Silicon-containing composite, method for producing the same, carbon composite using the same, electrode containing the same, lithium battery, and electronic device

Abstract

To provide a silicon-containing composite, a manufacturing method therefor, a carbon composite using the same, an electrode containing the same, the lithium battery and the electronic element.SOLUTION: There is provided a silicon-containing composite 11 containing a porous core 1 containing a porous silicon secondary particle, and a shell 2 containing second graphene 10b on at least a surface of the porous core, in which the porous silicon secondary particle contains an aggregate of 2 or more silicon composite primary particles 10, the silicon composite primary particle contains silicon, silicon suboxide (SiOx) (O<x<2) on at least a surface of the silicon, and one or more containing the first graphene 10a on at least a surface of the silicon suboxide and selected from the first graphene and the second graphene contains one or more element selected from nitrogen (N), phosphorus (P) and sulfur (S).SELECTED DRAWING: Figure 1A

Description

Technical Field

[0001] The present invention relates to a silicon-containing composite, a method for producing the same, a carbon composite using the same, an electrode containing the same, a lithium battery, and an electronic device.

Background Art

[0002] Conventionally, among the negative electrode active materials for lithium-ion batteries, silicon has a very high theoretical capacity of 4,200 mAh / g and a low price, and research on its utilization as a negative electrode material has been actively carried out. By the way, when silicon is discharged, while a Li 4.4 Si alloy is formed, it is accompanied by volume expansion, generates an active material that is electrically isolated in the electrode, and has problems such as promoting an electrolyte decomposition reaction due to an increase in the specific surface area of the active material. In order to overcome this, methods have been proposed to reduce the volume expansion of silicon, develop a structure with a small pulverization phenomenon during volume expansion, or form a coating layer made of carbon or the like on the silicon surface.

[0003] By the way, when using the silicon materials developed so far, the volume expansion reduction effect and the charge and discharge efficiency of the battery could not reach a satisfactory level.

Summary of the Invention

Problems to be Solved by the Invention

[0004] The problem to be solved by the present invention is to provide a silicon-containing composite and a method for producing the same. The problem to be solved by the present invention is also to provide the above-mentioned silicon-containing composite and a carbon composite containing a carbon-based material.

[0005] The problem to be solved by the present invention is also to provide an electrode containing the above-mentioned silicon-containing composite or the carbon composite. Another problem to be solved by the present invention is to provide a lithium battery including an electrode containing the silicon-containing composite or the silicon-containing composite and a carbon composite containing a carbon-based material.

[0006] Another problem to be solved by the present invention is to provide a field emission device including the silicon-containing composite or the silicon-containing composite and a carbon composite containing a carbon-based material. Another problem to be solved by the present invention is to provide a biosensor including the silicon-containing composite or the silicon-containing composite and a carbon composite containing a carbon-based material.

[0007] A problem to be solved by the present invention is to provide a semiconductor device including the silicon-containing composite or the silicon-containing composite and a carbon composite containing a carbon-based material. Another problem to be solved by the present invention is to provide a thermoelectric device including the silicon-containing composite or the silicon-containing composite and a carbon composite containing a carbon-based material.

Means for Solving the Problems

[0008] According to one aspect, a silicon-containing composite including a porous core containing porous silicon secondary particles and a shell containing a second graphene on at least one surface of the porous core, the porous silicon secondary particles include aggregates of two or more silicon composite primary particles, the silicon composite primary particles include silicon, silicon suboxide (SiO x )(O<x<2) on at least one surface of the silicon, and a first graphene on at least one surface of the silicon suboxide, There is provided a silicon-containing composite in which one or more selected from the first graphene and the second graphene contain one or more elements selected from nitrogen (N), phosphorus (P), and sulfur (S).

[0009] The silicon suboxide exists in one or more states selected from a film and a matrix. The first graphene and the second graphene each exist in one or more states selected from a film, particles, and a matrix.

[0010] On the other hand, a step of obtaining porous silicon secondary particles from a composition containing silicon, a structure containing silicon suboxide (SiO x )(O<x<2), a dispersant, and a solvent, and a step of supplying a carbon source gas to the porous silicon secondary particles and performing heat treatment are provided, and a method for producing a silicon-containing composite is provided. A method for manufacturing a silicon-containing composite is provided, which includes supplying a carbon source gas to the porous silicon secondary particles and performing heat treatment.

[0011] On yet another aspect, the aforementioned silicon-containing composite and a carbon composite containing a carbon-based material are provided. On yet another aspect, an electrode including the aforementioned silicon-containing composite and a carbon composite containing a carbon-based material is provided.

[0012] On yet another aspect, a lithium battery including the aforementioned electrode is provided. Yet another aspect is to provide an electronic device including the silicon-containing composite and a carbon composite containing a carbon-based material. The electronic device is a field emission device, a biosensor, a semiconductor device, or a thermoelectric device.

[0013] On yet another aspect, a silicon-containing composite includes a core containing porous silicon secondary particles and a shell containing second graphene disposed on top of the core. The porous silicon secondary particles include aggregates of two or more silicon composite primary particles, and the silicon composite primary particles are silicon suboxide SiO xIt includes (0 < x < 2) and the first graphene disposed on the silicon suboxide, and one or more selected from the first graphene and the second graphene each contain one or more selected from nitrogen, phosphorus, and sulfur, and a silicon-containing composite is provided.

Advantages of the Invention

[0014] By using the silicon-containing composite according to the present invention, the formation of a network between silicon particles can reduce the expansion of the electrode plate during charge and discharge, not only improving the initial efficiency and volumetric energy density, but also improving the conductivity and the charge and discharge durability by forming a highly durable silicon protective layer.

Brief Description of the Drawings

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Figure 1A

Figure 1B

Figure 1C

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Figure 10A

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Figure 12E

Embodiments for Carrying Out the Invention

[0016] With reference to the accompanying drawings, exemplary one or more silicon-containing composites, electrodes containing an electrode active material containing the same, lithium batteries containing the same, field emission devices using the composite, biosensors, and semiconductor devices will be further described below.

[0017] A silicon-containing composite comprising a porous core containing porous silicon secondary particles and a shell containing a second graphene on at least one surface of the porous core. The porous silicon secondary particles include aggregates of two or more silicon composite primary particles. The silicon composite primary particles include silicon, silicon suboxide (SiO x )(O<x<2) on at least one surface of the silicon, and a first graphene on at least one surface of the silicon suboxide. One or more selected from the first graphene and the second graphene contain one or more elements selected from nitrogen (N), phosphorus (P), and sulfur (S), and a silicon-containing composite is provided.

[0018] The silicon-containing composite is also porous. The silicon suboxide exists in one or more states selected from a film and a matrix, and the first graphene and the second graphene each exist in one or more states selected from a film, particles, and a matrix. The term "matrix" indicates a three-dimensional space, and the term "membrane" indicates a two-dimensional space compared to the matrix.

[0019] The second graphene is also directly grown on top of the silicon suboxide of the porous silicon secondary particles. The first graphene is directly grown from the surface of the silicon suboxide, and the second graphene is directly grown from the surface of the porous silicon secondary particles.

[0020] In this specification, the term "matrix" can indicate a three-dimensional space compared to the "membrane" indicating a two-dimensional space. According to another embodiment, the matrix can indicate a case where the constituent components have a uniform composition, while the membrane has a composition gradient.

[0021] As used herein, the term "cluster" refers to an aggregate of at least one or more primary particles, and is substantially interpreted to have the same meaning as "secondary particle".

[0022] As used herein, the term "graphene" can have a structure such as a flake, nanosheet, film (or, membrane). Here, the nanosheet indicates a case where it is formed irregularly on silicon suboxide, while the membrane refers to a film form that is continuously and uniformly formed on top of silicon suboxide. In this way, graphene can also have a plurality of layers or can have a structure without layer distinction.

[0023] As used herein, the term "silicon suboxide" can have a single composition represented by SiO x (O<x<2). Alternatively, silicon suboxide can include one or more selected from, for example, Si, SiO2, and refers to a case where the average composition is represented by SiO x (O<x<2).

[0024] In one silicon-containing composite of an embodiment, the core size is 3 to 10 μm, and the shell thickness is 10 to 5,000 nm, for example, also 10 to 1,000 nm. Here, the size means the diameter or the major axis length.

[0025] Figure 1A shows a silicon-containing composite according to an embodiment. Referring to it, the silicon-containing composite 11 includes a core 1 containing porous silicon secondary particles and a shell 2 containing a second graphene 10b disposed on top of the core 1.

[0026] The porous silicon secondary particles include an aggregate of two or more silicon composite primary particles 10, and the silicon composite primary particles are silicon, silicon suboxide (SiO x)(O < x < 2), and includes a first graphene 10a disposed on silicon suboxide. In the silicon composite primary particles, the first graphene forms a shell on the silicon suboxide surface, and in the silicon composite secondary particles, the second graphene forms a shell on the upper part of the core. The silicon-containing composite has a double core / shell structure. By having such a double core / shell structure, volume expansion is suppressed and side reactions with the electrolyte are reduced.

[0027] The first graphene 10a of core 1 may have the same or different number of layers compared to the second graphene 10b of shell 2.

[0028] According to one embodiment, the second graphene 10b of shell 2 has a higher density than the first graphene 10a in core 1. According to one embodiment, the number of layers of the first graphene 10a in core 1 is 1 to 30 layers, for example, 5 to 15 layers, specifically 10 layers, and the number of layers of the second graphene 10b in the shell 2 is 1 to 50 layers, for example, 20 to 30 layers.

[0029] One or more selected from nitrogen, phosphorus, and sulfur may be doped into the first graphene 10a and the second graphene 10b.

[0030] In the surface depth of 10 nm or less determined by XPS (X-ray photoelectron spectroscopy) analysis for the silicon-containing composite, the content of one or more selected from nitrogen, phosphorus, and sulfur is 0.2 atomic % or less, for example, 0.05 to 0.2 atomic %. The surface depth is, for example, 1 to 10 nm, for example, 5 to 10 nm.

[0031] The content of one or more selected from nitrogen, phosphorus, and sulfur is 2,000 ppm or less, for example, 50 to 2,000 ppm, for example, 500 to 2,000 ppm.

[0032] FIG. 1B shows a silicon-containing composite according to another embodiment. The silicon-containing composite of FIG. 1B has a structure in which a carbon coating film 12 is further disposed on the surface of the silicon-containing composite of FIG. 1A. The carbon coating film 12 may include amorphous carbon, crystalline carbon, or a combination thereof. And, like the first graphene and the second graphene, the carbon coating film 12 may include one or more selected from nitrogen, sulfur, and phosphorus.

[0033] In a silicon-containing composite according to still another embodiment, it is also possible that one or more selected from nitrogen, phosphorus, and sulfur are not included in the first graphene and the second graphene but are included only in the carbon coating film 12.

[0034] Referring to FIG. 2, the effects when nitrogen is included in the silicon-containing composite will be described in more detail.

[0035] In the manufacturing process of graphene, some defects are generated, thereby reducing the conductivity. If such graphene is used as an electrode material, an SEI (solid electrolyte interface) layer is more easily formed. As shown in FIG. 2, when nitrogen is included, if nitrogen is introduced into the defect region of graphene, the stability and quality of graphene are further improved. Nitrogen is introduced at the positions of pyridinic N, quaternary nitrogen, and pyrrolic N, and the effect of further improving the quality of graphene can be obtained.

[0036] Also, if nitrogen is introduced into the defect sites of graphene, when such a structure is used as an electrode material, the formation of the SEI layer is effectively suppressed. According to one embodiment, there is an outer layer having a higher density than the core. Such an outer layer thickness is not limited, but is, for example, also 20 to 60 nm.

[0037] The intensity ratio (Id / Ig) of the D peak to the G peak determined by Raman analysis spectrum of the silicon-containing composite is from 0.8 to 1.5, for example, from 1 to 1.4, for example, from 1.1 to 1.3, for example, about 1.2.

[0038] The 20% weight loss temperature determined by thermogravimetric analysis of the silicon-containing composite is 7 to 15 °C higher than that of the silicon-containing composite containing no element selected from nitrogen, phosphorus and sulfur.

[0039] When the silicon-containing composite contains nitrogen, the 20% weight loss temperature is, for example, 710 to 730 °C. The core and the shell may further contain graphite.

[0040] The diameter ratio of the porous silicon secondary particles to the silicon-containing composite is from 1:1 to 1:30, for example, from 1:1 to 1:25, specifically, 1:21. The diameter ratio of the porous silicon secondary particles to the silicon-containing composite cluster indicates the size ratio when both the porous silicon secondary particles and the silicon-containing composite have a spherical shape. If the porous silicon secondary particles and the silicon-containing composite are non-spherical, it is also the ratio of the major axis lengths.

[0041] According to another embodiment, in the silicon-containing composite, the core diameter is from 3 to 10 μm, and the shell thickness is from 10 to 5,000 nm (0.01 to 5 μm), for example, from 10 to 1,000 nm. The core diameter and the shell (carbon coating film) thickness of the silicon-containing composite are from 1:0.001 to 1:1.67, for example, 1:001, 1:1.67, 1:0.0033, or 1:0.5.

[0042] In the silicon-containing composite, the total content of the first graphene and the second graphene is 0.1 to 2,000 parts by weight, for example, 0.1 to 300 parts by weight, for example, 0.1 to 90 parts by weight, specifically, 5 to 30 parts by weight, based on 100 parts by weight of silicon. When the total content of the first graphene and the second graphene is within the above range, the silicon volume suppression effect of the silicon-containing composite is excellent, and the conductivity characteristics are also excellent.

[0043] In the composite primary particles, the first graphene extends from silicon of silicon suboxide (SiO x )(O < x < 2) at a distance of 10 nm or less, for example, 1 nm or less, for example, about 0.00001 to 1 nm, and includes at least 1 to 30 graphene layers. The total thickness of the first graphene is 0.3 to 1,000 nm, for example, 0.3 to 50 nm, for example, 0.6 to 50 nm, for example, 1 to 30 nm. The first graphene is oriented at an angle of 0 to 90° with respect to the main axis of silicon. In this specification, the main axis means the Y axis.

[0044] As shown in FIG. 1C, the first graphene and the second graphene may be oriented at a 90° angle with respect to the main axis (Y axis) of the plate-like and needle-like silicon particles 10 formed on the surface of the silicon suboxide (SiO x )(0 < x < 2) film.

[0045] In the silicon-containing composite, the second graphene extends from silicon of silicon suboxide (SiO x )(O < x < 2) of the porous silicon secondary particles at a distance of 1,000 nm or less, for example, 500 nm or less, for example, 10 nm or less, for example, 5 nm or less, 1 nm or less, for example, about 0.00001 to 1 nm, and includes at least 1 to 30 graphene layers. The total thickness of the second graphene is 0.6 to 50 nm, for example, 1 to 50 nm. The second graphene is oriented at an angle of 0 to 90° with respect to the main axis of silicon.

[0046] Silicon suboxide (SiO x )(where 0 < x < 2) has a thickness of 30 μm or less, for example, 10 nm. The shape of the silicon is not limited and is, for example, one or more selected from the group consisting of sphere, nanowire, acicular, and rod-shaped. And the average particle size of the silicon is 10 nm to 30 μm, for example, 100 nm.

[0047] The average particle size (D50) of the porous silicon secondary particles is 200 nm to 50 μm, for example, 1 to 30 μm, for example, 1 to 10 μm, and specifically, 3 to 5 μm. And the specific surface area of the porous silicon secondary particles is 0.1 to 100 m 2 / g, for example, 1 to 30 m 2 / g. And the density of the porous silicon secondary particles is 0.1 to 2.8 g / cc, for example, 0.5 to 2 g / cc.

[0048] The surface of the structure of the silicon-containing composite may further include a carbon coating film containing amorphous carbon. In this way, if a carbon coating film is further formed, although the initial efficiency decreases, a lithium battery with improved life characteristics can be manufactured.

[0049] The carbon coating film may further contain one or more selected from nitrogen, phosphorus, and sulfur, similar to the first graphene and the second graphene. The method of including one or more selected from nitrogen, phosphorus, and sulfur in the carbon coating film can be applied in various ways.

[0050] The thickness of the carbon coating film is, for example, 10 to 5,000 nm. The amorphous carbon is, for example, one or more selected from the group consisting of pitch carbon, soft carbon, hard carbon, mesophase pitch carbide, fired coke, and carbon fiber.

[0051] The carbon coating film containing amorphous carbon may further contain crystalline carbon. The crystalline carbon is one or more selected from the group consisting of fullerenes, natural graphite and artificial graphite, graphene and carbon nanotubes.

[0052] The carbon coating film is a non-porous continuous coating film, and the thickness of the carbon coating film is 1 to 5,000 nm. The carbon coating film may include, for example, a first carbon coating film containing amorphous carbon and a second carbon coating film containing crystalline carbon.

[0053] The particle size distribution characteristics of the silicon-containing composite are narrow. For example, the D50 of the porous silicon cluster is 1 to 30 μm, the D10 is 0.001 to 10 μm, and the D90 is 10 to 30 μm. The porous silicon cluster can be seen as secondary particles.

[0054] Thus, the silicon-containing composite according to one embodiment has a narrow particle size distribution. In contrast, the silicon composite secondary particles obtained from the conventional silicon composite primary particles have an irregular size distribution of the secondary particles and are difficult to control as the particle size of the negative electrode active material showing optimal cell performance. In the silicon-containing composite, the oxygen content is 0.01 to 15 atomic %, for example, 3.5 to 5 atomic %, specifically, 3.5 to 3.8 atomic %. The reason why the oxygen content is less than that of the conventional silicon-based material is that the oxidation of silicon is suppressed by using a dispersant such as stearic acid during the production of the silicon-containing composite. By minimizing such an oxygen content, the silicon capacity is maximized and the initial efficiency is improved.

[0055] Regarding the conventional graphene direct-grown silicon primary particles and the state of the negative electrode after charge and discharge when using them, it is as follows. The graphene direct-grown silicon primary particles have a structure in which the first graphene is disposed on the upper part of the needle-shaped silicon particles. It is mixed with graphite, and a negative electrode active material layer in the form of a mixture is formed on the copper current collector to manufacture a negative electrode.

[0056] After charge and discharge, due to the volume expansion and contraction of silicon, the graphene directly grown silicon primary particles as the active material are detached, and due to silicon isolation, the capacity decreases. And on the surface of the silicon primary particles, an unstable SEI layer continuously grows, thereby resulting in large lithium consumption and reduced charge-discharge durability.

[0057] After many studies, in order to solve the above problems, the inventor of the present invention utilizes a silicon-containing composite having a double core / shell structure to form a uniform charge-discharge network, thereby reducing the crushing phenomenon caused by the volume expansion and contraction of silicon during charge and discharge, and forming a stable SEI on the surface of the silicon-containing composite, thereby enabling the production of a negative electrode with improved durability during charge and discharge.

[0058] Also, silicon having a size of 100 nm or more, for example, 150 nm or more, for example, 100 to 200 nm, can be used to produce a silicon-containing composite containing graphene containing nitrogen on top of silicon / silicon suboxide in one manufacturing process.

[0059] A silicon-containing composite according to an embodiment has a capacity of 600 to 2,000 mAh / cc and has very excellent capacity characteristics.

[0060] In still another aspect, a silicon-containing composite includes a core containing porous silicon secondary particles and a shell containing a second graphene disposed on top of the core, wherein the porous silicon secondary particles include aggregates of two or more silicon composite primary particles, and the silicon composite primary particles include i) SiO x (0 < x < 2), and ii) SiO x (0 < x < 2), and at least one of the first graphene and the second graphene contains at least one selected from nitrogen, phosphorus, and sulfur, and a silicon-containing composite is provided.

[0061] In this specification, "the heat treatment product of SiO x (0 < x < 2)" refers to the product obtained by performing heat treatment on SiO x (0 < x < 2). Here, the heat treatment means the heat treatment for a vapor deposition reaction for growing graphene on SiO x (0 < x < 2). During the vapor deposition reaction, as the graphene source, a carbon source gas or a gas mixture containing a carbon source gas and a reducing gas can be used. The reducing gas can be, for example, hydrogen.

[0062] SiO x (0 < x < 2) heat treatment product is also the product obtained by heat-treating SiO x (0 < x < 2) in an atmosphere of i) a carbon source gas or ii) a gas mixture containing a carbon source gas and a reducing gas.

[0063] SiO x (0 < x < 2) heat treatment product is, for example, a structure in which silicon (Si) is disposed in a silicon suboxide (SiO y )(0 < y ≤ 2) matrix.

[0064] The heat treatment product of SiO x (0 < x < 2) according to one embodiment is, for example, i) a structure in which silicon (Si) is disposed in a silicon oxide (SiO2) matrix, ii) a structure in which silicon (Si) is disposed in a matrix containing SiO2 and SiO y (0 < y < 2), or iii) a structure in which silicon (Si) is disposed in a SiO y (0 < y < 2) matrix.

[0065] Said i) SiO x (0 < x < 2), and ii) SiO xAn amorphous carbon layer may be disposed between one or more silicon oxides selected from among heat treatment products in the range of (0 < x < 2) and the first graphene. An amorphous carbon layer may be disposed between a core including porous silicon secondary particles and the second graphene. The amorphous carbon layer acts as a graphene growth nucleus and helps to favorably grow graphene on the silicon oxide and the core.

[0066] According to another embodiment, there is no carbide such as silicon carbide (SiC) between silicon and silicon suboxide and / or between silicon suboxide and graphene. If such a carbide is present, when SiC does not react with lithium and is used as an electrode material, the capacity decreases, and a high temperature is required to form graphene on SiC, the crystallinity of silicon increases, and the pulverization phenomenon is accelerated during lithium charge and discharge.

[0067] A method for manufacturing a silicon-containing composite according to an embodiment will be described with reference to FIG. 3. First, a structure including silicon and silicon suboxide (SiO x )(0 < x < 2) formed on the silicon is crushed to obtain crushed silicon primary particles.

[0068] The crushed silicon primary particles, a dispersant, and a solvent are mixed to obtain Composition 30. Porous silicon secondary particles 31 are obtained from Composition 30. In the porous composite secondary particles, the porosity is, for example, 0.1 to 50%, and the pore size is 10 to 500 nm.

[0069] The method for manufacturing porous silicon secondary particles from the above-described composition can be variously used by using a co-impregnation method, a spray drying method, a solid-phase method, etc. According to one embodiment, the spray drying method can be used. When manufacturing particles by the spray drying method, the particle diameter can be controlled by selecting the spray form, the pressurized gas supply rate, the composition supply rate, the drying temperature, etc.

[0070] During spray drying, the ambient temperature is from normal temperature (25 °C) to 500 °C, for example, it is carried out at a temperature of 50 to 300 °C. When carrying out spray drying, while preventing in advance the occurrence of problems such as particle adhesion and blockage due to moisture condensation at the outlet part of the particles, when carried out within the above temperature range, the porosity of the silicon composite secondary particles is appropriate.

[0071] During spray drying, the spray pressure of the spray drying is also 1 to 5 bar. Before spray drying, by means such as crushing the starting material, the surface area of the silicon primary particles 31 is increased as much as possible. For this purpose, the crushed silicon primary particles are used as the starting material.

[0072] For example, when using spray drying, spherical porous silicon secondary particles 31 can be obtained. On the surface of the porous silicon secondary particles 31, a dispersant such as stearic acid is partially present. During spray drying, the nozzle size is 50 to 1,000 μm, for example, 150 μm.

[0073] Thereafter, a silicon-containing composite can be manufactured, including the step of supplying a carbon source gas and one or more precursors selected from nitrogen, phosphorus, and sulfur to the porous silicon secondary particles 31 and performing heat treatment. In FIG. 3, reference numeral 10a is the first graphene, reference numeral 10b is the second graphene, reference numeral 1 is the core, reference numeral 2 is the shell, and reference numeral 20 is the silicon composite primary particle. In this way, one or more precursors selected from nitrogen, phosphorus, and sulfur can be obtained only through the process of further adding to the manufacturing process using the existing carbon source gas. Therefore, the manufacturing process of the target product is simplified and easy. The mixing ratio of one or more precursors selected from nitrogen, phosphorus, and sulfur and the carbon source gas can be controlled by controlling the volumes of these respective precursors and the carbon source gas, and can be controlled as desired.

[0074] According to an embodiment, in a carbon source and one or more precursors selected from nitrogen, phosphorus, and sulfur, the content of one or more precursors selected from nitrogen, phosphorus, and sulfur is 20% by volume or less, for example, 5 to 20% by volume, based on the total content of the reaction gas. When the content of one or more precursors selected from nitrogen, phosphorus, and sulfur is within the above range, the crystallinity and quality of graphene are excellent.

[0075] The carbon source first fills the pores of the porous silicon secondary particles and then grows outside the secondary particles.

[0076] As the solvent, ethanol, methanol, isopropyl alcohol, etc. are used. By going through the heat treatment step using such an alcohol-based solvent, the dispersant is removed along with the removal of the solvent, and the content remaining in the silicon-containing composite is minimized. As a result, a silicon-containing composite with a minimized oxygen content can be obtained.

[0077] The dispersant serves to evenly disperse the silicon primary particles. The dispersant is, as a non-limiting example, one or more selected from stearic acid, resorcinol, polyvinyl alcohol, and pitch. The content of the dispersant is 1 to 15 parts by weight, for example, 5 to 10 parts by weight, based on 100 parts by weight of the total weight of the composition. When the content of the dispersant is within the above range, silicon and graphene are evenly dispersed without being aggregated.

[0078] The carbon source is one or more selected from the group consisting of a compound represented by the following Chemical Formula 1, a compound represented by the following Chemical Formula 2, and an oxygen-containing gas represented by the following Chemical Formula 3. (Chemical Formula 1) C n H (2n+2-a) [OH] a In the above Chemical Formula 1, n is an integer from 1 to 20, and a is 0 or 1. (Chemical Formula 2) C n H (2n) In the above Chemical Formula 2, n is an integer from 2 to 6. (Chemical Formula 3) C x H y O z In the above Chemical Formula 3, x is 0 or an integer from 1 to 20, y is 0 or an integer from 1 to 20, and z is 1 or 2.

[0079] The carbon source is, for example, one or more selected from the group consisting of methane, ethylene, propylene, methanol, ethanol, and propanol.

[0080] The heat treatment is carried out at 600 to 1,100 °C, for example, 700 to 1,000 °C. When carried out at such a heat treatment temperature, graphene is formed at high density in the core and the shell.

[0081] As described above, the silicon composite primary particles include silicon, silicon suboxide (SiO x )(O<x<2) disposed on the silicon, and graphene disposed on the silicon suboxide. The silicon suboxide (SiO x )(O<x<2) is an unstable substance with oxygen deficiency compared to silica (SiO2), and has a tendency to react with other reactive substances such as a carbon source gas to form a stable substance. Utilizing such a point, the silicon suboxide (SiO x )(O<x<2) film is used as a seed layer material for forming graphene.

[0082] The silicon suboxide (SiO x )(O<x<2) formed on the silicon has a film form, and the silicon suboxide film thickness has a very important influence on the form, structure, etc. of graphene.

[0083] The silicon suboxide (SiO x)(O < x < 2) The film thickness can be varied by using the manufacturing process utilized during the formation of graphene, for example, the composition of the carbon source necessary for graphene formation. Such silicon suboxide (SiO x )(O < x < 2) The film thickness is also 300 μm or less.

[0084] According to one embodiment, the silicon suboxide (SiO x )(O < x < 2) The film thickness of the composite used in the battery is 10 nm or less, 0.1 to 10 nm, specifically 0.1 to 5 nm. By using a composite having a silicon suboxide (SiOx) (O < x < 2) film within such a thickness range, the capacity characteristics of the battery are excellent.

[0085] According to one embodiment, the process of forming graphene on the upper part of the silicon suboxide (SiO x )(O < x < 2) film utilizes a gas-phase carbon deposition reaction without using a catalyst.

[0086] The gas-phase carbon deposition reaction is carried out in a mixed gas atmosphere containing one or more selected from the group consisting of the compound represented by the following Chemical Formula 1, the compound represented by the following Chemical Formula 2, and the oxygen-containing gas represented by the following Chemical Formula 3, and one or more precursors selected from nitrogen, phosphorus, and sulfur, through a step of heat-treating silicon coated with silicon suboxide (SiO x ). (Chemical Formula 1) C n H (2n+2-a) [OH] a In the Chemical Formula 1, n is an integer of 1 to 20, and a is 0 or 1. (Chemical Formula 2) C n H (2n) In the Chemical Formula 2, n is an integer of 2 to 6. (Chemical Formula 3) C x H y O z In the formula (3), x is 0 or an integer of 1 to 20, y is 0 or an integer of 1 to 20, and z is 1 or 2.

[0087] The above-mentioned gas-phase carbon deposition reaction is not restricted by the theory described later. However, such a coating involves the reforming using CO2 or the like with respect to silicon coated with silicon suboxide (SiO x ).

[0088] According to the above-mentioned gas-phase carbon deposition reaction, graphene is directly grown on silicon coated with silicon suboxide (SiO x ), and the adhesion between silicon and graphene is high.

[0089] According to another embodiment, even if there is no SiO x layer on the upper part of the Si layer, through the process of reacting a carbon mixed gas and an oxygen mixed gas, in the reaction of the oxygen-containing mixed gas, an SiO x layer is first formed on the upper part of the silicon layer, and while the carbon mixed gas reacts thereon, graphene can be formed. The adhesion between silicon and graphene can be evaluated via an electron scanning microscope by the distance between the silicon of SiO x and graphene.

[0090] The first graphene of the silicon composite primary particles constituting the silicon-containing composite extends at a distance of 10 nm or less in silicon, for example, 0.5 to 10 nm, for example, 0.5 nm to 7.5 nm, for example, 0.5 to 5 nm. According to another embodiment, the first graphene extends at a distance of 5 nm or less in silicon, for example, 1 nm or less, for example, 0.0001 to 5 nm, for example, 0.5 to 1 nm. And the first graphene is oriented at an angle of 0 to 90° with respect to the main axis of silicon. It includes at least 1 to 20 graphene layers, and the total thickness of the first graphene is 0.6 to 12 nm. And the first graphene is oriented at an angle of 0 to 90° with respect to the Y axis of silicon.

[0091] Silicon, in its form, is non - limiting. For example, silicon can be one or more selected from spheres, nanowires, needles, rods, particles, nanotubes, nanorods, wafers, and nanoribbons.

[0092] According to one embodiment, silicon is also of the needle - like particle type. At this time, the needle - like silicon particles have a length of about 100 to 160 nm, for example, 108 to 125 nm, a thickness of about 10 to 100 nm, for example, 20 to 50 nm, and specifically, 40 nm.

[0093] According to one embodiment, a silicon sub - oxide (SiO x )(0 < x < 2) film may be formed on the needle - like silicon, and graphene may be formed on top of it.

[0094] According to another embodiment, a silicon sub - oxide (SiO x )(0 < x < 2) film may be formed on the silicon particles, and graphene may be formed on top of it. Here, the average particle size of the silicon particles is 40 nm to 40 μm, for example, 40 nm to 100 nm.

[0095] When silicon is of the wafer type, the thickness of the silicon wafer is 2 mm or less, for example, 0.001 to 2 mm.

[0096] Graphene is formed by a plurality of carbon atoms linked to each other by covalent bonds to form a polycyclic aromatic molecule. The carbon atoms linked by covalent bonds form a 6 - membered ring as the basic repeating unit, but may further contain 5 - membered rings and / or 7 - membered rings. As a result, graphene appears as a single layer of carbon atoms (usually sp 2 bonds) covalently bonded to each other. Graphene can consist of a single layer, but several of them can be stacked on top of each other to form multiple layers. For example, it can have a number of layers from 1 layer to 100 layers, or alternatively, 2 layers to 100 layers, or 3 layers to 50 layers.

[0097] Graphene can have structures such as nanosheets, membranes (or films), graphene nanosheets, flakes, etc. The term "nanosheet" refers to the case where it is formed in an irregular state on silicon suboxide, and "membrane" refers to a film form continuously and uniformly formed on top of silicon suboxide.

[0098] A silicon-containing composite according to an embodiment may further include a metal oxide. If such a metal oxide is further included, there is an advantage of preventing the formation of the SEI layer by suppressing side reactions.

[0099] The metal oxide includes one or more selected from the group consisting of magnesium oxide, manganese oxide, aluminum oxide, titanium oxide, zirconium oxide, tantalum oxide, tin oxide, hafnium oxide, and aluminum fluoride (AlF3).

[0100] In a silicon-containing composite according to an embodiment, graphene can play the role of an SEI stabilizing clamping layer. And the silicon-containing composite has a high specific surface area, and in a battery using the same, it is possible to prevent a decrease in initial efficiency and volumetric energy density.

[0101] In the silicon-containing composite, graphene can suppress the crushing and pulverization of active materials such as silicon, and can improve the conductivity of the composite. Graphene plays a role in suppressing the crushing and pulverization of particles that occur in silicon particles. Graphene plays the role of a clamping layer that prevents the disintegration of silicon particles, promotes the alloying reaction between lithium ions and Si, has an extremely excellent specific capacity, and provides a continuous conductive path between particles.

[0102] When the silicon particles expand, the graphene layers slide past each other and slide back to a relaxed position during the delithiation process. Such movement is because the van der Waals force is greater than the interlayer frictional force.

[0103] The above-mentioned clamping effect of the graphene layer can be confirmed through the fact that the graphene layer remains intact even after repeating the lithiation / delithiation cycle about 200 times, and the graphene layer serves as a clamping layer to prevent the decomposition of silicon particles.

[0104] In a silicon-containing composite according to an embodiment, dense graphene is formed on the surface of the primary particles of the silicon composite, nano-sized pores are formed between the particles, and it can play a buffering role when the volume of the primary and secondary particles expands. And through heat treatment, the SEI layer can be stably formed. And several layers of graphene present on the surface of the secondary particles prevent the primary particles from protruding outside the secondary particles due to the sliding between the graphene layers during the expansion and contraction of the silicon volume, and reduce the contact between the primary particles of the silicon composite and the electrolyte.

[0105] In another aspect, the above-mentioned silicon-containing composite and a carbon composite containing a carbon-based material are provided. The silicon-containing composite according to an embodiment has a reduced specific surface area and an increased volume density (specific capacity) compared to the primary particles of the silicon composite, and can improve the volume energy density when mixed with the carbon-based material, and further reduce the volume expansion of the electrode.

[0106] The above-mentioned carbon composite has excellent initial efficiency and specific capacity characteristics compared to the composite, and its rate-determining performance and durability are further improved.

[0107] The content of the carbon-based material is 0.001 to 99 parts by weight, for example, 10 to 97 parts by weight, for example, 50 to 97 parts by weight, based on 100 parts by weight of the carbon composite. When the content of the carbon-based material is within the above range, a carbon composite excellent in capacity and conductivity can be obtained.

[0108] The carbon-based material contains one or more selected from the group consisting of graphene, graphite, fullerene, carbon fiber, and carbon nanotube. The carbon composite may contain, for example, graphite and a silicon-containing composite formed on the graphite.

[0109] As the graphite, for example, SFG6 graphite is used, and for example, the average particle size is about 6 μm. When forming an electrode using the carbon composite, the content of the carbon composite in the electrode is, for example, 68 to 87 parts by weight, and the content of the binder is, for example, 13 to 32 parts by weight. The content of graphite in the carbon composite is, for example, 1 to 20 parts by weight based on 100 parts by weight of the carbon composite.

[0110] As the binder, for example, lithium polyacrylate is used. The compound represented by Chemical Formula 1 and the compound represented by Chemical Formula 2 are one or more selected from the group consisting of methane, ethylene, propylene, methanol, ethanol, and propanol.

[0111] The oxygen-containing gas represented by Chemical Formula 3 includes, for example, carbon dioxide (CO2) and carbon monoxide (CO), water vapor (H2O), or a mixture thereof. The nitrogen precursor can have, for example, ammonia.

[0112] The sulfur precursor is also, for example, sulfur powder, (NH4)2S04, Li2S04, CoSO4, or a combination thereof. And the phosphorus precursor is also phosphorus powder, (NH4)2HPO4, NH4H2PO4, Li3PO4, P2O5, or a combination thereof.

[0113] In addition to the carbon source, it may further contain one or more inert gases selected from the group consisting of nitrogen, helium, and argon. The oxygen-containing gas is also one or more selected from the group consisting of carbon monoxide, carbon dioxide, and water vapor.

[0114] When an oxygen-containing gas is used as the carbon source, the thickness of the silicon oxide film can be formed thicker compared to the silicon oxide film thickness of the native oxide film. For example, the thickness of the silicon oxide film can be controlled to 10 nm or less, for example, 0.5 to 5 nm. By using a silicon oxide film having such a thickness range, the morphology and thickness of graphene can be adjusted. More specifically, if the thickness of the silicon oxide film is formed thicker than that of the native oxide film within the above-mentioned thickness range, a graphene layer having a denser structure than the graphene nanosheet formed on top of it can be obtained. Here, the graphene layer has a structure of, for example, 5 to 10 layers.

[0115] When the gas mixture contains water vapor, the resulting composite can exhibit even higher conductivity. Without being bound by a specific theory, in the presence of water vapor, due to the reaction between the gas mixtures, high-crystalline carbon is deposited on silicon coated with silicon suboxide, so even when a smaller amount of carbon is coated, it is considered that high conductivity can be exhibited. The content of water vapor in the gas mixture is not limited, and for example, 0.01 to 10 vol% is used based on 100 vol% of the total carbon source.

[0116] The carbon source is, for example, methane, a mixed gas containing methane and an inert gas, an oxygen-containing gas, or a mixed gas containing methane and an oxygen-containing gas.

[0117] The carbon source according to one embodiment is also a CH4:CO2 mixed gas or a CH4:CO2:H2O mixed gas. According to one embodiment, the morphology of graphene may also vary depending on the type of carbon source.

[0118] The CH4:CO2 mixed gas is also provided at a molar ratio of about 1:0.20 to 0.50, specifically, also provided at a molar ratio of about 1:0.25 to 0.45, and more specifically, also provided at a molar ratio of about 1:0.30 to 0.40.

[0119] The CH4:CO2:H2O mixed gas is also provided at a molar ratio of about 1:0.20 to 0.50:0.01 to 1.45, specifically, also provided at a molar ratio of about 1:0.25 to 0.45:0.10 to 1.35, and more specifically, also provided at a molar ratio of about 1:0.30 to 0.40:0.50 to 1.0.

[0120] A carbon source according to another embodiment is also carbon monoxide (C0) or carbon dioxide (CO2).

[0121] A carbon source according to still another embodiment is a mixed gas of CH4 and N2. The CH4:N2 mixed gas is also provided at a molar ratio of about 1:0.20 to 0.50, specifically, also provided at a molar ratio of about 1:0.25 to 0.45, and more specifically, also provided at a molar ratio of about 1:0.30 to 0.40. A carbon source according to one embodiment does not contain an inert gas such as nitrogen.

[0122] The heat treatment is carried out at 750 to 1,100 °C, for example, also at 800 to 1,000 °C.

[0123] In the heat treatment stage, the pressure is not limited either and can be selected considering factors such as the heat treatment temperature, the composition of the gas mixture, and the amount of the desired carbon coating. The pressure during the heat treatment can be controlled by adjusting the amount of the inflowing gas mixture and the amount of the outflowing gas mixture. For example, the pressure during the heat treatment is 1 atm or more, for example, also 2 atm or more, 3 atm or more, 4 atm or more, 5 atm or more, but is not limited thereto.

[0124] The heat treatment time is not particularly limited and can be appropriately adjusted according to the heat treatment temperature, the pressure during heat treatment, the composition of the gas mixture, and the amount of the desired carbon coating. For example, the reaction time can be 10 minutes to 100 hours, specifically 30 minutes to 90 hours, and more specifically 50 minutes to 40 hours, but is not limited thereto. Without being bound by a specific theory, the longer the time, the more graphene (carbon) is deposited, whereby the electrical properties of the composite can be improved. However, such a tendency is not necessarily directly proportional to the time. For example, after a predetermined time, no further graphene deposition occurs or the deposition rate decreases.

[0125] The method for producing the silicon-containing composite described above can provide a uniform coating of graphene on silicon coated with silicon suboxide (SiO x ) even at a relatively low temperature through the gas-phase reaction of the carbon source described above. And the desorption reaction of graphene formed on silicon coated with a silicon suboxide (SiO x ) film hardly occurs. By controlling the thickness of the silicon oxide film, the desorption reaction of graphene can be further suppressed. Thus, the thickness of the silicon oxide film capable of efficiently suppressing the desorption reaction of graphene is 10 nm or less, 0.1 to 10 nm, and specifically 0.1 to 5 nm.

[0126] In addition, since graphene is coated on silicon through a gas-phase reaction, a coating film having high crystallinity can be formed. When such a silicon-containing composite is used as a negative electrode active material, the conductivity of the negative electrode active material can be increased without structural change.

[0127] During the gas-phase carbon deposition reaction for producing the silicon-containing composite according to one embodiment, it can be carried out in an atmosphere of a gas mixture containing a carbon mixed gas and a reducing gas such as hydrogen.

[0128] When the silicon composite primary particles constituting the silicon-containing composite are one or more silicon oxides selected from the heat treatment products of i) SiO x (0 < x < 2) and ii) SiO x (0 < x < 2), and include the first graphene disposed on top of the silicon oxide, the first graphene can be formed by performing heat treatment in an atmosphere of a gas mixture of a carbon source gas such as methane and hydrogen. The mixing ratio of the carbon source gas and hydrogen is, for example, 1:1 to 1:7, or for example, also a ratio of 1:1 to 1:5. The basis of this ratio is also the molar ratio or the flow rate ratio.

[0129] The manufacturing process of the carbon composite using the silicon-containing composite according to one embodiment is as follows. Mix a silicon-containing composite according to one embodiment and a carbon-based material, and heat-treat it.

[0130] The heat treatment is carried out at 600 to 1,100 °C, for example, 700 to 1,000 °C. When the heat treatment temperature is within the above range, a carbon composite with excellent capacity characteristics can be obtained.

[0131] The elemental ratio (C / Si) of silicon (Si) to carbon (C) determined by XPS (X-ray photoelectron spectroscopy) analysis of a silicon-containing composite according to one embodiment is 100 to 200, for example, 140 to 180. And the elemental ratio (C / Si) of silicon (Si) to carbon (C) determined by XPS analysis of the silicon-containing composite increases compared to the C / Si ratio of the silicon-containing composite that does not contain one or more selected from nitrogen, phosphorus, and sulfur. At this time, the increase rate increases by, for example, 300% or more, for example, 490% or more. Here, the increase in the elemental ratio (C / Si) of silicon (Si) to carbon (C) means that the coverage rate of graphene on silicon / silicon suboxide is high.

[0132] A silicon-containing composite or carbon composite according to an embodiment is also usefully used in batteries, light emitters for displays, field emission materials for displays, thermoelectric elements, biosensors, and the like.

[0133] According to still another aspect, an electrode including the aforementioned silicon-containing composite or carbon composite is provided. The electrode is also an electrode for a lithium battery. The electrode is also a negative electrode.

[0134] The silicon-containing composite or carbon composite is also used as an electrode active material, for example, as a negative electrode active material. In this way, when used as a negative electrode active material, silicon volume expansion is reduced and pulverization is reduced. And the conductivity is improved and the high-rate characteristics are improved. Also, graphene can be coated in a minimal amount on silicon coated with silicon suboxide, and a negative electrode active material with improved energy density per volume can be obtained. A lithium battery including a silicon-containing composite, or a silicon-containing composite and a carbon composite including a carbon-based material is provided.

[0135] The negative electrode is also manufactured by the following method. The negative electrode is manufactured, for example, by forming a negative electrode active material composition containing a silicon-containing composite or carbon composite, which is a negative electrode active material, a conductive agent, and a binder, into a certain shape, or by applying the aforementioned negative electrode active material composition to a current collector such as a copper foil. In the composition, the conductive agent may not be used.

[0136] Also, without a current collector, the negative electrode active material composition may be formed in film form on a separator.

[0137] Specifically, a negative electrode active material composition in which the aforementioned negative electrode active material, conductive agent, binder, and solvent are mixed is prepared. The negative electrode active material composition is directly coated on a metal current collector to manufacture a negative electrode plate. As an alternative, after the negative electrode active material composition is cast on a separate support, a film peeled off from the support is laminated on the metal current collector to manufacture a negative electrode plate. The negative electrode is not limited to the forms listed above, and may be in other forms as well.

[0138] In addition to the aforementioned negative electrode active material, the negative electrode active material composition may contain other carbon negative electrode active materials added thereto. For example, the carbon negative electrode active material is, for example, one or more selected from the group consisting of natural graphite, artificial graphite, expanded graphite, graphene, carbon black, fullerene soot, carbon nanotubes, and carbon fibers, but is not necessarily limited thereto, and any of them is possible as long as it is used in the technical field.

[0139] As the conductive agent, acetylene black, ketjen black, natural graphite, artificial graphite, carbon black, carbon fiber, metal powders such as copper, nickel, aluminum, and silver, metal fibers, etc. can be used, and conductive materials such as polyphenylene derivatives can be used by mixing one or more of them, but are not limited thereto, and any of them can be used as long as it is used as a conductive agent in the technical field.

[0140] As the binder, vinylidene fluoride / hexafluoropropylene copolymer, polyvinylidene fluoride (PVDF), polyacrylonitrile, polymethyl methacrylate, polytetrafluoroethylene, styrene-butadiene rubber-based polymer, polyacrylic acid, polyamideimide, polyimide, or a mixture thereof may also be used, but are not limited thereto, and any of them can be used as long as it is used as a binder in the technical field.

[0141] As the solvent, N-methylpyrrolidone, acetone, water, etc. are used, but it is not limited thereto, and any of them can be used as long as it is used in the relevant technical field.

[0142] The contents of the aforementioned negative electrode active material, conductive agent, binder, and solvent are at levels commonly used in lithium batteries. Depending on the use and configuration of the lithium battery, one or more of the binder and solvent may be omitted.

[0143] Furthermore, a lithium battery according to another embodiment employs the aforementioned negative electrode. The lithium battery can also be manufactured by the following method. First, a negative electrode is prepared by the aforementioned negative electrode manufacturing method.

[0144] Next, a positive electrode active material composition in which a positive electrode active material, a conductive agent, a binder, and a solvent are mixed is prepared. The positive electrode active material composition is directly coated and dried on a metal current collector to manufacture a positive electrode. As an alternative, after the positive electrode active material composition is cast on a separate support, the film peeled off from the support is laminated on a metal current collector to manufacture a positive electrode.

[0145] As the positive electrode active material, it may contain one or more selected from the group consisting of lithium cobalt oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium iron phosphate, and lithium manganese oxide, but it is not necessarily limited thereto, and all positive electrode active materials available in the relevant technical field are used.

[0146] For example, as long as the positive electrode active material is a lithium-containing metal oxide and is commonly used in the industry, any of them can be used without limitation. For example, one or more of composite oxides of metals selected from cobalt, manganese, nickel, and combinations thereof and lithium can be used. Specific examples thereof include Li a A 1-b B’ bD2 (in the above formula, 0.90 ≤ a ≤ 1 and 0 ≤ b ≤ 0.5); Li a E 1-b B’ b O 2-c D c (in the above formula, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05); LiE 2-b B’ b O 4-c D c (in the above formula, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05); Li a Ni 1-b-c Co b B’ c D α (in the above formula, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α ≤ 2); Li a Ni 1-b-c Co b B’ c O 2-α F α (in the above formula, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α < 2); Li a Ni 1-b-c Co b B’ c O 2-α F’2 (in the above formula, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α < 2); Li a Ni 1-b-c Mn b B’ c D α (in the above formula, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α ≤ 2); Li a Ni 1-b-c Mn b B’ c O 2-α F’ α (in the above formula, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α < 2); Li a Ni 1-b-c Mn b B’ c O 2-α F’2 (in the above formula, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α < 2); Li a Ni b E c Gd O2 (in the above formula, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0.001 ≤ d ≤ 0.1); Li a Ni b Co c Mn d G e O2 (in the above formula, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0 ≤ d ≤ 0.5, 0.001 ≤ e ≤ 0.1); Li a NiG b O2 (in the above formula, 0.90 ≤ a ≤ 1, 0.001 ≤ b ≤ 0.1); Li a CoG b O2 (in the above formula, 0.90 ≤ a ≤ 1, 0.001 ≤ b ≤ 0.1); Li a MnG b O2 (in the above formula, 0.90 ≤ a ≤ 1, 0.001 ≤ b ≤ 0.1); Li a Mn2G b O4 (in the above formula, 0.90 ≤ a ≤ 1, 0.001 ≤ b ≤ 0.1); QO2; QS2; LiQS2; V2O5; LiV2O5; LiI’O2; LiNiVO4; Li 3-f J2(PO4)3 (0 ≤ f ≤ 2); Li 3-f Any one of the compounds represented by the chemical formulas Fe2(PO4)3 (0 ≤ f ≤ 2); LiFePO4 can be used.

[0147] In the above chemical formulas, A is Ni, Co, Mn, or a combination thereof; B’ is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, a rare earth element, or a combination thereof; D is O, F, S, P, or a combination thereof; E is Co, Mn, or a combination thereof; F’ is F, S, P, or a combination thereof; G is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, or a combination thereof; Q is Ti, Mo, Mn, or a combination thereof; I’ is Cr, V, Fe, Sc, Y, or a combination thereof; J is V, Cr, Mn, Co, Ni, Cu, or a combination thereof.

[0148] Here, it goes without saying that those having a coating layer on the surface of the compound can also be used, or the compound and a compound having a coating layer can be mixed and used. The coating layer may contain a coating element compound such as an oxide of the coating element, a hydroxide of the coating element, an oxyhydroxide of the coating element, an oxycarbonate of the coating element, or a hydroxycarbonate of the coating element. The compounds forming those coating layers may be amorphous or crystalline. As the coating element contained in the coating layer, Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr, or a mixture thereof can be used. The coating layer formation process can use such elements in the compound and can be coated by any coating method (for example, spray coating method, dipping method, etc.) as long as it does not adversely affect the physical properties of the positive electrode active material. Since this is well-known to those skilled in the art, detailed description thereof will be omitted.

[0149] For example, LiNiO2, LiCoO2, LiMn x O 2x (x = 1, 2), LiNi 1-x Mn x O2(0 < x < 1), LiNi 1-x-y Co x Mn y O2(0 ≤ x ≤ 0.5, 0 ≤ y ≤ 0.5), LiFeO2, V2O5, TiS, MoS, etc. are used.

[0150] In the positive electrode active material composition, the conductive agent, the binder, and the solvent can be the same as those in the case of the negative electrode active material composition. On the other hand, a plasticizer can be further added to the positive electrode active material composition and / or the negative electrode active material composition to form pores inside the electrode plate.

[0151] The contents of the positive electrode active material, conductive agent, binder, and solvent are at levels commonly used in lithium batteries. Depending on the application and configuration of the lithium battery, one or more of the conductive agent, binder, and solvent may be omitted.

[0152] Next, a separator to be inserted between the positive electrode and the negative electrode is prepared. Any separator can be used as long as it is commonly used in lithium batteries. A separator with low resistance to ion movement of the electrolyte and excellent electrolyte moisture retention ability is used. For example, it is selected from among glass fiber, polyester, Teflon (registered trademark), polyethylene, polypropylene, polytetrafluoroethylene (PTFE), or combinations thereof, and may be in the form of a non-woven fabric or a woven fabric. For example, a wound separator such as polyethylene or polypropylene is used for lithium-ion batteries, and a separator with excellent impregnation ability for organic electrolytes is used for lithium-ion polymer batteries. For example, the separator is also manufactured by the following method.

[0153] A polymer resin, filler, and solvent are mixed to prepare a separator composition. The separator composition may be directly coated and dried on top of the electrode to form a separator. Alternatively, after the separator composition is cast and dried on a support, the separator film peeled off from the support may be laminated on top of the electrode to form a separator.

[0154] The polymer resin used in separator manufacturing is not particularly limited, and any can be used as long as it is a substance used as a binder for the electrode plate. For example, vinylidene fluoride / hexafluoropropylene copolymer, polyvinylidene fluoride (PVDF), polyacrylonitrile, polymethyl methacrylate, or mixtures thereof are used.

[0155] The separator may contain a ceramic component to improve the performance of the membrane. For example, the separator can be manufactured by coating it with an oxide or including ceramic particles during the manufacturing process. Next, an electrolyte is prepared.

[0156] For example, the electrolyte can be an organic electrolyte solution or a solid. Examples include, but are not limited to, boric oxide and lithium oxynitride. Any solid electrolyte that can be used in the technical field can be employed. The solid electrolyte may be formed on the negative electrode by methods such as sputtering.

[0157] For example, an organic electrolyte solution is prepared. The organic electrolyte solution is manufactured by dissolving a lithium salt in an organic solvent.

[0158] Any organic solvent that can be used as an organic solvent in the technical field can be used. Examples include propylene carbonate, ethylene carbonate, fluoroethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, methyl isopropyl carbonate, dipropyl carbonate, dibutyl carbonate, fluoroethylene carbonate, benzonitrile, acetonitrile, tetrahydrofuran, 2-methyltetrahydrofuran, γ-butyrolactone, dioxolane, 4-methyldioxolane, N,N-dimethylformamide, N,N-dimethylacetamide, N,N-dimethylsulfoxide, dioxane, 1,2-dimethoxyethane, sulfolane, dichloroethane, chlorobenzene, nitrobenzene, diethylene glycol, dimethyl ether, or a mixture thereof.

[0159] Any lithium salt can be used as long as it is used as a lithium salt in the relevant technical field. For example, LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiCF3SO3, Li(CF3SO2)2N, Li(FSO2)2N, LiC4F9SO3, LiAlO2, LiAlCl4, LiN(C xF2x+1 SO2)(C y F 2y+1 SO2)(where x and y are natural numbers), LiCl, LiI, or a mixture thereof, etc.

[0160] As can be seen from FIG. 12A, the lithium battery 121 includes a positive electrode 123, a negative electrode 122, and a separator 124. The aforementioned positive electrode 123, negative electrode 122, and separator 124 are wound or folded and housed in a battery case 125. Next, an organic electrolyte is injected into the battery case 125 and sealed by a cap assembly 126, and the lithium battery 121 is completed. The battery case 125 can also be cylindrical, rectangular, thin-film type, etc. For example, the lithium battery 121 can also be a thin-film battery. The lithium battery 121 can also be a lithium-ion battery.

[0161] A separator may be disposed between the positive electrode and the negative electrode to form a battery structure. After the battery structure is laminated into a bicell structure, impregnated with an organic electrolyte, and the resulting product is housed and sealed in a pouch, a lithium-ion polymer battery is completed.

[0162] Also, a plurality of battery structures are laminated to form a battery pack, and such a battery pack is used in all devices that require high capacity and high output. For example, it is also used in notebook computers, smartphones, electric vehicles (EVs), etc.

[0163] Since the lithium battery has excellent high-rate characteristics and life characteristics, it is suitable for electric vehicles (EVs). For example, it is suitable for hybrid vehicles such as plug-in hybrid electric vehicles (PHEVs).

[0164] Still other aspects provide a field emission device including the complex, or the complex and a carbon composite including a carbon-based material.

[0165] A field emission device is a device that utilizes electron movement. A normal field emission device includes at least a reduction electrode, an emitter chip, and an oxidation electrode separated from the reduction electrode (for the respective details, refer to U.S. Patent Nos. 7,009,331, 6,976,897, 6,911,767, and U.S. Patent Application No. 2006 / 0066217, which are incorporated herein by reference). A voltage is applied to the reduction electrode and the oxidation electrode to emit electrons from the emitter chip. The electrons travel from the reduction electrode toward the oxidation electrode. The present device is then used in various applications including, but not limited to, an ultrasonic vacuum tube device (e.g., an X-ray tube), a power amplifier, an ion gun, a high-energy accelerator, a free electron laser, and an electron microscope, and particularly for flat panel displays. Flat panel displays are also used as a replacement for conventional cathode ray tubes. Accordingly, those flat panel displays are applied to TVs (televisions) and computer monitors.

[0166] As the emitter chip, a composite according to one embodiment, or a carbon composite using the same, may be used.

[0167] Conventional emitter chips are manufactured from metals such as molybdenum and semiconductors such as silicon. One concern regarding the use of metal emitter chips is that the control voltage required for emission is relatively high, for example, approximately 100 V. Also, since those emitter chips do not have uniformity, the current density between pixels also becomes non-uniform.

[0168] By using the emitter chip using the aforementioned silicon-containing composite or carbon composite, excellent field emission characteristics can be obtained. The aforementioned silicon-containing composite or carbon composite can be used during the manufacture of an electroluminescent device.

[0169] According to yet another aspect, there is provided a biosensor including a silicon-containing composite according to one embodiment, or the silicon-containing composite and a carbon composite including a carbon-based material. The silicon-containing composite or carbon composite according to one embodiment can be used when forming an electrode for a biosensor.

[0170] FIG. 12E is a cross-sectional view showing the electrode structure of a biosensor according to one embodiment. Referring to it, a biosensor electrode according to one embodiment includes a substrate 310, a first layer 320 including a silicon-containing composite or a carbon composite formed on the substrate 310, and a second layer 330 formed on the first layer. The second layer 330 supports or immobilizes a biological substance 340 in various ways.

[0171] The substrate 310 means all kinds of plates on which graphene is deposited or formed at its upper part. Specifically, it is also selected from the group consisting of glass, plastic, metal, ceramics and silicon. It should be noted that the type of the substrate is not particularly limited as long as graphene is deposited or formed on its upper part.

[0172] As the biological substance 340, a biological substance selected from the group consisting of enzymes, aptamers, proteins, nucleic acids, microorganisms, cells, lipids, hormones, DNA, PNA, RNA, and mixtures thereof is used, and it should be noted that various biological substances not mentioned in this specification are used.

[0173] Referring to FIG. 12E, as the biological substance 340, a specific enzyme is used, and the second layer 330 discloses an electrode for a biosensor in which such a specific enzyme is supported or a membrane on which the enzyme is immobilized is used. On the other hand, in FIG. 12E, although the specific enzyme is shown as being supported or immobilized inside the membrane, it should be noted that the position of the specific enzyme is not limited thereto, and part or all of it may protrude above the membrane. In such a configuration, since the enzyme has excellent substrate specificity and selectively reacts only with specific molecules even in a mixture, it can selectively detect an analyte (e.g., blood glucose, etc.) that reacts with the specific enzyme.

[0174] According to still another aspect, a semiconductor device including the silicon-containing composite, or the silicon-containing composite and a carbon composite including a carbon-based material is provided. The silicon-containing composite or the carbon composite can be used as an electrode of a semiconductor device. According to still another aspect, a thermoelectric material including the silicon-containing composite, or the silicon-containing composite and a carbon composite including a carbon-based material, and a thermoelectric device including the same are provided.

[0175] The thermoelectric performance of the thermoelectric material is improved by its excellent electrical properties. Such a thermoelectric material is usefully used in a thermoelectric device, a thermoelectric module, or a thermoelectric apparatus.

[0176] The performance of the thermoelectric material is evaluated using the ZT value of the following Equation 1, which is commonly referred to as the dimensionless figure of merit. (Equation 1) ZT=(S 2 σT) / k In Equation 1, ZT represents the figure of merit, S represents the Seebeck coefficient, σ represents the electrical conductivity, T represents the absolute temperature, and κ represents the thermal conductivity.

[0177] As shown in Equation 1, in order to increase the ZT value of the thermoelectric material, the Seebeck coefficient and the electrical conductivity, that is, the power factor (S 2σ) should be increased, and the thermal conductivity should be decreased.

[0178] A silicon-containing composite or carbon composite according to an embodiment includes graphene. When applying the properties of graphene to a thermoelectric material, it will exhibit high electrical conductivity and low thermal conductivity, thus improving the performance of the thermoelectric material.

[0179] In a silicon-containing composite or carbon composite having an embodiment, the crystallinity and electronic structure change at the interface between graphene having metallic properties and silicon having semiconductor properties, the Seebeck coefficient increases, the transmission of charge carriers is accelerated, and an increase in electrical conductivity and charge mobility can be induced. Also, phonon scattering at the interface between graphene and silicon increases, enabling control of the thermal conductivity.

[0180] As described above, the silicon-containing composite or carbon composite can be usefully used as a thermoelectric material. Therefore, the thermoelectric material can be formed into a thermoelectric element by a method such as cutting. The thermoelectric element is also a p-type thermoelectric element. Such a thermoelectric element means one in which the thermoelectric material is formed into a predetermined shape, for example, a rectangular parallelepiped shape.

[0181] On the other hand, a thermoelectric element is also a component that can be combined with an electrode and exhibit a cooling effect by applying a current and a power generation effect by a temperature difference.

[0182] FIG. 12B shows an embodiment of a thermoelectric module employing a thermoelectric element. As shown in FIG. 12B, an upper insulating substrate 211 and a lower insulating substrate 221 are formed with a patterned upper electrode (first electrode) 212 and a lower electrode (second electrode) 222, and the upper electrode 212 and the lower electrode 222 are in contact with each other through p-type thermoelectric components 215 and n-type thermoelectric components 216. These electrodes 212, 222 are connected to the outside of the thermoelectric element by lead electrodes 224. The aforementioned thermoelectric element can be used as the p-type thermoelectric component (215). The n-type thermoelectric component 216 can be used without limitation as long as it is known in the art.

[0183] As insulating substrates 211 and 221, gallium arsenide (GaAs), sapphire, silicon, Pyrex (registered trademark), quartz substrates, etc. can be used. The materials of the electrodes 212 and 222 can be variously selected from copper, aluminum, nickel, gold, titanium, etc., and their sizes can also be variously selected. The method by which these electrodes 212 and 222 are patterned can use a conventionally known patterning method without limitation, for example, a lift-off semiconductor process, a vapor deposition method, a photolithography method, etc. can be used.

[0184] In one embodiment of the thermoelectric module, as shown in FIGS. 12C and 12D, one of the first electrode and the second electrode is exposed to the heat source. In one embodiment of the thermoelectric element, one of the first electrode and the second electrode is electrically connected to the power supply source, or is electrically connected to the outside of the thermoelectric module, for example, an electrical element (e.g., a battery) that consumes or stores electricity.

[0185] As one embodiment of the thermoelectric module, one of the first electrode and the second electrode is electrically connected to the power supply source. Hereinafter, it will be described in more detail through examples and comparative examples. However, these examples are for illustrative purposes only, and the scope of the present invention is not limited only by them.

Examples

[0186] 〔Production Example 1〕 Needle-shaped silicon was pulverized to obtain plate-shaped and needle-shaped silicon particles with a length (D90) of about 150 nm and a thickness of about 40 nm, on the surface of which a silicon suboxide (SiO x )(0 < x < 2) film (thickness: about 0.1 nm) was formed.

[0187] A composition containing 25 parts by weight of the plate-shaped and needle-shaped silicon particles, 10 parts by weight of stearic acid, and 65 parts by weight of isopropyl alcohol was spray-dried and dried to obtain porous silicon secondary particles having an average particle size of about 3 to 6 μm.

[0188] The spray drying was carried out using a spray dryer (Model: MMSD (Micro Mist Spray Dryers), Fujisaki electric). Under N2 conditions, the spray nozzle size was controlled to about 150 μm, the pressure was adjusted to about 0.6 MPa, the powder injection atmosphere temperature (about 200 °C) was adjusted, and isopropyl alcohol was dried to produce secondary particles of porous silicon composite particles.

[0189] The porous silicon secondary particles were placed in a reactor. After purging the inside of the reactor with nitrogen gas, a gas mixture having the composition shown in Table 1 below was flowed into the reactor as a reaction gas to create an atmosphere composed of the gas in the reactor. The pressure generated by the gas flow in the reactor was 1 atm. Under the gas atmosphere, the internal temperature of the reactor was raised to 1,000 °C (heating rate: about 23 °C / min), and the heat treatment was carried out while continuously flowing the gas into the reactor and maintaining at that temperature for 1 hour. Next, the resultant was left standing for about 3 hours. Thereafter, the supply of the gas was interrupted, the reactor was cooled to room temperature (25 °C), the inside of the reactor was purged with nitrogen, and a silicon-containing composite was obtained.

[0190] In the silicon-containing composite, the contents of the first graphene and the second graphene are about 25 parts by weight based on 100 parts by weight of the total weight of the silicon-containing composite.

[0191] [Production Examples 2 to 6] Silicon-containing composites were obtained in the same manner as in Production Example 1, except that gas mixtures having the compositions shown in Table 1 below were used as the reaction gas, respectively.

[0192] [Production Example 7] Silicon suboxide (SiO x )(0 < x < 2) Instead of plate-shaped and needle-shaped silicon particles with a film (thickness: about 0.1 nm) formed on the surface and a length (D90) of about 150 nm and a thickness of about 40 nm, silicon suboxide (SiO xExcept for using plate-like and needle-like silicon particles with a length (D90) of about 200 nm and a thickness of about 40 nm on which a film (thickness: about 0.1 nm) of (0 < x < 2) is formed on the surface, it was carried out in the same manner as in Production Example 1 to obtain a silicon-containing composite.

[0193] [Production Example 8] Silicon suboxide (SiO x )(0 < x < 2) Instead of plate-like and needle-like silicon particles with a length (D90) of about 150 nm and a thickness of about 40 nm on which a film (thickness: about 0.1 nm) is formed on the surface, silicon suboxide (SiO x Except for using plate-like and needle-like silicon particles with a length (D90) of about 100 nm and a thickness of about 40 nm on which a film (thickness: about 0.1 nm) of (0 < x < 2) is formed on the surface, it was carried out in the same manner as in Production Example 1 to obtain a silicon-containing composite.

[0194] [Reference Production Example 1] Silicon suboxide (SiO x )(0 < x < 2) Instead of plate-like and needle-like silicon particles with a length (D90) of about 150 nm and a thickness of about 40 nm on which a film (thickness: about 0.1 nm) is formed on the surface, silicon suboxide (SiO x )(0 < x < 2) Except for using plate-like and needle-like silicon particles with a length (D90) of about 200 nm and a thickness of about 40 nm on which a film (thickness: about 0.1 nm) is formed on the surface and using a gas mixture having the composition shown in Table 1 below as the reaction gas, it was carried out in the same manner as in Production Example 1 to obtain a silicon-containing composite.

[0195] As shown in Table 1 below, the first graphene and the second graphene contained in the silicon-containing composites produced according to Production Examples 1 to 8 exhibited both film form and plate form. The first graphene and the second graphene were found to mainly have a film form in the region adjacent to silicon suboxide and a flake form in a region far from the adjacent region. The silicon-containing composite produced according to Production Example 5 showed a relatively higher ratio of the first graphene and the second graphene existing in the film form compared to the silicon-containing composites produced according to Production Examples 1 to 4 and Production Examples 6 to 8.

[0196]

Table 1

[0197] 〔Comparative Production Example 1〕 A composition containing 20 parts by weight of granular 10-μm-sized silicon, 10 parts by weight of stearic acid, and 70 parts by weight of isopropyl alcohol was used to produce a slurry containing acicular silicon particles through a crushing process and dried without going through a spraying process.

[0198] The resultant product was pulverized to obtain acicular silicon particles with a length of about 125 nm and a silicon suboxide (SiO x )(0 < x < 2) film (thickness: about 0.1 nm) formed on the surface.

[0199] The acicular silicon primary particles were placed in a reactor. In the reactor, a gas of 300 sccm of nitrogen (N2) was flowed to create an atmosphere consisting of the gas in the reactor. The pressure generated by the gas flow in the reactor was 1 atm. Under the gas atmosphere, the internal temperature of the reactor was raised to 950 °C (heating rate: about 23 °C / min), and the gas was continuously flowed into the reactor while maintaining the temperature for 3 hours for heat treatment. Next, the resultant product was left for about 4 hours to obtain porous silicon primary particles. The structure of the silicon primary particles had an acicular form.

[0200] 〔Comparative Production Example 2〕 A silicon-containing composite was produced in the same manner as in Production Example 1, except that CH4 was used as the reaction gas and pyridine was used as the nitrogen precursor. When carried out according to Comparative Production Example 2, the adhesion between silicon / silicon suboxide and the first graphene and / or the adhesion between the porous silicon secondary particles and the second graphene were quite poor.

[0201] 〔Example 1: Production of negative electrode and cell〕 A slurry was produced by mixing the silicon-containing composite produced in Production Example 1, graphite, lithium polyacrylate (Li-PAA), and deionized water. In the said slurry, the mixing ratio of the solid content of the mixture of the silicon-containing composite produced in Production Example 1 and graphite is 92:8 by weight ratio. In the mixture of the silicon-containing composite produced in Production Example 1 and graphite, the weight ratio of the silicon-containing composite and graphite is 1:12 by weight ratio.

[0202] After applying the said slurry to a copper foil (Cu foil), using a doctor blade, after removing the film so that the coating thickness becomes 40 μm, it was vacuum dried at 120 °C for 2 hours, and then it was rolled to produce a negative electrode.

[0203] The positive electrode was prepared by mixing LiNi 0.6 Co 0.2 Mn 0.2 , Denka Black, polyvinylidene fluoride (PVdF) as a binder, and N-methyl-2-pyrrolidone (NMP) as a solvent to produce a slurry. In the said slurry, the mixing weight ratio of LiNi 0.6 Co 0.2 Mn 0.2 , Denka Black, and polyvinylidene fluoride (PVdF) as a binder was 93:5:2.

[0204] A coin full cell was manufactured using the negative electrode and the positive electrode. After applying the slurry to an aluminum foil, a doctor blade was used to remove the film so that the coating thickness became 40 μm, and then it was vacuum dried at 120 °C for 2 hours, and then it was rolled to manufacture the positive electrode.

[0205] As the separator, a polypropylene film (Cellgard 3510) was used, and as the electrolyte, 1.3 M LiPF6 EC:DEC:FEC (50:25:25 volume ratio) was used. EC represents ethylene carbonate, DEC represents diethyl carbonate, and FEC represents fluoroethylene carbonate, respectively.

[0206] 〔Example 1a: Manufacture of Negative Electrode and Coin Full Cell〕 A coin full cell was fabricated in the same manner as in Example 1, except that 1.3 M LiPF6 EC:DEC:FEC (68:25:7 volume ratio) was used as the electrolyte.

[0207] 〔Examples 2 to 8: Manufacture of Negative Electrode and Coin Full Cell〕 Negative electrodes and coin full cells were manufactured in the same manner as in Example 1, except that the silicon-containing composites according to Production Examples 2 to 8 were used instead of the silicon-containing composite according to Production Example 1.

[0208] 〔Example 7a〕 A coin full cell was fabricated in the same manner as in Example 7, except that 1.3 M LiPF6 EC:DEC:FEC (68:25:7 volume ratio) was used as the electrolyte.

[0209] 〔Example 7b〕 A coin full cell was fabricated in the same manner as in Example 7, except that 1.3 M LiPF6 EC:DEC (75:25 volume ratio) was used as the electrolyte.

[0210] 〔Example 8a〕 A coin full cell was fabricated in the same manner as in Example 8, except that 1.3 M LiPF6 in EC:DEC:FEC (68:25:7 by volume) was used as the electrolyte.

[0211] 〔Example 9: Production of negative electrode and coin half cell〕 A silicon-containing composite produced according to Production Example 1, carbon black (KB600JD), AST9005 (AEKYUNG), and deionized water as a solvent were mixed to produce a slurry. In the said slurry, the solid content mixing ratio of the silicon-containing composite produced according to Production Example 1, carbon black (KB600JD), and AST9005 (AEKYUNG) was 79:1:20 by weight.

[0212] After applying the said slurry onto a copper foil, using a doctor blade, the film was removed so that the coating thickness became 40 μm, and then it was vacuum dried at 120 °C for 2 hours, and then it was rolled to produce a negative electrode. A coin half cell was fabricated using the said negative electrode and lithium metal as a counter electrode.

[0213] As the separator, a polypropylene film (Cellgard 3510) was used, and as the electrolyte, 1.3 M LiPF6 in EC (ethylene carbonate):DEC (diethyl carbonate):FEC (fluoroethylene carbonate) (2:6:2 by volume) was used.

[0214] 〔Examples 10 - 16: Production of negative electrode and coin half cell〕 Negative electrodes and coin half cells were fabricated in the same manner as in Example 9, except that the silicon-containing composites according to Production Examples 2 - 8 were used instead of the silicon-containing composite according to Production Example 1.

[0215] 〔Example 17: Production of negative electrode and coin full cell〕 Negative electrodes and coin full cells were fabricated in the same manner as in Example 1, except that carbon black (KB600JD) was used instead of graphite during the production of the negative electrode.

[0216] 〔Example 18: Production of Negative Electrode and Coin Full Cell〕 A negative electrode and a coin full cell were produced in the same manner as in Example 1, except that in the mixture of the silicon-containing composite produced according to Production Example 1 and graphite, the mixing ratio was changed from 1:12 by weight to 1:99 by weight.

[0217] 〔Example 19: Production of Negative Electrode and Coin Full Cell〕 A negative electrode and a coin full cell were produced in the same manner as in Example 1, except that in the mixture of the silicon-containing composite produced according to Production Example 1 and graphite, the mixing ratio was changed from 1:12 by weight to 3:97 by weight.

[0218] 〔Example 20: Production of Negative Electrode and Coin Full Cell〕 A negative electrode and a coin full cell were produced in the same manner as in Example 1, except that in the mixture of the silicon-containing composite produced according to Production Example 1 and graphite, the mixing ratio was changed from 1:12 by weight to 1:1 by weight.

[0219] 〔Comparative Example 1: Production of Negative Electrode and Coin Full Cell〕 A negative electrode and a coin full cell were produced in the same manner as in Example 1, except that the substance produced according to Comparative Production Example 1 was used instead of the silicon-containing composite produced according to Production Example 1.

[0220] 〔Comparative Example 1a: Production of Negative Electrode and Coin Half Cell〕 A negative electrode and a coin half cell were produced in the same manner as in Example 9, except that the substance produced according to Comparative Production Example 1 was used instead of the silicon-containing composite produced according to Production Example 1.

[0221] 〔Comparative Example 2: Production of Negative Electrode and Coin Full Cell〕 Except for using the substance produced by Comparative Production Example 2 instead of the silicon-containing composite produced by Production Example 1, the same method as in Example 1 was carried out to manufacture a negative electrode and a coin full cell.

[0222] 〔Comparative Example 2a: Manufacture of Negative Electrode and Coin Half Cell〕 Except for using the substance produced by Comparative Production Example 2 instead of the silicon-containing composite produced by Production Example 1, the same method as in Example 9 was carried out to manufacture a negative electrode and a coin half cell.

[0223] 〔Evaluation Example 1: Charge-Discharge Characteristics〕 (1) Measurement of Initial Efficiency, Rate-Determining Performance, Coulomb Efficiency, and Discharge Capacity 1) Examples 1 to 8 and Comparative Example 1 Using the full cells produced in Examples 1 to 8 and Comparative Example 1, charge-discharge characteristic evaluations were carried out for each coin cell by the following method. (Charge: 1.0C / Cutoff: 4.2V - 0.01C, Discharge: 1.0C / Cutoff: 2.8V) The charge-discharge characteristic evaluation results are as shown in Table 2 below.

[0224]

Table 2

[0225] 〔2) Examples 7a, 7b, 8a and Comparative Example 1〕 Using the coin cells produced in Examples 7a, 7b, 8a and Comparative Example 1, charge-discharge characteristic evaluations were carried out for each coin cell at 45 °C by the following method. (Charge: 1.0C / Cutoff: 4.2V - 0.01C, Discharge: 1.0C / Cutoff: 2.8V) The charge-discharge characteristic evaluation results are as shown in Table 3 below.

[0226]

Table 3

[0227] 〔Evaluation Example 2: Raman Analysis〕 Raman analysis was performed on the silicon-containing composite of Production Example 1. The Raman analysis was carried out using Raman 2010 Spectra (NT-MDT Development Co.) (laser system: 473, 633, 785 nm, lowest Raman shift: ~50 cm -1 , spatial resolution: approximately 500 nm). The Raman analysis results for the silicon-containing composite of Production Example 1 are as shown in Fig. 4. Based on the Raman analysis results, the ratio of the D peak intensity to the G peak intensity was measured and shown in Table 4 below.

[0228] Graphene shows peaks at 1,350 cm -1 , 1,580 cm -1 , 2,700 cm -1 in the Raman analysis spectrum, and these peaks provide information related to the thickness, crystallinity, and charge doping state of graphene. The peak shown at 1,580 cm-1 is a peak called the G mode, which is due to the vibration mode corresponding to the stretching of carbon-carbon bonds, and the energy of the G mode is determined by the density of excess charges doped into graphene. And the peak shown at 2,700 cm -1 is a peak called the 2D mode and is useful when evaluating the thickness of graphene. The peak that appears at 1,350 cm -1 is a peak called the D mode, which is a peak shown when there are defects in the SP 2 crystal structure. And the D / G intensity ratio (Id / Ig) provides information related to the degree of disorder of the graphene crystal.

[0229]

Table 4

[0230] Referring to Table 4, it can be seen that the silicon-containing composite produced by Production Example 1 has improved crystallinity and quality of graphene.

[0231] 〔Evaluation Example 3: XPS Analysis (Oxygen and Carbon Contents of Graphene)〕 1) XPS analysis was performed on the silicon-containing composites produced by Production Examples 1 to 8, the oxygen and carbon contents were analyzed, and the analysis results are shown in Table 5 below. For the XPS analysis, Quantum 2000 (Physical Electronics Inc.) was used (acceleration voltage: 0.5 to 15 keV, 300 W, energy resolution: approximately 1.0 eV, sputter rate: 0.1 nm / min).

[0232]

Table 5

[0233] In Table 5 above, the carbon content indicates the content of carbon corresponding to the C1s peak, and the oxygen content indicates the oxygen content corresponding to the O1s peak.

[0234] 〔Evaluation Example 4: Scanning Electron Microscope〕 SEM (scanning electron microscope) analysis was performed on the silicon-containing composite produced by Production Example 1. The SEM analysis results of the silicon-containing composite produced by Production Example 1 are shown in FIGS. 9A and 9B, and the SEM analysis results of the product obtained by Reference Production Example 1 are shown in FIGS. 10A and 10B.

[0235] Referring to them, it was found that the silicon-containing composite produced by Production Example 1 has excellent adhesion of the shell to the core and uniformly formed small-sized graphene layers compared with the product of Reference Example 1.

[0236] 〔Evaluation Example 5: Thermogravimetric Analysis〕 Thermogravimetric analysis was performed on the silicon-containing composites produced in Production Example 1 and Reference Production Example 1. The results of the thermogravimetric analysis are shown in FIG. 5. Referring to FIG. 5, it was found that the silicon-containing composite of Production Example 1 had a 20 wt% loss temperature of about 720°C, which was lower than that of Reference Production Example 1 (20 wt% loss temperature: 708°C), indicating improved thermal stability and a shift of the TGA derivative peak position to the higher temperature side.

[0237] 〔Evaluation Example 6: DCIR (direct-current internal resistance) characteristics〕 1) Examples 1 to 8 and Comparative Example 1 The resistance characteristics of the full cells produced in Example 1 and Comparative Example 1 after the first cycle and after the 100th cycle were measured by the following method.

[0238] For each full cell, at 25°C with a current of 0.1C rate, constant current charging was performed until the voltage reached 4.30 V (vs. Li), and then, while maintaining 4.30 V in the constant voltage mode, it was cut off with a current of 0.05C rate. Next, during discharge, it was discharged with a constant current of 0.1C rate until the voltage reached 2.8 V (vs. Li) (formation stage, first cycle). Such charge-discharge processes were further performed twice to complete the formation process.

[0239] For each full cell, at 25°C with a current of 0.1C rate (0.38 mA / cm 2 ), constant current charging was performed until the voltage reached 4.40 V (vs. Li), and then, while maintaining 4.40 V in the constant voltage mode, it was cut off with a current of 0.05C rate (second cycle).

[0240] For the lithium battery after the second cycle, at 25 °C, a constant current charge was performed at a current of 1.0 C rate until the voltage reached 4.3 V (versus Li). Next, while maintaining 4.3 V in the constant voltage mode, it was cut off at a current of 0.01 C rate. Next, during discharge, it was discharged at a constant current of 1.0 C rate until the voltage reached 2.8 V (versus Li) (the third cycle), and such a cycle was repeatedly performed under the same conditions (the 100th cycle).

[0241] After performing charge and discharge as described above, the impedance of the lithium metal battery was measured by using an impedance analyzer (Solartron 1260A Impedance / Gain-Phase Analyzer) and applying a voltage bias of 10 mV in the frequency range of 25 °C, 106 to 0.1 MHz by the two-probe method to evaluate the direct current internal resistance (DCIR) after the first cycle. The DCIR increase rate was calculated by the following formula 2, and the evaluation results are shown in Table 6. (Formula 2) DCIR increase rate = {(DCIR after the 100th cycle) / (DCIR after the first cycle)} X 100 Referring to it, the full cell of Example 1 had a lower DCIR increase rate compared to the case of Comparative Example 1.

[0242] [Table 6]

[0243] Referring to Table 6, it was found that in the full cells manufactured according to Examples 1, 7, and 8, the DCIR increase rate decreased compared to the full cell of Comparative Example 1. 2) Examples 7a, 7b, 8a and Comparative Example 1 The resistance characteristics after the first cycle and the 100th cycle of the full cells manufactured according to Examples 7a, 7b, 8a and Comparative Example 1 were measured by the following method.

[0244] For each full cell, at 25°C with a current of 0.1C rate, constant current charging was carried out until the voltage reached 4.30V (versus Li), and then, while maintaining 4.30V in the constant voltage mode, it was cut off with a current of 0.05C rate. Next, during discharge, it was discharged at a constant current of 0.1C rate until the voltage reached 2.8V (versus Li) (formation stage, first cycle). Such charge-discharge processes were further carried out two more times to complete the formation process.

[0245] For each full cell, at 25°C with a current of 0.1C rate (0.38mA / cm 2 ), constant current charging was carried out until the voltage reached 4.40V (versus Li), and then, while maintaining 4.40V in the constant voltage mode, it was cut off with a current of 0.05C rate (second cycle).

[0246] For the lithium battery after the second cycle, at 25°C with a current of 1.0C rate, constant current charging was carried out until the voltage reached 4.3V (versus Li), and then, while maintaining 4.3V in the constant voltage mode, it was cut off with a current of 0.01C rate. Next, during discharge, it was discharged at a constant current of 1.0C rate until the voltage reached 2.8V (versus Li) (third cycle), and such cycles were repeatedly carried out under the same conditions (100th cycle).

[0247] After carrying out charge-discharge in such a manner, the impedance of the lithium metal battery was measured by using an impedance analyzer (Solartron 1260A Impedance / Gain-Phase Analyzer) with the two-probe method to evaluate the direct current internal resistance (DCIR) after the first cycle by applying a voltage bias of 10mV in the frequency range of 25°C, 106 to 0.1MHz to measure the resistance. The DCIR increase rate was calculated by the following formula 2, and the evaluation results are shown in Table 7 below. (Formula 2) DCIR increase rate = {(DCIR after the 100th cycle) / (DCIR after the first cycle)} X 100 Referring to it, the full cells of Examples 7a, 7b, and 8a had a decreased DCIR increase rate compared to the case of Comparative Example 1.

[0248]

Table 7

[0249] 〔Evaluation Example 7: Rate-determining Performance〕 For the full cells prepared according to Example 1, 7, 8 and Comparative Example 1, at 25 °C with a current of 0.1 C rate, constant current charging was performed until the voltage reached 4.30 V (vs. Li), and then, while maintaining 4.30 V in the constant voltage mode, it was cut off with a current of 0.05 C rate. Next, during discharge, it was discharged with a constant current of 0.1 C rate until the voltage reached 3.0 V (vs. Li) (first cycle, formation cycle).

[0250] For the lithium battery after the first cycle, at 25 °C with a current of 0.2 C rate, constant current charging was performed until the voltage reached 4.3 V (vs. Li), and then, while maintaining 4.3 V in the constant voltage mode, it was cut off with a current of 0.01 C rate. Next, during discharge, it was discharged with a constant current of 0.2 C rate until the voltage reached 3.0 V (vs. Li) (second cycle).

[0251] For the lithium battery after the second cycle, at 25 °C with a current of 0.5 C rate, constant current charging was performed until the voltage reached 4.3 V (vs. Li), and then, while maintaining 4.3 V in the constant voltage mode, it was cut off with a current of 0.01 C rate. Next, during discharge, it was discharged with a constant current of 0 C rate until the voltage reached 3.0 V (vs. Li) (third cycle).

[0252] For the lithium battery after the third cycle, at 25 °C with a current of 1.0 C rate, constant current charging was performed until the voltage reached 4.3 V (vs. Li), and then, while maintaining 4.3 V in the constant voltage mode, it was cut off with a current of 0.01 C rate. Next, during discharge, it was discharged with a constant current of 1.0 C rate until the voltage reached 3.0 V (vs. Li) (fourth cycle).

[0253] In the above-described full charge-discharge cycles, a 10-minute stop time was provided after one charge / discharge cycle. The rate capability of each full cell is defined by the following Equation 3. (Equation 3) Rate capability [%] = (discharge capacity when discharging a cell at a rate of 1C in the third cycle) / (discharge capacity when discharging a cell at a rate of 0.2C in the second cycle) X 100 Each evaluation result is shown in Table 8.

[0254]

Table 8

[0255] Referring thereto, the full cells of Examples 1, 7, and 8 had improved rate capabilities as compared to the full cell of Comparative Example 1.

[0256] 〔Evaluation Example 8: XPS Analysis (C / Si Content)〕 XPS analysis was performed on the silicon-containing composites produced by Production Example 1 and Reference Production Example 1. Using X-ray photo electron spectroscopy, quantitative analysis of carbon atoms and silicon atoms in each sample was performed. When photons (X-rays) having a certain energy are irradiated onto a sample, photoelectrons are emitted from the sample. By measuring the kinetic energy of the photoelectrons, the binding energy required to emit the photoelectrons from the sample can be known. Since the binding energy is an atomic-specific property, elemental analysis and measurement of the surface concentration of elements are possible through it. Thereby, the C / Si content is calculated from the amounts of the quantitatively analyzed carbon atoms and silicon atoms.

[0257] XPS analysis was performed using Quantum 2000 (Physical Electronics Inc.) (acceleration voltage: 0.5 - 15 keV, 300 W, energy resolution: approximately 1.0 eV, minimum analysis area: 10 micro, sputter rate: 0.1 nm / min).

[0258] After each sample was vacuum-dried at 110 for 12 hours, in the XPS pre-chamber, at room temperature, in a vacuum of 10 -4 ~10 -5 torr, degassing treatment was carried out for 1 - 8 hours. After introducing the sample into the analysis chamber, measurement was performed after the background vacuum reached the order of 10 -10 torr. Peaks with binding energies of 98 to 105 eV were attributed to Si2p, and peaks with binding energies of 282 to 297 eV were attributed to C1s. The C / Si content was calculated as the ratio of the integrated values of these peaks. In the XPS analysis results, the parts related to C1s, Si2p, and N1s are shown in FIGS. 6, 7, and 8 respectively, and Table 9 below shows the C / Si content and the content of each element.

[0259]

Table 9

[0260] Referring to Table 9, the silicon-containing composite of Production Example 1 had an increased C / Si content compared to the silicon-containing composite of Reference Example 1. From such results, it was found that the silicon-containing composite of Production Example 1 was superior in the adhesion between silicon / silicon oxide and graphene and in the coating uniformity of graphene compared to the silicon-containing composite of Reference Production Example 1.

[0261] 〔Evaluation Example 9: TEM Analysis〕 The silicon-containing composite of Production Example 1 was analyzed using a transmission electron microscope. During the TEM analysis, Titan cubed G260 - 300 from FEI was used as the analyzer. The TEM analysis photographs of the silicon-containing composite of Production Example 1 are as shown in FIGS. 11A and 11B.

[0262] Referring to them, it was found that the silicon-containing composite of Production Example 1 is excellent in the adhesion between silicon / silicon oxide and graphene and the graphene coating uniformity on silicon / silicon oxide.

[0263] As shown in FIG. 11A, it was confirmed that the first graphene and the second graphene are oriented at a 90° angle with respect to the main axis (Y-axis) of the plate-like and needle-like silicon particles formed on the surface of the silicon suboxide (SiO x )(0 < x < 2) film.

[0264] Above, one embodiment has been described with reference to the drawings and examples, but they are merely illustrative, and those skilled in the art in the relevant technical field will be able to understand that various modifications and equivalent other embodiments are possible from them. Therefore, the protection scope of the invention is determined by the scope of the claims.

Industrial Applicability

[0265] The silicon-containing composite, its manufacturing method, the carbon composite using the same, the electrode containing the same, the lithium battery, and the electronic device of the present invention can be effectively applied to, for example, the technical field related to thermoelectric modules.

Explanation of Signs

[0266] 1 Core 2 Shell 10 Silicon primary particles 10a First graphene 10b Second graphene 11 Silicon-containing composite 121 Lithium battery 122 Negative electrode 123 Positive electrode 124 Separator 125 Battery case 126 Cap assembly

Claims

1. A silicon-containing composite comprising a porous core containing porous silicon secondary particles and a shell containing second graphene on at least one surface of the porous core, wherein the porous silicon secondary particles include aggregates of two or more silicon composite primary particles, The silicon composite primary particles include silicon, silicon suboxide (SiO ｘ )(O < x < 2) on at least one surface of the silicon, and first graphene on at least one surface of the silicon suboxide, one or more selected from the first graphene and the second graphene contain one or more elements selected from nitrogen (N), phosphorus (P), and sulfur (S), the first graphene is directly grown graphene on the surface of silicon suboxide, and the second graphene is directly grown graphene on the surface of porous silicon secondary particles, the silicon is acicular, the silicon-containing composite has a double core / shell structure, a silicon-containing composite.

2. The silicon suboxide exists in a film state, The silicon-containing composite according to claim 1, wherein the first graphene and the second graphene each exist in a film state.

3. The silicon-containing composite according to claim 1 or 2, wherein the content of one or more selected from nitrogen, phosphorus, and sulfur at a surface depth of 10 nm or less determined by XPS (X-ray photoelectron spectroscopy) analysis of the silicon-containing composite is 0.2 atomic% or less.

4. The elemental ratio (C / Si) of silicon (Si) to carbon (C) determined by XPS (X-ray photoelectron spectroscopy) analysis of the silicon-containing composite is 100 to 200, The silicon-containing composite according to any one of claims 1 to 3, wherein the elemental ratio (C / Si) of carbon (C) to silicon (Si) determined by XPS analysis of the silicon-containing composite is increased compared to the C / Si ratio of a silicon-containing composite not containing one or more selected from nitrogen, phosphorus, and sulfur.

5. The silicon-containing composite according to any one of claims 1 to 4, wherein the intensity ratio (Id / Ig) of the D peak to the G peak determined by the Raman analysis spectrum of the silicon-containing composite is 0.8 to 1.

5.

6. The 20% weight loss temperature determined by thermogravimetric analysis of the silicon-containing composite is 7 to 15 °C higher than the 20% weight loss temperature of a silicon-containing composite that does not contain one or more elements selected from nitrogen, phosphorus, and sulfur, The silicon-containing composite according to any one of claims 1 to 5, characterized in that.

7. In the silicon-containing composite, the oxygen content is 0.01 to 15 atomic% based on the total content of oxygen, carbon, and silicon atoms in the silicon-containing composite. The silicon-containing composite according to any one of claims 1 to 6, characterized in that.

8. The silicon-containing composite according to any one of claims 1 to 7, characterized in that it includes a carbon coating film containing amorphous carbon on at least one surface of the silicon-containing composite.

9. The silicon-containing composite according to claim 8, characterized in that the carbon coating film contains one or more elements selected from nitrogen, phosphorus, and sulfur.

10. The silicon-containing composite according to claim 8 or 9, characterized in that the carbon coating film further contains crystalline carbon.

11. The crystalline carbon is one or more selected from the group consisting of fullerene, natural graphite and artificial graphite, graphene and carbon nanotubes, The silicon-containing composite according to claim 10, characterized in that the amorphous carbon is one or more selected from the group consisting of pitch carbon, soft carbon, hard carbon, mesophase pitch carbide, calcined coke and carbon fiber.

12. The carbon coating film is a non-porous continuous coating film, and the carbon coating film thickness is 1 to 5,000 nm. The silicon-containing composite according to any one of claims 8 to 11, characterized in that.

13. Silicon, and a structure containing silicon suboxide (SiO ｘ )(O < x < 2), obtaining porous silicon secondary particles from a composition containing a dispersant and a solvent, Supplying a carbon source to the porous silicon secondary particles and performing a heat treatment, i) A nitrogen precursor is supplied simultaneously with the supply of the carbon source, or ii) Reacting the silicon-containing composite with a nitrogen precursor, A method for producing a silicon-containing composite, which produces the silicon-containing composite according to any one of claims 1 to 12.

14. The solvent is an alcohol-based solvent, and the step of obtaining the porous silicon secondary particles from the composition is carried out by spray-drying the composition. The method for producing a silicon-containing composite according to claim 13, wherein:

15. The dispersant is one or more selected from stearic acid, resorcinol, polyvinyl alcohol, and carbon pitch. The method for producing a silicon-containing composite according to claim 13 or 14, wherein:

16. The nitrogen precursor is ammonia. The method for producing a silicon-containing composite according to any one of claims 13 to 15, wherein:

17. The carbon source contains one or more selected from the group consisting of a compound represented by the following Chemical Formula 1, a compound represented by the following Chemical Formula 2, and an oxygen-containing compound represented by the following Chemical Formula 3. The method for producing a silicon-containing composite according to any one of claims 13 to 16, wherein: (Chemical Formula 1) C ｎ H （２ｎ＋２－ａ） [OH] ａ In the Chemical Formula 1, n is an integer from 1 to 20, and a is 0 or 1. (Chemical Formula 2) C ｎ H （２ｎ） In the Chemical Formula 2, n is an integer from 2 to 6. (Chemical Formula 3) C ｘ H ｙ O ｚ In the Chemical Formula 3, x is an integer from 1 to 20, y is 0, or an integer from 1 to 20, and z is 1 or 2.

18. The carbon source further contains a first oxygen-containing compound represented by the following Chemical Formula 3a, and the first oxygen-containing compound represented by the following Chemical Formula 3a is different from the oxygen-containing compound represented by the Chemical Formula 3. The method for producing a silicon-containing composite according to claim 17, wherein: (Chemical Formula 3a) C ｘ H ｙ O ｚ In the Chemical Formula 3a, x is 0, or an integer from 1 to 20, y is 0, or an integer from 1 to 20, and z is 1 or 2.

19. The carbon source contains one or more selected from the group consisting of methane, ethylene, propylene, acetylene, methanol, ethanol, and propanol. The method for producing a silicon-containing composite according to any one of claims 14 to 18, wherein:

20. The content of the nitrogen precursor is 20% by volume or less based on the total volume of the carbon source gas and the nitrogen precursor. The method for producing a silicon-containing composite according to any one of claims 13 to 19, wherein:

21. The method for producing a silicon-containing composite according to any one of claims 13 to 20, wherein the heat treatment is carried out at 750 to 1,100 °C.

22. The method for producing a silicon-containing composite according to any one of claims 13 to 21, further comprising the step of dry-mixing a composition containing the silicon-containing composite, a carbonaceous material, and a solvent to obtain a silicon-containing composite having a carbon coating film formed thereon.

23. In the step of dry-mixing a composition containing the silicon-containing composite, a carbonaceous material, and a solvent, further comprising one or more selected from nitrogen precursors, sulfur precursors, and phosphorus precursors, or The method for producing a silicon-containing composite according to claim 22, wherein the silicon-containing composite having a carbon coating film formed thereon is reacted with one or more selected from nitrogen precursors, sulfur precursors, and phosphorus precursors.

24. A carbon composite comprising the silicon-containing composite according to any one of claims 1 to 12 and a carbon-based material.

25. The carbon composite according to claim 24, wherein the content of the carbon-based material is 0.001 to 99 parts by weight based on 100 parts by weight of the carbon composite.

26. An electrode comprising the silicon-containing composite according to any one of claims 1 to 12, or the silicon-containing composite and a carbon composite containing a carbon-based material.

27. The electrode according to claim 26, wherein the carbon-based material is one or more selected from the group consisting of graphene, graphite, fullerene, carbon fiber, and carbon nanotube, and the content of the carbon-based material is 0.001 to 99.999 parts by weight based on 100 parts by weight of the carbon composite.

28. A lithium battery comprising the electrode according to claim 26.

29. An element comprising the silicon-containing composite according to any one of claims 1 to 12, or the silicon-containing composite and a carbon composite containing a carbon-based material.

30. The element according to claim 29, wherein the element is a field emission element, a biosensor, a semiconductor element, or a thermoelectric element.

31. A silicon-containing composite comprising a core containing porous silicon secondary particles and a shell containing a second graphene disposed on top of the core, The porous silicon secondary particles include aggregates of two or more silicon composite primary particles. The silicon composite primary particles are i) SiO ｘ (0 < x < 2), and ii) SiO ｘ (0 < x < 2), and one or more silicon oxides selected from the heat treatment products thereof, and first graphene disposed on the silicon oxide, and one or more selected from the first graphene and the second graphene each contain one or more selected from nitrogen, phosphorus, and sulfur. The first graphene is directly grown graphene on the surface of silicon oxide, and the second graphene is directly grown graphene on the surface of porous silicon secondary particles. SiO ｘ The silicon in (0 < x < 2) is acicular, The silicon-containing composite is a silicon-containing composite having a double core / shell structure.

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