Silicon carbon composite, negative electrode active material, negative electrode composition, negative electrode, and lithium secondary battery

Abstract

The present invention 29 This invention relates to a silicon-carbon composite having a peak A in the range of 20 ppm to -15 ppm, a peak B in the range of -20 ppm to -100 ppm, and a peak C in the range of -110 ppm to -140 ppm in a Si-MAS-NMR spectrum, as well as a negative electrode active material, negative electrode composition, negative electrode, lithium secondary battery, battery module, and battery pack containing the same.

Description

[Technical Field]

[0001] This application claims the benefit as of the filing date of Korean Patent Application No. 10-2023-0136853, filed with the Korean Intellectual Property Office on 13 October 2023, and all its contents are incorporated herein by reference.

[0002] This application relates to silicon-carbon composites, negative electrode active materials, negative electrode compositions, negative electrodes, and lithium secondary batteries. [Background technology]

[0003] In recent years, with the rapid proliferation of battery-powered electronic devices such as mobile phones, laptops, electric vehicles, power tools, and vacuum cleaners, the demand for small, lightweight, and relatively high-capacity and / or high-power rechargeable batteries has been rapidly increasing. In particular, lithium-ion batteries, being lightweight and possessing high energy density, have attracted considerable attention as a power source for electronic devices. As a result, research and development efforts to improve the performance of lithium-ion batteries are being actively pursued.

[0004] Generally, a lithium secondary battery includes a positive electrode, a negative electrode, a separator interposed between the positive and negative electrodes, an electrolyte, an organic solvent, and the like. Furthermore, active material layers containing positive electrode active material and negative electrode active material can be formed on a current collector at both the positive and negative electrodes. Generally, lithium-containing metal oxides such as LiCoO2 and LiMn2O4 are used as the positive electrode active material, while lithium-free carbon-based active materials and silicon-based active materials are used as the negative electrode active material.

[0005] Batteries using graphite as the negative electrode active material can exhibit a high discharge voltage of 3.6V, but their capacity is low, limiting their ability to increase energy density.

[0006] In contrast, silicon-based active materials are attracting attention as next-generation anode active materials due to their high capacity and efficiency. Therefore, there is a need to develop silicon-based active materials with high capacity or efficiency characteristics.

Summary of the Invention

Problems to be Solved by the Invention

[0007] One embodiment of the present invention aims to provide a silicon-carbon composite that can be used as a negative electrode active material having excellent capacity and / or efficiency characteristics.

[0008] One embodiment of the present invention aims to provide a silicon-carbon composite that can be used as a negative electrode active material having excellent aqueous system processability and reduced gas generation.

[0009] One embodiment of the present invention aims to provide a silicon-carbon composite that can be used as a negative electrode active material having excellent life characteristics.

[0010] One embodiment of the present invention aims to provide a negative electrode active material, a negative electrode composition, a negative electrode, and a lithium secondary battery including the silicon-carbon composite.

Means for Solving the Problems

[0011] One embodiment of the present invention is 29 In the Si-MAS-NMR spectrum, it has peak A within the range of chemical shift values of 20 ppm to -15 ppm, peak B within the range of -20 ppm to -100 ppm, and peak C within the range of -110 ppm to -140 ppm, and the ratio ((B + C) / A) of the sum of the intensities of peak B and peak C to the intensity of peak A is 3 or more and less than 4, and a silicon-carbon composite is provided.

[0012] In one embodiment of the present invention, the silicon-carbon composite contains carbon, and the carbon may be contained in an amount of 38 parts by weight to 50 parts by weight based on 100 parts by weight of the silicon-carbon composite.

[0013] In one embodiment of the present invention, the silicon-carbon composite may be porous carbon-based particles and particles having a silicon-based material provided in at least a portion of the interior and surface of the porous carbon-based particles; or porous silicon-based particles and particles having carbon provided in at least a portion of the interior and surface of the porous silicon-based particles.

[0014] In one embodiment of the present invention, the silicon-carbon composite further includes a carbon layer on its surface, and the total weight of the carbon layer may be 5% to 40% by weight based on 100% by weight of the silicon-carbon composite particles.

[0015] In one embodiment of the present invention, the pore volume of the silicon-carbon composite is 0.005 cm³. 3 / g~0.03cm 3 / g is also acceptable.

[0016] In one embodiment of the present invention, the pore size of the silicon-carbon composite may be 10 nm to 20 nm.

[0017] In one embodiment of the present invention, the silicon-carbon composite may have a D90 particle size of 5 μm to 15 μm, a D50 particle size of 1 μm to 10 μm, a Dmin of 1 μm to 3 μm, and a Dmax of 17 μm to 23 μm.

[0018] One embodiment of the present invention provides a negative electrode active material comprising a silicon-carbon composite according to the embodiment described above.

[0019] In one embodiment of the present invention, the silicon-carbon composite is provided in an amount of 0.1 to 14 parts by weight based on 100 parts by weight of the negative electrode active material.

[0020] In one embodiment of the present invention, the negative electrode active material further comprises a carbon-based active material, the carbon-based active material may be present in an amount of 86 parts by weight or more and 99.9 parts by weight or less based on 100 parts by weight of the negative electrode active material.

[0021] One embodiment of the present invention provides a negative electrode composition comprising a negative electrode active material, a binder, and a conductive material according to the embodiment described above.

[0022] One embodiment of the present invention provides a negative electrode comprising the negative electrode composition according to the embodiment described above.

[0023] One embodiment of the present invention provides a lithium secondary battery including a negative electrode, a positive electrode, and a separator according to the embodiment described above.

[0024] One embodiment of the present invention provides a battery module including a lithium secondary battery according to the embodiment described above.

[0025] One embodiment of the present invention provides a battery pack including a lithium secondary battery according to the embodiment described above.

[0026] One embodiment of the present invention provides a battery pack including a battery module according to the embodiment described above.

[0027] One embodiment of the present invention is a method for producing a silicon-carbon composite, comprising the steps of: heat-treating silicon oxide powder to carry out a disproportionation reaction; etching the heat-treated silicon oxide powder with an etching agent; pulverizing the etched silicon oxide powder to obtain porous silicon particles; and reacting the porous silicon particles with a carbon compound to form a carbon layer on the surface of the porous silicon particles, The aforementioned silicon-carbon composite is 29 The present invention provides a method for producing a silicon-carbon composite, wherein the Si-MAS-NMR spectrum has a peak A in the range of 20 ppm to -15 ppm, a peak B in the range of -20 ppm to -100 ppm, and a peak C in the range of -110 ppm to -140 ppm, and the ratio of the sum of the intensities of peak B and peak C to the intensity of peak A ((B+C) / A) is 3 or more and less than 4.

[0028] One embodiment of the present invention is a method for producing a silicon-carbon composite, comprising the steps of: depositing silicon onto porous carbon particles by chemical vapor deposition (CVD); and forming a carbon layer on the surface of the silicon-deposited porous carbon particles, The aforementioned silicon-carbon composite is 29 The present invention provides a method for producing a silicon-carbon composite, wherein the Si-MAS-NMR spectrum has a peak A in the range of 20 ppm to -15 ppm, a peak B in the range of -20 ppm to -100 ppm, and a peak C in the range of -110 ppm to -140 ppm, and the ratio of the sum of the intensities of peak B and peak C to the intensity of peak A ((B+C) / A) is 3 or more and less than 4. [Effects of the Invention]

[0029] According to embodiments of the present invention, 29 In the Si-MAS-NMR spectrum, a lithium secondary battery with improved capacity and / or efficiency can be provided by satisfying the requirement that the intensities of multiple chemical shift values ​​within a specific range are within a specific ratio range. Specifically, by satisfying the requirement that the intensity ratio between peaks within a specific range is within a specific range, the lifetime characteristics and / or aqueous processability can be improved. When the intensity ratio is within the range according to the embodiments of the present invention, higher intensities offer advantages in capacity and efficiency, and the change in phase stability (viscosity) in the negative electrode slurry containing a binder such as carboxymethylcellulose (CMC) is less, resulting in less gas generation such as H2, and thus excellent aqueous processability. [Brief explanation of the drawing]

[0030] [Figure 1] This graph shows the NMR analysis results of the silicon-carbon composite fabricated in Example 1. [Figure 2] This graph shows the NMR analysis results of the silicon-carbon composite fabricated in Example 2. [Figure 3] This graph shows the NMR analysis results of the silicon-carbon composite fabricated in Example 3. [Figure 4]This graph shows the NMR analysis results of the silicon-carbon composites produced in Comparative Examples 1, 2, and 5. [Figure 5] This graph shows the NMR analysis results of the silicon-carbon composite manufactured in Comparative Example 3. [Figure 6] This graph shows the NMR analysis results of the silicon-carbon composite produced in Comparative Example 6. [Figure 7] This graph shows the NMR analysis results of the silicon-carbon composite produced in Comparative Example 7. [Figure 8] This shows the results of waveform analysis based on the NMR analysis results of the silicon-carbon composite of Example 2. [Modes for carrying out the invention]

[0031] The present invention will be described in more detail below to aid in understanding the invention. The present invention may be realized in various different forms and is not limited to the embodiments described herein. In this regard, terms and words used herein and in the claims should not be interpreted in a manner limited to their ordinary or dictionary meanings, but rather should be interpreted in a manner consistent with the technical idea of ​​the present invention, in accordance with the principle that inventors may appropriately define the concepts of terms in order to best describe their invention.

[0032] In this specification, terms such as “include,” “provide,” or “have” indicate the presence of implemented features, figures, stages, components, or combinations thereof, and should be understood not to preemptively exclude the possibility of the presence or addition of one or more other features, figures, stages, components, or combinations thereof.

[0033] Furthermore, when a part of a layer or structure is said to be "above" or "above" another part, it includes not only the case where it is "directly above" the other part, but also the case where another part exists in between. In contrast, when a part is said to be "directly above" another part, it means that there is no other part in between. Also, when a part is said to be "above" or "above" a reference part, it means that it is located above or below the reference part, and does not necessarily mean that it is located "above" or "above" in the opposite direction of gravity.

[0034] The terms and words used herein should not be interpreted in a manner limited to their ordinary or dictionary meanings, but rather should be interpreted in a manner consistent with the technical idea of ​​the present invention, in accordance with the principle that inventors may appropriately define the concepts of terms in order to best explain their invention.

[0035] In this specification, singular expressions of terms include plural expressions unless the context clearly indicates otherwise.

[0036] Preferred embodiments of the present invention will be described in detail below. However, embodiments of the present invention may be modified in various ways, and the scope of the present invention is not limited to the embodiments described later.

[0037] A silicon-carbon composite according to one embodiment of the present invention is 29The Si-MAS-NMR spectrum is characterized by having peak A in the chemical shift range of 20 ppm to -15 ppm, peak B in the range of -20 ppm to -100 ppm, and peak C in the range of -110 ppm to -140 ppm, and the ratio ((B+C) / A) of the sum of the intensities of peak B and peak C to the intensity of peak A is 3 or more and less than 4. The ratio may be, for example, 3.2 or more and 4 or less. Here, if at least one of peaks A, peak B, and peak C contains two or more peaks, when calculating the ratio, the intensity of that peak is calculated as the sum of the intensities of the two or more peaks. For example, if there are two peaks B, when calculating the ratio, the intensity of peak B is calculated as the sum of the intensities of the two peaks B.

[0038] In this specification, 29 The Si-MAS-NMR spectrum is a spectrum measured using a Solid 400 MHz WB (wide bore) NMR system, and can be measured under the following conditions. MAS(magic angle spinning)rate:14kHz Spectral frequency(sfo1):79.51MHz(29Si) Temperature: ambient temperature 29Si chemical shift reference:TMS(l)at 0ppm Pulse program: 1D Hahn-echo Spectral width (sw): 100kHz Acquisition time: 40ms Carrier frequency(o1p)at -40ppm Pulse length (p1): 3 μs Recycle delay (d1): 60s Number of scans: 1k~5k

[0039] Select "Gaussian / Lorentzian" as the fitting model for waveform analysis measured by the above method. The parameters used for the analysis are composed of the peak amplitude, peak position, full width at half maximum (FWHM) of the peak, and Gaussian / Lorentzian fraction (xG / (1 - x)L). After setting appropriate initial values, fitting was performed. At this time, xG / (1 - x)L was fixed at 0.3. The fitting conditions used were nParVar = 15, Step = 1, Thresh = 0.001, and fitting was repeated until an appropriate convergence value was reached.

[0040] In this specification, 29 The peak in the Si - MAS - NMR spectrum means a peak having an intensity of 10% or more of the maximum peak intensity, and those with an intensity less than 10% of the maximum peak intensity are not included in the peak.

[0041] The above 29 In the Si - MAS - NMR spectrum, peak A within the range of chemical shift values from 20 ppm to - 15 ppm means the peak of silicon carbide (Si - C) in which silicon and carbon are covalently bonded, and peak B within the range of - 20 ppm to - 100 ppm may mean the peak of elemental Si itself or silicon oxide. The component represented by the peak B can be represented by SiOx (x is 0 or more and less than 2). For example, since Si itself is a material that shows a peak around - 79 ppm, when the peak B appears around - 89 ppm or so, it can be determined as Si or SiOx.

[0042] The silicon - carbon composite 29 In the Si - MAS - NMR spectrum, it further has a peak C within the range of chemical shift values from - 110 ppm to - 140 ppm. This peak C means the presence of SiO2. The peak C has technical significance in that it can improve the capacity characteristics of the battery by making the ratio of (B + C) / A have a specific value.

[0043] The inventors have revealed that peaks B and C are advantageous for the development of battery capacity, and that peak A affects the improvement of aqueous processability. They have also revealed that when the intensity ratio of these peaks is within a specific range, both battery capacity and aqueous processability can be improved. For example, the ratio of the sum of the intensities of peaks B and C to the intensity of peak A ((B+C) / A) is 3 or more and less than 4. When the ratio is within this range, the battery exhibits excellent capacity and efficiency characteristics, and can demonstrate excellent discharge capacity as a superior silicon-based active material. Furthermore, when the ratio is within this range, gas generation during the aqueous process is reduced, the decomposition of components such as cellulose-based binders used in the aqueous process is prevented, phase stability is maintained, and a decrease in slurry viscosity can be prevented.

[0044] According to one embodiment, the silicon-carbon composite can be represented as a Si / C-based active material. In this specification, the silicon-carbon composite is a composite of Si and C, and is distinguished from silicon carbide itself, which is represented as SiC. The silicon carbide does not react electrochemically with lithium, and all its properties, such as lifetime, can be measured to zero.

[0045] In this specification, the silicon-carbon composite is a composite of Si and C, where Si and C (e.g., graphite) are present. For example, the peaks of Si and C can be observed by elemental analysis methods such as XRD or NMR. In this specification, the silicon-carbon composite can be represented as Si / C. The silicon-carbon composite may optionally contain additional components. For example, the silicon-carbon composite may contain silicon carbide represented as SiC. If the silicon-carbon composite contains silicon carbide, its content is 3% by weight or less. The silicon-carbon composite may exist in a crystalline, amorphous, or mixed state. For example, the C in the silicon-carbon composite may exist in an amorphous state.

[0046] According to one embodiment of the present invention, the carbon may be present in an amount of 38 to 50 parts by weight based on 100 parts by weight of the silicon carbon composite. Specifically, the carbon may be present in an amount of 38 to 45 parts by weight, or 38 to 43 parts by weight, based on 100 parts by weight of the silicon carbon composite.

[0047] If the amount of carbon by weight is less than the range, the exposure of silicon on the surface of the silicon-carbon composite increases, making it more likely that side reactions with water will occur, resulting in poor water-based processability. If the amount exceeds the range, the amount of silicon by weight is relatively small, and the target volume cannot be achieved.

[0048] According to one embodiment, the silicon-carbon composite may consist of porous carbon-based particles and particles having silicon provided in at least a portion of the interior and surface of the porous carbon-based particles; or it may consist of porous silicon-based particles and particles having carbon provided in at least a portion of the interior and surface of the porous silicon-based particles.

[0049] According to one embodiment, the silicon-carbon composite is a particle having porous carbon-based particles and silicon provided in at least part of the interior and surface of the porous carbon-based particles. The silicon can be formed by depositing silicon onto the porous carbon-based particles using silane gas. If necessary, a carbon layer may be further formed on the surface of the silicon-carbon composite. The carbon layer imparts conductivity and can improve the initial efficiency, life characteristics, and capacity characteristics of the secondary battery. The total weight of the carbon layer may be 5% to 40% by weight based on 100% by weight of the silicon-carbon composite particles. The carbon layer may contain at least one of amorphous carbon and crystalline carbon.

[0050] According to one embodiment, the silicon-carbon composite may be manufactured by the steps of: heat-treating silicon oxide powder to perform a disproportionation reaction; etching the heat-treated silicon oxide powder with an etching agent; pulverizing the etched silicon oxide powder to obtain porous silicon particles; and reacting the porous silicon particles with a carbon compound to form a carbon layer on the surface of the porous silicon particles.

[0051] According to another embodiment, the silicon-carbon composite may be manufactured by the steps of: depositing silicon onto porous carbon particles by chemical vapor deposition (CVD); and forming a carbon layer on the surface of the silicon-deposited porous carbon particles.

[0052] According to one embodiment, the silicon-carbon composite may consist of porous silicon-based particles and particles having carbon provided in at least part of the interior and surface of the porous silicon-based particles. This can be formed by etching silicon oxide to form porous silicon-based particles, such as a Si matrix, and then coating them with carbon. The carbon may be as described above regarding the carbon layer.

[0053] For example, the porous silicon-based particles may be manufactured by a process in which silicon oxide (e.g., SiO) is phase-separated into Si and silicon dioxide (SiO2) by heat treatment, and then etched with an etching agent such as HF. When the silicon oxide is heat-treated, the size of the Si crystal grains corresponding to peak B can be controlled by a disproportionation reaction (900°C to 1400°C). This allows for adjustment of the ratio between peaks A, B, and C mentioned above.

[0054] According to one embodiment, the silicon-carbon composite has a specific surface area of ​​0.5 m² as measured by the BET method. 2 / g~10m 2 It may also be / g, and the stomatal volume is 0.005 cm³. 3 / g~0.03cm 3 The pore size may be 10 nm to 20 nm, and the pore size measured by the BET method may be 10 nm to 20 nm. The silicon-carbon composite has a pore volume of 0.005 cm³ measured by mercury osmosis. 3 / g~0.03cm 3 / g is also acceptable.

[0055] According to one embodiment, the silicon-carbon composite may have a D90 particle size of 5 μm to 15 μm, a D50 particle size of 1 μm to 10 μm, a Dmin of 1 μm to 3 μm, and a Dmax of 17 μm to 23 μm. In this specification, the average particle size (D 50 The average particle size (D) can be defined as the particle size corresponding to 50% of the cumulative volume in the particle size distribution curve. 50 The particle size can be measured, for example, using the laser diffraction method. This laser diffraction method can generally measure particle sizes from the submicron region to several millimeters in size, and can obtain highly reproducible and high-resolution results.

[0056] One embodiment provides a negative electrode active material containing a silicon-carbon composite according to the embodiment described above.

[0057] One embodiment provides a negative electrode composition comprising a negative electrode active material, a binder, and a conductive material according to the embodiment described above.

[0058] According to one embodiment, the silicon-carbon composite may be included in an amount of 0.1 to 14 parts by weight based on 100 parts by weight of the negative electrode active material, for example, in an amount of 0.1 to 12 parts by weight, or 1 to 10 parts by weight.

[0059] According to one embodiment, the negative electrode active material may further contain a carbon-based active material. The carbon-based active material may be included in an amount of 86 to 99.9 parts by weight, 88 to 99.9 parts by weight, for example, 90 to 99 parts by weight, based on 100 parts by weight of the negative electrode active material contained in the negative electrode composition. The carbon-based active material may contain at least one of natural graphite and artificial graphite. If the carbon-based active material contains both natural graphite and artificial graphite, the weight ratio of the artificial graphite to the natural graphite may be 1:99 to 99:1, for example, 1:9 to 9:1, or 3:7 to 7:3. For example, based on 100 parts by weight of the carbon-based active material, the natural graphite may be 10 to 70 parts by weight and the artificial graphite may be 30 to 90 parts by weight.

[0060] The aforementioned natural graphite refers to graphite that occurs naturally, and examples include flake graphite, scaly graphite, or soil graphite. The advantages of this natural graphite are that it is abundant, inexpensive, has high theoretical capacity and compressible density, and can achieve high output.

[0061] For example, the natural graphite may be spheroidized natural graphite, and may have a spheroidity of 0.9 or higher. For example, the natural graphite may be spheroidized natural graphite and may have a tap density of 0.9 g / cc or higher.

[0062] In this specification, sphericity may be the value obtained by dividing the circumference of a circle having the same area as the projected image by the perimeter of the projected image when the particle is projected. The sphericity can be determined from an SEM image, or it can be measured using a particle shape analyzer, such as the sysmex FPIA3000 manufactured by Malvern. The size of the crystal can also be confirmed by XRD analysis.

[0063] According to one embodiment of the present invention, the negative electrode composition further comprises a binder and a conductive material, wherein the binder may be an aqueous binder.

[0064] The binder may contain at least one selected from the group consisting of polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride, polyacrylonitrile, polymethyl methacrylate, polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, polyacrylic acid, ethylene-propylene-diene monomer (EPDM), sulfonated EPDM, styrene-butadiene rubber (SBR), fluororubber, polyacrylic acid, and substances in which the hydrogen atoms of these substances are substituted with Li, Na, or Ca, and may also contain various copolymers thereof.

[0065] The conductive material is not particularly limited as long as it does not cause a chemical change in the battery and is conductive. For example, graphite such as natural graphite or artificial graphite; carbon black such as acetylene black, Ketjen black, channel black, furnace black, lamp black, and thermal black; conductive fibers such as carbon fibers and metal fibers; conductive tubes such as carbon nanotubes; metal powders such as fluorocarbon, aluminum, and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives may be used.

[0066] According to one embodiment, the aqueous binder may be present in an amount of 1% to 5% by weight, for example about 3% to 4% by weight, based on the solid content of the negative electrode composition, and the conductive material may be present in an amount of 0.1% to 2% by weight, for example about 1% by weight, based on the solid content of the negative electrode composition.

[0067] One embodiment of the present invention provides a negative electrode comprising the negative electrode composition according to the embodiment described above.

[0068] Specifically, the negative electrode may include a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector. The negative electrode active material layer includes the negative electrode composition according to the embodiments described above.

[0069] The negative electrode active material layer may be formed by applying a negative electrode slurry containing the aforementioned negative electrode composition to at least one surface of a negative electrode current collector, drying it, and rolling it.

[0070] The negative electrode current collector is not particularly limited, as long as it does not cause a chemical change in the battery and is conductive. For example, the current collector may be made of copper, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel with a surface treatment of carbon, nickel, titanium, silver, etc. Specifically, transition metals that readily adsorb carbon, such as copper and nickel, may be used as the current collector. The thickness of the current collector may be 6 μm to 20 μm, but is not limited thereto.

[0071] The negative electrode slurry may contain a solvent for forming the negative electrode slurry. Specifically, the solvent for forming the negative electrode slurry may contain at least one selected from the group consisting of distilled water, ethanol, methanol, and isopropyl alcohol, specifically distilled water, in order to facilitate the dispersion of the components.

[0072] One embodiment of the present invention provides a lithium secondary battery including a negative electrode, a positive electrode, and a separator according to the embodiment described above.

[0073] The positive electrode may include a positive electrode current collector and a positive electrode active material layer formed on the positive electrode current collector and containing the positive electrode active material.

[0074] In the positive electrode, the positive electrode current collector is not particularly limited as long as it does not cause a chemical change in the battery and is conductive. For example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel with a surface treatment of carbon, nickel, titanium, silver, etc. may be used. The positive electrode current collector may also have a thickness of 3 μm to 500 μm, and fine irregularities may be formed on the surface of the current collector to increase the adhesion strength of the positive electrode active material. For example, the positive electrode current collector may be used in various forms such as film, sheet, foil, mesh, porous material, foam, or nonwoven fabric.

[0075] The positive electrode active material may be a commonly used positive electrode active material. Specifically, the positive electrode active material may be a layered compound such as lithium cobalt oxide (LiCoO2) or lithium nickel oxide (LiNiO2), or a compound substituted with one or more transition metals; lithium iron oxide such as LiFe3O4; or a compound with the chemical formula Li 1+c1 Mn 2-c1 Lithium manganese oxides such as O4 (0 ≤ c1 ≤ 0.33), LiMnO3, LiMn2O3, LiMnO2; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, V2O5, Cu2V2O7; chemical formula LiNi 1-c2 Ni-site type lithium nickel oxide represented as Mc2O2 (where M is at least one selected from the group consisting of Co, Mn, Al, Cu, Fe, Mg, B, and Ga, satisfying 0.01 ≤ c2 ≤ 0.3); chemical formula LiMn 2-c3 Lithium manganese composite oxides represented as Mc3O2 (where M is at least one selected from the group consisting of Co, Ni, Fe, Cr, Zn, and Ta, satisfying 0.01 ≤ c3 ≤ 0.1) or Li2Mn3MO8 (where M is at least one selected from the group consisting of Fe, Co, Ni, Cu, and Zn); examples include, but are not limited to, LiMn2O4 in which part of the Li in the chemical formula is substituted with an alkaline earth metal ion. The positive electrode may be Li metal.

[0076] The positive electrode active material layer may also include a positive electrode conductive material and a positive electrode binder, along with the positive electrode active material described above.

[0077] In this case, the positive electrode conductive material is used to impart conductivity to the electrode, and can be used without particular limitation as long as it has electronic conductivity without causing a chemical change in the battery that is constructed. Specific examples include graphite such as natural graphite or artificial graphite; carbon-based materials such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, and carbon fiber; metal powders or metal fibers such as copper, nickel, aluminum, and silver; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives. One of these alone or a mixture of two or more may be used.

[0078] Furthermore, the positive electrode binder plays a role in improving the adhesion between positive electrode active material particles and the adhesion between the positive electrode active material and the positive electrode current collector. Specific examples include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene-butadiene rubber (SBR), fluororubber, or various copolymers thereof, and one of these alone or a mixture of two or more may be used.

[0079] The separator separates the negative and positive electrodes and provides a pathway for lithium ions to move. Generally, any separator commonly used in secondary batteries can be used without particular limitations, but it is especially preferable that it has low resistance to ion movement in the electrolyte and excellent electrolyte moisture absorption capacity. Specifically, porous polymer films, such as porous polymer films made from polyolefin polymers like ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer, and ethylene / methacrylate copolymer, or laminated structures of two or more layers thereof may be used. Alternatively, ordinary porous nonwoven fabrics, such as nonwoven fabrics made from high-melting-point glass fibers or polyethylene terephthalate fibers, may be used. Furthermore, to ensure heat resistance or mechanical strength, coated separators containing ceramic components or polymeric substances may be used, and they may be selectively used as single-layer or multi-layer structures.

[0080] The lithium secondary battery may further contain an electrolyte. Examples of the electrolyte include, but are not limited to, organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel-type polymer electrolytes, solid inorganic electrolytes, and molten inorganic electrolytes that can be used in the manufacture of lithium secondary batteries.

[0081] Specifically, the electrolyte may include a non-aqueous organic solvent and a metal salt.

[0082] As the non-aqueous organic solvent, for example, aprotic organic solvents such as N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, γ-butyrolactone, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolane, formamide, dimethylformamide, dioxolane, acetonitrile, nitromethane, methyl formate, methyl acetate, triester phosphate, trimethoxymethane, dioxolane derivatives, sulfolane, methylsulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivatives, tetrahydrofuran derivatives, ether, methyl propionate, and ethyl propionate may be used.

[0083] In particular, among the carbonate-based organic solvents, ethylene carbonate and propylene carbonate, which are cyclic carbonates, can be preferably used as high-viscosity organic solvents because they have high dielectric constants and dissociate lithium salts well. Furthermore, when such cyclic carbonates are mixed with linear carbonates with low viscosity and low dielectric constant, such as dimethyl carbonate and diethyl carbonate, in appropriate proportions, an electrolyte with high electrical conductivity can be produced, making them even more preferable.

[0084] As the metal salt, a lithium salt may be used, and the lithium salt is a substance that is easily soluble in the non-aqueous electrolyte, for example, as the anion of the lithium salt, F - Cl - , I - NO3 - , N(CN)2 - BF4 - ClO4 - PF6 - (CF3)2PF4 - (CF3)3PF3 - (CF3)4PF2 - (CF3)5PF - (CF3)6P - CF3SO3 - CF3CF2SO3- , (CF3SO2)2N - , (FSO2)2N - CF3CF2(CF3)2CO - (CF3SO2) 2CH - (SF5)3C - , (CF3SO2)3C - CF3(CF2)7SO3 - CF3CO2 - CH3CO2 - SCN - , and (CF3CF2SO2)2N - You may use one or more selected from the group consisting of the following:

[0085] In addition to the components of the electrolyte, the electrolyte may further contain one or more additives for purposes such as improving the battery's lifespan, suppressing the decrease in battery capacity, and improving the battery's discharge capacity, such as haloalkylene carbonate compounds like difluoroethylene carbonate, pyridine, triethyl phosphite, triethanolamine, cyclic ethers, ethylenediamine, n-glyme, hexamethyl phosphate triamide, nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinone, N,N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salts, pyrrole, 2-methoxyethanol, or aluminum trichloride.

[0086] According to another embodiment of the present invention, a battery module and a battery pack including the secondary battery as a unit cell are provided. Since the battery module and battery pack include the secondary battery having high capacity, high rate characteristics and cycle characteristics, they can be used as a power source for medium to large devices selected from the group consisting of electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, and power storage systems. [Examples]

[0087] The following describes the Specification in detail with reference to examples. However, the examples relating to this Specification may be modified into various other forms, and the scope of this application should not be construed as being limited to the examples described below. The examples of this application are provided to give a more complete explanation of this Specification to a person of average knowledge in the industry.

[0088] <Example 1> (1) Manufacturing of silicon-carbon composites 20 g of SiOx (x=0.9~1) powder was subjected to a disproportionation reaction of SiO by heat treatment at 1,200°C under an inert atmosphere of argon gas.

[0089] Ten g of the processed SiOx (x=0.9~1) powder was dispersed in distilled water, and then 10 ml of a 30 wt% HF aqueous solution was gradually added while stirring at a speed of 500 Rpm. The SiO powder obtained by the above process was etched for 2 hours. After the above manufacturing process, the pH of the powder was made neutral by filtration or washing. After obtaining the powder, porous silicon was produced by drying it under vacuum at 130°C for 6 hours. Subsequently, the particle size was ground in a mortar and pestle so that the D50 was 4 μm~6 μm. Under an inert gas atmosphere of Ar, acetylene (C2H2) was used in a CVD apparatus to etch 10 -1 A silicon-carbon composite containing a carbon coating layer was produced by reacting porous silicon at 720°C for approximately 5 hours at a rate of 1 L / min using a Torr detector to form a carbon layer on the surface. The NMR analysis results are shown in Figure 1. According to Figure 1, peaks corresponding to peaks A, B, and C appeared, and the ratio of (B+C) / A was measured to be 3.3.

[0090] (2) Manufacturing of the negative electrode A negative electrode slurry was prepared by mixing a negative electrode active material containing the silicon-carbon composite and graphite produced above in a weight ratio of 9:91; a conductive material containing carbon black and SWCNTs; and a binder containing carboxymethyl cellulose (CMC) and styrene-butadiene rubber (SBR) in a weight ratio of 95.3:1:3.6, with an appropriate amount of distilled water added and mixed so that the total solid content was approximately 46% by weight.

[0091] The negative electrode slurry was applied to a 20 μm thick Cu metal thin film and then dried in circulating air at 60°C. Next, after rolling, it was dried in a vacuum oven at 130°C for about one day, and then rolled to 1.4875 cm². 2 The negative electrode was manufactured by punching out a circular shape.

[0092] (3) Manufacturing of secondary batteries 1.7671cm 2 A die-cut Li metal thin film was used as the positive electrode. A porous polyethylene separator was interposed between the positive and negative electrodes, and an electrolyte solution containing 1M LiPF6 with additives dissolved in a mixed solution of EMC (ethyl methyl carbonate) and EC (ethylene carbonate) in a 7:3 ratio was injected to produce a Li coin half-cell.

[0093] <Example 2> A silicon-carbon composite was produced in the same manner as in Example 1, except that the disproportionation reaction was carried out at a temperature of 1,150°C and acetylene (C2H2) was flowed at 700°C to form a carbon layer. The NMR analysis results of the active material produced by the method of Example 2 are shown in Figure 2. According to Figure 2, peaks corresponding to peaks A, B, and C appeared, and the ratio of (B+C) / A was measured to be 3.5.

[0094] Using the silicon-carbon composite described above, a negative electrode and a secondary battery were manufactured in the same manner as in Example 1.

[0095] Figure 8 shows the waveform analysis results of the NMR analysis in Figure 2. The silicon-carbon composite of Example 2 has peaks (1) to (6), of which (1) corresponds to peak A, (2), (4), (5), and (6) correspond to peak B, and (3) corresponds to peak C. When calculating the ratio (B+C) / A, B was calculated as the sum of the intensities of peaks (2), (4), (5), and (6).

[0096] <Example 3> (1) Production of porous carbon particles A 0.5 M sucrose aqueous solution was placed in an autoclave and reacted at 180°C for 24 hours to synthesize spherical particles. After the reaction, the resulting carbon-based particles were washed 3 to 5 times with ethanol. The carbon-based particles, dried at 100°C for 24 hours or more, were mixed with KOH in a 1:3 parts by weight ratio, and the mixture was heated in a nitrogen atmosphere at 800°C for 3 hours to expand the pores. After washing with distilled water, porous carbon particles were produced by drying at 80°C for 12 hours or more.

[0097] (2) Silicon deposition and carbon composite formation Silane gas was injected into the reactor by chemical vapor deposition (CVD) at a flow rate of approximately 40 mL / min to 110 mL / min, and the reactor was treated for approximately 3 hours at a temperature below 800°C with a heating condition of 10°C / min to 15°C / min to produce a negative electrode active material in the form of silicon deposited on porous carbon particles. Ethylene (C2H4) gas was then injected into the silicon-deposited porous carbon particles using a CVD apparatus under an inert gas (Ar) atmosphere for 10 minutes. -1 A silicon-carbon composite was produced by reacting it with torr at 700°C at a rate of 1 L / min for approximately 5 hours to form a carbon layer on the surface of the silicon-based active material. As shown in Figure 3, NMR analysis of the silicon-carbon composite produced in this way revealed peaks corresponding to peaks A, B, and C, and the ratio of (B+C) / A was confirmed to be 3.4.

[0098] (3) Manufacturing of negative electrodes and secondary batteries The negative electrode and secondary battery were manufactured in the same manner as in Example 1, except that the silicon-carbon composite and graphite were used as the negative electrode active material in a ratio of 12:88.

[0099] <Comparative Example 1> (1) Method for producing silicon oxide containing magnesium Si and SiO2 were mixed in a 1:1 molar ratio in crucible 1, and then heated to a sublimation temperature of 1400°C. In crucible 2, metallic magnesium was separately heated and evaporated between 600 and 1000°C. Both crucibles were under reduced pressure of 0.1 torr. The vapor-state mixtures containing Mg obtained from crucibles 1 and 2 were reacted for 6 hours, and then condensed into a solid phase in a vacuum at 800°C. The silicon-based active material produced by the above method was pulverized using a ball mill for about 3 to 4 hours to produce particles with a D50 of 6 μm. Subsequently, under an inert gas atmosphere of Ar, methane (CH4) was added using a CVD apparatus. -1 A silicon oxide containing magnesium was produced by reacting particles with a torr at a rate of 1 L / min for approximately 5 hours to form a carbon layer on the surface of the silicon-based active material. The Mg content in the powder was analyzed by ICP-MS and measured to be 8% by weight.

[0100] As shown in Figure 4, NMR analysis of the silicon oxide produced by this method revealed peaks corresponding to peaks B and C, but no peak A. Since peak A was absent, it was impossible to measure the ratio of (B+C) / A.

[0101] The negative electrode and secondary battery were manufactured in the same manner as in Example 1, except that the silicon-carbon composite and graphite were used as the negative electrode active material in a ratio of 15:85.

[0102] <Comparative Example 2> In Comparative Example 1, the active material was produced using the same process as in Comparative Example 1, except that the metallic magnesium in the second crucible was removed. As shown in Figure 4, the NMR analysis of the silicon oxide produced by this method showed peaks corresponding to peaks B and C, but no peak A appeared. Since peak A was absent, it was impossible to measure the ratio of (B+C) / A.

[0103] The negative electrode and secondary battery were manufactured in the same manner as in Example 1, except that the silicon-carbon composite and graphite were used as the negative electrode active material in a ratio of 12:88.

[0104] <Comparative Example 3> In Example 3, the same procedure was followed, except that the CVD carbon coating process using ethylene (C2H4) on porous carbon was carried out at a temperature of 500°C. As shown in Figure 5, the silicon-carbon composite produced in this way showed peaks corresponding to peaks B and C in NMR analysis, but no peak corresponding to peak A appeared, making it impossible to confirm the ratio of (B+C) / A.

[0105] Using the silicon-carbon composite described above, a negative electrode and a secondary battery were manufactured in the same manner as in Example 1.

[0106] <Comparative Example 4> A mixed gas of 1 L / min of silane, 3 L / min of acetylene, and 1 L / min of argon was introduced into the deposition chamber of a fluidized bed reactor at a temperature of 700°C and a pressure of 1 atm. A silicon-carbon composite was obtained from the collection chamber of the fluidized bed reactor. NMR analysis of the silicon-carbon composite produced in this way revealed peaks corresponding to peaks A, B, and C, and the ratio of (B+C) / A was confirmed to be 2.8.

[0107] The negative electrode and secondary battery were manufactured in the same manner as in Example 1, except that the silicon-carbon composite and graphite were used as the negative electrode active material in a ratio of 11:89.

[0108] <Comparative Example 5> 1 kg of silicon powder and 1 kg of silica powder were placed in a vacuum reactor. First, a vacuum of less than 0.1 torr was created, then the mixture was heated to 1400°C to turn the raw materials into vapor. Simultaneously, a benzene solution was gradually passed through to rapidly vaporize the benzene, which was then completely mixed with the silicon / silica mixture vapor. The mixed vapor was then cooled and deposited on a water-cooled substrate, and the material was pulverized to obtain silicon oxide in which carbon atoms were uniformly inserted at the atomic level. Subsequently, the pulverized material was carbon coated, and 1 kg of the material was placed in a rotary furnace. After heating to 1000°C under an argon atmosphere as a protective gas, argon gas and a mixed gas of propylene and methane in a 1:1 volume ratio were introduced to perform vapor-phase coating, where the volume ratio of propylene to methane was 2:3. The temperature was maintained for 1 hour, and then the organic gas supply source was shut off to allow it to cool, resulting in silicon oxide in which internal carbon atoms were uniformly dispersed at the atomic level. As shown in Figure 4, the silicon-carbon composite produced in this manner did not exhibit a peak corresponding to peak A in NMR analysis, and the ratio of (B+C) / A could not be confirmed.

[0109] The negative electrode and secondary battery were manufactured in the same manner as in Example 1, except that the silicon-carbon composite and graphite were used as the negative electrode active material in a ratio of 12:88.

[0110] <Comparative Example 6> In Example 3, the same method was used as in Example 3, except that the silane gas injection time was 5 hours. As shown in Figure 6, NMR analysis of the silicon-carbon composite produced by this method revealed peaks corresponding to peaks A, B, and C, and the ratio of (B+C) / A was measured to be 2.7.

[0111] Using the silicon-carbon composite described above, a negative electrode and a secondary battery were manufactured in the same manner as in Example 1.

[0112] <Comparative Example 7> In the process of expanding the pores of porous carbon, carbon-based particles and KOH were mixed in a ratio of 1:3.5 parts by weight and heat-treated for 5 hours. The procedure was the same as in Example 3, except that the reaction was carried out at 650°C for 8 hours at a rate of 300 ml / min under the conditions of the silane gas deposition process. As shown in Figure 7, NMR analysis of the silicon-carbon composite produced in this way revealed peaks corresponding to peaks A, B, and C, and the ratio of (B+C) / A was confirmed to be 2.6.

[0113] The negative electrode and secondary battery were manufactured in the same manner as in Example 1, except that the silicon-carbon composite and graphite were used as the negative electrode active material in a ratio of 10:90.

[0114] Table 1 below shows the peak ratios identified by NMR analysis of the silicon-based active materials produced in the examples and comparative examples.

[0115] Furthermore, Table 2 below shows the results of measuring the C content, O content, and Si content of each example and comparative example using a carbon-sulfur analyzer (CS Analyzer) and an oxygen-nitrogen-hydrogen analyzer (ONH Analyzer), as well as the percentage of graphite contained in the negative electrode active material.

[0116] [Battery performance evaluation] The manufactured batteries were subjected to charging and discharging tests to evaluate their discharge capacity, initial efficiency, and capacity retention rate, and these results are shown in Table 1 below.

[0117] The first and second cycles were charged and discharged at 0.1C, and from the third to the 49th cycle, they were charged and discharged at 0.5C. The 50th cycle ended in a charged state (lithium was in the negative electrode). Charging conditions: CC (constant current) / CV (constant voltage) (5mV / 0.005C current cut-off) Discharge condition: CC (constant current) condition 1.5V

[0118] The discharge capacity (mAh / g) and initial efficiency (%) were derived from the results of a single charge-discharge cycle. Specifically, the initial efficiency (%) was derived by the following calculation. Initial efficiency (%) = (Discharge capacity per cycle / Charge capacity per cycle) × 100

[0119] The capacity retention rates were derived using the following calculations. Capacity retention rate (%) = (49 discharge capacity / 1 discharge capacity) × 100

[0120] [Evaluation of water-based processability] 1) Evaluation of processability (Shear viscosity) characteristics As part of the process evaluation, the change in shear viscosity at a shear rate of 1 Hz for the slurries produced in the examples and comparative examples was measured and is shown in Table 1 below. Specifically, the change in shear viscosity (%) was derived using the following formula. Change in shear viscosity (%) = ((Shear viscosity of slurry after 48 hours - Shear viscosity of slurry immediately after mixing) / Shear viscosity of slurry immediately after mixing) × 100

[0121] 2) Gas generation point: After placing 20g of slurry into a 10 x 15cm aluminum pouch and vacuum sealing it, the volume change is measured using Archimedes' principle. The point at which a volume change of 2mL or more occurs at 60°C is defined as the gas generation point.

[0122] [Table 1] [Table 2]

[0123] Examples 1 to 3 involved applying materials to batteries that had peaks corresponding to peaks A, B, and C, and whose peak ratios met the range of the present invention. As shown in Table 1, these materials exhibited a certain level of effectiveness in discharge capacity, initial efficiency, and capacity retention, while viscosity changes and gas generation remained below a certain level.

[0124] In Example 3, the effect in terms of aqueous processability was inferior to that of Examples 1 and 2. This is because silicon was deposited not only on the voids of the porous carbon but also on the surface, which is disadvantageous in terms of aqueous processability. However, it can be confirmed that it is superior in terms of volume and aqueous processability compared to Comparative Examples 3, 6, and 7, which were manufactured using the same method of depositing silicon onto porous carbon but did not meet the peak ratio requirement.

[0125] In contrast, Comparative Examples 1 to 7 failed to satisfy the aforementioned peak ratio and therefore showed inferior performance in terms of volume and aqueous processability. Specifically, Comparative Examples 1, 2, and 5 did not include the process of depositing carbon onto porous silicon, so an appropriate amount of SiC was not produced, and as a result, the aqueous processability was poor due to reaction with the electrolyte.

[0126] Comparative Example 4 had an insufficient carbon content in the silicon-carbon composite, resulting in a lack of SiC on the surface. Consequently, it could not effectively prevent reaction with water and had poor aqueous processability.

Claims

1. ２９ A silicon-carbon composite having a Si-MAS-NMR spectrum in which peak A is located in the range of 20 ppm to -15 ppm, peak B in the range of -20 ppm to -100 ppm, and peak C in the range of -110 ppm to -140 ppm, and the ratio of the sum of the intensities of peak B and peak C to the intensity of peak A ((B + C) / A) is 3 or more and less than 4.

2. The silicon-carbon composite according to claim 1, wherein the silicon-carbon composite contains carbon, and the carbon is present in an amount of 38 to 50 parts by weight based on 100 parts by weight of the silicon-carbon composite.

3. The silicon-carbon composite according to claim 1, wherein the silicon-carbon composite comprises porous carbon-based particles and particles having a silicon-based material provided in at least a portion of the interior and surface of the porous carbon-based particles; or porous silicon-based particles and particles having carbon provided in at least a portion of the interior and surface of the porous silicon-based particles.

4. The silicon-carbon composite according to claim 1, further comprising a carbon layer on the surface of the silicon-carbon composite, wherein the total weight of the carbon layer is 5% to 40% by weight based on 100% by weight of the silicon-carbon composite particles.

5. The pore volume of the silicon-carbon composite is 0.005 cm³. ３ / g ~ 0.03cm ３ The silicon-carbon composite according to claim 1, wherein the concentration is / g.

6. The silicon-carbon composite according to claim 1, wherein the pore size of the silicon-carbon composite is 10 nm to 20 nm.

7. The silicon-carbon composite according to claim 1, wherein the D90 particle size is 5 μm to 15 μm, the D50 particle size is 1 μm to 10 μm, Dmin is 1 μm to 3 μm, and Dmax is 17 μm to 23 μm.

8. A negative electrode active material comprising the silicon carbon composite according to any one of claims 1 to 7.

9. The negative electrode active material according to claim 8, wherein the silicon-carbon composite is included in an amount of 0.1 to 14 parts by weight based on 100 parts by weight of the negative electrode active material.

10. The negative electrode active material according to claim 8, further comprising a carbon-based active material, wherein the carbon-based active material is present in an amount of 86 parts by weight or more and 99.9 parts by weight or less based on 100 parts by weight of the negative electrode active material.

11. A negative electrode composition comprising the negative electrode active material, binder, and conductive material according to claim 8.

12. The negative electrode composition according to claim 11, wherein the negative electrode active material further comprises a carbon-based active material.

13. A negative electrode comprising the negative electrode composition described in claim 11.

14. A lithium secondary battery comprising the negative electrode, positive electrode, and separator described in claim 13.

15. A battery module comprising the lithium secondary battery described in claim 14.

16. A battery pack comprising the lithium secondary battery described in claim 14.

17. A battery pack comprising the battery module described in claim 15.

18. A step in which silicon oxide powder is heat-treated to carry out a disproportionation reaction; A step of etching the heat-treated silicon oxide powder with an etching agent; The step of grinding the etched silicon oxide powder to obtain porous silicon particles; and The step of reacting the porous silicon particles with a carbon compound to form a carbon layer on the surface of the porous silicon particles. A method for producing a silicon carbon composite containing, The aforementioned silicon-carbon composite is ２９ A method for producing a silicon-carbon composite, wherein the Si-MAS-NMR spectrum has a peak A in the range of 20 ppm to -15 ppm, a peak B in the range of -20 ppm to -100 ppm, and a peak C in the range of -110 ppm to -140 ppm, and the ratio of the sum of the intensities of peak B and peak C to the intensity of peak A ((B + C) / A) is 3 or more and less than 4.

19. The step of depositing silicon onto porous carbon particles by chemical vapor deposition (CVD); and The step of forming a carbon layer on the surface of porous carbon particles on which the silicon has been deposited. A method for producing a silicon carbon composite containing, The aforementioned silicon-carbon composite is ２９ A method for producing a silicon-carbon composite, wherein the Si-MAS-NMR spectrum has a peak A in the range of 20 ppm to -15 ppm, a peak B in the range of -20 ppm to -100 ppm, and a peak C in the range of -110 ppm to -140 ppm, and the ratio of the sum of the intensities of peak B and peak C to the intensity of peak A ((B + C) / A) is 3 or more and less than 4.

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