A negative electrode active material, a negative electrode containing the same, a secondary battery containing the same, and a method for manufacturing the negative electrode active material.

Abstract

The present invention relates to a negative electrode active material, a negative electrode containing the same, a secondary battery containing the same, and a method for manufacturing the negative electrode active material.

Description

[Technical Field]

[0001] This application claims the benefit as of the filing date of Korean Patent Application No. 10-2022-0150562, filed with the Korean Intellectual Property Office on November 11, 2022, and Korean Patent Application No. 10-2023-0154765, filed with the Korean Intellectual Property Office on November 9, 2023, and all of its contents are incorporated herein by reference.

[0002] The present invention relates to a negative electrode active material, a negative electrode containing the same, a secondary battery containing the same, and a method for producing a negative electrode active material. [Background technology]

[0003] In recent years, with the rapid proliferation of electronic devices that use batteries, such as mobile phones, laptops, and electric vehicles, the demand for rechargeable batteries that are small, lightweight, and relatively high-capacity has been rapidly increasing. In particular, lithium-ion batteries are attracting attention as a power source for portable devices due to their light weight and high energy density. 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 the current collector of the positive and negative electrodes, respectively. 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] Among negative electrode active materials, silicon-based active materials are attracting attention because they have a higher capacity and superior fast charging characteristics compared to carbon-based active materials. However, silicon-based active materials have the disadvantage of low initial efficiency due to a large degree of volume expansion / contraction during charging and discharging, resulting in a large irreversible capacity.

[0006] On the one hand, among silicon-based active materials, silicon-based oxides, specifically SiO x In the case of silicon-based oxides represented by (0 < x < 2), there is an advantage in that the degree of volume expansion / contraction due to charge and discharge is lower compared to other silicon-based active materials such as silicon (Si). However, there is still a drawback that the initial efficiency decreases due to the presence of irreversible capacity in silicon-based oxides as well.

[0007] In relation to this, research has been continuously conducted to reduce irreversible capacity and improve initial efficiency by doping or inserting metals such as Li, Al, and Mg into silicon-based oxides. However, in the case of a negative electrode slurry containing a metal-doped silicon-based oxide as a negative electrode active material, there is a problem that the metal oxide formed by doping reacts with moisture to increase the pH of the negative electrode slurry and change the viscosity. For this reason, the state of the manufactured negative electrode becomes poor, and there is a problem that the charge and discharge efficiency of the negative electrode decreases.

[0008] In addition, as the cycle progresses, there is a problem that swelling of the negative electrode occurs and many side reactions of the electrolyte occur.

[0009] Therefore, in a situation where it is necessary to develop a negative electrode active material that can suppress the surface reaction of the negative electrode active material containing a silicon-based oxide, improve the phase stability of the slurry, and improve the charge and discharge efficiency of the negative electrode manufactured therefrom.

Prior Art Documents

Patent Documents

[0010]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0011] The present invention relates to a negative electrode active material, a negative electrode containing the same, a secondary battery containing the same, and a method for manufacturing a negative electrode active material.

Means for Solving the Problem

[0012] One embodiment of the present invention is a silicon-based particle containing SiO x (0 < x < 2) and a Mg compound; and a negative electrode active material including a carbon layer provided on at least a part of the silicon-based particle, wherein the negative electrode active material contains N element and H element, and the total content of the N element and the H element is 250 ppm or more and less than 3000 ppm based on 100 parts by weight of the negative electrode active material, and the weight ratio of the H element to the N element is 1 or less. A negative electrode active material is provided.

[0013] One embodiment of the present invention provides a negative electrode.

[0014] One embodiment of the present invention provides a secondary battery including the negative electrode.

[0015] One embodiment of the present invention includes the steps of vaporizing Si powder, SiO2 powder, and Mg respectively and mixing them, and then cooling the mixed gas to form silicon-based particles; and mixing the silicon-based particles with a carbon-based material to provide a carbon layer on at least a part of the surface of the silicon-based particles. A method for manufacturing a negative electrode active material according to the present invention is provided.

Effect of the Invention

[0016] The negative electrode active material according to one embodiment of the present invention contains a Mg compound, and is characterized in that the total of N and H in the negative electrode active material is 250 ppm or more and less than 3000 ppm, and the weight ratio of H to N is 1 or less. The negative electrode active material satisfying this has high hardness and elasticity, has characteristics advantageous for swelling of the negative electrode, has high conductivity of the carbon layer, and has an effect of improving life characteristics.

[0017] Therefore, a negative electrode including the negative electrode active material according to one embodiment of the present invention and a secondary battery including the negative electrode have an effect of improving the discharge capacity, initial efficiency, resistance performance, and / or life characteristics of the battery.

Mode for Carrying Out the Invention

[0018] The following provides a more detailed description of this specification.

[0019] In this specification, when a part "includes" a component, this means that, unless otherwise stated, it may include other components rather than excluding them.

[0020] In this specification, when one member is said to be "on top of" another member, this includes not only cases where one member is in contact with another member, but also cases where another member exists between the two members.

[0021] 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.

[0022] The terms used herein are for illustrative purposes only and are not intended to limit the invention. The singular expressions used herein include plural expressions unless the context clearly indicates otherwise.

[0023] In this specification, the crystallinity of the structure contained in the negative electrode active material can be confirmed by X-ray diffraction analysis. X-ray diffraction analysis can be performed using an XRD (X-ray diffraction) analyzer (product name: D4-endavor, manufacturer: bruker), and other instruments used in this industry may be used as appropriate.

[0024] In this specification, the presence and content of elements in the negative electrode active material can be confirmed by ICP analysis, which can be performed using an inductively coupled plasma atomic emission spectrometer (ICPAES, Perkin-Elmer 7300).

[0025] In this specification, the average particle diameter (D 50 ) can be defined as the particle diameter corresponding to 50% of the volume accumulation amount in the particle size distribution curve (graph curve of the particle size distribution diagram) of the particles. The average particle diameter (D 50 ) can be measured, for example, using the laser diffraction method. The laser diffraction method can generally measure particle diameters ranging from the submicron region to about several millimeters, and can obtain highly reproducible and highly resolvable results.

[0026] Hereinafter, preferred embodiments of the present invention will be described in detail. However, the embodiments of the present invention may be modified into various forms, and the scope of the present invention is not limited to the embodiments described below.

[0027] <Negative electrode active material> One embodiment of the present invention is a silicon-based particle containing SiO x (0 < x < 2) and a Mg compound; and a negative electrode active material including a carbon layer provided on at least a part of the silicon-based particle, wherein the negative electrode active material contains N element and H element, and the total content of the N element and H element is 250 ppm or more and less than 3000 ppm based on 100 parts by weight of the negative electrode active material, and the weight ratio of the H element to the N element is 1 or less.

[0028] The negative electrode active material according to one embodiment of the present invention contains silicon-based particles. The silicon-based particles contain SiO x (0 < x < 2) and a Mg compound.

[0029] The SiO x (0 < x < 2) may correspond to a matrix in the silicon-based particles. The SiO x (0 < x < 2) may be in a form containing Si and / or SiO2, and the Si may form a phase. For example, the SiO x(0 < x < 2) may be a composite containing amorphous SiO2 and Si crystals. That is, the x corresponds to the number ratio of O to Si contained in the SiO x (0 < x < 2). When the silicon-based particles contain the SiO x (0 < x < 2), the discharge capacity of the secondary battery can be improved.

[0030] The Mg compound may correspond to a matrix within the silicon-based particles. The Mg compound may exist in at least one form of magnesium atoms, magnesium silicate, magnesium silicide, and magnesium oxide within the silicon-based particles. When the silicon-based particles contain a Mg compound, there is an effect that the initial efficiency is improved.

[0031] The Mg compound may be distributed on the surface and / or inside of the silicon-based particles in a doped form. The Mg compound is distributed on the surface and / or inside of the silicon-based particles, can control the expansion / contraction of the volume of the silicon-based particles to an appropriate level, and can play a role in preventing damage to the active material. Also, the Mg compound may be contained in that it reduces the ratio of the irreversible phase (for example, SiO2) of the silicon-based oxide particles and increases the efficiency of the active material.

[0032] The Mg compound may include at least any one selected from the group consisting of Mg silicate, Mg silicide, and Mg oxide. The Mg silicate may include at least any one of Mg2SiO4 and MgSiO3. The Mg silicide may include Mg2Si. The Mg oxide may include MgO.

[0033] The Mg compound may exist in the form of magnesium silicate. The Mg silicate can be classified into crystalline magnesium silicate and amorphous magnesium silicate.

[0034] The Mg compound may exist within the silicon-based particles in the form of at least one magnesium silicate, selected from Mg2SiO4 and MgSiO3.

[0035] The Mg element may be present in an amount of 0.1 to 40 parts by weight based on 100 parts by weight of the total negative electrode active material, more specifically in an amount of 0.1 to 20 parts by weight, or 0.1 to 10 parts by weight, or more specifically in an amount of 0.5 to 8 parts by weight. If the Mg content exceeds the above range, there is a problem that the initial efficiency increases as the Mg content increases, but the discharge capacity decreases. Therefore, when the above range is met, a suitable discharge capacity and initial efficiency can be achieved.

[0036] The Mg content can be confirmed by ICP analysis. Specifically, a certain amount (approximately 0.01 g) of the negative electrode active material is separated, transferred to a platinum crucible, and completely decomposed on a hot plate with the addition of nitric acid, hydrofluoric acid, and sulfuric acid. Then, using an inductively coupled plasma atomic emission spectrometer (ICPAES, Perkin-Elmer 7300), the intensity of a standard solution prepared using a standard solution (5 mg / kg) is measured at the wavelength specific to the element to be analyzed to create a reference calibration curve. Subsequently, the pre-treated sample solution and a blank sample are introduced into the instrument, their respective intensities are measured to calculate the actual intensities, and the concentrations of each component are calculated against the calibration curve created above. The total is then converted so that it equals the theoretical value, and the elemental content of the manufactured negative electrode active material can be analyzed.

[0037] In one embodiment of the present invention, the silicon-based particles may contain additional metal atoms. The metal atoms may exist within the silicon-based particles in the form of at least one of metal atoms, metal silicates, metal silicides, and metal oxides. The metal atoms may include at least one selected from the group consisting of Mg, Li, Al, and Ca. This can improve the initial efficiency of the negative electrode active material.

[0038] In one embodiment of the present invention, the silicon-based particles have a carbon layer provided on at least a portion of their surface. In this case, the carbon layer may be in a form that partially covers at least a portion of the surface, i.e., the surface of the particles, or it may cover the entire surface of the particles. The carbon layer imparts conductivity to the negative electrode active material, thereby improving the initial efficiency, life characteristics, and capacity characteristics of the secondary battery.

[0039] In one embodiment of the present invention, the carbon layer contains amorphous carbon. The carbon layer may further contain crystalline carbon.

[0040] The crystalline carbon can further improve the conductivity of the negative electrode active material. The crystalline carbon may include at least one selected from the group consisting of fullerene, carbon nanotubes, and graphene.

[0041] The amorphous carbon can appropriately maintain the strength of the carbon layer and suppress the expansion of the silicon-based particles. The amorphous carbon may be a carbon-based material formed by using at least one carbide or hydrocarbon selected from the group consisting of tar, pitch, and other organic materials as a source in chemical vapor deposition.

[0042] The aforementioned carbonized organic substances may be carbonized organic substances selected from carbonized sucrose, glucose, galactose, fructose, lactose, mannose, ribose, aldohexose, or ketohexose, and combinations thereof.

[0043] The hydrocarbon may be a substituted or unsubstituted aliphatic or alicyclic hydrocarbon, or a substituted or unsubstituted aromatic hydrocarbon. The aliphatic or alicyclic hydrocarbon of the substituted or unsubstituted aliphatic or alicyclic hydrocarbon may be methane, ethane, ethylene, acetylene, propane, butane, butene, pentane, isobutane, or hexane. Examples of the aromatic hydrocarbon of the substituted or unsubstituted aromatic hydrocarbon include benzene, toluene, xylene, styrene, ethylbenzene, diphenylmethane, naphthalene, phenol, cresol, nitrobenzene, chlorobenzene, indene, coumarone, pyridine, anthracene, or phenanthrene.

[0044] In one embodiment of the present invention, the carbon layer may be an amorphous carbon layer.

[0045] In one embodiment of the present invention, the carbon layer may be included in amounts of 0.1 to 50 parts by weight, 0.1 to 30 parts by weight, or 0.1 to 20 parts by weight, based on 100 parts by weight of the total negative electrode active material. More specifically, it may be included in amounts of 0.5 to 15 parts by weight, 1 to 10 parts by weight, or 1 to 5 parts by weight. When these ranges are met, a decrease in the capacity and efficiency of the negative electrode active material can be prevented.

[0046] In one embodiment of the present invention, the thickness of the carbon layer may be 1 nm to 500 nm, and more specifically, 5 nm to 300 nm. When this range is met, the conductivity of the negative electrode active material is improved, volume changes of the negative electrode active material are easily suppressed, side reactions between the electrolyte and the negative electrode active material are suppressed, and the initial efficiency and / or lifespan of the battery are improved.

[0047] Specifically, the carbon layer may be formed by chemical vapor deposition (CVD) using at least one hydrocarbon gas selected from the group consisting of methane, ethane, and acetylene.

[0048] In this invention, the crystallinity of the carbon layer can be confirmed by calculating the D / G band ratio using Raman spectroscopy. Specifically, measurements can be taken using a Renishaw 2000 Raman microscope system and 532 nm laser excitation, with a low laser power density and a 30-second exposure time, and a 100x optical lens to avoid the thermal effect of the laser. To reduce positional deviations, a total of 25 points are measured in a 5 μm × 5 μm area, and after fitting using a Lorentzian function, the average values ​​of the D and G bands can be calculated.

[0049] In one embodiment of the present invention, the negative electrode active material may contain N and H elements.

[0050] In one embodiment of the present invention, the total content of N and H elements may be 250 ppm or more and less than 3000 ppm. Specifically, it may be 280 ppm or more and 2000 ppm or less, 280 ppm or more and 1800 ppm or less, or 300 ppm or more and 1800 ppm or less. The lower limit of the content of N and H elements may be 250 ppm, 280 ppm, 290 ppm, 300 ppm, 350 ppm, 400 ppm, 450 ppm, 500 ppm, 550 ppm, 600 ppm, or 700 ppm, and the upper limit of the content of N and H elements may be 2900 ppm, 2500 ppm, 2000 ppm, 1800 ppm, 1600 ppm, 1500 ppm, 1300 ppm, or 1000 ppm.

[0051] When the content of N and H elements satisfies the aforementioned range, a Mg-Si-ON film is effectively formed on the surface of the silicon-based particles, allowing for control of material swelling, increasing the conductivity of the carbon layer, and improving lifetime characteristics. Conversely, when the content of N and H is below the aforementioned range, a sufficient Mg-Si-ON film is not formed on the surface of the silicon-based particles, making it difficult to control swelling. When the content of N and H exceeds the aforementioned range, the hardness and elasticity of the Mg-Si-ON film decrease, making it difficult to control swelling. Specifically, when present in an Mg-Si-ON structure rather than a structure like Si-ON glass, Mg forms bonds with O, providing a relatively robust structure. The present invention is advantageous for forming an Mg-Si-ON structure by satisfying the aforementioned specific range and proportions of N and H content, thereby improving hardness and elasticity, and thereby controlling swelling. If the N and H content is excessively high or does not meet the aforementioned ratios, the probability of Si-OH or other structures forming is relatively higher than the probability of Mg-Si-ON formation.

[0052] The aforementioned content and proportions of N and H elements can be determined according to the process conditions or materials used in the manufacturing process of the negative electrode active material. For example, the aforementioned range can be satisfied by mixing a material containing appropriate amounts of N and H, such as an appropriate amount of ammonia, along with a material that provides a carbon source during the formation of the carbon layer.

[0053] In one embodiment of the present invention, the negative electrode active material may include a Mg-Si-ON film provided on the surface of the silicon-based particles. The Mg-Si-ON film may be in a form that includes silicon oxynitride having Si-N bonds.

[0054] The aforementioned N may exist on the surface of the silicon-based particles containing the Mg compound in the form of silicon oxynitride, or it may exist in a form contained in the carbon layer. Specifically, the N may have a Si-N bond and exist on the surface of the silicon-based particles in the form of silicon oxynitride, or the N may be contained in the carbon layer in a form having a CN bond.

[0055] In other words, at least a portion of the N in the negative electrode active material according to the present invention may exist having Si-N bonds. In another embodiment, at least a portion of the N in the negative electrode active material according to the present invention may be contained in a carbon layer.

[0056] The H may exist on the surface of the silicon-based particles containing the Mg compound in a form having Si-OH bonds, or it may exist in a form contained in the carbon layer. Specifically, the H may be contained in the carbon layer in a form having CH bonds.

[0057] In one embodiment of the present invention, the content of N may be 125 ppm or more and less than 3000 ppm. Specifically, it may be 150 ppm or more and 2500 ppm or less, 175 ppm or more and 2000 ppm or less, 200 ppm or more and 1500 ppm or less, or 210 ppm or more and 1200 ppm or less. The lower limit of the content of N may be 125 ppm, 150 ppm, 175 ppm, 200 ppm, 210 ppm, 220 ppm, 250 ppm, 350 ppm, 400 ppm, or 430 ppm, and the upper limit of the content of N may be 2900 ppm, 2500 ppm, 2000 ppm, 1500 ppm, 1200 ppm, 1000 ppm, 800 ppm, 600 ppm, or 500 ppm.

[0058] When the N content satisfies the aforementioned range, the Mg-Si-ON film is effectively formed on the surface of the silicon-based particles, controlling material swelling and improving lifetime characteristics, and increasing the conductivity of the carbon layer, thus improving lifetime characteristics. Conversely, when the N content is below the aforementioned range, the Mg-Si-ON film is not effectively formed on the surface of the silicon-based particles, making it difficult to control swelling. When the N content exceeds the aforementioned range, the hardness and elasticity of the Mg-Si-ON film decrease, making it difficult to control swelling.

[0059] In one embodiment of the present invention, the content of H may be 1 ppm or more and less than 1500 ppm. Specifically, it may be 10 ppm or more and 1200 ppm or less, 50 ppm or more and 1000 ppm or less, 70 ppm or more and 800 ppm or less, or 70 ppm or more and 600 ppm or less. The lower limit of the content of H may be 1 ppm, 10 ppm, 50 ppm, 70 ppm, 80 ppm, 100 ppm, 200 ppm, or 300 ppm, and the upper limit of the content of H may be 1400 ppm, 1200 ppm, 1000 ppm, 800 ppm, 600 ppm, 500 ppm, or 400 ppm.

[0060] When the H content meets the aforementioned range, there are fewer functional groups in the carbon layer, resulting in fewer side reactions with the electrolyte and thus an improvement in battery life. Conversely, when the H content is below the aforementioned range, the hydrophobicity of the active material becomes excessively high, leading to problems with insufficient dispersion in the aqueous slurry. When the H content exceeds the aforementioned range, there is an excess of functional groups in the carbon layer, leading to increased side reactions with the electrolyte and a decrease in battery performance.

[0061] In one embodiment of the present invention, the weight ratio of H to N may be 1 or less. Specifically, it may be greater than 0 and 1 or less, or 0.1 or more and 1 or less.

[0062] The weight ratio of H to N may be 0.95 or less, 0.9 or less, 0.85 or less, or 0.8 or less, and may be 0 or more, greater than 0, 0.01 or more, 0.1 or more, greater than 0.1, 0.2 or more, or 0.3 or more. When the weight ratio of H to N satisfies the above range, the negative electrode active material is sufficiently dispersed in the aqueous slurry, resulting in excellent conductivity of the negative electrode active material and excellent Li ion withdrawal. On the other hand, if the weight ratio of H to N is less than the above range, many defects occur in the carbon layer, and side reactions of the electrolyte increase, resulting in poor cycle characteristics. If it exceeds the above range, the hydrophobicity of the carbon layer increases, and there is a problem that dispersion in the aqueous slurry does not occur sufficiently.

[0063] In this specification, the content (concentration) of the N and H elements can be measured by placing 0.1 g of the negative electrode active material sample to be measured in a crucible and placing it in an ONH analyzer (Bruker, G8 Galileo).

[0064] The average particle size (D) of the negative electrode active material 50 The particle size may be 0.1 μm to 30 μm, more specifically 1 μm to 20 μm, and more specifically 1 μm to 10 μm. When the above range is met, the structural stability of the active material during charging and discharging can be ensured, the problem of volume expansion / contraction levels increasing due to excessively large particle size can be prevented, and the problem of initial efficiency decreasing due to excessively small particle size can be prevented.

[0065] The BET specific surface area of ​​the negative electrode active material is 1 m². 2 / g~100m 2 It may also be / g, specifically 1m 2 / g~70m 2 It can also be / g, or more specifically 1m 2 / g~50m 2 It may also be / g, for example, 2m 2 / g~30m 2 It may also be / g. When the above range is met, side reactions with the electrolyte during battery charging and discharging can be reduced, thereby improving the battery's lifespan characteristics.

[0066] <Method for manufacturing negative electrode active material> One embodiment of the present invention provides a method for producing a negative electrode active material, which includes the steps of: vaporizing and mixing Si powder, SiO2 powder, and Mg, respectively, and then cooling the mixed gas to form silicon-based particles; and mixing the silicon-based particles with a carbon-based material to provide a carbon layer on at least a portion of the surface of the silicon-based particles.

[0067] The Si powder and SiO2 powder can be manufactured by heating them under vacuum to vaporize them, and then depositing the vaporized mixed gas. In this process, the Si powder and SiO2 powder may be heated and vaporized individually, or they may be heated and vaporized in a mixed state.

[0068] The Si powder and SiO2 powder may be included in a weight ratio of 2:8 to 8:2, specifically in a weight ratio of 4:6 to 6:4 or 5:5.

[0069] Specifically, the Si powder and SiO2 powder may be heat-treated under vacuum at 1300°C to 1800°C, 1400°C to 1800°C, or 1400°C to 1600°C.

[0070] The mixed gas vaporized by the heat treatment can be cooled under vacuum and deposited onto the solid phase. Furthermore, the deposited solid phase can be heat-treated in an inert atmosphere to produce preliminary silicon-based particles. The heat treatment may be performed at 500°C to 1000°C or 700°C to 900°C.

[0071] A carbon layer can be provided on the surface of the silicon-based particles.

[0072] The carbon layer may be formed by using a carbon-based material, for example, by chemical vapor deposition (CVD) using hydrocarbon gas, or by a method of carbonizing a carbon source material.

[0073] Specifically, the formed silicon-based particles may be introduced into a reactor and then formed by chemical vapor deposition (CVD) of a hydrocarbon gas at 600°C to 1200°C. The hydrocarbon gas may be at least one hydrocarbon gas selected from the group consisting of methane, ethane, propane, and acetylene, and may be heat-treated at 900°C to 1000°C.

[0074] In this case, the negative electrode active material may be made to contain N and H within the ranges described above using the method described below.

[0075] (1) A method in which, after the step of forming the silicon-based particles, the silicon-based particles are heat-treated in a nitrogen atmosphere.

[0076] In one embodiment of the present invention, after vaporizing and mixing Si powder, SiO2 powder, and Mg, and then cooling the mixed gas to form silicon-based particles, the silicon-based particles may be heat-treated in a nitrogen (N2) atmosphere. Specifically, silicon-based particles containing an Mg compound may be heat-treated in a nitrogen atmosphere to introduce silicon oxynitride onto the surface of the silicon-based particles.

[0077] In this case, the heat treatment temperature may be 850°C to 1200°C, and more specifically, 900°C to 1100°C.

[0078] Subsequently, a carbon layer may be formed on the surface of the silicon-based particles using the chemical vapor deposition (CVD) method described above under an Ar atmosphere.

[0079] (2) A method in which the step of mixing the silicon-based particles and a carbon-based material to form a carbon layer on at least a portion of the surface of the silicon-based particles is carried out under an N2 atmosphere.

[0080] In one embodiment of the present invention, the step of mixing the silicon-based particles with a carbon-based material to form a carbon layer on at least a portion of the surface of the silicon-based particles may be carried out under an N2 atmosphere.

[0081] In this case, a carbon layer may be formed on the surface of the silicon-based particles using chemical vapor deposition (CVD) in the aforementioned step. In this case, the carbon-based material may be a hydrocarbon gas.

[0082] In another embodiment, the carbon layer may be formed in the above step by coating the surface of silicon-based particles with a carbon source. In this case, the carbon-based material may be pitch.

[0083] In one embodiment of the present invention, prior to the step of mixing the silicon-based particles with a carbon-based material to form a carbon layer on at least a portion of the surface of the silicon-based particles, the silicon-based particles may be further heat-treated in an N2 atmosphere.

[0084] In this case, the heat treatment temperature may be 850°C to 1200°C, and more specifically, 900°C to 1100°C.

[0085] (3) A method in which, in the step of mixing the silicon-based particles and a carbon-based material to form a carbon layer on at least a part of the surface of the silicon-based particles, the carbon-based material is further enriched with NH3 gas.

[0086] In one embodiment of the present invention, in the step of providing a carbon layer on at least a portion of the surface of the silicon-based particles, NH3 may be further included in addition to the carbon-based material.

[0087] In this case, the weight ratio of the carbon-based material to NH3 may be 0.8:1 to 30:1. Specifically, it may be 0.8:1 to 20:1, 0.8:1 to 10:1, 0.8:1 to 5:1, 0.8:1 to 2:1, 0.8:1 to 1.5:1, or 0.8:1 to 1.2:1. When the above range is satisfied, N and H are introduced into the negative electrode active material within a suitable range, which can impart suitable hardness and elasticity to the negative electrode active material and have the effect of improving conductivity.

[0088] The above step may be carried out using chemical vapor deposition (CVD).

[0089] The anode active material according to the present invention can be manufactured by appropriately utilizing the methods (1) to (3) described above, and is not limited thereto; the anode active material according to the present invention can also be manufactured by appropriately employing a combination of the methods (1) to (3).

[0090] When the negative electrode active material is formed by the method described above, N and H are introduced into the negative electrode active material within suitable ranges, thereby improving the performance of the battery using it.

[0091] <Negative electrode> The negative electrode according to one embodiment of the present invention may include the negative electrode active material described above.

[0092] Specifically, the negative electrode may include a negative electrode current collector and a negative electrode active material layer disposed on the negative electrode current collector. The negative electrode active material layer may contain the negative electrode active material. Furthermore, the negative electrode active material layer may further include a binder, a thickener, and / or a conductive material.

[0093] The negative electrode active material layer may be formed by applying a negative electrode slurry containing a negative electrode active material, a binder, a thickener, and / or a conductive material to at least one side of a current collector, drying, and rolling.

[0094] The negative electrode slurry may further contain additional negative electrode active material.

[0095] As the additional negative electrode active material, a compound capable of reversible intercalation and deintercalation of lithium may be used. Specific examples include carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber, and amorphous carbon; metallic compounds capable of alloying with lithium, such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloys, Sn alloys, or Al alloys; and SiO2. βExamples include lithium-doped and dedoped metal oxides such as (0<β<2), SnO2, vanadium oxide, lithium titanium oxide, and lithium vanadium oxide; or composites containing the metallic compound and carbonaceous material, such as Si-C composites or Sn-C composites. One or more of these mixtures may be used. A metallic lithium thin film may also be used as the negative electrode active material. As for the carbon material, either low-crystallinity carbon or high-crystallinity carbon may be used. Examples of low-crystalline carbon include soft carbon and hard carbon, while examples of high-crystalline carbon include amorphous, plate-like, flaky, spherical, or fibrous natural or artificial graphite, Kish graphite, pyrolytic carbon, mesophase pitch-based carbon fiber, meso-carbon microbeads, mesophase pitches, and high-temperature calcined carbon such as petroleum or coal tar pitch-derived cokes.

[0096] The additional negative electrode active material may be a carbon-based negative electrode active material.

[0097] In one embodiment of the present invention, the weight ratio of the negative electrode active material contained in the negative electrode slurry to the additional negative electrode active material may be 10:90 to 90:10, and more specifically, it may be 10:90 to 50:50.

[0098] 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.

[0099] A negative electrode slurry containing a negative electrode active material according to one embodiment of the present invention may have a pH of 7 to 11 at 25°C. A pH within this range of the negative electrode slurry has the effect of stabilizing the rheological properties of the slurry. Conversely, if the pH of the negative electrode slurry is less than 7 or greater than 11, decomposition of carboxymethylcellulose (CMC), used as a thickening agent, occurs, leading to a decrease in slurry viscosity and a reduction in the dispersion of the active material contained in the slurry.

[0100] 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.

[0101] 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.

[0102] 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.

[0103] The aforementioned thickening agent may be carboxymethylcellulose (CMC), but is not limited thereto, and any other thickening agent used in the present art may be used as appropriate.

[0104] In one embodiment of the present invention, the weight ratio of the negative electrode active material contained in the negative electrode slurry to the additional negative electrode active material may be 1:99 to 30:70, specifically 5:95 to 30:70, or 10:90 to 20:80.

[0105] In one embodiment of the present invention, the total negative electrode active material contained in the negative electrode slurry may be in an amount of 60 to 99 parts by weight, specifically 70 to 98 parts by weight, based on 100 parts by weight of the total solid content of the negative electrode slurry.

[0106] In one embodiment of the present invention, the binder may be included in an amount of 0.5 to 30 parts by weight, specifically 1 to 20 parts by weight, based on 100 parts by weight of the total solid content of the negative electrode slurry.

[0107] In one embodiment of the present invention, the conductive material may be included in an amount of 0.5 to 25 parts by weight, specifically 1 to 20 parts by weight, based on 100 parts by weight of the total solid content of the negative electrode slurry.

[0108] In one embodiment of the present invention, the thickening agent may be included in an amount of 0.5 to 25 parts by weight, more specifically 0.5 to 20 parts by weight, or more specifically 1 to 20 parts by weight, based on 100 parts by weight of the total solid content of the negative electrode slurry.

[0109] A negative electrode slurry according to one embodiment of the present invention may further 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 components.

[0110] In one embodiment of the present invention, the solid content weight of the negative electrode slurry may be 20 to 75 parts by weight, specifically 30 to 70 parts by weight, based on 100 parts by weight of the total negative electrode slurry.

[0111] <Secondary battery> A secondary battery according to one embodiment of the present invention may include a negative electrode according to the embodiment described above. Specifically, the secondary battery may include a negative electrode, a positive electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte, wherein the negative electrode is the same as the negative electrode described above. Since the negative electrode has been described above, a detailed explanation will be omitted.

[0112] 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.

[0113] 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, it may be used in various forms such as film, sheet, foil, mesh, porous material, foam, or nonwoven fabric.

[0114] 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 M c2 Ni-site type lithium nickel oxide represented as O2 (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 ≤ 0.5); chemical formula LiMn 2-c3 M c3 Lithium manganese composite oxides represented as O2 (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); or LiMn2O4 in which part of the Li in the chemical formula is substituted with an alkaline earth metal ion, etc., are examples, but are not limited thereto. The positive electrode may be Li metal.

[0115] 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.

[0116] 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.

[0117] 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.

[0118] 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 those made from polyolefin polymers like ethylene homopolymers, propylene homopolymers, ethylene / butene copolymers, ethylene / hexene copolymers, and ethylene / methacrylate copolymers, or laminated structures of two or more layers thereof, may be used. Alternatively, ordinary porous nonwoven fabrics, such as those 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 these may be selectively used as single-layer or multi-layer structures.

[0119] 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.

[0120] Specifically, the electrolyte may contain a non-aqueous organic solvent and a metal salt.

[0121] 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.

[0122] 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, and therefore they can be used even more preferably.

[0123] 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:

[0124] 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, hexaphosphate 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.

[0125] 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]

[0126] The following are preferred embodiments to aid in understanding the present invention. However, these embodiments are merely illustrative examples, and it will be apparent to those skilled in the art that various changes and modifications are possible within the scope of this description and the technical concept, and such variations and modifications will naturally fall within the scope of the appended claims.

[0127] <Examples and Comparative Examples> [Example 1] 92g of a powder containing Si and SiO2 in a 1:1 molar ratio was mixed with 8g of Mg and heated under vacuum in a reaction furnace at a sublimation temperature of 1,400°C. The sublimated mixture of Mg, Si, and SiO2 was then reacted in a vacuum cooling zone with a cooling temperature of 800°C, causing it to condense into a solid phase and form silicon-based particles. Subsequently, heat treatment was performed in an inert atmosphere at 800°C. Afterward, 15 SUS ball media were added to the silicon-based particles, and the mixture was ground for 3 hours using a ball mill to a size of 6 μm (D 50 A product of the following size was manufactured. Subsequently, while maintaining an inert atmosphere by flowing Ar gas, the silicon-based particles were positioned in the hot zone of the CVD apparatus, and using Ar as the carrier gas, methane and ammonia were added in a weight ratio of 9:1 and blown into the 950°C hot zone for 10 -1 The reaction was carried out in Torr for 20 minutes to form a carbon layer on the surface of the silicon-based particles.

[0128] The substance produced as described above was used as the negative electrode active material in Example 1. 50 The thickness is 6 μm, and the specific surface area is 6 m². 2 It was / g.

[0129] Measurements using an ONH component analyzer revealed that the nitrogen content in the negative electrode active material was 450 ppm, and the hydrogen content was 360 ppm.

[0130] [Example 2] In Example 1, the negative electrode active material was produced using the same method, except that the weight ratio of methane to ammonia was set to 1:1.

[0131] Measurements using an ONH component analyzer revealed that the nitrogen content in the negative electrode active material was 1100 ppm and the hydrogen content was 500 ppm.

[0132] [Example 3] In Example 1, the negative electrode active material was produced using the same method, except that the weight ratio of methane to ammonia was set to 95:5.

[0133] Measurements using an ONH component analyzer revealed that the nitrogen content in the negative electrode active material was 220 ppm and the hydrogen content was 80 ppm.

[0134] [Comparative Example 1] In Example 1, the negative electrode active material was produced using the same method, except that the weight ratio of methane to ammonia was set to 1:2.

[0135] Measurements using an ONH component analyzer revealed that the nitrogen content in the negative electrode active material was 1600 ppm and the hydrogen content was 1500 ppm.

[0136] [Comparative Example 2] In Example 1, the active material was produced using the same method, except that the CVD temperature was set to 900°C.

[0137] Measurements using an ONH component analyzer revealed that the nitrogen content in the negative electrode active material was 400 ppm, and the hydrogen content was 430 ppm.

[0138] [Comparative Example 3] In Example 1, the active material was produced using the same method, except that the weight ratio of methane to ammonia was set to 1:3.

[0139] Measurements using an ONH component analyzer revealed that the nitrogen content in the negative electrode active material was 1500 ppm and the hydrogen content was 1600 ppm.

[0140] [Comparative Example 4] In Example 1, the active material was produced using the same method, except that ammonia was not added.

[0141] Measurements using an ONH component analyzer revealed that the nitrogen content in the negative electrode active material was 10 ppm and the hydrogen content was 1 ppm.

[0142] The composition of the negative electrode active material produced in the above examples and comparative examples is shown in Table 1 below.

[0143] [Table 1]

[0144] In this specification, the content (concentration) of elements N and H was measured by placing 0.1 g of the negative electrode active material sample to be measured in a crucible and immersing it in an ONH analyzer (Bruker, G8 Galileo). The content of element Mg was confirmed by ICP analysis using an inductively coupled plasma atomic emission spectrometer (ICP-OES, AVIO 500, Perkin-Elmer 7300).

[0145] The carbon content of the aforementioned carbon layer was confirmed under oxygen conditions by elemental analysis by combustion (Bruker G4 ICARUS).

[0146] The D of the negative electrode active material 50 The PSD (Photon Scale Degradation) was analyzed using a microtrac device.

[0147] The specific surface area of ​​the negative electrode active material was measured using a BET measuring device (BEL-SORP-MAX, Nippon Bell) by degassing the gas at 200°C for 8 hours and then performing N2 adsorption / desorption at 77K.

[0148] <Experimental Example: Evaluation of Discharge Capacity, Initial Efficiency, and Lifetime (Capacity Retention Rate) Characteristics> A negative electrode and a battery were manufactured using the negative electrode active materials of the examples and comparative examples, respectively.

[0149] A mixture was prepared by mixing the aforementioned negative electrode active material, carbon black as a conductive material, and PAA (polyacrylic acid) as a binder in a weight ratio of 80:10:10. Then, 7.8g of distilled water was added to 5g of the mixture and stirred to produce a negative electrode slurry. The negative electrode slurry was applied to a copper (Cu) metal thin film, which was a negative electrode current collector with a thickness of 20μm, and dried. During this process, the temperature of the circulating air was 60°C. Next, the film was rolled (rolled in a roll press) and dried in a vacuum oven at 130°C for 12 hours to produce a negative electrode.

[0150] The manufactured negative electrode was 1.7671 cm 2 A circularly cut lithium (Li) metal thin film was used as the positive electrode. A porous polyethylene separator was interposed between the positive electrode and the negative electrode. A lithium coin half-cell was manufactured by dissolving vinylene carbonate in a mixed solution of ethyl methyl carbonate (EMC) and ethylene carbonate (EC) in a volume ratio of 7:3, at a concentration of 0.5 parts by weight, and then injecting an electrolyte containing 1M LiPF6.

[0151] The manufactured batteries were subjected to charging and discharging tests to evaluate their discharge capacity, initial efficiency, and capacity retention rate, which are shown in Table 2 below.

[0152] 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

[0153] 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

[0154] The capacity retention rates were derived using the following calculations. Capacity retention rate (%) = (49 discharge capacity / 1 discharge capacity) × 100

[0155] [Table 2]

[0156] In Table 2, Examples 1 to 3 using the negative electrode active material according to the present invention contain N and H elements in the negative electrode active material, with a total content of N and H elements of 250 ppm or more and less than 3000 ppm based on 100 parts by weight of the negative electrode active material, and a weight ratio of H elements to N elements of 1 or less. It was confirmed that the discharge capacity, initial efficiency, and capacity retention rate of the battery were improved. This is thought to be because the Mg-Si-ON film appropriately formed on the surface of the silicon-based particles of the present invention effectively controls material swelling, thereby increasing the conductivity of the carbon layer. In contrast, Comparative Examples 1 to 4 either have a total content of less than 250 ppm or more than 3000 ppm of N and H elements, or the weight ratio of H elements to N in the active material is greater than 1. In these comparative examples, the negative electrode active material either does not adequately form an Mg-Si-ON film on the surface of the silicon-based particles, or the hardness and elasticity of the formed Mg-Si-ON film are reduced, making it difficult to control swelling, and thus it can be confirmed that the discharge capacity, initial efficiency, and life characteristics of the battery are inferior.

Claims

1. SiO ｘ (0 < x < 2) and silicon-based particles containing Mg compounds; and A carbon layer provided on at least a portion of the silicon-based particles. A negative electrode active material containing, The negative electrode active material comprises N and H elements. The total content of the aforementioned N and H elements is 250 ppm or more and 2000 ppm or less based on 100 parts by weight of the negative electrode active material. A negative electrode active material in which the weight ratio of H element to N element is 0.85 or less.

2. The negative electrode active material according to claim 1, wherein the N element is contained in an amount of 125 ppm or more and 1500 ppm or less based on 100 parts by weight of the negative electrode active material.

3. The negative electrode active material according to claim 1, wherein the H element is contained in an amount of 1 ppm or more and less than 1500 ppm based on 100 parts by weight of the negative electrode active material.

4. The negative electrode active material according to claim 1, wherein the weight ratio of element H to element N is 0.1 or more and 0.85 or less.

5. The negative electrode active material according to claim 1, wherein at least a portion of the N exists having a Si-N bond.

6. The negative electrode active material according to claim 1, wherein at least a portion of the N is present in the carbon layer.

7. The negative electrode active material according to claim 1, wherein the Mg compound comprises Mg silicate.

8. The negative electrode active material according to claim 1, wherein the element Mg is contained in an amount of 0.1 parts by weight or more and 40 parts by weight or less based on 100 parts by weight of the total negative electrode active material.

9. The anode active material according to claim 1, wherein the carbon layer is contained in an amount of 0.1 parts by weight or more and 50 parts by weight or less, based on a total of 100 parts by weight of the anode active material.

10. Si powder, SiO ２ The steps include: vaporizing the powder and Mg separately and mixing them, then cooling the mixed gas to form silicon-based particles; and A step of mixing the silicon-based particles with a carbon-based material to form a carbon layer on at least a portion of the surface of the silicon-based particles. A method for producing a negative electrode active material according to any one of claims 1 to 9, including

11. A method for producing a negative electrode active material according to claim 10, further comprising the step of heat-treating the silicon-based particles in a nitrogen atmosphere after the step of forming the silicon-based particles.

12. In the step of mixing the silicon-based particles with a carbon-based material to form a carbon layer on at least a portion of the surface of the silicon-based particles, in addition to the carbon-based material, NH ３ A method for producing a negative electrode active material according to claim 10, further comprising adding gas.

13. A negative electrode comprising the negative electrode active material according to any one of claims 1 to 9.

14. A secondary battery comprising the negative electrode described in claim 13.

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