Title of the invention: Spherical carbon-based negative electrode active material, manufacturing method thereof, negative electrode and lithium secondary battery comprising the same technical field [One] The present invention relates to a spherical carbon-based negative active material, a method for manufacturing the same, an anode and a lithium secondary battery comprising the same, and more particularly, to a spherical carbon-based negative active material with reduced internal pores and improved sphericity, It relates to a manufacturing method thereof, an anode including the same, and a lithium secondary battery. [2] This application claims priority based on Korean Application No. 10-2019-0123397 filed on October 4, 2019, and all contents disclosed in the specification of the application are incorporated herein by reference. background [3] As technology development and demand for mobile devices increase, the demand for secondary batteries as an energy source is rapidly increasing. Among these secondary batteries, a lithium secondary battery having a high energy density and voltage, a long cycle life, and a low discharge rate has been commercialized and widely used. [4] A lithium secondary battery has a structure in which an electrolyte containing lithium salt is impregnated in an electrode assembly with a porous separator interposed between a positive electrode and a negative electrode, each of which is coated with an active material on an electrode current collector, and the electrode is an active material, a binder And it is prepared by applying a slurry in which a conductive material is dispersed in a solvent to a current collector, drying and pressing. [5] Lithium metal was used as a negative electrode of a conventional secondary battery, but as the battery short circuit due to the formation of dendrites and the risk of explosion due to this are known, reversible intercalation of lithium ions while maintaining structural and electrical properties ) and carbon-based compounds capable of desorption are being replaced. [6] The carbon-based compound has a very low discharge potential of about -3 V with respect to the standard hydrogen electrode potential, and excellent electrode life cycle life due to a very reversible charge/discharge behavior due to the uniaxial orientation of the graphite layer indicates In addition, since the electrode potential is 0V Li/Li+ when charging Li ions and can exhibit a potential almost similar to that of pure lithium metal, there is an advantage that higher energy can be obtained when an oxide-based positive electrode and a battery are formed. [7] As the carbon-based compound, various types of carbon-based materials including artificial graphite, natural graphite, and hard carbon have been applied. Among the carbon-based compounds, graphite is currently most widely used. [8] Among the graphite, natural graphite is used to reduce irreversible reaction and improve the fairness of the electrode by changing it to a smooth surface shape through post-processing such as spheronization, and coating low-crystalline carbon such as pitch through heat treatment. By covering the surface, it is possible to prevent the edge surface of graphite from being exposed as it is, to prevent destruction by electrolyte and to reduce irreversible reaction. The method of manufacturing an anode active material by coating low-crystalline carbon on spherical natural graphite is a method used by most anode material manufacturers. [9] However, the negative active material prepared by the above method is produced by spheroidizing natural graphite having a particle shape in the form of scales, and contains a large amount of voids inside the spheroidized graphite particles. These voids lower the density of the negative electrode active material, making it difficult to manufacture a high-density negative electrode plate. In the process of densifying the negative electrode active material layer on the current collector, the low crystalline carbon coating film is broken due to the exposure of the graphite edge surface, resulting in destruction and irreversible reaction by the electrolyte. problem will arise. [10] In addition, natural graphite has a major disadvantage of electrode swelling compared to artificial graphite, the internal pores generated in the spheroidization process of natural graphite are larger than that of artificial graphite, and the film layer formed by the many internal pores is gas due to side reactions at high temperature. Generation and high temperature storage performance may be deteriorated. DETAILED DESCRIPTION OF THE INVENTION technical challenge [11] Accordingly, the present invention is to solve the above problems, and one object of the present invention is to have a spherical carbon-based anode active material with reduced internal pores and improved sphericity, a method for preparing the same, a negative electrode comprising the same, and lithium To provide a secondary battery. [12] Another object of the present invention is to provide a negative electrode including the negative electrode active material and a lithium secondary battery having the same. means of solving the problem [13] In order to solve the problems of the present invention described above, according to one aspect of the present invention, there is provided a negative electrode active material of the following embodiment, a method for manufacturing the same, and a negative electrode and a secondary battery including the same. [14] According to a first embodiment, [15] preparing spheroidized granulated particles by mixing and spheroidizing small-grained flaky graphite and opposing flaky graphite having a larger average particle diameter than the fine-grained flaky graphite; [16] coating the spherical granulated particles with carbon; and [17] There is provided a method for producing a spherical carbon-based negative electrode active material comprising a; pulverizing the carbon-coated spherical granulated particles. [18] According to a second embodiment, according to the first embodiment, [19] The small-grained flaky graphite may have an average particle diameter of 20 to 50 μm, and the large-scale flaky graphite may have an average particle diameter of 50 to 100 μm. [20] According to a third embodiment, according to the first or second embodiment, [21] The weight ratio of the large-scale flaky graphite to the small-grained flaky graphite may be 70:30 to 40:60. [22] According to a fourth embodiment, [23] As a spherical carbon-based negative electrode active material, [24] The specific surface area value of the negative active material is 1.5 to 2.8 m 2 /g, [25] The total pore volume of the negative active material is 1.0e -2 to 1.8e -2 m 3 /g, [26] There is provided a spherical carbon-based anode active material, characterized in that the specific surface area of ​​pores having a size of 24 nm or more in the anode active material is 0.1 to 0.8 m 2 /g. [27] According to a fifth embodiment, according to a fourth embodiment, [28] The specific surface area value of the negative active material may be 1.8 to 2.5 m 2 /g. [29] According to a sixth embodiment, according to the fourth or fifth embodiment, [30] The total pore volume of the negative active material may be 1.19e -2 to 1.57e -2 m 3 /g. [31] According to a seventh embodiment, according to any one of the fourth to sixth embodiments, [32] The specific surface area of ​​pores having a size of 24 nm or more in the negative active material may be 0.3 to 0.7 m 2 /g. [33] According to an eighth embodiment, according to any one of the fourth to seventh embodiments, [34] The spheroidized carbon-based negative active material may have an average particle diameter of 10 to 20 μm. [35] According to a ninth embodiment, according to any one of the fourth to eighth embodiments, [36] The spheroidization degree of the spherical anode active material may be 0.82 to 0.98. [37] According to a tenth embodiment, [38] As an anode comprising a current collector, and a negative electrode active material layer positioned on at least one surface of the current collector, [39] An anode is provided, wherein the anode active material layer includes the spherical carbon-based anode active material according to any one of the fourth to ninth embodiments. [40] According to an eleventh embodiment, [41] There is provided a lithium secondary battery comprising the negative electrode according to the tenth embodiment. Effects of the Invention [42] According to one embodiment of the present invention, spheroidization is not performed by applying one type of existing flaky graphite, but by mixing flaky graphite with a large average particle diameter and flaky graphite with small flaky graphite to proceed with spheroidization. It is possible to provide a spherical carbon-based anode active material with improved internal pores and reduced internal pores. When such a negative active material is applied to the negative electrode of a secondary battery, internal stress is reduced, swelling characteristics are improved, and a secondary battery having excellent capacity retention when stored at a high temperature can be provided. Brief description of the drawing [43] The following drawings attached to this specification illustrate preferred embodiments of the present invention, and serve to further understand the technical idea of ​​the present invention together with the above-described content of the invention, so the present invention is limited to the matters described in those drawings It should not be construed as being limited. [44] 1 is a schematic diagram of a spheroidization step in a method for manufacturing a spheroidized carbon-based negative active material according to an embodiment of the present invention. [45] 2 is a schematic diagram of the spheroidization step in the conventional method for producing a spheroidized carbon-based negative electrode active material. Modes for carrying out the invention [46] Hereinafter, the terms or words used in the present specification and claims should not be construed as being limited to conventional or dictionary meanings, and the inventor appropriately defines the concept of the term in order to best describe his invention. It should be interpreted as meaning and concept consistent with the technical idea of ​​the present invention based on the principle that it can be done. [47] [48] A method for producing a spheroidized carbon-based negative electrode active material according to another aspect of the present invention, [49] preparing spheroidized granulated particles by mixing and spheroidizing small-grained flaky graphite and opposing flaky graphite having a larger average particle diameter than the fine-grained flaky graphite; [50] coating the spherical granulated particles with carbon; and [51] and pulverizing the carbon-coated spherical granulated particles. [52] [53] As a result of spheroidization by applying flaky graphite having a single average particle diameter in the prior art, in the present invention, the average particle diameter is mutually Mixing two other types of flaky graphite, namely, fine-grained flaky graphite and large-scale flaky graphite with a larger average particle diameter than the above-mentioned fine-grained flaky graphite By performing spheroidization, internal pores are reduced, spheroidization is improved, and when used as an electrode of a battery, swelling of the electrode is suppressed, and the performance of the battery is improved when stored at a high temperature. We want to provide an active material. [54] Hereinafter, each step will be described in detail. [55] First, spheroidized granulated particles are prepared by mixing and spheroidizing small-grained flaky graphite and large-scale graphite, which has a larger average particle diameter than the small-grained flaky graphite. [56] In this step, small-grained flaky graphite and large-scale flaky graphite having a larger average particle diameter than the fine-grained flaky graphite are prepared in a predetermined weight ratio, mixed, and spheroidized to prepare spheroidized granulated particles. [57] In this step, the small-grained flaky graphite is inserted and filled in the empty space (void) created between the opposing flaky graphites while they are in contact and assembling, the internal pores are reduced, and more dense spherical particles can provide [58] In this step, using a mixture of fine-grained flaky graphite and large-scale flaky graphite as a raw material, a spheronization method commonly known in the art, for example, a method of applying a mechanical treatment such as impact compression, friction or shear force is performed. can The mechanical treatment may be performed using a spheronization apparatus commonly known in the art, for example, a counter jet mill (Hosokawa Micron, JP), an ACM palverizer (Hosokawa Micron, JP), or a current jet (Nissin, JP). ) such as crushers, SARARA (Kawasaki Heavy Indestries, Ltd, JP), GRANUREX (Freund Corporation, JP), New Gramasin (Seishin, JP), Acromaster (Hosokawa Micron, JP), etc. granulators, pressure kneaders ), a kneader such as two rolls, a mechano microsystem, an extruder, a ball mill, a planetary mill, a mechano fusion system, a Nobilta, a hybridization, a compression shearing processing apparatus such as a rotary ball mill, etc. can be used. [59] According to one embodiment of the present invention, the mixture is put into the spheronization device to which the above-described mechanical shear force is applied to form a granulated particle core, and 1 in a concentric direction to the surface of the granulated particle core. It is possible to form spherical granulated particles in which a surface layer in a spherically bonded form is formed by laminating more than one layer. The granulated particle core and the surface layer are formed simultaneously to form spherical granulated particles. [60] In one embodiment of the present invention, it is possible to obtain spherical granulated particles by repeatedly processing a mixture of small-grained flaky graphite and large-scale flaky graphite using a rotary processing machine. As a result of the repeated rotational movement, the grinding of the inner surface of the processing machine and the collision between the fine-grained flaky graphite and the opposing flaky graphite, the friction processing between the graphites, and the shearing caused by the shear stress, The granulation is performed, and finally, spheroidized granulated particles can be obtained. At this time, the grinding time and the grinding speed can be adjusted within an appropriate range according to the amount of graphite to be input. [61] In addition, in this step, the step of isotropically pressing the prepared spherical granulated particles can be additionally included so as to improve the contact between the small-grained flaky graphite and the opposing flaky graphite contained in the spherical granulated particles. have. [62] At this time, the isotropic pressurization refers to three-dimensionally uniformly pressurizing the spherical granulated particles, and water or argon is used as a medium at room temperature for isotropic pressurization of the spherical granulated particles, or isotropically pressurized at room temperature. Cold isostatic pressure treatment, etc. can be used. [63] In addition, the pressure for isotropically pressurizing the spheroidized granulated particles is not particularly limited, but preferably 50 to 100 atm, and more preferably 100 to 200 atm. [64] The flaky graphite refers to natural graphite having a particle shape in the form of scales, and may be prepared by pulverizing natural graphite such as scales, plate shapes, crushed shapes, and tablet shapes to a desired particle size. [65] In an embodiment of the present invention, the average particle diameter of the small-grained flaky graphite is 20 to 50 μm, or 25 to 45 μm, and the average particle diameter of the large scale graphite is 50 to 100 μm, or 55 to 90 μm. have. When the average particle diameter of the small-grained flaky graphite and the large-scale flaky graphite satisfies this range, the internal pores are reduced, and the film layer formed by the internal pores decreases gas generation and high-temperature storage performance due to side reactions at high temperatures. can be [66] In one embodiment of the present invention, the weight ratio of the opposing flaky graphite and small-grained flaky graphite is 70:30 to 40:60, or 70:30 to 45:55, or 70:30 to 50:50, or 50: 50 to 45:55. When the weight ratio of the large-scale flaky graphite to the small-grained flaky graphite satisfies this range, it may be advantageous in that the internal pores can be controlled. [67] Referring to FIG. 1 according to an embodiment of the present invention, when small-grained flaky graphite 110 and large-scale graphite 120 are mixed and subjected to the spheroidization process described above, spheroidized granulated particles 100 are formed At this time, the spherical granulated particles 100 are filled with the small-grained flaky graphite 110 in the space created between the opposing flaky graphites 120, so that the internal voids 130 can be greatly reduced. [68] On the other hand, referring to FIG. 2 according to the prior art, if the spheroidization process is performed using only the opposing scale graphite 210, the spherical granulated particles 200 can be obtained, but at this time the spherical granulated particles 200 It can be seen that the space created between the opposing scale-like graphite 210 is still maintained, so that the internal void 220 is very large. [69] Next, the spheroidized granulated particles are coated with carbon. [70] In this carbon coating step, the carbon coating material is attached to the surface of the spherical granulated particle by homogeneously mixing the surface of the previously prepared spherical granulated particle with the carbon coating material, and then carbonized by carbonizing it to form a carbon coating layer on the surface of the spherical granulated particle. can form. This carbon material forms a coating layer on the surface of the spherical granulated particles, and further bonds the small-grained graphite constituting the spherical granulated particles and the opposing scale-like graphite to each other, so that spheroidization that can occur by repeated charging and discharging A decrease in stability of the granulated particles can be prevented. [71] Examples of the carbon coating material include sucrose, phenol resin, naphthalene resin, polyvinyl alcohol resin, furfuryl alcohol resin, polyacrylonitrile resin, Polyamide resin, furan resin, cellulose resin, styrene resin, polyimide resin, epoxy resin or vinyl chloride resin, coal-based pitch, petroleum It may be prepared from a carbon precursor including a base pitch, polyvinyl chloride, mesophase pitch, tar, a block-copolymer, a low molecular weight heavy oil, or a mixture thereof. [72] In this case, 1 to 10 parts by weight, or 3 to 6 parts by weight of the carbon coating material may be used based on 100 parts by weight of the spherical granulated particles. When the content of the carbon coating layer satisfies this range, a problem in which the capacity per weight is reduced and the initial efficiency is reduced due to irreversibility due to the formation of an excessively thick coating layer, or an excessively thin coating layer is formed and the specific surface area of ​​the active material increases to increase side reactions And it is possible to prevent a problem in that the life efficiency is reduced due to peeling of the coating layer during the charging and discharging process, and it is helpful in the formation of the initial SEI layer to improve the stability of the spherical granulated particles that may be generated by repeated charging and discharging. [73] First, the method of homogeneously mixing the surface of the spheroidized granulated particles with the carbon coating material is not particularly limited and may be performed by a method commonly known in the art. For example, using a mechanochemical method such as a kneader such as two rolls, a blade, a mechano micro system, an extruder, a ball mill, a planetary mill, a mechano fusion system, a novelta, hydridation, a rotary ball mill, or It can be carried out using a spray dry method (spray dry), an emulsion method (emulsion), and the like. [74] After homogeneously mixing the carbon coating material and the spherical granulated particles in this way, the carbon coating layer can be formed on the spherical granulated particles by carbonization treatment at a temperature of 900 to 1,300° C. for 12 to 48 hours. The formed carbon coating layer may be made of amorphous or crystalline carbon. When the carbonization treatment conditions are satisfied, the carbon coating material is sufficiently stabilized, impurities in the carbon coating material are completely removed, and the coated surface properties of the carbon coating material are prevented from being denatured at excessively high temperatures. have. [75] Next, the carbon-coated spherical granulated particles are pulverized. [76] The spherical granulated particles obtained through the carbonization treatment in the step of carbon-coating the spherical granulated particles may exist in an aggregated form with each other. The agglomerated particles are subjected to a disintegration process to separate them from each other. [77] In the pulverization step, the molded article can be easily pulverized only by applying a slight shearing force to the obtained molded article. The pulverization step is not particularly limited, but, for example, can be carried out using a stirrer having a stirring blade, and a known pulverizer such as a conventional jet mill, vibration mill, pin mill, hammer mill, etc. can be carried out. [78] A spherical carbon-based negative active material according to another aspect of the present invention, [79] The specific surface area value of the negative active material is 1.5 to 2.8 m 2 /g, [80] The total pore volume of the negative active material is 1.0e -2 to 1.8e -2 m 3 /g, [81] The specific surface area of ​​pores having a size of 24 nm or more in the negative active material is 0.1 to 0.8 m 2 /g. [82] According to one embodiment of the present invention, the spheroidized carbon-based negative active material may be prepared by the above-described method for preparing the spherical carbon-based negative active material. [83] The specific surface area value of the negative active material may be 1.5 to 2.8 m 2 /g, and according to one embodiment of the present invention, 1.8 to 2.5 m 2 /g. When the specific surface area value of the negative electrode active material satisfies this range, it is advantageous in terms of high temperature storage performance by reducing side reactions with the electrolyte. [84] The "specific surface area" is measured by the BET method, and specifically, it can be calculated from the amount of nitrogen gas adsorbed under liquid nitrogen temperature (77 K) using BELSORP-mino II manufactured by BEL Japan. [85] The total pore volume of the negative active material may be 1.0e -2 to 1.8e -2 m 3 /g, and according to one embodiment of the present invention, 1.19e -2 to 1.57e -2 m 3 /g. When the total pore volume of the negative electrode active material satisfies this range, it is advantageous in terms of high temperature storage performance due to reduction of side reactions with the electrolyte. [86] In this case, the total pore volume of the negative electrode active material may be measured by the BET method in the same manner as the above-described specific surface area measurement, and may be measured using the same equipment as the specific surface area measurement method. [87] In addition, the specific surface area of ​​pores having a size of 24 nm or more in the negative active material is 0.1 to 0.8 m 2 /g, and according to one embodiment of the present invention, it may be 0.3 to 0.7 m 2 /g. When the specific surface area of ​​pores having a size of 24 nm or more in the anode active material satisfies this range, it is advantageous in reducing side reactions with the electrolyte. [88] The specific surface area of ​​pores having a size of 24 nm or more in the negative electrode active material may be measured by the BET method in the same manner as the above-described specific surface area measurement, and may be measured using the same equipment as the specific surface area measurement. [89] In particular, the specific surface area value of the negative active material is 1.5 to 2.8 m 2 /g, the total pore volume of the negative active material is 1.0e -2 to 1.8e -2 m 3 /g, and the negative active material has a size of 24 nm or more It is important that the specific surface area of ​​the pores having a specific surface area of ​​0.1 to 0.8 m 2 /g satisfies all of the conditions in that it is possible to suppress an increase in swelling due to gas generation in a long life by suppressing a side reaction due to an irreversible decrease. [90] According to one embodiment of the present invention, the average particle diameter of the spherical carbon-based negative active material may be 10 to 20 ㎛, or 11 to 18 ㎛. [91] The average particle diameter D50 means a particle diameter at 50% of the cumulative distribution of the number of particles according to the particle diameter. For example, D90 is a particle size at a point of 90% of the cumulative distribution of the number of particles according to the particle size, and D10 is a particle size at a point of 10% of the cumulative distribution of the number of particles according to the particle size. [92] The average particle diameter may be measured using a 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 (eg, Microtrac S3500) to measure the difference in diffraction pattern depending on the particle size when the particles pass through the laser beam to measure the particle size distribution can be calculated. D10, D50, and D90 can be measured by calculating the particle diameter at the point used as 10%, 50%, and 90% of the particle number cumulative distribution according to the particle diameter in a measuring apparatus. [93] The spheroidization degree of the spheroidized carbon-based negative active material may be 0.82 to 0.98, or 0.88 to 0.92. [94] The sphericity may be a value obtained by dividing the circumference of a circle having the same area as the projected image when the negative active material is projected by the perimeter of the projected image, and may be specifically expressed by Equation 1 below. The sphericity can be measured using a particle analyzer, for example, a particle analyzer such as sysmex FPIA3000 manufactured by Malvern. [95] [Equation 1] [96] Sphericity = circumference of a circle with the same area as the projected image of the active material / perimeter of the projected image [97] According to another aspect of the present invention, there is provided an anode including the anode active material. [98] Specifically, the negative electrode according to an embodiment of the present invention includes a current collector, and a negative electrode active material layer including the negative electrode active material according to the present invention on at least one surface of the current collector. [99] The electrode layer may be prepared by coating the slurry for the negative electrode active material layer obtained by dispersing the negative electrode active material, the binder and the conductive material according to the present invention in a solvent on at least one surface of the current collector, followed by drying and rolling. [100] The current collector is not particularly limited as long as it has conductivity without causing chemical change in the battery, and for example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, carbon, nickel on the surface of copper or stainless steel. , titanium, silver, etc. surface-treated, aluminum-cadmium alloy, etc. may be used. The thickness of the current collector is not particularly limited, but may have a commonly applied thickness of 3 to 500 μm. [101] The negative active material may be included in an amount of 80% to 99% by weight based on the total weight of the negative electrode slurry composition. [102] The binder is a component that assists in bonding between the conductive material, the active material, or the current collector, and is typically included in an amount of 0.1 to 20% by weight based on the total weight of the negative electrode slurry composition. Examples of such binders include polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HEP), polyvinylidenefluoride, polyacrylonitrile, polymethylmethacrylate , polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, polyacrylic acid, styrene butyrene rubber (SBR), lithium -substituted polyacrylate (lithium polyacrylate, Li-PAA), and the like. Among them, in particular, lithium-substituted polyacrylate (Li-PAA) can provide excellent adhesion compared to other binders, such as SBS/CMC, when used in a negative electrode having a high silicon content of about 80% in the active material, Due to these characteristics, it is advantageous in that it can be applied to a Si-based anode to achieve a high capacity retention rate during charging and discharging. [103] The conductive material is not particularly limited as long as it has conductivity without causing chemical change in the battery. For example, carbon such as carbon black, acetylene black, Ketjen black, channel black, Farness black, lamp black, thermal black, etc. black; conductive fibers such as carbon fibers and metal fibers; metal powders such as fluorocarbon, aluminum, and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; A conductive material such as a polyphenylene derivative may be used. The conductive material may be added in an amount of 0.1 to 20% by weight based on the total weight of the negative electrode slurry composition. [104] The dispersion medium may include water or an organic solvent such as N-methyl-2-pyrrolidone (NMP), in an amount that has a desirable viscosity when the negative electrode slurry contains a negative electrode active material, and optionally a binder and a conductive material. can be used [105] In addition, the coating method of the negative electrode slurry is not particularly limited as long as it is a method commonly used in the art. For example, a coating method using a slot die may be used, and in addition, a Mayer bar coating method, a gravure coating method, a dip coating method, a spray coating method, etc. may be used. [106] Another embodiment of the present invention relates to a lithium secondary battery including the negative electrode. Specifically, the lithium secondary battery may be manufactured by injecting a lithium salt-containing electrolyte into an electrode assembly including a positive electrode, the negative electrode as described above, and a separator interposed therebetween. [107] For the positive electrode, a slurry is prepared by mixing a positive electrode active material, a conductive material, a binder, and a solvent, and the slurry is directly coated on a metal current collector, or a positive electrode active material film, which is cast on a separate support and peeled from the support, is laminated on the metal current collector. Thus, a positive electrode can be manufactured. [108] As an active material used for the positive electrode, LiCoO 2 , LiNiO 2 , LiMn 2 O 4 , LiCoPO 4 , LiFePO 4 and LiNi 1-xyz Co x M1 y M2 z O 2 (M1 and M2 are each independently Al, Ni, Co, Fe, Mn, V, Cr, Ti, W, Ta, any one selected from the group consisting of Mg and Mo, x, y and z are each independently 0≤x<0.5, 0≤ as the atomic fraction of the oxide composition elements It may include any one active material particle selected from the group consisting of y<0.5, 0≤z<0.5, 0