Negative electrode active material, method for producing negative electrode active material, negative electrode composition, negative electrode for lithium secondary battery containing the same, and lithium secondary battery containing the negative electrode

Abstract

The present application relates to a negative electrode active material, a method for manufacturing the negative electrode active material, a negative electrode composition, a negative electrode for a lithium secondary battery including the same, and a lithium secondary battery including the negative electrode.

Description

Technical Field

[0001] This application claims the benefit of the filing date of Korean Patent Application No. 10-2022-0110091, filed with the Korean Intellectual Property Office on August 31, 2022, and all of its contents are incorporated herein by reference.

[0002] This application relates to a negative electrode active material, a method for manufacturing the same, a negative electrode composition, a negative electrode for a lithium secondary battery including the same, and a lithium secondary battery including the negative electrode.

Background Art

[0003] Due to the rapid increase in the use of fossil fuels, the demand for alternative and clean energy has been increasing. As part of this, the fields of power generation and energy storage using electrochemical reactions are the most actively studied.

[0004] Currently, a typical example of an electrochemical device using such electrochemical energy is a secondary battery, and its usage area is increasingly expanding.

[0005] As the technology development and demand for mobile devices increase, the demand for secondary batteries as an energy source has been rapidly increasing. Among such secondary batteries, lithium secondary batteries having a high energy density, voltage, long cycle life, and low self-discharge rate have been commercialized and widely used. In addition, research on methods for manufacturing high-density electrodes with a higher energy density per unit volume as electrodes for such high-capacity lithium secondary batteries has been actively underway.

[0006] Generally, a secondary battery is composed of a positive electrode, a negative electrode, an electrolyte, and a separator. The negative electrode includes a negative electrode active material that inserts and desorbs lithium ions emitted from the positive electrode, and silicon-based particles having a large discharge capacity can be used as the negative electrode active material.

[0007] Especially in recent years, in response to the demand for high-density energy batteries, research has been actively carried out on methods to increase the capacity by using silicon-based compounds such as Si / C and SiOx, which have a capacity more than 10 times larger than that of graphite-based materials, as the negative electrode active material. However, in the case of silicon-based compounds, which are high-capacity materials, although the capacity is large compared to the conventionally used graphite, there is a problem that the volume rapidly expands during the charging process, breaking the conductive path and degrading the battery characteristics.

[0008] Therefore, in order to solve the problems when using silicon-based compounds as the negative electrode active material, various solutions have been discussed, such as a solution to adjust the driving potential, a method of further coating a thin film on the active material layer, a method to suppress the volume expansion itself, such as a method to adjust the particle size of the silicon-based compound, or various solutions to prevent the conductive path from being broken. However, in the case of the above solutions, they may rather reduce the performance of the battery, so there are limitations in application, and there are still limitations in the commercialization of manufacturing negative electrode batteries with a high content of silicon-based compounds.

[0009] In addition, research is being carried out to reduce the electrode resistance in order to ensure the life stability of electrodes using silicon-based compounds. However, in the production of slurries containing silicon-based active materials, problems such as gas generation due to the reaction with the solvent still occur, and problems such as non-uniform electrode coating and degradation of life characteristics have occurred.

[0010] Therefore, even when using silicon-based active materials as the negative electrode active material to improve the capacity performance, research on the silicon-based active material itself is necessary, which can prevent the damage of the conductive path due to the volume expansion of the silicon-based compound and suppress the gas generation during slurry formation.

Prior Art Documents

Patent Documents

[0011]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0012] When producing a silicon-based active material by a chemical processing method instead of a conventional grinding processing method, the physical properties of the silicon-based active material itself can be adjusted. During the lithium insertion / desorption reaction, it was confirmed that the reaction occurs uniformly and the stress received by the silicon-based active material is reduced. However, even in this case, gas generation due to the reaction between silicon and the slurry solvent during slurry production has become a problem, and it has been found that such a problem can be solved when a coating layer having a specific composition is formed on the silicon-based active material produced as described above.

[0013] Accordingly, the present application relates to a negative electrode active material, a method for producing a negative electrode active material, a negative electrode composition, a negative electrode for a lithium secondary battery including the same, and a lithium secondary battery including the negative electrode, which can solve the above-described problems.

Means for Solving the Problems

[0014] One embodiment of the present specification provides a negative electrode active material including a silicon-based active material; and a silicon oxide coating layer surrounding at least a part of the outer surface of the silicon-based active material, wherein an oxygen (O) atom content of the silicon oxide coating layer is 40% or more based on 100% of all atoms included in the silicon oxide coating layer, the silicon-based active material includes one or more selected from the group consisting of SiOx (x = 0) and SiOx (0 < x < 2), and the silicon-based active material includes 70 parts by weight or more of the SiOx (x = 0) based on 100 parts by weight of the silicon-based active material.

[0015] In another embodiment, a step of chemically reacting a silane gas to deposit a silicon-based active material on a substrate; a step of obtaining the silicon-based active material deposited on the substrate; and a step of forming silicon oxide on the surface of the silicon-based active material; A method for manufacturing a negative electrode active material, wherein the step of forming the silicon oxide includes oxidizing the silicon-based active material through heat treatment or chemical treatment; or coating the surface of the silicon-based active material with silicon oxide; And including a silicon oxide coating layer surrounding at least a part of the outer surface of the silicon-based active material, and the oxygen (O) atom content of the silicon oxide coating layer is 40% or more based on 100% of all atoms contained in the silicon oxide coating layer. A method for manufacturing a negative electrode active material is provided.

[0016] In another embodiment, an attempt is made to provide a negative electrode composition including a negative electrode active material according to the present application; a negative electrode conductive material; and a negative electrode binder.

[0017] In another embodiment, an attempt is made to provide a negative electrode for a lithium secondary battery, including a negative electrode current collector layer; and a negative electrode active material layer provided on one or both surfaces of the negative electrode current collector layer, wherein the negative electrode active material layer includes the negative electrode composition according to the present application or a cured product thereof.

[0018] Finally, a lithium secondary battery including a positive electrode; a negative electrode for a lithium secondary battery according to the present application; a separator provided between the positive electrode and the negative electrode; and an electrolyte is provided.

Effects of the Invention

[0019] The negative electrode active material of the present invention, as a silicon-based active material, contains at least one selected from the group consisting of SiOx (x = 0) and SiOx (0 < x < 2). Based on 100 parts by weight of the silicon-based active material, it contains 70 parts by weight or more of the SiOx (x = 0), that is, while having a pure Si (Pure Si) active material, different from the conventional pulverization processing method, it controls the reaction conditions of the chemical method to generate (silane gas), and thereby contains a silicon-based active material that satisfies certain physical properties. When using the silicon-based active material manufactured in this way, it becomes possible to react uniformly during the insertion and desorption reactions of lithium during charge and discharge, reduce the stress received by the silicon-based active material, and relieve the cracking of particles, thereby improving the life of the electrode.

[0020] In addition, this application is characterized in that a silicon oxide coating layer under specific conditions is formed on at least a part of the outer surface of the silicon-based active material manufactured as described above. Thereby, the silicon oxide coating layer acts as a protective layer, suppresses the reaction between the surface of the silicon-based active material and the solvent during slurry formation, prevents the hydrogen generation reaction, and thereby has the characteristic of improving the non-uniform electrode coating due to bubble generation during electrode coating.

Brief Description of the Drawings

[0021]

Figure 1

Figure 2

Figure 3

Modes for Carrying Out the Invention

[0022] Before explaining the present invention, first, some terms are defined. In this specification, when a part "includes" a certain component, this means that, unless otherwise stated to the contrary, it does not exclude other components, but may further include other components.

[0023] In this specification, "p to q" means the range of "p or more and q or less". In this specification, the "specific surface area" is measured by the BET method, specifically, it is calculated from the nitrogen gas adsorption amount at liquid nitrogen temperature (77K) using BELSORP-mini II of BEL Japan, Inc. That is, in this application, the BET specific surface area may mean the specific surface area measured by the above measurement method.

[0024] In this specification, "Dn" means the particle size distribution and means the particle size at the n% point of the cumulative particle number distribution by particle size. That is, D50 is the particle size (average particle size) at the 50% point of the cumulative particle number distribution by particle size, D90 is the particle size at the 90% point of the cumulative particle number distribution by particle size, and D10 is the particle size at the 10% point of the cumulative particle number distribution by particle size. On the other hand, the average particle size can be measured using the laser diffraction method. Specifically, after dispersing the powder to be measured in a dispersion medium, it is introduced into a commercially available laser diffraction particle size measuring device (for example, Microtrac S3500), and the difference in the diffraction pattern due to the particle size when the particles pass through the laser beam is measured to calculate the particle size distribution.

[0025] In one embodiment of this application, the particle size or diameter can mean the average diameter or representative diameter of each particle forming the metal powder.

[0026] In this specification, the meaning that a polymer includes a certain monomer in monomer units means that the monomer participates in a polymerization reaction and is included as a repeating unit in the polymer. In this specification, when a polymer is said to include a monomer, this is interpreted in the same way as the polymer including the monomer in monomer units.

[0027] In this specification, unless otherwise specified as "homopolymer", the term "polymer" is understood to be used in a broad sense including copolymers.

[0028] In this specification, the weight-average molecular weight (Mw) and the number-average molecular weight (Mn) are the polystyrene-equivalent molecular weights measured by Gel Permeation Chromatography (GPC) using monodisperse polystyrene polymers (standard samples) of various degrees of polymerization commercially available for molecular weight measurement as the reference substance. In this specification, unless otherwise specified, the molecular weight means the weight-average molecular weight.

[0029] Hereinafter, for those with ordinary knowledge in the technical field to which the present invention pertains to easily implement the present invention, a detailed description will be given with reference to the drawings. However, the present invention can be embodied in various different forms and is not limited to the following description.

[0030] One embodiment of this specification includes a silicon-based active material; and a silicon oxide coating layer surrounding at least a part of the outer surface of the silicon-based active material, wherein the oxygen (O) atom content of the silicon oxide coating layer is 40% or more based on 100% of all atoms contained in the silicon oxide coating layer, the silicon-based active material includes one or more selected from the group consisting of SiOx (x = 0) and SiOx (0 < x < 2), and based on 100 parts by weight of the silicon-based active material, it contains 70 parts by weight or more of SiOx (x = 0), providing a negative electrode active material.

[0031] The negative electrode active material according to this application includes a silicon oxide coating layer surrounding at least a part of the surface of a silicon-based active material manufactured by a specific manufacturing method. Thus, the silicon oxide coating layer acts as a protective layer, suppressing the reaction between the surface of the silicon-based active material and the solvent during slurry formation to prevent the hydrogen generation reaction, and thereby having the characteristic of improving the non-uniform electrode coating caused by bubble generation during electrode coating.

[0032] In one embodiment of the present application, a negative electrode active material is provided in which the thickness of the silicon oxide coating layer is 1 nm or more and 3 μm or less.

[0033] In still another embodiment, the thickness of the silicon oxide coating layer may be 1 nm or more and 3 μm or less, preferably 2 nm or more and 3 μm or less, and more preferably 3 nm or more and 3 μm or less.

[0034] By satisfying the above range for the thickness of the silicon oxide coating layer, it is possible to easily prevent contact between the solvent and the silicon-based active material, and further maximize the content of the silicon-based active material with the above thickness range, resulting in excellent capacity characteristics.

[0035] That is, in the silicon-based active material, an SiOx layer is formed through the reaction between silicon on the particle surface and OH ions in the slurry solvent during slurry formation, and at the same time, hydrogen gas is generated. Since such a layer has low electrical conductivity, when it is thickly formed in the active material, the resistance of the active material itself increases, and the life retention performance deteriorates due to the high resistance. The main feature of the present application is that the silicon oxide layer within the above thickness range is easily and intentionally formed during the manufacturing process of the silicon-based active material, thereby solving the problem of deterioration of the life retention performance as described above.

[0036] In one embodiment of the present application, a negative electrode active material is provided in which the area of the silicon oxide coating layer is 90% or more based on the outer surface of the silicon-based active material.

[0037] The area of the coating can be understood to mean the degree to which the silicon oxide coating layer is coated based on the outer surface of the silicon-based active material. That is, when the silicon oxide coating layer surrounds the silicon-based active material entirely, the area of the coating can be 100%, and at this time, it can be understood that the surface of the silicon-based active material is isolated from the outside, that is, cut off by the silicon oxide coating layer.

[0038] In one embodiment of the present application, the area of the silicon oxide coating layer may be 90% or more, 91% or more, 92% or more based on the outer surface of the silicon-based active material, and may satisfy the range of 100% or less, 99% or less, 95% or less.

[0039] By having the area of the silicon oxide coating layer as described above, gas generation can be more easily suppressed, and in the future, when included in the electrode, it will have the characteristic of being able to easily play the role of the silicon-based active material. In particular, the silicon oxide coating layer according to the present application is used to exhibit a gas generation suppression effect. When the area of the silicon oxide coating layer is 100%, it can block contact with water in a slurry state and has the characteristic of reducing gas generation.

[0040] In one embodiment of the present application, the silicon oxide coating layer provides a negative electrode active material containing at least one selected from the group consisting of crystalline silicon; and amorphous silicon;.

[0041] In one embodiment of the present application, the silicon oxide coating layer contains crystalline silicon.

[0042] In one embodiment of the present application, the silicon oxide coating layer contains amorphous silicon.

[0043] In one embodiment of the present application, the oxygen (O) atom content of the silicon oxide coating layer provides a negative electrode active material containing 40% or more based on 100% of all atoms contained in the silicon oxide coating layer.

[0044] In another embodiment, the oxygen (O) atom content of the silicon oxide coating layer contains 40% or more, preferably 40.5% or more, more preferably 41% or more based on 100% of all atoms contained in the silicon oxide coating layer, and can satisfy the range of 70% or less, 50% or less, 45% or less.

[0045] The oxygen (O) atom content of the silicon oxide coating layer can mean the content of oxygen atoms when the atoms contained in the entire silicon oxide are defined as 100%. Specifically, the silicon oxide coating layer may contain oxygen and silicon atoms, and can mean the oxygen atom content when the total of the oxygen and silicon atoms is defined as 100%.

[0046] As described above, when the oxygen atom content of the silicon oxide coating layer is within the above range, the silicon oxide coating layer satisfies the above composition and has the characteristic of easily blocking the OH ions of the silicon-based active material and the external slurry solvent. In particular, when the proportion of O in SiO2 with respect to the silicon oxide coating layer itself is less than the above range, there is a possibility of causing a problem that relatively more defects occur.

[0047] In one embodiment of the present application, the silicon-based active material includes at least one selected from the group consisting of SiOx (x = 0) and SiOx (0 < x < 2), and based on 100 parts by weight of the silicon-based active material, the SiOx (x = 0) may be included in an amount of 70 parts by weight or more.

[0048] In one embodiment of the present application, the silicon-based active material includes SiOx (x = 0), and based on 100 parts by weight of the silicon-based active material, the SiOx (x = 0) may be included in an amount of 70 parts by weight or more.

[0049] In another embodiment, based on 100 parts by weight of the silicon-based active material, the SiOx (x = 0) may be included in an amount of 70 parts by weight or more, preferably 80 parts by weight or more, more preferably 90 parts by weight or more, and may be included in an amount of 100 parts by weight or less, preferably 99 parts by weight or less, more preferably 95 parts by weight or less.

[0050] In one embodiment of the present application, as the silicon-based active material, those containing particularly pure silicon (Si) particles may be used. Using pure silicon (Si) particles as the silicon-based active material means that, based on 100 parts by weight of the total silicon-based active material as described above, pure Si particles (SiOx (x = 0)) not bonded to other particles or elements are included within the above range.

[0051] In one embodiment of the present application, the silicon-based active material may be composed of silicon-based particles having 100 parts by weight of SiOx (x = 0) based on 100 parts by weight of the silicon-based active material.

[0052] In one embodiment of the present application, the silicon-based active material may contain metal impurities. In this case, the impurities are metals that can generally be contained in the silicon-based active material. Specifically, based on 100 parts by weight of the silicon-based active material, it may contain 0.1 part by weight or less.

[0053] In the case of silicon-based active materials, compared with the conventionally used graphite-based active materials, the capacity is significantly higher, and attempts to apply them are increasing. However, the volume expansion rate is high during the charge and discharge process, and it has remained at the level of mixing a small amount with graphite-based active materials and using them.

[0054] Therefore, in the case of the present invention, in order to improve the capacity performance, while using only the silicon-based active material as the negative electrode active material, in order to solve the above problems, rather than adjusting the composition of the conductive material and the binder, the existing problems have been solved by adjusting the crystal grain size or surface area of the silicon-based active material itself.

[0055] In one embodiment of the present application, the crystal grain size of the silicon-based active material may be 200 nm or less.

[0056] In yet another embodiment, the size of the crystal grains of the silicon-based active material is 200 nm or less, preferably 130 nm or less, more preferably 110 nm or less, even more preferably 100 nm or less, specifically 95 nm or less, and more specifically 91 nm or less. The size of the crystal grains of the silicon-based active material may be in the range of 10 nm or more, preferably 15 nm or more.

[0057] The silicon-based active material has the above-mentioned crystal grain size, and the crystal grain size of the silicon-based active material can be adjusted by changing the process conditions in the manufacturing process. At this time, by satisfying the above range so that grain boundaries are widely distributed, when lithium ions are inserted, they will enter uniformly, and the stress generated when inserting lithium ions into silicon particles can be reduced, thereby relaxing the cracking of the particles. As a result, it has the characteristic of being able to improve the life stability of the negative electrode. When the crystal grain size exceeds the above range, the intra-particle crystal grain system will be narrowly distributed. In this case, lithium ions in the particles will be inserted unevenly, the stress due to ion insertion will be large, and the particle cracking phenomenon will occur.

[0058] In one embodiment of the present application, the silicon-based active material includes a crystal structure having a crystal grain distribution of 1 nm or more and 200 nm or less, and provides a negative electrode active material in which the area ratio of the crystal structure is 5% or less based on the total area of the silicon-based active material.

[0059] In yet another embodiment, based on the total area of the silicon-based active material, the area ratio of the crystal structure is 5% or less, 3% or less, and may be 0.1% or more.

[0060] That is, the silicon-based active material according to the present application has a crystal grain size of 200 nm or less, a small size of one crystal structure is formed, and the above-mentioned area ratio can be satisfied. Thereby, the distribution of grain boundaries can be widened, and the above-mentioned effects can be achieved.

[0061] In one embodiment of the present application, a negative electrode active material is provided in which the number of crystal structures contained in the silicon-based active material is 20 or more.

[0062] In another embodiment, the number of crystal structures contained in the silicon-based active material may be 20 or more, 30 or more, 35 or more, and may satisfy the range of 60 or less, 50 or less.

[0063] That is, as described above, when the silicon-based active material satisfies the grain size within the above range and the number of crystal structures within the above range, the strength of the silicon-based active material itself has an appropriate range, and when contained in the electrode, it can impart flexibility and can efficiently suppress volume expansion.

[0064] In the present application, a crystal grain means a crystal particle that is an aggregate of irregularly shaped microscopic sizes in a metal or material, and the crystal grain size can mean the diameter of the observed crystal grain particles. That is, in the present application, the crystal grain size means the size of a domain that shares the same crystal direction within the particle, and has a different concept from the particle size or particle diameter that represents the size of the substance.

[0065] In one embodiment of the present application, the crystal grain size can be calculated as an FWHM (Full Width at Half Maximum) value through XRD analysis. Specifically, the method for calculating the crystal grain size can be understood from FIG. 3. In FIG. 3, the remaining values except for L are measured by XRD analysis of the silicon-based active material, and since the FWHM and the crystal grain size are inversely proportional through the Debye-Scherrer formula, the crystal grain size can be measured. At this time, the Debye-Scherrer formula is as shown in the following formula 1-1.

[0066] [Formula 1-1] FWHM = Kλ / LCosθ In the above formula 1-1, L represents the grain size, K is a constant, θ is the Bragg angle, and λ represents the wavelength of X-ray.

[0067] Note that the shape of the grains is diverse and can be measured three-dimensionally. Generally, the size of the grains can be measured by the commonly used circle method or diameter measurement method, but it is not limited to this.

[0068] In the diameter measurement method, 5 to 10 equilibrium lines with a length of L mm can be drawn on the micrograph of the target particles, and the number of grains z on the line can be counted and averaged for measurement. At this time, only those that are completely included are counted, and those that are only touching are excluded. If the number of lines is P and the magnification is V, the average particle diameter can be calculated by the following formula 1-2.

[0069] [Formula 1-2] Dm=(L*P*10 3 ) / (zV)(um)

[0070] Also, in the circle method, after drawing a circle with a determined diameter on the micrograph of the target particles, the average area of the grains can be obtained by the method of obtaining the average area of the grains based on the number of grains inside the circle and the number of grains on the boundary line, and can be calculated by the following formula 1-3.

[0071] [Formula 1-3] Fm=(Fk*10 6 ) / ((0.67n+z)V 2 )(um 2 )

[0072] In the above formula 1-3, Fm represents the average particle area, Fk represents the measured area on the photo, z represents the number of particles inside the circle, n represents the number of particles on the arc, and V represents the magnification of the microscope, respectively.

[0073] In one embodiment of the present application, the negative electrode active material may include a silicon-based active material with a surface area of 0.25 m 2 / g or more.

[0074] In another embodiment, the silicon-based active material has a specific surface area of 0.25 m 2 / g or more, preferably 0.28 m 2 / g or more, more preferably 0.30 m 2 / g or more, specifically 0.31 m 2 / g or more, more specifically 0.32 m 2 / g or more. The silicon-based active material may have a specific surface area of 3 m 2 / g or less, preferably 2.5 m 2 / g or less, more preferably 2.2 m 2 / g or less. The specific surface area can be measured according to DIN 66131 (using nitrogen).

[0075] The silicon-based active material has the above-mentioned specific surface area, and the size of the specific surface area of the silicon-based active material can be adjusted by changing the process conditions in the manufacturing process and the growth conditions of the silicon-based active material described below. That is, when manufacturing the negative electrode active material by the manufacturing method according to the present application, a rough surface has a larger surface area than particles having the same particle size. At this time, by satisfying the above range and having a high binding force with the binder, it has the characteristic of being able to relieve cracks in the electrode due to repeated charge and discharge cycles.

[0076] Also, when lithium ions are inserted, they will enter uniformly, and the stress applied when inserting lithium ions into silicon particles can be reduced, thereby relieving the cracking of the particles. As a result, it has the characteristic of being able to improve the life stability of the negative electrode. When the specific surface area is less than the above range, even when having the same particle size, the surface is smoothly formed, the binding force with the binder decreases, and electrode cracks occur. In this case, lithium ions in the particles are inserted non-uniformly, the stress due to ion insertion is large, and the particle cracking phenomenon occurs.

[0077] In one embodiment of the present application, the silicon-based active material provides a negative electrode active material that satisfies the range of the following formula 2-1. [Formula 2-1] X1 / Y1 ≤ 0.960 In Formula 2-1, X1 is the actual area of the silicon-based active material, Y1 means the area of spherical particles having the same perimeter as the silicon-based active material.

[0078] The measurement of Formula 2-1 can be performed using a particle analyzer. Specifically, after the silicon-based active material according to the present application is scattered on a glass plate through air injection, the scattered silicon-based active material particles are photographed with a shadow image to measure the shapes of 10,000 silicon-based active material particles in the photograph. At this time, Formula 2-1 is a value representing the average for 10,000 particles. From the above image, Formula 2-1 according to the present application can be measured, and Formula 2-1 can be represented by the sphericity of the silicon-based active material. The sphericity may be represented by the formula [4π * actual area of the silicon-based active material / (boundary) 2 may be represented.

[0079] In one embodiment of the present application, the sphericity of the silicon-based active material may be, for example, 0.960 or less, for example, 0.957 or less. The sphericity of the silicon-based active material may be 0.8 or more, for example, 0.9 or more, specifically 0.93 or more, more specifically 0.94 or more, for example, 0.941 or more.

[0080] In one embodiment of the present application, the silicon-based active material provides a negative electrode active material that satisfies the following range of Formula 2-2.

[0081] [Formula 2-2] X2 / Y2 ≤ 0.995 In Formula 2-2, Y2 is the actual perimeter of the silicon-based active material, X2 is the perimeter of the circumscribed figure of the silicon-based active material.

[0082] The measurement of Formula 2-2 can be performed using a particle analyzer. Specifically, after scattering the silicon-based active material according to the present application onto a glass plate through air injection, the scattered silicon-based active material particles are photographed to obtain a shadow image, and the shapes of 10,000 silicon-based active material particles in the photograph can be measured. At this time, Formula 2-2 represents an average value for 10,000 particles. From the above image, Formula 2-2 according to the present application can be measured, and Formula 2-2 can represent the convexity of the silicon-based active material.

[0083] In one embodiment of the present application, X2 / Y2 ≤ 0.996, preferably X2 / Y2 ≤ 0.995 can be satisfied, and 0.8 ≤ X2 / Y2, preferably 0.9 ≤ X2 / Y2, more preferably 0.95 ≤ X2 / Y2, specifically 0.98 ≤ X2 / Y2 can be satisfied.

[0084] The smaller the value of Formula 2-1 or Formula 2-2, the greater the roughness of the silicon-based active material can be meant. By using the silicon-based active material having the above range, the binding force with the binder is increased, and the electrodes can have the characteristic of alleviating cracks due to repeated charge and discharge cycles.

[0085] In one embodiment of the present application, the silicon-based active material may include silicon-based particles having a particle size distribution of 0.01 μm or more and 30 μm or less.

[0086] The silicon-based active material including silicon-based particles having a particle size distribution of 0.01 μm or more and 30 μm or less means that a large number of individual silicon-based particles having a particle size within the above range are included, and the number of silicon-based particles included is not limited.

[0087] The particle size of the silicon-based particles can be represented by its diameter in the case of a spherical shape. However, in the case of other non-spherical shapes, the particle size can be measured in comparison with the case of a spherical shape, and the particle size of individual silicon-based particles can generally be measured by a method used in the art.

[0088] On the one hand, the average particle size (D50 particle size) of the silicon-based active material of the present invention is 3 μm to 10 μm, specifically 4 μm to 8 μm, and more specifically may be 6 μm to 7 μm. When the average particle size is included in the above range, the specific surface area of the particles is included in an appropriate range, and the viscosity of the negative electrode slurry is formed in an appropriate range. Thereby, the dispersion of the particles constituting the negative electrode slurry becomes smooth. Further, since the size of the silicon-based active material has a value equal to or greater than the lower limit value of the above range, the contact area between the silicon particles and the conductive material is excellent due to the composite composed of the conductive material and the binder in the negative electrode slurry, and the conductive network is likely to continue, increasing the capacity retention rate. On the other hand, when the average particle size satisfies the above range, silicon particles that are too large are excluded, and the surface of the negative electrode is formed smoothly, thereby preventing the current density non-uniformity phenomenon during charge and discharge.

[0089] In one embodiment of the present application, the silicon-based active material has a generally characteristic BET specific surface area. The BET specific surface area of the silicon-based electrode active material is preferably 0.01 m 2 / g to 150.0 m 2 / g, more preferably 0.1 m 2 / g to 100.0 m 2 / g, particularly preferably 0.2 m 2 / g to 80.0 m 2 / g, most preferably 0.2 m 2 / g to 18.0 m 2 / g. The BET specific surface area is measured in accordance with DIN 66131 (using nitrogen).

[0090] In one embodiment of the present application, the silicon-based active material can exist, for example, in a crystalline or amorphous form and is preferably not porous. The silicon particles are preferably spherical or flaky particles. As an alternative, although less preferred, the silicon particles may also have a fibrous structure or exist in the form of a silicon-containing film or coating.

[0091] In one embodiment of the present application, the silicon-based active material may have a non-spherical form, and its sphericity may be, for example, 0.9 or less, for example, 0.7 to 0.9, for example, 0.8 to 0.9, for example, 0.85 to 0.9.

[0092] In the present application, the sphericity is determined by the following formula (3-1), where A is the area and P is the boundary line. [Formula 3-1] 4πA / P 2

[0093] In one embodiment of the present application, a negative electrode composition including the negative electrode active material; a negative electrode conductive material; and a negative electrode binder is provided.

[0094] In one embodiment of the present application, the negative electrode active material provides a negative electrode composition that is 60 parts by weight or more based on 100 parts by weight of the negative electrode composition.

[0095] In still another embodiment, the negative electrode active material may include 60 parts by weight or more, preferably 65 parts by weight or more, more preferably 70 parts by weight or more, and may be 95 parts by weight or less, preferably 90 parts by weight or less, more preferably 85 parts by weight or less based on 100 parts by weight of the negative electrode composition.

[0096] The negative electrode composition according to the present application uses a negative electrode active material having a specific crystal grain size that can suppress the volume expansion rate during the charge and discharge process even when using a negative electrode active material with extremely high capacity within the above range, and does not deteriorate the performance of the negative electrode even when including the above range, and has excellent output characteristics during charging and discharging.

[0097] Conventionally, it has been common to use only graphite-based compounds as the negative electrode active material. However, in recent years, as the demand for high-capacity batteries has increased, attempts have been increasing to mix and use silicon-based active materials to increase the capacity. However, in the case of silicon-based active materials, even if the characteristics of the silicon-based active material itself are adjusted as described above, there may be a problem that the volume rapidly expands during the charge / discharge process, damaging the conductive path formed in the negative electrode active material layer.

[0098] Therefore, in one embodiment of the present application, the negative electrode conductive material may include at least one selected from the group consisting of a dot-shaped conductive material, a planar conductive material, and a linear conductive material.

[0099] In one embodiment of the present application, the dot-shaped conductive material can be used to improve the conductivity of the negative electrode, and means a dot-shaped or spherical conductive material having conductivity without inducing a chemical change. Specifically, the dot-shaped conductive material may be at least one selected from the group consisting of natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black, conductive fiber, fluorocarbon, aluminum powder, nickel powder, zinc oxide, potassium titanate, titanium oxide, and polyphenylene derivative, and preferably may include carbon black in terms of realizing high conductivity and excellent dispersibility.

[0100] In one embodiment of the present application, the dot-shaped conductive material has a BET specific surface area of 40 m 2 / g or more and 70 m 2 / g or less, preferably 45 m 2 / g or more and 65 m 2 / g or less, more preferably 50 m 2 / g or more and 60 m 2 / g or less.

[0101] In one embodiment of the present application, the dot-shaped conductive material may satisfy a functional group content (Volatile matter) of 0.01% or more and 1% or less, preferably 0.01% or more and 0.3% or less, more preferably 0.01% or more and 0.1% or less.

[0102] In particular, when the functional group content of the dot-shaped conductive material satisfies the above range, functional groups exist on the surface of the dot-shaped conductive material, and when water is used as a solvent, the dot-shaped conductive material can be smoothly dispersed in the solvent. In particular, in the present invention, by using a specific silicon-based active material, the functional group content of the dot-shaped conductive material can be lowered, thereby having an excellent effect on improving dispersibility.

[0103] In one embodiment of the present application, it is characterized by including a dot-shaped conductive material having a functional group content within the above range together with a silicon-based active material, and the adjustment of the functional group content can be adjusted according to the degree of heat treatment of the dot-shaped conductive material.

[0104] In one embodiment of the present application, the particle size of the dot-shaped conductive material is 10 nm to 100 nm, preferably 20 nm to 90 nm, and more preferably 20 nm to 60 nm. In one embodiment of the present application, the conductive material may include a planar conductive material.

[0105] The planar conductive material can play a role in increasing the surface contact between silicon particles in the negative electrode to improve conductivity, and at the same time suppressing the interruption of the conductive path due to volume expansion. The planar conductive material can be expressed as a plate-shaped conductive material or a bulk-type conductive material.

[0106] In one embodiment of the present application, the planar conductive material can include at least one selected from the group consisting of plate-shaped graphite, graphene, graphene oxide, and graphite flakes, and preferably may be plate-shaped graphite.

[0107] In one embodiment of the present application, the average particle size (D50) of the planar conductive material is 2 μm to 7 μm, specifically 3 μm to 6 μm, and more specifically may be 3.5 μm to 5 μm. When the above range is satisfied, due to the sufficient particle size, dispersion is easy without causing an excessive increase in the viscosity of the negative electrode slurry. Therefore, when dispersing using the same equipment and time, the dispersion effect is excellent.

[0108] In one embodiment of the present application, the planar conductive material provides a negative electrode composition in which D10 is 0.5 μm or more and 2.0 μm or less, D50 is 2.5 μm or more and 3.5 μm or less, and D90 is 6.5 μm or more and 15.0 μm or less.

[0109] In one embodiment of the present application, as the planar conductive material, a high specific surface area planar conductive material having a high BET specific surface area; or a low specific surface area planar conductive material may be used.

[0110] In one embodiment of the present application, as the planar conductive material, a high specific surface area planar conductive material; or a low specific surface area planar conductive material can be used without limitation. However, particularly for the planar conductive material according to the present application, the electrode performance may be affected to some extent by the dispersion, and in some cases, it is particularly preferable to use a low specific surface area planar conductive material that does not cause problems in dispersion.

[0111] In one embodiment of the present application, the planar conductive material may have a BET specific surface area of 1 m 2 / g or more.

[0112] In another embodiment, the planar conductive material has a BET specific surface area of 1 m 2 / g or more and 500 m 2 / g or less, preferably 5 m 2 / g or more and 300 m 2 / g or less, more preferably 5 m 2 / g or more and 250 m 2 / g or less. As the planar conductive material according to the present application, a high specific surface area planar conductive material; or a low specific surface area planar conductive material can be used.

[0113] In another embodiment, the planar conductive material is a high specific surface area planar conductive material and may satisfy the range of having a BET specific surface area of 50 m 2 / g or more and 500 m 2 / g or less, preferably 80 m 2 / g or more and 300 m 2 / g or less, more preferably 100 m 2 / g or more and 300 m 2 / g or less.

[0114] In still another embodiment, the planar conductive material is a low specific surface area planar conductive material, and the BET specific surface area is 1 m 2 / g or more and 40 m 2 / g or less, preferably 5 m 2 / g or more and 30 m 2 / g or less, more preferably 5 m 2 / g or more and 25 m 2 / g or less.

[0115] As other conductive materials, there may be linear conductive materials such as carbon nanotubes. The carbon nanotubes may be bundle-type carbon nanotubes. The bundle-type carbon nanotubes may include a plurality of carbon nanotube unit bodies. Specifically, here, the "bundle type" means that, unless otherwise specified, a plurality of carbon nanotube unit bodies are arranged side by side with substantially the same orientation of the longitudinal axis of the carbon nanotube unit body, or are intertwined, and refers to a secondary shape in the form of a bundle or a rope. The carbon nanotube unit body has a graphite sheet having a nanosize diameter cylinder shape and an sp2 bond structure. At this time, the characteristics of a conductor or a semiconductor can be exhibited depending on the angle and structure by which the graphite sheet is wound. The bundle-type carbon nanotubes can be uniformly dispersed during the production of the negative electrode as compared with entangled-type carbon nanotubes, can smoothly form a conductive network in the negative electrode, and can improve the conductivity of the negative electrode.

[0116] In one embodiment of the present application, the negative electrode conductive material provides a negative electrode composition that is 10 parts by weight or more and 40 parts by weight or less based on 100 parts by weight of the negative electrode composition.

[0117] In another embodiment, the negative electrode conductive material may contain 0.1 parts by weight or more and 40 parts by weight or less, preferably 0.2 parts by weight or more and 30 parts by weight or less, more preferably 0.4 parts by weight or more and 25 parts by weight or less, and most preferably 0.4 parts by weight or more and 10 parts by weight or less, based on 100 parts by weight of the negative electrode composition.

[0118] In one embodiment of the present application, the negative electrode conductive material provides a negative electrode composition containing a planar conductive material and a linear conductive material.

[0119] In one embodiment of the present application, the negative electrode conductive material provides a negative electrode composition containing 80 parts by weight or more and 99.9 parts by weight or less of the planar conductive material; and 0.1 parts by weight or more and 20 parts by weight or less of the linear conductive material, based on 100 parts by weight of the negative electrode conductive material.

[0120] In yet another embodiment, the negative electrode conductive material may contain 80 parts by weight or more and 99.9 parts by weight or less, preferably 85 parts by weight or more to 99.9 parts by weight or less, and more preferably 95 parts by weight or more to 98 parts by weight or less of the planar conductive material, based on 100 parts by weight of the negative electrode conductive material.

[0121] In yet another embodiment, the negative electrode conductive material may contain 0.1 parts by weight or more and 20 parts by weight or less, preferably 0.1 parts by weight or more and 15 parts by weight or less, and more preferably 0.2 parts by weight or more and 5 parts by weight or less of the linear conductive material, based on 100 parts by weight of the negative electrode conductive material.

[0122] In one embodiment of the present application, when the negative electrode conductive material contains a planar conductive material and a linear conductive material and satisfies the respective compositions and ratios, it does not significantly affect the life characteristics of existing lithium secondary batteries. In particular, when it contains a planar conductive material and a linear conductive material, there are many points where charging and discharging are possible, it has excellent output characteristics at a high C-rate, and the amount of gas generated at high temperatures is reduced.

[0123] In one embodiment of the present application, the negative electrode conductive material may consist of a linear conductive material. In particular, when the linear conductive material is used alone, the tortuosity of the silicon-based negative electrode, which is a problem of the silicon-based negative electrode, can be simplified, the electrode structure can be improved, and thus the movement resistance of lithium ions in the electrode can be reduced.

[0124] In one embodiment of the present application, when the negative electrode conductive material contains a linear conductive material alone, the negative electrode conductive material may contain 0.1 parts by weight or more and 5 parts by weight or less, preferably 0.2 parts by weight or more and 3 parts by weight or less, and more preferably 0.4 parts by weight or more and 1 part by weight or less based on 100 parts by weight of the negative electrode composition.

[0125] The negative electrode conductive material according to the present application has a completely different configuration from the positive electrode conductive material applied to the positive electrode. That is, in the case of the negative electrode conductive material according to the present application, it serves to capture the contacts between silicon-based active materials with a very large volume expansion of the electrode during charging and discharging, and the positive electrode conductive material serves to impart partial conductivity while serving as a buffer with a buffering role when rolled, and the configuration and role of the negative electrode conductive material of the present invention are completely different.

[0126] Further, the negative electrode conductive material according to the present application is applied to a silicon-based active material and has a completely different configuration from the conductive material applied to a graphite-based active material. That is, the conductive material used for an electrode having a graphite-based active material has characteristics of improving output characteristics and imparting partial conductivity because it simply has particles smaller than the active material, and the configuration and role of the negative electrode conductive material applied together with the silicon-based active material as in the present invention are completely different.

[0127] In one embodiment of the present application, the planar conductive material used as the above-described negative electrode conductive material has a different structure and role from the carbon-based active material generally used as the negative electrode active material. Specifically, the carbon-based active material used as the negative electrode active material may be artificial graphite or natural graphite, and means a material processed into a spherical or dot-like form to facilitate the storage and release of lithium ions.

[0128] On the one hand, the sheet-like conductive material used as the negative electrode conductive material is a substance having a sheet or plate-like form, and can be expressed as plate-like graphite. That is, it is a substance contained to maintain a conductive path within the negative electrode active material layer, and does not play a role in the storage and release of lithium, but means a substance for ensuring a sheet-like conductive path inside the negative electrode active material layer.

[0129] That is, in the present application, the fact that plate-like graphite was used as the conductive material means that it was processed into a sheet-like or plate-like form and used as a substance for ensuring a conductive path rather than for the role of storing or releasing lithium. At this time, the negative electrode active material contained together has high capacity characteristics for the storage and release of lithium and plays a role of being able to store and release all lithium ions transmitted from the positive electrode.

[0130] On the other hand, in the present application, the fact that a carbon-based active material was used as the active material means that it was processed into a dot-like or spherical shape and used as a substance for playing a role in storing or releasing lithium.

[0131] That is, in one embodiment of the present application, artificial graphite or natural graphite, which is a carbon-based active material, is dot-like and has a BET specific surface area of 0.1 m 2 / g or more and 4.5 m 2 / g or less. Also, the plate-like graphite, which is a sheet-like conductive material, may have a BET specific surface area of 5 m 2 / g or more.

[0132] In one embodiment of the present application, the negative electrode 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, tetrafluoroethylene, polyethylene, polypropylene, polyacrylic acid, ethylene-propylene-diene monomer (EPDM), sulfonated EPDM, styrene-butadiene rubber (SBR), fluororubber, poly acrylic acid, and substances in which their hydrogens are substituted with Li, Na, or Ca, etc., and may also include various copolymers thereof.

[0133] The negative electrode binder according to one embodiment of the present application plays a role in suppressing the active material and the conductive material in order to prevent the twisting and structural deformation of the negative electrode structure during the volume expansion and relaxation of the silicon-based active material. As long as the role is satisfied, any common binder can be applied. Specifically, an aqueous binder can be used, and more specifically, a PAM-based binder can be used.

[0134] In one embodiment of the present application, the negative electrode binder is 30 parts by weight or less, preferably 25 parts by weight or less, more preferably 20 parts by weight or less, based on 100 parts by weight of the negative electrode composition, and may be 5 parts by weight or more, 10 parts by weight or more.

[0135] One embodiment of the present application includes: chemically reacting a silane gas to deposit a silicon-based active material on a substrate; obtaining the silicon-based active material deposited on the substrate; and forming silicon oxide on the surface of the silicon-based active material. A method for manufacturing a negative electrode active material, wherein the step of forming the silicon oxide includes oxidizing the silicon-based active material through heat treatment or chemical treatment; or coating the surface of the silicon-based active material with silicon oxide. A method for manufacturing a negative electrode active material according to the present application is provided, which includes a silicon oxide coating layer surrounding at least a part of the outer surface of the silicon-based active material.

[0136] At this time, as a method for forming the silicon oxide coating layer, it may include oxidizing the silicon-based active material by heat treatment or chemical treatment; or coating the surface of the silicon-based active material with silicon oxide.

[0137] The step of oxidizing the silicon-based active material by heat treatment or chemical treatment corresponds to a method of oxidizing the surface of existing silicon-based active material particles. Specifically, oxidation by heat treatment can form a silicon oxide coating layer through heat treatment at 40°C to 1000°C for 1 minute to 90 minutes while flowing oxygen gas. Furthermore, oxidation by heat treatment can form a silicon oxide coating layer not only by the above method but also by heating with an inert gas and an oxygen mixed gas at a temperature of 300°C to 1000°C.

[0138] Also, oxidation by chemical treatment can form a silicon oxide coating layer by treating the silicon-based active material with 30 vol% H2O2 hydrogen peroxide + 70 vol% H2SO4 sulfuric acid (piranha solution) or concentrated nitric acid.

[0139] The step of coating silicon oxide on the surface of the silicon-based active material does not originate from the existing silicon-based active material. By coating a new silicon oxide coating layer, in a state where tetraethyl orthosilicate and the silicon-based active material are mixed, a silicon oxide coating layer can be formed on the surface through the hydration process of tetraethyl orthosilicate via a basic substance.

[0140] By the above-described method, the negative electrode active material according to the present application has the characteristic that it can produce an electrode with less gas generation during slurry formation and excellent life characteristics.

[0141] In one embodiment of the present application, a method for manufacturing a negative electrode active material is provided, wherein the step of heat-treating the silicon-based active material is to perform heat treatment under conditions of 40°C or higher and 150°C or lower.

[0142] A silicon oxide coating layer with a thin thickness can be intentionally formed while satisfying the above temperature conditions, and the above problems are solved through the silicon oxide coating layer formed under such conditions.

[0143] According to an example, the silane gas may contain at least one gas selected from monosilane, dichlorosilane, and trichlorosilane, and specifically may be trichlorosilane gas.

[0144] In the present application, a method for manufacturing a negative electrode active material is provided, wherein the step of chemically reacting the silane gas to deposit a silicon-based active material on a substrate is to form under conditions of a high temperature of 100°C or higher.

[0145] In one embodiment of the present application, the step of chemically reacting the silane gas to deposit a silicon-based active material on a substrate may be performed under a pressure condition of 10 Pa to 150 Pa. Due to such a low pressure, the silicon growth rate decreases, and thereby, small crystal grains can be formed. The step may be performed under a temperature condition of 100 °C or higher, specifically 500 °C or higher, preferably 800 °C or higher, more preferably 800 °C to 1300 °C, 800 °C to 1100 °C. This is a lower temperature than the conventional gas atomizing method that heats to 1600 °C or higher to melt Si.

[0146] In one embodiment of the present application, the silicon-based active material may further include a step of growing through crystal nucleation. The step of growing the silicon-based active material through crystal nucleation may be performed under a temperature condition of 800 °C or higher, preferably 800 °C to 1300 °C. This is a lower temperature than the conventional gas atomizing method that heats to 1600 °C or higher to melt Si. Also, the step of growing the silicon-based active material by crystal nucleation can be performed under a pressure of 100 Pa to 150 Pa. Due to such a low pressure, the silicon growth rate decreases, and thereby, small crystal grains can be formed and a specific surface area can be achieved.

[0147] Conventionally, a silicon mass was produced by pulverizing it through physical force. When manufacturing in this way, the size of the crystal grains generally exceeds the range of 200 nm, the surface is smooth, and the surface area has a value of less than 0.25 m 2 / g. When simply manufacturing a silicon-based active material by a conventional method, there is a drawback that the size of the surface area cannot be controlled and it is difficult to ensure the life stability of the negative electrode.

[0148] However, in the method for manufacturing the negative electrode active material according to the present application, after the silicon mass is silane gasified through a chemical reaction under specific process conditions as described above, silicon particles can be formed including the step of growing the silicon-based active material through crystal nucleation. As a result, a silicon-based active material satisfying the surface area size and crystal grain size according to the present application could be obtained.

[0149] In one embodiment of the present application, there is provided a negative electrode for a lithium secondary battery, including: a negative electrode current collector layer; and a negative electrode active material layer formed on one or both surfaces of the negative electrode current collector layer and including the negative electrode composition according to the present application or a cured product thereof.

[0150] FIG. 1 is a diagram showing a laminated structure of a negative electrode for a lithium secondary battery according to one embodiment of the present application. Specifically, a negative electrode 100 for a lithium secondary battery including a negative electrode active material layer 20 on one surface of a negative electrode current collector layer 10 can be confirmed. FIG. 1 shows that the negative electrode active material layer is formed on one surface, but it may be included on both surfaces of the negative electrode current collector layer.

[0151] In one embodiment of the present application, the negative electrode for the lithium secondary battery may be formed by applying and drying a negative electrode slurry including the negative electrode composition on one or both surfaces of the negative electrode current collector layer.

[0152] At this time, the negative electrode slurry may include the aforementioned negative electrode composition; and a slurry solvent.

[0153] In one embodiment of the present application, the solid content of the negative electrode slurry may satisfy 5% or more and 40% or less.

[0154] In another embodiment, the solid content of the negative electrode slurry may satisfy a range of 5% or more and 40% or less, preferably 7% or more and 35% or less, and more preferably 10% or more and 30% or less.

[0155] The solid content of the negative electrode slurry can mean the content of the negative electrode composition contained in the negative electrode slurry, and can mean the content of the negative electrode composition based on 100 parts by weight of the negative electrode slurry.

[0156] When the solid content of the negative electrode slurry satisfies the above range, the viscosity during the formation of the negative electrode active material layer is appropriate, and it has the characteristic that the agglomeration phenomenon of the particles of the negative electrode composition can be minimized and the negative electrode active material layer can be efficiently formed.

[0157] In one embodiment of the present application, the slurry solvent can be used without limitation as long as it can dissolve the negative electrode composition. Specifically, water or NMP can be used.

[0158] In one embodiment of the present application, the negative electrode current collector layer generally has a thickness of 1 μm to 100 μm. Such a negative electrode current collector layer is not particularly limited as long as it has high conductivity without inducing chemical changes in the battery. For example, copper, stainless steel, aluminum, nickel, titanium, fired carbon, those surface-treated with carbon, nickel, titanium, silver, etc. on the surface of copper or stainless steel, aluminum-cadmium alloy, etc. can be used. Also, fine irregularities can be formed on the surface to strengthen the binding force of the negative electrode active material, and it can be used in various forms such as films, sheets, foils, nets, porous bodies, foams, non-woven fabrics, etc.

[0159] In one embodiment of the present application, a negative electrode for a lithium secondary battery is provided, wherein the thickness of the negative electrode current collector layer is 1 μm or more and 100 μm or less, and the thickness of the negative electrode active material layer is 20 μm or more and 500 μm or less.

[0160] However, the thickness can be variously deformed according to the type and use of the negative electrode used, and is not limited thereto.

[0161] In one embodiment of the present application, the porosity of the negative electrode active material layer may satisfy the range of 10% or more and 60% or less.

[0162] In another embodiment, the porosity of the negative electrode active material layer may satisfy the range of 10% or more and 60% or less, preferably 20% or more and 50% or less, and more preferably 30% or more and 45% or less.

[0163] The porosity varies according to the composition and content of the silicon-based active material, conductive material, and binder contained in the negative electrode active material layer. In particular, by including the silicon-based active material and conductive material according to the present application in specific compositions and content portions, the above range is satisfied. Thereby, the electric conductivity and resistance of the electrode have an appropriate range.

[0164] In one embodiment of the present application, a lithium secondary battery is provided that includes a positive electrode; a negative electrode for a lithium secondary battery according to the present application; a separator provided between the positive electrode and the negative electrode; and an electrolyte.

[0165] FIG. 2 is a diagram showing the laminated structure of a lithium secondary battery according to an embodiment of the present application. Specifically, a negative electrode 100 for a lithium secondary battery including a negative electrode active material layer 20 can be confirmed on one surface of a negative electrode current collector layer 10, and a positive electrode 200 for a lithium secondary battery including a positive electrode active material layer 40 can be confirmed on one surface of a positive electrode current collector layer 50. It shows that the negative electrode 100 for a lithium secondary battery and the positive electrode 200 for a lithium secondary battery are laminated with a separator 30 interposed therebetween.

[0166] The secondary battery according to an embodiment of the present specification may particularly include the negative electrode for a lithium secondary battery 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, and the negative electrode is the same as the negative electrode described above. Since the negative electrode has been described above, a specific description thereof will be omitted.

[0167] 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.

[0168] In the positive electrode, the positive electrode current collector is not particularly limited as long as it has conductivity without inducing chemical changes in the battery. For example, stainless steel, aluminum, nickel, titanium, fired carbon, or those obtained by surface treatment with carbon, nickel, titanium, silver, etc. on the surface of aluminum or stainless steel can be used. Further, the positive electrode current collector can usually have a thickness of 3 μm to 500 μm, and fine irregularities can be formed on the surface of the current collector to enhance the adhesive force of the positive electrode active material. For example, it may be used in various forms such as films, sheets, foils, nets, porous bodies, foams, non-woven fabrics, etc.

[0169] The positive electrode active material may be a commonly used positive electrode active material. Specifically, the positive electrode active material includes layered compounds such as lithium cobalt oxide (LiCoO2) and lithium nickel oxide (LiNiO2), and compounds substituted with one or more transition metals; lithium iron oxides such as LiFe3O4; the chemical formula Li 1+c1 Mn 2-c1 O4 (0 ≦ c1 ≦ 0.33), lithium manganese oxides such as LiMnO3, LiMn2O3, LiMnO2; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, V2O5, Cu2V2O7; the chemical formula LiNi 1-c2 M c2 O2 (where M is at least one selected from the group consisting of Co, Mn, Al, Cu, Fe, Mg, B, and Ga, and satisfies 0.01 ≦ c2 ≦ 0.6) represented by Ni-site type lithium nickel oxide; the chemical formula LiMn 2-c3 M c3 O2 (where M is at least one selected from the group consisting of Co, Ni, Fe, Cr, Zn, and Ta, and satisfies 0.01 ≦ c3 ≦ 0.6) or Li2Mn3MO8 (where M is at least one selected from the group consisting of Fe, Co, Ni, Cu, and Zn).) represented by lithium manganese composite oxide; examples include LiMn2O4 in which a part of the Li in the chemical formula is substituted with alkaline earth metal ions, but it is not limited to these. The positive electrode may be metallic lithium (Li-metal).

[0170] In one embodiment of the present application, the positive electrode active material includes a lithium composite transition metal compound containing nickel (Ni), cobalt (Co), and manganese (Mn), the lithium composite transition metal compound includes single particles or secondary particles, and the average particle size (D50) of the single particles may be 1 μm or more.

[0171] For example, the average particle size (D50) of the single particles may be 1 μm or more and 12 μm or less, 1 μm or more and 8 μm or less, 1 μm or more and 6 μm or less, more than 1 μm and 12 μm or less, more than 1 μm and 8 μm or less, or more than 1 μm and 6 μm or less.

[0172] The single particles can have excellent particle strength even when formed with a small particle size having an average particle size (D50) of 1 μm or more and 12 μm or less. For example, the single particles can have a particle strength of 100 MPa to 300 MPa during rolling with a force of 650 kgf / cm 2 Thereby, even when the single particles are rolled with a strong force of 650 kgf / cm 2 the phenomenon of an increase in fine particles in the electrode due to particle cracking is alleviated, and thereby the life characteristics of the battery are improved.

[0173] The single particles can be manufactured by mixing a transition metal precursor and a lithium raw material and firing them. The secondary particles can be manufactured by a method different from that of the single particles, and their composition may be the same as or different from that of the single particles.

[0174] The method for forming the single particles is not particularly limited, but generally, it can be formed by increasing the firing temperature and overfiring, and can be manufactured by using additives such as a grain growth promoter useful for overfiring, or by changing the starting materials.

[0175] For example, the firing is performed at a temperature capable of forming single particles. To form these, firing must be performed at a temperature higher than that during the production of secondary particles. For example, when the precursor composition is the same, firing must be performed at a temperature about 30°C to 100°C higher than that during the production of secondary particles. The firing temperature for forming the single particles can vary depending on the metal composition within the precursor. For example, when forming a high-content nickel (High-Ni) NCM-based lithium composite transition metal oxide with a nickel (Ni) content of 80 mol% or more into single particles, the firing temperature may be about 700°C to 1000°C, preferably about 800°C to 950°C. When the firing temperature satisfies the above range, a cathode active material containing single particles with excellent electrochemical properties can be manufactured. When the firing temperature is less than 790°C, a cathode active material containing a secondary particle-like lithium composite transition metal compound can be manufactured. When it exceeds 950°C, firing occurs excessively, and a layered crystal structure may not be formed well, and the electrochemical properties may deteriorate.

[0176] In this specification, the single particle is a term used to distinguish from secondary particles formed by aggregation of dozens to hundreds of conventional primary particles, and is a concept including a single particle composed of one primary particle and a pseudo-single particle form which is an aggregate of 30 or fewer primary particles.

[0177] Specifically, the single particle in the present invention may be in the form of a single particle composed of one primary particle or a pseudo-single particle which is an aggregate of 30 or fewer primary particles, and the secondary particle may be in the form of an aggregate of hundreds of primary particles.

[0178] In one embodiment of the present application, the lithium composite transition metal compound which is the cathode active material further includes secondary particles, and the average particle diameter (D50) of the single particles is smaller than the average particle diameter (D50) of the secondary particles.

[0179] In the present invention, the single particle may be in the form of a single particle composed of one primary particle or a pseudo-single particle which is an aggregate of 30 or fewer primary particles, and the secondary particle may be in the form of an aggregate of hundreds of primary particles.

[0180] The aforementioned lithium composite transition metal compound may further contain secondary particles. The secondary particles refer to a form formed by aggregation of primary particles, and can be distinguished from the concept of single particles including a pseudo-single particle form which is one primary particle, one single particle, or an aggregate of 30 or fewer primary particles.

[0181] The particle size D50 of the secondary particles may be 1 μm to 20 μm, 2 μm to 17 μm, preferably 3 μm to 15 μm. The specific surface area (BET) of the secondary particles is 0.05 m 2 / g to 10 m 2 / g, preferably 0.1 m 2 / g to 1 m 2 / g, more preferably 0.3 m 2 / g to 0.8 m 2 / g.

[0182] In a further embodiment of the present application, the secondary particles are aggregates of primary particles, and the average particle size (D50) of the primary particles is 0.5 μm to 3 μm. Specifically, the secondary particles may be in a form where hundreds of primary particles are aggregated, and the average particle size (D50) of the primary particles may be 0.6 μm to 2.8 μm, 0.8 μm to 2.5 μm, or 0.8 μm to 1.5 μm.

[0183] When the average particle size (D50) of the primary particles satisfies the above range, a single-particle cathode active material with excellent electrochemical properties can be formed. If the average particle size (D50) of the primary particles is too small, the number of aggregated primary particles forming lithium nickel-based oxide particles increases, and the effect of suppressing particle cracking during rolling decreases. If the average particle size (D50) of the primary particles is too large, the lithium diffusion path inside the primary particles becomes long, the resistance increases, and the output characteristics may deteriorate.

[0184] According to a further embodiment of the present application, the average particle size (D50) of the single particles is characterized by being smaller than the average particle size (D50) of the secondary particles. Thereby, even if the single particles are formed with a small particle size, their particle strength can be excellent, whereby the phenomenon of an increase in fine particles in the electrode due to particle cracking is alleviated, and thereby the life characteristics of the battery can be improved.

[0185] In one embodiment of the present application, the average particle size (D50) of the single particles is 1 μm to 18 μm smaller than the average particle size (D50) of the secondary particles.

[0186] For example, the average particle size (D50) of the single particles can be 1 μm to 16 μm smaller than the average particle size (D50) of the secondary particles, 1.5 μm to 15 μm smaller, or 2 μm to 14 μm smaller.

[0187] When the average particle size (D50) of the single particles is smaller than the average particle size (D50) of the secondary particles, for example, when the above range is satisfied, the single particles can have excellent particle strength even if they are formed with a small particle size. Thereby, the phenomenon of an increase in fine particles in the electrode due to particle cracking is alleviated, and there are effects of improving the life characteristics and energy density of the battery.

[0188] According to a further embodiment of the present application, the single particles are contained in an amount of 15 parts by weight to 100 parts by weight based on 100 parts by weight of the positive electrode active material. The single particles may be contained in an amount of 20 parts by weight to 100 parts by weight, or 30 parts by weight to 100 parts by weight based on 100 parts by weight of the positive electrode active material.

[0189] For example, the single particles may be contained in an amount of 15 parts by weight or more, 20 parts by weight or more, 25 parts by weight or more, 30 parts by weight or more, 35 parts by weight or more, 40 parts by weight or more, or 45 parts by weight or more based on 100 parts by weight of the positive electrode active material. The single particles may be contained in an amount of 100 parts by weight or less based on 100 parts by weight of the positive electrode active material.

[0190] When including single particles within the above range, excellent battery characteristics can be exhibited in combination with the aforementioned negative electrode material. In particular, when the single particles are 15 parts by weight or more, the phenomenon of an increase in fine particles within the electrode due to particle cracking during the rolling process after electrode fabrication can be alleviated, and thereby the life characteristics of the battery can be improved.

[0191] In one embodiment of the present application, the lithium composite transition metal compound may further include secondary particles, and the secondary particles may be 85 parts by weight or less with respect to 100 parts by weight of the positive electrode active material. The secondary particles may be 80 parts by weight or less, 75 parts by weight or less, or 70 parts by weight or less with respect to 100 parts by weight of the positive electrode active material. The secondary particles may be 0 parts by weight or more with respect to 100 parts by weight of the positive electrode active material.

[0192] When the above range is satisfied, the aforementioned effects due to the presence of the single-particle positive electrode active material can be maximized. When including the secondary-particle positive electrode active material, its components may be the same as those exemplified by the aforementioned single-particle positive electrode active material, or may be different components, and can mean a form in which the single-particle form is aggregated.

[0193] In one embodiment of the present application, the positive electrode active material in 100 parts by weight of the positive electrode active material layer may be included in an amount of 80 parts by weight or more and 99.9 parts by weight or less, preferably 90 parts by weight or more and 99.9 parts by weight or less, more preferably 95 parts by weight or more and 99.9 parts by weight or less, and even more preferably 98 parts by weight or more and 99.9 parts by weight or less.

[0194] The positive electrode active material layer may include a positive electrode conductive material and a positive electrode binder together with the above-described positive electrode active material.

[0195] At this time, the positive electrode conductive material is used to impart conductivity to the electrode, and in the battery being configured, it can be used without particular limitation as long as it has electronic conductivity without causing a chemical change. Specific examples include graphite such as natural graphite and artificial graphite; carbon-based substances 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. Among these, one kind alone or a mixture of two or more kinds can be used.

[0196] Also, the positive electrode binder plays a role in improving the adhesion between the positive electrode active material particles and the adhesive force 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, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene - propylene - diene polymer (EPDM), sulfonated - EPDM, styrene - butadiene rubber (SBR), fluororubber, or various copolymers thereof. Among these, one kind alone or a mixture of two or more kinds may be used.

[0197] As the separation membrane, it separates the negative electrode and the positive electrode and provides a migration path for lithium ions. Generally, any material can be used without particular limitation as long as it is used as a separation membrane in a secondary battery. In particular, it is preferably low in resistance to ion migration of the electrolyte while having excellent electrolyte moisture retention ability. Specifically, a porous polymer film, for example, a porous polymer film made of polyolefin-based polymers such as ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer, and ethylene / methacrylate copolymer, or a laminate structure of two or more layers thereof may be used. Also, a normal porous non-woven fabric, for example, a non-woven fabric made of high-melting glass fibers, polyethylene terephthalate fibers, etc. may be used. Further, in order to ensure heat resistance or mechanical strength, a coated separation membrane containing a ceramic component or a polymer substance can also be used, and it may be selectively used in a single-layer or multi-layer structure.

[0198] 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. Specifically, the electrolyte may contain a non-aqueous organic solvent and a metal salt.

[0199] Examples of the non-aqueous organic solvent include 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 derivative, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivative, tetrahydrofuran derivative, ether, methyl propionate, ethyl propionate, etc. may be used.

[0200] In particular, ethylene carbonate and propylene carbonate, which are cyclic carbonates among the carbonate-based organic solvents, are organic solvents with high viscosity and high dielectric constant, which can dissociate lithium salts well, so they are preferably used. When such cyclic carbonates are mixed with chain carbonates with low viscosity and low dielectric constant such as dimethyl carbonate and diethyl carbonate in an appropriate ratio and used, an electrolyte having high electrical conductivity can be made and can be more preferably used.

[0201] As the metal salt, a lithium salt can be used. The lithium salt is a substance that is easily dissolved in the non-aqueous electrolyte. For example, as the anion of the lithium salt, F - , Cl - , I - , NO3 - , N(CN)2 - , BF4 - , ClO4 - , PF6 - , (CF3)2PF4 - , (CF3)3PF3 - , (CF3)4PF2 - , (CF3)5PF - , (CF3)6P - , CF3SO3 - , CF3CF2SO3- 、(CF3SO2)2N - 、(FSO2)2N - 、CF3CF2(CF3)2CO - 、(CF3SO2)2CH - 、(SF5)3C - 、(CF3SO2)3C - 、CF3(CF2)7SO3 - 、CF3CO2 - 、CH3CO2 - 、SCN - and (CF3CF2SO2)2N - One or more selected from the group consisting of can be used.

[0202] In addition to the electrolyte components, the electrolyte may further contain one or more additives such as haloalkylene carbonate compounds such as difluoroethylene carbonate, pyridine, triethyl phosphite, triethanolamine, cyclic ethers, ethylenediamine, n-glyme, hexamethylphosphoric triamide, nitrobenzene derivatives, sulfur, quinoneimine dyes, N-substituted oxazolidinones, N,N-substituted imidazolidines, ethylene glycol dialkyl ethers, ammonium salts, pyrrole, 2-methoxyethanol, or aluminum trichloride for the purpose of improving the life characteristics of the battery, suppressing the decrease in battery capacity, and improving the discharge capacity of the battery.

[0203] One embodiment of the present invention provides a battery module including the secondary battery as a unit cell and a battery pack including the same. Since the battery module and the 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-sized devices selected from the group consisting of electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, and power storage systems.

Examples

[0204] Hereinafter, preferred embodiments are presented to assist in understanding the present invention. However, these embodiments are for illustrative purposes only, and it is obvious to those skilled in the art that various changes and modifications are possible within the scope of this description and the scope of the technical idea. It goes without saying that such variations and modifications belong to the scope of the appended claims.

[0205] <Production Example> <Production of the negative electrode active materials of Examples 1 to 6> After the chemical reaction of silane gas, a silicon-based active material was formed on the substrate through vapor deposition. Then, a silicon oxide coating layer was formed on the surface of the silicon-based active material by the method shown in Table 1 below.

[0206] <Production of the negative electrode active material of Comparative Example 1> A negative electrode active material was produced in the same manner as in Example 1, except that a silicon oxide coating layer was not formed in Example 1.

[0207] <Production of the negative electrode active material of Comparative Example 2> After the chemical reaction of silane gas, a silicon-based active material was formed on the substrate through vapor deposition. Then, a silicon oxide coating layer was formed on the surface of the silicon-based active material by the method shown in Table 1 below. At this time, the silicon oxide coating layer was obtained by base treatment after heat treatment oxidation. After the formation of the oxide coating layer, the O content of the oxide layer was reduced by strong base treatment to produce a negative electrode active material.

[0208] For reference, in Table 1 below, the crystallinity of the silicon oxide coating layer corresponds to the process of confirming whether the oxide layer formed through XRD measurement shows a crystal structure.

[0209]

Table 1

[0210] <Production of the negative electrode> A negative electrode active material containing the silicon-based active material, a first conductive material, a second conductive material, and polyacrylamide as a binder were added to distilled water as a solvent for forming a negative electrode slurry at a weight ratio of 80:9.6:0.4:10 to produce a negative electrode slurry (solid content concentration: 25% by weight).

[0211] Specifically, the first conductive material is plate-shaped graphite (specific surface area: 17 m 2 / g, average particle size (D50): 3.5 μm), and the second conductive material is SWCNT.

[0212] As a specific mixing method, the first conductive material, the second conductive material, the binder, and water were dispersed at 2500 rpm for 30 min using a homomixer, then the silicon-based active material was added, and then dispersed at 2500 rpm for 30 min to prepare a negative electrode slurry.

[0213] The negative electrode slurry was coated on both sides of a copper current collector (thickness: 8 μm) as a negative electrode current collector layer at a loading amount of 85 mg / 25 cm 2 and rolled (roll press), and dried in a vacuum oven at 130 °C for 10 hours to form a negative electrode active material layer (thickness: 33 μm), which was used as the negative electrode (negative electrode thickness: 41 μm, negative electrode porosity: 40.0%).

[0214] <Manufacture of secondary battery> As a positive electrode active material, LiNi 0.6 Co 0.2 Mn 0.2 O2 (average particle size (D50): 15 μm), carbon black (product name: Super C65, manufacturer: Timcal) as a conductive material, and polyvinylidene fluoride (PVdF) as a binder were added to N-methyl-2-pyrrolidone (NMP) as a solvent for forming a positive electrode slurry at a weight ratio of 97:1.5:1.5 to produce a positive electrode slurry (solid content concentration: 78% by weight).

[0215] The positive electrode slurry was coated on both sides of an aluminum current collector (thickness: 12 μm) as a positive electrode current collector at 537 mg / 25 cm 2Coated with the loading amount, roll pressed, and dried in a vacuum oven at 130 °C for 10 hours to form a positive electrode active material layer (thickness: 65 μm) to fabricate a positive electrode (thickness of the positive electrode: 77 μm, porosity 26%).

[0216] An electrolyte was injected between the positive electrode and the negative electrodes of the examples and comparative examples through a polyethylene separator to fabricate a lithium secondary battery.

[0217] The electrolyte was prepared by adding vinylene carbonate at 3 wt% based on the total weight of the electrolyte to an organic solvent in which fluoroethylene carbonate (FEC) and diethyl carbonate (DEC) were mixed at a volume ratio of 10:90, and adding LiPF6 as a lithium salt at a concentration of 1 M.

[0218] <Experimental Example> Experimental Example 1: Monocell Life Evaluation The secondary batteries including the negative electrodes manufactured in the examples and comparative examples were evaluated for their life using an electrochemical charge / discharge device, and the capacity retention rate was evaluated. The secondary batteries were subjected to an In-situ cycle test at 4.2 - 3.0 V, 1C / 0.5C, and charged / discharged at 0.33C / 0.33C (4.2 - 3.0 V) every 50 cycles during the test to measure the capacity retention rate, and the results are shown in Table 2. Capacity retention rate (%) = {(Discharge capacity at the Nth cycle) / (Discharge capacity at the first cycle)} × 100

[0219]

Table 2

[0220] Experimental Example 2: Evaluation of @SOC50 2.5C Discharge Resistance Increase Rate (After 200 Cycles) During the test in Experimental Example 1, after measuring the capacity retention rate by charging / discharging at 0.33C / 0.33C (4.2 - 3.0 V) every 50 cycles, the battery was discharged at 2.5C pulse at SOC50 to measure the resistance, and the resistance increase rate was compared and analyzed. Regarding the evaluation of the resistance increase rate, the data at 200 cycles were calculated respectively, and the results were as shown in Table 3 below. [Table 3]

[0221] Experimental Example 3: Volume Change Amount Due to Gas Generation at 40°C Using Pouch Test After putting 20 g of the negative electrode slurry produced in the above Examples and Comparative Examples into a pouch, sealing it, and storing it in an oven at 40°C, the volume change with the passage of time was measured using a graduated cylinder, and the results are shown in Table 4 below. [Table 4]

[0222] As can be confirmed from Tables 2 and 3 above, in the cases of Examples 1 to 6 in which the silicon oxide coating layer according to the present application was formed, it was confirmed that the life evaluation and the resistance increase rate were higher or equal compared to Comparative Examples 1 and 2. This corresponds to the result that when using the silicon-based active material according to the present application, it becomes possible to react uniformly during the insertion and desorption reactions of lithium during charge and discharge, reduce the stress received by the silicon-based active material, relieve the cracking of the particles, and thereby improve the life of the electrode.

[0223] Furthermore, in the cases of Examples 1 to 6 in which the silicon oxide coating layer according to the present application was formed, as can be seen from Table 4 that the gas generation amount decreased compared to Comparative Examples 1 and 2 in which the silicon oxide coating layer was not formed, it was found that the volume change amount was lower compared to Comparative Examples 1 and 2.

[0224] This corresponds to the result that the negative electrode active material according to the present application in the slurry state has the contact with water blocked and the gas generation reduced.

[0225] Furthermore, in the case of Comparative Example 2, it corresponds to the one in which the ratio of O is adjusted to be less than the scope of the present application through the base treatment on the silicon oxide layer. In this case, it can be confirmed that the gas generation suppression effect is reduced due to the formation of defects in the silicon oxide coating layer, and as a result, it can be confirmed that the same experimental results as those of Comparative Example 1 without coating the silicon oxide coating layer are shown.

Explanation of reference numerals

[0226] 10 ··· Negative electrode current collector layer 20 ··· Negative electrode active material layer 30 ··· Separator 40 ··· Positive electrode active material layer 50 ··· Positive electrode current collector layer 100 ··· Negative electrode for lithium secondary battery 200 ··· Positive electrode for lithium secondary battery

Claims

1. A negative electrode active material comprising a silicon-based active material and a silicon oxide coating layer surrounding at least a part of the outer surface of the silicon-based active material, wherein the oxygen (O) atom content of the silicon oxide coating layer is 40% or more based on 100% of all atoms contained in the silicon oxide coating layer, the silicon-based active material includes at least one selected from the group consisting of SiO x (x = 0) and SiO x (0 < x < 2), and based on 100 parts by weight of the silicon-based active material, the SiO x (x = 0) is contained in an amount of 70 parts by weight or more.

2. The negative electrode active material according to claim 1, wherein the thickness of the silicon oxide coating layer is 1 nm or more and 3 μm or less.

3. The negative electrode active material according to claim 1, wherein the crystal grain size of the silicon-based active material is 200 nm or less.

4. The negative electrode active material according to claim 1, wherein the average particle size (D50) of the silicon-based active material is 3 μm to 10 μm.

5. The negative electrode active material according to claim 1, wherein the oxygen (O) atom content of the silicon oxide coating layer is 60% or more based on 100% of all atoms contained in the silicon oxide coating layer.

6. The negative electrode active material according to claim 1, wherein the area of the silicon oxide coating layer is 90% or more based on the outer surface of the silicon-based active material.

7. The negative electrode active material according to claim 1, wherein the silicon oxide coating layer includes at least one selected from the group consisting of crystalline silicon and amorphous silicon.

8. A step of chemically reacting silane gas to deposit a silicon-based active material on a substrate, a step of obtaining the silicon-based active material deposited on the substrate, and a step of forming silicon oxide on the surface of the silicon-based active material, wherein the method for manufacturing a negative electrode active material includes: the step of forming the silicon oxide includes a step of oxidizing the silicon-based active material by heat treatment or chemical treatment or a step of coating silicon oxide on the surface of the silicon-based active material, a negative electrode active material manufacturing method according to any one of claims 1 to 7, including a silicon oxide coating layer surrounding at least a part of the outer surface of the silicon-based active material, and the oxygen (O) atom content of the silicon oxide coating layer is 40% or more based on 100% of all atoms contained in the silicon oxide coating layer.

9. The method for manufacturing a negative electrode active material according to claim 8, wherein the silane gas contains at least one gas selected from monosilane, dichlorosilane, and trichlorosilane.

10. The step of chemically reacting the silane gas to deposit a silicon-based active material on a substrate is performed under conditions of a high temperature of 100 °C or higher. The method for manufacturing a negative electrode active material according to claim 8.

11. A negative electrode composition comprising the negative electrode active material, the negative electrode conductive material, and the negative electrode binder according to any one of claims 1 to 7.

12. The negative electrode active material is 60 parts by weight or more based on 100 parts by weight of the negative electrode composition. The negative electrode composition according to claim 11.

13. The negative electrode conductive material includes at least one selected from the group consisting of a dot-shaped conductive material, a planar conductive material, and a linear conductive material. The negative electrode composition according to claim 11.

14. Including a negative electrode current collector layer and a negative electrode active material layer provided on one or both surfaces of the negative electrode current collector layer. The negative electrode active material layer contains the negative electrode composition according to claim 11 or a cured product thereof. A negative electrode for a lithium secondary battery.

15. The thickness of the negative electrode current collector layer is 1 μm or more and 100 μm or less. The thickness of the negative electrode active material layer is 20 μm or more and 500 μm or less. The negative electrode for a lithium secondary battery according to claim 14.

16. A positive electrode. The negative electrode for a lithium secondary battery according to claim 14. A separator provided between the positive electrode and the negative electrode, and An electrolyte. A lithium secondary battery comprising the above.

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