Carbon-silicon / oxide composite, manufacturing method therefor, and silicon negative electrode material including same

Abstract

The present invention relates to a carbon-silicon / oxide composite used for a silicon negative electrode material, a manufacturing method therefor, and a silicon negative electrode material using same. More specifically, the present invention relates to: a silicon-carbon composite that can reduce volume expansion of the composite while suppressing side reactions with an electrolyte caused by the leakage of silicon from the carbon-silicon / oxide composite; a manufacturing method therefor; and a silicon negative electrode material using same.

Description

Carbon-silicon / oxide composite, method for producing the same, and silicon anode material comprising the same

[0001] The present invention relates to a negative electrode material of a lithium-ion battery and / or an all-solid-state battery, which 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 a side reaction with an electrolytic component. The present invention relates to a carbon-silicon / oxide composite capable of minimizing such volume expansion and side reaction with an electrolytic component, a method for producing the same, and a silicon negative electrode material 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 reduces 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] [Prior Art Literature]

[0011] [Patent Document]

[0012] (Patent Document 001) Republic of Korea Publication No. 10-2019-0093960 (Published on August 12, 2019)

[0013] (Patent Document 002) U.S. Patent No. 4,242,196 (registration date: December 30, 1980)

[0014] 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 a side reaction with the electrolyte component. Specifically, when silicon comes into contact with an electrolyte, gas is generated due to a side reaction, which reduces the lifespan of the battery. In addition, although a carbon coating method has high lifespan stability, there is a problem in that a portion of the silicon is crystallized and forms silicon carbide during the carbonization process, which reduces the capacity. Accordingly, the present invention provides a carbon-silicon / oxide composite that forms a silicon oxide layer on the surface of the carbon-silicon composite to minimize such volume expansion and side reactions with the electrolyte component, thereby achieving minimized volume expansion and side reactions, a method for manufacturing the same, a silicon 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.

[0015] The carbon-silicon / oxide composite of the present invention for solving the above problem comprises a carbon-silicon composite including a porous carbon support including a surface portion and a deep portion, a silicon deposition layer formed on the porous carbon support, and a silicon oxide layer formed on the carbon-silicon composite.

[0016] As a preferred embodiment of the present invention, the silicon deposition layer may have a Si intensity ratio of 25 to 60% according to the following equation 1 when measured by XPS (X-ray Photoelectron Spectroscope).

[0017] [Formula 1]

[0018] Si intensity ratio = Si peak intensity / (Si peak intensity + SiO2 peak intensity) * 100%

[0019] In Equation 1, the Si peak intensity is the intensity of the Si 2p peak appearing at 99.9 eV, and the SiO2 peak intensity is the peak intensity appearing at 103.5 eV.

[0020] As a preferred embodiment of the present invention, the silicon oxide layer may be formed by oxidizing the surface of a silicon deposition layer.

[0021] As a preferred embodiment of the present invention, the silicon oxide layer may have an average thickness of 5 to 100 nm.

[0022] As a preferred embodiment of the present invention, the carbon-silicon / oxide composite may have an oxygen (O) content of 10 to 30 wt% as measured by a scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS).

[0023] As a preferred embodiment of the present invention, the carbon-silicon / oxide composite may have a silicon (Si) content of 20 to 60% as measured by X-ray fluorescence spectroscopy (XRF).

[0024] As a preferred embodiment of the present invention, the porous carbon support may include mesopores having a diameter of 2 nm to 50 nm.

[0025] As a preferred embodiment of the present invention, 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 50 to 76%.

[0026] 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 10% or more.

[0027] As a preferred embodiment of the present invention, the porous carbon support may have a surface porosity greater than a deep porosity.

[0028] In a preferred embodiment of the present invention, the BET of the carbon-silicon / oxide composite is 200 m 2 / g or less, the average particle size may be 5 to 15 ㎛, and the tap density may be 0.50 to 0.80 g / ml.

[0029]

[0030] In addition, the method for manufacturing a carbon-silicon / oxide composite of the present invention includes a first step of preparing a carbon-silicon composite including a porous carbon support including a surface portion and a deep portion and a silicon deposition layer formed on the porous carbon support, and a second step of oxidizing the carbon-silicon composite to form a silicon oxide layer on the surface of the silicon deposition layer.

[0031] As a preferred embodiment of the present invention, the oxidation treatment in the second step can be performed by heat treatment at 90 to 550°C in an air or oxygen atmosphere.

[0032] As a preferred embodiment of the present invention, the heat treatment may be performed in a rotary kiln, and may be performed while injecting air or oxygen at a rotation speed of 1 to 10 rpm and a flow rate of 500 to 4,500 ml / min.

[0033] As a preferred embodiment of the present invention, the carbon-silicon composite of step 1 may be manufactured by performing a process including step 1-1 of preparing a porous carbon support having mesopores having a diameter of 2 nm to 50 nm and a ratio of the volume of mesopores in the surface layer to the volume of the entire mesopores of 50 to 76%; and step 1-2 of depositing silicon (Si) on the porous carbon support.

[0034] As a preferred embodiment of the present invention, the deposition in steps 1 and 2 can be performed at a deposition temperature of 300°C to 600°C and under an atmosphere supplying silane (SiH4) gas.

[0035] As a preferred embodiment of the present invention, the carbon-silicon / oxide composite may have an oxygen content increase rate of 100 to 400% according to the following formula 2.

[0036] [Formula 2]

[0037] Oxygen content increase rate (%) = {(BA) / A} * 100(%)

[0038] In Equation 2, A and B are the oxygen contents (%) measured by SEM (scanning electron microscope) and EDS (energy dispersive spectroscopy), A is the oxygen content (%) on the surface of the carbon-silicon composite of step 1, and B is the oxygen content (%) on the surface of the carbon-silicon / oxide composite manufactured by performing step 2.

[0039]

[0040] Another object of the present invention is to provide a silicon anode material comprising the carbon-silicon / oxide composite described above.

[0041] In addition, another object of the present invention is to provide a lithium ion battery and / or an all-solid-state battery including the silicon negative electrode material.

[0042] The carbon-silicon / oxide composite of the present invention has low expansion properties due to the presence of a silicon oxide layer of optimal thickness, thereby suppressing volume expansion caused by lithium ion insertion into the composite, and further has the effect of suppressing and preventing the formation of a side reaction layer by minimizing side reactions with electrolyte components caused by silicon outflow. When such a carbon-silicon / oxide composite is applied as a silicon anode material for 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.

[0043] 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.

[0044] 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.

[0045] 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.

[0046] The silicon oxide layer described herein may be implemented by including SiOx.

[0047] Hereinafter, the present invention will be described in more detail.

[0048] The carbon-silicon / oxide composite of the present invention is a composite in which a silicon oxide layer is formed on the surface of a silicon deposition layer by oxidizing a carbon-silicon composite, wherein the carbon-silicon composite includes a porous carbon support including a surface portion and a deep portion, and a silicon (Si) deposition layer formed on the porous carbon support, and a silicon oxide layer is formed on the carbon-silicon composite.

[0049] The above silicon oxide layer is formed by oxidizing the surface of the carbon-silicon composite, i.e., the silicon deposition layer, and when the carbon-silicon / oxide composite is used as an anode material of a secondary battery, it serves to minimize volume expansion of the carbon-silicon / oxide composite due to lithium ion insertion and to minimize the formation of a side reaction layer formed by the reaction of F in the electrolyte and the anode material component. The average thickness may be 5 to 100 nm, preferably the average thickness may be 5 to 50 nm, and more preferably the average thickness may be 10 to 30 nm. At this time, if the average thickness of the silicon oxide layer is less than 5 nm, the thickness is insufficient, and the effect of suppressing the increase in the expansion rate of the carbon-silicon / oxide composite as a negative electrode material may be insufficient. If the average thickness of the silicon oxide layer exceeds 100 nm, it is advantageous in terms of low expansion rate and suppression of side reactions with the electrolyte component, but the effect of increasing the electrical efficiency of the secondary battery may be reduced due to the decrease in electrical conductivity and ionic conductivity. Therefore, it is appropriate to form it with a thickness within the above range.

[0050] Additionally, the carbon-silicon / oxide composite may have an oxygen (O) content of 10 to 30%, preferably 12.0 to 23.0%, as measured by a scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS).

[0051] Additionally, the carbon-silicon / oxide composite may have a silicon (Si) content of 20 to 60%, preferably 46.0 to 59.0%, as measured by X-ray fluorescence spectroscopy (XRF).

[0052] Additionally, the carbon-silicon / oxide composite has a BET surface area of ​​200.0 m 2 / g or less, preferably 100.0 to 200.0 m 2 / g, more preferably 120.0 to 200.0 m 2 / g could be.

[0053] Additionally, the carbon-silicon / oxide composite may have a tap density of 0.50 to 0.80 g / ml, preferably 0.54 to 0.65 g / ml, and more preferably 0.56 to 0.63 g / ml.

[0054] Additionally, the carbon-silicon / oxide composite may have an average particle size of 5 to 15 μm, and preferably an average particle size of 5.5 to 14 μm.

[0055] As the above carbon-silicon / oxide composite satisfies the oxygen content range, silicon content range, BET specific surface area range, tap density range, and average particle size range, it can be more advantageous in achieving the purpose of the present invention.

[0056]

[0057] The carbon-silicon / oxide composite described above is manufactured by performing a process including the first step of preparing a carbon-silicon composite including a porous carbon support including a surface portion and a deep portion and a silicon deposition layer formed on the porous carbon support; and the second step of oxidizing the carbon-silicon composite to form a silicon oxide layer on the surface of the silicon deposition layer.

[0058] The specific characteristics, properties and manufacturing method of the carbon-silicon composite of the above step 1 will be described later.

[0059] The oxidation treatment in the above two steps can be performed by heat treatment at 90 to 550°C, preferably 200 to 520°C, more preferably 350 to 520°C, for 20 to 90 minutes, preferably 20 to 70 minutes, in an air (or oxygen (additional)) atmosphere. At this time, if the heat treatment temperature is less than 90°C, the oxidation treatment may not proceed well, and if it exceeds 550°C, there may be a problem in that crystalline silicon in the silicon deposition layer of the carbon-silicon composite increases or silicon carbide is generated. Therefore, it is appropriate to perform the oxidation treatment within the above temperature range and time.

[0060] In addition, the heat treatment can be performed in a rotary kiln, and is advantageous in forming a silicon oxide layer of an appropriate thickness and an appropriate oxygen content when performed while injecting air or oxygen at a rotation speed of 1 to 10 rpm and a flow rate of 500 to 4,500 ml / min, preferably at a rotation speed of 1 to 8 rpm and a flow rate of 900 to 4,200 ml / min.

[0061] For example, the method can be performed by injecting air or oxygen at a rotation speed of 4 to 8 rpm and a flow rate of 1,000 to 4,200 ml / min, preferably at a rotation speed of 4 to 6 rpm and a flow rate of 2,000 to 4,200 ml / min.

[0062] The carbon-silicon / oxide composite manufactured by performing the above steps may have an oxygen content increase rate of 100 to 400%, preferably 150 to 350%, and more preferably 170 to 350% according to the following formula 2.

[0063] [Formula 2]

[0064] Oxygen content increase rate (%) = {(BA) / A} * 100(%)

[0065] In Equation 2, A and B are the oxygen contents (%) measured by SEM (scanning electron microscope) and EDS (energy dispersive spectroscopy), A is the oxygen content (%) on the surface of the carbon-silicon composite of step 1, and B is the oxygen content (%) on the surface of the carbon-silicon / oxide composite manufactured by performing step 2.

[0066]

[0067] Below, the carbon-silicon composite constituting the carbon-silicon / oxide composite is described in detail.

[0068] [Carbon-silicon composite]

[0069] In the carbon-silicon / oxide composite of the present invention, the carbon-silicon composite comprises a porous carbon support including a surface portion and a core portion, and a silicon deposition layer formed on the porous carbon support. The silicon deposition layer may be deposited and present on the surface portion and / or the core portion of the porous carbon support.

[0070] In this specification, the core of the porous 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.

[0071] The above porous carbon support may be a commercially available one, and preferably, one manufactured by the following method may be used.

[0072]

[0073] [Porous carbon support]

[0074] A porous carbon support powder according to one embodiment of the present invention can be manufactured by a method including the steps of (1) synthesizing pitch by thermal decomposition and polycondensation of a petroleum-based raw material, (2) solidifying the pitch to obtain a solid pitch, (3) stabilizing the pitch, (4) carbonizing the stabilized pitch to obtain a carbonized body, and (5) activating the carbonized body to obtain a porous carbon support.

[0075] Step (1)

[0076] 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.

[0077] 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 oil (RFCC-DO), 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.

[0078] 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.

[0079] 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.

[0080] 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.

[0081] 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.

[0082] 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.

[0083] 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.

[0084] 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.

[0085] 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.

[0086] 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.

[0087] 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%.

[0088] 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.

[0089] 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.

[0090] 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.

[0091] Step (2)

[0092] In step (2) of a process for manufacturing a porous carbon support powder from a petroleum-based raw material according to one embodiment of the present invention, pitch can be solidified to obtain a solid pitch.

[0093] The liquid pitch obtained in step (1) is solidified, for example, by extrusion and cooling, to obtain a solid pitch. The process of extruding, cooling, and solidifying the liquid pitch to obtain a solid pitch 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.

[0094] The pitch obtained in step (2) has an average particle size of 1 to 30 mm, preferably 5 to 25 mm. When the average particle size of the pitch is within this range, a porous carbon support can be manufactured through stabilization, carbonization, and activation described below without separately pulverizing the pitch.

[0095] However, if necessary, the pitch obtained in step (2) may be further crushed or pulverized and classified. The pitch can be further finely divided through crushing or pulverization, and the particle size distribution of the pitch can be made uniform through classification. Here, classification can be performed by dry classification, wet classification, or classification using a sieve. By crushing or pulverizing and classification, powdered pitch having a diameter of 50 to 500 μm can be obtained.

[0096] Step (3)

[0097] Step (3) of the method for manufacturing a porous carbon support powder according to the present invention may be a step for stabilizing a solid pitch. Specifically, it may be a step for stabilizing the structure of the solid pitch by first oxidizing the solid pitch. If the solid pitch is pulverized in step (2), this step may be a step for stabilizing the pulverized powder pitch.

[0098] 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 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.

[0099] In a specific embodiment of the present invention, the stabilization of the pitch can be performed at a pressure of 0.1 to 10.0 bar, preferably 0.5 to 5.0 bar. When the stabilization of the pitch is performed at this pressure, the structure of the pitch can be sufficiently stabilized, even up to the carbon inside the pitch.

[0100] In a specific embodiment of the present invention, the stabilization of the pitch 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 of the pitch is performed under these oxidizing gas flow rates, the structure of the pitch, including the carbon within the pitch, can be sufficiently stabilized.

[0101] In a specific embodiment of the present invention, the pitch stabilization may be performed for 1 to 10 hours, preferably 2 to 8 hours. If the pitch stabilization is performed for this period of time, the structure of the pitch, including the carbon within the pitch, can be sufficiently stabilized.

[0102] Step (4)

[0103] Step (4) of the method for manufacturing a porous carbon support according to the present invention may be a step of carbonizing stabilized pitch to obtain a carbonized body. Through carbonizing the pitch, other functional groups contained in the pitch are removed, and a carbonized body composed of substantially pure carbon can be obtained.

[0104] In a specific embodiment of the present invention, the carbonization of the pitch 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.

[0105] In a specific embodiment of the present invention, carbonization of the pitch may be performed at a temperature of 700°C to 1,000°C or 800°C to 1,000°C. If the temperature during carbonization of the pitch is lower than this range, carbonization may not be sufficiently performed, and if the temperature during carbonization of the pitch is higher than this range, the carbonization yield may decrease.

[0106] In a specific embodiment of the present invention, the carbonization of the pitch can be performed under a flow rate condition of an inert gas, preferably nitrogen, of 0.1 to 30.0 ml / min, preferably 0.1 to 10.0 ml / min. When the carbonization of the pitch is performed under these inert gas flow rates, the pitch can be sufficiently carbonized.

[0107] In a specific embodiment of the present invention, the carbonization of the pitch may be performed for 0.5 to 5.0 hours, preferably 1 to 3 hours. If the carbonization of the pitch is performed for this period of time, the pitch can be sufficiently carbonized.

[0108] Step (5)

[0109] In the method for manufacturing a porous carbon support according to the present invention, in step (5), a porous carbon support can be obtained by activating a carbonized body. By activating the carbonized body (carbonized pitch), pores are formed in the pitch, thereby obtaining a porous carbon support.

[0110] 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.

[0111] In a specific embodiment of the present invention, 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 activation of the carbonized body is performed at this temperature, a porous carbon support in which micropores and mesopores are sufficiently formed can be obtained.

[0112] In a specific embodiment of the present invention, activation of the carbonized body can be performed at a pressure of 0.1 to 10.0 bar, preferably 0.1 to 5.0 bar. When activation of the carbonized body is performed at this pressure, a porous carbon support in which micropores and mesopores are sufficiently formed can be obtained.

[0113] In a specific embodiment of the present invention, the activation of the carbonized body can be performed under conditions of a flow rate of an oxidizing gas, preferably water vapor, of 0.1 to 100.0 ml / min, preferably 0.1 to 50.0 ml / min. When the activation of the carbonized body is performed under these oxidizing gas flow rates, a porous carbon support in which micropores and mesopores are sufficiently formed can be obtained.

[0114] In a specific embodiment of the present invention, the activation of the carbonized body may be performed for 0.5 to 5.0 hours, preferably 1 to 3 hours. When the activation of the carbonized body is performed for this period of time, a porous carbon support in which micropores and mesopores are sufficiently formed can be obtained.

[0115] In a specific embodiment of the present invention, steps (3) to (5) above may each be performed in a heating furnace using microwaves. In a preferred specific embodiment of the present invention, steps (3) to (5) above may 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 pellets themselves without increasing the external temperature of the pitch pellets, but is not particularly limited thereto.

[0116] In a specific embodiment of the present invention, steps (3) to (5) above can be performed continuously in a single device. In a preferred embodiment of the present invention, steps (3) to (5) above can be performed continuously in a single rotary kiln, but this device is not particularly limited. Since stabilization, carbonization, and activation of pitch pellets are performed continuously in a single device, process optimization can be easily achieved.

[0117] 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.

[0118] 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 50% or more, preferably 50 to 76%. When the ratio of the mesopores of the surface layer to the volume of the entire mesopores of the porous carbon support is 50% 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 entire mesopores of the porous carbon support may refer to the volume of the entire 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 entire 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.

[0119] At this time, if the ratio of the mesopores of the surface layer to the total mesopores of the carbon-silicon composite is outside the above range, the charge / discharge capacity may decrease and the cycle characteristics may deteriorate.

[0120] In one example of the present invention, the porous carbon support of the carbon-silicon composite according to the present invention may have a mesopore volume ratio of 10% or more to the total pore volume. 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 / discharge processes, which can mechanically damage the negative electrode material.

[0121] On the other hand, in the case of mesopores, silicon can be sufficiently deposited deep within the pores during deposition. The carbon-silicon composite 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.

[0122] The porous carbon support may have a ratio of the volume of mesopores to the volume of the entire pores, but is not limited thereto. The upper limit of the ratio of the volume of mesopores to the volume of the entire pores of the porous carbon support is not particularly limited, but may be, for example, 70% or less, 60% or less, 50% or less, or 40% or less. When the ratio of the volume of mesopores to the volume of the entire pores of the porous carbon support of the carbon-silicon composite satisfies the above range, the porous carbon support of the carbon-silicon composite has excellent electrical properties, while preventing excessive aggregation of silicon, thereby preventing damage due to volume expansion of silicon.

[0123] In one embodiment of the present invention, the tap density of the porous carbon support of the carbon-silicon composite may be 0.70 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 of the carbon-silicon composite is too low, process control may be difficult during silane gas deposition, which may result in a decrease in yield. In addition, if the tap density of the porous carbon support of the carbon-silicon composite is too high, uniform coating may be difficult during silane gas deposition.

[0124]

[0125] In one example of the present invention, the BET specific surface area of ​​the porous carbon support among the carbon-silicon composite compositions 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 of the carbon-silicon composite is excessively low, the proportion of macropores may increase, which may reduce the mechanical strength of the negative electrode material and result in a lack of effective pores. Furthermore, if the BET surface area of ​​the porous carbon support of the carbon-silicon composite is excessively high, the proportion of micropores may increase, and silicon may not be sufficiently deposited deep into the porous carbon support.

[0126] The diameter of the porous carbon support of the above carbon-silicon composite may be 20 μm or less. The diameter is D 50It can mean the diameter, and can be a value measured using MICROTRAC S3500 equipment. Specifically, it can mean the average value obtained by performing particle size analysis three times after dispersing the porous carbon support in ethanol. The diameter of the porous carbon support can be 20 ㎛ or less, 18 ㎛ or less, 16 ㎛ or less, 14 ㎛ or less, 12 ㎛ or less, or 10 ㎛ or less, and can 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 of the carbon-silicon composite 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.

[0127] In one example, the porous carbon support of the carbon-silicon composite according to the present invention may include macropores having a diameter exceeding 50 nm. In this case, the ratio of the volume of the macropores to the total pore volume of the porous carbon support may be 40% or less. The ratio of the volume of the macropores to the total pore volume of the porous carbon support may be 40% or less, 35% or less, 30% or less, 25% or less, 20% or less, or 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. If the ratio of the macropores of the porous carbon support of the carbon-silicon composite is too high, the mechanical strength of the negative electrode material manufactured from the carbon-silicon composite 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.

[0128]

[0129] The silicon (Si) deposition layer included in the carbon-silicon composite according to the present invention may be formed on the surface of the porous carbon support, inside and / or outside the pores of the surface and / or deep portion. The silicon may be formed by deposition as described below.

[0130] Since the carbon-silicon composite according to the present invention has the above structure, the negative electrode material manufactured using the carbon-silicon / oxide composite according to the present invention can have a high electrical capacity while minimizing the influence due to volume expansion of silicon.

[0131] In another example, the silicon content (or the content of the silicon deposition layer) of the carbon-silicon composite according to the present invention may be 10 wt% or more based on the total weight of the carbon-silicon composite. The silicon content of the carbon-silicon composite may be a value obtained by analysis using an energy dispersive spectrometer (EDS) or X-ray fluorescence (XRF).

[0132] The content of silicon (or silicon deposition layer) in the carbon-silicon composite may be, but is not limited to, 10 wt% or more, 15 wt% or more, 20 wt% or more, 25 wt% or more, or 30 wt% or more. In addition, the content of silicon (or silicon deposition layer) in the carbon-silicon composite may be, but is not limited to, 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. If the content of silicon (or silicon deposition layer) in the carbon-silicon composite is too low, the electric capacity may decrease, and if the content of silicon (or silicon deposition layer) is too large, the volume expansion rate of silicon increases during charge and discharge, which may cause structural damage to the negative electrode material and deteriorate the cycle characteristics.

[0133]

[0134] In addition, the silicon (Si) deposition layer formed by oxidizing the carbon-silicon composite may be at least partially oxidized to form a silicon oxide (SiOx) layer, and the silicon deposition layer may have an Si intensity ratio of 25 to 60% according to the following equation 1 when measured by XPS (X-ray Photoelectron Spectroscope), and preferably 27 to 56%.

[0135] [Formula 1]

[0136] Si intensity ratio = Si peak intensity / (Si peak intensity + SiO2 peak intensity) * 100%

[0137] In Equation 1, the Si peak intensity is the intensity of the Si 2p peak appearing at 99.9 eV, and the SiO2 peak intensity is the peak intensity appearing at 103.5 eV.

[0138]

[0139] And, the carbon-silicon composite described above can be used by manufacturing it in the following manner.

[0140]

[0141] [Carbon-silicon composite manufacturing method]

[0142] The carbon-silicon composite constituting the carbon-silicon / oxide composite of the present invention can be manufactured by performing a process including step 1-1 of preparing a porous carbon support; and step 1-2 of depositing silicon (Si) on the porous carbon support to form a silicon deposition layer.

[0143] The porous carbon support of step 1-1 above can be a commercially available one, and can be one having the manufacturing method and physical properties described above.

[0144] The above deposition in steps 1 and 2 can be performed at a deposition temperature of 300°C to 600°C and under an atmosphere supplying silane (SiH4) gas.

[0145] Additionally, the silane gas supply can be performed at 50 sccm to 500 sccm.

[0146] As a preferred embodiment, the deposition can be performed under the conditions of a temperature of 300°C to 600°C and a flow rate of 50 sccm to 500 sccm and an atmosphere in which silane (SiH4) gas is supplied by the above method. The deposition can be performed, for example, using chemical vapor deposition (CVD) and under atmospheric pressure conditions, but is not limited thereto. Through the deposition, silicon can be deposited on the surface of the porous carbon support according to the present invention and on the inside and / or outside of the pores.

[0147] Additionally, before the deposition in step 1-2, the porous carbon support prepared in step 1-1 may be subjected to a further pretreatment process, and then the deposition may be performed using this.

[0148] As a preferred example, a pretreatment process can be performed in which the porous carbon support of step 1-1 is immersed and stirred in an aqueous inorganic acid solution, followed by sequential steps of acidification, washing, and drying. By performing the pretreatment process, metal impurities contained in the porous carbon support can be removed.

[0149] The above-mentioned inorganic acid aqueous solution is an aqueous solution in which an inorganic acid is dissolved in water, and the inorganic acid may include at least one selected from hydrochloric acid, nitric acid, hydrofluoric acid, sulfuric acid, and phosphoric acid. In addition, the concentration of the inorganic acid in the inorganic acid aqueous solution may be 0.2 to 5.0 M, preferably 0.3 to 1.2 M, and more preferably 0.4 to 1.0 M.

[0150] And, the mixing ratio of the porous carbon support and the inorganic acid aqueous solution is appropriate to mix the powder and the inorganic acid aqueous solution at a weight ratio of about 1:8 to 12, preferably at a weight ratio of about 1:9 to 11.

[0151] In addition, it is appropriate to perform the acidification process by immersing and stirring the porous carbon support in an aqueous inorganic acid solution for 2 to 24 hours, preferably when the concentration of the inorganic acid is about 0.5 to 1.2 M, for 6 to 24 hours, more preferably for 12 to 24 hours.

[0152] Then, the porous carbon support is washed, and in a preferred embodiment, washing is performed at least once with distilled water at 60 to 80°C.

[0153] And, after washing is completed, after checking whether neutralization has occurred, if neutralization has occurred, drying can be performed using a general method used in the industry, such as natural drying or hot air drying, to obtain a purified, high-purity porous carbon support.

[0154] The porous carbon support purified by performing the above pretreatment process can be a high-purity powder with very low metal impurities.

[0155]

[0156] The carbon-silicon / oxide composite of the present invention described above can be applied as a battery negative electrode material, and the battery negative electrode material can have improved mechanical strength along with high electrical capacity and excellent cycle characteristics.

[0157] The method for manufacturing the above-mentioned battery negative electrode material is not particularly limited, and can be manufactured using a general method for manufacturing battery negative electrode materials. For example, the above-mentioned battery negative electrode material can be manufactured by mixing a carbon-silicon / oxide 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.

[0158] The present invention also relates to a battery comprising the aforementioned battery negative electrode material. The battery comprising the battery negative electrode material according to the present invention is a secondary battery, and may be a lithium-ion battery or an all-solid-state battery, but is not limited thereto.

[0159] 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.

[0160] The negative electrode of the lithium ion battery may include the above-described battery negative electrode material. The negative electrode may include a negative electrode current collector and a battery 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.

[0161] 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.

[0162] 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.

[0163] The above negative electrode may include a battery 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.

[0164] 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.

[0165]

[0166] 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.

[0167]

[0168] [Example]

[0169] Preparation Example 1: Preparation of a porous carbon support

[0170] 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.

[0171] After crushing the solid pitch pellets obtained above, 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.

[0172] The activated carbonized body, after the above activation, was pulverized using a pulverizer (NETZSCH, air jet mill) to produce a porous carbon support.

[0173] 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

[0174] 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 average particle size of the carbon supports was measured using a particle size analyzer (Horiba, Laser Particle Analyzer, LA-960V2) according to ASTM E112.

[0175] Example 1: Average particle size (㎛, D) 50 Diameter)6.0BET specific surface area (m) 2 / g)1105Tab density (g / ml)0.3Micropores of the entire porous carbon support (%)78.0Mesopores of the entire porous carbon support (%)20.0Ratio of the volume of mesopores in the surface layer to the volume of the entire mesopores in the deep and surface layers of the porous carbon support66%Macropores of the entire porous carbon support (%)2.0

[0176]

[0177] Example 1: Preparation of carbon-silicon / oxide composites

[0178] A carbon-silicon (C-Si) composite was manufactured using the porous carbon support of Preparation Example 1 manufactured above.

[0179] Specifically, 20 g of a porous carbon support was placed in a rotary kiln, and silane (SiH4) gas was injected to deposit the porous carbon support.

[0180] During silane gas coating, the pressure was at atmospheric pressure, and deposition was performed for 1 hour at a temperature of 475°C and a flow rate of 300 sccm to manufacture a carbon-silicon (C-Si) composite.

[0181] After 10 g of the previously manufactured carbon-silicon (C-Si) composite was placed in a rotary kiln, external air was supplied at a rotation speed of 5 rpm and a flow rate of 4,000 ml / min, and heat treatment was performed at a temperature of 500°C for 30 minutes to oxidize the surface of the silicon deposition layer of the carbon-silicon (C-Si) composite, thereby forming a silicon oxide layer (SiOx) on the surface of the silicon deposition layer, thereby manufacturing a carbon-silicon / oxide composite.

[0182]

[0183] Examples 2 to 7: Preparation of carbon-silicon / oxide composites

[0184] The same method as in Example 1 was used, but the surface of the silicon deposition layer of the carbon-silicon (C-Si) composite was oxidized under the conditions shown in Table 3 to form a silicon oxide layer (SiOx) on the surface of the silicon deposition layer, thereby manufacturing a carbon-silicon / oxide composite, respectively.

[0185]

[0186] Comparative Example 1

[0187] A carbon-silicon composite without a silicon oxide layer was manufactured using the same method as Example 1, but without performing heat treatment.

[0188] Classification Oxidation treatment temperature (℃) Oxidation treatment time (min) Air flow rate (ml / min) Example 1 500 30 4,000 Example 2 500 30 2,000 Example 3 500 60 1,000 Example 4 100 90 3,000 Example 5 500 30 160 Example 6 600 60 1,000 Example 7 500 120 3,000 Comparative example 1 No oxidation treatment (heat treatment)

[0189]

[0190] Experimental Example 1: Measurement of the physical properties of carbon-silicon / oxide composites

[0191] The Si content in the carbon-silicon / oxide composites manufactured in the examples and comparative examples was measured using XRF, and the results are shown in Table 4 below.

[0192] Additionally, after oxidation treatment of the carbon-silicon / oxide composite, the oxygen (O) content was analyzed by EDS, and the results are shown in Table 2 below.

[0193] And, the Si intensity ratio in the silicon oxide layer is a value measured and calculated based on the following equation 1 by measuring XPS (X-ray Photoelectron Spectroscope).

[0194] [Formula 1]

[0195] Si intensity ratio = Si peak intensity / (Si peak intensity + SiO2 peak intensity) * 100%

[0196] In Equation 1, the Si peak intensity is the intensity of the Si 2p peak appearing at 99.9 eV, and the SiO2 peak intensity is the peak intensity appearing at 103.5 eV.

[0197] Additionally, the oxygen content increase rate was measured according to Equation 2 below.

[0198] [Formula 2]

[0199] Oxygen content increase rate (%) = {(BA) / A} * 100(%)

[0200] In Equation 2, A and B are the oxygen contents (%) measured by SEM (scanning electron microscope) and EDS (energy dispersive spectroscopy), A is the oxygen content (%) on the surface of the carbon-silicon composite (Comparative Example 1) on which no silicon oxide layer is formed, and B is the oxygen content (%) on the surface of the manufactured carbon-silicon / oxide composite (Example 1).

[0201] Additionally, the specific surface area (BET), particle size, and tap density of the carbon-silicon / oxide composite were measured, and the results are shown in Table 4 below.

[0202] Carbon-silicon / oxide composite properties Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Comparative Example 1 Si content (wt%) in carbon-silicon / oxide composite 5757555655675555 O content (wt%) in carbon-silicon / oxide composite 16.3 14.4 20.7 15.19.1 31.2 7.3 4.9 Si intensity ratio in silicon oxide layer (%) 4553284763117176 Oxygen content increase rate on the surface of carbon-silicon / oxide composite (%) 23319432320886537490 BET specific surface area (m 2 / g)157183186121863728585Average particle size (㎛)6.66.76.77.07.05.47.17.1Tap density (g / ml)0.610.590.600.610.610.500.610.61

[0203] As shown in Table 4, in the cases of Examples 1 to 4, the Si intensity ratio in the silicon oxide layer is approximately 25 to 60%, and the oxygen content increase rate on the surface of the silicon-carbon composite satisfies 100 to 400%.

[0204] In contrast, in Example 6, where heat treatment was performed at 600°C, which is higher than 550°C, carbon on the surface was decomposed, which tended to significantly increase the O content, significantly reduced the Si strength ratio, and an excessive amount of silicon oxide layer existed on the surface.

[0205] In addition, in the case of Comparative Example 1, Example 4, and Example 7 in which heat treatment was performed at 50°C, which is less than 90°C, the rate of increase in oxygen content was small compared to Example 1 (500°C) and Example 4 (100°C), and as a result, the Si strength ratio in the silicon oxide layer was high.

[0206] In addition, in Comparative Example 1, although the oxygen content increase rate was 0%, since the amorphous state of Si is highly reactive, oxidation can occur when the surface comes into contact with air even at room temperature, and a portion of the surface can be formed. However, oxidation occurring through surface contact was limited.

[0207]

[0208] Experimental Example 1: Electrochemical Evaluation of Secondary Batteries

[0209] Half coin cells were manufactured using each of the carbon-silicon / oxide composites of the previously manufactured examples and comparative examples.

[0210] A slurry was prepared by mixing carbon-silicon / oxide composite:conductive material: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.

[0211] 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.

[0212] 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 5 below.

[0213] 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) as additives (see Table 5).

[0214] Composition (AM:CM:BM) 8:1:1 Area capacity (mAh / cm 2 )1 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

[0215] In Table 5 above, AM, CM, and BM represent the active material (carbon-silicon composite), conductor (Super P carbon black), and binder (styrene-butadiene rubber / carboxymethyl cellulose 5:5), respectively, and EC, EMC, DMC, FEC, VC, and PS represent ethylene carbonate, ethyl methyl carbonate, dimethyl carbonate, fluoroethylene carbonate, vinylene carbonate, and propane sultone, respectively.

[0216] Electrochemical analysis was performed on the manufactured half coin cell under the following conditions, and the results are shown in Table 6 below.

[0217] Cut off voltage (V): 0.005 - 1.5V (Formation), 0.005 - 1.2V(Cycle)

[0218] Formation C-rate (C): 0.1C lithiation, 0.1C delithiation

[0219] Cycle C-rate (C): 0.5C lithiation, 0.5C delithiation

[0220]

[0221] In addition, the capacity retention rate was evaluated by calculating the discharge capacity after 50 cycles as a percentage of the discharge capacity after the first cycle, and the results are shown in Table 6 below.

[0222] Classification Initial Capacity Retention Rate (%, 50 Cycles) Half Coin Cell Carbon-Silicon / Oxide Composite Charge Capacity (mAh / g) Discharge Capacity (mAh / g) ICE (%) Manufacturing Example 1 Example 11,8191,43678.937 Manufacturing Example 2 Example 21,9621,56179.644 Manufacturing Example 3 Example 31,8301,35173.859 Manufacturing Example 4 Example 41,9101,50178.645 Manufacturing Example 5 Example 51,9511,68286.223 Manufacturing Example 6 Example 61,3021,01678.027 Manufacturing Example 7 Example 71,9221,68287.533 Comparative Manufacturing Example 1 Comparative Example 11,9711,72987.732

[0223] Referring to Table 6 above, it was confirmed that the half coin cells of Manufacturing Examples 1 to 4, which introduced the carbon-silicon / oxide composites of Examples 1 to 4 as anode materials, had relatively low ICE but relatively greatly improved capacity retention rates compared to Comparative Manufacturing Example 1 and Manufacturing Example 5. Specifically, compared to Comparative Manufacturing Example 1 (Comparative Example 1) without a silicon oxide layer, the half coin cells of Manufacturing Examples 1 to 4 (Examples 1 to 4) had improved capacity retention rates by a minimum of 15.6% and a maximum of 84.3%.

[0224] In addition, Manufacturing Example 6, which introduced the carbon-silicon / oxide composite of Example 6 as a negative electrode material, had a problem of a significantly reduced capacity retention rate when compared with Manufacturing Example 1, and when Manufacturing Example 7, which introduced the carbon-silicon / oxide composite of Example 7 as a negative electrode material, was compared with Manufacturing Example 4.

[0225]

[0226] It is believed that this is because the silicon-carbon composite, which is the negative electrode material, forms a silicon oxide layer with an appropriate thickness, thereby suppressing volume expansion due to insertion of lithium ions into the composite, minimizing side reactions with electrolyte components due to silicon outflow, and thereby suppressing or preventing the formation of a side reaction layer, resulting in a high capacity retention rate (high long-term stability).

[0227]

[0228] 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. A carbon-silicon composite comprising a porous carbon support including a surface portion and a deep portion, and a silicon deposition layer formed on the porous carbon support; and A carbon-silicon / oxide composite, comprising a silicon oxide layer formed on the carbon-silicon composite.

2. In the first paragraph, the silicon deposition layer is a carbon-silicon / oxide composite having a Si intensity ratio of 25 to 60% according to the following equation 1 when measured by XPS (X-ray Photoelectron Spectroscope): [Formula 1] Si intensity ratio = Si peak intensity / (Si peak intensity + SiO2 peak intensity) * 100% In Equation 1, the Si peak intensity is the intensity of the Si 2p peak appearing at 99.6 to 99.9 eV, and the SiO2 peak intensity is the peak intensity appearing at 103.5 to 103.7 eV.

3. A carbon-silicon / oxide composite in the first paragraph, wherein the silicon oxide layer is formed by oxidizing the surface of a silicon deposition layer.

4. In the first paragraph, the carbon-silicon / oxide composite, The oxygen (O) content measured by SEM (scanning electron microscope) and EDS (energy dispersive spectroscopy) is 10 to 30 wt%, A carbon-silicon / oxide composite having a silicon (Si) content of 20 to 60 wt% as measured by X-ray fluororescene spectroscopy (XRF).

5. In the first paragraph, the porous carbon support is a carbon-silicon / oxide composite comprising mesopores having a diameter of 2 to 50 nm.

6. A carbon-silicon / oxide composite in which the ratio of the volume of the mesopores of the surface layer to the volume of the entire mesopores of the porous carbon support in the fifth paragraph is 50 to 76%.

7. In the fifth paragraph, the porous carbon support is a carbon-silicon / oxide composite in which the ratio of the volume of mesopores to the volume of the total pores is 10% or more.

8. In the first paragraph, the porous carbon support is a carbon-silicon / oxide composite having a surface porosity greater than a deep porosity.

9. In paragraph 1, The BET surface area of ​​the above carbon-silicon / oxide composite is 200 m 2 A carbon-silicon / oxide composite having a particle size of 5 to 15 μm and a tap density of 0.50 to 0.80 g / ml.

10. Step 1 of preparing a carbon-silicon composite, comprising a porous carbon support including a surface portion and a deep portion and a silicon deposition layer formed on the porous carbon support; and A method for manufacturing a carbon-silicon / oxide composite, comprising the second step of forming a silicon oxide layer on the surface of a silicon deposition layer by oxidizing the carbon-silicon composite.

11. A method for producing a carbon-silicon / oxide composite, wherein the oxidation treatment in the 10th paragraph is performed by heat treatment at 90 to 550°C in an air or oxygen atmosphere.

12. A method for producing a carbon-silicon / oxide composite, wherein the heat treatment in the 11th paragraph is performed in a rotary kiln while injecting air or oxygen at a rotation speed of 1 to 10 rpm and a flow rate of 500 to 4,500 ml / min.

13. A method for producing a carbon-silicon / oxide composite in accordance with paragraph 10, wherein the carbon-silicon / oxide composite has an oxygen content increase rate of 100 to 400% according to the following formula 2. [Formula 2] Oxygen content increase rate (%) = {(BA) / A} * 100(%) In Equation 2, A and B are the oxygen contents (%) measured by SEM (scanning electron microscope) and EDS (energy dispersive spectroscopy), A is the oxygen content (%) on the surface of the carbon-silicon composite of step 1, and B is the oxygen content (%) on the surface of the carbon-silicon / oxide composite manufactured by performing step 2.

14. A silicon anode material comprising a carbon-silicon / oxide composite according to any one of claims 1 to 9.

15. A lithium ion battery comprising the silicon negative electrode material of Article 14.

16. An all-solid-state battery comprising the silicon negative electrode material of Article 14.