1

[0221]

[0222] Examples 4 and 5

[0223] The same procedure as Example 1 was followed, but the carbon-silicon composite particles according to Preparation Example 1 were changed to carbon-silicon composite particles according to Preparation Examples 2 and 3, and Examples 4 and 5 were performed, respectively, to manufacture a low-expansion silicon-carbon composite.

[0224]

[0225] Experimental Example 2: Electrochemical Evaluation of Secondary Batteries

[0226] An electrochemical evaluation was performed using the same method as in Experimental Example 1, but using low-expansion silicon-carbon composites according to Examples 4 and 5 as samples. The results are shown in Table 7 below.

[0227] After the initial 50 cycles of operation, the half-cell sample was charged and discharged. The initial efficiency was %), and the thickness change rate was %). The fluorine atom content was %). The initial capacity was maintained %. Manufacturing Example 4: Example 4 50745890.3244.661.5. Manufacturing Example 5: Example 5 50345390.0256.760.0.

[0228]

[0229] As can be seen from Table 7 above, Manufacturing Examples 4 and 5, which satisfied the carbon support type of the present invention and applied Examples 4 and 5 including a carbon coating layer, were confirmed to have low thickness change rate and fluorine atom content change rate and excellent capacity retention rate.

[0230]

[0231] 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 defined in the claims, and such modifications are also within the scope of the present invention.

Claims

1. Carbon-silicon composite particles comprising a carbon support including a surface layer and a core layer, and silicon arranged including the surface of the carbon support; and A low-expansion silicon-carbon composite, characterized by comprising a carbon coating layer disposed on the outermost surface of the carbon-silicon composite particles.

2. In paragraph 1, The above carbon coating layer contains carbide of pitch, and the carbon coating layer has an average thickness of 10 to 400 nm. A low-expansion silicon-carbon composite characterized in that the BET (Brunauer-Emmett-Teller) specific surface area of ​​the low-expansion silicon-carbon composite is 200 m2 / g or less.

3. In paragraph 2, The above pitch is a low-expansion silicon-carbon composite characterized in that it is manufactured based on petroleum residue.

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

5. In paragraph 1, The above carbon support comprises a porous carbon support, A low-expansion silicon-carbon composite characterized in that the silicon is disposed on the surface and inside the pores of the porous carbon support.

6. In paragraph 5, The above porous carbon support comprises mesopores having a diameter of 2 nm to 50 nm, A low-expansion silicon-carbon composite characterized in that the ratio of the volume of mesopores of the surface layer to the volume of the entire mesopores of the porous carbon support is 0.5 to 0.

76.

7. In paragraph 5, The above porous carbon support has a ratio of the volume of mesopores to the volume of the total pores of 0.09 or more, The above porous carbon support is a low-expansion silicon-carbon composite characterized in that the porosity of the surface layer is greater than that of the deep layer.

8. Step 1 of preparing carbon-silicon composite particles including a carbon support including a surface portion and a deep portion, and silicon arranged including the surface of the carbon support; Step 2: manufacturing carbon-silicon composite particles coated with a carbon coating layer forming material by coating the surface of the carbon-silicon composite particles with a carbon coating layer forming material; and A method for producing a low-expansion silicon-carbon composite, characterized by comprising the step of: carbonizing carbon-silicon composite particles coated with a carbon coating layer forming material to form a carbon coating layer on the outermost surface of the carbon-silicon composite particles; 9. In paragraph 8, A method for manufacturing a low-expansion silicon-carbon composite, characterized in that the above-mentioned second step is performed by dry-coating or wet-coating pitch on the surface of the carbon-silicon composite particles.

10. In paragraph 8, A method for manufacturing a low-expansion silicon-carbon composite, characterized in that in the above step 2, the carbon coating layer forming material is coated in an amount of 4.0 to 30.0 parts by weight based on 100 parts by weight of the carbon-silicon composite particles.

11. In paragraph 9, The above 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, characterized in that coating is performed for 5 to 30 minutes under conditions of a blade rotation speed of 500 to 5,000 rpm of a mechanofusion device.

12. In paragraph 9, A method for manufacturing a low-expansion silicon-carbon composite, characterized in that the wet coating of the above two steps is performed by mixing the carbon-silicon composite particles with a coating solution containing the pitch and THF (Tetrahydrofuran), and then removing the THF.

13. In paragraph 8, Step 1 above is, A method for producing a low-expansion silicon-carbon composite, characterized by comprising a step of depositing silicon (Si) including the surface of the carbon support.

14. In paragraph 13, A method for producing a low-expansion silicon-carbon composite, characterized in that the above deposition is performed at a deposition temperature of 300°C to 600°C and in an atmosphere supplying 50 sccm to 500 sccm of silane (SiH4) gas per 10 g of the carbon support.

15. A cathode material characterized by comprising a low-expansion silicon-carbon composite according to any one of claims 1 to 7.

16. A lithium ion battery comprising a negative electrode material according to Article 15.

17. An all-solid-state battery comprising a negative electrode material according to Article 15.

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