Silicon-carbon composite, anode active material, anode and secondary battery

Abstract

The present invention relates to a silicon-carbon composite, an anode active material comprising same, an anode composition, an anode, a lithium secondary battery, a battery module and a battery pack, the silicon-carbon composite having, when etching is performed with an argon (Ar) ion beam at an energy of 1,000 eV for 5,000 seconds, and then XPS analysis is performed, a ratio of an Si element proportion measured by Si2p spectrum to an N element proportion measured by N1s spectrum of 35-200.

Description

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

[0001] This application claims the benefit of the filing date of Korean Patent Application No. 10-2024-0144985 filed with the Korean Intellectual Property Office on October 22, 2024, the entire contents of which are incorporated herein.

[0002] The present application relates to a silicon carbon composite, a negative electrode active material comprising the same, a negative electrode comprising the negative electrode active material, and a secondary battery comprising the negative electrode.

[0003] Recently, accompanied by the rapid proliferation of battery-powered electronic devices such as mobile phones, laptop computers, electric vehicles, power tools, and vacuum cleaners, the demand for rechargeable batteries that are small and lightweight yet possess relatively high capacity and / or high output is rapidly increasing. Lithium-ion batteries are gaining prominence as power sources for electronic devices due to their lightweight nature and high energy density. Accordingly, active research and development efforts are underway to improve the performance of lithium-ion batteries.

[0004] The performance of lithium-ion batteries can be achieved through innovation in each of the key materials, such as major components like cathode materials, anode materials, separators, and electrolytes.

[0005] One embodiment of the present invention aims to provide a silicon carbon composite, a negative electrode active material, a negative electrode, and a lithium secondary battery that have excellent capacity and / or efficiency characteristics and can be used as a negative electrode active material of high energy density.

[0006] In one embodiment of the present invention, when etched with an argon (Ar) ion beam at an energy of 1,000 eV for 5,000 seconds and then analyzed by XPS, N 1s Si relative to the ratio of N element measured by the spectrum 2p A silicon carbon composite is provided in which the ratio of the proportion of Si elements measured by the spectrum is 35 to 200.

[0007] One embodiment of the present invention provides a negative electrode active material comprising a silicon carbon composite according to the embodiments described above.

[0008] One embodiment of the present invention provides a cathode composition comprising a cathode active material according to the above embodiment.

[0009] One embodiment of the present invention provides a cathode comprising a cathode composition according to the above embodiment.

[0010] One embodiment of the present invention provides a lithium secondary battery comprising a negative electrode, a positive electrode, and a separator according to the above embodiment.

[0011] One embodiment of the present invention provides a battery module including a lithium secondary battery according to the above embodiment.

[0012] One embodiment of the present invention provides a battery pack comprising a battery module according to the above embodiment.

[0013] According to embodiments of the present invention, when XPS analysis is performed after etching with an argon (Ar) ion beam at an energy of 1,000 eV for 5,000 seconds, N 1s Si relative to the ratio of N element measured by the spectrum 2p A lithium secondary battery with improved capacity and / or efficiency can be provided by using a silicon-carbon composite as a negative electrode active material in which the ratio of Si elements measured by the spectrum satisfies a specific value.

[0014] The following drawings attached to this specification illustrate preferred embodiments of the present invention and serve to further enhance understanding of the technical concept of the present invention together with the detailed description of the invention provided below; therefore, the present invention should not be interpreted as being limited only to the matters described in such drawings.

[0015] FIG. 1 is a schematic diagram showing the structure of a lithium secondary battery according to one embodiment of the present invention.

[0016] FIG. 2 is a schematic diagram showing a negative electrode of a lithium secondary battery according to one embodiment of the present invention.

[0017] Figure 3 shows the spectra analyzed by XPS after etching the silicon carbon composites of Examples 1 to 4 for 5,000 seconds.

[0018] Figure 4 shows the spectra analyzed by XPS after etching the silicon carbon composites of Comparative Examples 1 to 5 for 5,000 seconds.

[0019] In parts of the attached drawings, corresponding components are given the same reference numerals. Those skilled in the art understand that the drawings are intended to illustrate elements simply and clearly and are not necessarily drawn to scale. For example, to aid in understanding various embodiments, the dimensions of some elements depicted in the drawings may be exaggerated compared to others. Additionally, elements of known technology that are useful or essential in commercially viable embodiments may often be omitted so as not to hinder the spirit of the various embodiments of the present invention.

[0020] The present invention will be described in more detail below to aid in understanding. The present invention may be implemented in various different forms and is not limited to the embodiments described herein.

[0021] In this specification, terms such as “comprising,” “comprising,” or “having” are intended to specify the existence of the implemented features, numbers, steps, components, or combinations thereof, and should be understood as not excluding in advance the existence or addition of one or more other features, numbers, steps, components, or combinations thereof.

[0022] Furthermore, when it is said that a part, such as a layer, is "above" or "on" another part, this includes not only the case where it is "directly above" the other part, but also the case where there is another part in between. Conversely, when it is said that a part is "directly above" another part, it means that there is no other part in between. Also, saying that a part is "above" or "on" a reference part means that it is located above or below the reference part, and it does not necessarily mean that it is located "above" or "on" facing the opposite direction of gravity.

[0023] Terms or words used in this specification should not be interpreted as being limited to their ordinary or dictionary meanings, but should be interpreted in a meaning and concept consistent with the technical spirit of the invention, based on the principle that the inventor can appropriately define the concept of the terms to best describe his invention.

[0024] The singular expressions of terms used in this specification include the plural expressions unless the context clearly indicates otherwise.

[0025] Embodiments of the present invention are described in detail below. However, embodiments of the present invention may be modified in various forms, and the scope of the present invention is not limited to the embodiments described below.

[0026] FIG. 1 is a schematic diagram showing the structure of a lithium secondary battery according to one embodiment of the present invention.

[0027] Referring to FIG. 1, a lithium secondary battery (100) according to one embodiment of the present invention includes a positive electrode (110), a negative electrode (120), a separator (130) interposed between the positive electrode (110) and the negative electrode (120), an electrolyte (140), etc. When charging, lithium ions move from the positive electrode (110) to the negative electrode (120) through the separator (130) (energy storage), and when discharging, lithium ions move from the negative electrode (120) to the positive electrode (110) through the separator (130) to generate electricity. In this process, the positive electrode (110) and the negative electrode (120) each play the role of releasing or receiving lithium ions, electrons move through a wire connecting the positive electrode (110) and the negative electrode (120) to generate an electric current, and lithium ions utilize an electrochemical reaction in which they travel between the positive electrode (110) and the negative electrode (120) through an electrolyte (140).

[0028] The positive electrode (110) and the negative electrode (120) of the lithium secondary battery (100) can each be manufactured by forming an active material layer containing a positive active material and a negative active material, respectively, on a current collector. Generally, a lithium-containing metal oxide such as LiCoO2 or LiMn2O4 is used as the positive active material for the positive electrode, and a carbon-based active material or a silicon-based active material that does not contain lithium is used as the negative active material for the negative electrode.

[0029] FIG. 2 is a schematic diagram showing a negative electrode (120) of a lithium secondary battery (100) according to one embodiment of the present invention.

[0030] Referring to FIG. 2, the negative electrode (120) of a lithium secondary battery (100) according to one embodiment of the present invention includes a current collector (122) and a negative electrode active material layer (124).

[0031] Batteries using graphite as a negative electrode active material can exhibit a high discharge voltage of 3.6 V, but their low capacity limits the ability to increase energy density. On the other hand, silicon-based active materials are attracting attention as next-generation negative electrode active materials because they possess high capacity and efficiency. Therefore, there is a need to develop silicon-based active materials with high capacity or efficiency characteristics. For example, an active material can be developed that is composed of a silicon-carbon composite containing silicon with high capacity characteristics and a lightweight carbon element capable of mitigating silicon volume expansion.

[0032] Meanwhile, silicon-carbon composite active materials with high capacity, high efficiency, and long lifespan can cause problems with slurry processability, and it is important to improve processability in order to develop high energy density lithium secondary batteries.

[0033] The present invention provides a silicon carbon composite applied to an active material for a negative electrode of a lithium secondary battery (100), which can maintain high capacity and efficiency while improving the processability of the slurry through the introduction of the physical properties of porous carbon and a surface coating layer, and a manufacturing technology for a negative electrode (120) using the same.

[0034] According to one embodiment of the present invention, the silicon carbon composite is a composite of Si and C, wherein Si and C (e.g., graphite) are present respectively. In this specification, the silicon carbon composite may be denoted as Si / C. The silicon carbon composite may consist of Si and C that are not bonded to each other, but may include additional components as needed. For example, the silicon carbon composite may or may not include silicon carbide denoted as SiC. If the silicon carbon composite includes silicon carbide, the content thereof is 3 weight percent or less. The silicon carbon composite may exist in a crystalline, amorphous, or mixed state. According to one example, C in the silicon carbon composite may exist in an amorphous state.

[0035] According to one embodiment, the silicon-carbon composite comprises porous carbon particles and silicon provided on at least a portion of the interior and surface of the porous carbon particles. The silicon may be formed by depositing silicon onto the porous carbon particles using a silane gas. If necessary, a carbon layer may be further formed on the surface of the silicon-carbon composite. Conductivity is imparted by the carbon layer, and the initial efficiency, lifespan characteristics, and battery capacity characteristics of the secondary battery may be improved. The total weight of the carbon layer may be included in an amount of 5% to 40% by weight based on 100% by weight of the total silicon-carbon composite particles. The carbon layer may comprise at least one of amorphous carbon and crystalline carbon.

[0036] As used herein, "about," "approximately," and "substantially" are used to mean a range of figures or degrees or approximations thereof, taking into account inherent manufacturing and material tolerances (e.g., ±5%).

[0037] According to one embodiment, the silicon-carbon composite may be a porous silicon particle and a particle having carbon provided on at least a portion of the interior and surface of the porous silicon particle. This can be formed by etching silicon oxide to form a silicon-based particle with a porous structure, such as a Si matrix, and then coating it with carbon. The carbon may be subject to the description of the carbon layer described above.

[0038] A negative electrode active material comprising a silicon carbon composite according to one embodiment of the present invention can be manufactured in the following manner.

[0039] First, a carbon-based particle precursor is placed in an electric furnace and heated under a nitrogen atmosphere for a certain period of time. Subsequently, the powder obtained from the heating process is mixed with, for example, a mixture of sulfuric acid and nitric acid, stirred at a certain temperature and for a certain period of time, and then centrifuged to obtain a precipitate. The obtained precipitate is then dried to obtain carbon-based particles.

[0040] Examples of the above carbon-based particle precursors may include natural polymers, synthetic polymers, and biomass, and examples may include cellulose powder, polyacrylonitrile (PAN), phenolic resin, melamine resin, or coconut shells, but are not limited thereto, and other materials available to those with ordinary knowledge in the art may also be used without limitation.

[0041] Subsequently, the above-mentioned carbon-based particles are heated in a specific solvent and atmosphere to obtain a porous carbon structure, and the porous carbon structure is dried. Subsequently, the porous carbon structure is treated in a specific atmosphere to produce a silicon carbon composite. The silicon carbon composite is reacted with the silicon carbon composite in an electric furnace by flowing a specific gas, such as acetylene gas, to produce a silicon carbon composite negative electrode active material including a carbon layer on its outermost surface.

[0042] When a silicon-carbon composite for a cathode active material manufactured according to one embodiment of the present invention is analyzed by X-ray Photoelectron Spectroscopy (XPS) after etching with an argon (Ar) ion beam, N 1s Si relative to the ratio of N element measured by the spectrum 2p The ratio of the proportion of Si elements measured by the spectrum is about 35 to 200, and the N 1s The proportion of the N element measured by the spectrum is approximately 0.35 atm% or more based on the total 100 atm% of Si, C, O, and N elements contained in the silicon carbon composite. In this specification, X-ray photoelectron spectroscopy (XPS) is a technique for analyzing the surface chemical composition of a material, which measures the binding energy of photoelectrons emitted from surface atoms by irradiating the surface of a sample with high-energy X-rays. This enables qualitative and quantitative analysis of elements and allows for the identification of the chemical state and environment of each element.

[0043] As described above, the step of etching the surface of the silicon carbon composite with an argon (Ar) ion beam before performing the XPS analysis may be further included. By including the step of etching the surface of the silicon carbon composite with an argon (Ar) ion beam in this manner, the surface layer of the sample, such as the carbon coating layer surrounding the silicon carbon composite, can be removed to analyze the elemental profile of the deeper layer inside the particle.

[0044] In one embodiment of the present invention, the step of etching the surface of the silicon carbon composite with an argon (Ar) ion beam may be a step of etching for 5,000 seconds with an energy of about 1,000 eV. By etching with the above energy and time, the outermost carbon coating layer can be sufficiently removed, thereby ensuring data reliability and maintaining the original properties of the sample, thus preventing errors in interpreting the chemical state of the sample.

[0045] In this specification, N obtained through XPS analysis 1s Spectrum and Si 2p The spectrum is a detection of photoelectrons emitted from the 1s orbital of a nitrogen atom and the 2p orbital of a silicon atom, respectively, which allows for the measurement of the nitrogen and silicon content present on the surface of the cathode active material.

[0046] In this specification, XPS analysis is performed under the following conditions.

[0047] <XPS 분석 조건>

[0048] - X-ray source: Monochromated Al K α (1486.6 eV)

[0049] - X-ray spot size: 400 µm

[0050] - Sputtering gun: Monatomic Ar (energy: 1000 eV, current: low, raster width: 2mm)

[0051] - Etching rate: 0.09 nm / s for Ta2O5

[0052] - Operation Mode: CAE (Constant Analyzer Energy) mode

[0053] - Survey scan: pass energy 200 eV, energy step 1 eV

[0054] - Narrow scan: scanned mode, pass energy 50 eV, energy step 0.1 eV

[0055] - Charge compensation: 0.1V 150μA

[0056] - SF: Al THERMO1

[0057] - ECF: TPP-2M

[0058] - BG subtraction: Smart

[0059] In one embodiment of the present invention, the depth profile of the X-ray photoelectron spectroscopy (XPS) can be measured by proceeding at 0.09 nm / s based on the Ta2O5 sample under an X-ray source of Monochromated Al K α.

[0060] In this specification, peak intensity refers to Si obtained through XPS analysis. 2p It refers to the value obtained by deconvolving the spectrum by peak and fitting it to a 'Gaussian / Lorentzian' model, then integrating the area under the resulting Gaussian function graph.

[0061] In the present specification, peaks may overlap and appear in the shape of a shoulder peak, and two or more peaks may coexist.

[0062] In the present specification, when peaks overlap or coexist, the intensity of the corresponding peak is calculated as the sum of the intensities of two or more peaks.

[0063] In this specification, the content ratio of the elements can be calculated through the following Equation 1.

[0064] [Equation 1]

[0065]

[0066] In Equation 1 above, i represents the type of element to be found, and j represents the type of all elements measured through XPS. Also, C i represents the ratio of the elemental content, and A i represents the area modified by considering the inelastic mean free path within the solid, and RSF i represents the Relative Sensitive Factor. For example, if peaks of elements A and B are detected via XPS with peak areas of 1000 and 500, respectively, and RSFs of 0.8 and 1.2, respectively, then the content ratio of A is It can be calculated as (75%).

[0067] In this specification, the meaning of the intensity of an XPS peak of a specific element refers to the sum of all peaks appearing through the XPS spectrum of each element. For example, Si by XPS 2p When observing the spectrum, Si 0 , Si-C, Si x (0 <x≤4) 등, 다양한 산화 상태를 나타내는 피크가 나타나지만, Si의 함량비를 계산할 때, 상기 피크의 강도를 모두 더한 값을 Si 원소의 피크의 강도로 계산한다.

[0068] In one embodiment of the present specification, j may be any one of silicon, carbon, oxygen, and nitrogen.

[0069] When a silicon-carbon composite according to one embodiment of the present invention was etched with an argon (Ar) ion beam at an energy of 1,000 eV for 5,000 seconds and then analyzed by XPS, N 1s Si relative to the ratio of N element measured by the spectrum 2p The ratio of the proportion of Si elements measured by the spectrum can be about 35 to 200.

[0070] In a silicon carbon composite according to one embodiment of the present invention, the lower limit of the ratio of the ratio of the Si element to the ratio of the N element may be about 35 or more, 37 or more, or 40 or more, and the upper limit may be about 200 or less, 150 or less, or 100 or less.

[0071] A secondary battery using a negative electrode active material in which the ratio of Si elements to N elements on the surface of a silicon-carbon composite satisfies the above range exhibits excellent capacity, efficiency, and lifespan. For example, when the ratio of Si elements to N elements on the surface of the silicon-carbon composite is within the above range, capacity and efficiency increase, which can lead to higher energy density of the cell and excellent cycle performance and high-rate characteristics.

[0072] For example, amorphous silicon causes unstable processability in an aqueous slurry, but if N is doped in the above ratio range to form a Si-N phase, process stability can be secured, and the Si-N phase acts as a buffer for volume expansion during charging and discharging, thereby achieving the effect of improving long-term life performance.

[0073] When a silicon-carbon composite according to one embodiment of the present invention was etched with an argon (Ar) ion beam at an energy of 1,000 eV for 5,000 seconds and then analyzed by XPS, N 1s The proportion of the N element measured by the spectrum may be about 0.35 atm% or more based on 100 atm% of the total Si, C, O, and N elements contained in the silicon carbon composite. For example, the lower limit of the proportion of the N element may be about 0.35 atm% or more, 0.37 atm% or more, or 0.40 atm% or more, and the upper limit may be about 2 atm% or less, 1.5 atm% or less, or 1 atm% or less.

[0074] When the ratio of N is within the above range, cycle performance and high-rate characteristics are excellent, and the energy density of the cell can be increased due to high capacity and efficiency.

[0075] When a silicon-carbon composite according to one embodiment of the present invention is etched with an argon (Ar) ion beam at an energy of 1,000 eV for 5,000 seconds and then analyzed by XPS, Si 2p The proportion of Si element measured by the spectrum may be about 20 atm% or more and 50 atm% or less. For example, the lower limit of the proportion of the Si element may be about 20 atm% or more, 25 atm% or more, or 28 atm% or more, and the upper limit may be about 50 atm% or less, 40 atm% or less, or about 35 atm% or less.

[0076] If the ratio of Si is maintained within the above range, capacity and efficiency increase, which can lead to higher energy density of the cell, and excellent cycle performance and high rate.

[0077] In one embodiment of the present specification, in order to satisfy the peak ratio in a silicon carbon composite material of a method for depositing silicon on porous carbon, the method may be performed by at least one of the following: a method of controlling the mixing ratio of a nitrogen source gas in the step of heating a carbon-based powder, or a method of controlling the mixing ratio using a silane and a nitrogen source mixed gas in the step of depositing silicon.

[0078] In one embodiment of the present specification, the nitrogen source gas may be nitrogen gas or ammonia gas, and may be, for example, nitrogen gas.

[0079] According to one embodiment, a carbon-based powder may be placed in a tubular furnace and nitrogen gas may be flowed to create an inert atmosphere, then the temperature may be gradually increased to heat to a temperature of about 300°C to 500°C, and then the temperature may be gradually increased again to heat to a temperature of about 800°C to 1000°C.

[0080] Subsequently, the powder obtained by heating is mixed with an acidic solvent and centrifuged to obtain a precipitate, and the obtained powder is neutralized in a basic solvent and dried to obtain a porous carbon structure. At this time, the temperature at which the carbon-based particles are placed in a basic solvent and heated may be approximately 700°C to 900°C.

[0081] A silicon carbon composite can be obtained by placing the above porous carbon structure into a horizontal furnace and flowing SiH4 / N2 gas at approximately 500°C to 800°C. For example, the temperature may be 550°C to 700°C or 550°C to 650°C.

[0082] At this time, the mixing ratio of SiH4 and N2 (SiH4 / N2) may be 97:3 to 88:12, for example, 95:5 to 90:10. The process may further include a step of forming a carbon layer by placing the silicon carbon composite obtained through the above process into a furnace, heat-treating it, and then flowing a hydrocarbon gas at about 600°C to 800°C. According to one embodiment, the temperature may be about 550°C to 770°C, or 600°C to 700°C.

[0083] Meanwhile, silicon-based powder can be placed in a horizontal tube and argon gas can be flowed to create an inert atmosphere, after which the temperature can be gradually increased to induce disproportionation. At this time, the heat treatment temperature may be approximately 750°C to 1200°C, and for example, 800°C to 1100°C.

[0084] After this, the above heat-treated SiO x After removing it from the tube, a step of removing the SiO2 phase by acid treatment and stirring can be performed.

[0085] After drying the porous silicon obtained above, a carbon layer can be formed by chemical vapor deposition (CVD) with a hydrocarbon gas at about 550 °C to 850 °C. The hydrocarbon gas may be at least one hydrocarbon gas selected from methane, ethane, propane, and acetylene.

[0086] In the above deposition / coating temperature range, the carbon surface layer becomes uniform and silicon carbide is formed, improving the processability of the water-based slurry.

[0087] In one embodiment of the present specification, in the case of a method for compounding carbon with porous silicon, the compounding can be performed by mixing a hydrocarbon and a nitrogen mixed gas in a certain ratio during the CVD process to satisfy the peak ratio.

[0088] For example, the mixing ratio of the hydrocarbon and nitrogen may be 97:3 to 88:12, for example, 95:5 to 90:10.

[0089] According to one embodiment, the silicon-carbon composite has a surface area of ​​about 0.5 m² by the BET method. 2 / g to 10 m 2 It can be / g, and the pore volume is 0.005 cm³ 3 / g to 0.03 cm 3 It may be / g, and the pore size determined by the BET method may be 1 nm to 20 nm. The silicon-carbon composite has a pore volume of approximately 0.005 cm² as measured by the mercury infiltration method. 3 / g to 0.03 cm 3 / g can be.

[0090] According to one embodiment, the silicon carbon composite is D 90 The particle size may be 5 μm to 15 μm, and D 50 The particle size may be 1 μm to 10 μm, and D min This 1 μm to 3 μm, D maxThe value may be 17 μm to 23 μm. In this specification, the average particle size (D 50 ) can be defined as the particle size corresponding to 50% of the cumulative volume in the particle size distribution curve. The above average particle size (D 50 ) can be measured, for example, using the laser diffraction method. The laser diffraction method generally enables the measurement of particle sizes ranging from the submicron range to several millimeters, and can obtain results with high reproducibility and high resolution.

[0091] One embodiment provides a negative electrode active material comprising a silicon carbon composite according to the embodiments described above.

[0092] One embodiment provides a cathode composition comprising a cathode active material according to the above embodiment; a binder and a conductive material.

[0093] According to one embodiment, the silicon carbon composite may be included in an amount of about 0.1 to 15 parts by weight based on 100 parts by weight of the negative electrode active material, for example, about 0.1 to 10 parts by weight, or 1 to 8 parts by weight.

[0094] According to one embodiment, the cathode active material may further include a carbon-based active material. The carbon-based active material may be included in an amount of about 70 parts by weight or more and 99.9 parts by weight or less, for example, 85 parts by weight to 99 parts by weight, based on 100 parts by weight of the total cathode active material included in the cathode composition. The carbon-based active material may include at least one of natural graphite and artificial graphite. When the carbon-based active material includes both natural graphite and artificial graphite, the weight ratio of the artificial graphite and the natural graphite may be about 1:9 to 9:1, for example, about 3:7 to 7:3. For example, based on 100 parts by weight of the carbon-based active material, the natural graphite may be about 10 parts by weight to 70 parts by weight; and the artificial graphite may be about 30 parts by weight to 90 parts by weight.

[0095] The above natural graphite refers to graphite that occurs naturally, examples of which include scaled graphite, scalable graphite, or soil graphite. This natural graphite has the advantages of being abundant, having a low price, high theoretical capacity and compaction density, and the ability to achieve high output.

[0096] According to one example, spherical natural graphite may be used as the natural graphite, and the degree of sphericity may be about 0.9 or higher. According to one example, the natural graphite is spherical natural graphite and may have a tap density of about 0.9 g / cc or higher.

[0097] In this specification, sphericity may be a 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 obtained from a Scanning Electron Microscope (SEM) image or measured using a particle shape analyzer, such as the Malvern Sysmex FPIA3000. Additionally, crystal size can be confirmed through XRD analysis.

[0098] According to one embodiment of the present invention, the cathode composition further comprises a binder and a conductive material, and the binder may be a water-based binder.

[0099] The binder may comprise at least one selected from polyvinylidenefluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidenefluoride, polyacrylonitrile, polymethylmethacrylate, 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 materials in which the hydrogens thereof are substituted with Li, Na, or Ca, etc., and may also comprise various copolymers thereof.

[0100] The above conductive material is not particularly limited as long as it is conductive without causing chemical changes in the battery, and for example, graphite such as natural graphite or artificial graphite; carbon black such as acetylene black, Ketjen black, channel black, Farnes black, lamp black, thermal black; conductive fibers such as carbon fibers or metal fibers; conductive tubes such as carbon nanotubes; metal powders such as fluorocarbon, aluminum, or nickel powder; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; conductive materials such as polyphenylene derivatives may be used.

[0101] According to one embodiment, the aqueous binder is included in an amount of about 1% to 5% by weight, for example, about 3% to 4% by weight, based on the solid content of the cathode composition, and the conductive material may be included in an amount of about 0.1% to 2% by weight, for example, about 1% by weight, based on the solid content of the cathode composition.

[0102] One embodiment of the present invention provides a cathode (120) comprising a cathode composition according to the embodiments described above.

[0103] For example, the cathode (120) may include a cathode current collector (122) and a cathode active material layer (124) disposed on at least one surface of the cathode current collector (122). The cathode active material layer (124) includes a cathode composition according to the embodiment described above.

[0104] The above-described cathode active material layer (124) can be formed by applying a cathode slurry containing the aforementioned cathode composition to at least one surface of a cathode current collector (122), drying, and rolling.

[0105] The above-mentioned negative current collector (122) may be conductive without causing chemical changes in the battery, and is not particularly limited. For example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, etc. may be used as the current collector (122). According to one embodiment, a transition metal that adsorbs carbon well, such as copper or nickel, may be used as the current collector (122). The thickness of the above-mentioned current collector (122) may be about 6 μm to 20 μm, but the thickness of the above-mentioned current collector (122) is not limited thereto.

[0106] The above cathode slurry may include a solvent for forming the cathode slurry. For example, the solvent for forming the cathode slurry may include at least one selected from distilled water, ethanol, methanol, and isopropyl alcohol, for example, distilled water, in terms of facilitating the dispersion of the components.

[0107] One embodiment of the present invention provides a lithium secondary battery (100) comprising a negative electrode (120), a positive electrode (110), and a separator (130) according to the above embodiment.

[0108] The above positive electrode (110) may include a positive electrode current collector and a positive electrode active material layer formed on the positive electrode current collector and including the positive electrode active material.

[0109] In the above positive electrode (110), the positive electrode current collector is not particularly limited as long as it is conductive without causing chemical changes in the battery, and for example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface treated with carbon, nickel, titanium, silver, etc. may be used. In addition, the above positive electrode current collector may typically have a thickness of about 3 μm to 500 μm, and fine irregularities may be formed on the surface of the positive electrode current collector to increase the adhesion of the positive electrode active material. For example, it may be used in various forms such as a film, sheet, foil, net, porous body, foam, nonwoven body, etc.

[0110] The above-mentioned positive electrode active material may be a commonly used positive electrode active material. For example, the above-mentioned 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-c1Lithium manganese oxides such as O4 (0≤c1≤0.33), LiMnO3, LiMn2O3, LiMnO2, etc.; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, V2O5, Cu2V2O7, etc.; chemical formula LiNi 1-c2 M c2 Ni-site type lithium nickel oxide represented by O2 (wherein M is at least one selected from Co, Mn, Al, Cu, Fe, Mg, B, and Ga, satisfying 0.01≤c2≤0.3); chemical formula LiMn 2-c3 M c3 Examples include lithium manganese composite oxides represented by O2 (where M is at least one selected from Co, Ni, Fe, Cr, Zn and Ta, satisfying 0.01≤c3≤0.1) or Li2Mn3MO8 (where M is at least one selected from Fe, Co, Ni, Cu and Zn); and LiMn2O4 in which a portion of the Li in the chemical formula is substituted with alkaline earth metal ions, but are not limited to these. The anode (110) may also be Li-metal.

[0111] The above-described positive active material layer may include a positive conductive material and a positive binder together with the positive active material described above.

[0112] The above-mentioned positive electrode conductive material is used to impart conductivity to the electrode, and in the battery being constructed, any material that possesses electronic conductivity without causing chemical changes can be used without any special limitations. Examples include graphite such as natural graphite or artificial graphite; carbon-based materials such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, and carbon fibers; metal powders or metal fibers such as copper, nickel, aluminum, and silver; conductive whiskey such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives, and one of these alone or a mixture of two or more may be used.

[0113] In addition, the anode binder serves to improve adhesion between anode active material particles and adhesion between the anode active material and the anode current collector. Examples include polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, 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.

[0114] The separator (130) separates the negative electrode (120) and the positive electrode (110) and provides a pathway for the movement of lithium ions. Any separator typically used in secondary batteries can be used without special limitations, and it may have low resistance to the movement of electrolyte ions and excellent electrolyte moisture retention capacity. For example, a porous polymer film, such as a porous polymer film made of a polyolefin-based polymer like ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer, and ethylene / methacrylate copolymer, or a laminated structure of two or more layers thereof may be used. In addition, a conventional porous nonwoven fabric, such as a nonwoven fabric made of high-melting-point glass fiber or polyethylene terephthalate fiber, may be used. Furthermore, a coated separator containing ceramic components or polymer materials may be used to ensure heat resistance or mechanical strength, and may optionally be used in a single-layer or multi-layer structure.

[0115] The above lithium secondary battery (100) may additionally include an electrolyte (140). Examples of the electrolytes that can be used in the manufacture of lithium secondary batteries include organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel-type polymer electrolytes, solid inorganic electrolytes, molten inorganic electrolytes, etc., but are not limited to these.

[0116] According to one embodiment, the electrolyte (140) may include a non-aqueous organic solvent and a metal salt.

[0117] As the above-mentioned 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, gamma-butyl lactone, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyl tetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolone, formamide, dimethylformamide, dioxolone, acetonitrile, nitromethane, methyl formate, methyl acetate, phosphate triester, trimethoxymethane, dioxolone derivative, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivative, tetrahydrofuran derivative, ether, methyl propionate, ethyl propionate, etc. may be used.

[0118] Among the above carbonate-based organic solvents, cyclic carbonates such as ethylene carbonate and propylene carbonate can be preferably used as high-viscosity organic solvents with high dielectric constants that effectively dissociate lithium salts. By mixing these cyclic carbonates with low-viscosity, low-dielectric constant linear carbonates such as dimethyl carbonate and diethyl carbonate in appropriate proportions, an electrolyte (140) with high electrical conductivity can be produced.

[0119] The metal salt mentioned above may be a lithium salt, and the lithium salt is a substance that dissolves well 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 - One or more types selected from can be used.

[0120] In addition to the electrolyte components mentioned above, the electrolyte (140) may further include one or more additives, such as a haloalkylene carbonate compound like difluoroethylene carbonate, pyridine, triethylphosphite, triethanolamine, cyclic ether, ethylene diamine, n-glyme, triamide hexaphosphate, nitrobenzene derivative, sulfur, quinone imine dye, N-substituted oxazolidinone, N,N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2-methoxyethanol, or aluminum trichloride, for the purpose of improving the lifespan characteristics of the battery, suppressing the decrease in battery capacity, and improving the discharge capacity of the battery.

[0121] According to another embodiment of the present invention, a battery module comprising the lithium secondary battery (100) as a unit cell and a battery pack comprising the same are provided. Since the battery module and the battery pack include the secondary battery having high capacity, high rate capability and cycle capability, they can be used as a power source for a medium-to-large device selected from the group consisting of electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles and power storage systems.

[0122] Hereinafter, the present specification will be described in detail with reference to examples. However, the embodiments according to the present specification may be modified in various different forms, and the scope of the present application is not to be interpreted as being limited to the embodiments described below. The embodiments of the present application are provided to more completely explain the present specification to those with average knowledge in the art.

[0123]

[0124] <Example 1>

[0125] (1) Preparation of silicon carbon composite 1

[0126] Cellulose powder was placed in a turbular furnace, heated to 400°C at a rate of 4°C / min, and heated under a nitrogen atmosphere for 2 hours. Subsequently, the furnace was heated to 900°C at a rate of 4°C / min and heated under a nitrogen atmosphere for 2 hours. The powder was mixed with sulfuric acid and nitric acid in a 3:1 volume ratio, stirred at 60°C for 2 hours, and then centrifuged to obtain a precipitate. The obtained powder was washed 5 times in a solvent mixed with ethanol and distilled water in a 1:3 volume ratio, and then dried at 120°C for 12 hours. The carbon-based particles were placed in a KOH solvent and heated at 800°C under a nitrogen atmosphere for 2 hours to obtain a porous carbon structure. The porous carbon structure was washed 3 times with distilled water and dried at 120°C for at least 12 hours. The porous carbon structure was classified to obtain an average particle size (D 50 The thickness was adjusted to 9㎛. The above porous carbon structure was placed in a horizontal furnace, and a silicon carbon composite was prepared by flowing SiH4 / N2=95 / 5 gas at a flow rate of 50 ml / min at 650°C for 1 hour. The silicon carbon composite was then placed in an electric furnace, and acetylene gas was flowed at 600°C for 3 hours to produce a silicon carbon composite negative electrode active material containing a carbon layer on the outermost surface.

[0127] (2) Preparation of the cathode

[0128] A cathode active material comprising the above-manufactured silicon carbon composite, natural graphite, and artificial graphite in a weight ratio of 10:15:75; a conductive material comprising carbon black and SWCNT; and a binder comprising carboxymethylcellulose (CMC) and styrene butadiene rubber (SBR) were mixed with an appropriate amount of distilled water in a weight ratio of 95.4:1:3.6 such that the total solid content was approximately 46% by weight, thereby preparing a cathode slurry.

[0129] The above cathode slurry was applied to a Cu metal thin film with a thickness of approximately 15 μm and dried at a circulating air temperature of 60°C. Subsequently, after rolling, it was dried in a vacuum oven at 130°C for about a day, and then 1.4875 cm 2 The cathode was manufactured by stamping it into a circular shape.

[0130] (3) Manufacturing of secondary batteries

[0131] 1.7671cm 2 A Li metal thin film formed by stamping was used as the anode. A porous polyethylene separator was placed between the anode and the cathode, and an electrolyte containing 1M concentration of dissolved LiPF6 containing an additive of a mixed solution of EMC (methyl ethyl carbonate) and EC (ethylene carbonate) in a mixing ratio of 7:3 was injected to prepare a Li coin half-cell.

[0132]

[0133] <Example 2>

[0134] (1) Manufacturing of silicon carbon composite 2

[0135] A silicon carbon composite was prepared in the same manner as in Example 1, except that SiH4 / N2=90 / 10 gas was flowed at a flow rate of 50 ml / min at 650°C for 1 hour.

[0136] (2) Manufacturing of negative electrode and secondary battery

[0137] It was prepared in the same manner as Example 1, except that silicon carbon composite 2 was used.

[0138]

[0139] <Example 3>

[0140] (1) Manufacturing of silicon carbon composite 3

[0141] A silicon carbon composite was prepared in the same manner as in Example 1, except that SiH4 / N2=95 / 5 gas was flowed at a flow rate of 50 ml / min at 550°C for 1 hour.

[0142] (2) Manufacturing of negative electrode and secondary battery

[0143] It was prepared in the same manner as Example 1, except that silicon carbon composite 3 was used.

[0144]

[0145] <Example 4>

[0146] (1) Manufacturing of silicon carbon composite 4

[0147] D 50 This 6㎛ SiOx (0 <x≤1)를 수평식 튜브 (horizontal tube)에 넣은 후, 1500sccm의 속도로 아르곤(Ar) 가스를 1시간 동안 흘러줘서 비활성 분위기를 만들어주었다. 그리고 150sccm의 속도로 아르콘 가스를 흘러주었고, 10℃ / min의 속도로 온도를 1000℃까지 증가시킨 후 6시간 동안 유지하여 불균등 반응(disproportionation)을 유도하였다. 상기 열처리된 SiOx(0<x≤1)를 튜브에서 꺼낸 후, 20 중량비의 HF 수용액에 침지시킨 후, 상온에서 1시간동안 교반하여 SiO2상을 제거하였다. 상기 얻어진 다공성 실리콘을 600℃진공 오븐에서 12시간 동안 건조하였다. 이후, 상기 건조된 다공성 실리콘을 CVD 장비를 이용하여 600℃에서 1:9 부피비로 혼합된 질소 / 아세틸렌 혼합 가스를 100sccm 속도로 3시간 흘러주어 최종 실리콘 카본 복합체를 제조하였다.

[0148] (2) Manufacturing of negative electrode and secondary battery

[0149] It was prepared in the same manner as Example 1, except that silicon carbon composite 4 was used.

[0150]

[0151] <Comparative Example 1>

[0152] (1) Manufacturing of silicon carbon composite 5

[0153] It was prepared in the same manner as in Example 1, except that SiH4 / N2=95 / 5 gas was flowed at a flow rate of 50 ml / min at 500°C for 1 hour.

[0154] (2) Manufacturing of negative electrode and secondary battery

[0155] It was prepared in the same manner as Example 1, except that silicon carbon composite 5 was used.

[0156]

[0157] <Comparative Example 2>

[0158] (1) Manufacturing of silicon carbon composite 6

[0159] It was prepared in the same manner as in Example 1, except that SiH4 / N2=99 / 1 gas was flowed at a flow rate of 50 ml / min at 650°C for 1 hour.

[0160] (2) Manufacturing of negative electrode and secondary battery

[0161] It was prepared in the same manner as Example 1, except that silicon carbon composite 6 was used.

[0162]

[0163] <Comparative Example 3>

[0164] (1) Manufacturing of silicon carbon composite 7

[0165] It was prepared in the same manner as in Example 4, except that a nitrogen / acetylene mixed gas mixed in a 1:99 volume ratio was reacted at 750℃ at a rate of 100 sccm for 3 hours.

[0166] (2) Manufacturing of negative electrode and secondary battery

[0167] It was prepared in the same manner as Example 1, except that silicon carbon composite 7 was used.

[0168]

[0169] <Comparative Example 4>

[0170] (1) Manufacturing of silicon carbon composite 8

[0171] It was prepared in the same manner as in Example 1, except that SiH4 / N2=95 / 5 gas was flowed at a flow rate of 50 ml / min at 750°C for 10 hours.

[0172] (2) Manufacturing of negative electrode and secondary battery

[0173] It was prepared in the same manner as Example 1, except that silicon carbon composite 8 was used.

[0174]

[0175] <Comparative Example 5>

[0176] (1) Manufacturing of silicon carbon composite 9

[0177] A silicon carbon composite prepared by mixing polished Si particles and ground carbon at 40°C was ground to an average particle size of 7 μm. The ground silicon carbon composite was reacted with a nitrogen / acetylene mixed gas at a volume ratio of 5:95 at 800°C at a rate of 100 sccm for 3 hours to prepare silicon carbon composite 9.

[0178] (2) Manufacturing of negative electrode and secondary battery

[0179] It was prepared in the same manner as Example 1, except that silicon carbon composite 9 was used.

[0180]

[0181] The XPS analysis results of the cathode active materials prepared in the above examples and comparative examples are shown in Figures 3 and 4 and Table 1 below.

[0182] Figure 3 shows the spectrum that appears when the secondary battery of the example is analyzed by XPS, and Figure 4 shows the spectrum that appears when the secondary battery of the comparative example is analyzed by XPS.

[0183] The Relative Sensitive Factor used in the experiment is as follows.

[0184] RSF Si =0.9

[0185] RSF N =1.676

[0186] RSF C =1.0

[0187] RSF O =2.881

[0188] Si Content Ratio (atm%) N Content Ratio (atm%) Ratio of Si Element / Ratio of N Element Example 1 32.00.477 Example 2 26.30.740.7 Example 3 27.60.392 Example 4 32.70.562.2 Comparative Example 1 30.40.1304 Comparative Example 2 32.00.1320 Comparative Example 3 26.30.1263 Comparative Example 4 87.90.4220 Comparative Example 5 12.30.431

[0189] The discharge capacity, initial efficiency, capacity retention rate, and slurry viscosity change rate of the above examples and comparative examples were measured and listed in Table 2 below.

[0190] <Discharge Capacity, Initial Efficiency, Capacity Retention Rate>

[0191] The first and second cycles were charged and discharged at 0.1C, and from the third cycle to the 299th cycle, they were charged and discharged at 0.5C. The 300th cycle was terminated in a charged state (where lithium is contained in the negative electrode).

[0192] Charging conditions: CC (constant current) / CV (constant voltage) (5mV / 0.005C current cut-off)

[0193] Discharge condition: CC (constant current) condition 1.5V

[0194] 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.

[0195] Initial efficiency (%) = (Discharge capacity per cycle / Charge capacity per cycle) × 100

[0196] The capacity retention rates were each derived by the following calculations.

[0197] Capacity Retention Rate (%) = (299 Discharge Cycles Capacity / 1 Discharge Cycle Capacity) × 100

[0198] Battery Discharge Capacity (mAh / g) Initial Efficiency (%) Capacity Retention Rate (%) Example 1 50 39 2.88 9.9 Example 2 50 19 2.59 0.1 Example 3 50 39 2.48 9.6 Example 4 50 9 2.38 9.0 Comparative Example 1 48 58 9.18 4.1 Comparative Example 2 48 48 8.48 3.5 Comparative Example 3 49 28 8.48 3.0 Comparative Example 4 49 89 0.57 8.9 Comparative Example 5 47 88 7.67 5.1

[0199] As shown in Table 2 above, N in Table 1 1s Si relative to the ratio of N element measured by the spectrum 2p Examples 1 to 4, in which the ratio of Si elements measured by the spectrum is 35 to 200, showed high discharge capacity and efficiency, and it can be confirmed that they are also excellent in terms of capacity retention rate.

[0200] In contrast, Comparative Examples 1 to 5 did not satisfy the above ratios and showed inferior effects in terms of capacity, efficiency, and capacity retention rate. For example, Comparative Examples 1, 2, and 4 manufactured silicon carbon composites by depositing silane gas onto porous carbon, but the mixing ratio of silane gas and nitrogen or the deposition temperature was not appropriate, so Si was excessively deposited compared to N inside the silicon carbon composite, resulting in inferior cycle performance and high-rate characteristics.

[0201] In the case of Comparative Example 3, a silicon-carbon composite was prepared by depositing acetylene gas onto porous silicon, but it can be seen that compared to Example 4 prepared by a similar method, Si was excessively deposited compared to N inside, resulting in low cycle characteristics.

[0202] In the case of Comparative Example 5, it can be seen that N is excessively contained compared to Si inside the silicon carbon composite, so the ratio of Si is low, resulting in low energy density and inferior efficiency.

[0203] Although the foregoing has been described with reference to the embodiments of the present disclosure, a person skilled in the art or having ordinary knowledge in the art will understand that various modifications and changes can be made to the various embodiments of the present disclosure without departing from the technical scope of the various embodiments of the present disclosure as set forth in the claims below. Accordingly, the technical scope of the various embodiments of the present disclosure should not be limited to the contents described in the detailed description of the specification, but should be determined by the claims.

Claims

1. When XPS analyzed after etching with an argon (Ar) ion beam at an energy of 1,000 eV for 5,000 seconds, N 1s Si relative to the ratio of N element measured by the spectrum 2p A silicon carbon composite having a ratio of Si elements measured by spectrum of 35 to 200.

2. In Claim 1, the above N 1s A silicon carbon composite in which the proportion of the N element measured by the spectrum is 0.35 atm% or more based on a total of 100 atm% of Si, C, O, and N elements contained in the silicon carbon composite.

3. The silicon carbon composite of claim 1, wherein the silicon carbon composite comprises porous carbon particles and silicon particles provided on at least a portion of the interior and surface of the porous carbon particles; or a silicon carbon composite comprising porous silicon particles and carbon particles provided on at least a portion of the interior and surface of the porous silicon particles.

4. A silicon-carbon composite according to any one of claims 1 to 3; and a negative electrode active material comprising a carbon-based active material.

5. The negative electrode active material according to claim 4, wherein the silicon carbon composite is included in an amount of 0.1 to 15 parts by weight based on 100 parts by weight of the negative electrode active material.

6. A cathode active material according to claim 4; a cathode composition comprising a binder and a conductive material.

7. The cathode composition of claim 6, wherein the silicon carbon composite is included in an amount of 0.1 to 15 parts by weight based on 100 parts by weight of the cathode active material.

8. A cathode composition according to claim 6, wherein the carbon-based active material comprises artificial graphite and natural graphite.

9. A cathode comprising the cathode composition according to claim 6.

10. A lithium secondary battery comprising a negative electrode, a positive electrode, and a separator according to claim 9.

11. A battery module comprising a lithium secondary battery according to claim 10.

12. A battery pack comprising a lithium secondary battery according to claim 10.

13. A battery pack comprising the battery module of claim 11.

14. Anode; cathode; and A lithium secondary battery comprising a separator located between the anode and the cathode, The above cathode comprises a current collector and a cathode active material layer formed on at least one surface of the current collector, and The above-mentioned cathode active material layer comprises a cathode composition including a cathode active material, a binder, and a conductive material, and When the above-mentioned cathode active material was etched with an argon (Ar) ion beam at an energy of 1,000 eV for 5,000 seconds and then analyzed by XPS, N 1s Si relative to the ratio of N element measured by the spectrum 2p A lithium secondary battery comprising a silicon-carbon composite having a ratio of Si elements measured by spectrum of 35 to 200.

15. In Claim 14, In the above silicon carbon composite, the N 1s A lithium secondary battery in which the proportion of N element measured by spectrum is 0.35 atm% or more based on 100 atm% of the total Si, C, O, and N elements contained in the silicon carbon composite.

16. In Claim 14, The above silicon carbon composite comprises a porous carbon particle and a particle having silicon provided on at least a portion of the interior and surface of the porous carbon particle; or a lithium secondary battery having a porous silicon particle and carbon provided on at least a portion of the interior and surface of the porous silicon particle.

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