Positive electrode active material for a lithium secondary battery and the electrode and battery containing it

Abstract

Positive electrode active material for a lithium secondary battery, wherein the positive electrode active material comprises a doped single particle of a nickel-based lithium composite metal oxide, wherein the single particle contains several crystal grains, each crystal grain having a size of 180 nm to 300 nm, as measured by X-ray diffraction analysis using a Cu Kα X-ray beam, and 2500 to 6000 ppm of one or more elements selected from the group consisting of M = Al, Ti, Mg, Zr, W, Y, Sr, Na, Cu, Fe, Ca and B, which are doped into a crystal lattice of the single particle, wherein the single particle in its crystal lattice structure comprises a surface region with a rock salt structure, a spinel structure or a mixed structure thereof from the surface of the single particle to a depth of 0.13% to 5.26% of the radius of the single particle of the lithium composite metal oxide and a central region with a layered structure from the interface with the surface region to the center of the single particle, and wherein the individual particle has an average particle size D50 of 3.5 µm or more to 8 µm or less.

Description

TECHNICAL FIELD

[0001] The present invention relates to a positive electrode active material for a lithium secondary battery with improved lifetime properties at high voltage and to an electrode and battery containing this material. STATE OF THE ART

[0002] With increasing technological development and the demand for mobile devices, the demand for secondary batteries as an energy source has risen rapidly. Among these secondary batteries, lithium-ion batteries with high energy density and voltage, long lifespan, and low self-discharge have been commercially marketed and widely used.

[0003] Due to the recent price increase in cobalt (Co), many attempts have been made to increase price competitiveness by replacing the lithium cobalt oxide (LCO) currently used as the positive electrode active material for small batteries with inexpensive lithium nickel cobalt manganese oxide (NCM).

[0004] In the case of NCM (Nitrogen Cell Cells), the upper voltage limit in commercial cells is 4.2 V. When NCM, with an upper voltage limit of 4.35 V, is used in a small device, it performs worse compared to LCO (Lithium Carbon Oxide). This is because the lithium deintercalation of NCM is higher than that of LCO at the same upper voltage limit, and NCM becomes more unstable at high states of charge (SOC). As a result, its lifetime characteristics degrade rapidly when NCM is used at high voltages of 4.35 V or higher.

[0005] Accordingly, it is necessary to develop NCM positive electrode active materials with improved lifetime properties as a cost-effective positive electrode active material that can be operated at a high voltage. Disclosure technical problem

[0006] To solve the above problem, it is an object of the present invention to provide a positive electrode active material for a lithium secondary battery with improved lifetime characteristics at a high voltage. TECHNICAL SOLUTION

[0007] One embodiment of the present invention provides a positive electrode active material for a lithium secondary battery, wherein the positive electrode active material comprises a doped single particle of a nickel-based lithium composite metal oxide, the single particle containing several crystal grains, each crystal grain having a size of 180 nm to 300 nm, measured by X-ray diffraction analysis with a Cu Kα X-ray beam, and 2500 to 6000 ppm of one or more elements selected from the group consisting of M = Al, Ti, Mg, Zr, W, Y, Sr, Na, Cu, Fe, Ca and B, which are doped into a crystal lattice of the single particle, wherein the single particle in its crystal lattice structure has a surface region with a rock salt structure, a spinel structure or a mixed structure thereof from the surface of the single particle to a depth of 0.13% to 5%.26% of the radius of the single particle of the lithium composite metal oxide and a central region with a layered structure from the interface with the surface region to the center of the single particle, and wherein the single particle has an average particle size D50 of 3.5 µm or more to 8 µm or less.

[0008] Another embodiment of the present invention provides a positive electrode active material for a lithium secondary battery, wherein the positive electrode active material comprises: a doped single particle of a nickel-based lithium composite metal oxide, wherein the single particle contains several crystal grains, each crystal grain having a size of 180 nm to 300 nm, measured by Cu-Kα X-ray, and one or more elements selected from the group consisting of M = Al, Ti, Mg, Zr, W, Y, Sr, Na, Cu, Fe, Ca and B, which is doped into a crystal lattice of the single particle; and a compound coated onto the surface of the single particle, wherein the compound comprises one or more elements selected from the group consisting of M' = Al, Ti, Mg, Zr, W, Y, Sr, Co, Na, Cu, Fe, Ca and B, wherein a total content of the element M, which is doped into the crystal lattice of the single particle, and of the element M' in the compound,which is coated on its surface, is 2500 ppm to 6000 ppm, wherein the individual particle in its crystal lattice structure has a surface region with a rock salt structure, a spinel structure or a mixed structure thereof from the surface of the individual particle to a depth of 0.13% to 5.26% of the radius of the individual particle of the lithium composite metal oxide and a central region with a layered structure from the interface with the surface region to the center of the individual particle, and wherein the individual particle has an average particle size D50 of 3.5 µm or more to 8 µm or less.

[0009] Another embodiment of the present invention provides a positive electrode active material for a lithium secondary battery, wherein the positive electrode active material comprises a doped single particle of a nickel-based lithium composite metal oxide, wherein the nickel-based lithium composite metal oxide is represented by the chemical formula 1 below, wherein the single particle contains several crystal grains, each crystal grain having a size of 180 nm to 300 nm, measured by X-ray diffraction analysis with a Cu Kα X-ray beam, and 2500 to 6000 ppm of one or more elements selected from the group consisting of M = Al, Ti, Mg, Zr, W, Y, Sr, Na, Cu, Fe, Ca and B, which are doped into a crystal lattice of the single particle, wherein the single particle has in its crystal lattice structure a surface region with a rock salt structure,a spinel structure or a mixed structure thereof from the surface of the single particle to a depth of 0.13% to 5.26% of the radius of the single particle of the lithium composite metal oxide and a central region with a layered structure from the interface with the surface region to the center of the single particle, and wherein the single particle has an average particle size D50 of 3.5 µm or more to 8 µm or less: Li, a (Ni x Mn y Co z )O 2+b (1) wherein in the chemical formula 1 0.95≤a≤1.2, 0≤b≤0.02, 0 <x<0,6, 0≤y≤0,4, 0≤z<1, and x+y+z=1.

[0010] Another embodiment of the present invention provides a positive electrode active material for a lithium secondary battery, wherein the positive electrode active material comprises: a doped single particle of a nickel-based lithium composite metal oxide, wherein the nickel-based lithium composite metal oxide is represented by chemical formula 1 below, wherein the single particle contains several crystal grains, each crystal grain having a size of 180 nm to 300 nm, measured by Cu-Kα X-ray, and one or more elements selected from the group consisting of M = Al, Ti, Mg, Zr, W, Y, Sr, Na, Cu, Fe, Ca and B, which is doped into a crystal lattice of the single particle; and a compound coated on the surface of the single particle, wherein the compound comprises one or more elements selected from the group consisting of M' = Al, Ti, Mg, Zr, W, Y, Sr, Co, Na, Cu, Fe, Ca and B,wherein a total content of element M doped into the crystal lattice of the single particle and of element M' in the compound coated on its surface is 2500 ppm to 6000 ppm, wherein the single particle in its crystal lattice structure comprises a surface region with a rock salt structure, a spinel structure or a mixed structure thereof from the surface of the single particle to a depth of 0.13% to 5.26% of the radius of the single particle of the lithium composite metal oxide and a central region with a layered structure from the interface with the surface region to the center of the single particle, and wherein the single particle has an average particle size D50 of 3.5 µm or more to 8 µm or less: Li, a (Ni x Mn y Co z )O 2+b (1) wherein in the chemical formula 1 0.95≤a≤1.2, 0≤b≤0.02, 0 <x<0,6, 0≤y≤0,4, 0≤z<1, and x+y+z=1.

[0011] Another embodiment of the present invention provides a positive electrode for a lithium secondary battery, wherein the positive electrode contains the positive electrode active material described above, and a lithium secondary battery containing the positive electrode. EFFECT OF THE INVENTION

[0012] A positive electrode active material for a lithium secondary battery according to the present invention can improve the lifetime characteristics at a high voltage. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figures 1A to 1F show scanning electron microscopy (SEM) images of positive electrode active materials produced in Examples 2, 4, 6, 8, 10 and 12 respectively; Fig. 2A to 2G show images of TEM-ASTAR and HR-TEM from Example 2 and Comparison Example 1; Fig. 3A and Fig.Figure 3B shows the gas formation of positive electrode active materials according to examples and comparative examples; and Fig. 4A and Fig. Figure 4B shows graphs of a comparison of the lifetime properties according to test example 3. BEST EXECUTION OF THE INVENTION

[0013] The following describes a method for producing a positive electrode active material for a lithium secondary battery, a positive electrode active material produced by the method, a positive electrode containing the positive electrode active material, and a lithium secondary battery according to specific embodiments of the present invention.

[0014] In this specification and the claims, "containing multiple crystal grains" means a crystal formed from two or more crystal particles with an average crystallite size within a defined range. The crystallite size of the crystal grain can be quantitatively analyzed by X-ray diffraction analysis (XRD) using Cu Kα X-rays (X-rα). Specifically, the manufactured particles are placed in a holder, and the diffraction pattern obtained by irradiating the particles with X-rays is analyzed, thereby quantitatively determining the average crystallite size of the crystal grain.

[0015] In the present description and the claims, D50 can be defined as a particle size at 50% of a particle size distribution and can be measured using a laser diffraction method.

[0016] Furthermore, it should be understood that the terms or words used in the specification and in the claims are not to be interpreted in the sense defined in commonly used dictionaries, but rather that the words or terms are to be interpreted in such a way as to have a meaning that corresponds to their meaning in the context of the relevant prior art and the technical idea of ​​the invention, based on the principle that an inventor can adequately define the meaning of the words or terms in order to explain the invention in the best possible way. Positive electrode active material

[0017] The present invention provides a positive electrode active material in the form of a single particle.

[0018] In particular, the positive electrode active material comprises a doped single particle of a nickel-based lithium composite metal oxide with an average particle size D50 of 3.5 µm or more to 8 µm or less, wherein the single particle contains several crystal grains, each crystal grain having a size of 180 nm to 300 nm, as measured by X-ray diffraction analysis using a Cu Kα X-ray beam, and wherein the single particle in its crystal lattice structure includes a surface region with a rock salt structure, a spinel structure or a mixed structure thereof from the surface of the single particle to a depth of 0.13% to 5.26% of the radius of the single particle of the lithium composite metal oxide and a central region with a layered structure from the interface with the surface region to the center of the single particle.The positive electrode active material has: 2500 to 6000 ppm of one or more elements selected from the group consisting of M = Al, Ti, Mg, Zr, W, Y, Sr, Na, Cu, Fe, Ca and B, which are doped into a single-particle crystal lattice; or one or more elements selected from the group consisting of M = Al, Ti, Mg, Zr, W, Y, Sr, Na, Cu, Fe, Ca and B, which are doped into a crystal lattice of the single particle, and a compound coated on the surface of the single particle, wherein the compound comprises one or more elements selected from the group consisting of M' = Al, Ti, Mg, Zr, W, Y, Sr, Co, Na, Cu, Fe, Ca and B, wherein the total content of element M doped into the crystal lattice of the single particle and of element M' in the compound coated on its surface is 2500 ppm to 6000 ppm. The nickel-based lithium composite metal oxide can be modified by Li. a (No x Mn y Co z ) O2+b represented where 0.95≤a≤1, 2, 0≤b≤0.02, 0 <x<0,6, 0≤y≤0,4, 0≤z<1, and x+y+z=1.

[0019] The individual particles exhibiting the above properties contribute to improving the lifespan characteristics of a battery at high voltage.

[0020] The individual particle is described in detail below. Particle shape and crystal grain size

[0021] 1) In general, a nickel-based lithium composite metal oxide is a secondary particle, but the single particles are a nickel-based lithium composite metal oxide in the form of a single particle.

[0022] In particular, a secondary particle of a nickel-based lithium composite metal hydroxide produced by co-precipitation is used as a precursor; this precursor is mixed with a lithium raw material, and this mixture is calcined at a temperature below 960°C to obtain a secondary particle of a nickel-based lithium composite metal oxide.

[0023] However, if the calcination temperature is increased to 960°C or higher, the particle no longer exhibits a secondary particle shape, and individual particles of the nickel-based lithium composite metal oxide can be obtained. This resulting product can be used as the individual particle of the present invention.

[0024] 2) However, the secondary particle of a nickel-based lithium composite metal oxide and the individual particles contain multiple crystal grains, regardless of the calcination temperature. "Containing multiple crystal grains" here means a crystal formed from two or more crystal particles with an average crystallite size within a specific range. The crystallite size of the crystal grain can be quantitatively analyzed by X-ray diffraction analysis (XRD) using a copper Kα X-ray beam (X-rα). Specifically, the produced particles are placed in a holder, and the diffraction pattern obtained by irradiating the particles with an X-ray beam is analyzed, thereby quantitatively determining the average crystallite size of the crystal grain.

[0025] Depending on the calcination temperature, however, a difference in crystal grain size can occur. In particular, if calcination is carried out at a low temperature below 960°C, crystal grains with a size of less than 180 nm can be obtained. This means that if the crystal grain size is less than 180 nm, it is difficult to obtain a single particle with a perfect shape. Consequently, there is a risk that the interface between a positive electrode active material and an electrolyte becomes large, and the contact between the particles and the electrolyte increases due to volume changes during charging / discharging. Furthermore, if the average crystallite size of the particles exceeds 300 nm, there is a risk that the capacitance will be reduced due to the enlargement of the crystal grains.

[0026] However, if the individual particles of the invention are excessively calcined at a temperature of 960°C or higher, in particular at 960°C to 1100°C, for example at 990°C to 1100°C, the crystal grains may become coarsened, and therefore crystal grains with a size of up to 180 nm to 300 nm may be present.

[0027] As such, the individual particles containing the coarsened crystal grains (180 nm to 300 nm) have a lower specific surface area (BET) than the secondary particles of a nickel-based lithium composite metal oxide containing smaller crystal grains, and therefore its reactivity with an electrolyte is low, and gas formation and release of internal metals can be reduced.

[0028] In general, for the same composition, the size of the individual particle and the size of the crystal grains within the individual particle increase with increasing calcination temperature, regardless of the particle shape. However, the results of X-ray diffraction analysis with a Cu Kα X-ray beam (X-rα) show that the crystal grains in the individual particles of the invention are larger when supercalcined at a temperature of 990°C (Examples 1 to 6) than those of the same composition supercalcined at a temperature of 1010°C (Examples 7 to 12). This is because the patterns resulting from supercalcination at 1010°C (Examples 7 to 12) are related to the degree of aggregation of the individual particles according to the calcination temperature and a measuring device, and do not deviate from the general trend.

[0029] When individual particles are supercalcined at 990°C (Examples 1 to 6), relatively small individual particles can aggregate and resemble secondary particles. This means that XRD is assumed to recognize this secondary-particle-like appearance and interpret the boundaries between the individual particles as grain boundaries, thus determining the individual particle size as a crystal grain size.

[0030] However, if the individual particles are supercalcined at 1010°C (Examples 7 to 12), relatively large individual particles can be observed separately while maintaining a certain distance from each other. It is therefore assumed that XRD detects individual particles and correctly identifies the crystal grain size within those particles. Average particle size (D50) and crystal structure

[0031] There are differences in the average particle size (D50) and crystal structure between the secondary particles of the nickel-based lithium composite metal oxide and the individual particles of the invention.

[0032] The average particle size (D50) of the secondary particles of the nickel-based lithium composite metal oxide can be 10 µm to 18 µm, and the average particle size (D50) of the individual particles of the invention is 3.5 µm or more to 8 µm or less.

[0033] As the D50 of the particles decreases, the specific BET surface area of ​​an active material increases. However, a decrease in BET due to the increase in crystal grain size caused by overcalcination is more pronounced than an increase in BET due to a decrease in particle size. As a result, the interface between an electrolyte and a positive electrode active material can be minimized to reduce side reactions and improve battery performance. Furthermore, manufacturing the active material in the form of small particles can increase capacity and efficiency, and the individual particles are easier to produce.

[0034] If the average particle size (D50) of the individual particles of the invention is less than 3.5 µm, there is a risk of reduced durability of the electrolyte and the positive electrode active material. If the average particle size (D50) of the individual particles of the invention is greater than 8 µm, there is a risk of reduced capacity due to overcalcination and a reduction in lifetime characteristics. Therefore, the average particle size (D50) of the individual particles of the invention is controlled in the range of 3.5 µm or more to 8 µm or less.

[0035] The crystal lattice structure of the secondary particles of the nickel-based lithium composite metal oxide can, however, exhibit a layered structure throughout the interior of the particle. This is due to the uniform formation of a layered structure consisting of lithium (Li) layer - cation mixed layer - lithium (Li) layer - cation mixed layer from the surface of the particle to the center of the particle at a temperature of less than 960°C.

[0036] In contrast, the individual particles of the invention exhibit different crystal structures in their central region and in their surface region. This is due to the structural change of the particle surface from a layered structure to a rock salt structure, a spinel structure, or a mixed structure thereof at a temperature of 960°C or higher. In particular, at a temperature of 960°C or higher, 960°C to 1100°C, or, for example, 990°C to 1100°C, a portion of the lithium is lost from the surface of the individual particles of the nickel-based lithium composite metal oxide, and the Ni 2+ Ions from the lower region migrate into the underlying lithium (Li) layer, resulting in a successive degradation of the cation-mixed layer. These successive reactions can occur from the surface of the individual particles of the nickel-based lithium composite metal oxide down to a certain depth.

[0037] In particular, the individual particles of the invention have a surface region and a central region that differ from each other with respect to the crystal lattice structure.

[0038] More specifically, the surface region of the individual particles of the invention contains a rock salt structure, a spinel structure, or a mixed structure thereof, extending from the surface of an individual particle to a depth of 0.13% to 5.26%, for example, a depth of 0.13% to 2.63% of the radius of the individual particle. Meanwhile, the central region of the individual particles of the invention exhibits a layered structure from the interface with the surface region to the center of the individual particle.

[0039] The surface area of ​​the rock salt structure, the spinel structure or the mixed structure thereof of the individual particles of the invention can exhibit low reactivity with an electrolyte, can be structurally stable and can retain its structural stability even when a charging voltage of more than 4.2 V, 4.4 V or more or 4.45 V or more is applied, compared to the surface area of ​​the layered structure of the secondary particles of the nickel-based lithium composite metal oxide. composition

[0040] 3) The single particle contains an element M doped into the crystal structure of a lithium composite metal oxide, which can be represented by the following chemical formula 1; and the single particle may, in addition to the element M doped into the crystal structure of the lithium composite metal oxide, which can be represented by the following chemical formula 1, contain a compound comprising an element M' and coated on the surface of the single particle: Li a (No x Mn y Co z ) O 2+b (1) wherein in the chemical formula 1 a, x, y and z represent a molar ratio of each element in the lithium composite metal oxide.

[0041] The element M doped into the crystal lattice of the single particle and the element M' of the compound coated onto the surface of the single particle can be the same or different. Element M is one or more elements selected from the group consisting of Al, Ti, Mg, Zr, W, Y, Sr, Na, Cu, Fe, Ca, and B, and element M' is one or more elements selected from the group consisting of Al, Ti, Mg, Zr, W, Y, Sr, Co, Na, Cu, Fe, Ca, and B.

[0042] In individual particles, the element M may be located only on a part of the particle's surface, depending on which position the element M prefers, and it may be arranged with a concentration gradient from the particle's surface to the particle's center, or it may be present uniformly throughout the entire particle.

[0043] If the individual particles are doped or coated and doped with the same element, the high-voltage properties of the active material can be further improved due to the stabilization of the surface structure. Among the elements that exhibit excellent surface structure stabilization, Ti, Mg, and Zr can be doped or coated and doped, or Zr alone can be used.

[0044] The element can be doped or coated and doped at concentrations ranging from 2500 ppm to 6000 ppm. If the element concentration is less than 2500 ppm, the structure-stabilizing effect of the doping or coating may be minimal. Conversely, if the element concentration exceeds 6000 ppm, there is a risk of reduced capacity and deterioration of lifetime and transmission rate characteristics due to increased resistance. The element can be coated or doped at concentrations ranging from 2500 ppm to 5500 ppm, and even more precisely from 3500 ppm to 5000 ppm, to achieve excellent performance enhancement through precise control of the element concentration.

[0045] Meanwhile, chemical formula 1 can correspond to a composition of a generally known secondary particle of a nickel-based lithium composite metal oxide.

[0046] For example, in chemical formula 1, lithium (Li) may be present in an amount corresponding to a, in particular 0.95 ≤ a ≤ 1.2. If a is less than 0.95, there is a risk of deterioration in the performance characteristics of a battery due to an increase in the interfacial resistance that arises at the contact surface between the positive electrode active material and the electrolyte. If, on the other hand, a is greater than 1.2, there is a risk of a reduction in the initial discharge capacity of the battery. Considering the effects of the combination with the characteristic structure of the active material according to an embodiment of the present invention, a can be even more specifically 0.98 ≤ a < 1.07, and even more specifically a = 1.

[0047] In chemical formula 1, nickel (Ni) is an element that contributes to the high voltage and high capacity of a secondary battery. Nickel (Ni) can be present in an amount corresponding to x, in particular 0 <x<0,6, enthalten sein, sofern die Bedingung x+y+z=1 erfüllt ist. Wenn x 0 ist, besteht die Gefahr einer Verschlechterung der Lade- / Entladekapazitätseigenschaften. Wenn x 0,6 oder mehr beträgt, besteht die Gefahr einer Verschlechterung der strukturellen und thermischen Stabilität des Aktivmaterials und, im Ergebnis, einer Verschlechterung der Lebensdauereigenschaften. Im Hinblick auf Hochspannungs- und Hochkapazitätseffekte durch Kontrolle des Nickelgehalts kann das Nickel insbesondere in einer Menge von 0,4≤x<0,6 und noch spezifischer in einer Menge von 0,5≤x<0,6 enthalten sein, sofern die Bedingung x+y+z=1 erfüllt ist.

[0048] Furthermore, manganese (Mn) in chemical formula 1 is an element that contributes to improving the thermal stability of the active material and can be present in an amount corresponding to y, in particular 0 ≤ y ≤ 0.4, provided the condition x + y + z = 1 is met. If y is greater than 0.4, there is a risk of deterioration of the lifetime properties due to increased manganese release. With a view to improving the thermal stability of the active material and improving its lifetime properties by controlling the manganese content, the manganese can be present even more specifically in an amount of 0.1 ≤ y < 0.4 and even more specifically in an amount of 0.1 ≤ y ≤ 0.3, provided the condition x + y + z = 1 is met.

[0049] Furthermore, in chemical formula 1, cobalt (Co) is an element that contributes to improving the charge / discharge cycle properties of the active material, and it can be present in an amount corresponding to z, in particular 0 ≤ z < 1, provided the condition x + y + z = 1 is met. If z is 1, there is a risk of deterioration of the charge / discharge capacity due to a deterioration of structural stability. With regard to improving the cycle properties of the active material by controlling the cobalt content, the cobalt can be present even more specifically in amounts of 0.1 ≤ z < 0.4 and even more specifically 0.1 ≤ z ≤ 0.3.

[0050] This means that chemical formula 1 can satisfy the following conditions: a=1, 0≤b≤0.02, 0.4≤x<0.6, 0.1≤y<0.4, 0.1≤z<0.4, and x+y+z=1, and in particular LiNi 0,5 Co 0,2 Mn 0,3 O2, LiNi 0,5 Co 0,3 Mn 0,2O2 or the like. Any one of these, or a mixture of two or more, can be included in the positive electrode active material. Method for producing a positive electrode active material

[0051] This document describes a method for producing the individual particles of the invention.

[0052] In particular, a single particle according to one embodiment can be produced by a series of processes that include the following steps: Producing an initial mixture comprising a lithium composite metal hydroxide particle with a D50 of 8 µm or less, a lithium raw material, and a compound comprising one or more elements selected from the group consisting of M = Al, Ti, Mg, Zr, W, Y, Sr, Na, Cu, Fe, Ca, and B; and Calcining the first mixture at a temperature of 960°C or higher.

[0053] In the step of calcining the first mixture at a temperature of 960°C or higher, the single particle of a nickel-based lithium composite metal oxide containing multiple crystal grains can be synthesized, and simultaneously the element M of the compound containing the element M can be doped into the crystal lattice of the single particle of the lithium composite metal oxide, thereby obtaining the single particle.

[0054] With regard to the content of the element doped in the ultimately obtained individual particles, the content of the compound containing element M, relative to the total weight of the first mixture, can be controlled to provide M in a range of 2500 ppm to 6000 ppm.

[0055] Meanwhile, another single particle of the invention can be produced by a series of processes that include the following steps: Producing an initial mixture comprising a nickel-based lithium composite metal hydroxide particle with a D50 of 8 µm or less, a lithium raw material and a compound comprising one or more elements selected from the group consisting of M = Al, Ti, Mg, Zr, W, Y, Sr, Na, Cu, Fe, Ca and B; Calcining the first mixture at a temperature of 960°C or higher; Producing a second mixture comprising the calcined product of the first mixture and a compound comprising one or more elements selected from the group consisting of M' = Al, Ti, Mg, Zr, W, Y, Sr, Co, Na, Cu, Fe, Ca and B; and Calcining of the second mixture at a temperature of 350°C to 800°C.

[0056] As in the production of the previously described single particle, in the step of calcining the first mixture at a temperature of 960°C or higher during the production of the other single particle of the invention, the single particle of a nickel-based lithium composite metal oxide containing several crystal grains can be synthesized, and at the same time the element M of the compound containing the element M can be doped into the crystal lattice of the single particle of the lithium composite metal oxide.

[0057] In contrast to the production of the single particle described above, the additional step of calcining the second mixture at a temperature of 350°C to 800°C can be carried out after the production of the second mixture, which contains the calcined product of the first mixture and the compound containing the element M', thereby obtaining another single particle of the invention.

[0058] Furthermore, the total content of the compound containing element M and the compound containing element M' can be controlled relative to the total weight of the first mixture and the second mixture to provide a total content of M and M' in a range of 2500 ppm to 6000 ppm.

[0059] With regard to the process for producing the individual particles, overlaps with the above statements are omitted and process characteristics are described in detail. calcination process

[0060] During the production of the individual particles, if the first mixture, that is, the mixture of the lithium composite metal hydroxide particle with a D50 of 8 µm or less, the lithium raw material and the compound containing element M, is calcined at a temperature of 960°C or higher, the individual particle of the lithium composite metal oxide, which contains several crystal grains, can be synthesized, and at the same time the element M of the compound containing element M can be doped into the crystal lattice of the individual particle of the lithium composite metal oxide.

[0061] The calcination temperature can be set to 960°C or higher, taking into account the factors described above, such as the production of individual particles, the size control of the crystal grains, etc. More specifically, the calcination temperature can be set to a temperature between 960°C and 1100°C, for example, between 990°C and 1100°C. In particular, if the Ni content is less than 0.6, overcalcination cannot occur at a temperature below 960°C. If the calcination temperature is below 960°C, the D50 value of the active material to be produced is therefore not as large as the range according to the invention, so there is a risk of deterioration of battery performance due to side reactions between the electrolyte and the positive electrode active material at a high state of charge (SOC).In contrast, a calcination temperature of more than 1100°C is not preferred, as the capacity may decrease due to the enlargement of the crystal grains.

[0062] The overcalcination process can be carried out in an oxidizing atmosphere containing oxygen, or more specifically, in an atmosphere with an oxygen content of 20% by volume or more.

[0063] The lithium composite metal hydroxide particle with a D50 of 8 µm or less can be a precursor for the production of the single particle of an embodiment described above, which is represented by the following chemical formula 2: (No x Mn y Co z ) OH 2+b (2) wherein in the chemical formula 2 0≤b≤0.02, 0 <x<0,6, 0≤y≤0,4, 0≤z<1, und x+y+z=1.

[0064] The average particle size (D50) of the lithium composite metal hydroxide particle can be, in particular, 4 µm or more to 8 µm or less. If the positive electrode active material is prepared using the precursor with a size in the above range, it is possible to produce a positive electrode active material with a D50 of 4 µm or more to 8 µm or less in the form of a single particle.

[0065] In particular, the lithium composite metal hydroxide particle with a D50 of 8 µm or less can be an oxide, hydroxide or oxyhydroxide containing nickel, cobalt and manganese as a precursor.

[0066] The precursor can be produced by a conventional process, except that the raw materials nickel, cobalt, and manganese are used in the amounts defined in chemical formula 1, and the average particle size (D50) of the finally produced precursor is 7 µm or less. For example, the precursor can be produced by a solid-state process in which nickel oxide, cobalt oxide, and manganese oxide are mixed and subsequently subjected to heat treatment, or it can be produced by a co-precipitation process in which the corresponding metal salts containing nickel, cobalt, and manganese are added to a solvent, in particular water or a mixture of water and an organic solvent miscible with water (in particular, an alcohol, etc.).

[0067] Furthermore, the lithium raw material can be a lithium-containing oxide, sulfate, nitrate, acetate, carbonate, oxalate, citrate, halide, hydroxide, oxyhydroxide, etc., and in particular Li₂CO₃, LiNO₃, LiNO₂, LiOH, LiOH · H₂O, LiH, LiF, LiCl, LiBr, LiI, CH₃COOLI, Li₂O, Li₂SO₄, CH₃COOLI, Li₃C₆H₅O₇, etc. Any of these or a mixture of two or more can be used. With regard to reaction efficiency and reducing the formation of byproducts during the reaction with the precursor to form the lithium composite metal oxide, the lithium raw material can be Li₂O or Li₂CO₃.

[0068] Furthermore, the raw material of the dopant element M can be an element M-containing oxide, sulfate, nitrate, acetate, carbonate, oxalate, citrate, halide, hydroxide, oxyhydroxide, etc. In this case, M is the same as described above.

[0069] The precursor for the formation of the lithium composite metal oxide, the lithium raw material and the raw material of element M or M' can be used after they have been mixed in quantities corresponding to the content range of lithium in the ultimately produced lithium composite metal oxide of chemical formula 1 and the content range of element M contained in the positive electrode active material (corresponding to a sum of M and M' in the manufacturing process). Coating process

[0070] The process for producing the coated single particle may further include the steps of producing a second mixture containing the calcined product of the first mixture and a compound comprising one or more elements selected from the group consisting of M' = Al, Ti, Mg, Zr, W, Y, Sr, Co, Na, Cu, Fe, Ca and B), and calcining the second mixture at a temperature of 350°C to 800°C after the step of calcining the first mixture at a temperature of 960°C or higher.

[0071] If this step is additionally included, a coating layer containing the compound containing the element M' can be formed on all or part of the surface of the single particle, and the compound containing the element M' can be in the form of a metal oxide, for example.

[0072] In this case, the coating element M' can be an element that is the same as or different from the doping element M.

[0073] Furthermore, the raw material of the coating element M' can be an element M'-containing oxide, sulfate, nitrate, acetate, carbonate, oxalate, citrate, halide, hydroxide, oxyhydroxide, etc. Here, M is the same as described above. An additional heat treatment process to form the coating layer can be carried out, as in the doping process, at a temperature of 350°C to 800°C, or more specifically at a temperature of 350°C to 650°C, in an oxidizing atmosphere containing oxygen.

[0074] If the temperature of the secondary heat treatment for the additional coating is lower than 350°C, the coating layer cannot be formed sufficiently, and if the temperature is higher than 800°C, there are problems with cation mixing and a deterioration of the capacity and transfer rate characteristics. Post-treatment process

[0075] However, after overcalcination during the production of the single particle and after secondary heat treatment during the production of the coated single particle, a cooling process can optionally be carried out.

[0076] The cooling process can be carried out using a common method, in particular a method such as natural cooling in an air atmosphere or hot air cooling.

[0077] Since the positive electrode active material for a lithium secondary battery, manufactured according to the process described above, can exhibit a reduced specific surface area (SFA), the interface with the electrolyte can be minimized. Furthermore, the amount of residual lithium in the active material is reduced through overcalcination, thereby minimizing side reactions with the electrolyte. Consequently, the positive electrode active material can exhibit excellent battery performance and lifetime characteristics when the battery is operated at a high voltage of 4.35 V or higher, and, in particular, its structural stability allows it to exhibit excellent high-temperature lifetime characteristics. Lithium secondary battery

[0078] Another embodiment of the present invention provides a positive electrode for a lithium secondary battery, wherein the positive electrode contains the positive electrode active material which contains one of the individual particles of the invention, and a lithium secondary battery which contains the positive electrode.

[0079] The positive electrode and the lithium secondary battery, each manufactured using the positive electrode active material described above, can exhibit excellent lifetime characteristics even at a high SOC.

[0080] In particular, the positive electrode can include a positive electrode collector and a positive electrode active material layer formed on the positive electrode collector and containing the positive electrode active material described above.

[0081] The positive electrode collector is not particularly restricted as long as it exhibits conductivity without causing chemical changes within the battery. For example, stainless steel, aluminum, nickel, titanium, calcined carbon and aluminum, or stainless steel surface-treated with carbon, nickel, titanium, or silver can be used. The positive electrode collector can have a thickness of 3 µm to 500 µm, and the adhesion of the positive electrode active material can be improved by creating a fine roughness on the collector's surface. For example, the collector can be in a variety of forms, such as a film, layer, foil, mesh, porous material, foamed material, nonwoven material, etc.

[0082] Furthermore, the positive electrode active material layer can contain a conductive material and a binder together with the positive electrode active material described above.

[0083] Here, the conductive material is used to provide a conductive electrode and is not particularly limited as long as it exhibits electrical conductivity without causing chemical changes in the battery. Specific examples may include: carbon-based materials such as carbon black, acetylene black, Ketjen black, sewer soot, furnace soot, lamp soot, thermal soot, carbon fibers, etc.; graphite such as natural or synthetic graphite; metal powders or metal fibers of copper, nickel, aluminum, silver, etc.; conductive whiskers such as zinc oxide, potassium titanate, etc.; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives, etc. These may be used alone or as a mixture of two or more. The conductive material may be present in an amount ranging from 1% to 30% by weight, based on the total weight of the positive electrode active material layer.

[0084] Furthermore, the binder improves the adhesion between the positive electrode active materials and the bond strength between the positive electrode active material and the collector. Specific examples include: polyvinylidene fluoride (PVDF), a vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, an ethylene propylene diene polymer (EPDM), sulfonated EPDM, styrene-butadiene rubber (SBR), fluororubber, or combinations thereof. These can be used alone or as a mixture of two or more. The binder can be present in an amount ranging from 1% to 30% by weight, based on the total weight of the positive electrode active material layer.

[0085] The positive electrode can be manufactured using a standard positive electrode manufacturing process, except for the use of the positive electrode active material described above. Specifically, the positive electrode can be manufactured by applying a slurry to form a positive electrode active material layer onto a positive electrode collector, followed by drying and rolling. The slurry is prepared by mixing the positive electrode active material described above, and optionally the binder and conductive material, in a solvent. The type and proportion of the positive electrode active material, binder, and conductive material are the same as described above.

[0086] The solvent can be a commonly used solvent and may include: dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, water, etc. These can be used alone or as a mixture of two or more. Taking into account the coating thickness of the slurry and the production yield, the solvent can be used in an amount sufficient to dissolve or disperse the positive electrode active material, the conductive material, and the binder, and to give the slurry a viscosity that allows for excellent uniformity of thickness when applied to fabricate the positive electrode.

[0087] As an alternative method, the positive electrode can be produced by pouring the slurry for forming the positive electrode active material layer onto a separate support and then laminating a film detached from the support onto the positive electrode collector.

[0088] Another embodiment of the present invention provides an electrochemical device containing the positive electrode. The electrochemical device can, in particular, be a battery, a capacitor, etc., and more specifically, a lithium secondary battery.

[0089] The lithium secondary battery can, in particular, include a positive electrode, a negative electrode opposite the positive electrode, a separator arranged between the positive and negative electrodes, and an electrolyte. The positive electrode is the same as described above. The lithium secondary battery can also optionally include a battery container housing an electrode assembly consisting of the positive electrode, the negative electrode, and the separator, as well as a sealing element for sealing the battery container.

[0090] In the lithium secondary battery, the negative electrode contains a negative electrode collector and a negative electrode active material layer that is arranged on the negative electrode collector.

[0091] The negative electrode collector is not particularly limited in its applications, as long as it exhibits high conductivity without causing chemical changes within the battery. For example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, or silver, or an aluminum-cadmium alloy can be used. The negative electrode collector can also typically have a thickness of 3 µm to 500 µm, and, as with the positive electrode collector, the adhesion of the negative electrode active material can be improved by creating a fine roughness on the collector's surface. For example, the collector can be in a variety of forms, such as a film, layer, foil, mesh, porous material, foamed material, nonwoven material, etc.

[0092] Furthermore, the negative electrode active material layer can optionally contain a binder and a conductive material along with the negative electrode active material. The negative electrode active material layer can be produced, for example, by applying and drying a slurry to form the negative electrode onto the negative electrode collector, wherein the slurry is prepared by mixing the negative electrode active material and optionally the binder and the conductive material in a solvent, or by casting a composition for forming the negative electrode onto a separate support and subsequently laminating a film detached from the support onto the negative electrode collector.

[0093] The negative electrode active material can be a compound capable of reversible intercalation and deintercalation of lithium. Specific examples may include one or a mixture of two or more of the following: a carbon material such as synthetic graphite, natural graphite, graphitized carbon fiber, amorphous carbon, etc.; a metal compound that can be alloyed with lithium, such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, a Si alloy, a Sn alloy, an Al alloy, etc.; a metal oxide that can dope and dedope lithium ions, such as SiO₂. x(0<x<2), SnO2, Vanadiumoxid oder Lithium-Vanadiumoxid, und ein Verbundmaterial, das die Metallverbindung und das Kohlenstoffmaterial enthält, wie ein Si-C-Verbundmaterial oder ein Sn-C-Verbundmaterial. Das Negativelektrodenaktivmaterial kann auch ein Lithiummetalldünnfilm sein. Darüber hinaus können sowohl niederkristalliner als auch hochkristalliner Kohlenstoff usw. als Kohlenstoffmaterial verwendet werden. Der niederkristalline Kohlenstoff ist ein weicher oder harter Kohlenstoff, und der hochkristalline Kohlenstoff ist ein hochtemperaturkalzinierter Kohlenstoff, wie amorpher, plättchenförmiger, flockiger, sphärischer oder faseriger natürlicher Graphit oder künstlicher Graphit, Kish-Graphit, pyrolytischer Kohlenstoff, Kohlenstofffasern auf Mesophasenpechbasis, Mesokohlenstoff-Mikroperlen, Mesophasenpechen, aus Erdöl oder Kohlenteer gewonnene Kokse oder dergleichen.

[0094] Furthermore, the binder and the conductive material can be the same as described for the positive electrode.

[0095] Meanwhile, in a lithium secondary battery, the separator serves to separate the negative and positive electrodes and create a passage for the lithium ions. The separator is not particularly limited as long as it is used as a separator in a conventional lithium secondary battery, and in particular, a separator is preferred that exhibits low resistance to electrolyte migration and has an excellent capacity to absorb an electrolyte solution. Specifically, the separator can be a porous polymer film made from a polyolefin-based polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, an ethylene / methacrylate copolymer, or the like, or a layered structure with two or more layers thereof.Alternatively, the separator can be a conventional porous nonwoven fabric, such as a high-melting-point glass fiber, polyethylene terephthalate fiber, or similar material. To ensure heat resistance or mechanical strength, the separator can also be coated, containing ceramic components or polymeric materials, and optionally used in a single- or multi-layer structure.

[0096] Furthermore, the electrolyte used in the present invention can be an organic liquid electrolyte, an inorganic liquid electrolyte, a solid polymer electrolyte, a gel polymer electrolyte, an inorganic solid electrolyte, an inorganic molten electrolyte, etc., which can be used in the manufacture of a lithium secondary battery, but the present invention is not limited thereto.

[0097] In particular, the electrolyte may contain an organic solvent and a lithium salt.

[0098] The organic solvent is not particularly restricted, as long as it can act as a medium that allows the ions involved in a battery's electrochemical reaction to migrate. Specifically, the organic solvent can be: an ester-based solvent such as methyl acetate, ethyl acetate, γ-butyrolactone, ε-caprolactone, etc.; an ether-based solvent such as dibutyl ether, tetrahydrofuran, etc.; a ketone-based solvent such as cyclohexanone, etc.; an aromatic hydrocarbon-based solvent such as benzene, fluorobenzene, etc.; a carbonate-based solvent such as dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (MEC), ethyl methyl carbonate (EMC), ethylene carbonate (EC), propylene carbonate (PC), etc.; an alcohol-based solvent such as ethyl alcohol, isopropyl alcohol, etc.Nitriles such as R-CN (where R is a C2 to C20 hydrocarbon group with a linear, branched, or cyclic structure and may contain a doubly bonded aromatic ring or an ether bond), etc.; amides such as dimethylformamide, etc.; dioxolanes such as 1,3-dioxolane, etc.; or sulfolane. Among these compounds, the carbonate-based solvent is preferred, and a mixture of a cyclic carbonate (e.g., ethylene carbonate, propylene carbonate, etc.) with high ionic conductivity and a high dielectric constant, which can increase the charging and discharging power of a battery, and a linear carbonate-based compound with low viscosity (e.g., ethyl methyl carbonate, dimethyl carbonate, diethyl carbonate, etc.) is even more preferred. If, in this case, the cyclic carbonate and the chain-like carbonate are used after mixing in a volume ratio of approximately 1:1 to approximately 1:9, excellent electrolyte performance can be achieved.

[0099] The lithium salt is not particularly restricted as long as it can supply lithium ions for use in a lithium secondary battery. The lithium salt can be, in particular: LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAlO4, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2FsSO3)2, LiN(C2F3SO2)2, LiN(CF3SO2)2, LiCl, LiI, LiB(C2O4)2, etc. The concentration of the lithium salt is preferably in the range of 0.1 M to 2.0 M. If the concentration of the lithium salt is within the above range, the electrolyte will have suitable conductivity and viscosity, allowing for excellent electrolyte performance and effective lithium ion migration.

[0100] In addition to the electrolyte components, the electrolyte may contain one or more additives to improve battery lifespan characteristics, suppress capacity degradation, enhance discharge capacity, etc. These additives may include haloalkyl carbonate-based compounds such as difluoroethylene carbonate, pyridine, triethyl phosphite, triethanolamine, cyclic ethers, ethylenediamine, n-glymers, triamide hexaphosphoric acid, nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinone, N,N-substituted imidazolidine, ethylene glycol dialkyl ethers, ammonium salts, pyrrole, 2-methoxyethanol, aluminum trichloride, etc. The additives may be present in amounts ranging from 0.1% to 5% by weight of the total electrolyte.

[0101] The lithium secondary battery, which contains the positive electrode active material according to the present invention, can stably exhibit excellent discharge capacity, output characteristics and capacity retention rate, making it advantageously suitable for use in portable devices such as mobile phones, notebooks, digital cameras, etc., and electric vehicles such as hybrid electric vehicles (HEVs), etc.

[0102] Accordingly, another embodiment of the present invention provides a battery module containing the lithium secondary battery as a cell unit, and a battery pack containing the same.

[0103] The battery module or battery pack can be used as a power source for one or more medium and large devices, such as a power tool, an electric car, including an electric vehicle (EV), a hybrid electric vehicle and a plug-in hybrid electric vehicle (PHEV), or as an energy storage system. DETAILED DESCRIPTION OF THE EXECUTION FORMS

[0104] The embodiments of the present invention are described in detail below so that a person skilled in the art with the usual knowledge in the field of the present invention can easily carry it out. However, the present invention can be implemented in various other embodiments and is not limited to those described here. Furthermore, the methods used in the experimental examples for measuring the physical properties of the active materials or precursors are the same as those described below. 1) Mean particle size D50 (µm): The particle sizes at 50% and 10% of the particle size distribution were measured for active materials and precursors respectively using a laser diffraction method (Microtrac MT 3000). 2) Crystallite size (nm): The crystal grain sizes (crystallite sizes, X sizes) of the individual particles were measured using an X-ray diffraction analyzer (Bruker AXS D4-Endeavor XRD) for measuring XRD (“X-ray diffraction”) with a Cu Kα X-ray beam (X-rα). 3) Amount of doping and amount of metal in the surface-coated metal compound: The amount of doped metal and / or the amount of metal in the surface-coated metal compound was / were measured using an inductively coupled plasma spectrometer (ICP). 4) Evaluation of the high-temperature properties of a 4.35 V full cell.

[0105] Each of the positive electrode active materials, a conductive carbon black material and a PVdF binder produced in the following examples and comparative examples were mixed in a weight ratio of 96:2:2 in an N-methylpyrrolidone solvent to produce a slurry for the formation of a positive electrode (viscosity: 5000 mPa·s), and the slurry was applied to an aluminum collector with a thickness of 20 µm, dried and rolled to produce a positive electrode.

[0106] Furthermore, artificial graphite MCMB (mesocarbon microbeads) as a negative electrode active material, a conductive carbon black material, a PVDF binder and a BM-L301 dispersion agent were mixed in a weight ratio of 96.5:0.75:1.25:1.5 in an N-methylpyrrolidone solvent to produce a slurry for the formation of a negative electrode, and the slurry was applied to a copper collector to produce a negative electrode.

[0107] A porous polyethylene separator was placed between the positive and negative electrodes, which were fabricated as described above, to create an electrode assembly. This assembly was then housed in a casing, and an electrolyte was injected into the casing to create a lithium secondary battery. The electrolyte was prepared by dissolving 1.15 M lithium hexafluorophosphate (LiPF6) in an organic solvent consisting of ethylene carbonate / dimethyl carbonate / ethyl methyl carbonate (volume ratio of the mixture EC / DMC / EMC = 3 / 4 / 3).

[0108] High-temperature lifetime maintenance rate (%): The lithium secondary batteries produced in this way were charged at 45°C with a constant current / constant voltage (CC / CV) from 0.7 C to 4.35 V / 38 mA and subsequently discharged with a constant current (CC) from 0.5 C to 2.5 V, and a discharge capacity was measured. This process was repeated for 1 to 100 cycles, and the results are presented in the Fig. 4A and Fig. 4B shown. Examples 1 to 6 (Overcalcination temperature: 990°C) Example 1

[0109] 94.91702 g of a Ni 0,5 Co 0,3 Mn 0,2 (OH)2 precursor with a particle size D50 of 4.2 µm, 38.86741 g LiOH as lithium raw material and 0.444807 g ZrO2, 0.010392 g MgO and 0.02594 g TiO2 as raw materials of element M were dry mixed and then supercalcined at 990°C to form a LiNi 0,5 Co 0,3 Mn 0,2To produce O2 positive electrode active material doped with 4000 ppm Zr / Mg / Ti (3500 ppm Zr, 250 ppm Mg and 250 ppm Ti), based on the total weight of the positive electrode active material. Example 2

[0110] A positive electrode active material doped with Zr / Mg / Ti was prepared in the same manner as in Example 1, except that a precursor of 5.2 µm was overcalcined at 990°C and doped with 4250 ppm Zr / Mg / Ti (3500 ppm Zr, 250 ppm Mg and 500 ppm Ti). Example 3

[0111] LiNi 0,5 Co 0,3 Mn 0,2 O2 doped with 4250 ppm Zr / Mg / Ti from Example 2, 0.026291 g Al2O3 and 0.028722 g B2O3 as raw material of element M' were mixed and calcined at 990°C to produce a doped positive electrode active material which was further coated with 900 ppm Al / B (500 ppm Al and 400 ppm B). Example 4

[0112] A positive electrode active material doped with Zr was prepared in the same manner as in Example 1, except that a precursor of 5.2 µm was overcalcined at 990°C and doped with 3500 ppm Zr using 0.444807 g ZrO2 as the raw material of element M. Example 5

[0113] A positive electrode active material doped with Zr was prepared in the same manner as in Example 1, except that a precursor of 5.2 µm was overcalcined at 990°C and 5500 ppm Zr was doped using 0.698983 g ZrO2 as the raw material of element M. Example 6

[0114] LiNi 0,5 Co 0,3 Mn 0,2 O2 doped with 4250 ppm Zr / Mg / Ti from Example 2, and 0.078872 g Al2O3 as raw material of element M' were mixed and calcined at 990°C to produce a doped positive electrode active material which was further coated with 1500 ppm Al. Examples 7 to 12 (Overcalcination temperature: 1010°C) Example 7

[0115] A LiNi 0,5 Co 0,3 Mn 0,2 O2 positive electrode active material doped with 4000 ppm Zr / Mg / Ti (3500 ppm Zr, 250 ppm Mg and 250 ppm Ti), based on the total weight of the positive electrode active material, was prepared in the same manner as in Example 1, except that the overcalcination was carried out at a temperature of 1010°C instead of 990°C as in Example 1. Example 8

[0116] A positive electrode active material doped with Zr / Mg / Ti was prepared in the same manner as in Example 1, except that the overcalcination was carried out at a temperature of 1010°C instead of 990°C as in Example 2, and 4250 ppm Zr / Mg / Ti (3500 ppm Zr, 250 ppm Mg and 500 ppm Ti) were doped in the same manner as in Example 2. Example 9

[0117] LiNi 0,5 Co 0,3 Mn 0,2 O2, doped with 4250 ppm Zr / Mg / Ti, was prepared in the same manner as in Example 3, except that the overcalcination was carried out at a temperature of 1010°C instead of 990°C as in Example 3. Subsequently, the doped positive electrode active material was further coated with 900 ppm Al / B (500 ppm Al and 400 ppm B) in the same manner as in Example 3. Example 10

[0118] A positive electrode active material doped with 3500 ppm Zr was prepared in the same manner as in Example 4, except that the overcalcination was carried out at a temperature of 1010°C instead of 990°C as in Example 4. Example 11

[0119] A positive electrode active material doped with 5500 ppm Zr was prepared in the same manner as in Example 5, except that the overcalcination was carried out at a temperature of 1010°C instead of 990°C as in Example 5. Example 12

[0120] LiNi 0,5 Co 0,3 Mn 0,2 O2, doped with 4250 ppm Zr / Mg / Ti, was prepared in the same manner as in Example 6, except that the overcalcination was carried out at a temperature of 1010°C instead of 990°C as in Example 6. Subsequently, the doped positive electrode active material was further coated with 1500 ppm Al in the same manner as in Example 6. Comparison example 1

[0121] A positive electrode active material doped with 4250 ppm Zr / Mg / Ti was prepared in the same manner as in Example 2, except that the calcination was carried out at a temperature of 920°C. Comparison example 2

[0122] A positive electrode active material doped with 4250 ppm Zr / Mg / Ti was prepared in the same manner as in Example 2, except that the calcination was carried out at a temperature of 950°C. Comparison example 3

[0123] A positive electrode active material doped with 1500 ppm Zr was prepared in the same manner as in Example 4, except that 1500 ppm Zr was used for doping. Comparison example 4

[0124] A positive electrode active material doped with 7500 ppm Zr was prepared in the same manner as in Example 4, except that 7500 ppm Zr was used for doping. Comparison example 5

[0125] A LiNi 0,5 Co 0,3 Mn 0,2 O 2- Positive electrode active material was prepared in the same way as in Example 4, except that no Zr doping treatment was performed. Comparative example 6

[0126] A positive electrode active material doped with 4250 ppm Zr / Mg / Ti was prepared in the same manner as in Example 2, except that a precursor of 11 µm was calcined at a temperature of 920°C. Comparative example 7

[0127] A positive electrode active material doped with 1500 ppm Zr was prepared in the same manner as in Example 4, except that a 12 µm precursor was overcalcined at a temperature of 960°C and doped with 1500 ppm Zr. Experimental Example 1 (Confirmation of crystal grain size by Cu Kα XRD analysis)

[0128] Each of the active materials produced in Examples 2, 4, 6, 8, 10 and 12 was observed and analyzed using a scanning electron microscope (SEM), etc., and the results are presented in the Fig. 1A (Example 2), 1B (Example 4), 1C (Example 6), 1D (Example 8), 1E (Example 10) and 1F (Example 12). Furthermore, the crystal grain sizes of the positive electrode active materials of Examples 1 to 8 and 10 to 12, as well as the comparison examples 1 to 7, were confirmed using an X-ray diffraction analyzer (Bruker AXS D4-Endeavor XRD), and the results are shown in Table 1 below.

[0129] In detail, the crystal grain sizes of the positive electrode active materials were calculated by performing an X-ray diffraction analysis using a Cu source (Cu Kα), obtaining a full width at half maximum (FWHM) from the analysis results, and then inserting the full width at half maximum into the following equation. τ=(K⋅λ) / (β⋅cosθ)

[0130] The above equation is generally known as the Scherrer equation, where K is a form factor, usually 0.9 without dimensions, λ is the X-ray wavelength, β is the full width at half the maximum of a peak with maximum intensity, and θ is an angle of the peak maximum. The corresponding values ​​are substituted into the equation, which calculates the crystal grain size τ. Table 1 Total amount of coating and doping (ppm) Crystal grain size (nm) Example 1 4000 264 Example 2 4250 233 Example 3 5150 207 Example 4 3500 225 Example 5 5500 233 Example 6 5750 229 Example 7 4000 181 Example 8 4250 194 Example 10 3500 194 Example 11 5500 195 Example 12 5750 206 Comparison example 1 4250 151 Comparison example 2 4250 178 Comparison example 3 1500 215 Comparison example 4 7500 239 Comparison example 5 0 232 Comparative example 6 4250 154 Comparative example 7 1500 199

[0131] With reference to the Fig. 1A to 1F confirmed that the active materials produced according to the present invention were manufactured in the form of single particles with a particle size of 3.5 µm to 10 µm.

[0132] Furthermore, with reference to Table 1, it was confirmed that when a precursor with an average particle size of 7 µm or less was used and overcalcination was carried out at 960°C or higher (Examples 1 to 12), the crystal grain size measured by Cu K-α X-ray (X-rα) was relatively large, in the range of 180 nm to 300 nm. In contrast, it was confirmed that when the calcination temperature was lower than 960°C (Comparative Examples 1, 2, and 6), the crystal grain size was less than 180 nm, regardless of the precursor size, indicating that overcalcination did not occur.

[0133] With the same compositions, it is common for the size of the individual particle and the size of the crystal grain within the individual particle to increase with increasing calcination temperature. However, according to the results measured by Cu-Kα X-ray (X-rα) spectroscopy, the sizes of the crystal grains overcalcined at 960°C (Examples 1 to 6) were larger than those of the crystal grains overcalcined at 1010°C (Examples 7 to 12) when their compositions were the same. This is because the patterns resulting from overcalcination at 1010°C (Examples 7 to 12) relate to the degree of aggregation of the individual particles as a function of the calcination temperature and a measuring instrument, and do not deviate from the general trend.

[0134] When individual particles are supercalcined at 990°C (Examples 1 to 6), relatively small individual particles can aggregate together and resemble secondary particles. This means that XRD recognizes the secondary particle-like appearance and identifies the boundaries between the individual particles as grain boundaries, thus determining the individual particle size as a crystal grain size.

[0135] In contrast, when individual particles are supercalcined at 1010°C (Examples 7 to 12), relatively large individual particles can be observed separately while maintaining a distance from each other. This means that XRD detects the individual particles and correctly identifies the crystal grain size within them.

[0136] In other words, those supercalcined at 1010°C (Examples 7 to 12) exhibited smaller crystal grains than those supercalcined at 960°C (Examples 1 to 6), as measured by a Cu-Kα X-ray (X-rα) beam, which is due to limitations of the measuring instrument.

[0137] However, all those supercalcined at 960 °C (Examples 1 to 6) and those at 1010 °C (Examples 7 to 12) exhibited practical crystal grain sizes that were within the error range (± 1%) of the value measured by a Cu-Kα X-ray (X-rα) beam, i.e., within the range of 180 nm to 300 nm. Experimental Example 2 (Evaluation of the crystal structure)

[0138] Example 2 and comparison example 1 were observed using TEM-ASTAR and HR-TEM instruments, respectively. In particular, an HR-TEM image of Example 2 is shown in Fig. 2A, a TEM-ASTAR image of its surface in the Fig. 2B and Fig.2C and a TEM-ASTAR image of its central region in Fig. shown in 2D. Furthermore, it is in Fig. 2E an HR-TEM image of comparison example 1, in Fig. 2F a TEM-ASTAR image of its surface and in Fig. 2G shows a TEM-ASTAR image of the central area of ​​it.

[0139] With reference to the Fig. In samples 2A to 2G, the crystal structure of the surface region can differ depending on the calcination temperature of the precursor, even if the compositions are the same. In particular, comparison example 1, which was not overcalcined, showed a uniform formation of a layered crystal lattice structure from the surface to the center.

[0140] In contrast, the overcalcined example 2 showed different crystal structures at the surface and in the center. More precisely, the overcalcined example 2 had a single particle D50 of 6.8 µm and exhibited a rock salt structure, a spinel structure, or a mixed structure from the surface region down to a depth of 25 nm, with the central region being a layered structure. Experimental Example 2 (Evaluation of Gas Production)

[0141] The positive electrode active materials according to the examples and comparative examples were measured with regard to gas formation, and the results are shown in Tables 2 and 3 below, as well as in the Fig. 2A and Fig. 2B shown.

[0142] In particular, a method for measuring gas formation is as follows.

[0143] Two NCM electrodes (loading amount per electrode area: 1000 mg / cm²) 2Two batteries, charged to a voltage of 4.35 V (based on a full cell), were placed on the base plate of a button cell and secured with a gasket. 80 µl of an electrolyte (DEC REF. (EC / PC / DEC=3 / 1 / 6, VC / PS=0.5 / 1 wt%)) were injected twice under vacuum. Each surface was vacuum-sealed to a thickness of 0.5 cm using a 6.5 x 10 cm aluminum pouch. Vacuum sealing here refers to sealing under monocellular vacuum sealing conditions of 95 kPa / 93 kPa. Subsequently, each battery was stored for two weeks at 60°C in a convection oven, and gas evolution within the battery was measured. Table 2 Type of gas Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Gas formation (µL) H2 0 0 0 0 0 0 CO 586,4 524,8 535,6 597,2222222 402,7 262,2504537 CO2 899,7 891,3 871,1 805,5555556 639,2 412,8856624 CH4 0 0 0 0 0 0 C2H2 0 0 0 0 0 0 C2H4 101,2 118,3 100,8 81,1965812 117,8 0 C2H6 0,0 0,0 0,0 0 0,0 0 C3H6 49,8 50,8 46,8 25,64102564 40,7 26,31578947 C3H8 0,0 0,0 0,0 0 0,0 0 Σ (9 gas types) 1638,6 1582,7 1556,8 1509,6 1203,7 701,4519056 Table 3 Type of gas Example 7 Example 8 Example 9 Example 10 Example 11 Example 12 Gas production (µL) H2 0 0 0 0 0 0 CO 597,2222 222 295,4545 455 504,8638 132 283,7620 579 486,0486 049 95,54140 127 CO2 805,5555 556 795,4545 455 885,2140 078 1020,900 322 612,9612 961 286,6242 038 CH4 0 0 0 0 0 0 C2H2 0 0 0 0 0 0 C2H4 81,19658 12 215,9090 909 97,27626 459 138,2636 656 0 222,9299 363 C2H6 0 0 0 0 0 0 C3H6 25,64102 564 147,7272 727 35,99221 79 52,25080 386 19,80198 02 53,07855 626 C3H8 0 0 0 0 0 0 Σ (9 gas types) 1506,410 256 1454,545 455 1527,237 354 1495,2 1116,111 611 658,1740 977

[0144] Referring to Tables 2 and 3 and the Fig. 3A and Fig.3B Gas formation was significantly reduced when overcalcination was carried out at 990°C or higher (Examples 1 to 12).

[0145] Those supercalcined at 1010°C (Examples 7 to 12) exhibited less gas evolution than those supercalcined at 960°C (Examples 1 to 6). This is attributed to the lower amount of residual lithium and the reduction of cracks within the supercalcined particles and at the particle surface interface. These cracks are areas where side reactions with the electrolyte can occur. By reducing these areas, gas evolution was significantly decreased. Experimental Example 3 (Evaluation of the high-temperature operating characteristics of the battery)

[0146] Each of the positive electrode active materials according to the examples and comparative examples was used to prepare a slurry for the formation of a positive electrode and a lithium secondary battery, and subsequently their high-temperature lifetime properties were evaluated, and the results are presented in the following. Fig. 4A and Fig. 4B shown.

[0147] With reference to the Fig. 4A and Fig.In 4B, the active materials of Examples 1 to 12, all of which exhibited technical combinations of precursor particle overcalcination and limited doping (and coating) contents, showed excellent high-voltage and high-temperature lifetime properties. In contrast, comparison examples 1 and 2, which did not meet the overcalcination conditions, showed a capacity retention of 85% or less after 100 cycles, and the gradient gradually increased. It is therefore expected that the capacity retention will decrease more rapidly after 100 cycles. Comparison examples 3 and 4, where the coating and doping contents did not meet the conditions, showed that the capacity retention decreased, and the gradient gradually decreased with the cycles. It is therefore expected that the capacity retention will decrease further after 100 cycles.Comparative example 5, in which no coating or doping was performed, showed excellent initial capacity retention but a rapid decline after 70 cycles. Comparative example 6, in which no overcalcination occurred and the precursor size was large, showed a rapid decline in initial capacity retention. Comparative example 7, in which overcalcination occurred but the precursor size and coating / doping content did not meet the conditions of the present invention, showed a rapid decline in initial capacity retention and a deterioration of lifetime characteristics with the number of cycles.

[0148] In particular, those overcalcined at 1010°C (Examples 7 to 12) showed excellent capacity retention compared to those overcalcined at 990°C (Examples 1 to 6), which may be related to gas formation, as confirmed in experimental Example 2. Specifically, those overcalcined at 1010°C (Examples 7 to 12) with low cobalt release can improve the electrochemical properties of the battery compared to those overcalcined at 960°C (Examples 1 to 6).

[0149] However, all those that were overcalcined at 960°C (Examples 1 to 6) and those that were overcalcined at 1010°C (Examples 7 to 12) showed a remarkable improvement in capacity retention compared to those of the comparison examples.

[0150] While preferred exemplary embodiments of the present invention have been described in detail, the scope of the present invention is not limited to the foregoing embodiments, and it is evident to the person skilled in the art that various modifications and improvements which utilize the basic concept of the present invention as defined in the appended claims are also included in the scope of the present invention.

[0151] This utility model is a branched version of EP application No. 18 880 300.1. The entire subject matter of that application is incorporated herein by reference. The subject matter defined by the original claims of EP application No. 18 880 300.1 is disclosed again below in preferred embodiments [1] to

[16] : [1] Positive electrode active material for a lithium secondary battery, wherein the positive electrode active material comprises a single particle of a nickel-based lithium composite metal oxide, the single particle containing several crystal grains, each crystal grain having a size of 180 nm to 300 nm as measured by X-ray diffraction analysis using a Cu Kα X-ray beam (X-rα), and 2500 to 6000 ppm of a metal (one or more metals selected from the group consisting of M = Al, Ti, Mg, Zr, W, Y, Sr, Co, F, Si, Mg, Na, Cu, Fe, Ca, S and B) doped into a crystal lattice of the single particle. [2] Positive electrode active material for a lithium secondary battery, the positive electrode active material comprising: a single particle of a nickel-based lithium composite metal oxide, wherein the single particle contains several crystal grains, each crystal grain having a size of 180 nm to 300 nm as measured by Cu-Kα X-ray (X-rα), and a metal (one or more metals selected from the group consisting of M = Al, Ti, Mg, Zr, W, Y, Sr, Co, F, Si, Mg, Na, Cu, Fe, Ca, S and B) doped into a crystal lattice of the single particle;and a metal compound (one or more metals selected from the group consisting of M' = Al, Ti, Mg, Zr, W, Y, Sr, Co, F, Si, Mg, Na, Cu, Fe, Ca, S and B) coated on the surface of the single particle, wherein the total content of the metal doped into the crystal lattice of the single particle and of the metal in the metal compound coated on its surface is 2500 ppm to 6000 ppm. [3] Positive electrode active material for a lithium secondary battery according to [1] or [2], wherein the single particle in its crystal lattice structure includes a surface region with a rock salt structure, a spinel structure or a mixed structure thereof from the surface of the single particle to a depth of 0.13% to 5.26% of the radius of the single particle of the lithium composite metal oxide and a central region with a layered structure from the interface with the surface region to the center of the single particle. [4] Positive electrode active material for a lithium secondary battery according to [1] or [2], wherein the individual particle has an average particle size (D50) of 3.5 µm or more to 8 µm or less. [5] Positive electrode active material for a lithium secondary battery according to [1] or [2], wherein the nickel-based lithium composite metal oxide is represented by the following chemical formula 1 Li a (Ni x Mn y Co z ) O 2+b (1) wherein in the chemical formula 1 0.95≤a≤1.2, 0≤b≤0.02, 0 <x<0,6, 0≤y≤0,4, 0≤z<0 und x+y+z=1. [6] Positive electrode active material for a lithium secondary battery according to [5], wherein in the chemical formula 1 a=1, 0≤b≤0.02, 0.4≤x<0.6, 0.1 <y<0,4, 0,1≤z<0,4 und x+y+z=1. [7] Positive electrode active material for a lithium secondary battery according to [5], wherein the chemical formula 1 LiNi 0,5 Co 0,2 Mn 0,3 O2 or LiNi 0,5Co 0,3 Mn 0,2 O2 is. [8] Positive electrode active material for a lithium secondary battery according to [5], wherein the element (M) is Ti, Mg or Zr. [9] Positive electrode active material for a lithium secondary battery according to [5], wherein the element (M) is Zr.

[10] Method for producing a positive electrode active material for a lithium secondary battery, the method comprising the following steps: Producing an initial mixture comprising a nickel-based lithium composite metal hydroxide particle with a D50 of 8 µm or less, a lithium raw material, and a metal compound (one or more metals selected from the group consisting of M = Al, Ti, Mg, Zr, W, Y, Sr, Co, F, Si, Mg, Na, Cu, Fe, Ca, S, and B); and Calcining the first mixture at a temperature of 960°C or higher, wherein the content of the metal (M) compound is 2500 ppm to 6000 ppm based on the total weight of the first mixture.

[11] Method for producing a positive electrode active material for a lithium secondary battery, the method comprising the following steps: Producing an initial mixture comprising a nickel-based lithium composite metal hydroxide particle with a D50 of 8 µm or less, a lithium raw material and a metal compound (one or more metals selected from the group consisting of M = Al, Ti, Mg, Zr, W, Y, Sr, Co, F, Si, Mg, Na, Cu, Fe, Ca, S and B); Calcining the first mixture at a temperature of 960°C or higher; Preparing a second mixture containing the calcined product of the first mixture and a metal compound (one or more metals selected from the group consisting of M' = Al, Ti, Mg, Zr, W, Y, Sr, Co, F, Si, Mg, Na, Cu, Fe, Ca, S and B); and Calcining the second mixture at a temperature of 350°C to 800°C, wherein the total content of the metal (M) compound and the metal (M') compound, based on the total weight of the first mixture and the second mixture, is 2500 ppm to 6000 ppm.

[12] Method according to

[10] or

[11] , wherein the nickel-based lithium composite metal hydroxide particle is represented by the following chemical formula 2 (No x Mn y Co z ) OH 2+b (2) wherein in the chemical formula 2 0.95≤a≤1.2, 0≤b≤0.02, 0 <x<0,6, 0≤y≤0,4 0≤z<1 und x+y+z+=1.

[13] Method according to

[10] or

[11] , wherein in the step of calcining the first mixture at a temperature of 960°C or higher the single particle of the nickel-based lithium composite metal oxide containing multiple crystal grains is synthesized, and simultaneously the metal (M) of the metal (M) compound is doped into the crystal lattice of the single particle of the lithium composite metal oxide.

[14] Method according to

[11] , wherein the metal (M') of the metal (M') compound and the metal (M) of the metal (M) compound are different.

[15] Positive electrode for a lithium secondary battery, wherein the positive electrode comprises the positive electrode active material according to [1] or [2].

[16] Lithium secondary battery comprising the positive electrode according to

[15] . QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] EP 18 880 300.1

[0151]

Claims

[1] Positive electrode active material for a lithium secondary battery, wherein the positive electrode active material comprises a doped single particle of a nickel-based lithium composite metal oxide, wherein the single particle contains a plurality of crystal grains, each crystal grain having a size of 180 nm to 300 nm as measured by X-ray diffraction analysis with a Cu Kα X-ray beam, and 2500 to 6000 ppm of one or more elements selected from the group consisting of M = Al, Ti, Mg, Zr, W, Y, Sr, Na, Cu, Fe, Ca and B, which are doped into a crystal lattice of the single particle, wherein the single particle contains in its crystal lattice structure a surface region having a rock salt structure, a spinel structure or a mixed structure thereof from the surface of the single particle to a depth of 0.13% to 5.26% of the radius of the single particle of the lithium composite metal oxide and a central region having a layered structure from the interface with the surface region to the center of the single particle, and wherein the single particle has an average particle size D50 of 3.5 µm or more to 8 µm or less. [2] Positive electrode active material for a lithium secondary battery, wherein the positive electrode active material comprises: a doped single particle of a nickel-based lithium composite metal oxide, wherein the single particle contains a plurality of crystal grains, each crystal grain having a size of 180 nm to 300 nm as measured by Cu-Kα X-ray, and one or more elements selected from the group consisting of M = Al, Ti, Mg, Zr, W, Y, Sr, Na, Cu, Fe, Ca, and B, doped into a crystal lattice of the single particle; and a compound coated on the surface of the single particle, wherein the compound comprises one or more elements selected from the group consisting of M' = Al, Ti, Mg, Zr, W, Y, Sr, Co, Na, Cu, Fe, Ca, and B, wherein a total content of the element M doped into the crystal lattice of the single particle and the element M' in the compound coated on its surface is 2500 ppm to 6000 ppm, wherein the single particle contains in its crystal lattice structure a surface region having a rock salt structure, a spinel structure or a mixed structure thereof from the surface of the single particle to a depth of 0.13% to 5.26% of the radius of the single particle of the lithium composite metal oxide and a central region having a layered structure from the interface with the surface region to the center of the single particle, and wherein the single particle has an average particle size D50 of 3.5 µm or more to 8 µm or less. [3] Positive electrode active material for a lithium secondary battery, wherein the positive electrode active material comprises a doped single particle of a nickel-based lithium composite metal oxide, wherein the nickel-based lithium composite metal oxide is represented by the chemical formula 1 below, wherein the single particle contains a plurality of crystal grains, each crystal grain having a size of 180 nm to 300 nm as measured by X-ray diffraction analysis with a Cu Kα X-ray beam, and 2500 to 6000 ppm of one or more elements selected from the group consisting of M = Al, Ti, Mg, Zr, W, Y, Sr, Na, Cu, Fe, Ca and B, which are doped into a crystal lattice of the single particle, wherein the single particle contains in its crystal lattice structure a surface region having a rock salt structure, a spinel structure or a mixed structure thereof from the surface of the single particle to a depth of 0.13% to 5.26% of the radius of the single particle of the lithium composite metal oxide and a central region having a layered structure from the interface with the surface region to the center of the single particle, and wherein the individual particle has an average particle size D50 of 3.5 µm or more to 8 µm or less: Li a (No x Mn y Co z ) O 2+b (1) where in the chemical formula 1 0.95≤a≤1.2, 0≤b≤0.02, 0 <x<0,6, 0≤y≤0,4, 0≤z<1, and x+y+z=1. [4] A positive electrode active material for a lithium secondary battery, the positive electrode active material comprising: a doped single particle of a nickel-based lithium composite metal oxide, wherein the nickel-based lithium composite metal oxide is represented by the chemical formula 1 below, wherein the single particle contains a plurality of crystal grains, each crystal grain having a size of 180 nm to 300 nm as measured by Cu-Kα X-ray, and one or more elements selected from the group consisting of M = Al, Ti, Mg, Zr, W, Y, Sr, Na, Cu, Fe, Ca and B doped into a crystal lattice of the single particle; and a compound coated on the surface of the single particle, wherein the compound comprises one or more elements selected from the group consisting of M' = Al, Ti, Mg, Zr, W, Y, Sr, Co, Na, Cu, Fe, Ca and B, wherein a total content of the element M doped into the crystal lattice of the single particle and the element M' in the compound coated on its surface is 2500 ppm to 6000 ppm, wherein the single particle contains in its crystal lattice structure a surface region having a rock salt structure, a spinel structure or a mixed structure thereof from the surface of the single particle to a depth of 0.13% to 5.26% of the radius of the single particle of the lithium composite metal oxide and a central region having a layered structure from the interface with the surface region to the center of the single particle, and wherein the individual particle has an average particle size D50 of 3.5 µm or more to 8 µm or less: Li a (No x Mn y Co z ) O 2+b (1) where in the chemical formula 1 0.95≤a≤1.2, 0≤b≤0.02, 0 <x<0,6, 0≤y≤0,4, 0≤z<1, and x+y+z=1. [5] The positive electrode active material for a lithium secondary battery according to claim 3 or 4, wherein in the chemical formula 1, a=1, 0≤b≤0.02, 0.4≤x<0.6, 0.1≤y<0.4, 0.1≤z<0.4 and x+y+z=1. [6] A positive electrode active material for a lithium secondary battery according to claim 3 or 4, wherein the chemical formula 1 LiNi 0,5 Co 0,2 Mn 0,3 O2 or LiNi 0,5 Co 0,3 Mn 0,2 O2 is. [7] A positive electrode active material for a lithium secondary battery according to any one of claims 1 to 6, wherein the element M is Ti, Mg or Zr. [8] A positive electrode active material for a lithium secondary battery according to any one of claims 1 to 7, wherein the element M is Zr. [9] A positive electrode for a lithium secondary battery, wherein the positive electrode comprises the positive electrode active material according to any one of claims 1 to 8. [10] A lithium secondary battery comprising the positive electrode according to claim 9.

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