Coating composition for coating surface of secondary battery electrode active material, and secondary battery electrode material comprising same

Abstract

The present invention relates to a coating composition for coating the surface of a secondary battery electrode active material, and a secondary battery electrode material comprising same, the composition comprising petroleum pitch having a softening point of 200-270° C.

Description

Coating composition for surface coating of secondary battery electrode active material and secondary battery electrode material comprising the same

[0001] The present invention relates to a coating composition for surface coating of a secondary battery electrode active material including petroleum pitch having a softening point of 200 to 270°C and a secondary battery electrode material including the same.

[0002]

[0003] Due to the rapid increase in fossil fuel use, the demand for alternative or clean energy is increasing, and as part of this, the most actively researched field is power generation and storage using electrochemical reactions.

[0004] Secondary batteries are a prime example of electrochemical devices that utilize this electrochemical energy, and their applications are expanding. With the recent technological development and increasing demand for portable devices such as laptops, mobile phones, and cameras, the demand for secondary batteries as an energy source has rapidly increased. Among these secondary batteries, lithium secondary batteries, which boast high energy density and high capacity, have been extensively studied and are now commercialized and widely used.

[0005] In general, secondary batteries are composed of a positive electrode, a negative electrode, an electrolyte, and a separator. The positive electrode material of a lithium secondary battery includes a metal oxide such as LiCoO2, Li(NiCoMn)O2, Li(NiCoAl)O2, LiFePO4, LiMnO2, LiMn2O4, or LiCrO2, and the negative electrode material includes a metal lithium, a carbon-based material such as graphite or activated carbon, or a material such as silicon oxide (SiOx). Among the above negative electrode materials, metal lithium was mainly used in the early days, but as the charge and discharge cycle progresses, lithium atoms grow on the surface of the metal lithium, damaging the separator and destroying the battery. Therefore, carbon-based materials are mainly used recently. However, carbon-based materials have a disadvantage of low capacity, with a theoretical capacity of only about 400 mAh / g, and various studies are being conducted to replace the carbon-based materials using high-capacity materials such as silicon (Si), which has a high theoretical capacity (4,200 mAh / g) as a negative electrode material.

[0006] Meanwhile, when using negative electrode materials such as silicon, a technology is being applied to coat the surface of the negative electrode with pitch, which acts as a conductive material and binder, to prevent volume changes. However, the performance of secondary batteries remains inconsistent depending on the pitch used.

[0007]

[0008] The present invention has been devised to overcome the above-described problems, and provides a coating composition for surface coating of a secondary battery electrode active material and a secondary battery electrode material including the same, which can significantly improve the performance, particularly the lifespan characteristics, of a secondary battery to which the coating composition is applied by forming a coating layer including petroleum pitch having a softening point of 200 to 270°C on the surface of an electrode active material, thereby securing the crystal structure and / or coating uniformity of the coating layer.

[0009]

[0010] In order to solve the above-described problem, the coating composition for surface coating of the secondary battery electrode active material of the present invention may include petroleum pitch having a softening point of 200 to 270°C and a volatile component that volatilizes at a temperature of 300°C or lower.

[0011] As a preferred embodiment of the present invention, the petroleum pitch may include isotropic petroleum pitch and anisotropic petroleum pitch.

[0012] As a preferred embodiment of the present invention, the coating composition for surface coating of the secondary battery electrode active material of the present invention may contain 10.0 wt% or less of volatile matter that volatilizes at a temperature of 300°C or less based on the total wt%.

[0013] As a preferred embodiment of the present invention, the coating composition for surface coating of the secondary battery electrode active material of the present invention may include 80 to 99 wt% of isotropic petroleum pitch and 1 to 20 wt% of anisotropic petroleum pitch based on the total weight%.

[0014] As a preferred embodiment of the present invention, the secondary battery may be a lead (Pd) battery, a nickel-cadmium (NiCd) battery, a nickel-metal (Ni-Metal) hydrogen battery, a lithium ion (Li-ion) battery, or a lithium ion polymer (Li-ion polymer) battery.

[0015] As a preferred embodiment of the present invention, the electrode active material may be a negative electrode active material.

[0016] As a preferred embodiment of the present invention, the negative active material may include silicon (Si).

[0017] Meanwhile, the secondary battery electrode material of the present invention may include an electrode active material including silicon and a coating layer coated on the surface of the electrode active material.

[0018] As a preferred embodiment of the present invention, the coating layer may be formed by carbonizing the coating composition for surface coating of the secondary battery electrode active material of the present invention.

[0019] As a preferred embodiment of the present invention, the secondary battery electrode material of the present invention may include a coating layer in an amount of 2.1 to 10.0 wt% based on the total wt%.

[0020] As a preferred embodiment of the present invention, the coating layer may include carbonized petroleum pitch.

[0021] As a preferred embodiment of the present invention, the petroleum pitch may include isotropic petroleum pitch and anisotropic petroleum pitch.

[0022] As a preferred embodiment of the present invention, the carbonized petroleum pitch may be carbonized at a temperature of 600 to 800°C for 30 to 120 minutes.

[0023] As a preferred embodiment of the present invention, the electrode active material may include a nonporous carbon support including at least one of hard carbon and soft carbon.

[0024] As a preferred embodiment of the present invention, the electrode active material may include a porous carbon support, and silicon may be disposed on the surface and inside the pores of the porous carbon support.

[0025] As a preferred embodiment of the present invention, the secondary battery electrode material of the present invention may contain 30.0 to 80.0 wt% of silicon.

[0026]

[0027] The coating composition for surface coating of a secondary battery electrode active material of the present invention and the secondary battery electrode material including the same form a coating layer including petroleum pitch having a softening point of 200 to 270°C on the surface of the electrode active material, thereby securing the crystal structure and / or coating uniformity of the coating layer, thereby significantly improving the performance, particularly the life characteristics, of a secondary battery to which the same is applied.

[0028]

[0029] Hereinafter, the present invention will be described in more detail.

[0030] To prevent volume changes when using existing anode materials like silicon, a technology has been applied to coat the surface of the anode with pitch, which acts as a conductive material and binder. However, the performance of secondary batteries has been inconsistent depending on the pitch used.

[0031] Accordingly, the present invention forms a coating layer including petroleum pitch having a softening point of 200 to 270°C on the surface of an electrode active material, thereby securing the crystal structure and coating uniformity of the coating layer, thereby significantly improving the performance, particularly the life characteristics, of a secondary battery to which it is applied.

[0032]

[0033] The coating composition for surface coating of the secondary battery electrode active material of the present invention may include pitch and a volatile substance.

[0034] Pitch is a solid organic material at room temperature, or a residue from the thermal decomposition of tar distillation. It consists of a complex mixture of numerous aromatic hydrocarbons and heterocyclic compounds. Pitch does not have a constant melting point, but rather a wide softening range, with a softening temperature ranging from approximately 320 K to 570 K, depending on molecular weight and composition.

[0035] The pitch of the present invention may include at least one selected from petroleum pitch, coal tar pitch, and mesogenic pitch, and preferably may include petroleum pitch.

[0036] Specifically, the pitch of the present invention may include petroleum pitch, and preferably includes petroleum pitch having a softening point of 200 to 270°C, more preferably 220 to 270°C, even more preferably 240 to 260°C, and even more preferably 250 to 260°C. If the softening point is less than 200°C, not only is it difficult to manufacture pitch for use in a dry coating process (Mechano-fusion), but there may also be a problem that the pitch may stick together at a low temperature during the carbonization process or melt due to frictional heat caused by the rpm of the inner wall, and if it exceeds 270°C, there may be a problem with the uniformity of the pitch coating.

[0037] Additionally, the petroleum pitch may include isotropic petroleum pitch and anisotropic petroleum pitch.

[0038] Specifically, the coating composition for surface coating of the secondary battery electrode active material of the present invention may contain 80 to 99 wt%, preferably 82 to 97 wt%, more preferably 84 to 97 wt%, even more preferably 88 to 97 wt%, and even more preferably 92 to 97 wt% of isotropic petroleum pitch based on the total wt%. If the isotropic petroleum pitch is contained in an amount less than 80 wt%, there may be a problem of formation of an uneven coating layer, and if it is contained in an amount exceeding 99 wt%, there may be a problem of reduced electrical conductivity.

[0039] In addition, the coating composition for surface coating of the secondary battery electrode active material of the present invention may contain 1 to 20 wt% of anisotropic petroleum pitch, preferably 1.2 to 15 wt%, more preferably 1.5 to 10 wt%, even more preferably 2.0 to 7.0 wt%, and even more preferably 2.0 to 4.0 wt%, based on the total weight%. If the anisotropic petroleum pitch is contained in an amount of less than 1 wt%, there may be a problem of reduced electrical conductivity, and if it is contained in an amount exceeding 20 wt%, there may be a problem of formation of an uneven coating layer.

[0040] Additionally, the volatile matter may include components that evaporate at a temperature of 300°C or lower as volatile substances.

[0041] Specifically, the coating composition for surface coating of the secondary battery electrode active material of the present invention may contain 10.0 wt% or less, preferably 0.1 to 10 wt%, more preferably 0.3 to 8.0 wt%, even more preferably 0.5 to 5.0 wt%, and even more preferably 0.5 to 2.0 wt%, of volatile matter that volatilizes at a temperature of 300°C or lower, based on the total weight%. If the volatile matter is contained in an amount exceeding 10 wt%, there may be a problem of formation of an uneven coating layer.

[0042] Meanwhile, the coating composition for surface coating of the secondary battery electrode active material of the present invention may have a value calculated by the following relational expression 1 of 0.8 or less, preferably 0.3 to 0.8, more preferably 0.3 to 0.75, more preferably 0.35 to 0.7, and even more preferably 0.4 to 0.6. If the value calculated by the following relational expression 1 exceeds 0.8, the degree of polymerization of the pitch included in the coating composition for surface coating of the secondary battery electrode active material of the present invention may be lowered, and there may be a problem of not satisfying the softening point targeted by the present invention.

[0043] [Relationship 1]

[0044] S / S P X 100 + MP

[0045] In the above relational expression 1, S represents the mass ratio of saturated hydrocarbons included in the coating composition for surface coating of a secondary battery electrode active material derived from the SARA (saturatesaromatics-resins-asphaltenes) analysis result, and S P represents the softening point of the coating composition for surface coating of a secondary battery electrode active material, and MP represents the volume ratio of the content of anisotropic petroleum pitch included in the coating composition for surface coating of a secondary battery electrode active material.

[0046] In addition, the secondary battery of the invention may be a lead (Pd) battery, a nickel-cadmium (NiCd) battery, a nickel-metal (Ni-metal) hydrogen battery, a lithium ion (Li-ion) battery, a solid-state battery, a soft carbon battery, a hard carbon battery, or a lithium ion polymer (Li-ion) battery, and preferably a lithium ion (Li-ion) battery.

[0047] Additionally, the electrode active material of the present invention may be a negative electrode active material, and the negative electrode active material may include silicon (Si).

[0048]

[0049] Furthermore, the secondary battery electrode material of the present invention may include an electrode active material including silicon and a coating layer coated on the surface of the electrode active material.

[0050] At this time, the electrode active material may include a porous carbon support containing silicon (Si), and the silicon may be disposed on the surface and inside the pores of the porous carbon support. Specifically, the porous carbon support containing silicon (Si) means that silicon is formed on the surface of an activated carbon porous carbon support, and the surface of the porous carbon support includes not only the surface exposed to the outside but also the surface located inside. Specifically, the porous carbon support is a porous material having pores on the outer surface and / or the inner surface, and as an example, when coating the surface of the porous carbon support using silicon, the silicon penetrates and coats not only the outer surface of the porous carbon support but also the inner surface of the porous carbon support through the pores, thereby partially or completely blocking the pores of the porous carbon support, and may be coated with a certain thickness on the outer surface of the porous carbon support.

[0051] In addition, when the electrode active material is a porous carbon support containing silicon (Si), the coating layer is formed on the surface of the porous carbon support containing silicon (Si), and the surface of the porous carbon powder containing silicon (Si) includes not only the surface exposed to the outside but also the surface located inside. Specifically, the porous carbon support containing silicon (Si) is a porous material having pores on the outer surface and / or the inner surface. As an example, when forming a coating layer using petroleum pitch, the petroleum pitch penetrates and coats not only the outer surface of the porous carbon support containing silicon (Si) but also the inner surface of the porous carbon support containing silicon (Si) through the pores, thereby not only blocking some or all of the pores of the porous carbon support containing silicon (Si), but also coating the outer surface of the porous carbon support containing silicon (Si) with a certain thickness to form a coating layer.

[0052] Additionally, the electrode active material may include a nonporous carbon support including at least one of hard carbon and soft carbon.

[0053] Additionally, the electrode active material may most preferably be a carbon-silicon composite.

[0054] A carbon-silicon composite comprises a carbon support including a surface portion and a core portion, and silicon (Si) disposed including a surface of the carbon support.

[0055] In this specification, the core of the carbon support may mean an area within a distance of 1 / 2 of the radius of the support from the center of the support, and the surface may mean the remaining area of ​​the support excluding the core.

[0056] The porous carbon support may be any carbon support commonly used in the art without limitation, but preferably, at least one of a non-porous carbon support and a porous carbon support may be used, more preferably, at least one of graphite, hard carbon, soft carbon, and porous carbon support may be used, and even more preferably, using at least one of hard carbon, soft carbon, and porous carbon support may be more advantageous in achieving the purpose of the present invention.

[0057] 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.

[0058] 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.

[0059] 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.

[0060] 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.

[0061] 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.

[0062] 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.

[0063] 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.

[0064] 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.

[0065] 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.

[0066] 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.

[0067] 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.

[0068] 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.

[0069] 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%.

[0070] 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.

[0071] 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.

[0072] 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.

[0073] 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.

[0074] 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.

[0075] 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).

[0076] 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.

[0077] 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.

[0078] 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.

[0079] 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.

[0080] 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.

[0081] 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.

[0082] 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.

[0083] 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.

[0084] 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.

[0085] 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.

[0086] 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.

[0087] 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.

[0088] 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.

[0089] 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.

[0090] 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.

[0091] In a specific example of the present invention, the activation of the carbonized body can be performed under conditions of a flow rate of an oxidizing gas, preferably water vapor, of 0.1 to 100 ml / min, preferably 0.1 to 50 ml / min. When the activation of the carbonized body is performed under these oxidizing gas flow rates, a porous carbon support in which micropores and mesopores are sufficiently formed can be obtained.

[0092] 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.

[0093] 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.

[0094] 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.

[0095] 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.

[0096] 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.

[0097] 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.

[0098] In one example of the present invention, the porous carbon support of the carbon-silicon composite according to the present invention may have a ratio of the volume of mesopores to the total pore volume of 0.1 or more. The pores of the porous carbon support can be classified into micropores with a diameter of less than 2 nm, mesopores with a diameter of 2 nm to 50 nm, and macropores with a diameter of more than 50 nm, depending on their size. Such porous supports have been studied in the direction of increasing the ratio of micropores to increase the specific surface area or increasing the ratio of macropores to increase the amount of material supported inside the pores. However, when there are many micropores, there is a problem that silicon (Si) is difficult to deposit inside the pores, resulting in a decrease in electrical capacity. In addition, when there are many macropores, silicon agglomeration occurs, which can generate stress during repeated charge / discharge processes, which can mechanically damage the negative electrode material.

[0099] 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.

[0100] 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.

[0101] 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.

[0102] 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.

[0103] 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 200 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 N2 / 77K Isotherm adsorption results can be calculated using the BET equation and the BJH equation according to ISO9277. The BET specific surface area of ​​the porous carbon support may be 200 ㎡ / 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.

[0104] The diameter of the above porous carbon support may be 20 μm or less. The diameter is D 50It may refer to the diameter, and may be a value measured using MICROTRAC S3500 equipment. Specifically, it may refer to an average value obtained by dispersing a porous carbon support in ethanol and then performing particle size analysis three times. The diameter of the porous carbon support may be 20 ㎛ or less, 18 ㎛ or less, 16 ㎛ or less, 14 ㎛ or less, 12 ㎛ or less, or 10 ㎛ or less, and may be 1 ㎛ or more, 2 ㎛ or more, 3 ㎛ or more, 4 ㎛ or more, or 4.5 ㎛ or more, but is not limited thereto. If the diameter of the porous carbon support is too small, when performing coating, silicon may be quickly filled inside and then additional coating may be performed on the surface, so that the surface coating layer may be formed thickly. In this case, deterioration may be accelerated during charge and discharge, and agglomeration of materials with small particle sizes may occur when manufacturing an electrode, and deterioration of the agglomerated portion may be significant. In addition, if the diameter of the porous carbon support is too large, it may be difficult for silane gas to diffuse into the interior of the porous carbon support, making it difficult to form a uniform silicon coating layer inside the support. In addition, if the diameter of the porous carbon support is too large, it may be difficult to uniformly coat the slurry on the current collector during electrode manufacturing, which may result in a decrease in capacity uniformity.

[0105] 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. 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. 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 damage to the negative electrode material by generating stress due to volume expansion during repeated charge and discharge processes.

[0106] 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.

[0107] 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.

[0108] 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.

[0109] 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.

[0110] 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.

[0111] 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.

[0112] 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.

[0113] 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.

[0114] 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.

[0115] 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.

[0116] 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.

[0117] 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.

[0118] 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.

[0119] 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.

[0120]

[0121] The coating layer of the present invention may be formed by carbonizing a coating composition for surface coating of the secondary battery electrode active material of the present invention.

[0122] Additionally, the coating layer of the present invention may include carbonized petroleum pitch. Specifically, the coating layer may include isotropic petroleum pitch and anisotropic petroleum pitch.

[0123] More specifically, the coating layer can be formed by coating the coating composition for surface coating of the secondary battery electrode active material of the present invention on the surface of the electrode active material including silicon and then carbonizing it.

[0124] Meanwhile, the carbonized petroleum pitch may be carbonized at a temperature of 600 to 800°C, preferably 600 to 750°C, and more preferably 650 to 750°C for 30 to 120 minutes, and preferably 30 to 60 minutes. At this time, if the carbonization temperature is less than 600°C, the carbon crystal structure of the pitch is not developed, so the conductivity of the material is low, which may cause a problem of reduced battery performance, and if it exceeds 800°C, the silicon is crystallized, which may cause a problem of reduced conductivity and a reduction in battery capacity. In addition, if the carbonization time is less than 30 minutes, the carbonized crystal quality is low, which may cause a reduction in conductivity, and if it exceeds 120 minutes, the silicon is crystallized due to excessive heat treatment, which may cause a problem of reduced conductivity and a reduction in battery capacity.

[0125]

[0126] Furthermore, the secondary battery electrode material of the present invention may contain silicon in an amount of 30.0 to 80.0 wt%, preferably 30.0 to 60.0 wt%, more preferably 30.0 to 41.0 wt%, still more preferably 33.0 to 40.0 wt%, still more preferably 35.0 to 40.0 wt%, and still more preferably 37.0 to 39.0 wt%, based on the total weight%.

[0127] In addition, the secondary battery electrode material of the present invention may include a coating layer in an amount of 2.1 to 10.0 wt%, preferably 2.1 to 6.0 wt%, more preferably 2.5 to 5.0 wt%, and even more preferably 3.5 to 5.0 wt%, based on the total weight%. If the coating layer is included in an amount of less than 2.1 wt%, there may be a problem of forming an uneven coating layer, and if it is included in an amount of more than 10.0 wt%, there may be a problem of reduced capacity due to formation of an excessive coating layer.

[0128] In addition, the secondary battery electrode material of the present invention has a thickness of 70 m 2 / g or less, preferably 10 to 70 m 2 / g, more preferably 20 to 60 m 2 / g, more preferably 30 to 50 m 2 / g of surface area, and if the specific surface area is 70 m 2 Exceeding / g may cause problems with reduced lifespan.

[0129] In addition, the secondary battery electrode material of the present invention has a thickness of 0.12 cm 3 / g or less, preferably 0.01 to 0.12 cm 3 / g, more preferably 0.02 to 0.1 cm 3 / g, more preferably 0.03 to 0.08 cm 3 / g of pore volume, and if the pore volume is 0.12 cm 3 Exceeding / g may cause problems with reduced lifespan.

[0130] In addition, the secondary battery electrode material of the present invention has a D of 20 ㎛ or less, preferably 2 to 15 ㎛, more preferably 3 to 10 ㎛, and even more preferably 4 to 8 ㎛. 50 It can have a diameter, if D 50 If the diameter exceeds 20 ㎛, there may be a problem in manufacturing the electrode due to the large particles in the active material making uniform coating impossible during electrode manufacturing.

[0131] In addition, the secondary battery electrode material of the present invention has a density of 0.1 to 10 g / cm 3 , preferably 0.2 to 5 g / cm 3 , more preferably 0.3 to 1 g / cm 3 , more preferably 0.4 to 0.8 g / cm 3 It can have a tap density of 0.1 g / cm. 3 If it is less than 10 g / cm, the electrode active material will be used in excess, which may cause the thickness of the electrode material to become thicker. 3 If it exceeds , there may be a problem of uneven coating.

[0132]

[0133] Meanwhile, the method for manufacturing a secondary battery electrode material of the present invention includes a first step and a second step.

[0134] First, in the first step of the method for manufacturing a secondary battery electrode material of the present invention, a coating composition for surface coating of a secondary battery electrode active material of the present invention is coated on the surface of the electrode active material, thereby forming a coating layer on the surface of the electrode active material. At this time, the electrode active material and / or the coating composition for surface coating of the secondary battery electrode active material of the present invention are as described above.

[0135] Additionally, the coating can be performed by dry coating using the mechano-fusion method.

[0136] Next, in the second step of the method for manufacturing a secondary battery electrode material of the present invention, a secondary battery electrode material can be manufactured by carbonizing an electrode active material having a coating layer formed on the surface.

[0137] At this time, carbonization can be performed at a temperature of 600 to 800°C, preferably 600 to 750°C, more preferably 650 to 750°C, for 30 to 120 minutes, preferably 30 to 60 minutes.

[0138]

[0139] 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.

[0140]

[0141] Preparation Example 1: Preparation of a coating composition for surface coating of a secondary battery electrode active material

[0142] (1) 300 g of petroleum residual oil (YNCC, HTC PFO (pyrolysis fuel oil)) was placed in a reactor equipped with a stirrer, and nitrogen was supplied at a flow rate of 100 ml / min to produce petroleum pitch through thermal decomposition and polycondensation. At this time, the stirrer was rotated at a speed of 200 rpm, and thermal decomposition and polycondensation were performed at a temperature of 400°C for 3 hours.

[0143] (2) The manufactured petroleum pitch was solidified and pelletized to manufacture solid petroleum pitch pellets having an average particle size of 1 to 30 mm.

[0144] (3) After crushing the manufactured solid petroleum pitch pellets, the crushed powder was fed into a rotary kiln with three zones to sequentially perform stabilization, carbonization, and activation. At this time, the carbonization yield of the stabilized powder was measured to be 63.2 wt%, and the carbonization yield was measured using a TGA (Thermogravimetric analysis) device after the temperature was increased to 900°C at a rate of 5°C / min.

[0145] (4) The activated powder was put back into a grinder (Netsch, air jet mill) and re-grind to manufacture a coating composition for surface coating of a secondary battery electrode active material.

[0146]

[0147] Preparation Example 2: Preparation of a coating composition for surface coating of a secondary battery electrode active material

[0148] A coating composition for surface coating of a secondary battery electrode active material was prepared using the same method as in Preparation Example 1. However, unlike Preparation Example 1, thermal decomposition and condensation polymerization were performed at a temperature of 350°C for 3 hours, thereby finally preparing a coating composition for surface coating of a secondary battery electrode active material.

[0149]

[0150] Preparation Example 3: Preparation of a coating composition for surface coating of a secondary battery electrode active material

[0151] A coating composition for surface coating of a secondary battery electrode active material was prepared using the same method as Preparation Example 1. However, unlike Preparation Example 1, thermal decomposition and condensation polymerization were performed at a temperature of 450°C for 3 hours, thereby finally preparing a coating composition for surface coating of a secondary battery electrode active material.

[0152]

[0153] Comparative Preparation Example 1: Preparation of a Coating Composition for Surface Coating of a Secondary Battery Electrode Active Material

[0154] A coating composition for surface coating of a secondary battery electrode active material was prepared using the same method as in Preparation Example 1. However, unlike Preparation Example 1, thermal decomposition and condensation polymerization were performed at a temperature of 300°C for 3 hours, thereby finally preparing a coating composition for surface coating of a secondary battery electrode active material.

[0155]

[0156] Comparative Preparation Example 2: Preparation of a Coating Composition for Surface Coating of a Secondary Battery Electrode Active Material

[0157] A coating composition for surface coating of a secondary battery electrode active material was prepared using the same method as in Preparation Example 1. However, unlike Preparation Example 1, thermal decomposition and condensation polymerization were performed at a temperature of 500°C for 3 hours, thereby finally preparing a coating composition for surface coating of a secondary battery electrode active material.

[0158]

[0159] Experimental Example 1: SARA Analysis

[0160] SARA (saturates-aromatics-resins-asphaltenes) analysis was performed on each of the coating compositions (=samples) for surface coating of secondary battery electrode active materials manufactured in Preparation Examples 1 to 3 and Comparative Preparation Examples 1 to 2. Specifically, Chromarod S-5 was loaded onto a chroma-rod holder, and a sample (10 to 15 mg / ㎖) dissolved in dichloromethane was spotted. Referring to the spot guide, 1 ㎕ was dropped in 7 to 8 portions using a micropipette. After drying the chroma-rod holder, it was placed in a tank filled with a developing solvent and developed. At this time, the developing solvents used were hexane, toluene, and methanol / dichloromethane (5:95) in that order. The dried chroma-rod holder was mounted on the IATROSCAN MK-6 and a scan was performed for 30 seconds, and at the same time, the Clarity program on the connected PC was run and then analysis was performed.

[0161]

[0162] Experimental Example 2: Anisotropy Measurement

[0163] High-temperature centrifugation was performed on each of the coating compositions for surface coating of secondary battery electrode active materials manufactured in Preparation Examples 1 to 3 and Comparative Preparation Examples 1 to 2. 0.6 g of the crushed coating compositions for surface coating of secondary battery electrode active materials manufactured in Preparation Examples 1 to 3 and Comparative Preparation Examples 1 to 2 were each placed in a glass tube having an inner diameter of 6 mm, an outer diameter of 8 mm, and a height of 90 to 100 mm, and two or four tubes were balanced and placed inside a high-temperature centrifuge. The heater temperature of the high-temperature centrifuge was set to 410°C, and the temperature was increased at a rate of 15°C per minute. When the heater reached the target temperature and about 30 minutes later, when the internal actual temperature reached 350 to 360°C, centrifugation was performed at 1,787 to 3,096 rpm (500 to 1,500 g) for 15 to 30 minutes. A tube containing a coating composition for surface coating of a centrifuged secondary battery electrode active material was cut to a length of 23–28 mm from the bottom, cured with epoxy resin, and then polished using a Tegramin-25 polisher. The polished cross-section was photographed under a polarizing microscope, and the anisotropic / isotropic areas were manually designated using the ImageJ program, and the ratio of the anisotropic area to the total area was calculated.

[0164]

[0165] Experimental Example 3: Measurement of the physical properties of a coating composition for surface coating of a secondary battery electrode active material.

[0166] Using a portion of the experimental data measured in Experimental Examples 1 and 2, the softening point, components and contents thereof of each coating composition for surface coating of secondary battery electrode active materials manufactured in Preparation Examples 1 to 3 and Comparative Preparation Examples 1 to 2 were measured and shown in Table 1 below. The values ​​calculated by the following Relational Expression 1 are also shown in Table 1 below.

[0167] [Relationship 1]

[0168] S / S P X 100 + MP

[0169] In the above relational expression 1, S represents the mass ratio of saturated hydrocarbons included in the coating composition for surface coating of a secondary battery electrode active material derived from the SARA (saturatesaromatics-resins-asphaltenes) analysis result of Experimental Example 1, and S P represents the softening point of the coating composition for surface coating of a secondary battery electrode active material, and MP represents the volume ratio of the content of anisotropic petroleum pitch included in the coating composition for surface coating of a secondary battery electrode active material.

[0170]

[0171]

[0172] In the above Table 1, the volatile matter was defined as a substance that evaporates at a temperature of 300°C or lower when performing TGA (Thermogravimetric analysis) analysis in an N2 atmosphere.

[0173]

[0174] Preparation Example 4: Preparation of electrode active material containing silicon

[0175] A carbon-silicon composite was prepared by coating silicon on the surface of a porous carbon support having the properties described in Table 2 below as an electrode active material containing silicon.

[0176]

[0177]

[0178] Example 1: Preparation of secondary battery negative electrode material

[0179] (1) Using the mechano-fusion method, the coating composition for surface coating of the secondary battery electrode active material prepared in Preparation Example 1 was dry-coated on the surface of the negative electrode active material to form a coating layer on the surface of the negative electrode active material. At this time, the electrode active material containing silicon prepared in Preparation Example 4 was used as the negative electrode active material, and the coating was performed at a speed of 4000 rpm for 15 minutes.

[0180] (2) A negative electrode material for a secondary battery was manufactured by carbonizing a negative electrode active material having a coating layer formed on the surface at a temperature of 700°C for 60 minutes.

[0181]

[0182] Example 2: Manufacturing of secondary battery negative electrode material

[0183] A secondary battery negative electrode material was manufactured using the same method as Example 1. However, unlike Example 1, the coating composition for surface coating of a secondary battery electrode active material prepared in Preparation Example 2 was used instead of the coating composition for surface coating of a secondary battery electrode active material prepared in Preparation Example 1, and thus, a secondary battery negative electrode material was finally manufactured.

[0184]

[0185] Example 3: Preparation of secondary battery negative electrode material

[0186] A secondary battery negative electrode material was manufactured using the same method as Example 1. However, unlike Example 1, the coating composition for surface coating of a secondary battery electrode active material prepared in Preparation Example 3 was used instead of the coating composition for surface coating of a secondary battery electrode active material prepared in Preparation Example 1, thereby finally manufacturing a secondary battery negative electrode material.

[0187]

[0188] Comparative Example 1: Manufacturing of secondary battery negative electrode material

[0189] A secondary battery negative electrode material was manufactured using the same method as Example 1. However, unlike Example 1, the coating composition for surface coating of a secondary battery electrode active material prepared in Comparative Preparation Example 1 was used instead of the coating composition for surface coating of a secondary battery electrode active material prepared in Preparation Example 1, and thus, a secondary battery negative electrode material was finally manufactured.

[0190]

[0191] Comparative Example 2: Manufacturing of secondary battery negative electrode material

[0192] A secondary battery negative electrode material was manufactured using the same method as Example 1. However, unlike Example 1, a secondary battery negative electrode material was manufactured using a coating composition for surface coating of a secondary battery electrode active material prepared in Comparative Preparation Example 2 instead of a coating composition for surface coating of a secondary battery electrode active material prepared in Preparation Example 1.

[0193]

[0194] Experimental Example 4: Measurement of Physical Properties of Secondary Battery Anode Materials

[0195] The specific surface area, pore volume, median particle size, tap density, silicon content, and coating layer content of each secondary battery negative electrode material manufactured in Examples 1 to 3 and Comparative Examples 1 to 2 were measured, respectively, and are shown in Table 3 below. Meanwhile, the content of the coating layer was calculated through a graph measured by increasing the temperature at a rate of 5°C / min up to 900°C using a TGA (Thermogravimetric analysis) device, and the maximum weight content (W) appearing at 500 to 550°C max ) at the inflection point between 600 and 650℃, the weight content (W min ) was measured through the value minus the maximum weight content (W) that appears at 500 to 550°C. Specifically, max) is the weight weight that appears due to the oxidation reaction of silicon included in each of the secondary battery negative electrode materials manufactured in Examples 1 to 3 and Comparative Examples 1 to 2, and after a temperature of 500°C, the carbon included in each of the secondary battery negative electrode materials manufactured in Examples 1 to 3 and Comparative Examples 1 to 2 is oxidized and removed, and in each of the secondary battery negative electrode materials manufactured in Examples 1 to 3 and Comparative Examples 1 to 2, the coating layer is first removed due to oxidation, and then the carbon support in the electrode active material is oxidized. Therefore, the weight content of the carbon layer was measured by utilizing the difference in thermal decomposition behavior between the coating layer and the electrode active material to measure the content of the coating layer.

[0196]

[0197]

[0198]

[0199] Manufacturing Example 1: Manufacturing of a secondary battery half coin cell

[0200] (1) The secondary battery negative electrode material, conductive material, and binder manufactured in Example 1 were mixed to manufacture a negative electrode material slurry. At this time, the negative electrode material slurry was mixed with 80 wt% of the secondary battery negative electrode material manufactured in Example 1, 10 wt% of the conductive material, and 10 wt% of the binder based on 100 wt% of the total. Super-P, which is a conductive carbon black, was used as the conductive material, and styrene butadiene rubber (SBR) and sodium carboxymethyl cellulose (CMC) were mixed in a weight ratio of 5:5 as the binder.

[0201] (2) Copper foil was prepared, the negative electrode slurry was uniformly applied to the surface of the prepared copper foil, and dried in a vacuum oven at 120°C for 6 hours and 30 minutes to manufacture a negative electrode plate.

[0202] (3) Lithium foil was prepared, and the prepared lithium foil and the negative electrode plate were used as counter electrodes, and a porous polyethylene film was used as a separator, and a secondary battery half coin cell was manufactured by punching to have a diameter of 20 mm and a thickness of 3.2 mm. In addition, the manufactured secondary battery half coin cell was filled with an electrolyte, and a 1.3M LiPF6 solution containing 10 wt% fluoro-ethylene carbonate (FEC), 0.2 wt% lithium tetrafluoroborate (LiBF4), 0.5 wt% vinylene carbonate (VC), and 1 wt% propane sulton (PS) additive was dissolved in a mixed solution, and the mixed solution was a mixture of 30 vol% ethylene carbonate (EC), 50 vol% ethyl methyl carbonate (EMC), and 20 vol% dimethyl carbonate (DMC) with respect to the total 100 vol%.

[0203]

[0204] Manufacturing Example 2: Manufacturing of a secondary battery half coin cell

[0205] A secondary battery half coin cell was manufactured using the same method as Manufacturing Example 1. However, unlike Manufacturing Example 1, the secondary battery negative electrode material manufactured in Example 2 was used instead of the secondary battery negative electrode material manufactured in Example 1, and a secondary battery half coin cell was finally manufactured.

[0206]

[0207] Manufacturing Example 3: Manufacturing of a secondary battery half coin cell

[0208] A secondary battery half coin cell was manufactured using the same method as Manufacturing Example 1. However, unlike Manufacturing Example 1, the secondary battery negative electrode material manufactured in Example 3 was used instead of the secondary battery negative electrode material manufactured in Example 1, and a secondary battery half coin cell was finally manufactured.

[0209]

[0210] Comparative Manufacturing Example 1: Manufacturing of a Secondary Battery Half Coin Cell

[0211] A secondary battery half coin cell was manufactured using the same method as Manufacturing Example 1. However, unlike Manufacturing Example 1, the secondary battery negative electrode material manufactured in Comparative Example 1 was used instead of the secondary battery negative electrode material manufactured in Example 1, and a secondary battery half coin cell was finally manufactured.

[0212]

[0213] Comparative Manufacturing Example 2: Manufacturing of a Secondary Battery Half Coin Cell

[0214] A secondary battery half coin cell was manufactured using the same method as Manufacturing Example 1. However, unlike Manufacturing Example 1, the secondary battery negative electrode material manufactured in Comparative Example 2 was used instead of the secondary battery negative electrode material manufactured in Example 1, and a secondary battery half coin cell was finally manufactured.

[0215]

[0216] Comparative Manufacturing Example 3: Manufacturing of a Secondary Battery Half Coin Cell

[0217] A secondary battery half coin cell was manufactured using the same method as in Manufacturing Example 1. However, unlike Manufacturing Example 1, an electrode active material including silicon prepared in Preparation Example 4 was used instead of the secondary battery negative electrode material manufactured in Example 1, and a secondary battery half coin cell was finally manufactured.

[0218]

[0219] Experimental Example 5: Electrochemical Analysis

[0220] The cut-off voltage (formation: 0.005 to 1.5 V, cycle test: 0.005 to 1.5 V) and C-rate (formation: 0.1 to 0.1, 0.01C cut-off at 0.005 V) of each of the secondary battery half coin cells manufactured in Manufacturing Examples 1 to 3 and Comparative Manufacturing Examples 1 to 3 were measured, and the electric capacity (= charge capacity and discharge capacity), initial charge-discharge efficiency (ICE), and retention rate after 50 charge-discharge cycles were calculated, respectively, and are shown in Tables 4 and 5 below.

[0221]

[0222]

[0223] As can be seen in Tables 4 and 5 above, the secondary battery half coin cells manufactured in Manufacturing Examples 1 to 3 not only had excellent electric capacity, but also had excellent initial coulombic efficiency (ICE), and were confirmed to have remarkably excellent retention rate (=capacity retention rate) after 50 charge / discharge cycles.

[0224] Meanwhile, among the secondary battery half coin cells manufactured in Manufacturing Examples 1 to 3, it can be confirmed that the secondary battery half coin cell manufactured in Manufacturing Example 1 has the best physical properties, and compared to the secondary battery half coin cell manufactured in Manufacturing Example 1,

[0225] It was confirmed that the secondary battery half coin cell manufactured in Comparative Manufacturing Example 1 had a decrease in electric capacity, ICE, and capacity retention rate.

[0226] It was confirmed that the secondary battery half coin cell manufactured in Comparative Manufacturing Example 2 had a decrease in electric capacity, ICE, and capacity retention rate.

[0227] It was confirmed that the secondary battery half coin cell manufactured in Comparative Manufacturing Example 3 had a reduced capacity retention rate.

[0228] It was confirmed that the secondary battery half coin cell manufactured in Manufacturing Example 2 had a slight decrease in ICE and capacity retention rate.

[0229] It was confirmed that the secondary battery half coin cell manufactured in Manufacturing Example 3 had a slight decrease in electric capacity, ICE, and capacity retention rate.

[0230]

[0231] The above illustrates and describes specific embodiments. However, the invention is not limited to the aforementioned embodiments, and those skilled in the art will readily appreciate that various modifications and implementations can be made without departing from the spirit and scope of the invention as set forth in the claims below.

Claims

Petroleum pitch having a softening point of 1.200 to 270℃; and Volatile matter that evaporates below a temperature of 300℃; A coating composition for surface coating of a secondary battery electrode active material, comprising:

2. In paragraph 1, The above petroleum pitch is a coating composition for surface coating of a secondary battery electrode active material, which includes isotropic petroleum pitch and anisotropic petroleum pitch.

3. In paragraph 1, A coating composition for surface coating of a secondary battery electrode active material, wherein the coating composition contains 10.0 wt% or less of a volatile matter that volatilizes at a temperature of 300°C or less based on the total weight%.

4. In paragraph 2, A coating composition for surface coating of a secondary battery electrode active material, wherein the coating composition comprises 80 to 99 wt% of isotropic petroleum pitch and 1 to 20 wt% of anisotropic petroleum pitch based on the total weight%.

5. In paragraph 1, A coating composition for surface coating of a secondary battery electrode active material, wherein the secondary battery is a lead (Pd) storage battery, a nickel-cadmium (NiCd) battery, a nickel-metal (Ni-metal) hydrogen battery, a lithium ion (Li-ion) battery, a solid-state battery, a soft carbon battery, a hard carbon battery, or a lithium ion polymer (Li-ion) battery.

6. In paragraph 1, The above electrode active material is a coating composition for surface coating of a secondary battery electrode active material, which is a negative electrode active material.

7. In paragraph 6, The above negative active material is a coating composition for surface coating of a secondary battery electrode active material, which contains silicon (Si).

8. Electrode active material containing silicon; and A coating layer coated on the surface of the electrode active material; A secondary battery electrode material, wherein the coating layer is formed by carbonizing a coating composition for surface coating of the secondary battery electrode active material of claim 1.

9. Electrode active material containing silicon; and A secondary battery electrode material comprising a coating layer coated on the surface of the electrode active material; The secondary battery electrode material comprises a coating layer in an amount of 2.1 to 10.0 wt% based on the total weight of the secondary battery electrode material.

10. In paragraph 9, A secondary battery electrode material, wherein the coating layer comprises carbonized petroleum pitch.

11. In paragraph 10, The above petroleum pitch is a secondary battery electrode material including isotropic petroleum pitch and anisotropic petroleum pitch.

12. In paragraph 10, The above carbonized petroleum pitch is a secondary battery electrode material carbonized at a temperature of 600 to 800°C for 30 to 120 minutes.

13. In paragraph 8 or 9, A secondary battery electrode material, wherein the electrode active material comprises a non-porous carbon support containing at least one of hard carbon and soft carbon.

14. In paragraph 8 or 9, The above electrode active material includes a porous carbon support, A secondary battery electrode material, wherein the silicon is disposed on the surface and inside the pores of the porous carbon support.

15. In paragraph 8 or 9, The secondary battery electrode material is a secondary battery electrode material containing silicon in an amount of 30.0 to 80.0 wt% based on the total weight%.

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