Positive electrode active material, method for preparing same, and positive electrode and lithium secondary battery comprising same

Abstract

The present invention provides a positive electrode active material and a method for preparing same, the positive electrode active material comprising: lithium nickel-based oxide particles in the form of a single particle consisting of one single nodule or a pseudo-single particle which is a composite of 40 or fewer nodules; a coating layer formed on the surface of the nickel-based oxide particles, wherein in X-ray diffraction (XRD) analysis, the positive electrode active material shows an A value, defined by equation 1 below, of 1.2 to 3.7. [Equation 1] A = {(peak area in the range of diffraction angle 2θ of 37.1° to 37.9° / peak area in the range of diffraction angle 2θ of 36.0° to 37.1°)} × 100

Description

Positive electrode active material, method for producing same, positive electrode and lithium secondary battery comprising same Cross-citation with related applications This application claims the benefit of priority to Korean Patent Application No. 10-2023-0190391, filed December 22, 2023, and Korean Patent Application No. 10-2024-0137158, filed October 08, 2024, the entire contents of which are incorporated herein by reference. Technical field The present invention relates to a cathode active material, a method for producing the same, a cathode comprising the same, and a lithium secondary battery. Lithium secondary batteries are generally composed of a positive electrode, a negative electrode, a separator, and an electrolyte, and the positive electrode and negative electrode include an active material capable of intercalation and deintercalation of lithium ions. Lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), lithium manganese oxide (LiMnO2 or LiMnO4, etc.), lithium iron phosphate compound (LiFePO4), etc. have been used as positive active materials for lithium secondary batteries. In order to complement the problems of lithium transition metal oxides containing only Ni, Co, or Mn, lithium composite transition metal oxides containing two or more transition metals have been developed, and among these, lithium nickel cobalt manganese oxide containing Ni, Co, and Mn is widely used in the field of electric vehicle batteries. Conventional lithium nickel cobalt manganese oxides are generally in the form of spherical secondary particles in which tens to hundreds of primary particles are aggregated. However, when lithium nickel cobalt manganese oxides in the form of secondary particles in which many primary particles are aggregated are applied, there is a problem in that the primary particles are likely to break during the rolling process during the manufacture of the positive electrode, and cracks occur inside the particles during the charge and discharge process. When the positive electrode active material is broken or cracked, the contact area with the electrolyte increases, which increases gas generation and active material degradation due to side reactions with the electrolyte, and this reduces the life characteristics. In order to solve the above problems, a technology has been proposed to manufacture a single particle type positive electrode active material rather than a secondary particle type by increasing the sintering temperature during the manufacture of lithium nickel cobalt manganese oxide. In the case of a single particle type positive electrode active material, the contact area with the electrolyte is smaller than that of a conventional secondary particle type positive electrode active material, so there is less side reaction with the electrolyte, and the particle strength is excellent, so there is less particle breakage during electrode manufacture. Therefore, when a single particle type positive electrode active material is applied, there is an advantage of excellent gas generation and life characteristics. However, conventional single particle type cathode active materials require a high sintering temperature during synthesis, and as a result, there is a problem in that the crystal structure on the particle surface changes from a layered structure to a rock-salt structure. The surface of the rock-salt structure, which is an insulator, has a problem in that it hinders the movement of lithium ions during charge and discharge, thereby reducing the lifespan of the battery. Therefore, there is a need to develop a cathode active material with a surface-optimized coating layer shape to reduce gas generation and improve life characteristics. The present invention aims to provide a cathode active material capable of reducing gas generation and improving high-temperature life characteristics by optimizing the shape of a cobalt coating layer on the surface of a lithium nickel-based oxide in the form of single particles, a method for producing the same, and a cathode and lithium secondary battery including the same. [1] The cathode active material of the present invention comprises lithium nickel-based oxide particles in the form of single particles consisting of one single nodule or quasi-single particles consisting of a composite of 40 or fewer nodules, and a coating layer formed on the surface of the lithium nickel-based oxide particles, wherein the cathode active material has an A of 1.2 to 3.7 as defined by the following formula 1 when analyzed by X-ray diffraction (XRD). [Formula 1] A = {(peak area in the region where the diffraction angle 2θ is 37.1° to 37.9°) / (peak area in the region where the diffraction angle 2θ is 36.0° to 37.1°)} × 100 [2] The present invention provides a positive electrode active material having a peak area of ​​120 to 160 in a region where the diffraction angle 2θ is 36.0° to 37.1° in the above [1]. [3] The present invention provides a positive electrode active material, wherein, in the above [1] or [2], the area of ​​the peak in the region where the diffraction angle 2θ is 37.1° to 37.9° is 1 to 5. [4] The present invention provides a positive electrode active material, wherein in at least one of the above [1] to [3], the coating layer has a form including both a dot shape and a film shape. [5] The present invention provides a positive electrode active material, wherein, in at least one of the above [1] to [4], the coating layer contains Co. [6] The present invention provides a cathode active material, wherein, in at least one of the above [1] to [5], the coating layer further includes at least one selected from the group consisting of B, Ti, Mg, Al, Zr, Y, Ba, Ca, Zn, Sr, W, Ta, Nb, and Mo. [7] The present invention, in at least one of the above [1] to [6], the positive electrode active material has an average particle diameter (D 50 ) provides a positive electrode active material having a diameter of 3.0 μm to 5.0 μm. [8] The present invention, in at least one of the above [1] to [7], the positive electrode active material has a BET specific surface area of ​​0.4 m 2 / g to 1.0m 2 / g, providing a positive electrode active material. [9] The present invention provides a positive electrode active material, wherein, in at least one of the above [1] to [8], the lithium nickel-based oxide has a composition represented by the following chemical formula 1. [Chemical Formula 1] Li a Ni b Co c M 1 d M 2 e O2 In the above chemical formula 1, M 1 At least one selected from the group consisting of Mn and Al, and M 2 is at least one selected from the group consisting of Ba, Ca, Zr, Ti, Mg, Ta, Nb, and Mo, and 0.8≤a≤1.5, 0.8≤b≤1.0, 0≤c≤0.2, 0≤d≤0.2, 0≤e≤0.2.

[0010] The present invention provides a method for producing a positive electrode active material, comprising the steps of mixing a transition metal precursor containing nickel, cobalt, and manganese and a lithium raw material and then calcining the mixture to produce a lithium nickel-based oxide, and the steps of mixing the lithium nickel-based oxide with cobalt, performing a first coating at a temperature of 450° C. to 600° C. and a second coating at 600° C. to 850° C. to produce a positive electrode active material including a coating layer on the surface of the lithium nickel-based oxide, wherein the lithium nickel-based oxide is in the form of a single particle consisting of one single nodule or a quasi-single particle which is a composite of 40 or fewer nodules, and wherein the positive electrode active material has an A of 1.2 to 3.7 as defined by the following Formula 1 when analyzed by X-ray diffraction (XRD). [Formula 1] A = {(peak area in the region where the diffraction angle 2θ is 37.1° to 37.9°) / (peak area in the region where the diffraction angle 2θ is 36.0° to 37.1°)} × 100

[0011] The present invention provides a method for manufacturing a positive electrode active material, wherein, in the above

[0010] , the first coating and the second coating are performed for 1 to 10 hours.

[0012] The present invention provides a positive electrode comprising a positive electrode active material according to at least one of [1] to [9].

[0013] The present invention provides a lithium secondary battery including the positive electrode of

[0012] . The cathode active material according to the present invention can improve side reactions with an electrolyte by optimizing the shape of a cobalt-containing coating layer on the surface of a lithium nickel-based oxide in the form of a single particle, thereby reducing gas generation and improving high-temperature life characteristics. Figure 1 is a SEM (Scanning Electron Microscope) image of a positive electrode active material manufactured according to Example 1 of the present invention. Figure 2 is a SEM (Scanning Electron Microscope) image of a positive electrode active material manufactured according to Example 2 of the present invention. Figure 3 is a SEM (Scanning Electron Microscope) image of a positive electrode active material manufactured by Comparative Example 1 of the present invention. Figure 4 is a SEM (Scanning Electron Microscope) image of a positive electrode active material manufactured by Comparative Example 2 of the present invention. Figure 5 is a graph showing the results of XRD analysis of positive electrode active materials manufactured according to Examples 1 and 2 and Comparative Examples 1 and 2 of the present invention. The terms or words used in this specification and claims should not be interpreted as limited to their usual or dictionary meanings, but should be interpreted as having meanings and concepts that conform to the technical idea of ​​the present invention, based on the principle that the inventor can appropriately define the concept of the term in order to explain his or her own invention in the best manner. The terminology used herein is for the purpose of describing embodiments only and is not intended to limit the invention. In this specification, the singular also includes the plural unless specifically stated otherwise. The terms "comprises" and / or "comprising" as used herein do not exclude the presence or addition of one or more other components in addition to the components mentioned. In this specification, when it is said that a part includes a certain component, this does not mean that other components are excluded, but rather that other components may be included, unless otherwise specifically stated. In this specification, “%” means weight percent unless otherwise explicitly indicated. In the present invention, a “single particle” is a particle composed of one single nodule. In the present invention, “quasi-single particle” means a composite particle formed of 40 or fewer nodules. In the present invention, "nodule" means a particle unit body constituting a single particle and a quasi-single particle, and the nodule may be a single crystal lacking a crystalline grain boundary, or a polycrystal in which no grain boundary exists in appearance when observed with a scanning electron microscope (SEM) at a magnification of 5,000 to 20,000 times. The average particle diameter of the nodule may be measured as the arithmetic mean of the particle diameters of each nodule measured using a scanning electron microscope (SEM). In the present invention, "secondary particle" means a particle formed by agglomeration of tens to hundreds of primary particles. More specifically, the secondary particle is an agglomerate of more than 40 primary particles. The expression "particle" used in the present invention may include any one or all of a single particle, a quasi-single particle, a primary particle, a nodule, and a secondary particle. In the present invention, the "average particle diameter (D 50 )" means the particle size based on 50% of the volume cumulative particle size distribution of the positive electrode active material. The average particle diameter (D 50 ) can be measured using a laser diffraction method. For example, after dispersing the positive active material powder in a dispersion medium, it can be measured by introducing it into a commercially available laser diffraction particle size measuring device (e.g., Microtrac MT 3000), irradiating it with ultrasonic waves of about 28 kHz with an output of 60 W, obtaining a volume cumulative particle size distribution graph, and then finding the particle size corresponding to 50% of the volume cumulative amount. In the present invention, the “specific surface area” is measured by the BET method, and specifically, can be calculated from the nitrogen gas adsorption amount at liquid nitrogen temperature (77K) using BELSORP-mino II of BEL Japan. The present inventors have conducted repeated studies to develop a single-particle type positive electrode active material having excellent high-temperature life characteristics, and as a result, they have found that when a positive electrode active material is applied in which the area ratio A of peaks in a specific diffraction angle range during X-ray diffraction analysis (XRD) is adjusted to satisfy a specific range by performing primary and secondary coatings at different temperature ranges, the optimized shape of the coating layer is satisfied, thereby improving side reactions with the electrolyte, reducing gas generation, and implementing high-temperature life characteristics, thereby completing the present invention. Hereinafter, the present invention will be described in detail. The cathode active material, the method for producing the same, the cathode and / or the lithium secondary battery according to the present invention comprise at least one of the following disclosed configurations, and may comprise any combination between technically possible configurations among the following configurations. Bipolar active material The cathode active material according to the present invention is a cathode active material including lithium nickel-based oxide particles in the form of single particles consisting of one single nodule or quasi-single particles consisting of 40 or fewer nodules; and a coating layer formed on the surface of the lithium nickel-based oxide particles, wherein the cathode active material has A of 1.2 to 3.7 as defined by the following formula 1 when analyzed by X-ray diffraction (XRD). [Formula 1] A = {(peak area in the region where the diffraction angle 2θ is 37.1° to 37.9°) / (peak area in the region where the diffraction angle 2θ is 36.0° to 37.1°)} × 100 At this time, the measurement conditions were Cu-Kα radiation standard, 2θ ranges of 36.0° to 37.1° and 37.1° to 37.9° were measured at 40 kV to obtain an X-ray diffraction analysis pattern. Through A defined by the above equation 1, the shape of the coating layer optimized for the surface of a lithium nickel oxide in the form of a single particle can be confirmed. When the value of A satisfies the above range, the coating layer can have a form that includes both a dot shape and a film shape. Specifically, the peak in the region where the diffraction angle 2θ is 37.1° to 37.9° reflects a thin and uniform coating layer mainly in the form of a film, which is a LiCoO2 (hereinafter, LCO) phase on the (101) crystal plane of the lithium nickel-based oxide particles, and the peak in the region where the diffraction angle 2θ is 36.0° to 37.1° mainly reflects a dot-shaped LCO phase. At this time, when the above A has a value of 1.2 to 3.7, this means that the peak intensities of the two regions are somewhat balanced. That is, it means that both the film in the region where the diffraction angle 2θ is 37.1° to 37.9° and the dot shape in the region where the diffraction angle 2θ is 36.0° to 37.1° exist. Therefore, in this case, since the coating layer includes both a dot shape and a film shape, the side reaction with the electrolyte on the surface of the lithium nickel-based oxide is improved, gas generation is reduced, and the high-temperature life characteristics can be improved by protecting the surface of the lithium nickel-based oxide. Preferably, the A value may be 1.5 to 3.5, 2.0 to 3.5, or 2.1 to 3.3. In the above formula 1, the coating form having an LCO phase on the surface of the lithium nickel-based oxide particles can be confirmed from the area of ​​the peak in the region where the diffraction angle 2θ is 37.1° to 37.9°. The area of ​​the peak in the region where the diffraction angle 2θ is 37.1° to 37.9° can be 1 to 5, preferably 2 to 5, and more preferably 3.0 to 3.5. When the above range is satisfied, it means that a thin and uniform layered (film) structure is formed, and in this case, there is an effect of improving ion mobility. In the above Equation 1, the coating shape of the lithium nickel-based oxide particle on the (101) crystal plane can be confirmed from the area of ​​the peak in the region where the diffraction angle 2θ is 36.0° to 37.1°. The area of ​​the peak in the region where the diffraction angle 2θ is 36.0° to 37.1° can be 120 to 160, 120 to 150, 135 to 148, or 140 to 148. When the above range is satisfied, it means that a dot shape has been formed, and since the dot shape has a large surface area, it can shorten the movement path of lithium ions, thereby increasing the electrochemical reaction rate. In conclusion, when the area of ​​the peak satisfies the above range, the cobalt coating layer on the surface of the lithium nickel-based oxide particle includes a dot shape and a film shape, so there is a surface protection effect (passivation) and an output characteristic improvement effect due to the dot-shaped LCO phase. The present invention includes lithium nickel-based oxide particles having a molar ratio of Ni of 80 mol% or more, preferably 90 mol% or more, among the total transition metals. When the molar ratio of Ni satisfies the above range, excellent capacity characteristics can be realized. The lithium nickel-based oxide particles are in the form of single particles consisting of one single nodule or pseudo-single particles consisting of a composite of 40 or fewer, preferably 2 to 30, and more preferably 2 to 20 nodules. Such lithium nickel-based oxides in the form of single particles and / or pseudo-single particles have higher particle strength than lithium nickel-based oxides in the form of conventional secondary particles in which tens to hundreds of primary particles are aggregated, and thus are less likely to be broken into particles during rolling. In addition, in the case of the lithium nickel-based oxide in the form of single particles or pseudo-single particles according to the present invention, since the number of sub-components (i.e., nodules) constituting the particles is small, the change due to volume expansion and contraction of the primary particles during charge and discharge is small, and accordingly, the occurrence of cracks inside the particles is also significantly reduced. The cathode active material according to the present invention includes a coating layer formed on the surface of the lithium nickel-based oxide particle. The coating layer may include cobalt (Co). The coating layer including cobalt suppresses the deterioration of the cathode active material during the charge / discharge process of the battery, thereby improving the high-temperature life characteristics. The cobalt content included in the coating layer may be 1 mol% to 5 mol%, preferably 1 mol% to 4 mol%, and more preferably 1 mol% to 3 mol%, based on 100 mol% of the lithium nickel-based oxide. If the cobalt content included in the coating layer is less than 1 mol% based on 100 mol% of the lithium nickel-based oxide, there may be a problem of poor high-temperature lifespan due to insufficient cobalt coating amount, and if it exceeds 5 mol%, the content of nickel contributing to the capacity among the entire transition metals may decrease, resulting in a problem of reduced charge capacity. The coating layer may further include at least one selected from the group consisting of Al, Mg, Ti, V, Cr, Mn, Zr, Nb, W, and B in addition to Co. The coating layer may preferably include Co and B. When the coating layer further includes B in addition to Co, the capacity improvement effect may be more excellent than in the case of a single cobalt-containing coating layer. Meanwhile, the cathode active material according to the present invention may specifically include a lithium nickel-based oxide having a composition as represented by the following chemical formula 1. [Chemical Formula 1] Li a Ni b Co c M 1 d M2 e O2 In the above chemical formula 1, M 1 is at least one selected from the group consisting of Mn and Al, and specifically may be Mn or a combination of Mn and Al, and M 2 is at least one selected from the group consisting of Ba, Ca, Zr, Ti, Mg, Ta, Nb and Mo. M 2 Elements are not essential, but when included in appropriate amounts, they can promote particle growth during sintering or play a role in improving crystal structure stability. The above a represents the molar ratio of lithium in the lithium nickel-based oxide, and may be 0.8≤a≤1.5, 0.8≤a≤1.2, 0.9≤a≤1.1, or 0.95≤a≤1.15. When the molar ratio of lithium satisfies the above range, a stable layered crystal structure can be formed. The above b represents the molar ratio of nickel among the total metal excluding lithium in the lithium nickel-based oxide, and may be 0.8≤b≤1.0, 0.8≤b<1.0, 0.85≤b<1.0, or 0.9≤b<1.0. When the molar ratio of nickel satisfies the above range, excellent capacity characteristics are exhibited, and in particular, when the molar ratio of nickel is 0.9 or higher, even better capacity characteristics can be implemented. The above c represents the molar ratio of cobalt among all metals excluding lithium in the lithium nickel oxide, and 0≤c≤0.2, 0 <c<0.2, 또는 0<c<0.18일 수 있다. The above d is M among all metals except lithium in lithium nickel oxide. 1 It represents the molar ratio of , 0≤d≤0.2, 0 <d<0.2, 또는 0<d<0.18일 수 있다. The above e is M of all metals except lithium in lithium nickel oxide. 2 It represents the molar ratio of elements, and can be 0≤e≤0.2, 0≤e≤0.15, or 0≤e≤0.1. The cathode active material according to the present invention has an average particle diameter (D 50 ) may be 3.0 ㎛ to 5.0 ㎛, 3.5 ㎛ to 5.0 ㎛, or 4.0 ㎛ to 4.5 ㎛. The average particle diameter (D) of the positive electrode active material according to the present invention 50 ) satisfies the above range, high energy density and low initial resistance characteristics can be realized. The average particle diameter (D) of the positive electrode active material 50 ) is less than 3.0㎛, the fine particle content increases, causing problems such as increased resistance or generation of high-temperature storage gas, and the average particle size (D 50 ) exceeds 5.0㎛, there may be problems with capacity and initial output. The cathode active material according to the present invention has a BET specific surface area of ​​0.4 m 2 / g to 1.0m 2 / g, 0.4m 2 / g to 0.8m 2 / g, or 0.4m 2 / g to 0.7m 2 / g. If the BET surface area of ​​the positive electrode active material is too low, the reaction area with the electrolyte is insufficient, making it difficult to implement sufficient capacity. If the surface area is too high, moisture absorption is rapid, and side reactions with the electrolyte are accelerated, making it difficult to secure life characteristics. Method for manufacturing positive electrode active material Next, a method for manufacturing the positive electrode active material of the present invention will be described. When manufacturing a cathode active material in which the molar ratio of Ni among the total transition metals is 80 mol% or more, the surface structure completion of the cathode active material may be low and the concentration of residual lithium may be high due to the high sintering temperature. Therefore, a technology is required that can improve the surface structure completion through a coating layer formed on the surface of lithium nickel-based oxide particles, reduce the concentration of residual lithium, and improve the resistance characteristics through optimization of the coating conditions. The method for manufacturing a cathode active material according to the present invention comprises the steps of mixing a transition metal precursor including nickel, cobalt, and manganese and a lithium raw material and then calcining to manufacture a lithium nickel-based oxide; and the step of mixing the lithium nickel-based oxide with cobalt, and then performing a first coating at a temperature of 450° C. to 600° C. and a second coating at 600° C. to 850° C. to manufacture a cathode active material including a coating layer on the surface of the lithium nickel-based oxide. The above lithium nickel-based oxide is in the form of a single particle consisting of one single nodule or a quasi-single particle which is a composite of 40 or fewer nodules, and the positive electrode active material has an A of 1.2 to 3.7 as defined by the following formula 1 when analyzed by X-ray diffraction (XRD). Since the above-described content is equally applicable, redundant explanation is omitted. [Formula 1] A = {(peak area in the region where the diffraction angle 2θ is 37.1° to 37.9°) / (peak area in the region where the diffraction angle 2θ is 36.0° to 37.1°)} × 100 Hereinafter, each step of the method for manufacturing a positive electrode active material is described in detail. First, a transition metal precursor including nickel, cobalt, and manganese and a lithium raw material are mixed and calcined to form a lithium nickel-based oxide. At this time, the transition metal precursor may be purchased and used as a commercially available precursor such as nickel-cobalt-manganese hydroxide, or may be manufactured according to a precursor manufacturing method known in the art, such as a coprecipitation method. For example, nickel (Ni), cobalt (Co) and M 1 After preparing a transition metal-containing solution containing an ammonium cation, a complex forming agent containing an ammonium cation and a basic aqueous solution are added to the transition metal-containing solution to cause a coprecipitation reaction, thereby preparing a transition metal precursor. The above transition metal-containing solution contains nickel-containing raw material, cobalt-containing raw material, M1 It may contain a raw material containing M 1 The containing raw material may be a manganese-containing raw material and / or an aluminum-containing raw material. The nickel-containing raw material may be, for example, a nickel-containing acetate, nitrate, sulfate, halide, sulfide, hydroxide, oxide or oxyhydroxide, and specifically, may be, but is not limited to, Ni(OH)2, NiO, NiOOH, NiCO3ㆍ2Ni(OH)2ㆍ4H2O, NiC2O2ㆍ2H2O, Ni(NO3)2ㆍ6H2O, NiSO4, NiSO4ㆍ6H2O, a fatty acid nickel salt, a nickel halide or a combination thereof. The cobalt-containing raw material may be a cobalt-containing acetate, nitrate, sulfate, halide, sulfide, hydroxide, oxide or oxyhydroxide, and specifically, may be, but is not limited to, Co(OH)2, CoOOH, Co(OCOCH3)2ㆍ4H2O, Co(NO3)2ㆍ6H2O, CoSO4, Co(SO4)2ㆍ7H2O or a combination thereof. The manganese-containing raw material may be, for example, a manganese-containing acetate, nitrate, sulfate, halide, sulfide, hydroxide, oxide, oxyhydroxide or a combination thereof, and specifically, may be, but is not limited to, manganese oxides such as Mn2O3, MnO2, Mn3O4; manganese salts such as MnCO3, Mn(NO3)2, MnSO4, manganese acetate, manganese dicarboxylic acid salts, manganese citrate, manganese fatty acid salts; manganese oxyhydroxide, manganese chloride or a combination thereof. The aluminum-containing raw material can be, for example, Al2O3, Al(OH)3, Al(NO3)3, Al2(SO4)3, (HO)2AlCH3CO2, HOAl(CH3CO2)2, Al(CH3CO2)3 aluminum halides or combinations thereof. The transition metal-containing solution contains nickel-containing raw materials, cobalt-containing raw materials, and M1 It is manufactured by adding the containing raw material to a solvent, specifically, water, or a mixed solvent of an organic solvent (e.g., alcohol, etc.) that can be uniformly mixed with water, or an aqueous solution of a nickel-containing raw material, an aqueous solution of a cobalt-containing raw material, and M 1 It may be manufactured by mixing the raw materials contained therein. The ammonium cation-containing complex forming agent may be, but is not limited to, NH4OH, (NH4)2SO4, NH4NO3, NH4Cl, CH3COONH4, NH4CO3 or a combination thereof. Meanwhile, the ammonium cation-containing complex forming agent may be used in the form of an aqueous solution, and at this time, water or a mixture of water and an organic solvent (specifically, alcohol, etc.) that can be uniformly mixed with water may be used as the solvent. The basic compound may be a hydroxide of an alkali metal or alkaline earth metal, such as NaOH, KOH or Ca(OH)2, a hydrate thereof or a combination thereof. The basic compound may also be used in the form of an aqueous solution, and in this case, water or a mixture of water and an organic solvent (specifically, alcohol, etc.) that can be evenly mixed with water may be used as the solvent. The basic compound is added to adjust the pH of the reaction solution, and can be added in an amount such that the pH of the metal solution becomes 8 to 12. The coprecipitation reaction can be carried out in an inert atmosphere such as nitrogen or argon, at a temperature range of 35°C to 80°C. Nickel-cobalt-M by the above process 1 The positive electrode active material precursor particles of hydroxide are generated and precipitated in the reaction solution. Nickel-containing raw material, cobalt-containing raw material and M 1By controlling the concentration of the contained raw material, a positive electrode active material precursor having a nickel (Ni) content of 80 mol% or more among the total metal content can be manufactured. The precipitated positive electrode active material precursor particles can be separated and dried according to a conventional method to manufacture a positive electrode active material precursor. Thereafter, the above transition metal precursor and lithium raw material can be mixed. As the lithium raw material, lithium-containing sulfate, nitrate, acetate, carbonate, oxalate, citrate, halide, hydroxide or oxyhydroxide can be used, and is not particularly limited as long as it can be dissolved in water. Specifically, the lithium raw material can be Li2CO3, LiNO3, LiNO2, LiOH, LiOHㆍH2O, LiH, LiF, LiCl, LiBr, LiI, CH3COOLi, Li2O, Li2SO4, CH3COOLi, or Li3C6H5O7, and any one of these or a mixture of two or more thereof can be used. The transition metal precursor and the lithium source material can be mixed so that the molar ratio of Li: total metal in the transition metal precursor is 1.2:1, 1.15:1, or 1.1:1. When the mixing ratio of the lithium source material and the transition metal precursor satisfies the above range, the layered crystal structure of the positive electrode active material is well developed, so that a positive electrode active material having excellent capacity characteristics and structural stability can be manufactured. Thereafter, the mixture can be calcined. The calcination can be performed in an air or oxygen atmosphere. In order to form a single-particle lithium nickel-based oxide, the calcination should be performed at a higher temperature than when producing a lithium nickel-based oxide in the form of secondary particles in the past. For example, when the precursor composition is the same, the calcination should be performed at a temperature that is about 30° C. to 100° C. higher than when producing a lithium nickel-based oxide in the form of secondary particles in the past. The calcination temperature for producing a single-particle lithium nickel-based oxide may vary depending on the metal composition in the precursor. For example, when producing a high-nickel single-particle lithium nickel-based oxide having a nickel (Ni) content of 80 mol% or more, the calcination temperature may be performed at a temperature of 800° C. to 1000° C., 800° C. to 950° C., or 850° C. to 950° C. When the sintering temperature satisfies the above range, a single particle lithium nickel oxide having excellent electrochemical properties can be produced. Additionally, the calcination can be performed for 6 to 35 hours, 6 to 20 hours, or 10 to 20 hours. When the calcination time satisfies the above range, a single particle lithium nickel-based oxide can be formed. Next, the lithium nickel-based oxide is mixed with cobalt, and then primary coating and secondary coating are performed to form a cathode active material including a coating layer on the surface of the lithium nickel-based oxide. The primary coating is performed at a temperature of 450°C to 600°C, and the secondary coating is characterized in that it is performed at a temperature of 600°C to 850°C. Residual lithium byproducts present on the surface of lithium nickel-based oxide particles include lithium hydroxide (LiOH) and lithium carbonate (Li2CO3). If the coating process is performed in two steps and the first coating is performed in a low temperature region, it can react with lithium hydroxide (LiOH) having a relatively low melting point to form a thin layer (film) of LCO on the surface. If the second coating is performed in a high temperature region within a specific temperature range, it can react with lithium carbonate (Li2CO3) having a high melting point to form a dot-shaped LCO phase on the surface, which can serve as LCO capable of implementing high output characteristics. The above first coating is performed at a temperature of 450°C to 550°C, preferably 465°C to 535°C, and more preferably 480°C to 520°C. If the above first coating is performed at a temperature of less than 450°C, there is a possibility that the lithium nickel-based oxide and cobalt may clump due to insufficient preliminary reaction, which causes a problem of forming an uneven coating layer, and if the first coating is performed at a temperature exceeding 550°C, the layered structure may be damaged by excessive heat, which causes a problem of forming an uneven coating layer. The above secondary coating is performed at a temperature of 600°C to 800°C, preferably 650°C to 800°C, and more preferably 650°C to 750°C. If the secondary coating is performed at a temperature of less than 600°C, the number of dot shapes on the surface increases relatively, which increases the area of ​​the uncoated portion on the surface of the lithium nickel-based oxide, resulting in a problem of poor long-term high-temperature performance. In addition, if the secondary coating is performed at a temperature exceeding 800°C, the LCO phase is not formed thinly on the surface, but lithium hydroxide (LiOH) and lithium carbonate (Li2CO3) both melt and enter the inside of the lithium nickel-based oxide particles, making it difficult to form a uniform coating layer. The above first coating can be performed for 1 hour to 10 hours, 1 hour to 7 hours, or 2 hours to 6 hours. The above secondary coating can be performed for 1 hour to 10 hours, 2 hours to 9 hours, or 3 hours to 8 hours. When the times of the first coating and the second coating satisfy the above ranges, a coating layer including both a dot shape and a film shape is formed, thereby improving the side reaction with the electrolyte on the surface of the lithium nickel-based oxide, reducing gas generation, and protecting the surface of the lithium nickel-based oxide, thereby improving the high-temperature life characteristics. For example, the surface of the lithium nickel-based oxide particles is coated with a cobalt compound. For example, the cobalt compound is Co(OH)2, CoOOH, Co(OCOCH3). 2· 4H2O, Co(NO3) 2· 6H2O, CoSO4, and Co(SO4) 2· It can be one or more of 7H2O. anode The positive electrode according to the present invention comprises the positive electrode active material of the present invention described above. Specifically, the positive electrode comprises a positive electrode current collector, a positive electrode active material layer formed on the positive electrode current collector, and the positive electrode active material layer comprises the positive electrode active material according to the present invention. Since the positive electrode active material has been described above, a detailed description thereof will be omitted, and only the remaining components will be described in detail below. The above-described positive electrode current collector may include a highly conductive metal, and is not particularly limited as long as it is easily adhered to a positive electrode active material layer but does not react in the voltage range of the battery. The positive electrode current collector may be, for example, made of stainless steel, aluminum, nickel, titanium, heat-treated carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, etc. In addition, the positive electrode current collector may typically have a thickness of 3 ㎛ to 500 ㎛, and fine unevenness may be formed on the surface of the current collector to increase the adhesion of the positive electrode active material. For example, the positive electrode current collector may be used in various forms such as a film, a sheet, a foil, a net, a porous body, a foam, and a non-woven fabric. The above-mentioned positive electrode active material layer may optionally include a conductive material and a binder, together with the above-mentioned positive electrode active material, as necessary. At this time, the positive electrode active material may be included in an amount of 80 wt% to 99 wt%, more specifically 90 wt% to 98 wt%, based on the total weight of the positive electrode active material layer. The conductive material is used to provide conductivity to the electrode, and can be used without special restrictions as long as it does not cause a chemical change in the battery to be formed and has electronic conductivity. Specific examples thereof include graphite such as natural graphite or artificial graphite; carbon-based materials such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, and carbon fiber; metal powders or metal fibers such as copper, nickel, aluminum, and silver; conductive tubes such as carbon nanotubes; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives, and the like. One of these may be used alone or a mixture of two or more may be used. The conductive material may be included in an amount of 0.01 wt% to 10 wt%, preferably 0.1 wt% to 9 wt%, and more preferably 0.1 wt% to 5 wt%, based on the total weight of the positive electrode active material layer. The above binder serves to improve the adhesion between positive electrode active material particles and the adhesion between the positive electrode active material and the current collector. Specific examples include polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylalcohol, polyacrylonitrile, polymethyl methacrylate, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene butadiene rubber (SBR), fluoroelastomer, polyacrylic acid, and polymers in which hydrogens of these are substituted with Li, Na, or Ca, or various copolymers thereof, and one of these may be used alone or a mixture of two or more thereof. The above binder may be included in an amount of 1 wt% to 30 wt%, preferably 1 wt% to 20 wt%, and more preferably 1 wt% to 10 wt%, based on the total weight of the positive electrode active material layer. The above positive electrode can be manufactured according to a conventional positive electrode manufacturing method, except that the above positive electrode active material is used. Specifically, the positive electrode slurry composition, which is manufactured by dissolving or dispersing the above positive electrode active material and optionally a binder, a conductive agent, and a dispersant in a solvent, can be manufactured by applying the positive electrode slurry composition onto a positive electrode current collector, followed by drying and rolling. The solvent may be a solvent generally used in the relevant technical field, and may include dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), dimethyl formamide (DMF), acetone, or water. One of these may be used alone or a mixture of two or more may be used. The amount of the solvent used is sufficient to dissolve or disperse the positive electrode active material, conductive material, binder, and dispersant, taking into account the coating thickness and manufacturing yield of the slurry, and to have a viscosity that can exhibit excellent thickness uniformity during subsequent coating for manufacturing the positive electrode. Alternatively, the positive electrode may be manufactured by casting the positive electrode slurry composition onto a separate support, and then peeling the resulting film from the support and laminating it onto a positive electrode current collector. Lithium secondary battery Next, a lithium secondary battery according to the present invention will be described. The above lithium secondary battery specifically includes a positive electrode, a negative electrode positioned opposite the positive electrode, and a separator and an electrolyte interposed between the positive electrode and the negative electrode. Since the positive electrode is the same as described above, a detailed description is omitted, and only the remaining components are specifically described below. In addition, the lithium secondary battery may optionally further include a battery container that accommodates the electrode assembly of the positive electrode, the negative electrode, and the separator, and a sealing member that seals the battery container. In the above lithium secondary battery, the negative electrode includes a negative electrode current collector and a negative electrode active material layer positioned on the negative electrode current collector. The above negative current collector is not particularly limited as long as it has high conductivity without causing a chemical change in the battery, and for example, copper, stainless steel, aluminum, nickel, titanium, heat-treated carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., an aluminum-cadmium alloy, etc. can be used. In addition, the negative current collector can typically have a thickness of 3 ㎛ to 500 ㎛, and, like the positive current collector, fine unevenness can be formed on the surface of the current collector to strengthen the bonding strength of the negative active material. For example, it can be used in various forms such as a film, a sheet, a foil, a net, a porous body, a foam, a non-woven fabric, etc. The above negative electrode active material layer optionally includes a binder and a conductive material together with the negative electrode active material. As the negative electrode active material, a compound capable of reversible intercalation and deintercalation of lithium can be used. Specific examples thereof include: carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber, and amorphous carbon; metallic compounds capable of alloying with lithium, such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloy, Sn alloy, and Al alloy; metallic oxides capable of doping and dedoping lithium, such as SiOβ (0 < β < 2), SnO2, vanadium oxide, and lithium vanadium oxide; or composites containing the metallic compounds and carbonaceous materials, such as Si-C composites or Sn-C composites, and any one or a mixture of two or more of these can be used. In addition, a metallic lithium thin film can be used as the negative electrode active material. In addition, the carbon material can be both low-crystalline carbon and high-crystalline carbon. Representative examples of low-crystallization carbon include soft carbon and hard carbon, and representative examples of high-crystallization carbon include amorphous, plate-like, flaky, spherical or fibrous natural or artificial graphite, Kish graphite, pyrolytic carbon, mesophase pitch-based carbon fiber, mesophase pitches, mesophase pitches, and high-temperature heat-treated carbon such as petroleum or coal tar pitch derived cokes. The above negative electrode active material may be included in an amount of 80 wt% to 99 wt%, 82 wt% to 99 wt%, or 84 wt% to 99 wt% based on the total weight of the negative electrode active material layer. The above binder is a component that assists in bonding between the conductive agent, the active material, and the current collector, and is typically added in an amount of 0.1 to 10 wt% based on the total weight of the negative electrode active material layer. Examples of such binders include polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene-butadiene rubber, nitrile-butadiene rubber, fluororubber, various copolymers thereof, and the like. The conductive agent is a component for further improving the conductivity of the negative electrode active material, and may be included in an amount of 1 wt% to 30 wt%, 1 wt% to 20 wt%, or 1 wt% to 10 wt% based on the total weight of the negative electrode active material layer. The conductive agent is not particularly limited as long as it has conductivity without causing a chemical change in the battery, and for example, graphite such as natural graphite or artificial graphite; carbon black such as acetylene black, Ketjen black, channel black, furnace black, lamp black, or thermal black; conductive fibers such as carbon fiber or metal fiber; fluorinated carbon; metal powder such as aluminum or nickel powder; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; conductive materials such as polyphenylene derivatives, etc. may be used. The above negative electrode active material layer can be manufactured by applying and drying a negative electrode slurry composition prepared by dissolving or dispersing a negative electrode active material, and optionally a binder and a conductive material in a solvent, on a negative electrode current collector, or by casting the negative electrode slurry composition on a separate support and then laminating the obtained film by peeling it off from the support on a negative electrode current collector. Meanwhile, in the lithium secondary battery, the separator separates the negative electrode and the positive electrode and provides a passage for lithium ions to move. If it is a separator that is usually used in lithium secondary batteries, it can be used without any special restrictions, and in particular, it is preferable that it has low resistance to ion movement of the electrolyte and excellent electrolyte moisture retention capacity. Specifically, a porous polymer film, for example, a porous polymer film made of a polyolefin polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, and an ethylene / methacrylate copolymer, or a laminated structure of two or more layers thereof, can be used. In addition, a conventional porous nonwoven fabric, for example, a nonwoven fabric made of high-melting-point glass fiber, polyethylene terephthalate fiber, etc. can be used. In addition, a coated separator containing a ceramic component or a polymer material can be used to secure heat resistance or mechanical strength, and can be selectively used in a single-layer or multi-layer structure. In addition, the electrolyte used in the present invention may include, but is not limited to, an organic liquid electrolyte, an inorganic liquid electrolyte, a solid polymer electrolyte, a gel-type polymer electrolyte, a solid inorganic electrolyte, a molten inorganic electrolyte, etc. that can be used in the manufacture of a lithium secondary battery. Specifically, the electrolyte may include an organic solvent and a lithium salt. As the organic solvent, any solvent that can act as a medium through which ions involved in the electrochemical reaction of the battery can move may be used without particular limitation. Specifically, the organic solvent may include ester solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, and ε-caprolactone; ether solvents such as dibutyl ether or tetrahydrofuran; ketone solvents such as cyclohexanone; aromatic hydrocarbon solvents such as benzene and fluorobenzene; Examples of solvents that can be used include carbonate solvents such as dimethylcarbonate (DMC), diethylcarbonate (DEC), methylethylcarbonate (MEC), ethylmethylcarbonate (EMC), ethylene carbonate (EC), and propylene carbonate (PC); alcohol solvents such as ethyl alcohol and isopropyl alcohol; nitriles such as R-CN (wherein R represents a linear, branched, or cyclic hydrocarbon group having 2 to 20 carbon atoms and may include a double-bonded aromatic ring or an ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; and sulfolanes. Among these, a carbonate solvent is preferable, and a mixture of a cyclic carbonate (e.g., ethylene carbonate or propylene carbonate, etc.) having high ionic conductivity and high dielectric constant that can improve the charge / discharge performance of the battery and a low-viscosity linear carbonate compound (e.g., ethyl methyl carbonate, dimethyl carbonate, or diethyl carbonate, etc.) is more preferable. The above lithium salt can be used without any special limitation as long as it is a compound capable of providing lithium ions used in a lithium secondary battery. Specifically, the anion of the above lithium salt is F - , Cl - , Br - , I - , NO3 - , N(CN)2 - , BF4 - , CF3CF2SO3 - , (CF3SO2)2N - , (FSO2)2N - , CF3CF2(CF3)2CO - , (CF3SO2)2CH - , (SF5)3C - , (CF3SO2)3C - , CF3(CF2)7SO3 - , CF3CO2 - , CH3CO2 - , SCN - and (CF3CF2SO2)2N - At least one selected from the group consisting of LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAl04, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2) 2. LiCl, LiI, or LiB(C2O4)2, etc. can be used. It is preferable to use the concentration of the lithium salt within the range of 0.1 M to 4.0 M, preferably 0.5 M to 3.0 M, and more preferably 1.0 M to 2.0 M. When the concentration of the lithium salt is within the above range, the electrolyte can exhibit excellent electrolyte performance because it has appropriate conductivity and viscosity, and lithium ions can move effectively. In addition to the electrolyte components, the electrolyte may further contain one or more additives, such as, for example, haloalkylene carbonate compounds such as difluoroethylene carbonate, pyridine, triethylphosphite, triethanolamine, cyclic ethers, ethylene diamine, n-glyme, hexaphosphoric acid triamide, nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinones, N,N-substituted imidazolidines, ethylene glycol dialkyl ethers, ammonium salts, pyrrole, 2-methoxy ethanol, or aluminum trichloride, for the purpose of improving the life characteristics of the battery, suppressing battery capacity decrease, and improving the discharge capacity of the battery. In this case, the additives may be contained in an amount of 0.1 to 10.0 wt% with respect to the total weight of the electrolyte. As described above, a lithium secondary battery including a cathode active material according to the present invention stably exhibits excellent discharge capacity, output characteristics, and capacity retention, and is therefore useful in portable devices such as mobile phones, laptop computers, and digital cameras, and electric vehicles such as hybrid electric vehicles (HEVs). Accordingly, according to another embodiment of the present invention, a battery module including the lithium secondary battery as a unit cell and a battery pack including the same are provided. The above battery module or battery pack can be used as a power source for one or more medium- to large-sized devices, including power tools; electric vehicles including electric vehicles (EVs), hybrid electric vehicles, and plug-in hybrid electric vehicles (PHEVs); or power storage systems. Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art can easily implement the present invention. However, the present invention may be implemented in various different forms and is not limited to the embodiments described herein. Examples and Comparative Examples Example 1 Ni 0.85 Co 0.05 Mn 0.1 (OH)2 and LiOH were mixed so that the molar ratio of Li: (Ni+Co+Mn) was 1.1:1, and calcined at 890℃ for 15 hours to obtain LiNi. 0.85 Co 0.05 Mn 0.1 A single particle lithium nickel oxide having a composition of O2 was prepared. Afterwards, the single particle type lithium nickel-based oxide was mixed with Co(OH)2 in a weight ratio of 100:0.2, and a first coating was performed at 500°C for 3 hours and a second coating was performed at 720°C for 6 hours to manufacture a cathode active material having a coating layer containing cobalt formed on the surface. Example 2 A positive electrode active material was manufactured in the same manner as in Example 1, except that the first coating was performed at 550°C for 3 hours and the second coating was performed at 680°C for 6 hours. Comparative Example 1 A positive electrode active material was manufactured in the same manner as in Example 1, except that the first coating was performed at 500°C for 3 hours and the second coating was performed at 880°C for 6 hours. Comparative Example 2 A positive electrode active material was manufactured in the same manner as in Example 1, except that the first coating was performed at 500°C for 3 hours and the second coating was performed at 570°C for 6 hours. Experimental Example 1 - Surface observation of positive electrode active material Using a scanning electron microscope, SEM images of the positive electrode active materials manufactured in Examples 1 to 2 and Comparative Examples 1 to 2 were obtained. These SEM images are shown in Figs. 1 to 4. Through FIGS. 1 and 2, it can be confirmed that the positive electrode active materials manufactured in Examples 1 and 2 have a cobalt coating layer present in both a dot shape and a film shape. On the other hand, through FIGS. 3 and 4, it can be confirmed that the cathode active material manufactured in Comparative Example 1 performed the secondary coating at a higher temperature than in the examples, so that cobalt and lithium hydroxide (LiOH), which has a relatively low melting point, reacted excessively and existed only in a film shape, and the cathode active material manufactured in Comparative Example 2 performed the secondary coating at a lower temperature than in the examples, so that cobalt and lithium carbonate (Li2CO3), which has a high melting point, reacted excessively and existed only in a dot shape. Experimental example 2: Average particle size (D) of positive electrode active material 50 ) measurement 0.005 g of each of the positive electrode active materials manufactured in the above Examples 1 to 2 and Comparative Examples 1 to 2 was dispersed in a dispersion medium, H2O, and then introduced into a commercially available laser diffraction particle size measuring device (e.g., Microtrac MT 3000) and irradiated with ultrasonic waves of about 28 kHz at an output of 60 W to obtain a volume cumulative particle size distribution graph of each positive electrode active material, and the average particle diameter (D) was obtained using the graph. 50 ) was obtained. The average particle diameter (D 50 ) is the particle size at the point where the cumulative distribution is 50% in the volume cumulative particle size distribution graph of the above positive electrode active material. The measurement results are shown in [Table 1] below. Average particle diameter (D 50 ) [㎛] Example 14.2 Example 24.1 Comparative Example 14.4 Comparative Example 24.1 Experimental Example 3: XRD Analysis of Positive Electrode Material In order to compare and analyze the coating layer included in the positive electrode active materials manufactured in Examples 1 to 2 and Comparative Examples 1 to 2, respectively, XRD analysis was performed on each positive electrode active material using Bruker's D8_Endeavor, and the results are shown in Fig. 5. Referring to FIG. 5 below, in the case of Example 1 and Comparative Example 1, it can be seen that since the difference between the first coating temperature and the second coating temperature is large, the change in peak intensity is large, and in the case of Example 2 and Comparative Example 2, since the difference between the first coating temperature and the second coating temperature is small, the change in peak intensity is relatively small. At this time, since the pattern and intensity of the peak observed in XRD vary depending on the temperature, evaluating only the presence or absence of the peak only confirms the presence or absence of the LCO phase. Therefore, the inventors of the present invention evaluated the area of ​​the peak within a specific angle region at a diffraction angle of 2θ, and confirmed the coating form on the (101) crystal plane of the lithium nickel-based oxide particle according to the change in temperature. Specifically, the measurement conditions were Cu-Kα radiation, 2θ range of 35° to 50° was measured at 40 kV to obtain an X-ray diffraction analysis pattern. In the final analysis data, the coating form on the (101) crystal plane of the lithium nickel-based oxide particles can be confirmed by the area of ​​the peak at 2θ of 36.0° to 37.1°. In addition, the coating form having a LiCoO2 (hereinafter, LCO) phase on the surface of each lithium nickel-based oxide particle can be confirmed by the area of ​​the peak at 2θ of 37.1° to 37.9°. A defined by the following Equation 1 was respectively calculated and shown in [Table 2] below. [Formula 1] A = {(peak area in the region where the diffraction angle 2θ is 37.1° to 37.9°) / (peak area in the region where the diffraction angle 2θ is 36.0° to 37.1°)} × 100 Area of ​​peak in the region where the diffraction angle 2θ is 36.0° to 37.1° Area of ​​peak in the region where the diffraction angle 2θ is 37.1° to 37.9° A value Example 1145.43.212.21 Example 2143.74.483.12 Comparative Example 1150.61.661.10 Comparative Example 2141.65.493.88 Experimental Example 4: Electrochemical Characteristics of Lithium Secondary Battery The high-temperature life characteristics and resistance characteristics of lithium secondary batteries manufactured as follows using the positive electrode active materials of Examples 1 to 2 and Comparative Examples 1 to 2 were evaluated. The measurement results are shown in [Table 3] below. <Manufacturing of lithium secondary batteries> The positive electrode active material, conductive material (carbon black), and PVDF binder manufactured in Examples 1 to 2 and Comparative Examples 1 to 2, respectively, were mixed in N-methylpyrrolidone at a weight ratio of 95:2:3 to manufacture a positive electrode slurry. The positive electrode slurry was applied to one surface of an aluminum current collector, dried at 130°C, and then rolled to manufacture a positive electrode. A negative electrode slurry was prepared by mixing a negative electrode active material (graphite (artificial: natural) = 50:50 weight ratio), a conductive agent (carbon nanotube), and a binder (styrene-butadiene rubber, SBR) in a weight ratio of 95.5:1.0:3.5 in water. The negative electrode slurry was applied onto a copper current collector sheet, dried, and then rolled to prepare a negative electrode. An electrode assembly was manufactured by interposing a separator between the positive and negative electrodes manufactured by the above-described method, and then the electrode assembly was placed inside a battery case, and an electrolyte was injected into the case to manufacture a battery cell. The electrolyte was manufactured by dissolving 0.6 M LiPF6 in a mixed organic solvent of ethylene carbonate (EC): dimethyl carbonate (DMC): ethyl methyl carbonate (EMC) = 1:2:1 by volume, and adding 2 wt% of vinylene carbonate (VC). Specifically, for each of the lithium secondary battery cells, the capacity retention rate and resistance increase rate at the 300th cycle were measured, with one cycle being charge / discharge in the voltage range of 2.5 V to 4.2 V under 0.1 C / 0.1 C conditions at 45°C. Capacity retention rate [%] Resistance increase rate [%] Example 185.885.1 Example 284.592.0 Comparative example 179.1116.5 Comparative example 282.1110.9 Through the above [Table 3], it can be confirmed that the lithium secondary batteries applying the positive electrode active materials of Examples 1 and 2, in which A defined by Equation 1 satisfies the scope of the present invention during XRD analysis, have higher capacity retention rates and lower resistance increase rates than the lithium secondary batteries applying the positive electrode active materials of Comparative Examples 1 and 2, and thus have superior high-temperature life characteristics and resistance characteristics. Experimental Example 5: Measurement of Gas Emission Each of the lithium secondary batteries manufactured above was charged to 4.2 V in CC-CV mode 0.33 C, and then the lithium secondary batteries were disassembled to separate the cathodes. Then, 400 mg of the cathode and 400 μL of the electrolyte were placed in a pouch-type battery case and sealed to manufacture a cell, and the cell was stored at 60° C. for 8 weeks, and the cell volume change (△Cell volume, unit: mL) before and after high-temperature storage was measured. The cell volume change was measured by placing the cell in water and measuring the change in the volume of water. The measurement results are shown in [Table 4] below. Gas generation [mL]Example 10.25Example 20.25Comparative Example 10.37Comparative Example 20.43 Through the above [Table 4], it can be confirmed that the lithium secondary battery applying the positive electrode active materials of Examples 1 and 2, where A defined by Equation 1 satisfies the scope of the present invention during XRD analysis, has a reduced amount of gas generation compared to the lithium secondary battery applying the positive electrode active materials of Comparative Examples 1 and 2.

Claims

1. A cathode active material comprising lithium nickel-based oxide particles in the form of single particles consisting of one single nodule or a composite of 40 or fewer nodules; and a coating layer formed on the surface of the lithium nickel-based oxide particles. The above positive electrode active material is a positive electrode active material, wherein, when analyzed by X-ray diffraction (XRD), A, defined by the following formula 1, is 1.2 to 3.

7. [Formula 1] A = {(peak area in the region where the diffraction angle 2θ is 37.1° to 37.9°) / (peak area in the region where the diffraction angle 2θ is 36.0° to 37.1°)} × 100 2. In claim 1, A cathode active material, wherein the area of ​​a peak in a region where the diffraction angle 2θ is 36.0° to 37.1° is 120 to 160.

3. In claim 1, A cathode active material, wherein the area of ​​a peak in a region where the diffraction angle 2θ is 37.1° to 37.9° is 1 to 5.

4. In claim 1, A positive electrode active material, wherein the coating layer has a form including both a dot shape and a film shape.

5. In claim 1, The above coating layer is a cathode active material containing Co.

6. In claim 5, A cathode active material, wherein the coating layer further includes at least one selected from the group consisting of B, Ti, Mg, Al, Zr, Y, Ba, Ca, Zn, Sr, W, Ta, Nb, and Mo.

7. In claim 1, The above positive electrode active material has an average particle diameter (D 50 ) is a positive electrode active material having a diameter of 3.0㎛ to 5.0㎛.

8. In claim 1, The above cathode active material has a BET surface area of ​​0.4 m 2 / g to 1.0m 2 / g, positive electrode active material.

9. In claim 1, The above lithium nickel-based oxide is a cathode active material having a composition represented by the following chemical formula 1. [Chemical Formula 1] Li a Ni b Co c M 1 d M 2 e O2 In the above chemical formula 1, M 1 At least one selected from the group consisting of Mn and Al, and M 2 is at least one selected from the group consisting of Ba, Ca, Zr, Ti, Mg, Ta, Nb, and Mo, and 0.8≤a≤1.5, 0.8≤b≤1.0, 0≤c≤0.2, 0≤d≤0.2, 0≤e≤0.

2.

10. A step of mixing a transition metal precursor including nickel, cobalt and manganese and a lithium raw material and then calcining to produce a lithium nickel-based oxide; and A step of manufacturing a cathode active material including a coating layer on the surface of the lithium nickel-based oxide by mixing the lithium nickel-based oxide with cobalt, performing a first coating at a temperature of 450° C. to 600° C. and a second coating at 600° C. to 850° C.; The above lithium nickel-based oxide is in the form of a single particle consisting of one single nodule or a quasi-single particle complex consisting of 40 or fewer nodules, A method for producing a positive electrode active material, wherein the positive electrode active material has A of 1.2 to 3.7 as defined by the following formula 1 when analyzed by X-ray diffraction (XRD). [Formula 1] A = {(peak area in the region where the diffraction angle 2θ is 37.1° to 37.9°) / (peak area in the region where the diffraction angle 2θ is 36.0° to 37.1°)} × 100 11. In claim 10, A method for manufacturing a positive electrode active material, wherein the first coating and the second coating are performed for 1 to 10 hours.

12. A positive electrode comprising a positive electrode active material according to any one of claims 1 to 9.

13. A lithium secondary battery comprising the positive electrode of claim 12.

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