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

Abstract

The present invention relates to a positive electrode active material in the form of a single particle, a method for preparing the same, and a positive electrode and a lithium secondary battery comprising the same, in which the present invention relates to a positive electrode active material comprising a lithium composite transition metal oxide in the form of a single particle having an average particle diameter (D50) of greater than 5.5 [mu] m and equal to or less than 10.0 [mu] m, wherein the lithium composite transition metal oxide contains Al, Y and Zr.

Description

Technical Field

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of priority from Korean Patent Application No. 10-2023-0047005, filed on April 10, 2023, the disclosure of which is incorporated herein by reference. Technical Field

[0003] The present invention relates to a positive electrode active material comprising a lithium composite transition metal oxide in the form of a single particle, a preparation method thereof, and a positive electrode and a lithium secondary battery comprising the positive electrode active material. Background Art

[0004] Recently, in order to solve the structural and thermal stability problems of cathode materials in the form of secondary particles themselves, the development of cathode materials in the form of single particles has been accelerated.

[0005] Specifically, because secondary particle-based cathode materials have a large contact area with the electrolyte when used in lithium secondary batteries, there are problems such as the volume expansion of the battery due to the generation of large amounts of gas. Furthermore, when the amount of nickel in the cathode material is increased to achieve higher capacity, there is also an increased risk of fire. Therefore, there is an increasing demand for the development of single-particle cathode materials.

[0006] For cathode materials in the form of single particles, structural and thermal stability issues are improved compared to those in the form of secondary particles, but stability remains a problem when the amount of nickel in the cathode material is increased for high capacity.

[0007] Therefore, there is a need to develop a positive electrode material in the form of a single particle that can improve the capacity retention and thermal stability of a battery when used in the battery while having excellent stability. Summary of the Invention

[0008] Technical issues

[0009] One aspect of the present invention provides a cathode active material including a lithium composite transition metal oxide in the form of single particles, which can improve the capacity retention and thermal stability of a battery when used in the battery while having excellent structural stability.

[0010] Another aspect of the present invention provides a method for preparing a positive electrode active material.

[0011] Another aspect of the present invention provides a lithium secondary battery in which capacity retention and thermal stability are improved by including a positive electrode active material.

[0012] Technical Solution

[0013] In order to solve the above problems, the present invention provides a positive electrode active material, a method for preparing the positive electrode active material, a positive electrode and a lithium secondary battery.

[0014] (1) The present invention provides a positive electrode active material, wherein the positive electrode active material comprises an average particle size (D 50 ) a lithium composite transition metal oxide in the form of a single particle having a size greater than 5.5 μm and equal to or less than 10.0 μm,

[0015] The lithium composite transition metal oxide contains aluminum (Al), yttrium (Y) and zirconium (Zr).

[0016] (2) The present invention provides the positive electrode active material described in (1) above, wherein the content of Al is 500 ppm to 3,000 ppm based on the total weight of the lithium composite transition metal oxide.

[0017] (3) The present invention provides the positive electrode active material described in (1) or (2) above, wherein the content of Y is 100 ppm to 2,000 ppm based on the total weight of the lithium composite transition metal oxide.

[0018] (4) The present invention provides the positive electrode active material described in any one of (1) to (3) above, wherein the content of Zr is 500 ppm to 5,000 ppm based on the total weight of the lithium composite transition metal oxide.

[0019] (5) The present invention provides the positive electrode active material described in any one of (1) to (4) above, wherein the lithium composite transition metal oxide contains 60 mol % or more of nickel based on the total moles of metals other than lithium.

[0020] (6) The present invention provides the positive electrode active material described in any one of (1) to (5) above, wherein the lithium composite transition metal oxide has a composition represented by Chemical Formula 1.

[0021] [Chemical Formula 1]

[0022] Li x [Ni a Co b Mn c Al d Y e Zr f M1 g ]O 2-y A y

[0023] In Chemical Formula 1,

[0024] M1 is at least one selected from the group consisting of boron (B), titanium (Ti), tungsten (W), niobium (Nb), strontium (Sr), molybdenum (Mo), magnesium (Mg), phosphorus (P), vanadium (V), tantalum (Ta), gallium (Ga), and calcium (Ca),

[0025] A is at least one selected from the group consisting of fluorine (F), chlorine (Cl), bromine (Br), iodine (I), and sulfur (S), and

[0026] 0.9≤x≤1.2,0.6≤a<1.0,0≤b≤0.4,0≤c≤0.4,0 <d≤0.01,0<e≤0.0006,0<f≤0.005,0≤g≤0.2,a+b+c+d+e+f+g=1,0≤y≤0.2。

[0027] (7) The present invention provides the positive electrode active material according to any one of (1) to (6) above, wherein the positive electrode active material further comprises a coating portion containing cobalt (Co) formed on the lithium composite transition metal oxide in the form of a single particle.

[0028] (8) The present invention provides the positive electrode active material described in (7) above, wherein the coating portion further contains Al, Zr or a combination thereof.

[0029] (9) The present invention provides a method for preparing a positive electrode active material, the method comprising the following steps:

[0030] (A) preparing a mixture by mixing a positive electrode active material precursor, a first lithium-containing raw material, an aluminum-containing raw material, an yttrium-containing raw material, and a zirconium-containing raw material, wherein the positive electrode active material precursor is a composite transition metal hydroxide, a composite transition metal oxyhydroxide, or a combination thereof;

[0031] (B) preparing a primary sintered product by primary sintering the mixture at a temperature of 820° C. to 950° C.; and

[0032] (C) A secondary sintered product is prepared by optionally mixing a second lithium-containing raw material with the primary sintered product and performing secondary sintering at a temperature of 700°C to 850°C.

[0033] (10) The present invention provides the method described in (9) above, wherein the method further comprises a step (B') of grinding the primary sintered product before the step (C).

[0034] (11) The present invention provides the method described in (9) or (10) above, wherein the method further comprises a step (C') of grinding the secondary sintered product.

[0035] (12) The present invention provides the method described in any one of (9) to (11) above, further comprising the step (D) of mixing the secondary sintered product and the cobalt-containing coating material and subjecting the mixture to heat treatment.

[0036] (13) The present invention provides the method described in (12) above, wherein when the secondary sintered product and the cobalt-containing coating material are mixed in step (D), an aluminum-containing coating material, a zirconium-containing coating material, or a combination thereof is also mixed.

[0037] (14) The present invention provides the method described in (12) or (13) above, wherein the cobalt-containing coating material is mixed in an amount such that the ratio (B / A) of the number of moles of cobalt contained in the cobalt-containing coating material (B) to the total number of moles of metals other than lithium contained in the secondary sintered product (A) is in the range of 0.01 to 0.03.

[0038] (15) The present invention provides the method described in (13) above, wherein the aluminum-containing coating material is mixed in an amount of 0.03 parts by weight to 0.10 parts by weight based on 100 parts by weight of the secondary sintered product.

[0039] (16) The present invention provides the method described in any one of (12) to (15) above, wherein the heat treatment is performed in an oxygen atmosphere.

[0040] (17) The present invention provides the method according to any one of (12) to (16) above, wherein the heat treatment is performed at a temperature of 600°C to 800°C.

[0041] (18) The present invention provides a positive electrode comprising the positive electrode active material according to any one of (1) to (8) above.

[0042] (19) The present invention provides a lithium secondary battery, comprising:

[0043] The positive electrode described in (18) above;

[0044] negative electrode;

[0045] a separator disposed between the positive electrode and the negative electrode; and

[0046] electrolytes.

[0047] Beneficial effects

[0048] Since the positive electrode active material of the present invention comprises an average particle size (D 50 ) is greater than 5.5 μm and equal to or less than 10.0 μm in the form of a single particle and the lithium composite transition metal oxide contains aluminum (Al), yttrium (Y) and zirconium (Zr), so it can improve the capacity characteristics and life characteristics of the lithium secondary battery.

[0049] Furthermore, according to the method for preparing a positive electrode active material of the present invention, the above-mentioned positive electrode active material can be efficiently prepared. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 Transmission electron microscopy (TEM)-energy dispersive X-ray spectroscopy (EDX)-mapping data of the positive electrode active material of Example 1. DETAILED DESCRIPTION

[0051] Hereinafter, the present invention will be described in more detail to enable a clearer understanding of the present invention.

[0052] It should be understood that the words or terms used in the specification and claims should not be interpreted as the meanings defined in commonly used dictionaries, and it should be further understood that the words or terms should be interpreted as having meanings consistent with their meanings in the relevant technical background and technical spirit of the present invention, based on the principle that the inventor can appropriately define the meanings of the words or terms to best explain the present invention.

[0053] It should be further understood that the terms "include", "comprises" or "has" in this specification clearly indicate the existence of the stated features, numbers, steps, elements or combinations thereof, but do not exclude the existence or addition of one or more other features, numbers, steps, elements or combinations thereof.

[0054] The term “on” in this specification refers not only to a case where one component is directly formed on an upper surface of another component, but also includes a case where an intermediate component may also exist.

[0055] In this specification, the expression "positive electrode active material in the form of a single particle" is a concept in contrast to the positive electrode active material in the form of spherical secondary particles formed by agglomeration of tens to hundreds of primary particles prepared by conventional methods, wherein it refers to a positive electrode active material composed of 10 or fewer primary particles. Specifically, in the present invention, the positive electrode active material in the form of a single particle may be a single particle composed of one primary particle, or may be in the form of secondary particles in which several primary particles are agglomerated.

[0056] The expression “primary particle” refers to the smallest particle unit recognized when the positive electrode active material is observed by a scanning electron microscope, and the expression “secondary particle” refers to a secondary structure formed by agglomeration of a plurality of primary particles.

[0057] In this specification, the expression "average particle size (D 50)” represents the particle size at 50% of the volume cumulative distribution according to the particle size. After the measurement target powder is dispersed in a dispersion medium, the dispersion medium is introduced into a commercially available laser diffraction particle size measuring instrument (e.g., Microtrac S3500), and the particle size distribution is calculated by measuring the difference in the diffraction pattern caused by the particle size when the particles pass through the laser beam, and D 50 It can be measured by calculating the particle diameter at 50% of the volume cumulative distribution of the particle diameters using a measuring instrument.

[0058] positive electrode active material

[0059] The present invention provides a positive electrode active material, wherein the positive electrode active material comprises an average particle size (D 50 The lithium composite transition metal oxide is in the form of single particles having a diameter greater than 5.5 μm and equal to or less than 10.0 μm, wherein the lithium composite transition metal oxide contains aluminum (Al), yttrium (Y), and zirconium (Zr). The lithium composite transition metal oxide may have a layered structure.

[0060] The present inventors have found that the average particle size (D 50 ) in the form of a single-particle lithium composite transition metal oxide with a particle size greater than 5.5 μm and equal to or less than 10.0 μm, and the lithium composite transition metal oxide contains Al, Y, and Zr. This improves the structural stability of the positive electrode active material, reduces cation mixing, and has a large grain size of 3.5 μm to 7.0 μm, thereby improving the capacity characteristics and lifespan characteristics of a lithium secondary battery, thereby completing the present invention. Specifically, the present inventors included Zr and Al as dopants to stabilize the structure of the positive electrode active material in the form of a single particle with a large average particle size. When Al was included as a dopant, there was an issue with the grain size not increasing. This issue was resolved by simultaneously including Y, thereby completing the present invention.

[0061] According to the present invention, the average particle size (D 50 ) is greater than 5.5 μm and equal to or less than 10.0 μm. The average particle size (D 50 ) can be more than 5.5 μm, 6.0 μm, 6.5 μm or more, 7.0 μm, 7.5 μm, 8.0 μm, 8.5 μm, 9.0 μm, 9.5 μm or 10.0 μm or less. 50 ) Within the above range, since the specific surface area is reduced to reduce contact with the electrolyte, the battery including the positive electrode active material according to the present invention has the advantages of high capacity retention, reduced gas generation and excellent thermal stability.

[0062] The average particle size of the lithium composite transition metal oxide (D 50 ) is less than 5.5 μm, because the specific surface area increases due to the small particle size, there are problems such as poor battery capacity retention and thermal stability. 50 ) is larger than 10.0 μm, since the movement distance of lithium in the particle increases, there are problems in that the resistance increases and the charge capacity also decreases.

[0063] According to the present invention, the content of Al may be 500 ppm to 3,000 ppm based on the total weight of the lithium composite transition metal oxide. In this case, since the internal crystal structure of the positive electrode active material is stabilized, the capacity characteristics and resistance characteristics of the battery can be improved.

[0064] According to the present invention, the content of Y may be 100 ppm to 2,000 ppm based on the total weight of the lithium composite transition metal oxide. In this case, since the size of the crystal grains contained in one particle satisfies the range of 3.5 μm to 7.0 μm, the capacity characteristics and resistance characteristics of the battery can be improved.

[0065] According to the present invention, the content of Zr may be 500 ppm to 5,000 ppm based on the total weight of the lithium composite transition metal oxide. In this case, Zr is stably doped in the lithium layer to improve structural stability during lithium insertion and extraction, thereby improving battery life characteristics and resistance characteristics.

[0066] According to the present invention, based on the total molar number of metals other than lithium, the lithium composite transition metal oxide can include more than 60 mol %, specifically more than 80 mol %, more specifically more than 85 mol % of nickel. That is, the lithium composite transition metal oxide can be a high nickel (high Ni) type lithium composite transition metal oxide. In this case, the energy density of the lithium secondary battery can be improved.

[0067] According to the present invention, the lithium composite transition metal oxide may have a composition represented by the following Chemical Formula 1. In this case, the lithium composite transition metal oxide has a layered structure.

[0068] [Chemical Formula 1]

[0069] Li x [Ni a Co b Mn c Al d Y e Zr f M1 g ]O 2-y A y

[0070] In Chemical Formula 1,

[0071] M1 is at least one selected from the following: boron (B), titanium (Ti), tungsten (W), niobium (Nb), strontium (Sr), molybdenum (Mo), magnesium (Mg), phosphorus (P), vanadium (V), tantalum (Ta), gallium (Ga), and calcium (Ca),

[0072] A is at least one selected from the following: fluorine (F), chlorine (Cl), bromine (Br), iodine (I), and sulfur (S), and

[0073] 0.9 ≤ x ≤ 1.2, 0.6 ≤ a < 1.0, 0 ≤ b ≤ 0.4, 0 ≤ c ≤ 0.4, 0 < d ≤ 0.01, 0 < e ≤ 0.0006, 0 < f ≤ 0.005, 0 ≤ g ≤ 0.2, a + b + c + d + e + f + g = 1, 0 ≤ y ≤ 0.2.

[0074] a represents the atomic fraction of nickel among the metal elements in the lithium composite transition metal oxide, where a can satisfy 0.6 ≤ a < 1, 0.8 ≤ a ≤ 0.98, or 0.85 ≤ a ≤ 0.95.

[0075] b represents the atomic fraction of cobalt among the metal elements in the lithium composite transition metal oxide, where b can satisfy 0 ≤ b ≤ 0.4, 0.01 ≤ b ≤ 0.2, or 0.01 ≤ b ≤ 0.15.

[0076] c represents the atomic fraction of manganese among the metal elements in the lithium composite transition metal oxide, where c can satisfy 0 ≤ c ≤ 0.4, 0.01 ≤ c ≤ 0.2, or 0.01 ≤ c ≤ 0.15.

[0077] d represents the atomic fraction of aluminum among the metal elements in the lithium composite transition metal oxide, where d can satisfy 0 < d ≤ 0.01, 0.002 ≤ d ≤ 0.008, or 0.003 ≤ d ≤ 0.006.

[0078] e represents the atomic fraction of yttrium among the metal elements in the lithium composite transition metal oxide, where e can satisfy 0 < e ≤ 0.0006, 0.0001 ≤ e ≤ 0.0005, or 0.0002 ≤ e ≤ 0.0003.

[0079] f represents the atomic fraction of zirconium among the metal elements in the lithium composite transition metal oxide, where f can satisfy 0 < f ≤ 0.005, 0.001 ≤ f ≤ 0.003, or 0.001 ≤ f ≤ 0.002.

[0080] g represents the atomic fraction of the M1 element among the metal elements in the lithium composite transition metal oxide, where g can satisfy 0 ≤ g ≤ 0.2, 0 ≤ g ≤ 0.1, or 0 ≤ g ≤ 0.05.

[0081] According to the present invention, the positive electrode active material may further include a coating portion containing cobalt (Co) formed on a lithium composite transition metal oxide in the form of a single particle. The coating portion may further include Al, Zr, or a combination thereof. In the case where the positive electrode active material further includes a coating portion, the amount of residual lithium by-products can be reduced, the structural stability can be improved to improve the life characteristics and resistance characteristics of the battery, and the amount of gas generated can also be reduced. In this case, the coating portion may have the form of a thin film and may be formed entirely or partially on the lithium composite transition metal oxide.

[0082] The content of Co present in the coating portion may be 0.5 mol % to 3 mol % based on the total moles of metals excluding lithium. In this case, residual lithium by-products may be further reduced, and lifespan characteristics and resistance characteristics may be further improved.

[0083] The content of Al in the coating portion may be 300 ppm to 10,000 ppm based on the total weight of the lithium composite transition metal oxide. In this case, since structural stability is further improved, life characteristics or resistance characteristics may be further improved.

[0084] Method for preparing positive electrode active material

[0085] The present invention provides a method for preparing the above-mentioned positive electrode active material. That is, the positive electrode active material according to the present invention is prepared by the following method for preparing a positive electrode active material.

[0086] The method for preparing a positive electrode active material according to the present invention comprises the following steps:

[0087] (A) preparing a mixture by mixing a positive electrode active material precursor, a first lithium-containing raw material, an aluminum-containing raw material, an yttrium-containing raw material, and a zirconium-containing raw material, wherein the positive electrode active material precursor is a composite transition metal hydroxide, a composite transition metal oxyhydroxide, or a combination thereof;

[0088] (B) preparing a primary sintered product by primary sintering the mixture at a temperature of 820° C. to 950° C.; and

[0089] (C) A secondary sintered product is prepared by optionally mixing a second lithium-containing raw material with the primary sintered product and performing secondary sintering at a temperature of 700°C to 850°C.

[0090] The aluminum-containing raw material may be at least one selected from Al(OH)3, Al2O3, AlCl3, Al(NO3)3, Al2(SO4)3, and Al2S3, specifically at least one selected from Al(OH)3, Al2O3, and Al(NO3)3, more specifically Al(OH)3. The aluminum-containing raw material may be added in an amount of 500 ppm to 3,000 ppm based on the total weight of the positive electrode active material precursor.

[0091] The yttrium-containing raw material may be at least one selected from YCl3, Y2O3, Y(NO3)3, Y(OH)3, YSZ, Y2(SO4)3, and Y2S3, specifically at least one selected from Y2O3 and Y(OH)3, more specifically Y2O3. The yttrium-containing raw material may be added in an amount of 100 ppm to 2,000 ppm based on the total weight of the positive electrode active material precursor.

[0092] The zirconium-containing raw material may be selected from Zr(OH)4, ZrO2, Zr(NO3)4, ZrCl4, ZrS2, Zr(SO4)2 and C8H 12 At least one of O8Zr, specifically at least one selected from Zr(OH)4 and ZrO2, more specifically ZrO2. The amount of the zirconium-containing raw material added may be 500 ppm to 5,000 ppm based on the total weight of the positive electrode active material precursor.

[0093] If the mixture is primarily sintered at a temperature of 820° C. to 950° C., a primary sintered product in the form of a single particle is prepared while primary particles of the positive active material precursor are agglomerated.

[0094] When the primary sintering temperature is within the above range, a primary sintered product in the form of a single particle with stable structure is prepared while the primary particles of the positive electrode active material precursor are agglomerated. When the primary sintering temperature is lower than 820°C, there is a problem of insufficient agglomeration of the primary particles. When the primary sintering temperature is higher than 950°C, there is a problem of unstable structure and low crystallinity of the prepared sintered product.

[0095] According to the present invention, in terms of preventing the lithium transition metal oxide from degenerating into a rock salt structure, the primary sintering can be performed in an oxygen atmosphere.

[0096] According to the present invention, the primary sintering may be performed for 3 to 15 hours, specifically 6 to 12 hours, and more specifically 9 to 12 hours, in terms of agglomerating primary particles and improving crystallinity of the primary sintered product.

[0097] If the primary sintered product is secondarily sintered at a temperature of 700° C. to 850° C., the secondary sintered product is prepared while lithium is intercalated into the primary sintered product. In this case, the secondary sintered product is a lithium composite transition metal oxide in the form of single particles.

[0098] When the secondary sintering temperature is within the above range, there is an advantage in that while lithium is intercalated into the rock salt structure that may be formed on the surface of the primary sintered product due to the high temperature during the primary sintering, the layered structure is restored and lithium by-products are reduced. When the secondary sintering temperature is lower than 700°C, there is a problem of a low lithium intercalation rate due to the low temperature. When the secondary sintering temperature is higher than 850°C, there is a problem that the surface of the primary sintered product degenerates into a rock salt structure due to the high temperature, and lithium by-products remain.

[0099] According to the present invention, in terms of preventing the lithium transition metal oxide from degenerating into a rock salt structure, the secondary sintering may be performed in an oxygen atmosphere.

[0100] According to the present invention, in terms of improving the crystallinity of the internal crystal structure of the positive electrode active material, the secondary sintering may be performed for 3 to 15 hours, specifically 6 to 12 hours, and more specifically 9 to 12 hours.

[0101] The method for preparing a positive electrode active material according to the present invention may further comprise a step (B') of grinding the primary sintered product before step (C). Step (B') may grind the primary sintered product so that the average particle size (D 50 ) is greater than 5.5 μm and equal to or less than 10.0 μm.

[0102] The method for preparing a positive electrode active material according to the present invention may further include a step (C') of grinding the secondary sintered product. In step (C'), the secondary sintered product may be ground so that the average particle size (D 50 ) is greater than 5.5 μm and equal to or less than 10.0 μm.

[0103] The grinding of step (B') and step (C') can be performed using a pin mill, an air classifying mill (ACM), or a jet mill. For the pin mill, grinding can be performed at 18,000 rpm, for the ACM, using equipment from Hosokawa Micron Corporation, classification can be performed at 6,000 rpm and main grinding can be performed at 12,000 rpm, and for the jet mill, using equipment from ZM solution, classification can be performed at 3,500 rpm and grinding can be performed at a pressure of 6 bar.

[0104] The positive electrode active material according to the present invention can be prepared by adding the lithium-containing raw material in two steps, or by adding the lithium-containing raw material in one step. That is, the lithium-containing raw material can be added in its entirety before the primary sintering, or can be added separately before the primary sintering and before the secondary sintering.

[0105] In the case where the lithium-containing raw material is added in two parts, the positive electrode active material according to the present invention can be prepared by, for example, the following operation: sintering the mixture prepared in step (A) at a temperature of 820° C. to 950° C. to obtain a primary sintered product, and grinding the primary sintered product at room temperature to obtain an average particle size (D 50 ) is greater than 5.5 μm and equal to or less than 10.0 μm, and then the second lithium-containing raw material and the ground primary sintered product are mixed and secondarily sintered at a temperature of 700° C. to 850° C. to obtain a secondary sintered product, and the secondary sintered product is ground at room temperature so that the average particle size (D 50 ) is greater than 5.5 μm and equal to or less than 10.0 μm. In this case, in step (A), the first lithium-containing raw material may be mixed so that the ratio (M:Li) of the total number of moles of transition metals (M) contained in the positive electrode active material precursor to the number of moles of lithium (Li) contained in the first lithium-containing raw material is in the range of 1:0.95 to 1:1.02, and in step (C), the second lithium-containing raw material may be mixed so that the ratio (M:Li) of the total number of moles of transition metals (M) contained in the positive electrode active material precursor of step (A) to the number of moles of lithium (Li) contained in the second lithium-containing raw material is in the range of 1:0.01 to 1:1.10.

[0106] In the case of adding the lithium-containing raw material at one time, the positive electrode active material according to the present invention can be prepared by, for example, performing a primary sintering of the mixture prepared in step (A) at a temperature of 820° C. to 950° C., then immediately lowering the temperature to 700° C. to 850° C. (without lowering the temperature to room temperature), performing a secondary sintering at a temperature of 700° C. to 850° C. to obtain a secondary sintered product, and grinding the secondary sintered product at room temperature so that the average particle size (D 50 ) is greater than 5.5 μm and equal to or less than 10.0 μm. In this case, in step (A), the first lithium-containing raw material may be mixed so that the ratio (M:Li) of the total number of moles of transition metals (M) contained in the positive electrode active material precursor to the number of moles of lithium (Li) contained in the first lithium-containing raw material is within a range of 1:1.00 to 1:1.10. In addition, the primary sintering temperature may be higher than the secondary sintering temperature.

[0107] The method for preparing a positive electrode active material according to the present invention may further include a step (D) of mixing the secondary sintered product and the cobalt-containing coating material and performing a heat treatment. In this case, a coating portion containing Co is formed on the secondary sintered product (lithium composite transition metal oxide in the form of a single particle).

[0108] According to the present invention, when the secondary sintered product and the cobalt-containing coating material are mixed in step (D), an aluminum-containing coating material, a zirconium-containing coating material, or a combination thereof may also be mixed. In this case, the coating may contain Al, Zr, or a combination thereof in addition to Co.

[0109] According to the present invention, the cobalt-containing coating material can be mixed in an amount such that the ratio (B / A) of the number of moles of cobalt (B) contained in the cobalt-containing coating material to the total number of moles of metals other than lithium (A) contained in the secondary sintered product is in the range of 0.01 to 0.03. In this case, there is an advantage in that lithium by-products can be controlled in the positive electrode active material preparation process without a washing process.

[0110] The cobalt-containing coating material may be at least one selected from Co(OH)2, Co3O4, CoO, (CH3CO2)2Co, CoCl2 and CoSO4·xH2O, and may specifically be Co(OH)2.

[0111] According to the present invention, the aluminum-containing coating material may be mixed in an amount of 0.03 to 0.10 parts by weight based on 100 parts by weight of the secondary sintered product. In this case, lifespan, resistance, and gas generation may be improved by ensuring structural stability.

[0112] The aluminum-containing coating material may be at least one selected from Al(OH)3, Al2(SO4)3·xH2O, Al2O3, Al(NO3)3·9H2O, AlCl3 and C2H5O4Al, and may specifically be Al(OH)3.

[0113] The zirconium-containing coating material may be selected from Zr(OH)4, ZrO2, Zr(NO3)4, ZrCl4, ZrS2, Zr(SO4)2 and C8H 12 At least one of O8Zr.

[0114] According to the present invention, the heat treatment may be performed in an oxygen atmosphere to prevent the lithium transition metal oxide from degenerating into a rock salt structure.

[0115] According to the present invention, the heat treatment may be performed at a temperature of 600° C. to 800° C., specifically 650° C. to 780° C., more specifically 680° C. to 720° C., so that the coating portion is formed to an appropriate thickness.

[0116] According to the present invention, the heat treatment may be performed for 1 to 10 hours, specifically 2 to 8 hours, and more specifically 3 to 6 hours, to improve the crystallinity of the coating portion.

[0117] positive electrode

[0118] The present invention provides a positive electrode comprising the positive electrode active material.

[0119] The positive electrode may include a positive electrode current collector and a positive electrode active material layer formed on the positive electrode current collector, wherein the positive electrode active material layer may include the positive electrode active material described above.

[0120] The positive electrode current collector may comprise a metal having high conductivity, and is not particularly limited as long as it is non-reactive within the voltage range of the battery and the positive electrode active material layer easily adheres thereto. As the positive electrode current collector, for example: stainless steel, aluminum, nickel, titanium, fired carbon; or aluminum or stainless steel surface-treated with one of carbon, nickel, titanium, silver, etc. may be used. In addition, the positive electrode current collector may generally have a thickness of 3 μm to 500 μm, and fine concavo-convexities may be formed on the surface of the current collector to improve the adhesion of the positive electrode active material. For example, the positive electrode current collector may be used in various shapes such as a film, a sheet, a foil, a mesh, a porous body, a foam, a non-woven fabric, and the like.

[0121] If desired, the positive electrode active material layer may optionally contain a conductive material and a binder in addition to the positive electrode active material. In this case, the content of the positive electrode active material may be 80% to 99% by weight, more specifically 85% to 98.5% by weight, based on the total weight of the positive electrode active material layer. Excellent capacity characteristics can be obtained within this range.

[0122] The conductive material is used to provide conductivity to the electrode, wherein any conductive material can be used without particular limitation, as long as it has suitable electronic conductivity and does not cause adverse chemical changes in the battery. Specific examples of the conductive material may be the following substances: graphite such as natural graphite or artificial graphite; carbon materials such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black and carbon fiber; powder or fiber of metals such as copper, nickel, aluminum and silver; conductive tubes such as carbon nanotubes; conductive whiskers such as zinc oxide whiskers and potassium titanate whiskers; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives, and any one thereof or a mixture of two or more thereof may be used. The content of the conductive material may be 0.1 wt % to 15 wt % based on the total weight of the positive electrode active material layer.

[0123] The binder improves the adhesion between the positive electrode active material particles and the adhesion between the positive electrode active material and the collector. Specific examples of the binder can be: polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-to-HFP), polyvinyl alcohol, polyacrylonitrile, polymethyl methacrylate, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene propylene diene monomer rubber (EPDM), sulfonated EPDM, styrene-butadiene rubber (SBR), fluororubber, polyacrylic acid and its hydrogen is replaced by lithium (Li), sodium (Na) or calcium (Ca) polymer or its various copolymers, and any one thereof or a mixture of two or more thereof can be used. Based on the gross weight of the positive electrode active material layer, the content of the binder can be 0.1 wt % to 15 wt %.

[0124] In addition to using the above-mentioned positive electrode active material, the positive electrode can be prepared according to a typical method for preparing a positive electrode. Specifically, a positive electrode active material layer-forming composition prepared by dissolving or dispersing the positive electrode active material and an optional binder and a conductive material in a solvent is applied to a positive electrode current collector, and then the coated positive electrode current collector can be dried and rolled to prepare a positive electrode, or the positive electrode active material layer-forming composition can be cast on a separate support, and then the film separated from the support is laminated on the positive electrode current collector to prepare a positive electrode.

[0125] The solvent may be a solvent commonly used in the art, and may include dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), dimethylformamide (DMF), acetone or water, and any one thereof or a mixture of two or more thereof may be used. If the solvent can dissolve or disperse the positive electrode active material, the conductive material, the binder and the dispersant, and can be made to have a viscosity that can provide excellent thickness uniformity during subsequent coating for preparing the positive electrode, the amount of the solvent used may be sufficient.

[0126] lithium secondary batteries

[0127] The present invention provides a lithium secondary battery, comprising:

[0128] positive electrode;

[0129] negative electrode;

[0130] a separator disposed between the positive electrode and the negative electrode; and

[0131] electrolytes.

[0132] The lithium secondary battery may further optionally include a battery container that houses an electrode assembly including a positive electrode, a negative electrode, and a separator, and a sealing member that seals the battery container.

[0133] The negative electrode may include a negative electrode current collector and a negative electrode active material layer disposed on the negative electrode current collector.

[0134] There are no particular limitations on the negative electrode current collector, as long as it has high conductivity without causing adverse chemical changes in the battery. Examples include copper, stainless steel, aluminum, nickel, titanium, and calcined carbon; copper or stainless steel surface-treated with one of carbon, nickel, titanium, and silver; and aluminum-cadmium alloys. Furthermore, the negative electrode current collector can typically have a thickness of 3 to 500 μm. Similar to the positive electrode current collector, fine irregularities can be formed on the surface of the current collector to improve adhesion of the negative electrode active material. For example, the negative electrode current collector can be used in various forms, such as films, sheets, foils, meshes, porous bodies, foams, and non-woven fabrics.

[0135] The negative electrode active material layer may optionally contain a binder and a conductive material in addition to the negative electrode active material.

[0136] Compounds that can reversibly intercalate and deintercalate lithium can be used as negative electrode active materials. Specific examples of negative electrode active materials may include the following: carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fibers, and amorphous carbon; (semi-)metallic materials that can form alloys with lithium, such as silicon (Si), aluminum (Al), tin (Sn), lead (Pb), zinc (Zn), bismuth (Bi), indium (In), magnesium (Mg), gallium (Ga), cadmium (Cd), Si alloys, Sn alloys, or Al alloys; (semi-)metallic oxides that can be doped and dedoped with lithium, such as SiO β (0<β<2), SnO2, vanadium oxide and lithium vanadium oxide; or a composite material comprising a (semi)metallic material and a carbonaceous material such as a Si-C composite material or a Sn-C composite material, and any one thereof or a mixture of two or more thereof can be used. In addition, a metallic lithium film can be used as a negative electrode active material. In addition, both low-crystalline carbon and high-crystalline carbon can be used as carbon materials. Typical examples of low-crystalline carbon can be soft carbon and hard carbon, and typical examples of high-crystalline carbon can be irregular, planar, flaky, spherical or fibrous natural graphite or artificial graphite, condensed graphite, pyrolytic carbon, mesophase pitch-type carbon fibers, mesophase carbon microbeads, mesophase pitch, and high-temperature sintered carbon such as coke derived from petroleum or coal tar pitch. The content of the negative electrode active material can be 80% by weight to 99% by weight based on the total weight of the negative electrode active material layer.

[0137] The binder of the negative electrode active material layer is a component that helps to bind the conductive material, the active material and the current collector, wherein the binder is generally added in an amount of 0.1% to 10% by weight based on the total weight of the negative electrode active material layer. Examples of binders may be polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene propylene diene monomer (EPDM), sulfonated EPDM, styrene-butadiene rubber, acrylonitrile-butadiene rubber, fluororubber and various copolymers thereof.

[0138] The conductive material of the negative electrode active material layer is a component used to further improve the conductivity of the negative electrode active material. The conductive material can be added in an amount of 10% by weight or less, preferably 5% by weight or less, based on the total weight of the negative electrode active material layer. There are no particular limitations on the conductive material, as long as it has conductivity and does not cause adverse chemical changes in the battery. For example, conductive materials such as the following can be used: graphite such as natural graphite or artificial graphite; carbon black such as acetylene black, Ketjen black, channel black, furnace black, lamp black, and thermal black; conductive fibers such as carbon fibers or metal fibers; fluorocarbons; metal powders such as aluminum powder and nickel powder; conductive whiskers such as zinc oxide whiskers and potassium titanate whiskers; conductive metal oxides such as titanium oxide; or polyphenylene derivatives.

[0139] The negative electrode can be prepared by coating a negative electrode active material layer-forming composition prepared by dissolving or dispersing an optional binder and a conductive material and a negative electrode active material in a solvent on a negative electrode collector and drying the coated negative electrode collector, or can be prepared by casting the negative electrode active material layer-forming composition on a separate support and then laminating the film separated from the support on the negative electrode collector.

[0140] The separator separates the negative electrode and the positive electrode and provides a path for the movement of lithium ions, wherein any separator can be used as the separator without particular limitation, as long as it is commonly used in lithium secondary batteries, and in particular, a separator having high moisture retention capacity for electrolytes and low resistance to electrolyte ion transfer can be used. Specifically, it is possible to use: a porous polymer film, for example, a porous polymer film prepared from 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 having two or more layers thereof. In addition, a typical porous non-woven fabric can be used, for example, a non-woven fabric formed of a high melting point glass fiber or a polyethylene terephthalate fiber. In addition, a coated separator comprising a ceramic component or a polymer material can be used to ensure heat resistance or mechanical strength, and a separator having a single-layer or multilayer structure can be optionally used.

[0141] The electrolyte may include an organic liquid electrolyte, an inorganic liquid electrolyte, a solid polymer electrolyte, a gel polymer electrolyte, a solid inorganic electrolyte or a molten inorganic electrolyte that can be used to prepare a lithium secondary battery, but the present invention is not limited thereto. As a specific example, the electrolyte may include an organic solvent and a lithium salt.

[0142] Any organic solvent can be used as the organic solvent without particular limitation, as long as it can be used as a medium through which ions participating in the electrochemical reaction of the battery can move. Specifically, the following substances can be used as the organic solvent: 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 dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), ethylene carbonate (EC) and propylene carbonate (PC); alcohol solvents such as ethanol and isopropanol; nitrile such as R-CN (wherein R is a linear, branched or cyclic C2-C20 hydrocarbon group and can contain a double bond, an aromatic ring or an ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolanes; or sulfolane. Among these solvents, carbonate solvents are preferred, and more preferred are mixtures of cyclic carbonates (e.g., ethylene carbonate or propylene carbonate) with low viscosity linear carbonate compounds (e.g., ethyl methyl carbonate, dimethyl carbonate or diethyl carbonate) that have high ionic conductivity and high dielectric constant and can improve the charge / discharge performance of the battery.

[0143] The lithium salt can be used without particular limitation, as long as it is a compound capable of providing lithium ions used in lithium secondary batteries. Specifically, the anion of the lithium salt can be at least one selected from the following: - 、Cl - Br - , I - 、NO3 - 、N(CN)2 - 、BF4 - CF3CF2SO3 - 、(CF3SO2)2N - 、(FSO2)2N - CF3CF2(CF3)2CO - 、(CF3SO2)2CH - 、(SF5)3C - 、(CF3SO2)3C - CF3(CF2)7SO3 - CF3CO2 - 、CH3CO2 - 、SCN - and (CF3CF2SO2)2N- , and the following substances can be used as the lithium salt: LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAlO4, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2, LiCl, LiI or LiB(C2O4)2. The lithium salt can be used in a concentration range of 0.1 M to 2.0 M. If the concentration of the lithium salt is included in the above range, since the electrolyte can have appropriate conductivity and viscosity, excellent performance of the electrolyte can be obtained, and lithium ions can be effectively moved.

[0144] In order to improve the life characteristics of the battery, suppress the reduction of the battery capacity and improve the discharge capacity of the battery, the electrolyte may further include at least one additive in addition to the above-mentioned electrolyte components, such as a halogenated alkylene carbonate compound such as difluoroethylene carbonate, pyridine, triethyl phosphite, triethanolamine, cyclic ether, ethylenediamine, (condensed) glycol dimethyl ether, hexamethylphosphoric triamide, nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinones, N, N-substituted imidazolidines, ethylene glycol dialkyl ethers, ammonium salts, pyrroles, 2-methoxyethanol or aluminum chloride. In this case, the content of the additive may be 0.1% to 5% by weight based on the total weight of the electrolyte.

[0145] Since the lithium secondary battery including the positive electrode active material according to the present invention has excellent capacity characteristics and life characteristics, the lithium secondary battery is suitable for: portable devices such as mobile phones, notebook computers and digital cameras; and electric vehicles such as hybrid electric vehicles (HEVs) and electric vehicles (EVs).

[0146] The shape of the lithium secondary battery of the present invention is not particularly limited, but a cylindrical type using a can, a prismatic type, a pouch type, or a coin type can be used.

[0147] The lithium secondary battery according to the present invention can be used not only in a battery cell used as a power source for small devices but also as a unit battery in a medium or large battery module including a plurality of battery cells.

[0148] Therefore, a battery module including a lithium secondary battery as a unit battery and a battery pack including the battery module are provided.

[0149] The battery module or battery pack can be used as a power source for at least one of the following medium to large devices: power tools; electric vehicles, including electric vehicles (EVs), hybrid electric vehicles, and plug-in hybrid electric vehicles (PHEVs); or power storage systems.

[0150] Preferred embodiments

[0151] Hereinafter, examples of the present invention will be described in detail in a manner that can be easily implemented by those skilled in the art. However, the present invention can be embodied in many different forms and should not be construed as limited to the examples set forth herein.

[0152] Examples and Comparative Examples

[0153] Example 1

[0154] A composite transition metal hydroxide (composition: Ni) in the form of secondary particles formed by agglomerating tens to hundreds of primary particles was prepared so that the ratio of the total molar number of transition metals (Ni+Co+Mn) contained in the composite transition metal hydroxide to the molar number of lithium (Li) contained in LiOH ((Ni+Co+Mn):Li) was 1:0.98. 0.885 Co 0.035 Mn 0.08 (OH)2, average particle size (D 50 ): 6.2 μm) and LiOH were mixed, and Al(OH)3 (KC DAEJOO), Y2O3 (NeoPerformance Materials), and ZrO2 (R&F) were added thereto in amounts of 1,400 ppm, 1,000 ppm, and 1,500 ppm, respectively, based on the total weight of the composite transition metal hydroxide and mixed to prepare a mixture.

[0155] The mixture was subjected to primary sintering at 830° C. for 6 hours to obtain a primary sintered product, and the primary sintered product was ground at room temperature so that the average particle size (D 50 ) is 5.8 μm.

[0156] The ground primary sintered product and LiOH were mixed so that the ratio of the total molar number of transition metals (Ni+Co+Mn) contained in the composite transition metal hydroxide to the molar number of lithium (Li) contained in LiOH ((Ni+Co+Mn):Li) was 1:0.04, and the secondary sintered product was obtained by secondary sintering at 760°C for 9 hours. The secondary sintered product was ground at room temperature to obtain an average particle size (D 50 ) is a lithium composite transition metal oxide in the form of a single particle of 5.8 μm (composition: LiNi 0.87836 Co 0.03493 Mn 0.07985 Al 0.00499 Y 0.00027 Zr 0.0016 O2).

[0157] After uniformly mixing the lithium composite transition metal oxide in the form of a single particle with Co(OH)2 (Huayou Cobalt) and Al(OH)3 (KC DAEJOO), a heat treatment was performed at a temperature of 700°C for 5 hours in an oxygen atmosphere to prepare a positive electrode active material (composition: LiNi) in which a coating portion containing Co and Al was formed on the lithium composite transition metal oxide in the form of a single particle. 0.85761 Co 0.05489 Mn 0.07978 Al 0.00586 Y 0.00027 Zr 0.00159 In this case, Co(OH)2 is mixed in such an amount that the ratio (B / A) of the number of moles (B) of cobalt contained in the cobalt-containing coating material to the total number of moles (A) of metals other than lithium contained in the lithium composite transition metal oxide in the form of a single particle is 0.02, and Al(OH)3 is mixed in such an amount that it is 0.05 parts by weight based on 100 parts by weight of the lithium composite transition metal oxide in the form of a single particle.

[0158] Example 2

[0159] A composite transition metal hydroxide (composition: Ni) in the form of secondary particles formed by agglomerating tens to hundreds of primary particles was prepared so that the ratio of the total molar number of transition metals (Ni+Co+Mn) contained in the composite transition metal hydroxide to the molar number of lithium (Li) contained in LiOH ((Ni+Co+Mn):Li) was 1:0.98. 0.885 Co 0.035 Mn 0.08 (OH)2, average particle size (D 50 ): 6.2 μm) and LiOH were mixed, and Al(OH)3 (KC DAEJOO), Y2O3 (NeoPerformance Materials), and ZrO2 (R&F) were added thereto in amounts of 1,400 ppm, 2,000 ppm, and 1,500 ppm, respectively, based on the total weight of the composite transition metal hydroxide and mixed to prepare a mixture.

[0160] The mixture was subjected to primary sintering at 830° C. for 6 hours to obtain a primary sintered product, and the primary sintered product was ground at room temperature so that the average particle size (D 50 ) is 5.8 μm.

[0161] The ground primary sintered product and LiOH were mixed so that the ratio of the total molar number of transition metals (Ni+Co+Mn) contained in the composite transition metal hydroxide to the molar number of lithium (Li) contained in LiOH ((Ni+Co+Mn):Li) was 1:0.04, and the secondary sintered product was obtained by secondary sintering at 760°C for 9 hours. The secondary sintered product was ground at room temperature to obtain an average particle size (D 50 ) is a lithium composite transition metal oxide in the form of a single particle of 5.8 μm (composition: LiNi 0.87813 Co 0.03492 Mn 0.07983 Al 0.00499 Y 0.00054 Zr 0.00159 O2).

[0162] After uniformly mixing the lithium composite transition metal oxide in the form of a single particle with Co(OH)2 (Huayou Cobalt) and Al(OH)3 (KC DAEJOO), a heat treatment was performed at a temperature of 700°C for 5 hours in an oxygen atmosphere to prepare a positive electrode active material (composition: LiNi) in which a coating portion containing Co and Al was formed on the lithium composite transition metal oxide in the form of a single particle. 0.85738 Co 0.05487 Mn 0.07976 Al 0.00586 Y 0.00054 Zr 0.00159 In this case, Co(OH)2 is mixed in such an amount that the ratio (B / A) of the number of moles (B) of cobalt contained in the cobalt-containing coating material to the total number of moles (A) of metals other than lithium contained in the lithium composite transition metal oxide in the form of a single particle is 0.02, and Al(OH)3 is mixed in such an amount that it is 0.05 parts by weight based on 100 parts by weight of the lithium composite transition metal oxide in the form of a single particle.

[0163] Example 3

[0164] A composite transition metal hydroxide (composition: Ni) in the form of secondary particles formed by agglomerating tens to hundreds of primary particles was prepared so that the ratio of the total molar number of transition metals (Ni+Co+Mn) contained in the composite transition metal hydroxide to the molar number of lithium (Li) contained in LiOH ((Ni+Co+Mn):Li) was 1:0.98. 0.885 Co 0.035 Mn 0.08 (OH)2, average particle size (D 50): 6.2 μm) and LiOH were mixed, and Al(OH)3 (KC DAEJOO), Y2O3 (NeoPerformance Materials) and ZrO2 (R&F) were added thereto in amounts of 2,800 ppm, 1,000 ppm and 1,500 ppm, respectively, based on the total weight of the composite transition metal hydroxide and mixed to prepare a mixture.

[0165] The mixture was subjected to primary sintering at 830° C. for 6 hours to obtain a primary sintered product, and the primary sintered product was ground at room temperature so that the average particle size (D 50 ) is 5.8 μm.

[0166] The ground primary sintered product and LiOH were mixed so that the ratio of the total molar number of transition metals (Ni+Co+Mn) contained in the composite transition metal hydroxide to the molar number of lithium (Li) contained in LiOH ((Ni+Co+Mn):Li) was 1:0.04, and the secondary sintered product was obtained by secondary sintering at 760°C for 9 hours. The secondary sintered product was ground at room temperature to obtain an average particle size (D 50 ) is a lithium composite transition metal oxide in the form of a single particle of 5.8 μm (composition: LiNi 0.87338 Co 0.03493 Mn 0.07985 Al 0.00998 Y 0.00027 Zr 0.00159 O2).

[0167] After uniformly mixing the lithium composite transition metal oxide in the form of a single particle with Co(OH)2 (Huayou Cobalt) and Al(OH)3 (KC DAEJOO), a heat treatment was performed at a temperature of 700°C for 5 hours in an oxygen atmosphere to prepare a positive electrode active material (composition: LiNi) in which a coating portion containing Co and Al was formed on the lithium composite transition metal oxide in the form of a single particle. 0.85262 Co 0.05489 Mn 0.07978 Al 0.01085 Y 0.00027 Zr 0.00159 In this case, Co(OH)2 is mixed in such an amount that the ratio (B / A) of the number of moles (B) of cobalt contained in the cobalt-containing coating material to the total number of moles (A) of metals other than lithium contained in the lithium composite transition metal oxide in the form of a single particle is 0.02, and Al(OH)3 is mixed in such an amount that it is 0.05 parts by weight based on 100 parts by weight of the lithium composite transition metal oxide in the form of a single particle.

[0168] Example 4

[0169] A composite transition metal hydroxide (composition: Ni) in the form of secondary particles formed by agglomerating tens to hundreds of primary particles was prepared so that the ratio of the total molar number of transition metals (Ni+Co+Mn) contained in the composite transition metal hydroxide to the molar number of lithium (Li) contained in LiOH ((Ni+Co+Mn):Li) was 1:0.98. 0.885 Co 0.035 Mn 0.08 (OH)2, average particle size (D 50 ): 6.2 μm) and LiOH were mixed, and Al(OH)3 (KC DAEJOO), Y2O3 (NeoPerformance Materials), and ZrO2 (R&F) were added thereto in amounts of 1,400 ppm, 1,000 ppm, and 3,500 ppm, respectively, based on the total weight of the composite transition metal hydroxide and mixed to prepare a mixture.

[0170] The mixture was subjected to primary sintering at 830° C. for 6 hours to obtain a primary sintered product, and the primary sintered product was ground at room temperature so that the average particle size (D 50 ) is 5.8 μm.

[0171] The ground primary sintered product and LiOH were mixed so that the ratio of the total molar number of transition metals (Ni+Co+Mn) contained in the composite transition metal hydroxide to the molar number of lithium (Li) contained in LiOH ((Ni+Co+Mn):Li) was 1:0.04, and the secondary sintered product was obtained by secondary sintering at 760°C for 9 hours. The secondary sintered product was ground at room temperature to obtain an average particle size (D 50 ) is a lithium composite transition metal oxide in the form of a single particle of 5.8 μm (composition: LiNi 0.87651 Co 0.03486 Mn 0.07968 Al 0.00498 Y 0.00027 Zr 0.0037 O2).

[0172] After uniformly mixing the lithium composite transition metal oxide in the form of a single particle with Co(OH)2 (Huayou Cobalt) and Al(OH)3 (KC DAEJOO), a heat treatment was performed at a temperature of 700°C for 5 hours in an oxygen atmosphere to prepare a positive electrode active material (composition: LiNi) in which a coating portion containing Co and Al was formed on the lithium composite transition metal oxide in the form of a single particle. 0.85576 Co 0.05481 Mn 0.07961 Al 0.00585 Y 0.00027 Zr0.0037 In this case, Co(OH)2 is mixed in such an amount that the ratio (B / A) of the number of moles (B) of cobalt contained in the cobalt-containing coating material to the total number of moles (A) of metals other than lithium contained in the lithium composite transition metal oxide in the form of a single particle is 0.02, and Al(OH)3 is mixed in such an amount that it is 0.05 parts by weight based on 100 parts by weight of the lithium composite transition metal oxide in the form of a single particle.

[0173] Example 5

[0174] A composite transition metal hydroxide (composition: Ni) in the form of secondary particles formed by agglomerating tens to hundreds of primary particles was prepared so that the ratio of the total molar number of transition metals (Ni+Co+Mn) contained in the composite transition metal hydroxide to the molar number of lithium (Li) contained in LiOH ((Ni+Co+Mn):Li) was 1:0.98. 0.885 Co 0.035 Mn 0.08 (OH)2, average particle size (D 50 ): 6.2 μm) and LiOH were mixed, and Al(OH)3 (KC DAEJOO), Y2O3 (NeoPerformance Materials), and ZrO2 (R&F) were added thereto in amounts of 1,400 ppm, 1,000 ppm, and 1,500 ppm, respectively, based on the total weight of the composite transition metal hydroxide and mixed to prepare a mixture.

[0175] The mixture was subjected to primary sintering at 830° C. for 6 hours to obtain a primary sintered product, and the primary sintered product was ground at room temperature so that the average particle size (D 50 ) is 6.8 μm.

[0176] The ground primary sintered product and LiOH were mixed so that the ratio of the total molar number of transition metals (Ni+Co+Mn) contained in the composite transition metal hydroxide to the molar number of lithium (Li) contained in LiOH ((Ni+Co+Mn):Li) was 1:0.04, and the secondary sintered product was obtained by secondary sintering at 760°C for 9 hours. The secondary sintered product was ground at room temperature to obtain an average particle size (D 50 ) is a lithium composite transition metal oxide in the form of a single particle of 6.8 μm (composition: LiNi 0.87836 Co 0.03493 Mn 0.07985 Al 0.00499 Y 0.00027 Zr 0.0016 O2).

[0177] After uniformly mixing the lithium composite transition metal oxide in the form of a single particle with Co(OH)2 (Huayou Cobalt) and Al(OH)3 (KC DAEJOO), a heat treatment was performed at a temperature of 700°C for 5 hours in an oxygen atmosphere to prepare a positive electrode active material (composition: LiNi) in which a coating portion containing Co and Al was formed on the lithium composite transition metal oxide in the form of a single particle. 0.85761 Co 0.05489 Mn 0.07978 Al 0.00586 Y 0.00027 Zr 0.00159 In this case, Co(OH)2 is mixed in such an amount that the ratio (B / A) of the number of moles (B) of cobalt contained in the cobalt-containing coating material to the total number of moles (A) of metals other than lithium contained in the lithium composite transition metal oxide in the form of a single particle is 0.02, and Al(OH)3 is mixed in such an amount that it is 0.05 parts by weight based on 100 parts by weight of the lithium composite transition metal oxide in the form of a single particle.

[0178] Comparative Example 1

[0179] A composite transition metal hydroxide (composition: Ni) in the form of secondary particles formed by agglomerating tens to hundreds of primary particles was prepared so that the ratio of the total molar number of transition metals (Ni+Co+Mn) contained in the composite transition metal hydroxide to the molar number of lithium (Li) contained in LiOH ((Ni+Co+Mn):Li) was 1:0.98. 0.885 Co 0.035 Mn 0.08 (OH)2, average particle size (D 50 ): 6.2 μm) and LiOH were mixed, and Al(OH) 3 (KC DAEJOO) and ZrO 2 (R&F) were added thereto in amounts of 1,400 ppm and 1,500 ppm, respectively, based on the total weight of the composite transition metal hydroxide and mixed to prepare a mixture.

[0180] The mixture was subjected to primary sintering at 830° C. for 6 hours to obtain a primary sintered product, and the primary sintered product was ground at room temperature so that the average particle size (D 50 ) is 5.8 μm.

[0181] The ground primary sintered product and LiOH were mixed so that the ratio of the total molar number of transition metals (Ni+Co+Mn) contained in the composite transition metal hydroxide to the molar number of lithium (Li) contained in LiOH ((Ni+Co+Mn):Li) was 1:0.04, and the secondary sintered product was obtained by secondary sintering at 760°C for 9 hours. The secondary sintered product was ground at room temperature to obtain an average particle size (D50 ) is a lithium composite transition metal oxide in the form of a single particle of 5.8 μm (composition: LiNi 0.8786 Co 0.03494 Mn 0.07987 Al 0.00499 Zr 0.0016 O2).

[0182] After uniformly mixing the lithium composite transition metal oxide in the form of a single particle with Co(OH)2 (Huayou Cobalt) and Al(OH)3 (KC DAEJOO), a heat treatment was performed at a temperature of 700°C for 5 hours in an oxygen atmosphere to prepare a positive electrode active material (composition: LiNi) in which a coating portion containing Co and Al was formed on the lithium composite transition metal oxide in the form of a single particle. 0.85784 Co 0.0549 Mn 0.0798 Al 0.00586 Zr 0.0016 In this case, Co(OH)2 is mixed in such an amount that the ratio (B / A) of the number of moles (B) of cobalt contained in the cobalt-containing coating material to the total number of moles (A) of metals other than lithium contained in the lithium composite transition metal oxide in the form of a single particle is 0.02, and Al(OH)3 is mixed in such an amount that it is 0.05 parts by weight based on 100 parts by weight of the lithium composite transition metal oxide in the form of a single particle.

[0183] Comparative Example 2

[0184] A composite transition metal hydroxide (composition: Ni) in the form of secondary particles formed by agglomerating tens to hundreds of primary particles was prepared so that the ratio of the total molar number of transition metals (Ni+Co+Mn) contained in the composite transition metal hydroxide to the molar number of lithium (Li) contained in LiOH ((Ni+Co+Mn):Li) was 1:0.98. 0.885 Co 0.035 Mn 0.08 (OH)2, average particle size (D 50 ): 6.2 μm) and LiOH were mixed, and Y2O3 (Neo Performance Materials) and ZrO2 (R&F) were added thereto in amounts of 1,000 ppm and 1,500 ppm, respectively, based on the total weight of the composite transition metal hydroxide and mixed to prepare a mixture.

[0185] The mixture was subjected to primary sintering at 830° C. for 6 hours to obtain a primary sintered product, and the primary sintered product was ground at room temperature so that the average particle size (D 50 ) is 5.8 μm.

[0186] The ground primary sintered product and LiOH were mixed so that the ratio of the total molar number of transition metals (Ni+Co+Mn) contained in the composite transition metal hydroxide to the molar number of lithium (Li) contained in LiOH ((Ni+Co+Mn):Li) was 1:0.04, and the secondary sintered product was obtained by secondary sintering at 760°C for 9 hours. The secondary sintered product was ground at room temperature to obtain an average particle size (D 50 ) is a lithium composite transition metal oxide in the form of a single particle of 5.8 μm (composition: LiNi 0.88336 Co 0.03493 Mn 0.07985 Y 0.00027 Zr 0.00159 O2).

[0187] After uniformly mixing the lithium composite transition metal oxide in the form of a single particle with Co(OH)2 (Huayou Cobalt) and Al(OH)3 (KC DAEJOO), a heat treatment was performed at a temperature of 700°C for 5 hours in an oxygen atmosphere to prepare a positive electrode active material (composition: LiNi) in which a coating portion containing Co and Al was formed on the lithium composite transition metal oxide in the form of a single particle. 0.86259 Co 0.05489 Mn 0.07978 Al 0.00088 Y 0.00027 Zr 0.00159 In this case, Co(OH)2 is mixed in such an amount that the ratio (B / A) of the number of moles (B) of cobalt contained in the cobalt-containing coating material to the total number of moles (A) of metals other than lithium contained in the lithium composite transition metal oxide in the form of a single particle is 0.02, and Al(OH)3 is mixed in such an amount that it is 0.05 parts by weight based on 100 parts by weight of the lithium composite transition metal oxide in the form of a single particle.

[0188] Comparative Example 3

[0189] A composite transition metal hydroxide (composition: Ni) in the form of secondary particles formed by agglomerating tens to hundreds of primary particles was prepared so that the ratio of the total molar number of transition metals (Ni+Co+Mn) contained in the composite transition metal hydroxide to the molar number of lithium (Li) contained in LiOH ((Ni+Co+Mn):Li) was 1:0.98. 0.885 Co 0.035 Mn 0.08 (OH)2, average particle size (D 50): 6.2 μm) and LiOH were mixed, and Al(OH) 3 (KC DAEJOO) and Y 2 O 3 (Neo Performance Materials) were added thereto in amounts of 1,400 ppm and 1,000 ppm, respectively, based on the total weight of the composite transition metal hydroxide and mixed to prepare a mixture.

[0190] The mixture was subjected to primary sintering at 830° C. for 6 hours to obtain a primary sintered product, and the primary sintered product was ground at room temperature so that the average particle size (D 50 ) is 5.8 μm.

[0191] The ground primary sintered product and LiOH were mixed so that the ratio of the total molar number of transition metals (Ni+Co+Mn) contained in the composite transition metal hydroxide to the molar number of lithium (Li) contained in LiOH ((Ni+Co+Mn):Li) was 1:0.04, and the secondary sintered product was obtained by secondary sintering at 760°C for 9 hours. The secondary sintered product was ground at room temperature to obtain an average particle size (D 50 ) is a lithium composite transition metal oxide in the form of a single particle of 5.8 μm (composition: LiNi 0.87976 Co 0.03499 Mn 0.07998 Al 0.005 Y 0.00027 O2).

[0192] After uniformly mixing the lithium composite transition metal oxide in the form of a single particle with Co(OH)2 (Huayou Cobalt) and Al(OH)3 (KC DAEJOO), a heat treatment was performed at a temperature of 700°C for 5 hours in an oxygen atmosphere to prepare a positive electrode active material (composition: LiNi) in which a coating portion containing Co and Al was formed on the lithium composite transition metal oxide in the form of a single particle. 0.85901 Co 0.05494 Mn 0.07991 Al 0.00587 Y 0.00027 In this case, Co(OH)2 is mixed in such an amount that the ratio (B / A) of the number of moles (B) of cobalt contained in the cobalt-containing coating material to the total number of moles (A) of metals other than lithium contained in the lithium composite transition metal oxide in the form of a single particle is 0.02, and Al(OH)3 is mixed in such an amount that it is 0.05 parts by weight based on 100 parts by weight of the lithium composite transition metal oxide in the form of a single particle.

[0193] Comparative Example 4

[0194] A composite transition metal hydroxide (composition: Ni) in the form of secondary particles formed by agglomerating tens to hundreds of primary particles was prepared so that the ratio of the total molar number of transition metals (Ni+Co+Mn) contained in the composite transition metal hydroxide to the molar number of lithium (Li) contained in LiOH ((Ni+Co+Mn):Li) was 1:0.98. 0.885 Co 0.035 Mn 0.08 (OH)2, average particle size (D 50 ): 4.19 μm) and LiOH were mixed, and Al(OH)3 (KC DAEJOO), Y2O3 (NeoPerformance Materials), and ZrO2 (R&F) were added thereto in amounts of 1,400 ppm, 1,000 ppm, and 1,500 ppm, respectively, based on the total weight of the composite transition metal hydroxide and mixed to prepare a mixture.

[0195] The mixture was subjected to primary sintering at 830° C. for 6 hours to obtain a primary sintered product, and the primary sintered product was ground at room temperature so that the average particle size (D 50 ) is 3.8 μm.

[0196] The ground primary sintered product and LiOH were mixed so that the ratio of the total molar number of transition metals (Ni+Co+Mn) contained in the composite transition metal hydroxide to the molar number of lithium (Li) contained in LiOH ((Ni+Co+Mn):Li) was 1:0.04, and the secondary sintered product was obtained by secondary sintering at 760°C for 9 hours. The secondary sintered product was ground at room temperature to obtain an average particle size (D 50 ) is a lithium composite transition metal oxide in the form of a single particle of 3.8 μm (composition: LiNi 0.87836 Co 0.03493 Mn 0.07985 Al 0.00499 Y 0.00027 Zr 0.0016 O2).

[0197] After uniformly mixing the lithium composite transition metal oxide in the form of a single particle with Co(OH)2 (Huayou Cobalt) and Al(OH)3 (KC DAEJOO), a heat treatment was performed at a temperature of 700°C for 5 hours in an oxygen atmosphere to prepare a positive electrode active material (composition: LiNi) in which a coating portion containing Co and Al was formed on the lithium composite transition metal oxide in the form of a single particle. 0.85761 Co 0.05489 Mn 0.07978 Al 0.00586 Y 0.00027 Zr 0.00159In this case, Co(OH)2 is mixed in such an amount that the ratio (B / A) of the number of moles (B) of cobalt contained in the cobalt-containing coating material to the total number of moles (A) of metals other than lithium contained in the lithium composite transition metal oxide in the form of a single particle is 0.02, and Al(OH)3 is mixed in such an amount that it is 0.05 parts by weight based on 100 parts by weight of the lithium composite transition metal oxide in the form of a single particle.

[0198] Comparative Example 5

[0199] A composite transition metal hydroxide (composition: Ni) in the form of secondary particles formed by agglomerating tens to hundreds of primary particles was prepared so that the ratio of the total molar number of transition metals (Ni+Co+Mn) contained in the composite transition metal hydroxide to the molar number of lithium (Li) contained in LiOH ((Ni+Co+Mn):Li) was 1:0.98. 0.885 Co 0.035 Mn 0.08 (OH)2, average particle size (D 50 ): 9 μm) and LiOH were mixed, and Al(OH)3 (KC DAEJOO), Y2O3 (NeoPerformance Materials) and ZrO2 (R&F) were added thereto in amounts of 1,400 ppm, 1,000 ppm and 1,500 ppm, respectively, based on the total weight of the composite transition metal hydroxide and mixed to prepare a mixture.

[0200] The mixture was subjected to primary sintering at 830° C. for 6 hours to obtain a primary sintered product, and the primary sintered product was ground at room temperature so that the average particle size (D 50 ) is 11 μm.

[0201] The ground primary sintered product and LiOH were mixed so that the ratio of the total molar number of transition metals (Ni+Co+Mn) contained in the composite transition metal hydroxide to the molar number of lithium (Li) contained in LiOH ((Ni+Co+Mn):Li) was 1:0.04, and the secondary sintered product was obtained by secondary sintering at 760°C for 9 hours. The secondary sintered product was ground at room temperature to obtain an average particle size (D 50 ) is a lithium composite transition metal oxide in the form of a single particle of 11 μm (composition: LiNi 0.87836 Co 0.03493 Mn 0.07985 Al 0.00499 Y 0.00027 Zr 0.0016 O2).

[0202] After uniformly mixing the lithium composite transition metal oxide in the form of a single particle with Co(OH)2 (Huayou Cobalt) and Al(OH)3 (KC DAEJOO), a heat treatment was performed at a temperature of 700°C for 5 hours in an oxygen atmosphere to prepare a positive electrode active material (composition: LiNi) in which a coating portion containing Co and Al was formed on the lithium composite transition metal oxide in the form of a single particle. 0.85761 Co 0.05489 Mn 0.07978 Al 0.00586 Y 0.00027 Zr 0.00159 In this case, Co(OH)2 is mixed in such an amount that the ratio (B / A) of the number of moles (B) of cobalt contained in the cobalt-containing coating material to the total number of moles (A) of metals other than lithium contained in the lithium composite transition metal oxide in the form of a single particle is 0.02, and Al(OH)3 is mixed in such an amount that it is 0.05 parts by weight based on 100 parts by weight of the lithium composite transition metal oxide in the form of a single particle.

[0203] Experimental example

[0204] Experimental Example 1: Analysis of positive electrode active materials

[0205] In order to confirm how the dopants Al, Y, and Zr exist in the positive electrode active material prepared in Example 1 and how the coating portion containing Co and Al is formed, TEM (transmission electron microscope) (Titan Buved G2 600-300) energy dispersive X-ray spectroscopy (EDX)-mapping was used for analysis, and the TEM EDX mapping data are shown in FIG. Figure 1 middle.

[0206] refer to Figure 1 For the positive electrode active material prepared in Example 1, it can be confirmed that the dopants Al, Y and Zr have no concentration gradient in the particles and are uniformly distributed, and it can be confirmed that the coating portion containing Co and Al is formed in the form of a thin film on the particle surface.

[0207] Experimental Example 2: Confirmation of the amount of residual lithium in the secondary sintered product

[0208] The amount of residual lithium present in each of the secondary sintered products prepared in Examples 1 to 5 and Comparative Examples 1 to 5, ie, the amount of Li 2 CO 3 and LiOH, was confirmed by the following method.

[0209] Specifically, 5 g of each of the secondary sintered products prepared in Examples 1 to 5 and Comparative Examples 1 to 5 was added to 100 g of distilled water, mixed for 5 minutes, and then filtered. After filtration, the amount of Li2CO3 and LiOH dissolved in the distilled water was measured by titration (using 0.1N HCl) using a pH meter, and the results are shown in Table 1.

[0210]

[0211] Experimental Example 3: Evaluation of Capacity Retention

[0212] The positive electrode active materials prepared in Examples 1 to 5 and Comparative Examples 1 to 5, a carbon black conductive material, and a polyvinylidene fluoride (PVDF) binder were mixed in an N-methylpyrrolidone (NMP) solvent at a ratio of 96:2:2 to prepare a positive electrode slurry. One surface of an aluminum current collector was coated with the positive electrode slurry, dried at 150°C, and then rolled to prepare a positive electrode.

[0213] A lithium metal electrode was used as the negative electrode. An electrode assembly was prepared by placing a porous polyethylene separator between the positive and negative electrodes. The electrode assembly was placed in a battery case, and an electrolyte was then injected into the case to prepare each half-cell. In this case, the electrolyte was prepared by dissolving 1.0 M LiPF6 in an organic solvent containing ethylene carbonate (EC): ethyl methyl carbonate (EMC): diethyl carbonate (DEC) in a volume ratio of 3:4:3.

[0214] For each half-cell thus prepared, the capacity of the lithium secondary battery was measured by repeating charge and discharge cycles 50 times at 45°C in the range of 3.0 V to 4.25 V at a constant current of 0.33C, and the percentage of the discharge capacity at the 50th cycle relative to the discharge capacity at the 1st cycle was defined as the capacity retention rate, and the capacity retention rates are shown in Table 2 below.

[0215]

[0216] Experimental Example 4: Evaluation of thermal stability

[0217] After each half-cell of Example 1 and Comparative Example 4 prepared in Experimental Example 3 was charged to 4.25 V (termination current: 0.05C) at a constant current of 0.2C in a constant current / constant voltage (CC / CV) mode at 25°C, the battery was disassembled in a charged state to wash the positive electrode with DMC, and the heat flow was measured while increasing the temperature at 10°C / min using a differential scanning calorimeter (DSC), and the total calorie value, onset (peak start) temperature, main peak temperature and instantaneous maximum calorie value obtained are shown in Table 3 below.

[0218]

[0219] Referring to Table 1, for the positive electrode active materials of Examples 1 to 5, it can be confirmed that the amount of residual lithium, that is, the total amount of Li 2 CO 3 and LiOH is reduced.

[0220] Referring to Tables 2 and 3, it can be confirmed that the batteries including the cathode active materials of Examples 1 to 5 respectively have excellent life characteristics due to high capacity retention rates, and it can be confirmed that the battery including the cathode active material of Example 1 has excellent thermal stability.

[0221] On the contrary, because the positive electrode active material of Comparative Example 1 does not contain Y, it has a grain growth problem, from which it can be confirmed that the capacity retention rate of the battery containing it is reduced. In addition, because the positive electrode active material of Comparative Example 2 does not contain Al, it is in the form of increased cation mixing due to many defects, from which it can be confirmed that the capacity retention rate of the battery containing it is reduced. In addition, because the positive electrode active material of Comparative Example 3 does not contain Zr to keep the structure stable, it can be confirmed that the capacity retention rate is reduced. In addition, because the average particle size of the positive electrode active material of Comparative Example 4 is small, it can be confirmed that the capacity retention rate of the battery is low and the thermal stability is also poor. In addition, because the average particle size of the positive electrode active material of Comparative Example 5 is large, the movement distance of lithium in the particles is increased, from which it can be confirmed that the capacity retention rate of the battery is reduced. In addition, although not shown in Table 2, it is confirmed that the resistance characteristics of the positive electrode active material of Comparative Example 5 are poor (initial resistance and resistance increase rate are high).

Claims

1. A positive electrode active material comprising an average particle size (D 50 ) a lithium composite transition metal oxide in the form of a single particle having a size greater than 5.5 μm and equal to or less than 10.0 μm, The lithium composite transition metal oxide contains Al, Y and Zr. 2 . The positive electrode active material according to claim 1 , wherein the content of Al is 500 ppm to 3,000 ppm based on the total weight of the lithium composite transition metal oxide. 3 . The positive electrode active material according to claim 1 , wherein the content of Y is 100 ppm to 2,000 ppm based on the total weight of the lithium composite transition metal oxide. 4 . The positive electrode active material according to claim 1 , wherein the content of Zr is 500 ppm to 5,000 ppm based on the total weight of the lithium composite transition metal oxide. 5 . The positive electrode active material according to claim 1 , wherein the lithium composite transition metal oxide contains 60 mol % or more of nickel based on the total moles of metals other than lithium.

6. The positive electrode active material according to claim 1, wherein the lithium composite transition metal oxide has a composition represented by Chemical Formula 1: [Chemical Formula 1] Li x [Ni a Co b Mr c Al d Y e Zr f M1 g ]O 2-y A y Wherein, in Chemical Formula 1, M1 is at least one selected from B, Ti, W, Nb, Sr, Mo, Mg, P, V, Ta, Ga and Ca, A is at least one selected from F, Cl, Br, I and S, and 0.9≤x≤1.2,0.6≤a<1.0,0≤b≤0.4,0≤c≤0.4,0 <d≤0.01,0<e≤0.0006,0<f≤0.005,0≤g≤0.2,a+b+c+d+e+f+g=1,0≤y≤0.2。 7 . The positive electrode active material according to claim 1 , further comprising a coating portion containing Co formed on the lithium composite transition metal oxide in the form of a single particle. 8 . The positive electrode active material according to claim 7 , wherein the coating part further comprises Al, Zr, or a combination thereof.

9. A method for preparing the positive electrode active material according to claim 1, comprising the following steps: (A) preparing a mixture by mixing a positive electrode active material precursor, a first lithium-containing raw material, an aluminum-containing raw material, an yttrium-containing raw material, and a zirconium-containing raw material, wherein the positive electrode active material precursor is a composite transition metal hydroxide, a composite transition metal oxyhydroxide, or a combination thereof; (B) preparing a primary sintered product by primary sintering the mixture at a temperature of 820° C. to 950° C.; and (C) preparing a secondary sintered product by optionally mixing a second lithium-containing raw material with the primary sintered product and performing secondary sintering at a temperature of 700°C to 850°C. 10 . The method according to claim 9 , further comprising a step (B′) of grinding the primary sintered product before step (C).

11. The method according to claim 9, further comprising a step (C') of grinding the secondary sintered product. 12 . The method according to claim 9 , further comprising the step (D) of mixing the secondary sintered product and a cobalt-containing coating material and subjecting the mixture to heat treatment.

13. The method according to claim 12, wherein: When the secondary sintered product and the cobalt-containing coating material are mixed in step (D), an aluminum-containing coating material, a zirconium-containing coating material, or a combination thereof are also mixed.

14. The method according to claim 12, wherein the cobalt-containing coating material is mixed in an amount such that a ratio (B / A) of the number of moles (B) of cobalt contained in the cobalt-containing coating material to the total number of moles (A) of metals other than lithium contained in the secondary sintered product is in a range of 0.01 to 0.

03. 15 . The method according to claim 13 , wherein the aluminum-containing coating material is mixed in an amount of 0.03 parts by weight to 0.10 parts by weight based on 100 parts by weight of the secondary sintered product. The method according to claim 12 , wherein the heat treatment is performed in an oxygen atmosphere.

17. The method according to claim 12, wherein the heat treatment is performed at a temperature of 600°C to 800°C. 18 . A positive electrode comprising the positive electrode active material according to claim 1 .

19. A lithium secondary battery, comprising: The positive electrode according to claim 18; negative electrode; A separator provided between the positive electrode and the negative electrode; and electrolytes.

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