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

Abstract

The present invention relates to a positive electrode active material, and a positive electrode and lithium secondary battery comprising same, the positive electrode active material comprising: a single-particle type lithium nickel-based oxide having 50-75 mol% of Ni and doped with a doping element M1; and a coating layer formed on the single particle-type lithium nickel-based oxide and including a coating element M2, wherein AONc+d defined by formula (1) is 3.5 to 4.2, R defined by formula (2) is 0.5 or less, and a weight ratio of the doping element M1 to the coating element M2 (M1 / M2) is 0.2 to 1.0.

Description

Cathode active material, cathode containing same, and lithium secondary battery The present invention relates to a cathode active material, a cathode including the same, and a lithium secondary battery, and more particularly, to a cathode active material capable of stably operating at 4.35 V or higher and realizing high energy density, and a cathode including the same and a lithium secondary battery. A lithium secondary battery is 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 intercalating and deintercalating lithium ions. Lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), lithium manganese oxide (LiMnO2 or LiMnO4, etc.), and lithium iron phosphate compound (LiFePO4) have been used as cathode active materials for lithium secondary batteries. Among these, lithium cobalt oxide has the advantages of high operating voltage and excellent capacity characteristics, but the high price of cobalt, which is the raw material, and its supply are unstable, making it difficult to commercially apply it to large-capacity batteries. Lithium nickel oxide has poor structural stability, making it difficult to achieve sufficient cycle life characteristics. Meanwhile, lithium manganese oxide has excellent stability but has the problem of poor capacity characteristics. Therefore, lithium composite transition metal oxides containing two or more transition metals have been developed to complement the problems of lithium transition metal oxides containing only Ni, Co, or Mn. 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 were generally in the form of spherical secondary particles formed by agglomeration of tens to hundreds of primary particles. However, in the case of lithium nickel cobalt manganese oxides formed in the form of secondary particles formed by agglomeration of many primary particles, there is a problem in that the primary particles are easily broken 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 particles are 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 causes problems in that the life characteristics are reduced. Meanwhile, in the electric vehicle field, cells with high energy density are required to extend the single-charge driving distance, and accordingly, cells using high-nickel NCM cathode active materials with a nickel content of 80 mol% or more, which have excellent capacity characteristics, are being developed as lithium secondary batteries for electric vehicles. However, when the nickel content in the cathode active material increases, the initial capacity characteristics are improved, but the highly reactive Ni is damaged when charge and discharge are repeated. +4 The problem is that the large amount of ions generated causes structural collapse of the cathode active material, which accelerates the deterioration of the cathode active material, reducing its lifespan and battery safety. This phenomenon becomes more severe as the operating voltage increases. Therefore, there is a need for the development of lithium secondary batteries with high energy density and excellent lifespan characteristics. The present invention is intended to solve the above problems, and to provide a cathode active material that can be stably driven at high voltage to realize high energy density and has excellent life characteristics, and a cathode and lithium secondary battery using the same. [1] The present invention comprises a Ni content of 50 mol% to 75 mol% and a doping element M. 1A single particle lithium nickel-based oxide doped with; and a coating element M formed on the single particle lithium nickel-based oxide 2 AON comprising a coating layer including and defined by the following formula (1) c+d is 3.5 to 4.2, and R defined by the following formula (2) is 0.5 or less, and the coating element M 2 The above doping element M for the weight of 1 Weight ratio of (M 1 / M 2 ) provides a positive electrode active material having a value of 0.2 to 1.0. Equation (1): AON c+d = {∑(M 1 Oxidation number of the element ×M 1 mole fraction of an element) + ∑(M 2 Oxidation number of the element ×M 2 mole fraction of an element) / (M 1 Elements and M 2 Sum of mole fractions of elements) Equation (2): R = | AON d - AON c | In the above equation (2), AON d is a doping element M defined by the following equation (2-1). 1 Average oxidation state of AON c is a coating element M defined by the following equation (2-2). 2 is the average oxidation number. Equation (2-1): AON d = ∑ (M 1 Oxidation number of the element × M 1 Mole fraction of element) / (M 1 Sum of mole fractions of elements) Equation (2-2): AON c = ∑ (M 2 Oxidation number of the element × M 2 Mole fraction of element) / (M 2 Sum of mole fractions of elements) [2] The present invention, in the above [1], the doping element M 1Provided is a cathode active material comprising at least one selected from the group consisting of Ti, Mg, Al, Zr, Y, Ba, B, Ca, Sr, W, Ta, Nb, and Mo. [3] The present invention, in the above [1] or [2], the doping element M 1 Provided is a cathode active material comprising two or more kinds selected from the group consisting of Ti, Mg, Al, Zr, Y, Ba, B, Ca, Sr, W, Ta, Nb, and Mo. [4] The present invention, in at least one of the above [1] to [3], the doping element M 1 A cathode active material is provided, which comprises at least one element selected from Y, Sr, Ti and Nb; and Zr. [5] The present invention, in at least one of the above [1] to [4], the coping element M 2 Provided is a cathode active material comprising at least one selected from the group consisting of Ti, Mg, Al, Zr, Y, Ba, Ca, Sr, W, Ta, Nb, and Mo. [6] The present invention, in at least one of the above [1] to [5], the coping element M 2 Provided is a cathode active material comprising two or more kinds selected from the group consisting of Ti, Mg, Al, Zr, Y, Ba, Ca, Sr, W, Ta, Nb, and Mo. [7] The present invention, in at least one of the above [1] to [6], the coping element M 2 Provides a cathode active material comprising Al and W. [8] The present invention relates to at least one of the above [1] to [7], wherein the average oxidation number AON of the doping element represented by the above formula (2-1) d A positive electrode active material having a value of 2.5 to 5.5 is provided. [9] The present invention, in at least one of the above [1] to [8], the average oxidation number AON of the coating element represented by the above formula (2-2) c A positive electrode active material having a value of 2.5 to 5.5 is provided.

[0010] The present invention provides a positive electrode active material in which R, defined by the above formula (2), is 0.01 to 0.30 in at least one of the above [1] to [9].

[0011] The present invention is characterized in that at least one of the above [1] to

[0010] is present, wherein the doping element M 1 A positive electrode active material is provided, which is included in an amount of 500 ppm to 10,000 ppm based on the total weight of the positive electrode active material.

[0012] The present invention, in at least one of the above [1] to

[0011] , the coating element M 2 A cathode active material is provided, which is included in an amount of 500 ppm to 10,000 ppm based on the total weight of the cathode active material.

[0013] The present invention provides a positive electrode active material, wherein in at least one of the above [1] to

[0012] , the single particle lithium nickel-based oxide is represented by the following [chemical formula 1]. [Chemical Formula 1] Li 1+x [Ni a Co b Mn c M 1 d ]O2 In the above [chemical formula 1], M1 includes at least one element selected from the group consisting of Ti, Mg, Al, Zr, Y, Ba, Ca, Sr, W, Ta, Nb, and Mo, and -0.1≤x≤0.1, 0.5≤a≤0.75, 0 <b<0.5, 0<c<0.5, 0<d≤0.2이다.

[0014] The present invention provides a positive electrode active material in which the average particle diameter of the nodules of the single-particle lithium nickel-based oxide is 0.8 µm to 4 µm, in at least one of the above [1] to

[0013] .

[0015] The present invention, in at least one of the above [1] to

[0014] , D of the positive electrode active material 50 This provides a positive electrode active material having a diameter of 3㎛ to 8㎛.

[0016] The present invention provides a positive electrode comprising a positive electrode active material according to at least one of the above [1] to

[0015] .

[0017] The present invention provides a lithium secondary battery including a positive electrode according to the above

[0016] .

[0018] The present invention provides a lithium secondary battery having a charge cut-off voltage of 4.35 V or higher, in the above

[0017] . The cathode active material according to the present invention includes a single particle lithium nickel oxide having a small contact area with the electrolyte, thereby minimizing side reactions with the electrolyte, thereby suppressing gas generation and reduction in lifespan due to side reactions with the electrolyte. In addition, since the cathode active material according to the present invention uses a lithium nickel oxide having a nickel content of 50 mol% to 75 mol%, it has high reactivity. +4 Since there are fewer ions, the structural stability of the positive electrode active material is improved, so that the positive electrode active material can be prevented from rapidly degrading even when driven at a high voltage of 4.35 V or higher. In addition, when the average oxidation number and content of the doping element and coating element are controlled within a specific range, such as in the positive electrode active material according to the present invention, the stability of the crystal structure and surface structure of the positive electrode active material is improved, thereby suppressing rapid degradation of the positive electrode active material when driven at a high voltage of 4.35 V or higher. Therefore, when the positive electrode active material according to the present invention is applied, it is possible to realize a secondary battery with excellent capacity characteristics and life characteristics because it can be driven stably at a high voltage of 4.35 V or higher. 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 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 to explain his or her own invention in the best way. In the present invention, “single particle type” means a particle composed of 30 or fewer nodules, and is a concept that includes a single particle composed of one nodule and a pseudo-single particle which is a composite of 2 to 30 nodules. The above “nodule” is a sub-particle unit that constitutes a single particle and a pseudo-single particle, and may be a single crystal without a crystalline grain boundary, or a polycrystal with no apparent grain boundary when observed under a magnification of 5,000 to 20,000 times using a scanning electron microscope. In the present invention, "secondary particle" refers to a particle formed by agglomeration of a plurality of primary particles, for example, tens to hundreds of primary particles. Specifically, the secondary particle may be an aggregate of 31 or more primary particles. In the present invention, “particle” is a concept including any one or all of a single particle, a pseudo-single particle, a primary particle, a nodule, and a secondary particle. In the present invention, the average particle diameter (D) of the nodules or primary particles mean) means the arithmetic mean value calculated after measuring the particle size of nodules or primary particles observed in a scanning electron microscope or an electron backscatter diffraction (EBSD) image. For example, the particle size of the nodules or primary particles can be measured by manufacturing an electrode using the positive electrode active material powder to be measured, cutting the electrode before rolling by ion milling (HITACHI IM-500, accelerating voltage 6 kV) to obtain a cross-section, and then measuring the number of primary particles on a scale of approximately 400±10 under the conditions of an accelerating voltage of 15 kV and a WD of 15 mm using an FE-SEM (JEOL JSM7900F). In the present invention, "average particle diameter D 50 "It refers to the particle size corresponding to 50% of the volume accumulation amount of the volume accumulation particle size distribution of the powder to be measured, and can be measured using the laser diffraction method. For example, after dispersing the powder to be measured 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 at an output of 60 W, obtaining a volume accumulation particle size distribution graph, and then calculating the particle size corresponding to 50% of the volume accumulation 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-mini II of BEL Japan. Hereinafter, the present invention will be described in more detail. positive electrode active material The cathode active material according to the present invention has a Ni content of 50 mol% to 75 mol% and at least one doping element M. 1A single particle lithium nickel-based oxide doped with; and at least one coating element M formed on the single particle lithium nickel-based oxide. 2 Includes a coating layer including . In the case of secondary particle-type lithium nickel-based oxides in which 31 to hundreds of primary particles are aggregated, the contact area with the electrolyte is large, and fine particles are generated due to particle breakage during the positive electrode rolling process, which causes many side reactions with the electrolyte, and gas is generated during the side reaction process. In contrast, single-particle lithium nickel-based oxides have a small number of nodules constituting the particles, which results in a small interparticle interface, resulting in a small contact area with the electrolyte, and high particle strength, which reduces particle breakage during rolling, resulting in less side reactions with the electrolyte compared to secondary particles, and accordingly, significantly less gas generation. Therefore, when single-particle lithium nickel-based oxides are applied as positive electrode active materials, superior life characteristics can be obtained compared to secondary particles. However, single-particle lithium nickel oxide particles have lower lithium mobility than conventional secondary-particle lithium nickel oxide particles due to longer intraparticle lithium migration paths and smaller internodular interfaces that serve as lithium ion migration paths, resulting in lower battery capacity and poor output characteristics. Therefore, high-voltage operation is required to realize high-capacity batteries. When the charge cut-off voltage of a lithium secondary battery using lithium nickel oxide is 4.3 V or lower, relatively stable performance can be achieved. However, when the charge cut-off voltage is 4.35 V or higher, side reactions with the electrolyte become severe, transition metal ions are eluted, and battery performance deteriorates rapidly. It is known that this performance deterioration becomes more severe when the temperature increases. In the past, to solve this problem, a method of reducing contact with the electrolyte by coating the surface of lithium nickel-based oxide with a metal oxide such as Al or boron has been used. However, since the coating layer is not electrically active, when a coating layer is formed on the surface of lithium nickel-based oxide, the resistance of the positive electrode active material increases, and the increase in resistance becomes more severe as the thickness of the coating layer increases. In particular, in the case of single-particle lithium nickel-based oxide, since the resistance is basically high, when a conventional coating layer is applied to the surface, the problem of output reduction due to the increased resistance occurs more seriously. The present inventors have conducted repeated research to solve the above problems and, as a result, have found that by applying doping and coating to a single-particle lithium nickel-based oxide having a nickel content of 50 mol% to 75 mol%, and adjusting the average oxidation numbers of the doping element and the coating element to satisfy the conditions of the following equations (1) and (2), and adjusting the content ratio of the doping element to the coating element to satisfy 0.2 to 1, the crystal structure and surface structure of the positive electrode active material are stably maintained even under a high voltage of 4.35 V or higher, thereby realizing excellent capacity characteristics and life characteristics, thereby completing the present invention. The positive electrode active material according to the present invention has an oxidation number AON defined by the following formula (1): C+d It is 3.5 to 4.2, preferably 3.5 to 4.0. Equation (1): AON c+d = {∑(M 1 Oxidation number of the element × M 1 mole fraction of an element) + ∑(M 2 Oxidation number of the element × M 2 mole fraction of an element) / (M 1 Elements and M 2 Sum of mole fractions of elements) M 1 Element and / or M 2In the case where multiple different elements are used as elements, the average oxidation number is the sum of the oxidation number of each element and the mole fraction of each element, divided by the sum of the mole fractions of the doping element and the coating element. For example, M 1 Elements a and b are used as elements, and M 2 If c and d elements are used as elements, the average oxidation number of the doping and coating elements is {(a Oxidation number of element × mole fraction of element a) + (oxidation number of element b × mole fraction of element b) + (c It is calculated as {(oxidation number of element × mole fraction of c element) + (oxidation number of d element × mole fraction of d element)} / (mole fraction of element a + mole fraction of element b + mole fraction of element c + mole fraction of element d). Meanwhile, M 1 Elements and M 2 When an element has two or more oxidation states, the oxidation number is calculated as the oxidation number at which each element is in its most stable state. For example, the oxidation number of Al is calculated as 3, the oxidation number of Mg is calculated as 2, the oxidation number of Ti is calculated as 4, the oxidation number of Nb is calculated as 5, the oxidation number of Sr is calculated as 2, the oxidation number of Zr is calculated as 4, the oxidation number of W is calculated as 6, the oxidation number of Y is calculated as 3, and the oxidation number of B is calculated as 3. Meanwhile, in the above equation (1), M 1 Mole fraction of elements and M 2 The mole fraction of an element was calculated by dividing the weight ratio (unit: ppm) of each element in the positive electrode active material by the atomic weight of each element, i.e., the weight ratio of each element (ppm) / the atomic weight of each element. In this case, M in the positive electrode active material 1 and M 2 The weight ratio of elements can be measured using the Inductively Coupled Plasma (ICP) method. According to the research of the present inventors, the above AON c+dWhen a cathode active material satisfying the range of 3.5 to 4.2 is applied, the high-voltage durability is significantly improved while minimizing the deterioration of the electrochemical properties of the secondary battery. In contrast, the AON of the cathode active material c+d When the value is less than 3.5 or more than 4.2, the deterioration of the positive electrode active material is accelerated during high voltage operation, resulting in a decrease in capacity and an increase in resistance. The positive electrode active material according to the present invention has an R value defined by the following formula (2) of 0.50 or less, preferably 0.01 to 0.50, and more preferably 0.01 to 0.30. Equation (2): R = | AON d - AON c | In the above equation (2), AON d is a doping element M defined by the following equation (2-1). 1 is the average oxidation number of , and AON c is a coating element M defined by the following equation (2-2). 2 is the average oxidation number. Equation (2-1): AON d = ∑ (M 1 Oxidation number of the element × M 1 Mole fraction of element) / (M 1 Sum of mole fractions of elements) Equation (2-2): AON c = ∑ (M 2 Oxidation number of the element × M 2 Mole fraction of element) / (M 2 Sum of mole fractions of elements) In the above equations (2-1) and (2-2), M 1 and M 2 The oxidation number and mole fraction of the elements are the same as those described in Equation (1). That is, the oxidation number is the oxidation number at which each element is in its most stable state, and the mole fraction is the value obtained by dividing the weight ratio (unit: ppm) of each element in the positive electrode active material by the atomic weight of each element. When R, represented by Equation (2), satisfies the above range, the crystal structure and surface structure of the positive electrode active material can be stably maintained, so that the degradation of the active material is suppressed during high voltage operation, and the resistance characteristics and high temperature life characteristics are improved. Doping element M 1 The average oxidation number AON d and coating element M 2 The average oxidation number AON c When the difference R exceeds 0.5, the resistance at the interface between the lithium nickel oxide and the coating layer increases due to the difference in the average oxidation number of the doping element and the coating element, and the life characteristics may be deteriorated due to the collapse of the crystal structure or surface structure when driven at high voltage. The above AON c+d , AON c and AON d Since AON is a value that varies depending on the type and content of doping elements and coating elements, it is a method of controlling the type and content of doping elements and coating elements when manufacturing positive electrode active materials. c+d , AON c and AON d You can adjust it to the desired range. The positive electrode active material according to the present invention comprises the coating element M 2 The above doping element M for the weight of 1 Weight ratio of (M 1 / M 2 ) is 0.2 to 1.0, preferably 0.3 to 1.0, more preferably 0.5 to 1.0. M 1 / M 2 If it exceeds 1.0, the capacity of the positive electrode active material decreases, the surface stability of the positive electrode active material deteriorates when driven at high voltage, and the amount of gas generated increases. If it is less than 0.2, the resistance of the positive electrode active material increases, and the crystal structure collapses when driven at high voltage, which may cause rapid deterioration of the active material. Meanwhile, the above doping element M 1It may include elements having oxidation numbers of 2 to 6. Specifically, the doping element M 1 It may be at least one selected from the group consisting of Ti, Mg, Al, Zr, Y, Ba, Ca, Sr, W, Ta, Nb, and Mo, preferably at least two selected from the group consisting of Ti, Mg, Al, Zr, Y, Ba, Ca, Sr, W, Ta, Nb, and Mo, more preferably at least two selected from the group consisting of Ti, Mg, Al, Zr, Sr, Nb, and Y. Even more preferably, the doping element M 1 It may include one or more elements selected from Y, Sr, Ti and Nb and Zr. More preferably, the doping element M 1 may include Zr and Y. The doping element M 1 In this case of Zr and Y, the molar ratio of Y to Zr (Y / Zr) may be 0.1 or more and 5 or less, preferably 0.2 or more and 2 or less, and more preferably 0.3 or more and 0.8 or less. The doping element M based on the total weight of the positive electrode active material 1 The total content of It may be 500 ppm to 10,000 ppm, preferably 1000 ppm to 10,000 ppm, more preferably 1500 ppm to 8000 ppm. Doping element M 1 When the content of the doping element satisfies the above range, the high-voltage durability can be improved while minimizing the capacity degradation of the positive electrode active material. If the content of the doping element is too high, the amount of transition metal may be reduced, which may negatively affect the capacity, and if it is too low, the effect of improving the high-voltage durability is reduced. Meanwhile, in the present invention, the doping element M 1 The average oxidation number AON of doping elements is defined by the following equation (2-1). dIt is preferable that the AON is 2.5 or more, 3.0 or more, 3.3 or more, 3.4 or more, or 3.5 or more, and it is preferable that it is 5.5 or less, 5.0 or less, 4.0 or less, or 3.9 or less. Specifically, the AON c can be 2.5 to 5.5, 3.0 to 5.0, 3.3 to 4.0, 3.4 to 3.9, or 3.5 to 3.9. Formula (2-1): AON d = ∑ (M 1 Oxidation number of the element × M 1 Mole fraction of element) / (M 1 Sum of mole fractions of elements) In the above equation (2-1), M 1 The oxidation number and mole fraction of the elements have the same meaning as described in equation (1). Doping element M 1 When the average oxidation number satisfies the above range, the crystal structure stability of the positive electrode active material is increased, and the effect of suppressing the degradation of the active material when driven at high voltage can be obtained. Meanwhile, the above coating element M 2 may include elements having oxidation numbers of 2 to 6. Specifically, the coating element M 2 It may include at least one selected from the group consisting of Ti, Mg, Al, Zr, Y, Ba, Ca, Sr, W, Ta, Nb, and Mo, preferably it may include at least two selected from the group consisting of Ti, Mg, Al, Zr, Y, Ba, Ca, Sr, W, Ta, Nb, and Mo, more preferably it may include at least two elements selected from the group consisting of Ti, Mg, Al, Zr, Y, and W. Even more preferably, the coating element coping element M 2 may contain Al and W. The coping element M based on the total weight of the positive electrode active material 2 The total content of 500 to 10,000 ppm, preferably 1,000 to 10,000 ppm, more preferably 1500 to 8000 ppm. Coating element M 2 When the content satisfies the above range, the effect of improving high-voltage durability can be obtained while minimizing the increase in resistance. If the content of the coating element is too high, the insertion / de-insertion of lithium ions may be suppressed, which may increase the resistance, and if it is too low, the effect of suppressing transition metal dissolution during high-voltage operation is reduced. Meanwhile, in the present invention, the coating elements are defined by the following formula (2-2) as the average oxidation number AON of the coating elements. c It is preferable that the AON is 2.5 or more, 3.0 or more, 3.3 or more, 3.4 or more, or 3.5 or more, and it is preferable that it is 5.5 or less, 5.0 or less, 4.0 or less, or 3.9 or less. Specifically, the AON c may be 2.5 to 5.5, 3.0 to 5.0, 3.3 to 4.0, or 3.4 to 3.9. Equation (2-2): AON c = ∑ (M 2 Oxidation number of the element × M 2 Mole fraction of element) / (M 2 Sum of mole fractions of elements) In the above equation (2-2), M 2 The oxidation numbers and mole fractions of elements have the same meaning as described in equation (1). Coating element M 2 When the average oxidation number satisfies the above range, the surface structural stability of the positive electrode active material is improved, and contact between electrolytes is suppressed, thereby obtaining the effect of suppressing degradation of the active material during high voltage operation. The positive electrode active material according to the present invention has a Ni content of 50 mol% to 75 mol%, preferably 50 mol% to 70 mol%, and a doping element M 1 It comprises a single particle lithium nickel oxide doped with doping element M. 1 is the same as described above. When a single particle lithium nickel oxide having a relatively low nickel content as described above is used as a cathode active material, side reactions with the electrolyte are suppressed under high voltage conditions, gas generation is reduced, and excellent life characteristics can be realized. In the case of single particle lithium nickel oxides with relatively low nickel content, the structural stability at high voltage is higher than that of lithium nickel oxides with high nickel content or secondary particle form, so that the degradation of life characteristics during high voltage operation can be minimized. Specifically, the higher the nickel content in the lithium nickel oxide, the more reactive Ni becomes. +4 As the number of ions increases, the structural stability of the positive electrode active material decreases during charge and discharge, causing positive electrode degradation to occur rapidly. This phenomenon becomes more severe during high voltage operation. Therefore, in the present invention, by applying a lithium nickel-based oxide with a low Ni content of 75 mol% or less, it is possible to suppress the reduction in lifespan due to active material degradation during high voltage operation. However, if the Ni content is too low, the capacity characteristics deteriorate, so the Ni content of the lithium nickel-based oxide is preferably about 50 mol% to 75 mol%. Specifically, the single particle lithium nickel-based oxide may be a lithium transition metal oxide containing nickel, manganese, and cobalt, and may be, for example, represented by the following [chemical formula 1]. [Chemical Formula 1] Li 1+x [Ni a Co b Mn c M 1 d ]O2 In the above [chemical formula 1], M 1 It may contain one or more elements selected from the group consisting of Ti, Mg, Al, Zr, Y, Ba, Ca, Sr, W, Ta, Nb, and Mo. M 1When the element is included, the structural stability of lithium nickel-based oxide particles is improved, so that excellent life characteristics can be realized when driving at high voltage. Preferably, the M 1 The element may include at least one selected from the group consisting of Ti, Mg, Al, Zr and Y, and more preferably, at least two selected from the group consisting of Ti, Mg, Al, Zr and Y. The above 1+x represents the lithium molar ratio in the lithium nickel-based oxide, and may be -0.1≤x≤0.1, 0≤x≤0.1, or 0≤x≤0.07. When 1+x satisfies the above range, a stable layered crystal structure can be formed. The above a represents the molar ratio of nickel among the total metals excluding lithium in the lithium nickel-based oxide, and may be 0.5≤a≤0.75, 0.55≤a≤0.75, or 0.55≤a≤0.70. When a satisfies the above range, it can be stably operated at high voltage and achieve high capacity. The above b represents the molar ratio of cobalt among all metals excluding lithium in the lithium nickel oxide, and is 0. <b<0.5, 0.05≤b≤0.25 또는 0.1≤b≤0.30일 수 있다. The above c represents the molar ratio of manganese among all metals excluding lithium in lithium nickel oxide, and is 0. <c<0.5, 0.05≤c≤0.25 또는 0.1≤c≤0.30일 수 있다. The above d is M of all metals except lithium in lithium nickel oxide. 1 It represents the molar ratio of elements, 0≤d≤0.2, 0≤d≤0.1 or 0 <d≤0.1일 수 있다. M 1 When the molar ratio of the elements satisfies the above range, both the structural stability and capacity of the positive electrode active material can be excellent. Meanwhile, it is preferred that the single particle lithium nickel-based oxide comprises no more than 30 nodules, preferably 1 to 25 nodules, and more preferably 1 to 15 nodules. If the number of nodules constituting the lithium nickel-based oxide exceeds 30, particle breakage increases during electrode manufacturing, and internal cracks occur more frequently due to volume expansion / contraction of the nodules during charge / discharge, which may deteriorate the effect of improving high-temperature life characteristics and high-temperature storage characteristics. Meanwhile, the average particle size of the nodules may be 0.8 µm to 4.0 µm, preferably 0.8 µm to 3 µm, and more preferably 1.0 µm to 3.0 µm. When the average particle size of the nodules satisfies the above range, particle breakage is minimized during electrode manufacturing, and resistance increase can be more effectively suppressed. At this time, the average particle size of the nodules refers to a value obtained by measuring the particle sizes of nodules observed in SEM images obtained by analyzing the positive electrode active material powder with a scanning electron microscope, and then calculating the arithmetic mean of the measured values. The cathode active material according to the present invention is formed on the single particle lithium nickel oxide, and the coating element M 2 Includes a coating layer including . Preferably, the coating layer is Li-M 2 -O may include a solid solution. The above M 2 is the same as described above. That is, the coating element M 2 It may include one or more or two or more elements selected from the group consisting of Ti, Mg, Al, Zr, Y, Ba, B, Ca, Sr, W, Ta, Nb, and Mo, and may include two or more elements selected from the group consisting of Ti, Mg, Al, Zr, Y, and W. More preferably, the coating element coping element M 2 It may include Al and W. When the above elements are included, side reactions with the electrolyte on the surface of the positive electrode active material particles can be effectively suppressed. Coating element M 2 There are two elements (for convenience, M 2a , M 2b In case of including (called) the above M 2a The average oxidation number is 2 to 3, and the above M 2b The average oxidation number may be 4 to 6. The above M 2b M for 2a Molar ratio (M 2a / M 2b ) may be 1 or more and 10 or less, preferably 2 or more and 6 or less, and more preferably 2.5 or more and 4 or less. The above Li-M 2 -When the -O solution is Li-Al-WO, the molar ratio of Al to W (Al / W) may be 1 or more and 10 or less, preferably 2 or more and 6 or less, and more preferably 2.5 or more and 4 or less. When the above range is satisfied, HF products due to side reactions of lithium salts in the electrolyte can be effectively suppressed, and battery capacity characteristics and resistance characteristics can be improved. Meanwhile, the positive electrode active material is D 50 It may be 3.0㎛ to 8.0㎛, preferably 3.0㎛ to 7.5㎛. More preferably, it is preferably about 3.5㎛ to 7.5㎛. D of lithium nickel-based oxide 50 If this is too small, the processability during electrode manufacturing may be poor, the electrolyte impregnation may be poor, and the electrochemical properties may increase. 50 If this is too large, there is a problem that the resistance increases and the output characteristics deteriorate. In addition, the above positive electrode active material is D 50 The single particle size ratio, which is the ratio of the average particle diameter of the nodules to the single particle size ratio, may be 0.1 to 1, 0.2 to 0.8, 0.3 to 0.9, or 0.4 to 0.8. When the single particle size ratio of the positive electrode active material satisfies the above range, the life characteristics and gas generation suppression effect at high temperature and / or high voltage are further improved. The positive electrode active material according to the present invention has a BET specific surface area of ​​0.3 m 2 / g to 1.5m 2 / g, preferably 0.4m 2 / g to 1.3m 2 / g, more preferably 0.5m 2 / g to 1.0m 2 / g. When the BET specific surface area of ​​the positive electrode active material satisfies the above range, the capacity characteristics and life characteristics are more excellent. If the BET specific surface area is too small, the reaction area with the electrolyte is insufficient, making it difficult to achieve sufficient capacity. If the BET specific surface area is too large, the adhesive strength may be reduced during electrode manufacturing or the side reaction with the electrolyte may be accelerated during electrode operation, making it difficult to secure life characteristics. Method for manufacturing positive electrode active material Next, a method for manufacturing a positive electrode active material according to the present invention will be described. The method for manufacturing a cathode active material according to the present invention comprises: (1) a transition metal precursor, a lithium raw material, and M 1 A step of producing a single-particle lithium nickel-based oxide by mixing and calcining a doping raw material containing an element, and (2) the single-particle lithium nickel-based oxide and M 2 It includes a step of mixing a coating raw material containing an element and performing heat treatment to form a coating layer on the surface of the single particle lithium nickel-based oxide. At this time, the doping raw material and coating raw material satisfy equations (1) and (2), and the coating element M 2 Doping element M for 1 Weight ratio of (M 1 / M 2 ) is injected in an amount such that the ratio is 0.2 to 1.0. First, a transition metal precursor, a lithium raw material, and a doping element M having a nickel content of 50 mol% to 75 mol% among all metals excluding lithium 1A doping raw material including (wherein, M1 is at least one selected from the group consisting of Ti, Mg, Al, Zr, Y, Ba, B, Ca, Zr, Sr, W, Ta, Nb, and Mo) is mixed and calcined to manufacture a single-particle lithium nickel-based oxide including 30 or fewer nodules. The transition metal precursor may be a precursor for a cathode active material commonly used in the relevant technical field. For example, the transition metal precursor may be purchased and used as a commercially available precursor such as nickel-cobalt-manganese hydroxide or nickel-cobalt-manganese oxide, or may be manufactured and used according to a precursor manufacturing method known in the relevant technical field such as coprecipitation or spray pyrolysis. The lithium raw material may include lithium-containing sulfate, nitrate, acetate, carbonate, oxalate, citrate, halide, hydroxide, or oxyhydroxide, and is not particularly limited as long as it can be dissolved in water. Specifically, the lithium raw material may 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 may be used. As the above doping raw material, an oxide, hydroxide, sulfide, oxyhydroxide, halide or mixture thereof containing one or more elements selected from the group consisting of Ti, Mg, Al, Zr, Y, Ba, B, Ca, Zr, Sr, W, Ta, Nb, and Mo may be used. The above transition metal precursor, lithium source material, and doping source material can be mixed using either solid-phase mixing or liquid-phase mixing. When mixing the components through solid-phase mixing, the firing process can be performed without a separate drying process. When mixing the components through liquid-phase mixing, the mixed components are spray-dried before the firing process. Thereafter, the mixture may be subjected to a calcination process. The calcination process may be performed in an air or oxygen atmosphere. The calcination process is performed at a temperature and time suitable for forming lithium nickel-based oxide in the form of single particles. The calcination temperature may vary depending on the nickel content, and may be performed at, for example, a temperature of 700°C to 1000°C, 750°C to 1000°C, or 850°C to 980°C, but is not limited thereto. The above firing time may be, for example, 10 to 30 hours, 15 to 30 hours, or 20 to 28 hours, but is not limited thereto. Next, the lithium nickel oxide is coated with a coating element M 2 A coating raw material including lithium composite transition metal oxide is mixed and heat-treated to form a coating layer on the surface of the lithium composite transition metal oxide particle. The above coating layer can be formed using a method known in the art, for example, a wet coating method, a dry coating method, a plasma coating method, or ALD (Atomic Layer Deposition). The above wet coating method can be performed, for example, by adding lithium nickel oxide and a coating raw material to an appropriate solvent such as ethanol, water, methanol, acetone, etc., and mixing until the solvent disappears. The above dry coating method is a method of mixing lithium nickel oxide and coating raw material in a solid state without a solvent, and for example, a grinder mixing method or a mechanofusion method can be used. The above coating raw material may be an oxide, hydroxide, oxyhydroxide, carbonate, sulfate, halide, sulfide, acetate, carboxylate or a combination thereof containing one or more elements selected from the group consisting of Ti, Mg, Al, Zr, Y, Ba, B, Ca, Zr, Sr, W, Ta, Nb, and Mo. The above heat treatment temperature is M 2 Depending on the type of element, the heat treatment can be appropriately adjusted, and for example, the heat treatment can be performed at a temperature of 200°C to 900°C, 250°C to 800°C, or 300°C to 700°C, but is not limited thereto. The heat treatment can be performed for 2 hours to 25 hours, 5 hours to 20 hours, or 8 hours to 18 hours, but is not limited thereto. anode Next, the anode of the present invention will be described. The positive electrode according to the present invention comprises the positive electrode active material according to the present invention described above, and may further comprise a positive electrode conductive material and a positive electrode binder, if necessary. Specifically, the positive electrode comprises a positive electrode current collector, a positive electrode active material layer formed on at least one surface of the positive electrode current collector, and the positive electrode active material layer comprises a positive electrode active material, a positive electrode conductive material, and a positive electrode binder. Meanwhile, since the positive electrode active material is the same as described above, a detailed description thereof will be omitted. The positive electrode current collector is not particularly limited as long as it is conductive and does not cause a chemical change in the battery, and for example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, etc. may be used. In addition, the positive electrode current collector may typically have a thickness of 3 to 500 μm, and fine unevenness may be formed on the surface of the positive electrode 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, sheet, foil, net, porous body, foam, or non-woven fabric. Meanwhile, the positive electrode active material may be included in an amount of 93 wt% to 99 wt%, preferably 95 wt% to 98 wt%, and more preferably 95 wt% to 97 wt%, based on the total weight of the positive electrode active material layer, i.e., the total amount of the positive electrode active material, the positive electrode conductive material, and the positive electrode binder. When the content of the positive electrode active material satisfies the above range, a high energy density can be realized. Next, the positive electrode conductive material is used to provide conductivity to the positive electrode, and in the battery to be formed, as long as it does not cause a chemical change and has electronic conductivity, it can be used without any particular limitation. Specific examples include graphite such as natural graphite or artificial graphite; carbon-based materials such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, summer black, carbon fiber, carbon nanotube, etc.; metal powder or metal fiber such as copper, nickel, aluminum, silver, etc.; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives, etc., and one of these may be used alone or a mixture of two or more may be used. The above-mentioned positive electrode conductive material may be included in an amount of 0.1 to 10 wt%, preferably 0.5 to 8 wt%, and more preferably 1 to 5 wt%, based on the total weight of the positive electrode active material layer. Next, the positive electrode binder serves to improve adhesion between positive electrode active material particles and adhesion between the positive electrode active material and the positive electrode current collector. Specific examples thereof include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer rubber (EPDM rubber), sulfonated-EPDM, styrene butadiene rubber (SBR), fluororubber, or various copolymers thereof, and one of these may be used alone or a mixture of two or more thereof may be used. The above positive electrode binder may be included in an amount of 0.5 wt% to 5 wt%, preferably 1 wt% to 4 wt%, and more preferably 1 wt% to 3 wt%, based on the total weight of the positive electrode active material layer. The positive electrode can be manufactured according to a conventional positive electrode manufacturing method. For example, the positive electrode can be manufactured by mixing a positive electrode active material, a positive electrode binder, and / or a positive electrode conductive material in a solvent to manufacture a positive electrode slurry, applying the positive electrode slurry onto a positive electrode current collector, and then drying and rolling the resulting film, or by casting the positive electrode slurry onto a separate support, and then peeling the resulting film from the support and laminating the resulting film onto a positive electrode current collector. Meanwhile, solvents commonly used in the art may be used as the solvent for the positive electrode slurry, and examples thereof include dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, and water, which may be used alone or in combination of two or more. The amount of the solvent used is sufficient to dissolve or disperse the positive electrode active material, conductive material, and binder in consideration of the coating thickness and manufacturing yield of the slurry, and to have a viscosity that can exhibit excellent thickness uniformity when applied thereafter for manufacturing the positive electrode. cathode A lithium secondary battery according to the present invention comprises an anode comprising a negative electrode active material, a negative electrode conductive material, and a negative electrode binder. Specifically, the negative electrode comprises a negative electrode current collector, and a negative electrode active material layer formed on at least one surface of the negative electrode current collector, wherein the negative electrode active material layer comprises a negative electrode active material, a negative electrode conductive material, and a negative electrode binder. The negative electrode current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery, and for example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., aluminum-cadmium alloy, etc. can be used. In addition, the negative electrode current collector can typically have a thickness of 3 to 500 ㎛, and like the positive electrode current collector, fine unevenness can be formed on the surface of the current collector to strengthen the bonding strength of the negative electrode 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. As the negative electrode active material, a compound capable of reversible intercalation and deintercalation of lithium may be used. Specific examples include carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber, and amorphous carbon; metallic compounds capable of alloying with lithium such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloy, Sn alloy, or Al alloy; SiO β (0 <β< 2), metal oxides capable of doping and dedoping lithium, such as SnO2, vanadium oxide, and lithium vanadium oxide; or composites containing the above metal 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 may be used. Meanwhile, both low-crystalline carbon and high-crystalline carbon can be used as the carbonaceous material. Representative examples of low-crystalline carbon include soft carbon and hard carbon, and representative examples of high-crystalline carbon include amorphous, plate-like, flaky, spherical or fibrous natural or artificial graphite, Kish graphite, pyrolytic carbon, mesophase pitch-based carbon fiber, meso-carbon microbeads, mesophase pitches, and high-temperature calcined carbon such as petroleum or coal tar pitch derived cokes. Preferably, the negative electrode active material may be composed of a carbon-based negative electrode active material, and at this time, the carbon-based negative electrode active material may include, for example, natural graphite, artificial graphite, graphitized carbon fiber, amorphous carbon, soft carbon, hard carbon, or a combination thereof. More preferably, the carbon-based negative electrode active material may include natural graphite and artificial graphite. The above carbon-based negative electrode active material has an average particle diameter D 50 This may be 2㎛ to 30㎛, preferably 5㎛ to 30㎛. The above negative active material may be included in an amount of 80 wt% to 98 wt%, preferably 90 wt% to 98 wt%, and more preferably 93 wt% to 98 wt%, based on the total weight of the negative active material layer. When the content of the negative active material satisfies the above range, excellent energy density can be achieved. Next, the negative electrode conductive material is used to provide conductivity to the negative electrode, and in the battery to be constructed, as long as it does not cause a chemical change and has electronic conductivity, it can be used without any particular limitation. Specific examples include graphite such as natural graphite or artificial graphite; carbon-based materials such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, summer black, carbon fiber, and carbon nanotube; metal powder or metal fiber such as copper, nickel, aluminum, and silver; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; 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 above negative electrode conductive material may be included in an amount of typically 0.1 to 10 wt%, preferably 0.5 to 8 wt%, and more preferably 1 to 5 wt%, based on the total weight of the negative electrode active material layer. The above negative electrode binder serves to improve adhesion between negative electrode active material particles and adhesion between the negative electrode active material and the negative electrode current collector. Specific examples thereof include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer rubber (EPDM rubber), sulfonated-EPDM, styrene-butadiene rubber (SBR), fluororubber, or various copolymers thereof, and one of these may be used alone or a mixture of two or more thereof. The above negative electrode binder may be included in an amount of 1 to 10 wt%, preferably 1 to 8 wt%, and more preferably 1 to 5 wt%, based on the total weight of the positive electrode active material layer. Meanwhile, in the lithium secondary battery according to the present invention, the negative electrode active material layer may have a single-layer structure or a multi-layer structure of two or more layers. For example, the negative electrode may include a first negative electrode active material layer formed on at least one surface of a negative electrode current collector and including a first negative electrode active material; and a second negative electrode active material layer formed on the first negative electrode active material layer and including a second negative electrode active material. At this time, the first negative electrode active material and the second negative electrode active material may be made of a carbon-based negative electrode active material, and may be, for example, natural graphite, artificial graphite, or a combination thereof. Meanwhile, when the negative electrode active material layer is a multilayer structure composed of two or more layers, each layer may have different types and / or contents of the negative electrode active material, binder, and / or conductive material. For example, the weight ratio of natural graphite to the total weight of the negative electrode active material in the first negative electrode active material layer (lower layer) may be formed to be higher than the weight ratio of natural graphite to the total weight of the negative electrode active material in the second negative electrode active material layer (upper layer), and the weight ratio of artificial graphite to the total weight of the negative electrode active material in the second negative electrode active material layer may be formed to be higher than the weight ratio of artificial graphite to the total weight of the negative electrode active material in the first negative electrode active material layer. Alternatively, the weight ratio of the conductive material to the total weight of the second negative electrode active material layer (upper layer) may be formed to be higher than the weight ratio of the conductive material to the total weight of the first negative electrode active material layer (upper layer). By forming the negative active material layer in a multilayer structure in this way and varying the composition of each layer, the performance characteristics of the battery, such as rapid charging performance and output characteristics, can be further improved. The above negative electrode can be manufactured according to a conventional negative electrode manufacturing method. For example, the negative electrode can be manufactured by mixing a negative electrode active material, a negative electrode binder, and / or a negative electrode conductive material in a solvent to manufacture a negative electrode slurry, applying the negative electrode slurry onto a negative electrode current collector, and then drying and rolling, or by casting the negative electrode slurry onto a separate support, peeling the support, and laminating the resulting film onto a negative electrode current collector. Meanwhile, solvents commonly used in the art may be used as solvents for the negative electrode slurry, and examples thereof include dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, and water, which may be used alone or in combination of two or more. The amount of the solvent used is sufficient to dissolve or disperse the negative electrode active material, conductive material, and binder, taking into account the coating thickness and manufacturing yield of the slurry, and to have a viscosity that can exhibit excellent thickness uniformity when applied thereafter for manufacturing the positive electrode. electrolyte The electrolyte may include an organic solvent and a lithium salt. The organic solvent may be used without any particular limitation as long as it can serve as a medium through which ions involved in the electrochemical reaction of the battery can move. 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; 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 is a C2 to C20 linear, branched, or cyclic hydrocarbon group, and may include a double-bonded aromatic ring or an ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; or sulfolanes can be used. 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 linear carbonate compound having low viscosity (e.g., ethyl methyl carbonate, dimethyl carbonate, or diethyl carbonate, etc.) is more preferable. The lithium salt may be used without any particular limitation as long as it is a compound capable of providing lithium ions used in a lithium secondary battery. Specifically, the lithium salt may be LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAl04, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2. LiCl, LiI, or LiB(C2O4)2. The concentration of the lithium salt is preferably within the range of 0.1 to 3.0M, preferably 0.1 to 2.0M, and more preferably 0.5 to 1.5M. 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 additionally include additives for the purposes of improving the life characteristics of the battery, suppressing battery capacity reduction, and improving the discharge capacity of the battery. For example, the additives include various additives used in the art, such as fluoroethylene carbonate (FEC), vinylene carbonate (VC), vinylethylene carbonate (VEC), ethylene sulfate (ESa), lithium difluorophosphate (LiPO2F2), lithium bisoxalato borate (LiBOB), lithium tetrafluoroborate (LiBF4), lithium difluorooxalato borate (LiDFOB), lithium difluorobisoxalatophosphate (LiDFBP), lithium tetrafluorooxalato phosphate (LiTFOP), lithium methylsulfate (LiMS), lithium ethylsulfate (LiES), propanesultone (PS), propenesultone (PRS), succinonitrile (SN), adiponitrile (AND), 1,3,6-hexanetricarbonitrile (HTCN), 1,4-dicyano-2-butene (DCB), fluorobenzene (FB), Ethyldi(pro-2-yl-1-yl)phosphate (EDP), 5-methyl-5-propazyloxylcarbonyl-1,3-dioxane-2-one (MPOD), etc. can be used alone or in combination, but are not limited thereto. The above additives can be included in an amount of 0.1 to 10 wt%, preferably 0.1 to 5 wt%, based on the total weight of the electrolyte. separator The lithium secondary battery according to the present invention may further include a separator between the positive electrode and the negative electrode, if necessary. The separator separates the negative electrode and the positive electrode and provides a passage for lithium ions to move. Any separator commonly used as a separator in lithium secondary batteries may be used without particular limitation. In particular, a separator having low resistance to electrolyte ion movement and excellent electrolyte moisture absorption capacity is preferable. 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, may 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. may also be used. Additionally, a coated separator containing ceramic components or polymeric materials may be used to secure heat resistance or mechanical strength, and may optionally be used in a single-layer or multi-layer structure. Meanwhile, it is preferable that the lithium secondary battery has a charge cut-off voltage of 4.35 V or higher, preferably 4.35 V to 5 V, and more preferably 4.35 V to 4.5 V. When the charge cut-off satisfies the above range, a high energy density can be realized. The energy density of a lithium secondary battery is affected not only by the capacity of the active material used but also by the operating voltage range. In particular, when lithium nickel cobalt manganese oxide is used as the positive electrode active material, a higher capacity can be realized as the operating voltage increases. However, there is a problem that when the operating voltage increases, side reactions with the electrolyte increase during charge and discharge, and the structural collapse of the positive electrode active material occurs rapidly, resulting in a rapid deterioration of the life characteristics. This problem is more prominent in high-nickel lithium nickel cobalt manganese oxides with a high nickel content. Therefore, in the past, when lithium nickel cobalt manganese oxides were used as the positive electrode active material, it was generally used at an operating voltage of 2.0 V to 4.3 V. However, in the present invention, by applying a cathode active material in which a single particle type lithium nickel oxide having a Ni content of 50 mol to 75 mol% or less is doped and coated to satisfy specific conditions, excellent life characteristics can be maintained even when driven at a high voltage having a charge cut-off voltage of 4.35 V or higher. The lithium secondary battery according to the present invention can be usefully applied to portable devices such as mobile phones, laptop computers, and digital cameras, as well as electric vehicles such as hybrid electric vehicles (HEVs). The lithium secondary battery according to the present invention can be operated at high voltage to achieve high energy density, and has excellent safety in the event of thermal runaway, making it particularly useful in the electric vehicle field. According to another embodiment of the present invention, a battery module including a lithium secondary battery according to the present invention 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, such as 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 them. However, the present invention may be implemented in various different forms and is not limited to the embodiments described herein. Example 1 Transition metal hydroxide Ni 0.6 Co 0.1 Mn 0.3 (OH)2, Li2CO3 as a lithium-containing raw material, and ZrO2 and Y2O3 as doping raw materials were mixed in amounts such that the contents of Zr and Y were 2800 ppm and 1400 ppm, respectively. After calcining the above mixture at 940°C for 20 hours, the calcined product was mixed with ultrapure water in a weight ratio of 1:1, washed for 20 minutes, and filtered using a depressurized filter. After filtration, drying was performed at 130°C under vacuum conditions to produce a single-particle lithium nickel-based oxide doped with Zr and Y. The above single particle lithium nickel oxide and coating raw materials Al2O3 and WO3 were mixed in amounts such that the contents of Al and W were 1400 ppm and 2900 ppm, respectively. Afterwards, the cathode active material (D) was formed with a coating layer by heat treatment at 400°C for 15 hours. 50 =3.8㎛) was manufactured. The cathode active material manufactured above: cathode conductive material: PVDF binder were mixed in a weight ratio of 95:2:3 in N-methylpyrrolidone to manufacture cathode slurry. At this time, carbon nanotubes were used as the cathode conductive material. The positive electrode slurry was applied onto an aluminum current collector sheet, dried, and then rolled to manufacture a positive electrode. An electrode assembly was manufactured by interposing a separator between the positive electrode and the lithium metal negative electrode manufactured as described above, and the electrode assembly was inserted into a battery case, and then an electrolyte was injected to manufacture a lithium secondary battery cell. Example 2 A lithium secondary battery was manufactured in the same manner as Example 1, except that Al2O3 and WO3 were mixed as coating raw materials in an amount such that the contents of Al and W were 1800 ppm and 3800 ppm, respectively, when manufacturing the positive electrode active material. Example 3 A lithium secondary battery was manufactured in the same manner as in Example 1, except that ZrO2 and SrO were mixed in an amount such that the contents of Zr and Sr were 3500 ppm and 800 ppm, respectively, instead of ZrO2 and Y2O3 as doping raw materials when manufacturing the positive electrode active material. Comparative Example 1 A lithium secondary battery was manufactured in the same manner as in Example 1, except that when manufacturing a cathode active material, ZrO2 and Y2O3 were mixed as doping raw materials in amounts such that the Zr and Y contents were 1200 ppm and 1400 ppm, respectively, and Al2O3 and WO3 were mixed as coating raw materials in amounts such that the Al and W contents were 1500 ppm and 1000 ppm, respectively. Comparative Example 2 A lithium secondary battery was manufactured in the same manner as in Example 1, except that when manufacturing a cathode active material, ZrO2 and Y2O3 were mixed as doping raw materials in amounts such that the Zr and Y contents were 1200 ppm and 500 ppm, respectively, and Al2O3 and WO3 were mixed as coating raw materials in amounts such that the Al and W contents were 500 ppm and 4200 ppm, respectively. Comparative Example 3 A lithium secondary battery was manufactured in the same manner as in Example 1, except that when manufacturing a cathode active material, ZrO2 and MgO were mixed in amounts such that the Zr and Mg contents were 1500 ppm and 1500 ppm, respectively, instead of ZrO2 and Y2O3 as doping raw materials, and Al2O3 and H3BO3 were mixed in amounts such that the Al and B contents were 1500 ppm and 500 ppm, respectively, instead of Al2O3 and WO3 as coating raw materials. Comparative Example 4 A lithium secondary battery was manufactured in the same manner as in Example 1, except that when manufacturing a cathode active material, ZrO2 and Nb2O3 were mixed in an amount such that the Zr and Nb contents were 1500 ppm and 1200 ppm, respectively, instead of ZrO2 and Y2O3 as doping raw materials, and Al2O3 and WO3 were mixed in an amount such that the Al and W contents were 500 ppm and 3000 ppm, respectively, as coating raw materials. Comparative Example 5 Ni as a transition metal hydroxide in the production of lithium nickel oxide 0.6 Co 0.1 Mn 0.3 Ni instead of (OH)2 0.86 Co 0.08 Mn 0.06 A lithium secondary battery was manufactured in the same manner as in Example 1, except that (OH)2 was used and calcination was performed at 890°C for 20 hours to manufacture a single-particle lithium nickel-based oxide. Comparative Example 6 A lithium secondary battery was manufactured using the same method as Example 1, except that secondary particle-type lithium nickel oxide was manufactured by performing calcination at 820°C for 20 hours during the manufacture of lithium nickel oxide. The average oxidation number AON of the doping elements of Examples 1 to 3 and Comparative Examples 1 to 6 using Equations (1) to (3) d , coating element average oxidation number AON cand the average oxidation number AON of doping elements and coating elements c+d was calculated, and the calculation results are shown in Table 1 below. Ni / Co / Mn particle shape M 1 M 2 AON d AON c AON c+d RW M1 / W M2Example 16 / 1 / 3 Single particle Zr 2800ppmY 1400ppmAl 1400ppmW 2900ppm3.663.703.680.040.98 Example 26 / 1 / 3 Single particle Zr 2800ppmY 1400ppmAl 1800ppmW 3800ppm3.663.713.690.050.75 Example 36 / 1 / 3 Single particle Zr 2500ppmSr 800ppmAl 1400ppmW 2900ppm3.623.703.660.080.77 Example 46 / 1 / 3 Single particle Zr 2800ppmY 1400ppmAl 1400ppmW 3000ppm3.663.723.690.060.95Example 56 / 1 / 3Single particle Zr 2800ppmY 1400ppmAl 1450ppmW 3400ppm3.663.773.730.110.87Comparative example 16 / 1 / 3Single particle Zr 1200ppmY 1400ppmAl 1500ppmW 1000ppm3.463.273.330.191.04Comparative example 26 / 1 / 3Single particle Zr 1200ppmY 500ppmAl 500ppmW 4200ppm3.704.664.360.960.36Comparative example 36 / 1 / 3Single particle Zr 1500ppmMg 1500ppmAl 1500ppmB 500ppm2.423.002.750.581.50Comparative example 46 / 1 / 3Single particle Zr 1500ppmNb 1200ppmAl 500ppmW 3000ppm4.444.404.420.040.77Comparative example 586 / 8 / 6Single particle Zr 2800ppmY 1400ppmAl 1400ppmW 2900ppm3.663.703.680.040.98Comparative example 66 / 1 / 3Secondary particle Zr 2800ppmY 1400ppmAl 1400ppmW 2900ppm3.663.703.680.040.98Comparative example 76 / 1 / 3 single particle Zr 400ppmY 200ppmAl 1400ppmW 3000ppm3.663.723.710.060.13Comparative example 86 / 1 / 3 single particle Zr 2800ppmY 1400ppmAl 1000ppmW 1200ppm3.663.453.560.211.9Comparative example 986 / 8 / 6 single particle Zr 2800ppmY 1400ppmAl 1400ppmW 3000ppm3.663.723.690.060.95Comparative example 106 / 1 / 3Secondary particle Zr 2800ppmY 1400ppmAl 1400ppmW 3000ppm3.663.723.690.060.95Comparative example 116 / 1 / 3Single particle Zr 400ppmY 200ppmTi 1500ppmNb 1200ppm3.664.294.210.630.22Comparative example 126 / 1 / 3Secondary particle Zr 2800ppmY 1400ppmAl 500ppmW 5000ppm3.664.784.221.120.76. Experimental Example 1 Each of the lithium secondary batteries manufactured in Examples 1 to 5 and Comparative Examples 1 to 12 was charged to 4.35 V at 0.5 C at 45°C and then discharged to 2.5 V at 1.0 C for 50 cycles, with one cycle being considered the charge-discharge cycle. Then, the capacity retention rate and resistance increase rate were measured. The measurement results are shown in [Table 2] below. Capacity retention rate (%) Resistance increase rate (%) Example 191.3 87.4 Example 291.2 87.6 Example 390.8 85.5 Example 491.0 88.4 Example 591.2 86.4 Comparative example 189.4 90.5 Comparative example 288.9 95.5 Comparative example 388.2 75.9 Comparative example 485.5 101.5 Comparative example 588.1 99.7 Comparative example 685.2 129.5 Comparative example 783.5 100.5 Comparative example 888.1 94.5 Comparative example 989.7 91.5 Comparative example 1084.2 115.8 Comparative example 1187.5 120.5 Comparative example 1285.2 124.5 Through the above Table 2, it can be confirmed that the secondary batteries of Examples 1 to 5 have superior life characteristics compared to the secondary batteries of Comparative Examples 1 to 12.

Claims

1. Ni content is 50 mol% to 75 mol%, and doping element M 1 Single particle lithium nickel oxide doped with; and Formed on the above single particle lithium nickel oxide, coating element M 2 Includes a coating layer including, Oxidation number AON defined by the following equation (1) c+d is 3.5 to 4.2, R, defined by the following equation (2), is 0.5 or less, The above coating element M 2 The above doping element M for the weight of 1 Weight ratio of (M 1 / M 2 ) is a positive electrode active material having a value of 0.2 to 1.

0. Equation (1): AON c+d = {∑(M 1 Oxidation number of the element ×M 1 mole fraction of an element) + ∑(M 2 Oxidation number of the element ×M 2 mole fraction of an element) / (M 1 Elements and M 2 Sum of mole fractions of elements) 식 (2): R = | AON d - AON c | In the above equation (2), AON d is a doping element M defined by the following equation (2-1). 1 Average oxidation state of AON c is a coating element M defined by the following equation (2-2). 2 is the average oxidation number. Equation (2-1): AON d = ∑ (M 1 Oxidation number of the element × M 1 Mole fraction of element) / (M 1 Sum of mole fractions of elements) Equation (2-2): AON c = ∑ (M 2 Oxidation number of the element × M 2 Mole fraction of element) / (M 2 Sum of mole fractions of elements) 2. In paragraph 1, The above doping element M 1 A cathode active material comprising at least one selected from the group consisting of Ti, Mg, Al, Zr, Y, Ba, B, Ca, Sr, W, Ta, Nb, and Mo.

3. In paragraph 1, The above doping element M 1 A cathode active material comprising two or more selected from the group consisting of Ti, Mg, Al, Zr, Y, Ba, B, Ca, Sr, W, Ta, Nb, and Mo.

4. In paragraph 1, The above doping element M 1 A cathode active material comprising at least one element selected from Y, Sr, Ti and Nb; and Zr.

5. In paragraph 1, The above coping element M 2 A cathode active material comprising at least one selected from the group consisting of Ti, Mg, Al, Zr, Y, Ba, Ca, Sr, W, Ta, Nb, and Mo.

6. In paragraph 1, The above coping element M 2 A cathode active material comprising two or more selected from the group consisting of Ti, Mg, Al, Zr, Y, Ba, Ca, Sr, W, Ta, Nb, and Mo.

7. In paragraph 1, The above coping element M 2 A cathode active material comprising Al and W.

8. In paragraph 1, The average oxidation number AON of the doping element represented by the above formula (2-1) d A positive electrode active material having a value of 2.5 to 5.

5.

9. In paragraph 1, The average oxidation number AON of the coating element represented by the above formula (2-2) c A positive electrode active material having a value of 2.5 to 5.

5.

10. In paragraph 1, A positive electrode active material having R defined by the above formula (2) of 0.01 to 0.

30.

11. In paragraph 1, The above doping element M 1 A cathode active material, which is contained in an amount of 500 ppm to 10,000 ppm based on the total weight of the cathode active material.

12. In paragraph 1, The above coating element M 2 A cathode active material, which is included in an amount of 500 ppm to 10,000 ppm based on the total weight of the cathode active material.

13. In paragraph 1, The above single particle lithium nickel oxide is a positive electrode active material represented by the following [chemical formula 1]. [Chemical Formula 1] Li 1+x [Ni a Co b Mr c M 1 d ]O2 In the above [chemical formula 1], M 1 It contains one or more elements selected from the group consisting of Ti, Mg, Al, Zr, Y, Ba, Ca, Sr, W, Ta, Nb, and Mo, and -0.1≤x≤0.1, 0.5≤a≤0.75, 0 <b<0.5, 0<c<0.5, 0<d≤0.2임.

14. In paragraph 1, A cathode active material having an average particle diameter of the nodules of the single-particle lithium nickel-based oxide of 0.8 ㎛ to 4 ㎛.

15. In paragraph 1, The above positive electrode active material is D 50 This positive electrode active material is 3㎛ to 8㎛.

16. A positive electrode comprising a positive electrode active material according to any one of claims 1 to 15.

17. A lithium secondary battery comprising a positive electrode according to claim 16.

18. In paragraph 17, The above lithium secondary battery has a charge cut-off voltage Lithium secondary battery with a voltage of 4.35 V or higher.