Carbon-silicon-silicon / carbon composite, manufacturing method therefor, and negative electrode active material and all-solid-state battery including same

Abstract

The present invention relates to a carbon-silicon-silicon / carbon composite comprising: a carbon-silicon composite including silicon disposed inside pores of a porous carbon support; and a silicon / carbon composite matrix disposed on the surface of the carbon-silicon composite, and a manufacturing method therefor. According to the present invention, the overall silicon size can be suppressed to be small, and the formation of Crystal-LixSiy (for example, Li15Si4 or Li3.75Si), which is an intermediate phase affecting the deterioration of battery performance, is suppressed, thereby mitigating the deterioration of battery performance during repeated charge–discharge cycles.

Description

Carbon-silicon-silicon / carbon composite, method for producing the same, negative active material and all-solid-state battery containing the same

[0001] The present invention relates to a carbon-silicon-silicon / carbon composite, and more particularly, to a carbon-silicon-silicon / carbon composite, a method for producing the same, an anode active material comprising the same, and an all-solid-state battery.

[0002] Carbon materials are materials made of carbon, one of the most abundant resources on Earth. Carbon materials are extremely lightweight, strong, and possess excellent electrical and thermal conductivity, making them a key material widely used in fields such as hydrogen vehicles, aviation, secondary batteries, and high-end consumer goods.

[0003] Carbon materials can be manufactured from various raw materials such as palm shell, polyacrylonitrile, rayon, and pitch. Among these, it is difficult to control the molecular weight and composition of carbon materials manufactured from solid raw materials such as palm shell (Republic of Korea Patent Application Publication No. 10-2019-0093960).

[0004] On the other hand, pitch, a viscoelastic solid polymer extracted from crude oil or plants, has the advantages of high yield when converted into carbon materials, low cost of raw materials, and its molecular structure is closer to the graphite structure than other raw materials, which can reduce the energy required for heat treatment (U.S. Patent Nos. 4,242,196 and 4,340,464).

[0005] In particular, pyrolysis fuel oil (PFO), naphtha cracking bottom oil (NCB), vacuum residue (VR), and fluid catalytic cracking decant oil (FCC-DO), which are obtained as by-products in the petroleum refining process, have a high content of aromatic compounds and a low content of impurities such as sulfur and nitrogen, and therefore pitch manufactured from them is attracting attention as a material for carbon materials.

[0006] Meanwhile, attempts are being made to use silicon-based anode active materials to improve the capacity of secondary batteries. Silicon, with its theoretically very high energy density, is attracting attention as a next-generation battery anode material to replace graphite. However, its volume increases by up to 300% during charge and discharge, leading to fragmentation of the silicon anode active material and severely reduced mechanical stability.

[0007] Accordingly, research has been conducted to solve these problems, but in the case of conventional negative active materials, there was a problem in that problems such as fragmentation due to volume expansion and decreased electrochemical performance were not sufficiently resolved.

[0008] [Prior Art Literature]

[0009] [Patent Document]

[0010] (Patent Document 0001) Republic of Korea Patent Application Publication No. 10-2019-0093960

[0011] (Patent Document 0002) U.S. Patent No. 4,242,196

[0012] (Patent Document 0003) U.S. Patent No. 4,340,464

[0013] The purpose of the present invention is to provide a carbon-silicon-silicon / carbon composite having a silicon-carbon composite matrix in which silicon carbide and silicon are mixed on the surface of a carbon-silicon composite in which silicon is formed inside the pores of a porous carbon support.

[0014] Another object of the present invention is to provide a method for producing the carbon-silicon-silicon / carbon composite.

[0015] Another object of the present invention is to provide a negative electrode active material comprising the carbon-silicon-silicon / carbon composite.

[0016] To solve the above-described problem, the present invention provides a carbon-silicon-silicon / carbon composite including a porous carbon support and silicon disposed within the pores of the porous carbon support, and a silicon / carbon composite matrix disposed on the surface of the carbon-silicon composite and in which silicon carbide and silicon are mixed.

[0017] According to one embodiment of the present invention, the pore volume of the carbon-silicon composite may be 5 to 50% of the pore volume of the porous carbon support.

[0018] Additionally, the pore volume of the carbon-silicon-silicon / carbon composite may be 0.5 to 50% of the pore volume of the porous carbon support.

[0019] Additionally, the silicon / carbon composite matrix may be 10 to 90 wt% of the total weight of the carbon-silicon-silicon / carbon composite.

[0020] Additionally, the carbon-silicon-silicon / carbon composite may contain 20 to 70 wt% of silicon among the total weight.

[0021] Additionally, the carbon-silicon-silicon / carbon composite may have a c / a peak ratio of 0 to 1.5.

[0022]

[0023] In addition, the present invention provides a method for producing a carbon-silicon-silicon / carbon composite, comprising the steps of forming silicon inside pores of a porous carbon support to produce a carbon-silicon composite, and forming a silicon / carbon composite matrix in which silicon carbide and silicon are mixed on the surface of the carbon-silicon composite.

[0024] According to one embodiment of the present invention, the step of manufacturing the carbon-silicon composite can be performed by applying a silicon source to the porous carbon support through chemical vapor deposition (CVD).

[0025] Additionally, the step of forming the silicon / carbon composite matrix can be performed by simultaneously chemical vapor depositing a silicon source and a carbon source onto the carbon-silicon composite.

[0026] Additionally, in the step of forming the silicon / carbon composite matrix, the silicon source and the carbon source may have a gas flow rate ratio of 1:0.05 to 1.9.

[0027]

[0028] In addition, the present invention provides a negative electrode active material comprising the above-described carbon-silicon-silicon / carbon composite.

[0029]

[0030] In addition, the present invention provides an all-solid-state battery including a solid electrolyte interphase (SEI) film including the above-described carbon-silicon-silicon / carbon composite.

[0031] The carbon-silicon-silicon / carbon composite according to the present invention comprises a carbon-silicon composite including silicon disposed inside the pores of a porous carbon support, and a silicon / carbon composite matrix disposed on the surface of the carbon-silicon composite, thereby suppressing the overall silicon size to be small and reducing the intermediate phase Crystal-Li that affects battery performance deterioration. x Si y (For example, Li 15 Si4 or Li 3.75 By suppressing the formation of Si), the deterioration of battery performance during repeated charge and discharge can be alleviated.

[0032] In addition, the manufacturing method according to the embodiment of the present invention can easily manufacture a carbon-silicon-silicon / carbon composite having the above characteristics.

[0033] FIG. 1 is a schematic diagram for manufacturing a carbon-silicon-silicon / carbon composite according to one embodiment of the present invention.

[0034] FIG. 2 is an SEM image of a carbon-silicon-silicon / carbon composite according to Examples 1 to 4 of the present invention.

[0035] Figure 3 is a graph showing the electrochemical evaluation results (charge / discharge efficiency, ICE) of Examples 1 to 4 and Comparative Example 2 of the present invention.

[0036] Figure 4 is a dQ / dV measurement graph of Examples 1 to 3 and Comparative Example 1 of the present invention.

[0037] The present invention is not limited to the contents disclosed below, and may be modified in various forms as long as the gist of the invention is not changed.

[0038] As used herein, the term “comprising” means that other components may be included unless otherwise stated.

[0039] All numbers and expressions indicating the amounts of components, reaction conditions, etc. described in this specification are to be understood as being modified in all cases by the term “about” unless otherwise stated.

[0040] The present invention will be described in more detail below.

[0041] carbon-silicon-silicon / carbon composite

[0042] According to one embodiment of the present invention, a carbon-silicon-silicon / carbon composite is provided, which comprises a porous carbon support, a carbon-silicon composite comprising silicon disposed within pores of the porous carbon support, and a silicon / carbon composite matrix disposed on a surface of the carbon-silicon composite, wherein silicon carbide and silicon are mixed.

[0043] At this time, each term of carbon-silicon-silicon / carbon composite can have the following meanings.

[0044] * Carbon: refers to the carbon of the porous carbon support.

[0045] * Silicon: refers to silicon placed inside the pores of a porous carbon support.

[0046] * Silicon / Carbon: refers to a silicon / carbon composite matrix disposed on the carbon-silicon composite and in which “Si within SiCx and / or SixCy” is located.

[0047] Meanwhile, the carbon-silicon-silicon / carbon composite may have a BET surface area of ​​200 m2 / g or less, preferably 100 m2 / g or less, and more preferably 50 m2 / g or less. If the BET surface area of ​​the carbon-silicon-silicon / carbon composite exceeds 200 m2 / g, a large number of SEI layers may be formed due to the reaction with the electrolyte due to the high BET, resulting in poor electrochemical performance.

[0048] Hereinafter, each component of a carbon-silicon-silicon / carbon composite according to one embodiment of the present invention is described.

[0049] porous carbon support

[0050] A carbon-silicon-silicon / carbon composite according to an embodiment of the present invention comprises a porous carbon support.

[0051] The porous carbon support may have a volume ratio of micropores having a pore size of 2 nm or less based on the total pore volume of 50 to 90%, preferably 60 to 80%. If the volume ratio of the micropores of the porous carbon support is less than 50%, the thickness of the silicon deposited inside may be thick, which may accelerate the deterioration of the material due to the volume expansion stress of the silicon during charge and discharge. In addition, if the volume ratio of the micropores exceeds 90%, many closed pores may be formed inside when the silicon is deposited.

[0052] In addition, the porous carbon support may have a BET specific surface area of ​​500 to 2,500 m2 / g, and preferably a BET specific surface area of ​​1,300 to 1,950 m2 / g. When the BET specific surface area of ​​the porous carbon support is less than 500 m2 / g, there may be too many macropores and thus a lack of effective pores, and when the BET specific surface area of ​​the porous carbon support exceeds 2,500 m2 / g, there may be too many micropores and thus many closed pores may be formed inside during silicon deposition.

[0053] In addition, the porous carbon support may have a tap density of 0.2 to 0.6 g / ml, and preferably, a tap density of 0.3 to 0.5 g / ml. When the tap density of the porous carbon support is less than 0.2 g / ml, process control may be difficult during silicon formation in the porous carbon support, resulting in a decrease in yield. When the tap density of the porous carbon support exceeds 0.6 g / ml, uniform silicon formation may be difficult during silicon formation in the porous carbon support.

[0054] And, the porous carbon support may have an average particle size of 1 to 20 μm. Preferably, the porous carbon support may have an average particle size of 3 to 20 μm, more preferably, an average particle size of 3 to 10 μm. If the average particle size of the porous carbon support does not satisfy the above range, the silicon formed on the surface of the porous carbon support may increase, and the silicon may not be formed at the desired level inside the pores.

[0055] Since the carbon-silicon-silicon / carbon composite according to an embodiment of the present invention includes a porous carbon support having the above characteristics, when such a carbon-silicon-silicon / carbon composite is used as an anode active material, it can be advantageous in terms of excellent electrical conductivity and alleviating stress due to volume expansion of silicon.

[0056]

[0057] carbon-silicon composites

[0058] A carbon-silicon-silicon / carbon composite according to an embodiment of the present invention comprises a carbon-silicon composite including silicon disposed within the pores of the porous carbon support.

[0059] In a specific example of the present invention, as described below, a silicon source is applied to the porous carbon support by chemical vapor deposition (CVD), thereby disposing silicon inside the pores of the porous carbon support, thereby obtaining a carbon-silicon composite.

[0060] At this time, the silicon is disposed inside the pores of the porous carbon support, and may also be disposed on at least a portion of the surface of the porous carbon support.

[0061] Meanwhile, the silicon may be crystalline or amorphous, and preferably amorphous or a similar phase. If the silicon is crystalline, the smaller the crystallite size, the denser the carbon-silicon composite can be obtained, thereby improving the initial efficiency and cycle life characteristics of the secondary battery.

[0062] In a specific embodiment of the present invention, the silicon arranged within the pores of the porous carbon support may be crystalline silicon, and at this time, the size of the silicon crystals may be on the nanoscale. Specifically, the average crystal size of the crystalline silicon may be 10 nm or less, and preferably, 8 nm or less, 5 nm or less, 3 nm or less, or 2 nm or less. When the average crystal size of the crystalline silicon satisfies the above range, the size of the stress due to the volume expansion of the silicon is reduced, and thus the life characteristics of the negative electrode active material may be improved.

[0063] The above silicon may be in the form of a thin film, and the average layer thickness of the silicon may be 10 nm to 5 μm. If the average layer thickness of the silicon is less than 10 nm, the electric capacity may be reduced, and if the average thickness exceeds 5 μm, the problem caused by volume expansion of the silicon may not be resolved, which may cause structural damage to the negative electrode material and deteriorate the cycle characteristics.

[0064] Meanwhile, the pore volume of the carbon-silicon composite may be 5 to 50%, and preferably 7 to 45%, of the pore volume of the porous carbon support. If the pore volume of the carbon-silicon composite is less than 5% of the pore volume of the porous carbon support, silicon may be formed in most of the pores and the silicon / carbon composite matrix, which may result in a deterioration of the life characteristics due to silicon volume expansion during charge and discharge. If it exceeds 50%, the electrochemical performance may decrease as less silicon may be arranged inside the pores of the porous carbon support.

[0065] The above silicon may further include a silicon oxide compound. The silicon oxide compound has the general formula SiO x It can be expressed as (0.5≤x≤2). Here, when the value of x is less than 0.5, expansion and contraction may increase and the life characteristics may deteriorate during charging and discharging of the secondary battery, and when x exceeds 2, the initial efficiency of the secondary battery may decrease as the amount of inactive oxide increases.

[0066] The content of the silicon oxide compound in the silicon may be 50 wt% or less based on the total weight of the silicon. If the content of the silicon oxide compound in the silicon exceeds 50 wt%, the initial efficiency of the secondary battery may be reduced.

[0067]

[0068] silicon / carbon composite matrix

[0069] A carbon-silicon-silicon / carbon composite according to an embodiment of the present invention comprises a silicon / carbon composite matrix in which silicon carbide and silicon are mixed and disposed on the surface of the carbon-silicon composite.

[0070] As the silicon / carbon composite matrix is ​​arranged on the surface of the carbon-silicon composite, contact between silicon and electrolyte in the carbon-silicon composite can be prevented when applied to a battery, thereby alleviating deterioration in battery performance during repeated charge and discharge cycles.

[0071] The above silicon / carbon composite matrix is ​​a mixture of silicon carbide and silicon, and may mean a continuous phase in which a silicon portion formed by Si-Si bonding and a silicon carbide portion formed by Si-C bonding are mixed.

[0072] In a specific example of the present invention, as described below, a silicon source and a carbon source can be simultaneously chemical vapor deposited (CVD) on the carbon-silicon composite to obtain a carbon-silicon-silicon / carbon composite.

[0073] Meanwhile, the silicon may be crystalline or amorphous, and preferably amorphous or a similar phase. If the silicon is crystalline, the smaller the crystallite size, the less stress caused by volume expansion, and the volume expansion is suppressed by silicon carbide, thereby improving the cycle life characteristics of the secondary battery.

[0074] Meanwhile, the pore volume of the carbon-silicon-silicon / carbon composite may be 0.5 to 50%, preferably 1 to 45%, of the pore volume of the porous carbon support. If the pore volume of the carbon-silicon-silicon / carbon composite is less than 0.5% of the pore volume of the porous carbon support, there may be a problem of including a thick coating layer in the silicon / carbon composite matrix, and if it exceeds 50%, there may be a problem of reduced initial charge / discharge efficiency due to a large surface area where electrolyte side reactions may occur.

[0075] In addition, the silicon / carbon composite matrix may be 10 to 90 wt% of the total weight of the carbon-silicon-silicon / carbon composite, and preferably 15 to 85 wt%. If the silicon / carbon composite matrix is ​​less than 10 wt% of the total weight of the carbon-silicon-silicon / carbon composite, the electric capacity may be reduced, and if it exceeds 90 wt%, the problem caused by volume expansion of silicon during charge and discharge may not be solved, which may cause structural damage to the negative electrode material and deteriorate the cycle characteristics.

[0076] The silicon of the above silicon / carbon composite matrix may further include a silicon oxide compound. The silicon oxide compound has the general formula SiO x It can be expressed as (0.5≤x≤2). Here, when the value of x is less than 0.5, expansion and contraction may increase and the life characteristics may deteriorate during charging and discharging of the secondary battery, and when x exceeds 2, the initial efficiency of the secondary battery may decrease as the amount of inactive oxide increases.

[0077] The content of the silicon oxide compound in the silicon of the silicon / carbon composite matrix may be 50 wt% or less based on the total weight of silicon in the silicon / carbon composite matrix. If the content of the silicon oxide compound in the silicon of the silicon / carbon composite matrix exceeds 50 wt%, the initial efficiency of the secondary battery may be reduced.

[0078] Meanwhile, the silicon included in the silicon / carbon composite matrix may include crystalline silicon. At this time, the size of the silicon crystals may be on the nanoscale. Specifically, the average size of the silicon crystals in the silicon / carbon composite matrix may be 10 nm or less. Preferably, the average size of the silicon crystals in the silicon / carbon composite matrix may be 8 nm or less, 5 nm or less, 3 nm or less, or 1 nm or less. When the average size of the silicon crystals in the silicon / carbon composite matrix satisfies the above range, the size of the stress due to the volume expansion of silicon is reduced, so that the life characteristics of the negative electrode active material may be improved. Meanwhile, the reason why the average size of the silicon crystals satisfies the above range may be because the Si-C bond is preferred over the Si-Si bond.

[0079] Meanwhile, the carbon-silicon-silicon / carbon composite may contain 20 to 70 wt% of silicon based on the total weight, and preferably 25 to 65 wt% of silicon based on the total weight. If the carbon-silicon-silicon / carbon composite contains less than 20 wt% of silicon based on the total weight, there may be a problem of reduced electrical capacity, and if it exceeds 70 wt%, the problem caused by volume expansion of silicon during charge and discharge may not be solved, which may cause structural damage to the negative electrode material and deteriorate cycle characteristics.

[0080]

[0081] Meanwhile, the carbon-silicon-silicon / carbon composite may have a c / a peak ratio of 0 to 1.5, preferably 0 to 1.3, more preferably 0 to 1.2, even more preferably 0 to 1.18, and even more preferably 0 to 1.15. When the c / a peak ratio of the carbon-silicon-silicon / carbon composite satisfies the above range, it may be more advantageous in achieving the purpose of the present invention, such as having an effect of maintaining stable electrochemical performance during a life evaluation. At this time, the c / a peak ratio represents the peak ratio of crystal (c) and amorphous (a).

[0082]

[0083] Method for manufacturing carbon-silicon-silicon / carbon composites

[0084] A carbon-silicon-silicon / carbon composite according to one embodiment of the present invention is manufactured by a manufacturing method including a step of manufacturing a carbon-silicon composite by forming silicon inside pores of a porous carbon support, and a step of forming a silicon / carbon composite matrix in which silicon carbide and silicon are mixed on the surface of the carbon-silicon composite (see FIG. 1).

[0085] Hereinafter, in the description of the method for manufacturing the carbon-silicon-silicon / carbon composite, the same content as the description of the carbon-silicon-silicon / carbon composite described above will be omitted and described.

[0086] First, a carbon-silicon composite is manufactured by forming silicon inside the pores of a porous carbon support.

[0087] At this time, the formation of the silicon can be performed using a device (e.g., a rotary kiln) and a method (e.g., chemical vapor deposition (CVD)) known in the technical field to which the present invention pertains. Specifically, a silicon source can be supplied to a porous carbon support and CVD can be performed to form silicon within the pores of the porous carbon support, thereby forming a carbon-silicon composite.

[0088] In a specific embodiment of the present invention, the silicon source may include at least one selected from silane (SiH4), dichlorosilane (SiH2Cl2), silicon tetrafluoride (SiF4), silicon tetrachloride (SiCl4), methylsilane (CH3SiH3), and disilane (Si2H6), but is not particularly limited thereto.

[0089] Additionally, the CVD can be performed at a temperature of 300 to 600°C, and preferably at a temperature of 450 to 550°C.

[0090]

[0091] Next, a silicon / carbon composite matrix in which silicon carbide and silicon are mixed is formed on the surface of the carbon-silicon composite to manufacture a carbon-silicon-silicon / carbon composite.

[0092] At this time, the formation of the silicon / carbon composite matrix can be performed using a device (e.g., a rotary kiln) and a method (e.g., chemical vapor deposition (CVD)) known in the technical field to which the present invention pertains. Specifically, by supplying a silicon source and a carbon source to the carbon-silicon composite and performing CVD, a silicon / carbon composite matrix in which silicon carbide and silicon are mixed can be formed on the surface of the carbon-silicon composite.

[0093] Alternatively, while continuously performing chemical vapor deposition of a silicon source to form the above carbon-silicon composite, a carbon source may be supplied in the latter half to perform chemical vapor deposition while simultaneously performing CVD of the silicon source and the carbon source to form a silicon / carbon composite matrix.

[0094] In a specific embodiment of the present invention, the silicon source may include at least one selected from silane (SiH4), dichlorosilane (SiH2Cl2), silicon tetrafluoride (SiF4), silicon tetrachloride (SiCl4), methylsilane (CH3SiH3), and disilane (Si2H6), but is not particularly limited thereto.

[0095] Additionally, the carbon source may include at least one selected from the group consisting of methane, ethane, propane, butane, methanol, ethanol, propanol, propanediol, butanediol, ethylene, propylene, butylene, butadiene, cyclopentene, acetylene, benzene, toluene, xylene, ethylbenzene, naphthalene, anthracene, and dibutylhydroxytoluene, but is not particularly limited thereto.

[0096] Additionally, the CVD can be performed at a temperature of 300 to 600°C, and preferably at a temperature of 450 to 550°C.

[0097] Meanwhile, in the step of forming the silicon / carbon composite matrix, the gas flow rate ratio of the silicon source and the carbon source may be 1:0.05 to 1.9, and preferably 1:0.6 to 1.5. If the gas flow rate ratio of the silicon source and the carbon source is less than 1:0.05 (silicon exceeding 1, carbon less than 0.05), silicon carbide may be insufficient in the silicon / carbon composite matrix, which may cause deterioration due to silicon volume expansion, and if the gas flow rate ratio exceeds 1:1.9 (silicon less than 1, carbon exceeding 1.9), silicon may be insufficient, which may cause deterioration of electrochemical characteristics such as deterioration of electrical capacity or deterioration of life characteristics.

[0098]

[0099] Negative active material

[0100] According to another embodiment of the present invention, a negative active material comprising the carbon-silicon-silicon / carbon composite is provided.

[0101] The negative active material according to an embodiment of the present invention may include a carbon-silicon-silicon / carbon composite.

[0102] In addition, the negative electrode active material according to an embodiment of the present invention may additionally include a carbon-based negative electrode material, specifically a graphite-based negative electrode material, in addition to the carbon-silicon-silicon / carbon composite. For example, the negative electrode active material may be obtained by mixing the carbon-silicon-silicon / carbon composite according to an embodiment of the present invention with a carbon-based negative electrode material, for example, a graphite-based negative electrode material.

[0103] Here, the carbon-based negative electrode material may include, but is not particularly limited to, at least one selected from the group consisting of natural graphite, artificial graphite, soft carbon, hard carbon, mesocarbon, carbon fiber, carbon nanotube, pyrolytic carbon, coke, organic polymer compound sintered body, and carbon black.

[0104] The content of the carbon-based negative electrode material in the negative electrode active material according to an embodiment of the present invention may be 2 to 80 wt%, preferably 5 to 70 wt%, and more preferably 30 to 70 wt%, based on the total weight of the negative electrode active material.

[0105] The negative active material according to an embodiment of the present invention can be effectively used in manufacturing a secondary battery, specifically, a negative electrode of a lithium secondary battery and a negative electrode of an all-solid-state battery.

[0106]

[0107] All-solid-state batteries

[0108] According to another embodiment of the present invention, an all-solid-state battery is provided comprising a solid electrolyte interphase (SEI) film comprising the carbon-silicon-silicon / carbon composite.

[0109] The above-described all-solid-state battery may be an all-solid-state battery including a positive electrode, a negative electrode, and a solid electrolyte between the positive electrode and the negative electrode, and the negative electrode may include a negative electrode active material layer, and may include a SEI (Solid Electrolyte Interphase) film including the carbon-silicon-silicon / carbon composite described above on at least a portion of the negative electrode active material particles of the negative electrode active material layer.

[0110] Meanwhile, the above-described negative electrode active material particles may be carbon-based negative electrode materials, and in this case, since the content may be the same as that described in the content of the above-described negative electrode active material, the related description will be omitted.

[0111] In addition, in addition to the negative active material particles and SEI film of the above-mentioned all-solid-state battery, the negative electrode configuration, positive electrode configuration, and solid electrolyte configuration can be applied to known all-solid-state battery configurations, and thus the present invention does not specifically limit them.

[0112]

[0113] The present invention is described in more detail by the following examples. The following examples are merely illustrative of the present invention and are not intended to limit the scope of the present invention.

[0114] [Example]

[0115] <Example 1>

[0116] First, a porous carbon support having a specific surface area of ​​1,934 m2 / g, a tap density of 0.44 g / ㎖, and an average particle size of 6 μm was prepared.

[0117] Next, 15 g of this porous carbon support was loaded into a rotating CVD device, and CVD was performed for 1 hour after heating to 475°C in an inert atmosphere (N2). During this time, CVD was performed for 50 minutes out of 1 hour with a gas flow rate of SiH4300sccm, and for the remaining 10 minutes, composite CVD was performed with a gas flow rate of SiH4:C2H4=300sccm:96sccm (SiH4 was continuously supplied), thereby manufacturing a carbon-silicon composite in which silicon was formed inside the pores of the porous carbon support, and a carbon-silicon-silicon / carbon composite in which silicon carbide and silicon were mixed and a silicon / carbon composite matrix was formed on the surface of the carbon-silicon composite.

[0118]

[0119] <Example 2>

[0120] The same procedure as Example 1 was followed, but the gas flow rate of SiH4:C2H4= 300 sccm: 96 sccm for the remaining 10 minutes was changed to SiH4:C2H4= 300 sccm: 150 sccm (gas flow rate ratio of silicon source and carbon source 1: 0.5) to manufacture a carbon-silicon-silicon / carbon composite.

[0121]

[0122] <Example 3>

[0123] The same procedure as Example 1 was followed, but the gas flow rate of SiH4:C2H4= 300 sccm: 96 sccm for the remaining 10 minutes was changed to SiH4:C2H4= 300 sccm: 300 sccm (gas flow rate ratio of silicon source and carbon source 1:1) to manufacture a carbon-silicon-silicon / carbon composite.

[0124]

[0125] <Example 4>

[0126] The same procedure as Example 1 was followed, but the gas flow rate of SiH4:C2H4= 300 sccm: 96 sccm for the remaining 10 minutes was changed to SiH4:C2H4= 300 sccm: 600 sccm (gas flow rate ratio of silicon source and carbon source 1:2) to manufacture a carbon-silicon-silicon / carbon composite.

[0127]

[0128] <Comparative Example 1>

[0129] A carbon-silicon composite was manufactured by performing the same procedure as Example 1, but changing the CVD to a deposition process for 1 hour under the conditions of a SiH4 gas flow rate of 300 sccm and a temperature of 475°C.

[0130]

[0131] Comparative Example 2

[0132] A carbon-silicon composite was manufactured by performing the same procedure as Example 1, but changing the CVD to a deposition time of 50 minutes under the conditions of a SiH4 gas flow rate of 300 sccm and a temperature of 475°C.

[0133]

[0134] <Experimental Example>

[0135] (1) Scanning electron microscope (SEM) analysis

[0136] The carbon-silicon-silicon / carbon composites manufactured according to Examples 1 to 4 above were observed using a scanning electron microscope (SEM) (Fig. 2).

[0137] At this time, the particle size, specific surface area, and tap density of the carbon-silicon-silicon / carbon composites manufactured according to Examples 1 to 4 are as shown in Table 1 below. In addition, as a control group, a porous carbon support having the particle size, tap density, and average particle size as shown in Table 1 below was prepared.

[0138] Classification Particle size (㎛) Specific surface area (㎡ / g) Tap density (g / ml) Example 16.70 29.88 0.69 Example 27.08 36.39 0.70 Example 38.08 38.28 0.75 Example 47.24 60.00 0.77 Control group 619 340.44

[0139] As can be seen in Table 1 above, in the case of Examples 1 to 3, it can be confirmed that the particle size increases due to the formation of silicon and the formation of a silicon / carbon composite matrix (silicon carbide + silicon mixture).

[0140] Meanwhile, in the case of Example 4, it was confirmed that the formation of Si nanoparticles was observed as shown in Fig. 2. This can be seen as the formation of nanoparticles rather than a silicon / carbon composite matrix in which silicon carbide and silicon are mixed, as nucleation becomes more favorable as the carbon content increases (gas flow ratio). As evidence of this, it can be confirmed that the degree of particle size increase is reduced compared to Example 3.

[0141]

[0142] (2) Electrochemical evaluation

[0143] Half coin cells were manufactured using the carbon-silicon-silicon / carbon composites of Examples 1 to 4 and the carbon-silicon composite of Comparative Example 2, and then electrochemical evaluations were performed. The half coin cell manufacturing conditions are shown in Table 2, and the evaluation results are shown in Tables 3 to 4 and FIG. 3. In Table 2, AM, CM, and BM represent active material (silicon / carbon composite), conductor (Super P carbon black), and binder (styrene-butadiene rubber / carboxymethyl cellulose 5:5), respectively, and EC, EMC, DMC, FEC, VC, and PS represent ethylene carbonate, ethyl methyl carbonate, dimethyl carbonate, fluoroethylene carbonate, vinylene carbonate, and propane sultone, respectively.

[0144] Composition (AM:CM:BM) 8:1:1 Areal capacity (mAh / cm2) 1 Electrolyte 1.3 M LiPF 6 EC / EMC / DMC 3:5:2, FEC 10%, LiBF 4 0.2%, 0.5% VC, 1% PS Cut-off voltage (V) Formation: 0.005-1.5, Cycle test: 0.005-1.2 C-rate (C) Formation: 0.1-0.1, 0.01 C cut-off (CV) at 0.005 V

[0145] Sample Charge Capacity (mAh / g)Discharge Capacity (mAh / g)ICE (%)Comparative Example 2 2059173884.4Example 1 2448215287.9Example 2 22295205189.4Example 3 2188195389.3Example 4 2394206786.3

[0146] Sample discharge capacity (mAh / g) ICE (%) Cycle retention rate Comparison Example 2 173884.444.4 Example 1 215287.953.5 Example 2 205189.448.4 Example 3 195389.366.1 Example 4 206786.355.4

[0147] As confirmed from Tables 3 and 4 above and Fig. 3, Examples 1 to 4 exhibited a reversible capacity of approximately 2000 mAh / g and achieved high CE. In contrast, Example 4 exhibited low ICE, and the comparative example exhibited a significantly reduced cycle retention rate.

[0148]

[0149] (3) dq / dV measurement (c-LiSi phase related measurement)

[0150] For Examples 1 to 3 and Comparative Example 1, Formation (CC-CV) was performed under the conditions of 0.1C-0.1C, 0.005V / 0.01C cut off (CV) using the C-rate calculated based on the Si mounting amount of the cathode material, etc. Then, dQ / dV (d(Q-Qo) / dE) was derived using the collected data. In the present invention, dQ / dV was calculated and derived through the Analysis Process of EC-Lab. This is shown in Table 5 and Fig. 4.

[0151] Sample peak ratio (c / a) Comparative Example 11.785 Example 11.035 Example 21.146 Example 31.029

[0152] As a result, it was found that Examples 1 to 3 formed less c-LiSi phase compared to Comparative Example 1, and accordingly, it was expected that there would be an effect of maintaining stable electrochemical performance during the life evaluation, and this could also be confirmed in Table 4 described above.

[0153] In particular, in the case of Example 3, the lowest c-Lisi peak was detected, and accordingly, it was found that the cycle retention was the best, as shown in Table 4 described above.

[0154]

[0155] Although one embodiment of the present invention has been described above, the spirit of the present invention is not limited to the embodiment presented in this specification, and a person skilled in the art who understands the spirit of the present invention will be able to easily propose other embodiments by adding, changing, deleting, or adding components within the scope of the same spirit, but this will also be considered to fall within the spirit of the present invention.

Claims

1. A carbon-silicon composite comprising a porous carbon support and silicon arranged within the pores of the porous carbon support; and A carbon-silicon-silicon / carbon composite comprising a silicon / carbon composite matrix in which silicon carbide and silicon are mixed and disposed on the surface of the carbon-silicon composite.

2. In paragraph 1, A carbon-silicon-silicon / carbon composite wherein the pore volume of the carbon-silicon composite is 5 to 50% of the pore volume of the porous carbon support.

3. In paragraph 1, A carbon-silicon-silicon / carbon composite having a pore volume of 0.5 to 50% of the pore volume of the carbon-silicon-silicon / carbon composite relative to the pore volume of the porous carbon support.

4. In paragraph 1, The above silicon / carbon composite matrix is ​​a carbon-silicon-silicon / carbon composite in which 10 to 90 wt% of the total weight of the carbon-silicon-silicon / carbon composite is present.

5. In paragraph 1, The above carbon-silicon-silicon / carbon composite is a carbon-silicon-silicon / carbon composite containing 20 to 70 wt% of silicon out of the total weight.

6. In paragraph 1, The above carbon-silicon-silicon / carbon composite is a carbon-silicon-silicon / carbon composite having a c / a peak ratio of 0 to 1.

5.

7. A step of forming silicon inside the pores of a porous carbon support to produce a carbon-silicon composite; and A method for manufacturing a carbon-silicon-silicon / carbon composite, comprising: forming a silicon / carbon composite matrix in which silicon carbide and silicon are mixed on the surface of the carbon-silicon composite.

8. In paragraph 7, A method for manufacturing a carbon-silicon-silicon / carbon composite, wherein the step of manufacturing the carbon-silicon composite is performed by chemical vapor deposition (CVD) of a silicon source onto the porous carbon support.

9. In paragraph 7, A method for manufacturing a carbon-silicon-silicon / carbon composite, wherein the step of forming the silicon / carbon composite matrix is ​​performed by simultaneously chemical vapor deposition of a silicon source and a carbon source onto the carbon-silicon composite.

10. In paragraph 7, A method for producing a carbon-silicon-silicon / carbon composite, wherein the silicon source and the carbon source have a gas flow rate ratio of 1:0.05 to 1.9 in the step of forming the silicon / carbon composite matrix.

11. A negative electrode active material comprising a carbon-silicon-silicon / carbon composite according to any one of claims 1 to 6.

12. An all-solid-state battery comprising a SEI (Solid Electrolyte Interphase) film comprising a carbon-silicon-silicon / carbon composite according to any one of claims 1 to 6.

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