Silicon-carbon composite, method for preparing same, and negative electrode and lithium secondary battery each comprising same

Abstract

The present invention relates to a silicon-carbon composite, a method for preparing same, and a negative electrode and a lithium secondary battery each comprising same, the silicon-carbon composite comprising: a carbon porous body; and silicon deposited in pores of the carbon porous body, wherein the carbon porous body is a carbide of a ZIF-based metal-organic framework, and the carbon porous body has a BET specific surface area of 1000 m2 / g to 2000 m2 / g.

Description

Silicon-carbon composite, method of manufacturing the same, negative electrode including the same, and lithium secondary battery

[0001] Cross-citation with related applications

[0002] This application claims the benefit of priority based on Korean Patent Application No. 10-2024-0189752 filed on December 18, 2024, and all contents disclosed in the document of said Korean Patent Application are incorporated herein as part of this specification.

[0003] Technology field

[0004] The present invention relates to a silicon-carbon composite, a method for manufacturing the same, a negative electrode comprising the same, and a lithium secondary battery.

[0005]

[0006] Recently, as the application areas of lithium-ion batteries have rapidly expanded to include not only power supply for electronic devices such as electrical, electronic, telecommunications, and computers, but also power storage for large-area devices such as automobiles and power storage systems, there is a growing demand for lithium-ion batteries that are high-capacity, high-output, and highly stable.

[0007] A lithium secondary battery is generally manufactured by applying a negative electrode active material capable of absorbing and releasing lithium ions or a positive electrode active material capable of inserting and extracting lithium ions, and optionally a material mixed with a binder and a conductive material, to a negative electrode current collector and a positive electrode current collector, respectively, to produce a negative electrode and a positive electrode, stacking these on both sides of a separator to form an electrode current collector of a predetermined shape, and then inserting this electrode current collector and a non-aqueous electrolyte into a battery case.

[0008] While carbon-based anode active materials are generally used, research is continuing to use materials with higher capacity as the demand for high-capacity and high-output lithium-ion batteries increases, and among these, research on silicon-based anode active materials is actively underway. Silicon-based anode active materials have a lithium capacity more than 10 times greater than that of carbon, and are emerging as next-generation anode active materials.

[0009] However, the aforementioned silicon-based negative electrode active materials have the problem of being difficult to use universally due to volume expansion during charging and discharging, resulting cracking or damage to active material particles, and consequently, degradation of lifespan characteristics. In particular, among the silicon-based negative electrode active materials, silicon oxide (SiOx) has good lifespan characteristics and possesses a higher charge / discharge capacity compared to carbon-based negative electrode active materials; however, it has the problem of poor initial efficiency due to the formation of an irreversible phase of lithium-silicon oxide during the lithium charging and discharging process.

[0010] Accordingly, silicon-carbon composites that do not form irreversible phases during the charging and discharging process of lithium are attracting attention as next-generation anode materials. However, although anode active materials containing silicon-carbon composites synthesized by combining silicon particles with carbon materials such as graphite and coke have improved lifespan characteristics and increased electrical conductivity compared to conventional silicon, they remain difficult to apply in technological fields requiring long lifespan characteristics, such as electric vehicles and energy storage systems (ESS).

[0011] Therefore, there is a need to develop next-generation cathode materials that possess excellent initial efficiency and lifespan characteristics, making them suitable for general use even in cases where long lifespan characteristics are required.

[0012] [Prior Art Literature]

[0013] [Patent Literature]

[0014] (Patent Document 1) KR 10-2021-0089720 A

[0015] (Patent Document 2) KR 10-2023-0113900 A

[0016]

[0017] The present invention aims to provide a silicon-carbon composite having high charge / discharge capacity and long lifespan characteristics by utilizing a carbon porous body having a ZIF-based metal-organic structure.

[0018] In addition, the present invention aims to provide a method for manufacturing the silicon-carbon composite.

[0019] In addition, the present invention aims to provide a negative electrode and a lithium secondary battery comprising the silicon-carbon composite.

[0020]

[0021] 1. The present invention comprises a carbon porous body; and silicon deposited within the pores of the carbon porous body, wherein the carbon porous body is a carbide of a ZIF-based metal-organic framework, and the BET specific surface area of ​​the carbon porous body is 1000 m² 2 / g or more than 2000 m 2 Provides a silicon-carbon composite having a g or less.

[0022] 2. In the present invention, in a scanning electron microscope (SEM) image taken at a magnification of 10,000 times, the average particle size (D) of the carbon porous body 50 The present invention provides a silicon-carbon composite having a thickness of 1 μm or more and 10 μm or less.

[0023] 3. The present invention provides a silicon-carbon composite according to 1. or 2. above, wherein the average diameter of the pores of the carbon porous body measured by BET analysis is 2.0 nm or less.

[0024] 4. The present invention provides a silicon-carbon composite in any one of 1 to 3 above, wherein the silicon is one or more selected from the group consisting of monosilane, disilane, dichlorosilane, monochlorosilane, and trichlorosilane.

[0025] 5. In any one of 1 to 4 above, the present invention has a BET specific surface area of ​​1.0 m² 2 / g or more than 2.0 m 2 Provides a silicon-carbon composite having a g or less.

[0026] 6. The present invention provides a method for manufacturing a silicon-carbon composite comprising: (S1) a step of forming a ZIF-based metal-organic framework; (S2) a step of heat-treating the ZIF-based metal-organic framework at a temperature of 350 ℃ to 1100 ℃ to form a carbon body; (S3) a step of mixing the carbon body with one or more selected from the group consisting of KOH, NaOH, ZnCl2, H3PO4, and K2CO3 in a weight ratio greater than 1:1 and less than 5, and heat-treating at a temperature of 600 ℃ to 900 ℃ to form a carbon porous body; and (S4) a step of depositing silicon on the carbon porous body for 1.5 hours to 2.5 hours; wherein step (S4) is performed at a temperature of 380 ℃ to 500 ℃.

[0027] 7. The present invention provides a method for manufacturing a silicon-carbon composite according to 6. above, wherein in step (S1), the ZIF-based metal-organic framework is formed by stirring zinc ions and an imidazole-based ligand.

[0028] 8. The present invention provides a method for manufacturing a silicon-carbon composite according to 6. or 7. above, wherein the molar ratio of the zinc ion to the imidazole-based ligand is 1:1 to 1:3.

[0029] 9. The present invention provides a method for manufacturing a silicon-carbon composite, wherein, in any one of 6 to 8 above, step (S2) is carried out in an argon atmosphere.

[0030] 10. The present invention provides a method for manufacturing a silicon-carbon composite, wherein, in any one of 6 to 9 above, the step (S2) is carried out for 1 hour to 5 hours.

[0031] 11. The present invention provides a method for manufacturing a silicon-carbon composite, wherein, in any one of 6 to 10 above, the heat treatment temperature in step (S2) is 800 ℃ to 1000 ℃.

[0032] 12. The present invention provides a cathode comprising a silicon-carbon composite according to any one of 1 to 5 above.

[0033] 13. The present invention provides a lithium secondary battery comprising a negative electrode according to 12. above.

[0034] The silicon-carbon composite of the present invention comprises a carbon porous body, which is a carbide of a ZIF-based metal-organic framework, and silicon deposited thereon, thereby securing a high specific surface area of ​​the carbon porous body and mitigating the degradation phenomenon of silicon particles, which can improve the initial capacity and lifespan characteristics of a lithium secondary battery.

[0035] In addition, the method for manufacturing a silicon-carbon composite of the present invention can produce a silicon-carbon composite having a uniform particle size without a separate activation process or classification process.

[0036] In addition, the lithium secondary battery of the present invention includes a negative electrode comprising a silicon-carbon composite according to the present invention, thereby having excellent initial capacity and lifespan characteristics.

[0037] Figure 1 shows an SEM image of the silicon-carbon composite of Example 1.

[0038] Figure 2 is a graph plotting the slope of the Relative Pressure-Desorption graph based on the BET analysis results for the carbon porous body prepared in Example 1.

[0039]

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

[0041] Terms and words used in this specification and claims shall not be interpreted as being limited to their ordinary or dictionary meanings, but shall be interpreted in a meaning and concept consistent with the technical spirit of the invention, based on the principle that the inventor can appropriately define the concept of the terms to best describe his invention.

[0042]

[0043] silicon-carbon composite

[0044] The present invention comprises a carbon porous body; and silicon deposited within the pores of the carbon porous body, wherein the carbon porous body is a carbide of a ZIF-based metal-organic framework, and the BET specific surface area of ​​the carbon porous body is 1000 m² 2 / g or more than 2000 m 2 Provides a silicon-carbon composite having a g or less.

[0045] Generally, porous carbon materials used in silicon-carbon composites include porous activated carbon, carbon nanotubes, carbon nanofibers, graphene, graphene oxide, carbon black, carbon pores, carbon aerogels, and carbon sponges; however, in the present invention, a carbide of a ZIF-based metal-organic framework is used as the porous carbon material. That is, the porous carbon material of the present invention is a ZIF-based porous carbon material.

[0046] The above-mentioned ZIF-based metal-organic framework is a type of Metal-Organic Framework (MOF) in which metal ions and organic ligands combine to form a porous network structure; it is a porous network structure primarily formed by the combination of metal ions and imidazole-based ligands. The above-mentioned ZIF-based metal-organic framework possesses high pore volume and specific surface area, which promotes the adsorption and dispersion of silicon onto the carbon porous material and helps the silicon-carbon composite to have a high energy storage density.

[0047] ZIF structures with desired characteristics can be designed depending on the selection of the aforementioned metal ions and organic ligands. Specifically, the pore structure, thermal stability, and chemical reactivity of the ZIF may vary depending on the selection of the metal ions, and each ligand can provide functionality suitable for specific applications.

[0048] According to one embodiment of the present invention, the metal ion may be one or more selected from the group consisting of zinc ion, cobalt ion, nickel ion, manganese ion, calcium ion, aluminum ion, copper ion, iron ion, chromium ion, and magnesium ion, and preferably may be a zinc ion.

[0049] According to one embodiment of the present invention, the imidazole-based ligand is a benzimidazole ligand, a 2-methylimidazole ligand, a 2-ethylimidazole ligand, a 2,4,5-trimethylimidazole ligand, a 2-aminoimidazole ligand, a 4,5-dimethylimidazole ligand, a 1,2-dimethylimidazole ligand, a 2-chlorimidazole ligand, a 2-nitroimidazole ligand, a 2-hydroxyethylimidazole ligand, It may be one or more selected from the group consisting of 2-phenylimidazole ligands and 2,4-dichlorimidazole ligands, and preferably may be a benzimidazole ligand.

[0050] According to one embodiment of the present invention, the silicon can be deposited on a carbon porous body using a chemical vapor deposition process, a physical vapor deposition process, a thermochemical deposition process, a chemical precipitation process, a sol-gel deposition process, and an electron beam deposition process, and preferably, it can be deposited on a carbon porous body using a chemical vapor deposition process.

[0051] The chemical vapor deposition process described above includes a process of exposing a gaseous silicon precursor, such as silane (SiH4) or dichlorosilane (SiH2Cl2), to the surface of a carbon porous body at a high temperature, and allowing the silicon precursor gas to penetrate into the pores of the carbon porous body to form solid silicon through a chemical reaction. The chemical vapor deposition process has the advantage of being able to form a silicon layer of high purity and uniformity on the surface or inside the pores of the carbon porous body, and allowing for precise thickness control.

[0052] According to one embodiment of the present invention, the silicon may be one or more selected from the group consisting of monosilane, disilane, dichlorosilane, monochlorosilane, and trichlorosilane, and preferably may be monosilane.

[0053] When the specific surface area of ​​the above-mentioned carbon porous material is high, silicon particles are better dispersed within the pores, the contact area with the electrolyte is expanded, and the diffusion path of lithium ions is shortened, which has the advantage of improving ionic conductivity and further enhancing electrochemical performance. However, if the specific surface area is excessively large, the material density decreases, which may be disadvantageous in terms of energy density; therefore, it is important to maintain an appropriate specific surface area.

[0054] According to one embodiment of the present invention, the BET specific surface area of ​​the carbon porous body can be measured through BET (Brunauer-Emmett-Teller) analysis, and the BET specific surface area of ​​the carbon porous body is 1000 m² 2It may be greater than / g. More specifically, the BET specific surface area of ​​the carbon porous body is 1000 m² 2 / g or more, 1100 m 2 / g or more, 1200 m 2 / g or more, 1300 m 2 / g or more, or 1400 m 2 It may be greater than / g, and 1800 m 2 / g or less, 1900 m 2 / g or less, or 2000 m 2 It may be / g or less. The BET specific surface area of ​​the above-mentioned carbon porous body is 1000 m² 2 If it is less than / g, there is a problem of inferior capacitance characteristics due to the small silicon deposition amount caused by the small pore volume, and 2000 m 2 If it exceeds / g, the silicon deposition amount is excessive, leading to a problem of inferior lifespan characteristics.

[0055] The above BET analysis is an experimental technique for measuring the surface area and pore structure of a substance, primarily using an inert gas such as nitrogen (N2) to calculate the surface area through the adsorption and desorption of the gas. First, the sample is placed in the analysis equipment, and the gas is adsorbed at a low temperature. Then, the amount of adsorbed gas is measured at various pressures while adjusting the gas pressure. The measured data is plotted as a function of the gas pressure to create an adsorption isotherm, and then the surface area, pore volume, and pore size distribution of the sample are calculated using the BET equation regarding the relationship between the amount of adsorbed gas and the gas pressure. In particular, the specific surface area of ​​the substance can be calculated using the unit area of ​​gas molecules and the amount of single-layer adsorption.

[0056] Average particle size (D of the above carbon porous body) 50 ) is a factor that can affect the characteristics of the porous structure and ion conductivity, and an appropriate range of average particle size (D 50 When the condition is satisfied, the specific surface area of ​​the carbon porous material increases, leading to higher reactivity and further improved ion conductivity and mass transfer efficiency.

[0057] According to one embodiment of the present invention, in a scanning electron microscope (SEM) image taken at a magnification of 10,000 times, the average particle size (D) of the carbon porous body 50 ) may be 1 μm or more and 10 μm or less. More specifically, the average particle size (D) of the carbon porous body. 50 ) may be 1.5 μm or more, 2 μm or more, 2.5 μm or more, 3 μm or more, 3.5 μm or more, 4 μm or more, 4.5 μm or more, 5 μm or more, 5.5 μm or more, and may be 9.5 μm or less, 9 μm or less, 8.5 μm or less, 8 μm or less, 7.5 μm or less, 7 μm or less, 6.5 μm or less, 6 μm or less. Here, when measuring the average particle size of the plurality of primary particles from an SEM image, the particle size of each primary particle may be the particle size based on the major axis of the primary particle. Within this range, the rolling density of the first cathode active material can be further improved, and the lifespan of the lithium secondary battery can be further improved. The average particle diameter (D) of the carbon porous body 50 If the above range is satisfied, it can be applied to the cathode material manufacturing process without an additional size selection process, thereby further improving processability, providing a sufficient reaction surface area during charging / discharging, and is more advantageous for maintaining ion conductivity.

[0058] The above-mentioned carbon porous material possesses a large active surface area as its specific surface area increases with a smaller average pore diameter. By controlling the average pore diameter of the carbon porous material in this way, conductivity as an electrode material can be further enhanced. In particular, in lithium-ion batteries, this increases the storage and release efficiency of lithium ions, thereby extending the battery's capacity and lifespan. Furthermore, the fine pore structure enhances the structural stability of the carbon porous material, making it effective for long-term use.

[0059] According to one embodiment of the present invention, the average diameter of the pores of the carbon porous body measured by BET analysis may be 2.0 nm or less. More specifically, the average diameter of the pores of the carbon porous body may be 0.01 nm or more, 0.03 nm or more, 0.05 nm or more, 0.08 nm or more, 0.1 nm or more, 0.3 nm or more, and 1.8 nm or less. When the average diameter of the pores of the carbon porous body measured by BET analysis satisfies the above range, sufficient space for silicon deposition can be secured, thereby further improving silicon deposition efficiency.

[0060] According to one embodiment of the present invention, the silicon-carbon composite has a BET specific surface area of ​​1.0 m² 2 / g or more than 2.0 m 2 It may be / g or less. Specifically, the silicon-carbon composite has a BET specific surface area of ​​1.0 m² 2 / g or more, or 1.1 m 2 It may be greater than / g, and 1.9 m 2 / g or less, or 2.0 m 2 It may be less than or equal to / g. When the BET specific surface area of ​​the silicon-carbon composite is within the above range, silicon is sufficiently deposited in the pores within the carbon composite, thereby improving capacitance characteristics, and silicon is deposited on the surface to an appropriate degree without any remaining pores, thereby improving lifespan characteristics.

[0061]

[0062] Method for manufacturing silicon-carbon composites

[0063] The present invention provides a method for manufacturing a silicon-carbon composite for manufacturing the silicon-carbon composite.

[0064] The above method for manufacturing a silicon-carbon composite comprises: (S1) a step of forming a ZIF-based metal-organic framework; (S2) a step of heat-treating the ZIF-based metal-organic framework at a temperature of 350 ℃ to 1100 ℃ to form a carbon body; (S3) a step of mixing the carbon body with one or more selected from the group consisting of KOH, NaOH, ZnCl2, H3PO4, and K2CO3 in a weight ratio greater than 1:1 and less than 5, and heat-treating at a temperature of 600 ℃ to 900 ℃ to form a carbon porous body; and (S4) a step of depositing silicon on the carbon porous body for 1.5 hours to 2.5 hours; wherein the step (S4) is carried out at a temperature of 380 ℃ to 500 ℃.

[0065]

[0066] The above step (S1) is a step of forming a ZIF-based metal-organic framework that serves as a material for a carbon porous body, and may be a step of forming a ZIF-based metal-organic framework by mixing and stirring zinc ions and an imidazole-based ligand.

[0067] According to one embodiment of the present invention, the zinc ion may be introduced in the form of a zinc compound, and the zinc compound may be one or more selected from the group consisting of zinc acetate (Zn(C2H2O2)2), zinc nitrate (Zn(NO3)2), and zinc sulfite (ZnSO4), and preferably may be zinc acetate (Zn(C2H2O2)2).

[0068] According to one embodiment of the present invention, the imidazole-based ligand may be introduced in the form of an imidazole-based compound, and the imidazole-based compound is benzimidazole, 2-methylimidazole, 2-ethylimidazole, 2,4,5-trimethylimidazole, 2-aminoimidazole, 4,5-dimethylimidazole, 1,2-dimethylimidazole, 2-chlorimidazole, 2-nitroimidazole, 2-hydroxyethylimidazole, 2-phenylimidazole, and It may be one or more selected from the group consisting of 2,4-dichlorimidazole, and preferably may be benzimidazole.

[0069] According to one embodiment of the present invention, a solvent may be mixed with zinc ions and an imidazole-based ligand in step (S1), and the solvent may be one or more selected from the group consisting of water, methanol, ethanol, toluene, ammonia, acetonitrile, dichloromethane (DCM), dimethyl carbonate (DMC), propylene carbonate (PC), and ethylene carbonate (EC).

[0070] When synthesizing a ZIF-based metal-organic framework in step (S1) above, various conditions such as reaction temperature and pH can affect the structure and properties of the ZIF. In particular, the reaction temperature can affect the crystallization rate and crystallinity. An appropriate range of reaction temperatures can increase the crystallization rate and ensure complete crystal formation. Additionally, since the reaction temperature affects the pore structure, an appropriate range of reaction temperatures can achieve the target pore size and shape.

[0071] According to one embodiment of the present invention, the step (S1) may be performed at a temperature of 0°C or higher and 100°C or lower. More specifically, the step (S1) may be performed at a temperature of 0°C or higher, 10°C or higher, 20°C or higher, 30°C or higher, 40°C or higher, or 50°C or higher, and also at 100°C or lower, 90°C or lower, 80°C or lower, 70°C or lower, or 60°C or lower. When the temperature of the step (S1) satisfies the above range, appropriate pore size and shape can be achieved.

[0072] In addition to the reaction temperature, the pH during the synthesis of ZIF-based metal-organic frameworks can also affect the stability, pore structure, and reaction rate of the structure. An appropriate pH facilitates the reaction between metal ions and ligands, enabling the formation of a more stable structure, optimizing the pore structure, and further increasing reaction efficiency.

[0073] According to one embodiment of the present invention, step (S1) may be performed at a pH of 8 or higher and 12 or lower. More specifically, step (S1) may be performed at a pH of 8.0 or higher, 8.5 or higher, 9.0 or higher, or 9.5 or higher, and may also be performed at a pH of 12.0 or lower, 11.5 or lower, 11.0 or lower, 10.5 or lower, or 10.0 or lower. When the pH in step (S1) satisfies the above range, the reaction between the metal ion and the ligand is facilitated, allowing for the formation of a more stable structure, optimization of the pore structure, and further increase in reaction efficiency.

[0074] If an appropriate molar ratio of the zinc ion and the imidazole-based ligand is maintained in step (S1) above, the structural stability can be further improved when forming the desired ZIF structure. Additionally, the specific surface area, pore size, and morphology of the ZIF-based metal-organic framework may vary depending on the molar ratio. When the molar ratio of the zinc ion and the imidazole-based ligand satisfies an appropriate range, the synthesis of the ZIF-based metal-organic framework is carried out more efficiently, impurities or defects are minimized, and the quality of the final product can be further improved.

[0075] According to one embodiment of the present invention, the molar ratio of the zinc ion to the imidazole-based ligand may be 1:1 to 3. More specifically, the molar ratio of the zinc ion to the imidazole-based ligand may be 1:1 or higher, 1:1.2 or higher, 1:1.3 or higher, 1:1.4 or higher, 1:1.5 or higher, 1:1.6 or higher, 1:1.7 or higher, 1:1.8 or higher, 1:1.9 or higher, 1:2 or higher, 1:3 or lower, 1:2.9 or lower, 1:2.8 or lower, 1:2.7 or lower, 1:2.6 or lower, 1:2.5 or lower, 1:2.4 or lower, 1:2.3 or lower, 1:2.2 or lower, and 1:2.1 or lower. When the molar ratio of the zinc ion to the imidazole-based ligand satisfies the above range, the synthesis of the ZIF-based metal-organic framework is carried out more efficiently, impurities or defects are minimized, and the quality of the final product can be further improved.

[0076] The above step (S2) is a step of forming a carbon body using the above ZIF-based metal-organic framework, and can be carried out by heat-treating the above ZIF-based metal-organic framework at a temperature of 800 ℃ to 1000 ℃.

[0077] The specific surface area value of the formed carbon body may vary depending on the heat treatment temperature in the above step (S2). For example, if the heat treatment temperature is too low, the pores of the carbon body may not be properly formed, resulting in a relatively low specific surface area. In addition, if the heat treatment temperature is too high, the pores of the carbon body may be excessively lost or the ZIF structure may be damaged, making it difficult to obtain the intended specific surface area value.

[0078] According to one embodiment of the present invention, the heat treatment temperature in step (S2) may be 350 ℃ or higher and 1100 ℃ or lower. More specifically, the heat treatment temperature in step (S2) may be 380 ℃ or higher, 400 ℃ or higher, 420 ℃ or higher, 450 ℃ or higher, 480 ℃ or higher, 500 ℃ or higher, 1100 ℃ or lower, 1000 ℃ or lower, 900 ℃ or lower, 800 ℃ or lower, 700 ℃ or lower, or 600 ℃ or lower. If the heat treatment temperature in step (S2) satisfies the above range, the pore structure of the carbon body is effectively formed to secure a high specific surface area, which provides a sufficient surface area during subsequent silicon deposition, thereby enabling uniform and stable deposition.

[0079] In addition to the heat treatment temperature of the above step (S2), the heat treatment time can also influence the determination of the physical and chemical properties of the carbon body. When an appropriate heat treatment time is satisfied, a carbon body with a high specific surface area can be formed through complete pore formation, and impurities are removed and the risk of byproducts being redeposited is reduced.

[0080] According to one embodiment of the present invention, the step (S2) may be carried out for 1 hour to 5 hours. More specifically, the step (S2) may be carried out for 1 hour or more, 1.5 hours or more, and for 5 hours or less, 4 hours or less, 3 hours or less.

[0081] According to one embodiment of the present invention, the step (S2) may be performed in an argon atmosphere.

[0082] The above step (S3) is a step of forming a carbon porous body by mixing the carbon body formed in step (S2) with one or more selected from the group consisting of KOH, NaOH, ZnCl2, H3PO4, and K2CO3 in a weight ratio greater than 1:1 and less than 5, and heat treating at a temperature of 600°C to 900°C. Specifically, to form the carbon porous body, the carbon body may be mixed with one or more selected from the group consisting of KOH, NaOH, ZnCl2, H3PO4, and K2CO3 in a weight ratio greater than 1:1, greater than 2, greater than 3, less than 4, or less than 5, and heat treating at a temperature of 600°C or higher, 650°C or higher, 700°C or higher, 800°C or lower, 850°C or lower, or 900°C or lower. By performing the above step (S3), the specific surface area of ​​the carbon porous body can be increased. On the other hand, if the above step (S3) is not performed, the carbon body has a low specific surface area and does not provide sufficient space for silicon to be deposited. Consequently, this hinders the uniform deposition of silicon on the carbon body (in the state where the above step (S3) is not performed), which can lead to a problem of reduced overall performance of the silicon-carbon composite and negatively affect battery performance, such as reduced battery capacity. If the mixing ratio of the above step (S3) is 1:1 or less, the specific surface area of ​​the carbon porous body is small, and if it is 1:5 or more, the specific surface area of ​​the carbon porous body is excessive, resulting in a problem of inferior capacity characteristics or lifespan characteristics of the battery. If the temperature of the above step (S3) is less than 600 ℃, the thermal energy required for the chemical reaction is not sufficiently transferred, and if it exceeds 900 ℃, the carbon body is excessively carbonized, resulting in a problem of pore destruction.

[0083] The above step (S4) is a step of depositing silicon on the carbon porous body, and can be carried out by depositing silicon on the carbon porous body formed in the above step (S3) for 1.5 to 2.5 hours.

[0084] The silicon may be injected in the form of silane gas and deposited on the carbon porous body. In this case, if the silicon deposition time is too short, a problem may arise where the silicon is not sufficiently deposited on the carbon porous body. This degrades the performance of the silicon-carbon composite, thereby lowering the capacity and initial efficiency characteristics of the battery. On the other hand, if the silicon deposition time is too long, silicon may be deposited on all surfaces of the carbon porous body, leading to a problem where the lifespan characteristics of the battery are degraded. Therefore, it is necessary to perform the above step (S4) for an appropriate amount of time.

[0085] According to one embodiment of the present invention, the step (S4) may be performed for 1.5 hours to 2.5 hours. More specifically, the step (S4) may be performed for 1.5 hours or more, 1.6 hours or more, 1.7 hours or more, 1.8 hours or more, 1.9 hours or more, 2.5 hours or less, 2.4 hours or less, 2.3 hours or less, 2.2 hours or less, and 2.1 hours or less.

[0086] In the above step (S4), if the silicon flow rate satisfies an appropriate range and the silicon deposition rate is maintained constant, silicon can be sufficiently deposited not only on the surface of the carbon porous body but also inside the pores.

[0087] According to one embodiment of the present invention, in step (S4), the flow rate of silicon may be 50 sccm or more and 1000 sccm or less. More specifically, the flow rate of silicon may be 50 sccm or more, 100 sccm or more, 150 sccm or more, 200 sccm or more, 250 sccm or more, 300 sccm or more, 350 sccm or more, or 400 sccm or more, and may also be 1000 sccm or less, 950 sccm or less, 900 sccm or less, 850 sccm or less, 800 sccm or less, 750 sccm or less, 700 sccm or less, 650 sccm or less, 600 sccm or less, 550 sccm or less, 500 sccm or less, or 450 sccm or less. In the above step (S3), if the silicon flow rate satisfies the above range, silicon can be sufficiently deposited not only on the surface of the carbon porous body but also inside the pores.

[0088] In the above step (S4), an appropriate silicon deposition temperature ensures that silicon is converted into a gaseous state and deposited uniformly on the carbon porous body, and optimizes the chemical interaction between silicon and carbon to further improve the stability and performance of the silicon-carbon composite.

[0089] According to one embodiment of the present invention, the step (S4) is performed at a temperature of 380°C to 500°C. More specifically, the step (S4) may be performed at a temperature of 380°C or higher, 400°C or higher, or 420°C or higher, and 440°C or lower, 460°C or lower, 480°C or lower, or 500°C or lower. When the temperature of the step (S4) is within the above range, it has the effect of depositing an appropriate amount of silicon on the carbon porous body while sufficiently transferring the thermal energy required for silicon deposition, thereby improving capacity characteristics and lifespan characteristics. On the other hand, if the temperature of the step (S4) is less than 380°C, the energy required for silicon deposition is not sufficiently supplied, making silicon deposition difficult and causing problems with capacity characteristics, and if it exceeds 500°C, silicon is deposited on all surfaces of the carbon porous body, causing problems with the lifespan characteristics of the battery.

[0090] Unlike conventional silicon-carbon composite manufacturing methods, the method for manufacturing a silicon-carbon composite according to the present invention is characterized by the fact that, by using a ZIF-based metal-organic framework prepared in steps (S2) to (S4) instead of activated carbon, a carbon porous body of relatively uniform size can be obtained, and thus, it does not undergo a separate activation process, grinding process, and classification process.

[0091]

[0092] cathode

[0093] The present invention provides a cathode comprising the silicon-carbon composite.

[0094] The above may include a negative current collector and a negative active material layer formed on the above negative current collector, and the negative active material layer may include the silicon-carbon composite.

[0095] The above-mentioned negative electrode current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery, and for example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., and aluminum-cadmium alloy may be used. In addition, the above-mentioned negative electrode current collector may typically have a thickness of 3 μm to 500 μm, and fine irregularities may be formed on the surface of the current collector to strengthen the bonding strength of the negative electrode active material. For example, it may be used in various forms such as a film, sheet, foil, net, porous body, foam, nonwoven fabric, etc.

[0096] The above-mentioned cathode active material layer may, together with the cathode active material, optionally include a conductive material and a binder as needed.

[0097] The conductive material described above is a component for further improving the conductivity of the negative electrode active material, and may be added in an amount of 10% by weight or less, preferably 5% by weight or less, based on the total weight of the negative electrode active material layer. Such conductive material is not particularly limited as long as it is conductive without causing chemical changes in the battery, and for example, graphite such as natural graphite or artificial graphite; carbon black such as acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black; conductive fibers such as carbon fibers or metal fibers; fluorinated carbon; metal powders such as aluminum or nickel powder; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; conductive materials such as polyphenylene derivatives may be used.

[0098] The above binder is a component that assists in the bonding between the conductive material, the active material, and the current collector, and is typically added in an amount of 0.1% to 10% by weight based on the total weight of the negative electrode active material layer. Examples of such binders include polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene-butadiene rubber, nitrile-butadiene rubber, fluororubber, and various copolymers thereof.

[0099] The above cathode may be manufactured by applying and drying a composition for forming a cathode active material layer, prepared by dissolving or dispersing a cathode active material and optionally a binder and a conductive material in a solvent, onto a cathode current collector, or by casting the composition for forming a cathode active material layer onto a separate support and then laminating the film obtained by peeling from the support onto a cathode current collector.

[0100]

[0101] lithium secondary battery

[0102] The present invention provides a lithium secondary battery comprising a cathode comprising the above-mentioned cathode.

[0103] The above lithium secondary battery may comprise the negative electrode; the positive electrode; a separator interposed between the negative electrode and the positive electrode; and an electrolyte. Additionally, the above lithium secondary battery may optionally further comprise a battery container housing an electrode assembly of the negative electrode, the positive electrode, and the separator, and a sealing member sealing the battery container.

[0104] The above positive electrode may include a positive electrode current collector and a positive electrode active material layer located on the positive electrode current collector.

[0105] The above positive current collector may include a highly conductive metal, and is not particularly limited as long as it facilitates the adhesion of the positive active material layer and is non-reactive within the voltage range of the battery. The above positive current collector may be, for example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface treated with carbon, nickel, titanium, silver, etc. Additionally, the above positive current collector may typically have a thickness of 3 μm to 500 μm, and may form fine irregularities on the surface of the current collector to increase the adhesion of the positive active material. It may be used in various forms, such as films, sheets, foils, nets, porous bodies, foams, and nonwoven fabrics.

[0106] The above positive active material layer may, together with the positive active material, optionally include a conductive material and a binder as needed. The above positive active material is LiCoO2, LiCoPO4, LiNiO2, Li x Ni a Co b M 1 c M 2 d O2(M 1 and M 2 Each is independently selected from the group consisting of Al, Mn, Cu, Fe, V, Cr, Mo, Ga, B, W, Mo, Nb, Mg, Hf, Ta, La, Ti, Sr, Ba, Ce, F, P, S, and Y, and 0.9≤x≤1.1, 0 <a<1.0, 0<b<1.0, 0≤c<0.5, 0≤ d<0.5, a+b+c+d=1이다.), LiMnO2, LiMnO3, LiMn2O3, LiMn2O4, LiMn 2-e M 3 e O2(M 3 ...is one or more selected from the group consisting of Co, Ni, Fe, Cr, Zn, and Ta, and 0.01≤e≤0.1), Li2Mn3M 4 O8(M 4is one or more selected from the group consisting of Ci, Ni, Fe, Cu and Zn), and may be one selected from the group consisting of LiFePO4, Li2CuO2, LiV3O8, V2O5, Cu2V2O7 and lithium metal.

[0107] The binder in the above positive active material layer serves to improve adhesion between positive active material particles and adhesion between the positive active material and the current collector. Specific examples include polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, polymethyl methacrylate, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene butadiene rubber (SBR), fluororubber, polyacrylic acid, and polymers in which hydrogens thereof are substituted with Li, Na, or Ca, or various copolymers thereof, and one of these alone or a mixture of two or more may be used. The above binder may be included in an amount of 0.1% to 15% by weight relative to the total weight of the positive active material layer.

[0108] The conductive material of the positive electrode active material layer is used to impart conductivity to the electrode, and in the battery being constructed, any material that possesses electronic conductivity without causing chemical changes can be used without any special limitations. Specific examples include graphite such as natural graphite or artificial graphite; carbon-based materials such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, and carbon fibers; metal powder or metal fibers such as copper, nickel, aluminum, and silver; conductive tubes such as carbon nanotubes; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives, and one of these alone or a mixture of two or more may be used. The conductive material may be included in an amount of 0.1% to 15% by weight relative to the total weight of the positive electrode active material layer.

[0109] The above-mentioned anode may be manufactured according to a conventional anode manufacturing method. Specifically, the above-mentioned anode may be manufactured by applying a composition for forming an anode active material layer, prepared by dissolving or dispersing the above-mentioned anode active material and, optionally, a binder, a conductive material, and a dispersant in a solvent, onto an anode current collector, followed by drying and rolling, or by casting the composition for forming an anode active material layer onto a separate support and then laminating a film obtained by peeling from the support onto an anode current collector.

[0110] The above solvent may be a solvent generally used in the relevant technical field, and may include dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), dimethylformamide (DMF), acetone, or water, and one of these alone or a mixture of two or more may be used. The amount of the above solvent used is sufficient if it is sufficient to dissolve or disperse the anode active material, conductive material, binder, and dispersant, taking into account the coating thickness of the slurry and the manufacturing yield, and to have a viscosity that can exhibit excellent thickness uniformity when coated for anode manufacturing thereafter.

[0111] The above separator separates the negative electrode and the positive electrode and provides a pathway for the movement of lithium ions. It can be used without special restrictions as long as it is typically used as a separator in a lithium secondary battery, and it is particularly desirable that it has low resistance to the movement of electrolyte ions and excellent electrolyte wettability. Specifically, a porous polymer film, such as a porous polymer film made of a polyolefin-based polymer like ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer, and ethylene / methacrylate copolymer, or a laminated structure of two or more layers thereof may be used. In addition, a conventional porous nonwoven fabric, such as a nonwoven fabric made of high-melting-point glass fiber or polyethylene terephthalate fiber, may be used. Furthermore, a coated separator containing ceramic components or polymer materials may be used to ensure heat resistance or mechanical strength, and it may optionally be used in a single-layer or multi-layer structure.

[0112] Examples of the above electrolytes include organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel-type polymer electrolytes, solid inorganic electrolytes, molten inorganic electrolytes, etc., which can be used in the manufacture of lithium secondary batteries, but are not limited to these. As a specific example, the above electrolyte may include an organic solvent and a lithium salt.

[0113] The above organic solvent may be used without special restrictions as long as it can serve as a medium through which ions involved in the electrochemical reaction of the battery can move. Specifically, the above organic solvent may include ester-based solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, and ε-caprolactone; ether-based solvents such as dibutyl ether or tetrahydrofuran; ketone-based solvents such as cyclohexanone; and aromatic hydrocarbon-based solvents such as benzene and fluorobenzene. Carbonate-based solvents such as dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (MEC), ethyl methyl carbonate (EMC), ethylene carbonate (EC), and propylene carbonate (PC); alcohol-based solvents such as ethyl alcohol and isopropyl alcohol; nitriles such as R-CN (where R is a straight-chain, branched, or cyclic hydrocarbon group having 2 to 20 carbon atoms and may include a double bond, a directional ring, or an ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; or sulfolanes may be used. Among these, a carbonate-based solvent is preferred, and a mixture of a cyclic carbonate (e.g., ethylene carbonate or propylene carbonate, etc.) having high ionic conductivity and high dielectric constant that can improve the charge / discharge performance of the battery, and a low-viscosity linear carbonate-based compound (e.g., ethylmethyl carbonate, dimethyl carbonate or diethyl carbonate, etc.) is more preferred.

[0114] The above lithium salt may be used without special restrictions as long as it is a compound capable of providing lithium ions used in lithium secondary batteries. Specifically, the anion of the above lithium salt is F - , Cl - , Br - , I - , NO3 - , N(CN)2 - , BF4 - , CF3CF2SO3 - , (CF3SO2)2N - , (FSO2)2N - , CF3CF2(CF3)2CO - , (CF3SO2)2CH - , (SF5)3C - , (CF3SO2)3C - , CF3(CF2)7SO3 - , CF3CO2 - , CH3CO2 - , SCN - and (CF3CF2SO2)2N - The lithium salt may be at least one selected from the group consisting of LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAlO4, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2, LiCl, LiI, or LiB(C2O4)2. It is preferable to use the lithium salt within the range of 0.1 M to 2.0 M. When the concentration of the lithium salt falls within the above range, the electrolyte has appropriate conductivity and viscosity, so it can exhibit excellent electrolyte performance and lithium ions can move effectively.

[0115] In addition to the above electrolyte components, the above electrolyte may further include one or more additives for the purpose of improving the lifespan characteristics of the battery, suppressing the decrease in battery capacity, and improving the discharge capacity of the battery, such as, for example, a haloalkylene carbonate-based compound such as difluoroethylene carbonate, pyridine, triethylphosphite, triethanolamine, cyclic ether, ethylene diamine, n-glyme, triamide hexaphosphate, nitrobenzene derivative, sulfur, quinone imine dye, N-substituted oxazolidinone, N,N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2-methoxyethanol, or aluminum trichloride. In this case, the above additives may be included in an amount of 0.1% to 5% by weight based on the total weight of the electrolyte.

[0116] The external shape of the lithium secondary battery of the present invention is not particularly limited, but can be a cylindrical shape using a can, a prismatic shape, a pouch shape, or a coin shape.

[0117] The lithium secondary battery according to the present invention can be used not only as a battery cell used as a power source for a small device, but can also preferably be used as a unit cell in a medium-to-large battery module comprising a plurality of battery cells.

[0118] Accordingly, a battery module including the above-mentioned lithium secondary battery as a unit cell and a battery pack including the same are provided.

[0119] The above battery module or battery pack can be used as a power source for one or more medium-to-large devices, including a power tool; an electric vehicle (EV), a hybrid electric vehicle, and a plug-in hybrid electric vehicle (PHEV); or a power storage system.

[0120]

[0121] Hereinafter, embodiments of the present invention are described in detail so that those skilled in the art can easily implement the invention. However, the present invention may be embodied in various different forms and is not limited to the embodiments described herein.

[0122]

[0123] Example 1

[0124] Solution 1 was prepared by adding 2.23 g of zinc acetate to 40 ml of methanol and stirring for 10 minutes. Next, 2.4 g of benzimidazole was added to 83.2 ml of methanol and stirred for 10 minutes, then 108 ml of toluene was added and stirred again for 10 minutes, and then 13.6 ml of ammonium hydroxide was added and stirred again for 10 minutes to prepare Solution 2.

[0125] The above-prepared solution 1 and solution 2 were mixed and stirred for 3 hours to form a ZIF-based metal-organic framework (ZIF-11 framework). The process of washing the ZIF-11 precursor with methanol was repeated 3 times. Afterward, the washed ZIF-11 was heat-treated at 950°C for 2 hours in an argon (Ar) atmosphere to form a carbon body (ZIF-11 carbon body, average particle size).

[0126] The above carbon body and KOH were mixed in a weight ratio of 1:3, and heat-treated at 800°C for 2 hours to form a ZIF-11-based carbon porous body.

[0127] A silicon-carbon composite was prepared by injecting monosilane gas at a rate of 50 sccm for 2 hours into 4 g of the above ZIF-11 carbonized at 425℃, thereby depositing silicon onto the carbonized ZIF-11.

[0128]

[0129] Example 2 and Comparative Examples 1, 2 and 4 to 7

[0130] A silicon-carbon composite was prepared in the same manner as in Example 1, except that the weight ratio of carbon body to KOH, the temperature of step (S4), and the time of step (S4) were changed as shown in Table 1 below.

[0131]

[0132] Comparative Example 3

[0133] A silicon-carbon composite was prepared in the same manner as in Example 1, except that the carbon body in step (S2) was a carbon porous body and step (S3) was not performed.

[0134]

[0135] Weight ratio of carbon body to KOH (S4) Temperature of step (°C) Time of step (Time) Example 11:34252 Example 21:44252.5 Comparative Example 11:14252 Comparative Example 21:54252 Comparative Example 3:4252 Comparative Example 41:53502 Comparative Example 51:56002 Comparative Example 61:54251 Comparative Example 71:54254

[0136] Experimental Example 1: Observation of SEM image of cathode active material

[0137] The appearance of the carbon porous bodies prepared in the examples and comparative examples was observed using a scanning electron microscope (SEM) at an acceleration voltage of 5 kV at a magnification of 10,000, and the SEM image observed in Example 1 is shown in Fig. 1.

[0138] Referring to Figure 1, it was confirmed that the carbon porous body prepared in Example 1 had an overall uniform skeletal structure and a uniform particle size of 3 μm to 7 μm.

[0139]

[0140] Experimental Example 2: Measurement of Specific Surface Area

[0141] For the carbon porous bodies and silicon-carbon composites prepared in the above examples and comparative examples, the specific surface area was measured using a Belsorp-Max instrument, and the results are shown in Table 2 below. In addition, the average diameter of the pores of the carbon porous bodies was measured using a Belsorp-Max instrument, and the slope of the Relative Pressure-Desorption graph plotted from the BET analysis results for the carbon porous body prepared in Example 1 is shown in Figure 2. The measurement was performed in the following steps: i) measuring the weight (w1) of a glass cell (c1) having the same volume, placing 3g of sample powder into c1, and vacuum drying at 200°C for 3 hours; ii) measuring the weight (w2) of a glass cell (c2) containing the sample powder after vacuum drying; iii) inputting the (w2-w1) value into the equipment, mounting c2 into the equipment, and measuring BET while partially immersing c2 in a vessel containing liquid nitrogen; iv) when N2 is supplied to the glass cell, N2 is adsorbed onto the surface of the sample powder (anode active material), and P / P0 increases from 0 to 1; v) when P / P0 reaches 1, N2 desorption begins, and P / P0 decreases from 1 to 0; vi) when P / P0 becomes 0, the measurement is completed.

[0142] Referring to Fig. 2, it can be seen that the carbon porous body prepared in Example 1 has an average pore diameter of about 1.67 nm.

[0143]

[0144] Specific surface area (m 2 / g) Carbon porous silicon-carbon composite Example 114501.9 Example 218501.1 Comparative Example 17202.1 Comparative Example 22310243 Comparative Example 33901.1 Comparative Example 423102100 Comparative Example 523104.8 Comparative Example 623101350 Comparative Example 723102

[0145] As shown in Table 2 above, the carbon porous bodies prepared in Examples 1 and 2 are 1000 m 2 / g or more than 2000 m 2 It showed a specific surface area of ​​less than / g, and 1.0 m after silicon deposition. 2 / g or more than 2.0 m 2 It was observed that silicon was efficiently deposited, as it had a very low specific surface area of ​​less than 1 / g. In contrast, it was confirmed that the carbon porous material prepared in Comparative Example 3, which did not perform step (S3), had a significantly lower specific surface area, and from the Examples and Comparative Examples 1, 2, and 4 to 7, it was confirmed that the specific surface area of ​​the carbon porous material varied depending on the mixing ratio of step (S3). Furthermore, the silicon-carbon composites prepared in Examples 1 and 2 according to the present invention had a BET specific surface area of ​​1.0 m² 2 / g or more than 2.0 m 2 It was confirmed that it was less than / g, and the silicon-carbon composites prepared in Comparative Examples 1 to 7 had a BET specific surface area of ​​1.0 m² 2 Less than / g or 2.0 m 2 It was confirmed that it exceeded / g.

[0146]

[0147] Experimental Example 3: Evaluation of Life Characteristics

[0148] A cathode slurry was prepared by mixing the silicon-carbon composite, PAM binder, and super C conductive material of the above examples and comparative examples in a weight ratio of 8:1:1. The cathode slurry was coated onto a copper foil with a thickness of 30 μm with a uniform thickness using a blade-type coating machine, a Matisse coater. The cathode was prepared by drying at 80°C.

[0149] An electrode assembly was manufactured by using the above-mentioned negative electrode as a working electrode and lithium metal as a counter electrode, interposing a porous polyethylene separator between the negative electrode and the counter electrode, and then placing the electrode assembly inside a case and injecting an electrolyte into the case to manufacture a secondary battery half cell. At this time, the electrolyte was prepared by dissolving a small amount of lithium salt (LiPF6), vinylene carbonate (VC), and propylene sulfite (PS) in a solvent mixed with ethylene carbonate (EC) and ethyl methyl carbonate (EMC).

[0150] For the secondary battery manufactured as described above, the formation process was carried out by discharging at room temperature in CC / CV mode at 0.1C until it reached 5mV, continuing to discharge the current until it reached 0.005C, and charging it to 1.5V with a constant current of 0.1C.

[0151] To verify the degradation of electrode performance due to repeated charging and discharging, the C-rate was changed to 0.5C, the cut-off current during discharge was changed to 0.02C, and the charging voltage was changed to 1.0V. While repeating charging and discharging under the above conditions, the change in capacity according to the charge-discharge cycle was verified.

[0152] As a result, it was confirmed that the silicon-carbon composite manufactured according to the present invention and the lithium secondary battery using it exhibited excellent capacity retention rate, with slow capacity reduction.

[0153] Discharge Capacity (mAh / g) Efficiency (%) Capacity Retention Rate (%) Example 1 16 108 9.7 89.7 Example 2 19 80 90.2 90.2 Comparative Example 1 9 50 88.1 88.1 Comparative Example 2 18 38 80.5 80.5 Comparative Example 3 5 50 64.4 20.1 Comparative Example 4 2 50 25.4 12.1 Comparative Example 5 15 20 77.8 70.5 Comparative Example 6 9 80 61.5 60.5 Comparative Example 7 2 350 89.5 75.8

Claims

1. Carbon porous body; and It includes silicon deposited within the pores of the above-mentioned carbon porous body, and The above-mentioned carbon porous body is a carbide of a ZIF-based metal-organic framework, and The BET specific surface area of ​​the above-mentioned carbon porous body is 1000 m² 2 / g or more than 2000 m 2 Silicon-carbon composite having a g or less.

2. In Paragraph 1, In a scanning electron microscope (SEM) image taken at a magnification of 10,000 times, the average particle size (D) of the carbon porous body 50 A silicon-carbon composite having a thickness of 1 µm or more and 10 µm or less.

3. In Paragraph 1, A silicon-carbon composite having an average pore diameter of 2.0 nm or less as measured by BET analysis of the carbon porous body.

4. In Paragraph 1, A silicon-carbon composite in which the silicon is one or more selected from the group consisting of monosilane, disilane, dichlorosilane, monochlorosilane, and trichlorosilane.

5. In Paragraph 1, BET specific surface area is 1.0 m 2 / g or more than 2.0 m 2 Silicon-carbon composite having a g or less.

6. (S1) Step of forming a ZIF-based metal-organic framework; (S2) A step of forming a carbon body by heat-treating the above ZIF-based metal-organic framework at a temperature of 350 ℃ to 1100 ℃; (S3) A step of forming a carbon porous body by mixing the carbon body with one or more selected from the group consisting of KOH, NaOH, ZnCl2, H3PO4, and K2CO3 in a weight ratio greater than 1:1 and less than 5, and heat-treating at a temperature of 600 ℃ to 900 ℃; and (S4) A step of depositing silicon on the above-mentioned carbon porous body for 1.5 to 2.5 hours; comprising, A method for manufacturing a silicon-carbon composite, wherein the above step (S4) is carried out at a temperature of 380 ℃ to 500 ℃.

7. In Paragraph 6, A method for preparing a silicon-carbon composite in which the ZIF-based metal-organic framework is formed by stirring zinc ions and an imidazole-based ligand in step (S1) above.

8. In Paragraph 7, A method for preparing a silicon-carbon composite in which the molar ratio of the zinc ion to the imidazole-based ligand is 1:1 to 3.

9. In Paragraph 6, The above (S2) step is a method for manufacturing a silicon-carbon composite, wherein the step is carried out in an argon atmosphere.

10. In Paragraph 6, A method for manufacturing a silicon-carbon composite, wherein the above (S2) step is carried out for 1 hour to 5 hours.

11. In Paragraph 6, A method for manufacturing a silicon-carbon composite, wherein the heat treatment temperature in the above (S2) step is 800 ℃ to 1000 ℃.

12. A cathode comprising a silicon-carbon composite according to any one of claims 1 to 5.

13. A lithium secondary battery comprising a negative electrode according to paragraph 12.

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