Anode active material, anode including the same, secondary battery including the same, and method for manufacturing anode 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 producing the negative electrode active material.

Description

[Technical Field]

[0001] The present invention relates to an anode active material, an anode containing the same, a secondary battery containing the same, and a method for producing the anode active material.

[0002] This application claims the benefit of the filing dates of Korean Patent Application No. 10-2022-0111916 filed with the Korean Intellectual Property Office on September 5, 2022, and Korean Patent Application No. 10-2023-0115379 filed with the Korean Intellectual Property Office on August 31, 2023, and all contents disclosed in the documents of the corresponding Korean patent applications are incorporated herein by reference. [Background technology]

[0003] In recent years, the rapid spread of battery-powered electronic devices such as mobile phones, laptops, and electric vehicles has led to a rapid increase in demand for small, lightweight, and relatively high-capacity secondary batteries. Lithium secondary batteries, in particular, are attracting attention as a power source for portable devices due to their light weight and high energy density. This has led to vigorous research and development efforts aimed at improving the performance of lithium secondary batteries.

[0004] Generally, a lithium secondary battery includes a positive electrode, a negative electrode, a separator between the positive electrode and the negative electrode, an electrolyte, an organic solvent, etc. The positive electrode and the negative electrode may each have an active material layer formed on a current collector, the active material layer including a positive electrode active material and a negative electrode active material. Generally, the positive electrode uses a lithium-containing metal oxide such as LiCoO2 or LiMn2O4 as the positive electrode active material, and the negative electrode uses a lithium-free carbon-based active material or a silicon-based active material as the negative electrode active material.

[0005] Among negative electrode active materials, silicon-based active materials have attracted attention due to their high capacity and excellent high-speed charging characteristics compared to carbon-based active materials. However, silicon-based active materials have the disadvantage of low initial efficiency due to their large volume expansion / contraction during charging / discharging and their large irreversible capacity.

[0006] On the one hand, among silicon-based active materials, in the case of silicon-based oxides, specifically silicon-based oxides represented by SiO x (0 < x < 2), there is an advantage in that the degree of volume expansion / contraction due to charge / 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.

[0007] Regarding this, research has been continuously conducted to reduce the irreversible capacity and improve the 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, thereby resulting in a poor state of the manufactured negative electrode and a decrease in the charge / discharge efficiency of the negative electrode.

[0008] Therefore, there is a need to develop a negative electrode active material that can improve the phase stability of a negative electrode slurry containing silicon-based oxides and improve the charge / discharge efficiency of the negative electrode manufactured therefrom. Summary of the Invention Problems to be Solved by the Invention

[0009] 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. Means for Solving the Problems <s

[0010] One embodiment of the present invention provides a silicon-based particle containing SiO x (0 < x < 2) and a Li compound; a carbon layer provided on at least a part of the surface of the silicon-based particle; and a surface layer containing Li, Al, and P provided on at least a part of the surface of the carbon layer, wherein an oxide containing one or more selected from the group consisting of Zr, B, Al, Zn, W, and Ti is provided at the interface between the silicon-based particle and the carbon layer.

[0011] One embodiment of the present invention provides a negative electrode including the negative electrode active material.

[0012] One embodiment of the present invention provides a secondary battery including the negative electrode.

[0013] One embodiment of the present invention is SiO x (0 < x < 2); manufacturing preliminary silicon-based particles containing the same; mixing the preliminary silicon-based particles with one or more oxides selected from the group consisting of Zr, B, Al, Zn, W, and Ti, or depositing the oxides on the preliminary silicon-based particles to provide the oxides on the surface of the preliminary silicon-based particles; providing a carbon layer on at least a part of the surface of the preliminary silicon-based particles; mixing the preliminary silicon-based particles provided with the carbon layer and a Li precursor, and then performing heat treatment to manufacture silicon-based particles; mixing the silicon-based particles with at least one selected from the group consisting of an Al precursor, a P precursor, and a precursor containing Al and P, and providing a surface layer on at least a part of the surface of the carbon layer. A method for manufacturing a negative electrode active material according to one embodiment of the present invention is provided.

Effects of the Invention

[0014] The negative electrode active material according to one embodiment of the present invention includes a surface layer containing Li, Al, and P, and is characterized in that one or more oxides selected from the group consisting of Zr, B, Al, Zn, W, and Ti are provided at the interface between the silicon-based particles and the carbon layer. By including the surface layer and the oxides simultaneously in the negative electrode active material, the reactivity of silicate, which has a high reactivity with water or basicity, can be reduced, external contact can be easily blocked, and the water-based processability of the slurry can be improved.

[0015] Specifically, the surface layer can effectively remove lithium by-products contained in the silicon-based particles during the process of forming the surface layer, and the formed surface layer can effectively cover unreacted lithium by-products, preventing the lithium by-products or silicates in the silicon-based particles from reacting with water in the slurry and degrading the physical properties of the slurry. Furthermore, since the surface layer contains Li, it has the effect of reducing lithium diffusion resistance on the surface of the negative electrode active material, thereby improving discharge rate capability.

[0016] Furthermore, by including an oxide containing one or more elements selected from the group consisting of Zr, B, Al, Zn, W, and Ti at the interface between the silicon-based particles and the carbon layer, the reactivity of highly reactive silicate within the silicon-based particles can be reduced, preventing contact with the outside world, and significantly improving aqueous processability.

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

[0018] The present specification will be explained in more detail below.

[0019] In this specification, when a part is said to "comprise" a certain component, this means that it may further include other components, rather than excluding other components, unless specifically stated to the contrary.

[0020] In this specification, when a member is said to be located "on" another member, this includes not only when the member is in contact with the other member, but also when there is another member between the two members.

[0021] The terms and words used in this specification should not be construed as being limited to their conventional or dictionary meanings, but should be construed in a meaning and concept that corresponds to the technical idea of ​​the present invention, in accordance with the principle that the inventor can appropriately define the concept of the term in order to best explain the invention.

[0022] As used herein, the singular expression of a term includes the plural expression unless the context clearly dictates otherwise.

[0023] In this specification, the crystallinity of the structure contained in the negative electrode active material may be confirmed by X-ray diffraction analysis. The X-ray diffraction analysis may be performed using an X-ray diffraction (XRD) analysis device (product name: D4-Endavor, manufacturer: Bruker), and in addition to the above device, any device commonly used in the art may be appropriately adopted.

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

[0025] In this specification, the average particle size (D 50 ) can be defined as the particle size corresponding to 50% of the cumulative volume on the particle size distribution curve (graph curve of particle size distribution). 50 ) can be measured, for example, by using a laser diffraction method. The laser diffraction method generally enables measurement of particle sizes from the submicron range to several mm, and can provide results with high reproducibility and high resolution.

[0026] Preferred embodiments of the present invention will be described in detail below. However, the embodiments of the present invention can be modified in various ways, 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 silicon oxide x (0 < x < 2) and silicon-based particles containing a Li compound; a carbon layer provided on at least a part of the surface of the silicon-based particles; and a surface layer containing Li, Al, and P provided on at least a part of the surface of the carbon layer, and an oxide containing one or more selected from the group consisting of Zr, B, Al, Zn, W, and Ti is provided at the interface between the silicon-based particles and the carbon layer. A negative electrode active material is provided.

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

[0029] The SiO x (0 < x < 2) can correspond to a matrix within 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. 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 Li compound can correspond to a matrix within the silicon-based particles. The Li compound may exist in at least one form of lithium atoms, lithium silicate, lithium silicide, and lithium oxide within the silicon-based particles. When the silicon-based particles contain a Li compound, there is an effect of improving the initial efficiency.

[0031] The Li compound can be distributed on the surface and / or inside of the silicon-based particles in a form doped into the silicon-based particles. The Li compound is distributed on the surface and / or inside of the silicon-based particles, can control the volume expansion / contraction of the silicon-based particles to an appropriate level, and can play a role in preventing damage to the active material. Further, the Li compound may be included in terms of reducing the proportion of the irreversible phase (e.g., SiO2) of the silicon-based oxide particles to increase the efficiency of the active material.

[0032] In one embodiment of the present invention, the Li compound can exist in the form of lithium silicate. The lithium silicate is represented by Li a Si b O c (2 ≤ a ≤ 4, 0 < b ≤ 2, 2 ≤ c ≤ 5), and can be classified into crystalline lithium silicate and amorphous lithium silicate. The crystalline lithium silicate can exist in the form of at least one lithium silicate selected from the group consisting of Li2SiO3, Li4SiO4, and Li2Si2O5 within the silicon-based particles, and the amorphous lithium silicate may have a complex structure of the form Li a Si b O c (2 ≤ a ≤ 4, 0 < b ≤ 2, 2 ≤ c ≤ 5), and is not limited to the above form.

[0033] In one embodiment of the present invention, based on 100 parts by weight of the total negative electrode active material, the Li element may be contained in an amount of 0.1 part by weight to 40 parts by weight or 0.1 part by weight to 25 parts by weight. Specifically, it may be contained in an amount of 1 part by weight to 25 parts by weight, and more specifically, it may be contained in an amount of 2 parts by weight to 20 parts by weight. As the content of Li increases, the initial efficiency increases, but there is a problem that the discharge capacity decreases. Therefore, when the above range is satisfied, an appropriate discharge capacity and initial efficiency can be realized.

[0034] The Li element content can be confirmed by ICP analysis. Specifically, a certain amount (approximately 0.01 g) of the negative electrode active material is taken and transferred to a platinum crucible. Nitric acid, hydrofluoric acid, and sulfuric acid are added and the mixture is completely decomposed on a hot plate. Then, an inductively coupled plasma (ICPAES, Perkin-Elmer 7300) spectrometer is used to measure the intensity of a standard solution (5 mg / kg) prepared at the characteristic wavelength of the element to be analyzed, creating a reference calibration curve. The pretreated sample solution and the base sample are then introduced into the instrument, and their respective intensities are measured to calculate the actual intensities. The concentrations of each component relative to the created calibration curve are calculated, and the total is converted to a theoretical value, allowing the element content of the prepared negative electrode active material to be analyzed.

[0035] In one embodiment of the present invention, the silicon-based particles may contain additional metal atoms. The metal atoms may be present in 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 may improve the initial efficiency of the negative electrode active material.

[0036] In one embodiment of the present invention, the silicon-based particles have a carbon layer formed on at least a portion of their surfaces. The carbon layer may cover at least a portion of the surface, i.e., the particle surface, or may cover the entire particle surface. The carbon layer provides electrical conductivity to the negative electrode active material, thereby improving the initial efficiency, lifespan characteristics, and battery capacity characteristics of the secondary battery.

[0037] In one embodiment of the present invention, the carbon layer contains amorphous carbon. Furthermore, the carbon layer may further contain crystalline carbon.

[0038] 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 nanotube, and graphene.

[0039] 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 using at least one carbide selected from the group consisting of tar, pitch, and other organic substances, or a hydrocarbon as a source for chemical vapor deposition.

[0040] The carbonized organic material may be a carbonized organic material selected from the group consisting of sucrose, glucose, galactose, fructose, lactose, mannose, ribose, aldohexose, and kedohexose, and combinations thereof.

[0041] 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, hexane, or the like. The aromatic hydrocarbon of the substituted or unsubstituted aromatic hydrocarbon may be benzene, toluene, xylene, styrene, ethylbenzene, diphenylmethane, naphthalene, phenol, cresol, nitrobenzene, chlorobenzene, indene, coumarone, pyridine, anthracene, phenanthrene, or the like.

[0042] In one embodiment of the present invention, the carbon layer may be an amorphous carbon layer.

[0043] In one embodiment of the present invention, the carbon layer may be included in an amount 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 a total of 100 parts by weight of the negative electrode active material. More specifically, the carbon layer may be included in an amount of 0.5 to 15 parts by weight, 1 to 10 parts by weight, or 1 to 5 parts by weight. When the amount is within the above range, a decrease in capacity and efficiency of the negative electrode active material can be prevented.

[0044] In one embodiment of the present invention, the thickness of the carbon layer is 1 nm to 500 nm, and specifically may be 5 nm to 300 nm. When the thickness is within this range, the conductivity of the negative electrode active material is improved, volume change of the negative electrode active material is easily suppressed, and side reactions between the electrolyte and the negative electrode active material are suppressed, resulting in improved initial efficiency and / or lifespan of the battery.

[0045] Specifically, the carbon layer can be formed by chemical vapor deposition (CVD) using at least one hydrocarbon gas selected from the group consisting of methane, ethane, and acetylene.

[0046] In the present invention, the crystallinity of the carbon layer can be confirmed by calculating the D / G band ratio using Raman spectroscopy. Specifically, measurements can be performed using a Renishaw 2000 Raman microscope system and 532 nm laser excitation, with a 100x optical lens at a low laser power density and 30 seconds of exposure time to avoid laser thermal effects. To reduce positional deviations, a total of 25 points are measured over a 5 μm × 5 μm area, and the results are fitted using a Lorentzian function, followed by the average values ​​of the D and G bands.

[0047] The negative electrode active material according to one embodiment of the present invention includes a surface layer containing Li, Al, and P provided on at least a portion of the surface of the carbon layer.

[0048] Specifically, the surface layer may be in a form in which it covers at least a portion of the silicon-based particle having a carbon layer on its surface. That is, the surface layer may be in a form in which it covers only a portion of the particle surface, or in which it covers the entire particle surface. Examples of the shape of the surface layer include an island type and a thin film type, but the shape of the surface layer is not limited thereto.

[0049] The surface layer may be provided on at least a part of the carbon layer. That is, the surface layer is coated adjacent to the carbon layer, and contains SiO x (0 < x < 2) and Li compound, and can be provided in the form of particle-carbon layer-surface layer. The surface layer can substantially or completely cover the carbon layer, or can partially cover the carbon layer.

[0050] In addition, the surface layer may be further provided on a region of the surface of the silicon-based particles where the carbon layer is not provided. That is, the surface layer is coated adjacent to the surface of the silicon-based particles where the carbon layer is not coated, and may be provided in the form of silicon-based particle-surface layer.

[0051] In one embodiment of the present invention, the surface layer contains Li, Al and P.

[0052] In one embodiment of the present invention, the surface layer may contain Li, Al, P and O elements.

[0053] In one embodiment of the present invention, the Al element contained in the negative electrode active material may be contained in an amount of 0.05 parts by weight or more and 0.5 parts by weight or less based on 100 parts by weight of the total negative electrode active material. Specifically, it may be contained in an amount of 0.1 parts by weight or more and 0.4 parts by weight or less, may be contained in an amount of 0.12 parts by weight or more and 0.35 parts by weight or less, and may be contained in an amount of 0.15 parts by weight or more and 0.3 parts by weight or less. The lower limit of the content of Al is 0.05 parts by weight, 0.1 parts by weight, 0.12 parts by weight, or 0.15 parts by weight, and the upper limit is 0.5 parts by weight, 0.4 parts by weight, 0.35 parts by weight or 0.3 parts by weight.

[0054] In one embodiment of the present invention, the P element contained in the negative electrode active material may be contained in an amount of 0.05 parts by weight or more and 2 parts by weight or less based on 100 parts by weight in total of the negative electrode active material. Specifically, it may be contained in an amount of 0.1 parts by weight or more and 1.5 parts by weight or less, may be contained in an amount of 0.15 parts by weight or more and 1.2 parts by weight or less, or may be contained in an amount of 0.3 parts by weight or more and 1.2 parts by weight or less. The lower limit of the content of P is 0.05 parts by weight, 0.1 parts by weight, 0.15 parts by weight, 0.2 parts by weight, 0.25 parts by weight, 0.3 parts by weight, 0.35 parts by weight, 0.4 parts by weight, 0.45 parts by weight or 0.5 parts by weight, and the upper limit is 2 parts by weight, 1.5 parts by weight, 1.2 parts by weight or 1 part by weight.

[0055] In one embodiment of the present invention, the Li element contained in the surface layer may be contained in an amount of 0.05 parts by weight or more and 2 parts by weight or less based on 100 parts by weight in total of the negative electrode active material. Specifically, it may be contained in an amount of 0.1 parts by weight or more and 1.5 parts by weight or less, or may be contained in an amount of 0.15 parts by weight or more and 1 part by weight or less. The lower limit of the content of Li contained in the surface layer is 0.05 parts by weight, 0.1 parts by weight, 0.15 parts by weight, 0.2 parts by weight, 0.25 parts by weight, 0.3 parts by weight, 0.35 parts by weight, 0.4 parts by weight, 0.45 parts by weight or 0.5 parts by weight, and the upper limit is 2 parts by weight, 1.5 parts by weight, 1.2 parts by weight or 1 part by weight.

[0056] In one embodiment of the present invention, the surface layer contains Li y Al z P w O v (0 < y ≤ 10, 0 < z ≤ 10, 0 < w ≤ 10, 0 < v ≤ 10) phase may be included. The y, z, w, and v represent the atomic number ratios.

[0057] In one embodiment of the present invention, the surface layer may contain at least one selected from the group consisting of aluminum oxide, phosphorus oxide, lithium oxide, aluminum phosphate, lithium salt, lithium phosphate, and lithium aluminate. In one example, the Li y Al z P w O vThe phase may include, but is not limited to, a mixture or a compound formed from Li3PO4, AlPO4, Al(PO3)3, LiAlO2, or the like.

[0058] When a surface layer containing the above components is provided, it is possible to prevent the phenomenon that the Li compound contained in the silicon-based particles reacts with the moisture of the slurry to lower the viscosity of the slurry, thereby having the effect of improving the stability of the electrode state and / or the charge-discharge capacity.

[0059] In one embodiment of the present invention, the surface layer may include an amorphous phase. In one example, the surface layer may be an amorphous phase. In one example, when performing X-ray diffraction analysis of the negative electrode active material according to one embodiment of the present invention, crystalline peaks derived from the surface layer may not appear.

[0060] In one embodiment of the present invention, the surface layer may further include at least one selected from the group consisting of Li2O, LiOH, and Li2CO3. Generally, in the process of doping lithium into silicon-based particles, the remaining substances are exposed to moisture and air, and lithium by-products such as Li2O, LiOH, and Li2CO3 can be formed. Therefore, the surface layer may be in a form containing at least one selected from the group consisting of Li2O, LiOH, and Li2CO3.

[0061] In one embodiment of the present invention, y may satisfy 0 < y ≤ 3.

[0062] In one embodiment of the present invention, z may satisfy 0 < z ≤ 1.

[0063] In one embodiment of the present invention, w may satisfy 0.5 ≤ w ≤ 3.

[0064] In one embodiment of the present invention, v may satisfy 4 < v ≤ 12.

[0065] The surface layer can be formed by dry mixing 1) silicon-based particles and aluminum phosphate, 2) silicon-based particles, an aluminum precursor, and a phosphorus precursor, or 3) silicon-based particles and a Li-Al-PO-based precursor and then heat treating the mixture, or by mixing the mixture in a solvent and then reacting the mixture while evaporating the solvent.

[0066] In one embodiment of the present invention, the surface layer may be included in an amount of more than 0 to 10 parts by weight, based on a total of 100 parts by weight of the negative electrode active material. Specifically, the surface layer may be included in an amount of 0.1 to 10 parts by weight, 0.3 to 8 parts by weight, or 0.5 to 5 parts by weight. More specifically, the surface layer may be included in an amount of 1 to 3.5 parts by weight, or 1.5 to 3 parts by weight. If the surface layer content is less than the above range, it may be difficult to prevent gas generation on the slurry, and if the surface layer content is greater than the above range, it may be difficult to achieve capacity or efficiency.

[0067] The upper limit of the content of the surface layer may be 10 parts by weight, 8 parts by weight, 6 parts by weight, 5 parts by weight, 4 parts by weight, 3.5 parts by weight, or 3 parts by weight, and the lower limit may be 0.1 parts by weight, 0.3 parts by weight, 0.5 parts by weight, 0.8 parts by weight, 1 part by weight, 1.2 parts by weight, 1.4 parts by weight, or 1.5 parts by weight.

[0068] In one embodiment of the present invention, the weight ratio of the surface layer to the carbon layer may be 1:0.1 to 1:30. Specifically, it may be 1:0.5 to 1:5, 1:1 to 1:4, or 1:1 to 1:3. By satisfying these ranges, the carbon layer and the surface layer effectively cover the silicon-based particles, efficiently suppressing side reactions in the slurry and stably achieving capacity and / or efficiency. On the other hand, if the content of the surface layer is too high compared to the carbon layer, it is difficult to achieve capacity or efficiency, and if the content of the carbon layer is too high compared to the surface layer, it is difficult to prevent gas generation in the slurry.

[0069] In one embodiment of the present invention, the surface layer may be included in an amount of 90 parts by weight or less, based on 100 parts by weight of the carbon layer. Specifically, the surface layer may be included in an amount of 80 parts by weight or less, 70 parts by weight or less, 60 parts by weight or less, or 50 parts by weight or less, based on 100 parts by weight of the carbon layer. The surface layer may also be included in an amount of 0.1 parts by weight or more, 1 part by weight or more, 5 parts by weight or more, or 10 parts by weight or more, based on 100 parts by weight of the carbon layer. By satisfying these ranges, the carbon layer and the surface layer can effectively cover the silicon-based particles, thereby efficiently suppressing side reactions in the slurry and achieving stable capacity and / or efficiency.

[0070] In one embodiment of the present invention, an oxide containing at least one selected from the group consisting of Zr, B, Al, Zn, W, and Ti is provided at the interface between the silicon-based particle and the carbon layer.

[0071] By providing an oxide containing Zr, B, Al, Zn, W, or Ti at the interface between the silicon-based particles and the carbon layer, the reactivity of silicate, which is highly reactive with water or basicity, can be reduced, and contact with the outside can be easily blocked. In addition, the oxide has low reactivity with the binder component of the slurry, further improving aqueous processability.

[0072] The oxide may contain Zr, specifically in the form of ZrO2.

[0073] The oxide may contain B, specifically in the form of B2O3.

[0074] The oxide may comprise Al, specifically in the form of Al2O3.

[0075] The oxide may contain Zn, specifically in the form of ZnO.

[0076] The oxide may contain W, specifically in the form of WO3.

[0077] The oxide may contain Ti, specifically in the form of TiO2.

[0078] The oxide may include at least one selected from the group consisting of ZrO2, B2O3, Al2O3, ZnO, WO3, and TiO2.

[0079] The oxides are not limited to the above types, and any oxide known in the art can be appropriately selected and used.

[0080] The phrase "the oxide containing at least one selected from the group consisting of Zr, B, Al, Zn, W, and Ti is provided at the interface between the silicon-based particle and the carbon layer" means that the oxide is provided adjacent to the surface of the silicon-based particle, and a carbon layer is provided adjacent to the oxide on the surface of the silicon-based particle. In other words, the silicon-based particle having the oxide on its surface may be coated with a carbon layer.

[0081] Furthermore, an oxide containing at least one selected from the group consisting of Zr, B, Al, Zn, W, and Ti may be further provided adjacent to the surface of the silicon-based particle on which the carbon layer is not provided.

[0082] In one embodiment of the present invention, the oxide may be included in an amount of 0.01 to 0.5 parts by weight, based on a total of 100 parts by weight of the negative electrode active material. Specifically, the oxide may be included in an amount of 0.01 to 0.3 parts by weight, 0.02 to 0.25 parts by weight, 0.03 to 0.2 parts by weight, 0.05 to 0.2 parts by weight, 0.01 to 0.2 parts by weight, or 0.07 to 0.16 parts by weight. When the oxide content is within the above range, the reactivity of silicate, which has high reactivity with water or base, can be effectively reduced. This can prevent the negative electrode active material from reacting with water in an aqueous slurry or lithium by-products from leaching out, thereby improving aqueous processability. On the other hand, if the content of the oxide exceeds the above range, the conductivity of the surface of the silicon-based particles is reduced, resulting in poor charge / discharge capacity / efficiency. On the other hand, if the content of the oxide is less than the above range, the reactivity of silicate near the surface of the silicon-based particles is not sufficiently reduced, resulting in poor improvement in the processability of the aqueous slurry.

[0083] The lower limit of the content of the oxide may be 0.01 parts by weight, 0.02 parts by weight, 0.03 parts by weight, 0.04 parts by weight, 0.05 parts by weight, 0.06 parts by weight, or 0.07 parts by weight, and the upper limit may be 0.5 parts by weight, 0.4 parts by weight, 0.3 parts by weight, 0.25 parts by weight, 0.2 parts by weight, 0.18 parts by weight, 0.15 parts by weight, or 0.12 parts by weight.

[0084] In one embodiment of the present invention, the Zr, B, Zn, W, and Ti oxides may each be included in an amount of 0.003 to 0.2 parts by weight, based on a total of 100 parts by weight of the negative electrode active material. Specifically, the amount may be 0.003 to 0.18 parts by weight, 0.004 to 0.17 parts by weight, 0.005 to 0.16 parts by weight, 0.01 to 0.15 parts by weight, 0.03 to 0.15 parts by weight, or 0.05 to 0.12 parts by weight. When the amount satisfies the above ranges, the reactivity of silicates, which are highly reactive with water or basicity, is reduced, thereby preventing the negative electrode active material from reacting with water in an aqueous slurry or lithium by-products from leaching out, thereby improving aqueous processability. On the other hand, if the content of these elements exceeds the above range, the conductivity of the surface of the silicon-based particles decreases, resulting in poor charge / discharge capacity / efficiency, and the metal is likely to exist as a simple metal rather than a metal oxide at the interface between the silicon-based particles and the carbon layer, acting as a metal impurity and adversely affecting the charge / discharge of the battery, causing lithium dendrites to grow internally and further leading to internal short circuits.If the content of these elements is below the above range, the reactivity of the silicate near the surface of the silicon-based particles cannot be sufficiently reduced, resulting in insufficient improvement of aqueous slurry processability.

[0085] In one embodiment of the present invention, the Al contained in the oxide may be 0.003 to 0.2 parts by weight, based on a total of 100 parts by weight of the negative electrode active material. Specifically, the Al may be 0.003 to 0.18 parts by weight, 0.004 to 0.17 parts by weight, 0.005 to 0.16 parts by weight, 0.01 to 0.15 parts by weight, 0.03 to 0.15 parts by weight, or 0.05 to 0.12 parts by weight. When the Al content is within the above range, the reactivity of silicate, which is highly reactive with water or base, is reduced, thereby preventing the negative electrode active material from reacting with water in an aqueous slurry or preventing lithium by-products from leaching out, thereby improving aqueous processability.

[0086] The oxide may be present in an amount of 1 to 12 parts by weight, based on a total of 100 parts by weight of the surface layer, specifically, 2 to 12 parts by weight, 2 to 10 parts by weight, 2 to 8 parts by weight, or 3 to 7 parts by weight. When the oxide content is within the above range, the reactivity of silicate, which is highly reactive with water or basicity, is reduced, thereby preventing the negative electrode active material from reacting with water in an aqueous slurry or preventing lithium by-products from leaching out, thereby improving aqueous processability. On the other hand, when the oxide content exceeds the above range, the conductivity of the silicon-based particle surface decreases, resulting in poor charge / discharge capacity / efficiency. Furthermore, the metal is likely to exist as a simple metal rather than a metal oxide at the interface between the silicon-based particle and the carbon layer, acting as a metal impurity and adversely affecting the charge / discharge of the battery. This can also lead to the growth of lithium dendrites inside the battery, potentially causing internal short circuits. If the content of the oxide is less than the above range, the reactivity of the silicate near the surface of the silicon-based particles is not sufficiently reduced, and the processability of the aqueous slurry is not sufficiently improved.

[0087] In one embodiment of the present invention, lithium by-products may be present on the silicon-based particles. Specifically, the lithium by-products may be present on the surface of the silicon-based particles, or on the surface of the carbon layer. Alternatively, the lithium by-products may be present between the surface layer and the silicon-based particles.

[0088] Specifically, the lithium by-product may refer to a lithium compound remaining near the surface of the silicon-based particles or the carbon layer after the silicon-based particles are produced. As described above, even after the acid treatment process, lithium by-products that have not reacted with the acid may remain.

[0089] The lithium by-product may include at least one selected from the group consisting of Li2O, LiOH, and Li2CO3.

[0090] The presence or absence of the lithium by-product can be confirmed by X-ray diffraction analysis (XRD) or X-ray photoelectron spectroscopy (XPS).

[0091] The lithium by-product may be included in an amount of 5 parts by weight or less, based on 100 parts by weight of the total negative electrode active material. Specifically, it may be included in an amount of 0.01 to 5 parts by weight, 0.05 to 2 parts by weight, or 0.1 to 1 part by weight. More specifically, it may be included in an amount of 0.1 to 0.8 parts by weight or 0.1 to 0.5 parts by weight. When the content of the lithium by-product is within this range, side reactions in the slurry can be reduced, viscosity changes can be reduced, and aqueous processability can be improved. On the other hand, when the content of the lithium by-product is higher than this range, the slurry becomes basic during formation, which can cause side reactions or viscosity changes, resulting in poor aqueous processability.

[0092] The content of the lithium by-product can be calculated by measuring the amount of the HCl solution at a specific pH range during titration of the aqueous solution containing the negative active material with the HCl solution using a titrator.

[0093] The negative electrode active material may have an average particle size (D50) of 0.1 μm to 30 μm, specifically 1 μm to 20 μm, and more specifically 1 μm to 10 μm. When the average particle size is within this range, the active material's structural stability during charge and discharge is ensured, the problem of increased volume expansion / contraction caused by an excessively large particle size is prevented, and the problem of reduced initial efficiency caused by an excessively small particle size is prevented.

[0094] <Method of manufacturing negative electrode active material> One embodiment of the present invention is SiO xThe step of manufacturing preliminary silicon-based particles including (0 < x < 2); the step of mixing the preliminary silicon-based particles and an oxide containing one or more selected from the group consisting of Zr, B, Al, Zn, W, and Ti, or depositing the oxide on the preliminary silicon-based particles to provide the oxide on the surface of the preliminary silicon-based particles; the step of providing a carbon layer on at least a part of the surface of the preliminary silicon-based particles; the step of mixing the preliminary silicon-based particles provided with the carbon layer and a Li precursor and then performing heat treatment to manufacture silicon-based particles; and the step of mixing the silicon-based particles with at least one selected from the group consisting of an Al precursor, a P precursor, and a precursor containing Al and P to provide a surface layer on at least a part of the surface of the carbon layer. A method for manufacturing the negative electrode active material including these steps is provided.

[0095] The preliminary silicon-based particles can be manufactured by heating and vaporizing Si powder and SiO2 powder in a vacuum and then depositing the vaporized mixed gas.

[0096] The Si powder and SiO2 powder may be included in a weight ratio of 2:8 to 8:2, specifically, may be included in a weight ratio of 4:6 to 6:4 or 5:5.

[0097] Specifically, the mixed powder of the Si powder and SiO2 powder can be heat-treated at 1300°C to 1800°C, 1400°C to 1800°C, or 1400°C to 1600°C under vacuum.

[0098] The mixed gas vaporized by the heat treatment can be cooled under vacuum and deposited on a solid phase. Further, the deposited solid phase can be heat-treated in an inert atmosphere to manufacture preliminary silicon-based particles. The heat treatment may be performed at 500°C to 1,000°C or 700°C to 900°C.

[0099] The formed preliminary silicon-based particles can exist in the form of SiO x (x = 1).

[0100] Thereafter, the preliminary silicon-based particles can be mixed with an oxide containing at least one selected from the group consisting of Zr, B, Al, Zn, W, and Ti, or the oxide can be vapor-deposited onto the preliminary silicon-based particles to provide the oxide on the surfaces of the preliminary silicon-based particles.

[0101] The step of providing an oxide on the surface of the preliminary silicon-based particles may further include mixing the oxide and then pulverizing the mixed oxide.

[0102] The oxide may be contained in an amount of 0.01 to 0.5 parts by weight based on a total of 100 parts by weight of the mixture, specifically, 0.05 to 0.3 parts by weight, or 0.1 to 0.2 parts by weight.

[0103] The pulverization may be performed by a ball mill, a jet mill, or air classification, and is preferably performed through a ball mill process. The pulverization method is not limited thereto, and any pulverization method known in the art may be appropriately adopted. The pulverization process may adjust the particle size of the preliminary silicon-based particles and simultaneously provide the oxide on the surfaces of the preliminary silicon-based particles.

[0104] For example, when adjusting the particle size of the preliminary silicon-based particles using a ball mill, 5 to 20 sus ball media may be added, specifically 10 to 15 may be added, but is not limited thereto.

[0105] In the particle size adjustment step, the grinding time of the preliminary silicon-based negative electrode active material may be 2 hours to 5 hours, specifically 2 hours to 4 hours, and more specifically 3 hours, but is not limited thereto.

[0106] In the step of depositing the oxide on the preliminary silicon-based particles to provide the oxide on the surface of the preliminary silicon-based particles, the deposition step can be carried out through physical vapor deposition (PVD) using a source containing the oxide. The deposition method is not limited thereto, and deposition methods known in the art can be appropriately adopted. Through the deposition step, the oxide can be provided on the surface of the preliminary silicon-based particles.

[0107] Thereafter, a carbon layer can be provided on the surface of the preliminary silicon-based particles.

[0108] The carbon layer can be formed by using chemical vapor deposition (CVD) with a carbon-based substance, for example, a hydrocarbon gas, or by a method of carbonizing a substance serving as a carbon source.

[0109] Specifically, after the formed preliminary particles are introduced into a reactor, they can be formed by chemical vapor deposition (CVD) of a hydrocarbon gas at 600 to 1200 °C. The hydrocarbon gas may be at least one hydrocarbon gas selected from the group including methane, ethane, propane, and acetylene, and can be heat-treated at 900 °C to 1000 °C.

[0110] Thereafter, after mixing the preliminary silicon-based particles provided with the carbon layer and a Li precursor, heat treatment can be carried out to produce silicon-based particles.

[0111] The step of mixing the preliminary particles with the carbon layer formed and Li powder and then performing heat treatment can be carried out at 700 °C to 900 °C for 4 to 6 hours, and specifically, it may be carried out at 800 °C for 5 hours.

[0112] The silicon-based particles formed by the heat treatment contain SiO x (0 < x < 2) and a Li compound.

[0113] The silicon-based particles may contain, as the aforementioned Li compound, Li silicate, Li silicide, or Li oxide, etc.

[0114] The silicon-based particles can further adjust their particle size by methods such as ball mill, jet mill, or air classification, etc., and are not limited thereto.

[0115] At least a part of the surface of the silicon-based particles provided with the carbon layer as described above is provided with a lithium compound (lithium by-product). Specifically, in the process of forming preliminary particles containing SiO x (0 < x < 2), forming a carbon layer on the preliminary particles, and then doping with Li to produce the silicon-based particles described above, a lithium compound, that is, a lithium by-product formed by unreacted lithium, remains near the surface of the silicon-based particles.

[0116] Thereafter, a surface layer can be provided on at least a part of the surface of the carbon layer.

[0117] The step of providing a surface layer on at least a part of the surface of the carbon layer may include a step of mixing and reacting one or more selected from the group consisting of the silicon-based particles, an Al precursor, a P precursor, and a precursor containing Al and P.

[0118] In one embodiment, the step of providing a surface layer on at least a part of the surface of the carbon layer may include a step of mixing and reacting the silicon-based particles, a precursor containing Al, and a precursor containing P.

[0119] The precursor containing Al and P may be contained in an amount of 0.1 part by weight to 5 parts by weight based on 100 parts by weight of the total mixture. Specifically, it may be contained in an amount of 0.5 part by weight to 4 parts by weight, or may be contained in an amount of 1 part by weight to 3 parts by weight.

[0120] The precursor containing Al and P may be aluminum phosphate.

[0121] Specifically, 1) a step of dry-mixing and heat-treating the silicon-based particles and aluminum phosphate, or 2) a step of reacting the silicon-based particles and aluminum phosphate by mixing them in a solvent and then heat-treating to vaporize the solvent can form a surface layer on at least a part of the carbon layer surface. When forming a surface layer by the above method, a surface layer can be easily formed by reacting lithium by-products formed or remaining in the manufacturing process of the silicon-based particles with aluminum phosphate.

[0122] The aluminum phosphate is Al b P c O d It may be in the form of (0 < b ≤ 10, 0 < c ≤ 10, 0 < d ≤ 10). Specifically, it may be Al(PO3)3 or AlPO4, and is not limited thereto. Salts used in the industry for forming the surface layer can be appropriately adopted.

[0123] In another embodiment, the step of providing a surface layer on at least a part of the carbon layer surface may include a step of mixing and reacting the silicon-based particles, a precursor containing Al (aluminum precursor), and a precursor containing P (phosphorus precursor).

[0124] Specifically, 3) a step of dry-mixing and heat-treating the silicon-based particles, aluminum precursor, and phosphorus precursor, or 4) a step of reacting the silicon-based particles, aluminum precursor, and phosphorus precursor by mixing them in a solvent and then heat-treating to vaporize the solvent can form a surface layer on at least a part of the carbon layer surface. When forming a surface layer by the above method, a surface layer can be easily formed by reacting lithium by-products formed in the manufacturing process of the silicon-based particles, the aluminum precursor, and the phosphorus precursor.

[0125] The aluminum precursor is Al a O bIt can be aluminum oxide in the form of (0 < a ≤ 10, 0 < b ≤ 10), and specifically it may be Al2O3.

[0126] Alternatively, the aluminum precursor may be aluminum hydroxide, aluminum nitrate, aluminum sulfate, etc. Specifically, it may be Al(OH)3, Al(NO3)3·9H2O, or Al2(SO4)3, but is not limited thereto, and an aluminum precursor used in the industry for forming the surface layer can be appropriately adopted.

[0127] The phosphorus precursor is P c O d It may be phosphorus oxide in the form of (0 < c ≤ 10, 0 < d ≤ 10).

[0128] Or, the phosphorus precursor may be ammonium phosphate, diammonium phosphate, phosphoric acid, etc. Specifically, it may be (NH4)3PO 4、 (NH4)2HPO 4、 H3PO4, or NH4H2PO4, but is not limited thereto, and a phosphorus precursor used in the industry for forming the surface layer can be appropriately adopted.

[0129] The precursor containing Al and P may be a precursor containing Li, Al, P, and O (Li - Al - P - O system precursor).

[0130] In another embodiment, the step of providing a surface layer on at least a part of the carbon layer surface may include the step of mixing and reacting the silicon - based particles and a precursor containing Li, Al, P, and O (Li - Al - P - O system precursor).

[0131] Specifically, in step 5), the silicon-based particles and the Li-Al-P-O-based precursor are dry-mixed and heat-treated, or in step 6), after the silicon-based particles and the Li-Al-P-O-based precursor are mixed in a solvent, they are heat-treated while vaporizing the solvent to react the silicon-based particles and the Li-Al-P-O-based precursor, through which a surface layer can be formed on at least a part of the carbon layer surface. When forming the surface layer by the above method, the Li-Al-P-O-based precursor can be directly introduced to form the surface layer.

[0132] The Li-Al-P-O-based precursor is Li y Al z P w O v It may be in the form of (0 < y ≤ 10, 0 < z ≤ 10, 0 < w ≤ 10, 0 < v ≤ 10). Specifically, it may be a mixture or compound formed complexly from Li3PO4, AlPO4, Al(PO3)3, or LiAlO2, etc., and is not limited thereto. The configuration used in the industry for forming the surface layer can be appropriately adopted.

[0133] The precursor may be aluminum phosphate.

[0134] In the step of providing a surface layer on at least a part of the carbon layer surface, the heat treatment may be performed at 500°C to 700°C, specifically, it can be performed at 550°C to 650°C. However, it is not limited thereto and may vary depending on the salt or precursor used, etc. When the heat treatment temperature is higher than the above range, the surface layer is formed in a crystalline state, and it becomes difficult for Li ions to enter and exit through the surface layer, resulting in problems such as a decrease in resistance and life characteristics, and a decrease in capacity and / or efficiency. When the heat treatment temperature satisfies the above range, the reaction between the salt or precursor and the Li by-product occurs well, and the surface layer contains Li, so the durability of the formed negative electrode active material against moisture is increased, the lithium diffusion (Li dffusion) resistance on the surface of the negative electrode active material is decreased, and there is an effect of excellent discharge rate capability.

[0135] The solvent may be water or ethanol, and is not limited thereto. Solvents used in the art can be appropriately adopted.

[0136] The surface layer formed on at least a part of the surface of the carbon layer preferably contains Li y Al z P w O v (0 < y ≤ 10, 0 < z ≤ 10, 0 < w ≤ 10, 0 < v ≤ 10) phase, and the Li y Al z P w O v phase may be an amorphous phase.

[0137] The content of the surface layer is as described above.

[0138] <Negative electrode> [[ID=3a]]The negative electrode according to an embodiment of the present invention may contain the negative electrode active material described above.

[0139] 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. Further, the negative electrode active material layer may further contain a binder, a thickener and / or a conductive material.

[0140] The negative electrode active material layer can 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 surface of a current collector, followed by drying and rolling.

[0141] The negative electrode slurry may further contain an additional negative electrode active material.

[0142] As the additional negative electrode active material, compounds capable of reversible intercalation and deintercalation of lithium can be used. Specific examples include carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fibers, 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, and Al alloys; SiO It should be noted that in the original text, there is an error in the line "本発明の一実施態様による負極は、前述した負極活物質を含んでもよい。 " which is translated as "The negative electrode according to an embodiment of the present invention may contain the negative electrode active material described above. " Here, "may contain" is used instead of "may include" in the original Japanese text for better English expression. If you want to be more literal, it could be "may include", but "may contain" is also a common and appropriate translation in this context.β Examples of the negative electrode active material include metal oxides capable of doping and dedoping lithium, such as SnO2, vanadium oxide, lithium titanium oxide, and lithium vanadium oxide (0<β<2); or composites containing the metallic compounds and carbonaceous materials, such as Si-C composites or Sn-C composites. A mixture of two or more of these may be used. A thin film of metallic lithium may also be used as the negative electrode active material. The carbon material may be either low-crystalline carbon or high-crystalline carbon. Typical low-crystalline carbons are soft carbon and hard carbon, while typical high-crystalline carbons are amorphous, plate-like, flake-like, spherical, or fibrous natural or artificial graphite, Kish graphite, pyrolytic carbon, mesophase pitch-based carbon fiber, mesocarbon microbeads, mesophase pitches, and high-temperature-fired carbons such as petroleum or coal tar pitch-derived cokes.

[0143] The additional negative electrode active material may be a carbon-based negative electrode active material.

[0144] In one embodiment of the present invention, the weight ratio of the negative electrode active material and the additional negative electrode active material contained in the negative electrode slurry may be 10:90 to 90:10, specifically 10:90 to 50:50.

[0145] The negative electrode slurry may include a solvent for forming a negative electrode slurry. Specifically, the solvent for forming a negative electrode slurry may include at least one selected from the group consisting of distilled water, ethanol, methanol, and isopropyl alcohol, specifically distilled water, in order to facilitate dispersion of components.

[0146] The negative electrode slurry containing the negative electrode active material according to one embodiment of the present invention may have a pH of 7 to 11 at 25°C. When the pH of the negative electrode slurry satisfies this range, the rheological properties of the slurry are stabilized. On the other hand, if the pH of the negative electrode slurry is less than 7 or exceeds 11, decomposition of carboxymethyl cellulose (CMC) used as a thickener occurs, causing a decrease in the viscosity of the slurry and a decrease in the degree of dispersion of the active material contained in the slurry.

[0147] The negative electrode current collector is not particularly limited as long as it is conductive and does not induce chemical changes in the battery. For example, the current collector can be made of copper, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, or the like. Specifically, transition metals that adsorb carbon well, such as copper and nickel, can be used as the current collector. The thickness of the current collector can be 6 μm to 20 μm, but is not limited thereto.

[0148] The binder may include at least one selected from the group consisting of polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride, polyacrylonitrile, polymethylmethacrylate, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, 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 hydrogen is substituted with Li, Na, Ca, or the like, or may include various copolymers thereof.

[0149] The conductive material is not particularly limited as long as it does not induce chemical changes in the battery and has conductivity. For example, graphite such as natural graphite and 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.

[0150] The thickener may be, but is not limited to, carboxymethyl cellulose (CMC), and any thickener used in the technical field may be appropriately employed.

[0151] In one embodiment of the present invention, the weight ratio of the negative electrode active material and the additional negative electrode active material contained in the negative electrode slurry may be 1:99 to 30:70, specifically 5:95 to 30:70 or 10:90 to 20:80.

[0152] In one embodiment of the present invention, the total amount of the negative electrode active material contained in the negative electrode slurry may be 60 parts by weight to 99 parts by weight, specifically 70 parts by weight to 98 parts by weight, based on 100 parts by weight of the total solid content of the negative electrode slurry.

[0153] 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.

[0154] 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.

[0155] In one embodiment of the present invention, the thickener may be contained in an amount of 0.5 parts by weight to 25 parts by weight, specifically 0.5 parts by weight to 20 parts by weight, and more specifically 1 part by weight to 20 parts by weight, based on a total of 100 parts by weight of the solid content of the negative electrode slurry.

[0156] The negative electrode slurry according to an embodiment of the present invention may further include a solvent for forming the negative electrode slurry. Specifically, the solvent for forming the negative electrode slurry may include at least one selected from the group consisting of distilled water, ethanol, methanol, and isopropyl alcohol, specifically distilled water, in order to facilitate dispersion of components.

[0157] In one embodiment of the present invention, the solid content weight of the negative electrode slurry may be 20 parts by weight to 75 parts by weight, specifically 30 parts by weight to 70 parts by weight, based on a total of 100 parts by weight of the negative electrode slurry.

[0158] <Secondary battery> A secondary battery according to an embodiment of the present invention may include the anode according to the embodiment described above. Specifically, the secondary battery may include an anode, a cathode, a separator interposed between the cathode and the anode, and an electrolyte solution, and the anode is the same as the anode described above. Since the anode has been described above, detailed description thereof will be omitted.

[0159] 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 including the positive electrode active material.

[0160] The positive electrode current collector in the positive electrode is not particularly limited as long as it is conductive and does not induce chemical changes in the battery. For example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, etc. can be used. The positive electrode current collector may typically have a thickness of 3 μm to 500 μm, and fine irregularities can be formed on the collector surface to enhance the adhesive strength of the positive electrode active material. It can be used in various forms, such as a film, sheet, foil, net, porous material, foam, or nonwoven fabric.

[0161] The positive electrode active material may be a commonly used positive electrode active material, such as a layered compound or a compound substituted with one or more transition metals, such as lithium cobalt oxide (LiCoO2) or lithium nickel oxide (LiNiO2); a lithium iron oxide such as LiFe3O4; 1+c1 Mn 2-c1 O4 (0≦c1≦0.33), lithium manganese oxides such as LiMnO3, LiMn2O3, and LiMnO2; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, V2O5, and Cu2V2O7; chemical formula LiNi 1-c2 M c2 Ni-site type lithium nickel oxide represented by the chemical formula LiMnO2 (wherein M is at least one selected from the group consisting of Co, Mn, Al, Cu, Fe, Mg, B, and Ga, and 0.01≦c2≦0.5 is satisfied); 2-c3 M c3 Examples of suitable lithium manganese composite oxides include, but are not limited to, lithium manganese composite oxides represented by Li2Mn3MO8 (where M is at least one selected from the group consisting of Co, Ni, Fe, Cr, Zn, and Ta, and satisfies 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. The positive electrode may be Li metal.

[0162] The positive electrode active material layer may contain a positive electrode conductive material and a positive electrode binder in addition to the above-described positive electrode active material.

[0163] In this case, the positive electrode conductive material is used to impart conductivity to the electrode, and can be any material that has electronic conductivity without causing chemical changes in the battery that is constructed. Specific examples include graphite such as natural graphite and 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 powder or metal fiber such as copper, nickel, aluminum, and silver; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; and conductive polymers such as polyphenylene derivatives. These may be used alone or in combination of two or more.

[0164] The positive electrode binder improves adhesion between particles of the positive electrode active material and between the positive electrode active material and the positive electrode current collector. Specific examples of the positive electrode binder include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated EPDM, styrene-butadiene rubber (SBR), fluororubber, and various copolymers thereof. These may be used alone or in combination.

[0165] The separator separates the negative electrode and positive electrode and provides a path for lithium ions to move. Any separator typically used in secondary batteries can be used without particular limitations. In particular, a separator that exhibits low resistance to ion migration in the electrolyte and excellent electrolyte humidification is preferred. Specifically, a porous polymer film, such as a porous polymer film made from a polyolefin polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, or an ethylene / methacrylate copolymer, or a laminate structure of two or more layers thereof, may be used. Conventional porous nonwoven fabrics, such as nonwoven fabrics made from high-melting-point glass fibers or polyethylene terephthalate fibers, may also be used. To ensure heat resistance or mechanical strength, a separator coated with a ceramic component or a polymer material may also be used, and may be used in a single-layer or multi-layer structure.

[0166] Examples of the electrolytic solution 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 manufacturing lithium secondary batteries.

[0167] Specifically, the electrolyte may contain a non-aqueous organic solvent and a metal salt.

[0168] Examples of the non-aqueous organic solvent that may be used include aprotic organic solvents such as N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, gamma-butyrolactone, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolane, formamide, dimethylformamide, dioxolane, acetonitrile, nitromethane, methyl formate, methyl acetate, phosphoric acid triester, trimethoxymethane, dioxolane derivatives, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivatives, tetrahydrofuran derivatives, ethers, methyl propionate, and ethyl propionate.

[0169] In particular, among the carbonate-based organic solvents, ethylene carbonate and propylene carbonate, which are cyclic carbonates, are preferably used because they are high-viscosity organic solvents with high dielectric constants and can dissociate lithium salts well. When such cyclic carbonates are mixed with linear carbonates having low viscosity and low dielectric constants, such as dimethyl carbonate and diethyl carbonate, in an appropriate ratio, an electrolyte solution having high electrical conductivity can be prepared, and therefore, these cyclic carbonates are more preferably used.

[0170] The metal salt may be a lithium salt, which is a substance that is easily dissolved in the non-aqueous electrolyte solution. For example, the anion of the lithium salt may be 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 selected from the group consisting of:

[0171] In addition to the components of the electrolyte, the electrolyte may further include one or more additives, such as a haloalkylene carbonate compound such as difluoroethylene carbonate, pyridine, triethyl phosphite, triethanolamine, cyclic ether, ethylenediamine, n-glyme, hexaphosphoric acid triamide, nitrobenzene derivatives, sulfur, quinoneimine 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 life characteristics of the battery, suppressing a decrease in battery capacity, and improving the discharge capacity of the battery.

[0172] According to another embodiment of the present invention, there is provided a battery module including the secondary battery as a unit cell, and a battery pack including the same. The battery module and the battery pack include the secondary battery having high capacity, excellent rate-limiting characteristics, and excellent cycle characteristics, and can be used as a power source for medium- to large-sized devices selected from the group consisting of electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, and power storage systems. [Example]

[0173] <Examples and Comparative Examples> Example 1 100g of powder, in which Si and SiO2 were mixed in a 1:1 molar ratio, was vacuum heated in a reactor at a sublimation temperature of 1,400°C. The vaporized Si and SiO2 mixed gas was then reacted in a vacuum cooling zone with a cooling temperature of 800°C to solidify. Then, heat treatment was carried out in an inert atmosphere at a temperature of 800°C to produce preliminary silicon-based particles. The preliminary silicon-based particles and ZrO2 were then added in a weight ratio of 99.9:0.1, and 15 SUS ball media were added using a ball mill, followed by pulverization for 3 hours to a particle size of 6μm (D 50 Then, the silicon-based particles were placed in the hot zone of a CVD apparatus while maintaining an inert atmosphere by flowing Ar gas, and methane was blown into the hot zone at 900°C using Ar as a carrier gas. -1 The reaction was carried out at torr to form a carbon layer on the surface of the silicon-based particles.

[0174] 10 g of Li metal powder was added to 90 g of the silicon-based particles, and heat treatment was carried out at a temperature of 800° C. in an inert atmosphere to prepare Li-doped silicon-based particles.

[0175] 98.5 g of the silicon-based particles were mixed with 1.5 g of Al(PO3)3, and then heat-treated at 600° C. to prepare a negative electrode active material in which a surface layer containing Li, Al, and P was formed on the surface of the silicon-based particles.

[0176] D of the negative electrode active material 50 is 6 μm, and the BET specific surface area is 2.5 m 2 / g.

[0177] The negative electrode active material contained ZrO2 at the interface between the silicon-based particles and the carbon layer, and ICP analysis of the negative electrode active material revealed that the contents of Li, Al, P, and Zr were 9.5 wt%, 0.15 wt%, 0.5 wt%, and 0.06 wt%, respectively, based on a total of 100 wt% of the negative electrode active material.

[0178] Example 2 A negative electrode active material was produced in the same manner as in Example 1, except that the preliminary silicon-based particles and ZrO2 were added in a weight ratio of 99.8:0.2 and then milled using a ball mill.

[0179] D of the negative electrode active material 50 is 6 μm, and the BET specific surface area is 2.5 m 2 / g.

[0180] The negative electrode active material contained ZrO2 at the interface between the silicon-based particles and the carbon layer, and ICP analysis of the negative electrode active material revealed that the contents of Li, Al, P, and Zr were 9.5 wt%, 0.15 wt%, 0.5 wt%, and 0.12 wt%, respectively, based on a total of 100 wt% of the negative electrode active material.

[0181] Example 3 A negative electrode active material was prepared in the same manner as in Example 1, except that 97.0 g of the silicon-based particles was mixed with 3.0 g of Al(PO3)3.

[0182] D of the negative electrode active material 50 is 6 μm, and the BET specific surface area is 2.5 m 2 / g.

[0183] The negative electrode active material contained ZrO2 at the interface between the silicon-based particles and the carbon layer, and ICP analysis of the negative electrode active material revealed that the contents of Li, Al, P, and Zr were 9.5 wt%, 0.3 wt%, 1.1 wt%, and 0.06 wt%, respectively, based on a total of 100 wt% of the negative electrode active material.

[0184] Example 4 A negative active material was prepared in the same manner as in Example 1, except that the preliminary silicon-based particles and B2O3 were mixed in a weight ratio of 99.9:0.1 and then milled using a ball mill.

[0185] D of the negative electrode active material 50 is 6 μm, and the BET specific surface area is 2.5 m 2 / g.

[0186] The negative electrode active material contained B2O3 at the interface between the silicon-based particles and the carbon layer, and ICP analysis of the negative electrode active material revealed that the contents of Li, Al, P, and B were 9.5 wt%, 0.15 wt%, 0.5 wt%, and 0.03 wt%, respectively, based on a total of 100 wt% of the negative electrode active material.

[0187] Example 5 A negative electrode active material was produced in the same manner as in Example 1, except that the preliminary silicon-based particles and Al2O3 were added in a weight ratio of 99.9:0.1 and then milled using a ball mill.

[0188] D of the negative electrode active material 50 is 6 μm, and the BET specific surface area is 2.5 m 2 / g.

[0189] The negative electrode active material contained Al2O3 at the interface between the silicon-based particles and the carbon layer, and ICP analysis of the negative electrode active material revealed that the Li, Al, and P contents were 9.5 wt%, 0.19 wt%, and 0.5 wt%, respectively, based on a total of 100 wt% of the negative electrode active material (the Al content at the interface was 0.04 wt%).

[0190] Example 6 A negative electrode active material was produced in the same manner as in Example 1, except that the preliminary silicon-based particles and ZnO were added in a weight ratio of 99.9:0.1 and then milled using a ball mill.

[0191] D of the negative electrode active material 50 is 6 μm, and the BET specific surface area is 2.5 m 2 / g.

[0192] The negative electrode active material contained ZnO at the interface between the silicon-based particles and the carbon layer, and ICP analysis of the negative electrode active material revealed that the contents of Li, Al, P, and Zn were 9.5 wt%, 0.15 wt%, 0.5 wt%, and 0.07 wt%, respectively, based on a total of 100 wt% of the negative electrode active material.

[0193] Example 7 The negative electrode active material was produced in the same manner as in Example 1, except that the preliminary silicon-based particles and WO3 were mixed in a weight ratio of 99.9:0.1 and then milled using a ball mill.

[0194] D of the negative electrode active material 50 is 6 μm, and the BET specific surface area is 2.5 m 2 / g.

[0195] The negative electrode active material contained WO3 at the interface between the silicon-based particles and the carbon layer, and ICP analysis of the negative electrode active material revealed that the contents of Li, Al, P, and W were 9.5 wt%, 0.15 wt%, 0.5 wt%, and 0.07 wt%, respectively, based on a total of 100 wt% of the negative electrode active material.

[0196] Example 8 A negative electrode active material was produced in the same manner as in Example 1, except that the preliminary silicon-based particles and TiO2 were added in a weight ratio of 99.9:0.1 and then milled using a ball mill.

[0197] D of the negative electrode active material 50 is 6 μm, and the BET specific surface area is 2.5 m 2 / g.

[0198] The negative electrode active material contained TiO2 at the interface between the silicon-based particles and the carbon layer, and ICP analysis of the negative electrode active material revealed that the contents of Li, Al, P, and Ti were 9.5 wt%, 0.15 wt%, 0.5 wt%, and 0.05 wt%, respectively, based on a total of 100 wt% of the negative electrode active material.

[0199] Comparative Example 1 A negative electrode active material was produced in the same manner as in Example 1, except that the preliminary silicon-based particles and Zr were added in a weight ratio of 99.9:0.1 and then milled using a ball mill.

[0200] D of the negative electrode active material 50 is 6 μm, and the BET specific surface area is 2.5 m 2 / g.

[0201] The negative electrode active material contained Zr at the interface between the silicon-based particles and the carbon layer, and ICP analysis of the negative electrode active material revealed that the contents of Li, Al, P, and Zr were 9.5 wt%, 0.15 wt%, 0.5 wt%, and 0.08 wt%, respectively, based on a total of 100 wt% of the negative electrode active material.

[0202] Comparative Example 2 After adding only the preliminary silicon-based particles (without adding ZrO), silicon-based particles were prepared using a ball mill, and a negative electrode active material was prepared in the same manner as in Example 1, except that 98.5 g of the Li-doped silicon-based particles were mixed with 1.5 g of Al(PO) and 0.1 g of ZrO.

[0203] D of the negative electrode active material 50 is 6 μm, and the BET specific surface area is 2.5 m 2 / g.

[0204] The surface layer of the negative electrode active material contained ZrO2, and when the negative electrode active material was analyzed by ICP, the contents of Li, Al, P, and Zr were 9.5 wt%, 0.15 wt%, 0.5 wt%, and 0.07 wt%, respectively, based on a total of 100 wt% of the negative electrode active material.

[0205] Comparative Example 3 A negative electrode active material was produced in the same manner as in Example 1, except that only the preliminary silicon-based particles were added (ZrO2 was not added) and then silicon-based particles were produced using a ball mill.

[0206] D of the negative electrode active material 50 is 6 μm, and the BET specific surface area is 2.5 m 2 / g.

[0207] When the negative active material was analyzed by ICP, the contents of Li, Al, and P were 9.5 wt%, 0.15 wt%, and 0.5 wt%, respectively, based on a total of 100 wt% of the negative active material.

[0208] Comparative Example 4 A negative electrode active material was prepared in the same manner as in Example 1, except that Al(PO3)3 was not added to the Li-doped silicon-based particles, and thus a surface layer containing Li, Al, and P was not formed.

[0209] D of the negative electrode active material 50 is 6 μm, and the BET specific surface area is 2.5 m 2 / g.

[0210] The negative electrode active material contained ZrO2 at the interface between the silicon-based particles and the carbon layer, and ICP analysis of the negative electrode active material revealed that the contents of Li, Al, P, and Zr were 9.8 wt%, 0.0 wt%, 0.0 wt%, and 0.06 wt%, respectively, based on a total of 100 wt% of the negative electrode active material.

[0211] The compositions of the negative electrode active materials prepared in the examples and comparative examples are as shown in Table 1 below.

[0212] [Table 1]

[0213] The contents of the elements were confirmed by ICP analysis using an inductively coupled plasma optical emission spectrometer (Perkin-Elmer 7300 ICP-OES, AVIO 500).

[0214] The location of the oxide contained in the negative electrode active material (the interface between the silicon-based particles and the carbon layer) was analyzed by XPS.

[0215] The content of the carbon layer was confirmed under oxygen conditions by combustion elemental analysis (Bruker G4 ICARUS).

[0216] D of the negative electrode active material 50 was analyzed using the PSD measurement method using a microtrac device.

[0217] The specific surface area was measured using a BET measurement device (BEL-SORP-MAX, Nippon Bell) by degassing at 200°C for 8 hours and then performing N2 adsorption / desorption at 77K.

[0218] <Experimental example: Discharge capacity, initial efficiency, and life (capacity retention) characteristic evaluation> Negative electrodes and batteries were fabricated using the negative electrode active materials of the examples and comparative examples, respectively.

[0219] The negative electrode active material, carbon black as a conductive material, and PAA (polyacrylic acid) as a binder were mixed in a weight ratio of 80:10:10 to prepare a mixture. 7.8 g of distilled water was then added to 5 g of the mixture and stirred to prepare a negative electrode slurry. The negative electrode slurry was applied to a copper (Cu) metal thin film as a negative electrode current collector with a thickness of 20 μm and dried. The circulating air temperature was 60°C. The mixture was then rolled and dried in a vacuum oven at 130°C for 12 hours to prepare a negative electrode.

[0220] The manufactured negative electrode and 1.7671 cm 2 A lithium (Li) metal thin film cut into a circular shape was used as the positive electrode. A porous polyethylene separator was placed between the positive electrode and the negative electrode, and an electrolyte solution of 1M LiPF6 dissolved in a 7:3 volumetric mixture of ethyl methyl carbonate (EMC) and ethylene carbonate (EC) with 0.5 parts by weight of vinylene carbonate was dissolved was injected to fabricate a lithium coin half-cell.

[0221] The produced batteries were charged and discharged, and the discharge capacity, initial efficiency, and capacity retention rate were evaluated. The results are shown in Table 2 below.

[0222] The first and second cycles were charged and discharged at 0.1 C, and the third to 49th cycles were charged and discharged at 0.5 C. The 50th cycle was completed in a charged state (with lithium contained in the negative electrode).

[0223] Charging conditions: CC (constant current) / CV (constant voltage) (5mV / 0.005C current cut-off) Discharge condition: CC (constant current) condition 1.5V

[0224] The discharge capacity (mAh / g) and initial efficiency (%) were calculated from the results of a single charge / discharge. Specifically, the initial efficiency (%) was calculated using the following formula:

[0225] Initial efficiency (%) = (single discharge capacity / single charge capacity) x 100

[0226] The capacity retention rate was calculated as follows.

[0227] Capacity retention rate (%) = (49 times discharge capacity / 1 time discharge capacity) × 100

[0228] <Experimental example: Processability (Shear viscosity) characteristic evaluation> As part of the processability evaluation, a slurry was prepared by mixing graphite, the negative electrode active material, carbon black, CMC, and SBR in a weight ratio of 77:20:1:1:1. The change in shear viscosity at a shear rate of 1 Hz was measured and shown in Table 2. Specifically, the change in shear viscosity (%) was calculated using the following formula:

[0229] Change in shear viscosity (%) = ((shear viscosity of slurry after 48 hours - shear viscosity of slurry immediately after mixing) / shear viscosity of slurry immediately after mixing) × 100

[0230] [Table 2]

[0231] In Table 2, it was confirmed that the negative electrode active materials used in Examples 1 to 8 contain oxides at the interface between the silicon-based particles and the carbon layer, and contain a surface layer containing Li, Al, and P, which reduces the reactivity of silicate, which is highly reactive with water or basicity, and can easily block contact with the outside, thereby improving the capacity retention rate and processability of the battery.

[0232] On the other hand, Comparative Example 1 used a negative electrode active material containing Zr instead of an oxide, and since Zr acts as a metal impurity, the discharge capacity, initial efficiency, and processability of the battery decreased. In particular, it was confirmed that lithium deposition occurred due to Zr during the battery cycle, and the capacity retention rate was hardly secured.

[0233] Comparative Examples 2 and 3 used negative electrode active materials in which oxide was contained in the surface layer or which contained no oxide. It was confirmed that it was difficult to reduce the reactivity of silicate in the silicon-based particles, and side reactions of the slurry occurred, resulting in a decrease in the capacity retention rate and processability of the battery.

[0234] Comparative Example 4, which concerns an anode active material having no surface layer, not only exhibited low discharge capacity and initial efficiency, but also significantly decreased capacity retention and processability. That is, even if an oxide such as ZrO2 is present between the silicon-based particles and the carbon layer as in Comparative Example 4, the absence of a surface layer did not improve capacity retention and processability. In fact, it was confirmed that the capacity retention and processability were further decreased compared to Comparative Example 3, which did not have an oxide.

Claims

1. SiO ｘ (0<x<2) and silicon-based particles comprising a Li compound; a carbon layer provided on at least a portion of the surface of the silicon-based particle; and a surface layer containing Li, Al and P provided on at least a portion of the surface of the carbon layer; Including, an oxide containing at least one selected from the group consisting of Zr, B, Al, Zn, W, and Ti provided at an interface between the silicon-based particle and the carbon layer; The negative electrode active material, wherein Zr, B, Al, Zn, W, and Ti contained in the oxide are each contained in an amount of 0.003 parts by weight to 0.2 parts by weight, based on a total of 100 parts by weight of the negative electrode active material.

2. The oxide is ZrO ２ , B ２ O ３ , Al ２ O ３ , ZnO, WO ３ and TiO ２ The negative electrode active material according to claim 1 , comprising at least one selected from the group consisting of:

3. The negative electrode active material according to claim 1 , wherein the oxide is provided adjacent to the surface of the silicon-based particle.

4. The negative electrode active material according to claim 1 , wherein the oxide is contained in an amount of 0.01 parts by weight to 0.5 parts by weight based on a total of 100 parts by weight of the negative electrode active material.

5. 2. The negative electrode active material according to claim 1, wherein Zr, B, Al, Zn, W, and Ti contained in the oxide are each contained in an amount of 0.004 parts by weight to 0.17 parts by weight, based on a total of 100 parts by weight of the negative electrode active material.

6. The surface layer is Li ｙ Al ｚ P ｗ O ｖ The negative electrode active material according to claim 1 , comprising a (0<y≦10, 0<z≦10, 0<w≦10, 0<v≦10) phase.

7. 2. The negative electrode active material according to claim 1, wherein the surface layer comprises at least one selected from the group consisting of aluminum oxide, phosphate, lithium oxide, aluminum phosphate, lithium salt, lithium phosphate, and lithium aluminate.

8. The negative electrode active material according to claim 1 , wherein the surface layer is contained in an amount of more than 0 parts by weight and not more than 10 parts by weight based on a total of 100 parts by weight of the negative electrode active material.

9. The negative electrode active material according to claim 1 , comprising 0.1 parts by weight to 40 parts by weight of Li element based on a total of 100 parts by weight of the negative electrode active material.

10. The negative electrode active material according to claim 1 , wherein the carbon layer is an amorphous carbon layer.

11. The negative electrode active material according to claim 1 , wherein the carbon layer is included in an amount of 0.1 parts by weight to 50 parts by weight based on a total of 100 parts by weight of the negative electrode active material.

12. SiO ｘ preparing preliminary silicon-based particles comprising (0<x<2); mixing the preliminary silicon-based particles with an oxide containing at least one selected from the group consisting of Zr, B, Al, Zn, W, and Ti, or depositing the oxide on the preliminary silicon-based particles to provide the oxide on the surfaces of the preliminary silicon-based particles; providing a carbon layer on at least a portion of the surface of the preliminary silicon-based particles; mixing the preliminary silicon-based particles having the carbon layer thereon with a Li precursor, and then heat-treating the mixture to prepare silicon-based particles; and mixing the silicon-based particles with at least one selected from the group consisting of an Al precursor, a P precursor, and a precursor containing Al and P, to form a surface layer on at least a portion of the carbon layer surface; The method for producing the negative electrode active material according to claim 1 , comprising:

13. The method of claim 12 , wherein the step of providing the oxide on the surface of the preliminary silicon-based particles further comprises a pulverization step.

14. A negative electrode comprising the negative electrode active material according to claim 1 .

15. A secondary battery comprising the negative electrode according to claim 14.

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