Silicon-carbon composite material, method of manufacturing the same, cathode and battery

Abstract

The present invention provides a silicon-carbon composite material, a method for manufacturing the same, a cathode, and a battery, and specifically relates to the field of battery technology. The silicon-carbon composite material is composed of silicon-carbon composite material particles, and the silicon-carbon composite material particles include a C / C composite porous material and silicon nanoparticles located within the pore channels and on the surface of the C / C composite porous material. The C / C composite porous material includes a first carbon material and a second carbon material. The first carbon material is a porous carbon matrix, and the second carbon material penetrates the interior of the C / C composite porous material and penetrates the silicon-carbon composite material. The silicon-carbon composite material provided in the present invention can extend the service life of the material by improving the electronic and ion conductivity of the silicon-carbon composite material by introducing a second carbon material to manufacture a C / C composite porous material and forming a conductive network having strength and toughness between the porous carbon matrix and silicon nanoparticles, thereby preventing the silicon from losing contact with the porous carbon matrix during volume change.

Description

Technology Field

[0001] Cross-reference of related applications

[0002] The present invention claims priority to Chinese patent application No. 202311154535X, filed with the Chinese Intellectual Property Office on September 7, 2023, with the invention title "Silicon-carbon composite material, method of manufacturing the same, cathode and battery," the entire contents of said application are incorporated into the present invention by reference.

[0003] The present invention relates to the field of battery technology, and in particular, to a silicon-carbon composite material, a method for manufacturing the same, a negative electrode, and a battery. Background Technology

[0004] Over the past few years, the performance of silicon anodes has been continuously improving, and Si / C composite anode materials are facing industrialization; however, the performance of silicon anodes in various aspects needs to be further enhanced.

[0005] Silicon anodes are characterized by high specific energy, but at the same time, massive volume expansion (approximately 300%) and contraction occur during the charge-discharge process. While combining carbon and silicon materials can mitigate the volume effect of silicon during lithium burial and delithiation processes to some extent, the repeated expansion and contraction of silicon volume can easily cause silicon and carbon to detach and lose contact. On the other hand, the intrinsic electronic conductivity of silicon is only 10 -5 ~10 -3 It is relatively low at S / cm, and the lithium ion diffusion coefficient is also 10 -14 ~10 -13 cm 2 It is relatively low at / s. Therefore, it leads to structural and morphological degradation of silicon-carbon composite materials and an increase in internal resistance of the battery, which can result in practical problems such as a decrease in battery energy density, a drop in voltage-power, and overheating of the battery.

[0006] Based on this, the present invention was proposed. The problem to be solved

[0007] The objective of the present invention is to provide a silicon-carbon composite material, which solves the problem of deterioration in structural stability and electrochemical performance of silicon-carbon composite materials caused by the loss of contact between silicon and carbon due to the repeated expansion and contraction of silicon materials in the prior art.

[0008] Another objective of the present invention is to provide a method for manufacturing a silicon-carbon composite material.

[0009] Another objective of the present invention is to provide a cathode.

[0010] Another objective of the present invention is to provide a battery. means of solving the problem

[0011] To realize the aforementioned objectives of the present invention, the following technical measures were applied.

[0012] In a first aspect of the present invention, a silicon-carbon composite material composed of silicon-carbon composite material particles may be provided. The silicon-carbon composite material particles may include a C / C composite porous material and silicon nanoparticles located within the pore channels and on the surface of the C / C composite porous material. The C / C composite porous material may include a first carbon material and a second carbon material. The first carbon material is a porous carbon matrix, and the second carbon material penetrates the interior of the C / C composite porous material and may penetrate the silicon-carbon composite material. The second carbon material may have a size exceeding 100 nm in at least one dimension.

[0013] Furthermore, the proportion of the second carbon material in the C / C composite porous material is 0.01 to 10 wt.%, and the second carbon material may include at least one of carbon nanotubes, graphene, carbon black, and carbon fibers.

[0014] Furthermore, the size of the second carbon material in the first dimension may be L, and 100 nm <L<100μm를 만족하며, 상기 제2 탄소재료의 제2 차원에서의 크기는 a일 수 있고, 0<a<20nm를 만족할 수 있다.

[0015] Furthermore, the above L is 100 nm <L<20μm를 만족하고, 상기 a는 0<a<10nm를 만족할 수 있다.

[0016] Furthermore, the compacted specific surface area of ​​the silicon-carbon composite material may be 1 to 20 times, preferably 1 to 10 times, and more preferably 1 to 5 times the specific surface area of ​​the silicon-carbon composite material.

[0017] Furthermore, the pore volume of the above C / C composite porous material is 0.2 to 3.0 cm 3 It can be / g, where the proportion of the volume occupied by micropores can exceed 50%.

[0018] Furthermore, the pore volume of the above C / C composite porous material is 0.4 to 1.5 cm 3 It can be / g, where the proportion of the volume occupied by micropores can exceed 70%.

[0019] Furthermore, the diameter of the silicon nanoparticles may be 0.5 to 5 nm, and furthermore, the content of silicon elements in the silicon-carbon composite material may be 5 to 80 wt.%.

[0020] Furthermore, the silicon-carbon composite particle may further include a heteroatom X located within the pore channel of the C / C composite porous material, and the heteroatom X may include at least one of B, N, P, O, and S, and the heteroatom X and the silicon atom among the silicon nanoparticles may form a Si-X chemical bond to separate and encapsulate the silicon nanoparticles.

[0021] Furthermore, the heteroatom content of the silicon-carbon composite material may be 0 to 10 wt.%.

[0022] Furthermore, the surface of the silicon-carbon composite particle may have a coating layer. Preferably, the material of the coating layer on the surface is one or more selected from solid electrolytes, electroconductive polymers, carbonaceous materials, metals, alloys, metal oxides, metal halides, metal sulfides, metal phosphates, borates, sulfates, nitrates, and multi-metal oxysalts.

[0023] Furthermore, the surface of the silicon-carbon composite particle may include a mesh-structured coating layer, and preferably, the material of the coating layer may be at least one of carbon nanotubes, graphene, carbon black, or carbon fibers.

[0024] Furthermore, the specific surface area of ​​the above silicon-carbon composite material is 0.1 to 50 m 2 / g, and pore volume is 0.01–0.5cm 3 It can be / g.

[0025] Furthermore, the specific surface area of ​​the above silicon-carbon composite material is 0.1 to 10 m 2 / g, and pore volume is 0.01–0.1cm 3 It can be / g.

[0026] Furthermore, the true density of the above silicon-carbon composite material is 1.3 to 2.0 g / cm³ 3 and the occlusive stomata volume is 0.01–0.25 cm 3 It can be / g.

[0027] According to a second aspect of the present invention, a method for manufacturing a silicon-carbon composite material is provided, comprising the following steps S1 and S2. Step S1 is a step of providing a C / C composite porous material, wherein the C / C composite porous material comprises a first carbon material and a second carbon material, wherein the first carbon material is a porous carbon matrix, and the second carbon material penetrates the interior of the C / C composite porous material and penetrates the silicon-carbon composite material. Step S2 is a step of obtaining the silicon-carbon composite material by contacting a silicon-containing precursor with the C / C composite porous material and performing chemical vapor deposition so that silicon nanoparticles are distributed inside the pore channels and on the surface of the C / C composite porous material. Here, the C / C composite porous material, the first carbon material, the second carbon material, and the silicon nanoparticles each have the same meaning as in the first aspect described above.

[0028] Furthermore, the method for manufacturing the above C / C composite porous material may introduce a second carbon material in at least one process of different manufacturing processes, including a carbon precursor process, a carbon precursor pre-stabilization process, a carbonizing process, a further pore-forming process, and a finished carbon material process, during the manufacturing process of the porous carbon material.

[0029] Preferably, a first carbon material precursor and a second carbon material can be mixed and the mixture can be sintered in an inert atmosphere or a mixed atmosphere of an inert gas and an oxygen-containing gas to obtain a C / C composite porous material. Alternatively, a first carbon material precursor can be sintered under an inert atmosphere to obtain a first carbon material, and then a mixture of the first carbon material and the second carbon material can be sintered to obtain a C / C composite porous material. Here, the first carbon material precursor may include at least one of a polymer precursor, a biomass precursor, and a fossil carbon source.

[0030] Furthermore, when contacting the silicon-containing precursor with the C / C composite porous material during step S2, a heteroatom-containing precursor may be introduced. Preferably, the contact method between the silicon-containing precursor, the heteroatom-containing precursor, and the C / C composite porous material may include (1) the silicon-containing precursor and the heteroatom-containing precursor alternately contacting the C / C composite porous material, or (2) the silicon-containing precursor and the heteroatom-containing precursor simultaneously contacting the C / C composite porous material, or (3) the silicon-containing precursor and the silicon-containing precursor and the heteroatom-containing precursor alternately contacting the C / C composite porous material, or the silicon-containing precursor continuously contacting the C / C composite porous material and the heteroatom-containing precursor intermittently contacting the C / C composite porous material. Here, the contact temperature at which the silicon-containing precursor and the heteroatom-containing precursor come into contact with the C / C composite porous material may be 150°C to 1000°C, and the contact time may be 1 to 100h.

[0031] The silicon-containing precursor may include at least one of monosilane, disilane, trisilane, halosilane, polysilane, silole and derivatives thereof, and silafluorene and derivatives thereof.

[0032] Furthermore, the above heteroatom-containing precursor may include at least one of a nitrogen-containing precursor, a phosphorus-containing precursor, a sulfur-containing precursor, or a boron-containing precursor.

[0033] According to a third aspect of the present invention, a cathode comprising a silicon-carbon composite material provided in the first aspect or a silicon-carbon composite material obtained according to a manufacturing method provided in the second aspect may be provided.

[0034] According to a fourth aspect of the present invention, a battery comprising a positive electrode, a negative electrode, an electrolyte, and a separator may be provided. The negative electrode may comprise a silicon-carbon composite material provided in a first aspect or a silicon-carbon composite material obtained according to a manufacturing method provided in a second aspect. Effects of the invention

[0035] Compared to existing technology, the present application has the following beneficial effects:

[0036] The silicon-carbon composite material provided in the present invention can improve the electronic and ion conductivity of the silicon-carbon composite material by introducing a second carbon material to manufacture a C / C composite porous material and forming a conductive network having strength and toughness between the porous carbon matrix and silicon nanoparticles, thereby preventing the silicon from losing contact with the porous carbon matrix during volume change. The second carbon material is a reinforced and toughened material that forms a flexible constraining network against silicon expansion while simultaneously ensuring structural stability under low SOC conditions and improving the cycle stability and structural stability of the silicon-carbon composite material.

[0037] In the method for manufacturing a silicon-carbon composite material provided in the present invention, the first carbon material precursor loses low-molecular-weight organic matter during the sintering, pore formation, and activation processes, and generates the release of small molecules such as CO2 and H2O to form a porous carbon matrix. At the same time, the second carbon material undergoes almost no weight loss or pore formation during the sintering and pore formation processes and maintains its original size and structure. Consequently, the second carbon material forms a composite structure that penetrates into the C / C composite porous material. When silicon is deposited inside the pore channels of the C / C composite porous material, the second carbon material forms a composite structure that penetrates into the silicon-carbon composite material. Thus, the silicon-carbon composite material manufactured can exhibit the same beneficial effects as the silicon-carbon composite material. Brief explanation of the drawing

[0038] To more clearly explain the technical method for one embodiment of the present disclosure, the drawings to be used in describing the embodiment are briefly introduced below. Since the drawings below represent only some embodiments of the present invention, they should not be construed as a limitation on the scope, and those skilled in the art should understand that other related drawings can be obtained based on these drawings without creative labor. Figure 1 is an SEM image of the silicon-carbon composite material obtained in Example 6. Specific details for implementing the invention

[0039] Embodiments of the present invention will be described in detail according to the examples below. Those skilled in the art will understand that the following examples are used only to illustrate the invention and should not be construed as limiting the scope of the invention. Where specific conditions are not indicated in the examples, they may be carried out according to existing conditions or conditions recommended by the manufacturer. Where the manufacturer is not indicated on the reagents or equipment used, they are all existing products available on the market.

[0040] The endpoints and arbitrary values ​​of the ranges disclosed in the present invention are not limited to exact ranges or values, and it should be understood that such ranges or values ​​include values ​​close to such ranges or values. In the case of numerical ranges, one or more new numerical ranges may be obtained through combination between the endpoint values ​​of each range, between the endpoint values ​​of each range and individual values, and between each individual value, and such numerical ranges should be considered as specifically disclosed herein.

[0041] In a first aspect of the present invention, a silicon-carbon composite material composed of silicon-carbon composite material particles is provided. The silicon-carbon composite material particles comprise a C / C composite porous material and silicon nanoparticles located within the pore channels and on the surface of the C / C composite porous material. The C / C composite porous material comprises a first carbon material and a second carbon material. The first carbon material is a porous carbon matrix, and the second carbon material penetrates the interior of the C / C composite porous material and penetrates the silicon-carbon composite material. The second carbon material has a size of at least 100 nm in one dimension.

[0042] The silicon-carbon composite material provided in the present invention can improve the electronic and ionic conductivity of the silicon-carbon composite material by introducing a second carbon material to manufacture a C / C composite porous material and forming a conductive network with strength and toughness between the porous carbon matrix and silicon nanoparticles, thereby preventing the silicon from losing contact with the porous carbon matrix during volume change. The second carbon material serves as a strength and toughness reinforcing material, forming a flexible limiting network against silicon expansion while simultaneously ensuring structural stability under low SOC conditions, and can improve the cycle stability and structural stability of the silicon-carbon composite material.

[0043] The action of the second carbon material in silicon-carbon composite particles is as follows: ① Under low SOC conditions, the second carbon material forms conductive whiskers in the composite material. These conductive whiskers connect the silicon nanoparticles with the porous carbon matrix to form conductive pathways, thereby preventing the separation of the silicon nanoparticles and the porous carbon matrix caused by the shrinkage of the silicon nanoparticles under low load conditions. This further enhances conductivity, which can lower the DCIR resistance of the battery system containing the composite material. ② It can improve magnification performance by establishing transmission pathways. ③ The second carbon material and the first carbon material are combined to form an elastic lattice, which can increase the compressive strength of the material.

[0044] In some embodiments, the proportion of the second carbon material in the C / C composite porous material is 0.01 to 10 wt.%, and the second carbon material may include at least one of carbon nanotubes, graphene, carbon black, and carbon fibers. If the proportion of the second carbon material in the C / C composite porous material exceeds 10 wt.%, it may affect the uniformity of the pore distribution in the C / C composite porous material and further affect the uniformity of silicon nanoparticles in the silicon-carbon composite material, which may lead to a degradation of material performance. Additionally, since the cost of the second carbon material is relatively high, excessive addition may increase the cost. The proportion of the second carbon material in the above C / C composite porous material may be 0.01%, 0.1 wt.%, 0.5 wt.%, 1 wt.%, 3 wt.%, 5 wt.%, 7 wt.%, 9 wt.%, or 10 wt.%, or a range value between any two values, but is not limited thereto.

[0045] Furthermore, the size of the second carbon material in the first dimension may be L, and 100 nm <L<100μm를 만족하며, 상기 제2 탄소재료의 제2 차원에서의 크기는 a일 수 있고, 0<a<20nm를 만족한다. 더 나아가, 상기 L은 100nm<L<20μm를 만족하고, 상기 a는 0<a<10nm를 만족할 수 있다. 제2 탄소재료는 3 차원 공간내에서, 제1 차원 방향에서의 크기가 L이고, 제2 차원 방향에서의 크기가 a인 것을 만족할 수 있다. 일부 구체적인 실시 양태에서, 제2 탄소재료는 예를 들어, L이 길이이고, a가 직경인 탄소나노튜브(CNT)일 수 있고, 또 예를 들어, L이 평면의 길이 또는 폭이고, a가 시트 두께인 그래핀일 수 있다. 제2 탄소재료의 제2 차원에서의 크기a가 작을 수록, 유연성이 더 좋고, 강도가 더 높으며, 형성되는 C / C복합재료가 더 높은 안정성을 구비하게 되며, 나아가 실리콘-탄소 복합재료도 더 높은 안정성을 구비하여 실리콘의 팽창에 대한 구속력이 더 강할 수 있다.

[0046] In some embodiments, since the material possesses relatively strong mechanical strength and structural stability, it can withstand pressure better without fracture; therefore, the ratio of the compacted specific surface area of ​​the silicon-carbon composite is smaller than the specific surface area of ​​the silicon-carbon composite. The compacted specific surface area is such that the silicon-carbon composite is 4000 kgf / cm² 2 It is the specific surface area of ​​the material after compaction under pressure. Compacted specific surface area of ​​the above silicon-carbon composite material (the above silicon-carbon composite material is 4000 kgf / cm² 2 The specific surface area of ​​the material after compaction under pressure may be 1 to 20 times, preferably 1 to 10 times, and more preferably 1 to 5 times the specific surface area of ​​the silicon-carbon composite material.

[0047] In some embodiments, the pore volume of the C / C composite porous material is 0.2 to 3.0 cm 3 It may be / g, where the proportion occupied by the volume of micropores may exceed 50%. Preferably, in some embodiments, the pore volume of the C / C composite porous material is 0.4 to 1.5 cm³ 3 It can be / g, where the proportion of the volume occupied by micropores can exceed 70%.

[0048] In some embodiments, the diameter of the silicon nanoparticles may be 0.5 to 5 nm, and preferably, in some embodiments, the content of silicon element in the silicon-carbon composite material may be 5 to 80 wt.% (e.g., 5 wt.%, 10 wt.%, 20 wt.%, 30 wt.%, 40 wt.%, 50 wt.%, 60 wt.%, 70 wt.%, or 80 wt.%, or a range value between any two values).

[0049] In some embodiments, the silicon-carbon composite particles further comprise a heteroatom X located within the pore channels of the C / C composite porous material, wherein the heteroatom X comprises at least one of B, N, P, O, and S, and the heteroatom X and the silicon atoms in the silicon nanoparticles can form Si-X chemical bonds to separate and encapsulate the silicon nanoparticles. Preferably, in some embodiments, the heteroatom content in the silicon-carbon composite material may be 0 to 10 wt.%.

[0050] In some embodiments, the surface of the silicon-carbon composite particle may have a coating layer. Preferably, in some embodiments, the material of the coating layer on the surface is one or more selected from solid electrolytes, conductive polymers, carbonaceous materials, metals, alloys, metal oxides, metal halides, metal sulfides, metal phosphates, borates, sulfates, nitrates, and polymetal oxychlorides.

[0051] More preferably, in some embodiments, the carbonaceous material may include carbon nanotubes, graphene, carbon black, or carbon fibers, but is not limited thereto. In some embodiments, the organic polymer may include polyethylene oxide, polyethylene glycol, phenolic resin, epoxy resin, or polysaccharide, but is not limited thereto.

[0052] In some embodiments, the coating layer is lithium hydroxide, lithium carbonate, lithium fluoride, lithium phosphate, lithium metaphosphate, aluminum dihydrogen phosphate, lithium metaaluminate, lithium aluminum phosphate, aluminum phosphate, aluminum metaphosphate, aluminum oxide, aluminum oxide monohydrate, aluminum oxide trihydrate, aluminum hydroxide, alumina sol, aluminum isopropoxide, magnesium oxide, magnesium hydroxide, zinc oxide, zinc hydroxide, titanium oxide, zirconium oxide, LiPON (lithium nitrogen phosphate), LLZO (lithium lanthanum zirconium oxide), LATP (lithium aluminum titanium phosphate), LLTO (lithium lanthanum titanium oxide), and lithium germanium It may include one or more of the following, but is not limited thereto. In some embodiments, the coating layer may include one or more of the following: a polymer such as polyethylene oxide, carboxymethylcellulose, polyacrylic acid, or polyacrylonitrile, and lithium complexes thereof, but is not limited thereto. In some embodiments, the coating layer may include one or more of the following: a lisicon-type solid electrolyte, a nasicion-type solid electrolyte, a perovskite-type solid electrolyte, a garnet-type solid electrolyte, and a sulfide-type solid electrolyte, but is not limited thereto. In some embodiments, the coating layer may include one or more of the following: a metal phosphate, a borate, a sulfate, a nitrate, and a polymetal oxyphosphate, but is not limited thereto.

[0053] In some embodiments, the surface of the silicon-carbon composite particles may include a lattice-shaped coating layer, and preferably, the material of the coating layer may be at least one of carbon nanotubes, graphene, carbon black, or carbon fibers. The carbon material forms a lattice-shaped coating structure on the surface of the composite material, thereby confining the volume expansion of the silicon nanoparticles within the material. The lattice-shaped coating formed by the carbon material constitutes a conductive channel, which can significantly reduce the resistivity of the composite material, stabilize the interface, stabilize the SEI film, and reduce lithium ion consumption.

[0054] In some embodiments, the specific surface area of ​​the silicon-carbon composite material is 0.1 to 50 m² 2 / g, and pore volume is 0.01–0.5cm 3 It may be / g. Preferably, in some embodiments, the specific surface area of ​​the silicon-carbon composite material is 0.1 to 10 m² 2 / g, and pore volume is 0.01–0.1cm 3 It can be / g.

[0055] In some embodiments, the true density of the silicon-carbon composite material is 1.3 to 2.0 g / cm³ 3 and the occlusive stomata volume is 0.01–0.25 cm 3 It can be / g.

[0056] According to a second aspect of the present invention, a method for manufacturing a silicon-carbon composite material comprising steps S1 and S2 can be provided. Step S1 is a step of providing a C / C composite porous material, wherein the C / C composite porous material comprises a first carbon material and a second carbon material, wherein the first carbon material is a porous carbon matrix, and the second carbon material penetrates the interior of the C / C composite porous material and penetrates the silicon-carbon composite material. Step S2 is a step of obtaining the silicon-carbon composite material by contacting a silicon-containing precursor with the C / C composite porous material and performing chemical vapor deposition so that silicon nanoparticles are distributed inside the pore channels and on the surface of the C / C composite porous material. Here, the C / C composite porous material, the first carbon material, the second carbon material, and the silicon nanoparticles each have the same meaning as in the first aspect described above.

[0057] In the method for manufacturing a silicon-carbon composite material provided in the present invention, the first carbon material precursor loses low-molecular-weight organic matter during the sintering, pore formation, and activation processes, and generates the release of small molecules such as CO2 and H2O to form a porous carbon matrix. At the same time, the second carbon material undergoes almost no weight loss or pore formation during the sintering and pore formation processes and maintains its original size and structure. Consequently, the second carbon material forms a composite structure that penetrates into the C / C composite porous material. When silicon is deposited inside the pore channels of the C / C composite porous material, the second carbon material forms a composite structure that penetrates into the silicon-carbon composite material. Thus, the silicon-carbon composite material manufactured can exhibit the same beneficial effects as the silicon-carbon composite material.

[0058] In some embodiments, a method for manufacturing a C / C composite porous material may introduce a second carbon material in at least one process of different manufacturing processes, including a carbon precursor process, a carbon precursor pre-stabilization process, a carbonization process, an additional pore formation process, and a finished carbon material process, during the manufacturing process of a porous carbon material.

[0059] Preferably, in some embodiments, a first carbon material precursor and a second carbon material are mixed, and the mixture is sintered in an inert atmosphere or a mixed atmosphere of an inert gas and an oxygen-containing gas to obtain a C / C composite porous material.

[0060] In some other embodiments, the method for manufacturing the C / C composite porous material may include sintering a first carbon material precursor under an inert atmosphere to obtain a first carbon material, and then sintering a mixture of the first carbon material and a second carbon material to obtain a C / C composite porous material.

[0061] In some embodiments, during the manufacturing process of a C / C composite porous material, a pore-forming agent may be added together with a first carbon material precursor to form a porous carbon matrix having a rich pore structure after sintering. The pore-forming agent may be one or more selected from sodium dodecyl benzene sulfonate, hexadecyl trimethylammonium bromide, polyethylene glycol, polyvinyl alcohol, polyvinylpyrrolidone, oleic acid, oleylamine, polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer (e.g., P123, F127 and / or F108), citric acid, malic acid, succinic acid, NH4HCO3, (NH4)2CO3, HNO3, H2SO4, LiOH, NaOH, and KOH.

[0062] In some embodiments, the first carbon material precursor may include at least one of a polymer precursor, a biomass precursor, and a fossil carbon source. For example, the first carbon material precursor may be one or more of glucose, sucrose, maltose, lactose, cyclodextrin, starch, glycogen, cellulose, hemicellulose, lignin, epoxy resin, thermoplastic phenolic resin, thermosetting phenolic resin, polyoxymethylene resin, urea formaldehyde resin, furfural resin, furfural acetone resin, acrylic resin, coconut shell, rice husk, and wood, but is not limited thereto.

[0063] In some embodiments, the step of manufacturing the C / C composite porous material may further include the step of activating the obtained C / C composite porous material to form pores. Specifically, the C / C composite porous material is brought into contact with an oxygen-containing material. The oxygen-containing material may include, but is not limited to, gases such as H2O, CO2, and O2; solids such as KOH, NaOH, K2CO3, Na2CO3, potassium acetate, and sodium acetate and aqueous solutions thereof; and H3PO4 or aqueous solutions thereof. The contact method may include gas-solid contact, solid-solid contact, and solid-liquid contact. The temperature of the above contact may be 300 to 1200°C (e.g., 300°C, 400°C, 500°C, 600°C, 700°C, 800°C, 900°C, 1000°C, 1100°C, or 1200°C, or a temperature between any two temperatures), and preferably 600 to 900°C.

[0064] In some embodiments, the contact temperature between the silicon-containing precursor and the C / C composite porous material in step S2 may be 150°C to 1000°C, and the contact time may be 1 to 100h.

[0065] In some embodiments, when contacting the silicon-containing precursor with the C / C composite porous material during step S2, a heteroatom-containing precursor may be introduced. Preferably, the contact method between the silicon-containing precursor, the heteroatom-containing precursor, and the C / C composite porous material may include (1) the silicon-containing precursor and the heteroatom-containing precursor alternately contacting the C / C composite porous material, or (2) the silicon-containing precursor and the heteroatom-containing precursor simultaneously contacting the C / C composite porous material, or (3) the silicon-containing precursor and the silicon-containing precursor and the heteroatom-containing precursor alternately contacting the C / C composite porous material, or the silicon-containing precursor continuously contacting the C / C composite porous material and the heteroatom-containing precursor intermittently contacting the C / C composite porous material.

[0066] Furthermore, the contact temperature of the silicon-containing precursor and the heteroatom-containing precursor with the C / C composite porous material may be 150°C to 1000°C (e.g., 150°C, 200°C, 300°C, 400°C, 500°C, 600°C, 700°C, 800°C, 900°C, or 1000°C, or a temperature between any two temperatures), and the contact time may be 1 to 100h (e.g., 1h, 12h, 24h, 36h, 48h, 72h, 96h, or 100h, or a time between any two hours).

[0067] In some embodiments, the silicon-containing precursor may include at least one of monosilane, disilane, trisilane, halogenated silane, polysilane, silole and derivatives thereof, and silafluorene and derivatives thereof.

[0068] In some embodiments, the heteroatom-containing precursor may be one or more mixtures of a boron-containing precursor, a nitrogen-containing precursor, a phosphorus-containing precursor, an oxygen-containing precursor, and a sulfur-containing precursor, but is not limited thereto. Here, the boron-containing precursor may include B(CH3)3, the nitrogen-containing precursor may include one or more mixtures of NH3, NO, N2O, and acetonitrile, the phosphorus-containing precursor may include one or more mixtures of PH3 and POCl3, the oxygen-containing precursor may include one or more mixtures of oxygen, carbon dioxide, water vapor, methanol, ethanol, n-propanol, isopropanol, butanol, acetone, and butanol, and the sulfur-containing precursor may include one or more mixtures of H2S and SO2.

[0069] According to a third aspect of the present invention, a cathode comprising a silicon-carbon composite material provided in the first aspect or a silicon-carbon composite material obtained according to a manufacturing method provided in the second aspect may be provided.

[0070] According to a fourth aspect of the present invention, a battery comprising a positive electrode, a negative electrode, an electrolyte, and a separator can be provided. The negative electrode may comprise a silicon-carbon composite material provided in the first aspect or a silicon-carbon composite material obtained according to a manufacturing method provided in the second aspect. By applying the silicon-carbon composite material, the energy density of the battery can be effectively improved and internal resistance reduced, thereby having a wide range of application prospects.

[0071] The present invention will be further explained through the specific examples and comparative examples below. However, these examples should be understood merely as providing a more detailed explanation and should not be understood as limiting the present invention in any form. Where specific conditions regarding the raw materials used in the examples and comparative examples of the present invention are not specified, they may be carried out according to existing conditions or conditions recommended by the manufacturer. If the manufacturer is not indicated on the reagents or equipment used, they are all existing products available on the market.

[0072] Example 1

[0073] The present embodiment provides a silicon-carbon composite material, and the manufacturing method is as follows.

[0074] (1) Sucrose and single-walled carbon nanotubes (DAZHAN Nano (Guangdong) Co., Ltd., outer diameter range 1.6±0.4 nm, length 5 μm) were mixed in a mass ratio of 100 / 0.01. The resulting mixture was heated from room temperature to 800°C at a rate of 2°C / min in an N2 atmosphere and maintained at that temperature for 2 hours. After grinding and classifying the resulting material, it was mixed with KOH in a ratio of m(KOH):m(C) = 1:2 and activated at 800°C for 2 hours to obtain a C / C composite porous material. Here, the proportion of carbon nanotubes in the porous composite framework is 0.1 wt.%. The pore volume of the C / C composite porous material is 0.80 cm³ 3 / g, and the proportion of the micropore volume to the pore volume is 85%.

[0075] (2) A C / C composite porous material was placed in a tube furnace and heated from room temperature to 600°C at a rate of 2°C / min in an N2 atmosphere, then changed to a 20% SiH4-N2 mixed gas and maintained at 600°C for 30 hours in a 20% SiH4-N2 mixed atmosphere. After changing to an N2 atmosphere, it was cooled naturally, and then ground and classified to obtain a silicon-carbon composite material. Here, the silicon content of the silicon-carbon composite material is 52 wt.%.

[0076] Example 2

[0077] The present embodiment provides a silicon-carbon composite material, and the manufacturing method is as follows.

[0078] (1) Except for the fact that the proportion of single-walled carbon nanotubes in the C / C porous composite material is 0.01 wt.%, all other raw materials and methods are the same as the corresponding steps of Example 1, so further explanation is omitted.

[0079] (2) Same as Example 1.

[0080] Example 3

[0081] The present embodiment provides a silicon-carbon composite material, and the manufacturing method is as follows.

[0082] (1) Except for the fact that the proportion of single-walled carbon nanotubes in the C / C porous composite material is 0.5 wt.%, all other raw materials and methods are the same as the corresponding steps of Example 1, so further explanation is omitted.

[0083] (2) Same as Example 1.

[0084] Example 4

[0085] The present embodiment provides a silicon-carbon composite material, and the manufacturing method is as follows.

[0086] (1) Single-walled carbon nanotubes are replaced with graphene (DONGLI New Materials (Guangdong) Co., Ltd., sheet thickness is <15 nm, and the length or width of the graphene plane is 3 to 6 μm), except that the proportion of the graphene in the porous composite framework is 2 wt.%, and all other raw materials and methods are the same as the corresponding steps of Example 1, so further explanation is omitted.

[0087] (2) Same as Example 1.

[0088] Example 5

[0089] The present embodiment provides a silicon-carbon composite material, and the manufacturing method is as follows.

[0090] (1) Same as Example 1.

[0091] (2) A C / C composite porous material was placed in a tube furnace and heated from room temperature to 600°C at a rate of 2°C / min in an N2 atmosphere, then changed to a 20% SiH4-0.002% CO2-N2 mixed gas and maintained at 600°C for 30 hours in a 20% SiH4-N2 mixed atmosphere. After changing to an N2 atmosphere, it was cooled naturally, and then ground and classified to obtain a silicon-carbon composite material.

[0092] Example 6

[0093] The present embodiment provides a silicon-carbon composite material, and the manufacturing method is as follows.

[0094] (1) Same as Example 1.

[0095] (2) Same as Example 1.

[0096] (3) Silicon-carbon composite particles were uniformly dispersed in pure water, then 0.4% of CNT (the same manufacturer and model as the single-walled carbon nanotube of Example 1) was added and uniformly stirred, and then spray-dried to obtain a CNT-coated silicon-carbon composite.

[0097] Example 7

[0098] The present embodiment provides a silicon-carbon composite material, and the manufacturing method is as follows.

[0099] (1) Same as Example 1.

[0100] (2) Same as Example 1.

[0101] (3) After uniformly dispersing silicon-carbon composite particles in pure water, 1% of the mass fraction of CNT (same manufacturer and model as the single-walled carbon nanotube of Example 1) and 3% of the mass fraction of lithium phosphate were added and uniformly stirred, then filtered and dried to obtain a silicon-carbon composite material with a fast ionic conductor coating layer. The mass ratio of CNT to lithium phosphate was 0.3:1, and the thickness of the coating layer was 6 nm.

[0102] Example 8

[0103] The present embodiment provides a silicon-carbon composite material, and the manufacturing method is as follows.

[0104] (1) Single-walled carbon nanotubes are replaced with multi-walled carbon nanotubes (Beijing Dk Nano technology Co., LTD, outer diameter 30~60 nm, inner diameter 20~50 nm, length 1~10 μm), except that the proportion of the multi-walled carbon nanotubes in the porous composite framework is 10 wt.%, and all other raw materials and methods are the same as the corresponding steps of Example 1, so further explanation is omitted.

[0105] (2) Same as Example 1.

[0106] Example 9

[0107] The present embodiment provides a silicon-carbon composite material, and the manufacturing method is as follows.

[0108] (1) Single-walled carbon nanotubes are replaced with multi-walled carbon nanotubes (Sun TULING New Materials Co., Ltd., diameter 3~15 nm, length 15~30 μm), except that the proportion of the multi-walled carbon nanotubes in the porous composite framework is 5 wt.%, and all other raw materials and methods are the same as the corresponding steps of Example 1, so further explanation is omitted.

[0109] (2) Same as Example 1.

[0110] Example 10

[0111] (1) Sucrose and single-walled carbon nanotubes (DAZHAN Nano (Guangdong) Co., Ltd., outer diameter range 1.6±0.4 nm, length 5 μm) were mixed in a mass ratio of 100 / 0.01. The resulting mixture was heated from room temperature to 800°C at a rate of 2°C / min in an N2 atmosphere and maintained at that temperature for 2 hours. After grinding and classifying the resulting material, it was mixed with KOH in a ratio of m(KOH):m(C) = 1:2 and activated at 800°C for 0.5 hours to obtain a C / C composite porous material. Here, the proportion of carbon nanotubes in the porous composite framework is 0.15 wt.%. The pore volume of the C / C composite porous material is 0.40 cm³ 3 / g, and the proportion of the micropore volume to the pore volume is 88%.

[0112] (2) A C / C composite porous material was placed in a tube furnace and heated from room temperature to 600°C at a rate of 2°C / min in an N2 atmosphere. Then, the atmosphere was changed to a 10% SiH4-N2 mixed gas and maintained at 600°C for 10 hours in a 10% SiH4-N2 mixed atmosphere. After changing to an N2 atmosphere, it was cooled naturally. After reaching room temperature, dry air was injected, and after 2 hours, the temperature was slowly raised to 200°C and maintained in an air atmosphere for 2 hours. The temperature was raised to 600°C in an N2 atmosphere and changed to 10% C2H2-N2 and maintained for 2 hours. The obtained material was ground and classified to obtain a silicon-carbon composite material. Here, the silicon content of the silicon-carbon composite material is 8 wt.%.

[0113] Example 11

[0114] (1) Sucrose and single-walled carbon nanotubes (DAZHAN Nano (Guangdong) Co., Ltd., outer diameter range 1.6±0.4 nm, length 5 μm) were mixed in a mass ratio of 100 / 0.01. The resulting mixture was heated from room temperature to 800°C at a rate of 2°C / min in an N2 atmosphere and maintained at that temperature for 2 hours. After grinding and classifying the resulting material, it was mixed with KOH in a ratio of m(KOH):m(C) = 1:2 and activated at 800°C for 5 hours to obtain a C / C composite porous material. Here, the proportion of carbon nanotubes in the porous composite framework is 0.06 wt.%. The pore volume of the C / C composite porous material is 1.50 cm³ 3 / g, and the proportion of the micropore volume to the pore volume is 86%.

[0115] (2) Except for changing the volume content of SiH4 in the SiH4-N2 mixed gas to 30% and changing the deposition time to 40 hours, all other raw materials and methods are the same as the corresponding steps of Example 1, so further explanation is omitted. Here, the silicon content of the silicon-carbon composite material is 78 wt.%.

[0116] Comparative Example 1

[0117] The present comparative example provides a silicon-carbon composite material, and the manufacturing method is as follows.

[0118] (1) Sucrose was heated from room temperature to 800°C at a rate of 2°C / min in an N2 atmosphere and maintained at that temperature for 2 hours. After grinding and classifying the obtained material, it was mixed with KOH in a ratio of m(KOH):m(C)=1:2 and activated at 800°C for 2 hours to obtain porous carbon.

[0119] (2) Porous carbon was placed in a tube furnace and heated from room temperature to 600°C at a rate of 2°C / min in an N2 atmosphere, then changed to a 20% SiH4-N2 mixed gas and maintained at 600°C for 30 hours in a 20% SiH4-N2 mixed atmosphere. After changing to an N2 atmosphere, it was cooled naturally, ground, and classified to obtain a silicon-carbon composite material.

[0120] Experimental Example 1

[0121] The physicochemical parameters of the silicon-carbon composite materials obtained in Examples 1 to 9 and Comparative Example 1 were measured.

[0122] The particle specific surface area was measured using a specific surface area analyzer.

[0123] The particle density was measured using a fully automatic density meter.

[0124] Compaction Specific Surface Area: Powder placed in a 12 mm diameter mold, 4000 kgf / cm² 2 Pressurization was applied and maintained for 30 seconds. The specific surface area measured after compaction was defined as the compacted specific surface area. A smaller ratio between the compacted specific surface area and the specific surface area indicates that the material has a stronger pressure resistance.

[0125] The obtained figures are as listed in Table 1.

[0126] Table 1. Table of Physical and Chemical Parameters of Silicon-Carbon Composites

[0127] Specific surface area (cm²) 3 / g) Compaction specific surface area (cm²) 3 / g) Compaction specific surface area / specific surface area True density (g / cm³) 3 ) Closed pore volume (cm²) 3 / g) Example 1 2.5 16.1 6.4 1.82 0.10 Example 2 2.5 28.5 11.4 1.85 0.09 Example 3 2.6 12.0 4.6 1.76 0.12 Example 4 3.1 16.8 5.4 1.79 0.11 Example 5 2.0 10.5 5.3 1.81 0.10 Example 6 1.5 6.4 4.3 1.84 0.09 Example 7 2.4 18.5 7.7 1.80 0.10 Example 8 2.6 35.2 13.5 1.65 0.15 Example 9 2.3 28.4 12.3 1.72 0.13 Example 10 2.5 4.8 1.9 1.68 0.14 Example 11 2.2 8.9 4.0 1.70 0.14 Comparative Example 1 2.3 92 40.0 1.85 0.09

[0128] As can be seen in Table 1, Examples 1 to 11 have a lower compaction specific surface area to specific surface area ratio than the Comparative Example, implying that the silicon-carbon composite material obtained by performing silicon chemical vapor deposition using a C / C composite material with a second carbon material added as a matrix possesses higher pressure resistance, and electrodes prepared with the materials of the examples will exhibit higher cycle stability. Here, the improvement in the pressure resistance of the material is more pronounced due to single-walled carbon nanotubes and graphene having smaller sizes in the second dimension; for example, the ratio of compaction specific surface area to specific surface area of ​​Examples 1 to 6 is smaller than that of Examples 8 and 9, and accordingly, the electrochemical performance is also slightly lower. Example 5 underwent CO2 passivation treatment compared to Example 1, and due to its relatively weak oxidizing properties, some of the silicon nanoparticles [are] SiOx material (0 <x<1)과 같은 산소 함유 물질에 둘러싸이므로 복합재료는 보다 높은 내압강도를 보였다. 실시예 6은 실시예 1의 기초상에서 CNT 피복을 실시하여 복합재료의 내압강도를 더욱 향상시켰다. 실시예 7은 실시예 1의 기초상에서 인산리튬 피복, 즉 CNT와 인산리튬의 복합 피복을 추가하였다. 실시예 8 및 9는 단일벽 CNT 대신 직경이 비교적 큰 다중벽 탄소나노튜브를 이용하여 피복하였는데, 다중벽 탄소나노튜브의 튜브 직경은 비교적 굵어, 유연성이 대폭 저하되어, 복합재료 중에 적절한 전도성 네트워크를 형성하기 위해서는 비교적 많은 첨가량이 필요하며, 이 경우 재료의 다짐밀도가 저하되고, 나아가 전기화학적 안정성에 영향을 주게 된다.Examples 10 and 11 represent cases where the silicon content is relatively low and relatively high, respectively. In the case where the silicon content is relatively low, the required pore volume of the C / C composite porous material matrix is ​​relatively small; therefore, since the CNT content in the C / C composite porous material obtained with the same proportion of CNT added to the precursor is relatively large, the CNT content in the final silicon-carbon composite material is also relatively large, and the material has the minimum compaction specific surface area; in other words, the compressive strength of the composite material is the highest. The porous carbon matrix of Comparative Example 1 does not contain the second carbon material, and the obtained silicon-carbon composite material has a compressive strength of 4000 kgf / cm. 2 The specific surface area after compaction under pressure is 92 m² 2 As it increases to / g, it can be confirmed that the internal pressure strength of the composite material is very low, which will significantly affect the cycle stability in lithium-ion batteries.

[0129] Experimental Example 2

[0130] The silicon-carbon composite material provided in Example 6 was observed using a field emission scanning electron microscope, and the acquired SEM image is shown in Fig. 1. As can be seen in Fig. 1, CNTs were coated on the outer surface of the particles to form an intersecting conductive network. In the case of Examples 1 to 5, it is difficult to directly observe the presence of the second carbon material in the SEM image. The reason for this is that the second carbon material, such as CNTs or graphene, has a size of 10 nm or less or 3 nm or less in the diameter or thickness direction, is closely connected to the first carbon material in the C / C composite porous material, and is generally located inside the composite material, making it difficult to observe the second carbon material on the surface of the composite material.

[0131] Experimental Example 3

[0132] The powder resistivity of the silicon-carbon composite materials obtained in Examples 1 to 9 and Comparative Example 1 was tested at a pressure of 20 MPa using an ST2722-SZ type 4-probe powder resistivity tester produced by Suzhou Grid Electronics Co., Ltd., and the obtained values ​​are shown in Table 2.

[0133] Experimental Example 4

[0134] Negative electrode plates were prepared using the silicon-carbon composite materials obtained in Examples 1 to 9 and Comparative Example 1 as negative electrode active materials, respectively, and CR2032 type buckle-type batteries were manufactured using conventional methods, and the electrical characteristics of the batteries were tested. The specific test methods are as follows:

[0135] (1) Half-battery assembly: A CR2032 buckle-type battery was assembled in a glove box, a metal lithium sheet was used as the counter electrode, a polypropylene microporous membrane was used as the separator, and the electrolyte used was a mixture of ethyl carbonate (EC) and diethyl carbonate (DEC) (volume ratio EC:DEC=1:1) in which LiPF6 was dissolved, where the concentration of LiPF6 is 1 mol / L.

[0136] Charge and discharge tests were performed on the battery using the LAND battery test system.

[0137] (2) Gram capacity and initial efficiency test: A CR2032 buckle-type battery was left for 6 hours, then discharged at 0.05C to 0.005V, then discharged at 0.01C to 0.005V, and then left for 5 minutes and charged at 0.05C to 1.5V. Initial lithium deintercalation capacity per gram is the gram capacity (or mass specific capacity) of the electrode material.

[0138] The obtained figures are as listed in Table 2.

[0139] Experimental Example 5

[0140] The silicon-carbon composite materials obtained in Examples 1 to 9 and Comparative Example 1 were used as negative electrode active materials, and electrode pieces containing the negative electrode active materials were manufactured into pouch-type batteries using a standard method, and electrical performance tests were performed. The pouch batteries were manufactured in a dehumidification chamber with a dew point of -45°C. Charge-discharge cycle tests of the batteries were conducted using the LANBTS battery test system. The specific method is as follows.

[0141] (1) Preparation of a positive electrode sheet: NCM811 as the positive electrode active material, SuperP as the conductive agent, PVDF as the binder, and NMP as the solvent were uniformly stirred and mixed in a mass ratio of 92:3:5:150, then uniformly coated onto a positive electrode current collector and dried at 80°C to obtain a positive electrode sheet.

[0142] (2) Preparation of a cathode sheet: A cathode active material was obtained by mixing the silicon-carbon composite material obtained in Examples 1 to 9 and Comparative Example 1 with graphene. The cathode active material, SuperP as a conductive agent, polyacrylic acid as a binder, and deionized water as a solvent were uniformly stirred and mixed in a mass ratio of 95:1:1:120, then uniformly coated onto a cathode current collector and dried at 100°C to obtain a cathode sheet.

[0143] (3) A positive electrode sheet and a negative electrode sheet were laminated in a rectangular shape and separated using a polypropylene separator to manufacture a battery cell, which was then sealed in an aluminum pouch. Afterward, an electrolyte of a corresponding capacity was injected into the aluminum pouch and vacuum sealed to obtain a pouch battery. The electrolyte was a mixture of EC and DEC of LiPF6, wherein the concentration of LiPF6 was 1 mol / L and the volume ratio of EC to DEC was 1:1.

[0144] (4) Formation and capacity grading: Formation was started for the battery after liquid injection and sealing. After being left in a 25°C constant temperature box for 12 hours, it was charged to 3.3V with a constant current of 0.02C and left for 30 minutes, then charged to 3.8V with a constant current of 0.025C and left for 10 minutes, then charged to 4.2V with a constant current of 0.33C and left for 10 minutes. After forming, the battery was vacuum-treated, the pouch was cut, and capacity grading was performed. It was charged to 4.45V with a constant current of 0.33C and left for 10 minutes, then discharged to 3V with a constant current of 1C and left for 10 minutes, and finally discharged to 3V with a constant current of 0.33C to finish the grading. The ratio of the discharge capacity to the charge capacity during the formation and grading of the pouch battery is the initial Coulomb efficiency of the battery.

[0145] (5) 25℃ Cycle Test: The battery was placed in a 25℃ constant temperature box and charged to 4.45V with a constant current of 1C, and then charged to 0.1C with a constant voltage of 4.45V. After leaving it for 10 minutes, it was discharged to 3.0V with a constant current of 1C and left for 10 minutes. The charging and discharging process described above was repeated until the discharge capacity was 80% or less of the discharge capacity of the first cycle. The number of cycles obtained at this time is the cycle life of the pouch battery. In the present invention, the capacity retention rate after 100 cycles was recorded.

[0146] (6) Scaling Performance Test: After leaving the manufactured buckle-type complete battery at room temperature for 12 hours, a constant current charge / discharge test was performed on a LAND test system. The charge / discharge cutoff voltage was 3.0 to 4.25 V. First, the battery was charged and discharged with a current of 0.25 C for 3 cycles. Then, the battery was charged and discharged with a current of 0.5 C for 3 cycles. Finally, the battery was charged and discharged with a current of 1 C for 3 cycles. The capacity retention rate was calculated as the discharge capacity at the 9th cycle / discharge capacity at the 1st cycle × 100%, and it was determined that the higher the value, the better the scaling performance.

[0147] (7) DCIR Test: After formation and grading, the battery was placed in a 25°C constant temperature box and charged to 4.45V with a constant current of 1C, and the charge capacity was recorded as Q1. After leaving it for 10 minutes, it was discharged to 3.0V with a constant current of 1C and left for 10 minutes. It was then charged continuously with a constant current of 1C until the capacity Q2 (Q2 = Q1 * 10%), i.e., the battery capacity reached 10% SOC. After leaving it for 10 minutes, the battery voltage at this time was first recorded as U0, and the battery voltage when discharged with a constant current of 5C for 18 seconds was recorded as U1. The discharge DC internal resistance (DCIR) of the battery at 10% SOC is (U0 - U1) / 5C.

[0148] The obtained figures are as listed in Table 2.

[0149] Table 2. Electrical Performance Value Table

[0150] Gram capacity (mAh / g) Initial Coulomb efficiency (%) 100-Cycle Capacity Retention Rate (%) Magnification Performance (%) Resistivity (Q-cm) DCIR(mQ) Example 1 1856 93.12 99.08 63.67 4.88 2.11 Example 2 1842 93.06 99.09 63.18 5.62 2.19 Example 3 1853 93.10 98.96 60.13 4.65 2.06 Example 4 1843 93.02 99.05 62.94 4.30 2.27 Example 5 1859 93.14 99.21 65.15 7.16 2.04 Example 6 1851 93.21 99.31 66.34 2.67 2.02 Example 7 1856 93.18 99.27 68.72 1.91 1.94 Example 8 1852 93.11 98.97 61.07 4.76 2.24 Example 9 1854 93.09 98.75 60.45 4.95 2.22 Example 10 680 93.15 99.69 71.52 1.06 1.26 Example 11 2561 93.05 98.78 60.34 8.15 2.01 Comparative Example 1 1838 92.61 95.35 53.47 12.56 2.43

[0151] As can be seen from Table 2, since the difference in silicon content between the silicon-carbon composite materials obtained in Examples 1 to 11 and Comparative Example 1 is not significant, it can be confirmed that the gram capacities are similar. Compared to Comparative Example 1, Examples 1 to 11 introduced a second carbon material to establish a conductive network within the C / C composite porous material; therefore, the resistivity and DCIR of the silicon-carbon composite material are significantly lower than those of Comparative Example 1, and at the same time, the magnification performance is significantly higher than that of Comparative Example 1, confirming that the ion conductivity of the silicon-carbon composite material has been improved. Here, since the surfaces of the silicon-carbon composite materials obtained in Examples 6 and 7 have a CNT coating layer and a composite coating layer of CNT and lithium phosphate, respectively, the optimization of their resistivity, magnification performance, and DCIR is more distinct. The second carbon material has good flexibility, which can increase the strength of the silicon-carbon composite material, enhance the structural stability of the material, and further improve cycle stability, so the initial Coulomb efficiency and 100-cycle capacity retention rate of the silicon-carbon composite material obtained in Examples 1 to 11 are both higher than those of Comparative Example 1.

[0152] Compared to Examples 8 and 9, Examples 1 to 3 use single-walled carbon nanotubes as the second carbon material. Single-walled carbon nanotubes have a higher Young's modulus than multi-walled carbon nanotubes, and at the same time, the tube diameter of the single-walled carbon nanotubes is relatively small, so they have better flexibility and higher strength. Therefore, the formed C / C composite porous material has higher stability, and thus the silicon-carbon composite material has higher stability. Consequently, the cycle stability of the composite materials of Examples 1 to 3 is superior to that of Examples 8 and 9. In Example 8, the tube diameter of the multi-walled carbon nanotubes is relatively thick, so flexibility is significantly reduced, and a relatively high amount of additive is required to form a suitable conductive network within the composite material. Consequently, many closed pores are formed within the composite material, which lowers the compaction density of the material and reduces structural stability during the cycling process.

[0153] In the case of Example 5, compared to Example 1, doping element O was introduced to separate and encapsulate silicon nanoparticles, thereby improving the conductivity and ionic conductivity of the silicon region and exhibiting higher magnification performance than Example 1.

[0154] Examples 10 and 11 represent cases with relatively low and relatively high silicon content, respectively. The composite material of Example 10 has a relatively low silicon content, so its specific capacity is relatively low, whereas its magnification performance, resistivity, and DCIR are all very low because it has a relatively high CNT content, and the material exhibited excellent cycle stability. In the case of Example 11, the specific capacity is relatively high because the silicon content is relatively high, but the cycle stability is relatively lower compared to Example 10.

[0155] Finally, each of the above embodiments is intended only to illustrate the technical methods of the present invention and is not intended to limit them. Although the present invention has been described in detail using each of the above embodiments, those skilled in the art will understand that the technical methods described in each of the above embodiments may be modified or equivalent substitutions may be made for some or all of the technical methods. Such modifications or substitutions do not cause the concept of such technical methods to deviate from the scope of the technical methods according to each embodiment of the present invention.

[0156] Industrial applicability

[0157] The method of the present invention improves the cycle stability and structural stability of silicon-carbon composite materials, which can be advantageous for realizing the industrialization of silicon-carbon composite materials.

Claims

Claim 1 A silicon-carbon composite material comprising a C / C composite porous material and silicon nanoparticles located within the pore channels and on the surface of the C / C composite porous material, wherein the C / C composite porous material comprises a first carbon material and a second carbon material, wherein the first carbon material is a porous carbon matrix, and the second carbon material penetrates the interior of the C / C composite porous material and penetrates the silicon-carbon composite material, wherein the ratio of the second carbon material to the C / C composite porous material is 0.01 to 10 wt.%, and the second carbon material has a size of at least 100 nm in at least one dimension. Claim 2 In claim 1, the silicon-carbon composite material is subject to the following conditions a to b, namely: a. the second carbon material comprises at least one of carbon nanotubes, graphene, carbon black, and carbon fibers; b. the size of the second carbon material in the first dimension is L and 100 nm <L<100μm를 만족하며, 상기 제2 탄소재료의 제2 차원에서의 크기는 a이고, 0<a<20nm를 만족함; 중 적어도 하나를 충족시키는 것을 특징으로 하는 실리콘-탄소 복합재료. Claim 3 A silicon-carbon composite material according to claim 1 or 2, characterized in that the compacted specific surface area of ​​the silicon-carbon composite material is 1 to 20 times the specific surface area of ​​the silicon-carbon composite material. Claim 4 In claim 1 or 2, the pore volume of the C / C composite porous material is 0.2 to 3.0 cm 3 A silicon-carbon composite material characterized by having a volume of / g, wherein the proportion of the volume occupied by micropores exceeds 50%. Claim 5 A silicon-carbon composite material according to claim 1 or 2, characterized in that the silicon-carbon composite material satisfies at least one of the following conditions a to b, namely, a. the diameter of the silicon nanoparticles is 0.5 to 5 nm; b. the content of silicon elements in the silicon-carbon composite material is 5 to 80 wt.%. Claim 6 A silicon-carbon composite material according to claim 1, further comprising a heteroatom X located within a pore channel of a C / C composite porous material, wherein the heteroatom X comprises at least one of B, N, P, O, and S, and the heteroatom X and the silicon atom in the silicon nanoparticle form a Si-X chemical bond to separate and surround the silicon nanoparticles; and wherein the heteroatom content in the silicon-carbon composite material is 0 to 10 wt.%. Claim 7 A silicon-carbon composite material according to claim 1, wherein the surface of the silicon-carbon composite material particles has a coating layer, and the material of the coating layer on the surface is one or more selected from solid electrolytes, conductive polymers, carbonaceous materials, metals, alloys, metal oxides, metal halides, metal sulfides, metal phosphates, borates, sulfates, nitrates, and polymetallic oxychlorides. Claim 8 A silicon-carbon composite material according to claim 7, wherein the surface of the silicon-carbon composite material particles comprises a lattice-shaped coating layer, and the material of the coating layer is at least one of carbon nanotubes, graphene, carbon black, or carbon fiber. Claim 9 In claim 1, the specific surface area of ​​the silicon-carbon composite material is 0.1 to 50 m² 2 / g, and pore volume is 0.01–0.5cm 3 / g; and / or the true density of the silicon-carbon composite material is 1.3 to 2.0 g / cm³ 3 and the occlusive stomata volume is 0.01–0.25 cm 3 Silicon-carbon composite material characterized by having / g. Claim 10 A method for manufacturing a silicon-carbon composite material according to claim 1, comprising: step S1, providing a C / C composite porous material, wherein the C / C composite porous material comprises a first carbon material and a second carbon material, wherein the first carbon material is a porous carbon matrix, and the second carbon material penetrates the interior of the C / C composite porous material and penetrates the silicon-carbon composite material; and step S2, bringing a silicon-containing precursor into contact with the C / C composite porous material and performing chemical vapor deposition so that silicon nanoparticles are distributed inside the pore channels and on the surface of the C / C composite porous material, thereby obtaining the silicon-carbon composite material; wherein the C / C composite porous material, the first carbon material, the second carbon material, and the silicon nanoparticles each have the same meaning as in claim 1. Claim 11 In claim 10, the method for manufacturing the C / C composite porous material comprises introducing a second carbon material in at least one of different manufacturing processes, including a carbon precursor process, a carbon precursor pre-stabilization process, a carbonization process, an additional pore formation process, and a finished carbon material process, mixing a first carbon material precursor and a second carbon material, and sintering the mixture in an inert atmosphere or a mixed atmosphere of an inert gas and an oxygen-containing gas to obtain a C / C composite porous material, or sintering the first carbon material precursor under an active atmosphere to obtain a first carbon material, and then sintering a mixture of the first carbon material and the second carbon material to obtain a C / C composite porous material, wherein the first carbon material precursor is at least one of a polymer precursor, a biomass precursor, and a fossil carbon source. Claim 12 In claim 10, in step S2, the contact temperature between the silicon-containing precursor and the C / C composite porous material is 150°C to 1000°C and the contact time is 1 to 100h, and / or when contacting the silicon-containing precursor and the C / C composite porous material, a heteroatom-containing precursor is introduced, wherein the contact temperature between the silicon-containing precursor and the heteroatom-containing precursor and the C / C composite porous material is 150°C to 1000°C and the contact time is 1 to 100h; and / or the silicon-containing precursor comprises at least one of monosilane, disilane, trisilane, halogenated silane, polysilane, silole and derivatives thereof, and silafluorene and derivatives thereof; A method for manufacturing a silicon-carbon composite material, characterized in that the heteroatom-containing precursor comprises at least one of a nitrogen-containing precursor, a phosphorus-containing precursor, a sulfur-containing precursor, or a boron-containing precursor. Claim 13 A cathode characterized by comprising a silicon-carbon composite material according to claim 1, or a silicon-carbon composite material obtained by the manufacturing method according to claim 10. Claim 14 A battery characterized by comprising a positive electrode, a negative electrode comprising a silicon-carbon composite material according to claim 1 or a silicon-carbon composite material obtained by a manufacturing method according to claim 10, an electrolyte, and a separator.

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