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 in which the particle size distribution is hardly changed even after rolling due to small particle deformation, a method for preparing the same, and a positive electrode and a lithium secondary battery comprising the same, and more particularly, to a positive electrode active material in the form of a single particle in which the particle size distribution is hardly changed even after rolling, a method for preparing the same, and a positive electrode and a lithium secondary battery comprising the same. The positive electrode active material includes a lithium composite transition metal oxide in a single particle form, where the lithium composite transition metal oxide includes Ni, Co, Mn, Al, and M1, where M1 is at least one selected from the group consisting of Zr, Y, K, Sr, and Ba, and satisfies mathematical formula 1. [mathematical formula 1] | 1-alpha / beta | < = 0.1 in mathematical formula 1, alpha is a value of (D90-D10) / D50, and beta is a value of (D90-D10) / D50 after rolling the positive electrode active material at 1,000 kgf / cm2 to 7,000 kgf / cm2.

Description

Technical Field

[0001] Cross-references to related applications This application claims priority to Korean Patent Application No. 10-2023-0051887, filed on April 20, 2023, the disclosure of which is incorporated herein by reference. Technical Field

[0002] This invention relates to a positive electrode active material, a method for preparing the same, and a positive electrode and a lithium secondary battery comprising the positive electrode active material. In particular, it relates to a positive electrode active material, a method for preparing the same, and a positive electrode and a lithium secondary battery comprising the positive electrode active material, wherein the positive electrode active material comprises a single-particle form of a lithium composite transition metal oxide that can improve battery performance. Background Technology

[0003] With the recent technological advancements and increasing demands for mobile devices and electric vehicles, the demand for secondary batteries as an energy source has increased significantly. Among these secondary batteries, lithium-ion batteries, characterized by high energy density, high voltage, long cycle life, and low self-discharge rate, have been commercialized and are widely used.

[0004] As positive electrode active materials for lithium-ion secondary batteries, lithium transition metal oxides have been developed, such as lithium cobalt oxides like LiCoO2, lithium nickel oxides like LiNiO2, lithium manganese oxides like LiMnO2 or LiMn2O4, and lithium iron phosphate oxides like LiFePO4. More recently, lithium composite transition metal oxides containing two or more transition metals, such as Li[Ni], have also been developed. a Co b Mn c O2, Li[Ni a Co b Al c ]O2 and Li[Ni a Co b Mn c Al d O2 is widely used.

[0005] Currently developed lithium composite transition metal oxides containing two or more transition metals are typically prepared as spherical secondary particles with tens to hundreds of primary particles aggregated within them. Recently, to address the structural and thermal stability issues of these secondary particle-form cathode active materials, the development of single-particle-form cathode active materials is being accelerated. Specifically, the problem with secondary particle-form cathode active materials is that when used in lithium-ion batteries, the battery volume expands due to the generation of large amounts of gas. Furthermore, increasing the amount of nickel in the cathode material to achieve higher capacity increases the risk of fire. Therefore, the demand for developing single-particle-form cathode active materials with excellent stability is increasing.

[0006] Therefore, there is a need to develop a single-particle positive electrode active material that, while possessing excellent stability, can improve various battery performance characteristics when used in batteries. Summary of the Invention

[0007] Technical issues One aspect of the present invention provides a positive electrode active material comprising a lithium composite transition metal oxide in the form of single particles, wherein the positive electrode active material has excellent structural stability and can improve the capacity, initial efficiency, lifespan and resistance of the battery when used in a battery.

[0008] Another aspect of the present invention provides a method for preparing a positive electrode active material.

[0009] Another aspect of the present invention provides a lithium secondary battery in which performance is improved by including a positive electrode active material.

[0010] Technical solution To address the aforementioned problems, this invention provides a positive electrode active material, a method for preparing the positive electrode active material, a positive electrode, and a lithium secondary battery.

[0011] (1) The present invention provides a positive electrode active material, wherein the positive electrode active material comprises a lithium composite transition metal oxide in the form of single particles. The lithium complex transition metal oxides include nickel (Ni), cobalt (Co), manganese (Mn), aluminum (Al), and M1. Where M1 is selected from at least one of zirconium (Zr), yttrium (Y), potassium (K), strontium (Sr) and barium (Ba), and satisfies mathematical formula 1.

[0012] [Mathematical Expression 1] |1-α / β|≤0.1 In mathematical formula 1, α is (D) 90 -D 10 ) / D 50The value, and β represents the amount of positive electrode active material at 1,000 kgf / cm². 2 Up to 7,000 kgf / cm 2 (D) after rolling 90 -D 10 ) / D 50 The value of .

[0013] (2) The present invention provides the positive electrode active material described in (1) above, wherein the lithium composite transition metal oxide has a layered structure.

[0014] (3) The present invention provides the positive electrode active material described in (1) or (2) above, wherein the lithium composite transition metal oxide has an average particle size (D) of 3.00 μm to 8.00 μm. 50 ).

[0015] (4) The present invention provides a positive electrode active material according to any one of (1) to (3) above, wherein the lithium composite transition metal oxide is doped with Al and M1.

[0016] (5) The present invention provides a positive electrode active material according to any one of (1) to (4) above, wherein the content of Al is from 500 ppm to 3,000 ppm based on the total weight of lithium complex transition metal oxide.

[0017] (6) The present invention provides a positive electrode active material according to any one of (1) to (5) above, wherein the content of M1 is from 100 ppm to 5,000 ppm based on the total weight of lithium composite transition metal oxide.

[0018] (7) The present invention provides a positive electrode active material according to any one of (1) to (6) above, wherein the lithium composite transition metal oxide contains more than 60 mol% nickel based on the total molar number of metals other than lithium.

[0019] (8) The present invention provides a positive electrode active material according to any one of (1) to (7) above, wherein the lithium composite transition metal oxide has a composition represented by chemical formula 1.

[0020] [Chemical Formula 1] Li x [Ni a Co b Mn c Al d M1 e M2 f O 2-y A y In chemical formula 1, M1 is selected from at least one of the following: Zr, Y, K, Sr, and Ba. M2 is selected from at least one of the following: boron (B), Ba, cerium (Ce), chromium (Cr), magnesium (Mg), vanadium (V), titanium (Ti), iron (Fe), zinc (Zn), silicon (Si), niobium (Nb), gallium (Ga), tin (Sn), molybdenum (Mo), tungsten (W), and phosphorus (P). A is selected from at least one of the following: fluorine (F), chlorine (Cl), bromine (Br), iodine (I), and sulfur (S), and 1.0 ≤ x ≤ 1.3, 0.6 ≤ a < 1, 0.0 <b≤0.4,0.0<c≤0.4,0.0<d≤0.01,0.0<e≤0.005,0.0≤f≤0.2,a+b+c+d+e+f=1,0≤y≤0.2。

[0021] (9) The present invention provides a method for preparing a positive electrode active material, the method comprising the following steps: (A) A mixture is prepared by mixing a positive electrode active material precursor containing Ni, Co and Mn, an aluminum-containing raw material, an M1-containing raw material and a first lithium-containing raw material; (B) A one-time sintered product is prepared by sintering the mixture once at a temperature of 800°C to 950°C; and (C) A secondary sintered product is prepared by mixing a second lithium-containing raw material with a primary sintered product and then performing a secondary sintering at a temperature of 680°C to 850°C. Where M1 is selected from at least one of the following: Zr, Y, K, Sr and Ba, and Based on the total weight of the positive electrode active material precursor, the mixing amount of the raw material containing M1 is from 100 ppm to 5,000 ppm.

[0022] (10) The present invention provides the method described in (9) above, wherein the method further includes a step (B') of grinding the sintered product once before step (C).

[0023] (11) The present invention provides the method described in (9) or (10) above, wherein the method further includes the step of grinding the secondary sintering product (C').

[0024] (12) The present invention provides a positive electrode comprising any one of the positive electrode active materials described in (1) to (8) above.

[0025] (13) The present invention provides a lithium secondary battery, the lithium secondary battery comprising: The positive electrode described in (12) above; negative electrode; A diaphragm positioned between the positive and negative electrodes; and Electrolytes.

[0026] Beneficial effects Because the positive electrode active material of the present invention comprises a lithium composite transition metal oxide in the form of single particles, wherein the lithium composite transition metal oxide comprises nickel (Ni), cobalt (Co), manganese (Mn), aluminum (Al) and M1, wherein M1 is at least one selected from zirconium (Zr), yttrium (Y), potassium (K), strontium (Sr) and barium (Ba), and satisfies mathematical formula 1 described in this specification, the particle size distribution hardly changes even after rolling due to small particle deformation. Therefore, the positive electrode active material of the present invention can improve the capacity, initial efficiency, lifespan and resistance of lithium secondary batteries.

[0027] Furthermore, the above-mentioned positive electrode active material can be effectively prepared using the method for preparing positive electrode active material according to the present invention. Detailed Implementation

[0028] The invention will be described in more detail below so that it can be more clearly understood. It should be understood that the words or terms used in the specification and claims should not be interpreted as having the meanings defined in common dictionaries, and should be further understood to be interpreted as having meanings consistent with their meanings in the relevant technical field and technical spirit of the invention, based on the principle that the inventors can appropriately define the meanings of the words or terms to best interpret the invention.

[0030] It should be further understood that the terms "comprising," "including," or "having" in this specification specify the presence of the stated features, number, steps, elements, or combinations thereof, but do not exclude the presence or addition of one or more other features, number, steps, elements, or combinations thereof.

[0031] The term "on top of" in this specification refers not only to the case where one component is formed directly on the upper surface of another component, but also to the case where there may be intermediate components.

[0032] In this specification, the term "single-particle positive electrode active material" is used in contrast to positive electrode active materials prepared by conventional methods, which are formed by the aggregation of tens to hundreds of primary particles into spherical secondary particles. Specifically, it refers to positive electrode active materials composed of fewer than 10 primary particles. In this invention, the single-particle positive electrode active material can be a single particle composed of a single primary particle, or it can be a secondary particle form in which several primary particles are aggregated.

[0033] The term "primary particle" refers to the smallest particle unit identified when observing positive electrode active materials using a scanning electron microscope, while the term "secondary particle" refers to a secondary structure formed by the aggregation of multiple primary particles.

[0034] In this specification, the term "average particle size (D)" is used. 50 ")" indicates the particle size at 50% of the volumetric cumulative distribution based on particle size. After dispersing the target powder in a dispersion medium, the dispersion medium is introduced into a commercially available laser diffraction particle size analyzer (e.g., Microtrac S3500). The particle size distribution is calculated by measuring the difference in the diffraction pattern caused by particle size as the particles pass through the laser beam, and D 50 The particle size can be measured by using a measuring instrument to calculate the particle size at 50% of the volumetric cumulative distribution based on the particle size.

[0035] Positive electrode active material This invention provides a positive electrode active material comprising a lithium composite transition metal oxide in single-particle form, wherein the lithium composite transition metal oxide comprises nickel (Ni), cobalt (Co), manganese (Mn), aluminum (Al), and M1, wherein M1 is at least one selected from zirconium (Zr), yttrium (Y), potassium (K), strontium (Sr), and barium (Ba), and satisfies the following mathematical formula 1. The lithium composite transition metal oxide may have a layered structure.

[0036] [Mathematical Expression 1] |1-α / β|≤0.1 In mathematical formula 1, α is (D) 90 -D 10 ) / D 50 The value, and β represents the amount of positive electrode active material at 1,000 kgf / cm². 2 Up to 7,000 kgf / cm 2 (D) after rolling 90 -D 10 ) / D 50 The value of .

[0037] The inventors have discovered that when the positive electrode active material comprises a single-particle lithium composite transition metal oxide, wherein the lithium composite transition metal oxide contains Ni, Co, Mn, Al, and M1, and satisfies Mathematical Formula 1, the positive electrode active material can improve various performance characteristics of lithium secondary batteries due to its small particle deformation, thus completing this invention. Specifically, the inventors have discovered that when the lithium composite transition metal oxide mainly contains Al, Al can improve the performance of lithium secondary batteries by increasing structural stability by replacing some transition metal ions in the crystal structure. Furthermore, when the lithium composite transition metal oxide also contains M1, it can provide a positive electrode active material with excellent particle strength and large grain size. When the positive electrode active material does not contain Al, its low thermal and structural stability causes deformation of the oxide lattice during charge and discharge cycles, resulting in problems with battery performance. Additionally, when the positive electrode active material does not contain M1, it fails to satisfy Mathematical Formula 1, resulting in low particle strength and / or small grain size.

[0038] According to the present invention, M1, selected from at least one of Zr, Y, K, Sr and Ba, is an element capable of improving the crystallinity and single-particle formation of the positive electrode active material, wherein it can specifically be selected from two or more of Zr, Y, K, Sr and Ba, more specifically from Zr and Y.

[0039] According to the present invention, the value of mathematical formula 1 can be 0.1 or less, specifically 0.1, 0.09, 0.08, 0.07, 0.06, or 0.05 or less. This means that the positive electrode active material has excellent particle strength, resulting in minimal deformation even when pressure is applied to it. When the value of mathematical formula 1 is within the aforementioned range, the battery containing the positive electrode active material can exhibit excellent capacity, initial efficiency, lifetime, or resistivity performance. When the value of mathematical formula 1 is greater than 0.1, the low particle strength increases particle breakage in the electrode, potentially leading to poor lifetime and resistivity performance.

[0040] According to the present invention, lithium composite transition metal oxides can have an average particle size (D) of 3.00 μm to 8.00 μm. 50 The average particle size (D) of lithium composite transition metal oxides 50 Specifically, the particle size can be 3.00 μm or larger than 3.50 μm, or 7.00 μm, 7.50 μm or smaller than 8.00 μm. The average particle size (D) of lithium composite transition metal oxides... 50 Within the above-mentioned range, electrochemical performance can be optimized.

[0041] According to the present invention, the lithium composite transition metal oxide can be doped with Al and M1. In this case, that is, when the lithium composite transition metal oxide contains Al and M1 as dopants, the capacity, initial efficiency, lifetime and resistivity of the lithium secondary battery can be further improved because the structural stability of the positive electrode active material is further improved, the cation mixing is reduced and the grain size is large.

[0042] In terms of increasing grain size while further improving the structural stability of single-particle positive electrode active materials with small average particle size, lithium composite transition metal oxides can be doped with Al, Zr and Y.

[0043] According to the present invention, the Al content can be from 500 ppm to 3,000 ppm based on the total weight of the lithium complex transition metal oxide. In this case, the capacity and resistance performance of the battery can be improved because the internal crystal structure of the positive electrode active material is stabilized.

[0044] According to the present invention, the content of M1 can be from 100 ppm to 5,000 ppm based on the total weight of the lithium complex transition metal oxide.

[0045] When M1 is Y and Zr, the Y content can be from 100 ppm to 2,000 ppm based on the total weight of the lithium complex transition metal oxide, and the Zr content can be from 500 ppm to 5,000 ppm based on the total weight of the lithium complex transition metal oxide. When the amount of Y is within the above range, the capacity and lifespan performance of the battery can be improved because the grain size contained in a single particle is large. Furthermore, when the amount of Zr is within the above range, the particle strength is excellent because Zr is stably doped in the lithium layer, thereby improving the structural stability during lithium insertion and extraction. As a result, the lifespan and resistance performance of the battery can be improved.

[0046] According to the present invention, based on the total molar number of metals other than lithium, the lithium complex transition metal oxide may contain 60 mol% or more, specifically 80 mol% or more, and more specifically 85 mol% or more of nickel. That is, the lithium complex transition metal oxide may be a high-nickel (high-Ni) lithium complex transition metal oxide. In this case, the energy density of the lithium secondary battery can be improved.

[0047] According to the present invention, the lithium complex transition metal oxide can have a composition represented by the following chemical formula 1. In this case, the lithium complex transition metal oxide has a layered structure.

[0048] [Chemical Formula 1] Li x [Ni a Co b Mnc Al d M1 e M2 f O 2-y A y In chemical formula 1, M1 is selected from at least one of the following: Zr, Y, K, Sr, and Ba. M2 is selected from at least one of the following: boron (B), Ba, cerium (Ce), chromium (Cr), magnesium (Mg), vanadium (V), titanium (Ti), iron (Fe), zinc (Zn), silicon (Si), niobium (Nb), gallium (Ga), tin (Sn), molybdenum (Mo), tungsten (W), and phosphorus (P). A is selected from at least one of the following: fluorine (F), chlorine (Cl), bromine (Br), iodine (I), and sulfur (S), and 1.0 ≤ x ≤ 1.3, 0.6 ≤ a < 1, 0.0 <b≤0.4,0.0<c≤0.4,0.0<d≤0.01,0.0<e≤0.005,0.0≤f≤0.2,a+b+c+d+e+f=1,0≤y≤0.2。

[0049] 'a' represents the atomic fraction of nickel in the lithium complex transition metal oxide, where 'a' can be greater than 0.6, 0.8, or 0.85, or less than 0.95, 0.98, or 1.0.

[0050] b represents the atomic fraction of cobalt in the lithium complex transition metal oxide, where b can be greater than 0.0 or 0.01, or less than 0.15, 0.2 or 0.4.

[0051] c represents the atomic fraction of manganese in the lithium complex transition metal oxide, where c can be 0.0, 0.01 or more, 0.15, 0.2 or less than 0.4.

[0052] d represents the atomic fraction of aluminum in the lithium complex transition metal oxide, where d can be greater than 0.0, 0.002, or 0.003, or less than 0.006, 0.008, or 0.01.

[0053] e represents the atomic fraction of element M1 in the lithium complex transition metal oxide, where e can be greater than 0.0, 0.0001, 0.0002, or 0.0006, or less than 0.002, 0.003, or 0.005.

[0054] f represents the atomic fraction of element M2 in the lithium complex transition metal oxide, where f can be greater than 0.0, 0.05, 0.1 or less than 0.2.

[0055] According to the present invention, the positive electrode active material may further include a cobalt (Co) coating formed on a lithium composite transition metal oxide in single-particle form. The coating may further include Al, Zr, or a combination thereof. When the positive electrode active material also includes a coating, the amount of residual lithium byproducts can be reduced, structural stability can be improved to enhance battery life and resistance performance, and gas generation can also be reduced. In this case, the coating may be in the form of a thin film and may be formed entirely or partially on the lithium composite transition metal oxide.

[0056] Based on the total molar number of metals other than lithium contained in the lithium complex transition metal oxide, the Co content in the coating can be from 0.5 mol% to 3 mol%. In this case, residual lithium byproducts can be further reduced, and lifetime and resistivity performance can be further improved.

[0057] Based on the total weight of the lithium complex transition metal oxide, the Al content present in the coating can range from 300 ppm to 10,000 ppm. In this case, the lifetime and resistivity can be further improved due to the further enhancement of structural stability.

[0058] Methods for preparing positive electrode active materials This invention provides a method for preparing the above-mentioned positive electrode active material. Specifically, the positive electrode active material according to this invention is prepared by the following method for preparing positive electrode active materials.

[0059] The method for preparing the positive electrode active material according to the present invention includes the following steps: (A) A mixture is prepared by mixing a positive electrode active material precursor containing Ni, Co and Mn, an aluminum-containing raw material, an M1-containing raw material and a first lithium-containing raw material; (B) A one-time sintered product is prepared by sintering the mixture once at a temperature of 800°C to 950°C; and (C) A secondary sintered product is prepared by mixing a second lithium-containing raw material with a primary sintered product and then performing a secondary sintering at a temperature of 680°C to 850°C.

[0060] In this case, M1 is at least one selected from Zr, Y, K, Sr and Ba, and the amount of raw material containing M1 is between 100 ppm and 5,000 ppm based on the total weight of the positive electrode active material precursor.

[0061] The inventors discovered that by adding lithium separately in steps (A) and (C), performing sintering in two stages, and adding a predetermined amount or more of M1 as a dopant before the first sintering, a single-particle lithium transition metal oxide is generated. Furthermore, due to the small particle deformation of the positive electrode active material, the particle size distribution does not change much even after rolling, thus completing the present invention.

[0062] The cathode active material precursor containing Ni, Co and Mn can have a composition represented by the following chemical formula 2 or chemical formula 3.

[0063] [Chemical Formula 2] Ni a' Co b' Mn c' M2 d' (OH)2 [Chemical Formula 3] Ni a' Co b' Mn c' M2 d' O·OH In chemical formulas 2 and 3, M2 is selected from at least one of B, Ba, Ce, Cr, Mg, V, Ti, Fe, Zn, Si, Nb, Ga, Sn, Mo, W, and P, and 0.6≤a'<1, 0.0 <b'≤0.4,0.0<c'≤0.4,0.0≤d'≤0.2。

[0064] The aluminum-containing raw material can 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, and more specifically Al(OH)3. Based on the total weight of the cathode active material precursor, the amount of aluminum-containing raw material added can be from 500 ppm to 3,000 ppm. Specifically, based on the total weight of the cathode active material precursor, the amount of aluminum-containing raw material can be 500 ppm, 600 ppm, 700 ppm, 800 ppm, 900 ppm, 1,000 ppm, 1,100 ppm, 1,200 ppm, 1,300 ppm, 1,400 ppm or more, 2,800 ppm, 2,900 ppm, and less than 3,000 ppm. In this case, because the internal crystal structure of the cathode active material is stabilized, there is an advantage of better battery life performance.

[0065] The raw material containing M1 can be a hydroxide, oxide, chloride, nitrogen oxide, sulfur oxide or sulfide containing M1, but is not limited to these.

[0066] When M1 is Y, the yttrium (Y)-containing raw material can 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, and more specifically Y2O3. Based on the total weight of the cathode active material precursor, the amount of yttrium-containing raw material added can be from 100 ppm to 2,000 ppm. Specifically, based on the total weight of the cathode active material precursor, the amount of yttrium-containing raw material can be 100 ppm, 200 ppm, 300 ppm, 400 ppm, 500 ppm, 600 ppm, 700 ppm, 800 ppm, 900 ppm, or more than 1,000 ppm but less than 2,000 ppm. In this case, because the grain size contained in a single particle is large, the capacity and lifespan performance of the battery can be further improved.

[0067] Furthermore, when M1 is Zr, the zirconium-containing raw material can 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 zirconium-containing raw material added can be from 500 ppm to 5,000 ppm based on the total weight of the cathode active material precursor. Specifically, based on the total weight of the cathode active material precursor, the amount of zirconium-containing raw material can be 500 ppm, 1,000 ppm, 1,500 ppm or more, 3,000 ppm, 3,500 ppm, 4,000 ppm, 4,500 ppm, and less than 5,000 ppm. In this case, because Zr is stably doped in the lithium layer, thereby further improving the structural stability during lithium insertion and extraction, there is also the advantage of further improved particle strength.

[0068] If the mixture is sintered in one step at a temperature between 800℃ and 950℃, a single-particle sintered product is prepared simultaneously with the primary particle agglomeration of the cathode active material precursor. Specifically, the primary sintering temperature can be above 800℃, 810℃, 820℃, 830℃, 840℃, or 850℃, or below 900℃, 910℃, 920℃, 930℃, 940℃, or 950℃. When the primary sintering temperature is within the above range, a structurally stable single-particle sintered product is prepared simultaneously with the primary particle agglomeration of the cathode active material precursor. However, when the primary sintering temperature is below 800℃, insufficient primary particle agglomeration occurs; and when the primary sintering temperature is above 950℃, the prepared sintered product exhibits unstable structure and low crystallinity.

[0069] To prevent lithium transition metal oxides from degenerating into rock salt structures, a single sintering process can be carried out in an oxygen atmosphere.

[0070] In terms of agglomerating primary particles and improving the crystallinity of primary sintering products, primary sintering can be carried out for 3 to 12 hours, specifically 3 hours, 4 hours, 5 hours, more than 6 hours, 9 hours, 10 hours, 11 hours or less than 12 hours.

[0071] If the primary sintering product is sintered a second time at a temperature between 680°C and 850°C, a secondary sintering product is prepared simultaneously with lithium intercalation into the primary sintering product. In this case, the secondary sintering product is a single-particle lithium composite transition metal oxide. The specific secondary sintering temperature can be 680°C, 700°C, 720°C, 740°C, 760°C, 780°C, above 800°C, 840°C, or below 850°C. When the secondary sintering temperature is within the above range, the advantage is that while lithium intercalates into the rock salt structure that can be formed on the surface of the primary sintering product due to the high temperature during primary sintering, the layered structure is restored, and lithium byproducts are reduced. When the secondary sintering temperature is below 680°C, there is a problem of low lithium intercalation rate due to the low temperature; when the secondary sintering temperature is above 850°C, there is a problem of the surface of the primary sintering product degenerating into a rock salt structure due to the high temperature, and lithium byproducts remaining.

[0072] Secondary sintering can be carried out in an oxygen atmosphere to prevent lithium transition metal oxides from degenerating into rock salt structures.

[0073] In terms of improving the crystallinity of the internal crystal structure of the positive electrode active material, the secondary sintering can be carried out for 3 to 12 hours, specifically 3 hours, 4 hours, 5 hours, 6 hours, more than 9 hours, 9 hours, 10 hours, 11 hours or less than 12 hours.

[0074] The method for preparing the positive electrode active material according to the present invention may further include a step (B') of grinding the sintered product once before step (C). In order to prevent an increase in initial resistance, step (B') may grind the sintered product once, such that the average particle size (D) is reduced. 50 The range is from 3.50 μm to 6.00 μm.

[0075] The method for preparing the positive electrode active material according to the present invention may further include a step (C') of grinding the secondary sintered product. Also in order to prevent an increase in initial resistance, step (C') may grind the secondary sintered product to reduce the average particle size (D). 50 The range is from 3.50 μm to 6.00 μm.

[0076] The grinding in steps (B') and (C') can be performed using a pin mill, an air classifier (ACM), or a jet mill. For a pin mill, grinding can be performed at 18,000 rpm; for an ACM, using equipment from Hosokawa Micron Corporation, classification can be performed at 6,000 rpm and main grinding at 12,000 rpm; and for a 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. Under these conditions, a particle size (D) with the desired average particle size can be easily obtained. 50 ) positive electrode active material.

[0077] The positive electrode active material according to the present invention is prepared by a two-part process of adding lithium-containing raw materials. That is, the lithium-containing raw materials can be added separately before the first sintering and before the second sintering. In this case, the advantage is that lithium is embedded into the rock salt structure that can be formed on the surface, which is beneficial to the restoration of the layered structure. When the lithium-containing raw materials are added all at once before the first sintering, there is a problem of reduced electrochemical performance due to the increase of lithium by-products, and if the lithium-containing raw materials are not added in the second sintering, there is a problem of high temperature and long time required due to slow reaction rate.

[0078] When adding lithium-containing raw materials in two parts, in step (A), the first lithium-containing raw material can be mixed such 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 1:0.98, 1:0.99, 1:1.00, 1:1.01, 1:1.02 or more, 1:1.04 or less, or 1:1.05. In step (C), the second lithium-containing raw material can be mixed such that the ratio (M:Li) of the total number of moles of transition metals (M) contained in the positive electrode active material precursor in step (A) to the number of moles of lithium (Li) contained in the second lithium-containing raw material is 1:0.01 or more, 1:0.05, 1:0.06, 1:0.07, 1:0.08, 1:0.09 or less, or 1:1.10 or less.

[0079] The method for preparing the positive electrode active material according to the present invention may further include a step (D) of mixing the secondary sintering product and the cobalt-containing coating material and performing heat treatment. In this case, a Co-containing coating is formed on the secondary sintering product (lithium composite transition metal oxide in single-particle form).

[0080] According to the present invention, when the secondary sintering 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.

[0081] According to the present invention, the cobalt-containing coating material can be mixed in an amount such that the ratio (B / A) of the molar number of cobalt contained in the cobalt-containing coating material to the total molar number of metals other than lithium contained in the secondary sintering product (excluding lithium) is in the range of 0.01 to 0.03. In this case, there is an advantage that lithium byproducts can be controlled in the positive electrode active material preparation process, excluding the washing step.

[0082] The cobalt-containing coating material can be at least one selected from Co(OH)2, Co3O4, CoO, (CH3CO2)2Co, CoCl2 and CoSO4·xH2O, specifically Co(OH)2.

[0083] According to the present invention, the aluminum-containing coating material can be mixed in an amount of 0.03 to 0.10 parts by weight based on 100 parts by weight of the secondary sintering product. In this case, by ensuring structural stability, lifespan, electrical resistance, and gas generation can be improved.

[0084] The aluminum-containing coating material can be at least one selected from Al(OH)3, Al2(SO4)3·xH2O, Al2O3, Al(NO3)3·9H2O, AlCl3 and C2H5O4Al, specifically Al(OH)3.

[0085] Zirconium-containing coating materials can be selected from Zr(OH)4, ZrO2, Zr(NO3)4, ZrCl4, ZrS2, Zr(SO4)2 and C8H. 12 At least one of O8Zr.

[0086] According to the present invention, heat treatment can be carried out in an oxygen atmosphere to prevent lithium transition metal oxides from degrading to a rock salt structure.

[0087] According to the present invention, in order to form a coating of appropriate thickness, heat treatment can be performed as follows: after heat treatment at a temperature of 600°C, 610°C, 620°C, 630°C, 640°C, 650°C to 720°C, 740°C, 760°C, 780°C or below 800°C, the temperature is lowered to approximately 450°C to 550°C, and then heat treatment is performed at a temperature of 450°C, 460°C, 470°C, 480°C to 520°C, 530°C, 540°C or below 550°C. That is, in a sintering curve, after heat treatment at 600°C to 800°C, heat treatment can be performed at 450°C to 550°C.

[0088] According to the present invention, the heat treatment can be performed for 1 hour, 2 hours, 3 hours or more, 8 hours, 9 hours or less than 10 hours to improve the crystallinity of the coated part.

[0089] positive electrode The present invention provides a positive electrode comprising the positive electrode active material.

[0090] 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 aforementioned positive electrode active material.

[0091] The positive electrode current collector can contain a highly conductive metal, and there are no particular limitations, as long as it is non-reactive within the battery's voltage range and the positive electrode active material layer can easily adhere to it. Examples of materials that can be used as the positive electrode current collector include: stainless steel, aluminum, nickel, titanium, sintered carbon; or aluminum or stainless steel with a surface treatment of carbon, nickel, titanium, silver, etc. Furthermore, the positive electrode current collector can typically have a thickness from 3 μm to 500 μm, and fine irregularities can 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 can be used in various shapes such as films, sheets, foils, meshes, porous bodies, foams, nonwoven fabrics, etc.

[0092] If desired, in addition to the positive electrode active material, the positive electrode active material layer may optionally contain conductive materials and binders. In this case, based on the total weight of the positive electrode active material layer, the content of the positive electrode active material can be from 80% to 99% by weight, more specifically from 85% to 98.5% by weight, and excellent capacity performance can be obtained within this range.

[0093] Conductive materials are used to provide conductivity to the electrodes. Any conductive material can be used without particular limitation, as long as it has suitable electronic conductivity and will not cause adverse chemical changes in the battery. Specific examples of conductive materials include: graphite such as natural or artificial graphite; carbonaceous materials such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal cracking black, and carbon fibers; powders or fibers 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 or a mixture of two or more thereof can be used. Based on the total weight of the positive electrode active material layer, the content of the conductive material can be from 0.1% by weight to 15% by weight.

[0094] The adhesive improves the adhesion between the positive electrode active material particles and the adhesion between the positive electrode active material and the current collector. Specific examples of adhesives include: polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, polymethyl methacrylate, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene propylene diene monomer (EPDM), sulfonated EPDM, styrene-butadiene rubber (SBR), fluororubber, polyacrylic acid and polymers whose hydrogen is replaced by lithium (Li), sodium (Na), or calcium (Ca), or various copolymers thereof, and any one or a mixture of two or more thereof may be used. Based on the total weight of the positive electrode active material layer, the adhesive content can range from 0.1% by weight to 15% by weight.

[0095] In addition to using the aforementioned positive electrode active materials, positive electrodes can be prepared according to typical methods for preparing positive electrodes. Specifically, a positive electrode active material layer forming composition, prepared by dissolving or dispersing the positive electrode active material along with optional binders and conductive materials in a solvent, is coated onto a positive electrode current collector. The positive electrode can then be prepared by drying and calendering the coated positive electrode current collector, or by casting the positive electrode active material layer forming composition onto a separate carrier and then stacking the film layer separated from the carrier onto the positive electrode current collector.

[0096] The solvent can be any solvent commonly used in the art and can include: dimethyl sulfoxide (DMSO), isopropanol, N-methylpyrrolidone (NMP), dimethylformamide (DMF), acetone, or water, and any one of them or a mixture of two or more thereof can be used. If the solvent can dissolve or disperse the positive electrode active material, conductive material, binder, and dispersant, and can produce a viscosity that provides excellent thickness uniformity during subsequent coating for preparing the positive electrode, then the amount of solvent used can be sufficient.

[0097] Lithium secondary batteries This invention provides a lithium secondary battery, the lithium secondary battery comprising: positive electrode; negative electrode; A diaphragm positioned between the positive and negative electrodes; and Electrolytes.

[0098] The lithium secondary battery may also optionally include: a battery container housing an electrode assembly containing a positive electrode, a negative electrode, and a separator, and a sealing member for sealing the battery container.

[0099] The negative electrode may include a negative electrode current collector and a layer of negative electrode active material disposed on the negative electrode current collector.

[0100] There are no particular restrictions on the negative electrode current collector, as long as it has high conductivity and will not cause adverse chemical changes in the battery. Materials used include, for example, copper, stainless steel, aluminum, nickel, titanium, sintered carbon; copper or stainless steel surface-treated with one of carbon, nickel, titanium, or silver; and aluminum-cadmium alloys. Furthermore, the negative electrode current collector can typically have a thickness from 3 μm to 500 μm, and similar to the positive electrode current collector, fine irregularities can be formed on its surface to improve the adhesion of the negative electrode active material. For example, the negative electrode current collector can be used in various shapes such as films, sheets, foils, meshes, porous bodies, foams, and nonwoven fabrics.

[0101] In addition to the negative electrode active material, the negative electrode active material layer may optionally include a binder and a conductive material.

[0102] Compounds capable of reversibly inserting and de-intercalating lithium can be used as anode active materials. Specific examples of anode active materials include: 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; and (semi-)metal oxides that can be doped and de-doped with lithium, such as SiO2. β(0<β<2), SnO2, vanadium oxide, and lithium vanadium oxide; or composite materials containing (semi-)metallic materials and carbonaceous materials such as Si-C composites or Sn-C composites, and any one of them or a mixture of two or more thereof can be used. Furthermore, lithium metal films can be used as the negative electrode active material. In addition, both low-crystallinity carbon and high-crystallinity carbon can be used as carbon materials. Typical examples of low-crystallinity carbon can be soft carbon and hard carbon, and typical examples of high-crystallinity carbon can be irregular, planar, sheet-like, spherical, or fibrous natural or artificial graphite, condensed graphite, pyrolytic carbon, mesophase pitch-based carbon fibers, mesophase carbon microspheres, mesophase pitch, and high-temperature sintered carbon such as coke derived from petroleum or coal tar pitch. Based on the total weight of the negative electrode active material layer, the content of the negative electrode active material can be from 80% to 99% by weight.

[0103] The binder in the negative electrode active material layer is a component that facilitates the bonding between the conductive material, the active material, and the current collector. It is typically added in amounts ranging from 0.1% to 10% by weight, based on the total weight of the negative electrode active material layer. Examples of binders include: polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene propylene diene monomer (EPDM), sulfonated EPDM, styrene-butadiene rubber, nitrile rubber, fluororubber, and various copolymers thereof.

[0104] The conductive material in the negative electrode active material layer is a component used to further improve the conductivity of the negative electrode active material. Based on the total weight of the negative electrode active material layer, the conductive material can be added in an amount of 10% by weight or less, preferably 5% by weight or less. There are no particular limitations on the conductive material, as long as it is conductive and will not cause adverse chemical changes in the battery. For example, conductive materials such as: graphite (e.g., natural or artificial graphite); carbon black (e.g., acetylene black, Ketjen black, channel black, furnace black, lamp black, and thermally cracked black); conductive fibers (e.g., carbon fiber or metal fiber); fluorocarbons; metal powders (e.g., aluminum and nickel powder); conductive whiskers (e.g., zinc oxide whiskers and potassium titanate whiskers); conductive metal oxides (e.g., titanium oxide); or polyphenylene derivatives.

[0105] The negative electrode can be prepared by coating a negative electrode active material layer forming composition, which is prepared by dissolving or dispersing optional binder and conductive material and negative electrode active material in a solvent, onto a negative electrode current collector and drying the coated negative electrode current collector, or by casting the negative electrode active material layer forming composition onto a separate carrier and then stacking the film layer separated from the carrier onto the negative electrode current collector.

[0106] The separator separates the negative and positive electrodes and provides a path for lithium ions to move. Any separator can be used without particular limitation, as long as it is commonly used in lithium secondary batteries. In particular, separators with high electrolyte retention capacity and low resistance to electrolyte ion transfer can be used. Specifically, porous polymer membranes can be used, such as porous polymer membranes prepared from polyolefin polymers like ethylene homopolymers, propylene homopolymers, ethylene / butene copolymers, ethylene / hexene copolymers, and ethylene / methacrylate copolymers; or membranes having two or more layers. Furthermore, typical porous nonwoven fabrics can be used, such as nonwoven fabrics formed from high-melting-point glass fibers or polyethylene terephthalate fibers. Additionally, separators coated with ceramic components or polymer materials can be used to ensure heat resistance or mechanical strength, and separators with single-layer or multi-layer structures can optionally be used.

[0107] The electrolyte may include organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel polymer electrolytes, solid inorganic electrolytes, or molten inorganic electrolytes that can be used to prepare lithium secondary batteries, but the present invention is not limited thereto. As a specific example, the electrolyte may contain an organic solvent and a lithium salt.

[0108] Any organic solvent can be used without particular limitation, as long as it serves as a medium through which ions participating in the battery electrochemical reaction 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; nitriles such as R-CN (where R is a linear, branched, or cyclic C2-C20 hydrocarbon group and may contain double bonds, aromatic rings, or ether bonds); amides such as dimethylformamide; dioxolane such as 1,3-dioxolane; or sulfolane. Among these solvents, carbonate solvents are preferred, and more preferably are mixtures of cyclic carbonates (e.g., ethylene carbonate or propylene carbonate) with high ionic conductivity and high dielectric constant that can improve the charge / discharge performance of the battery and low viscosity linear carbonate compounds (e.g., ethyl methyl carbonate, dimethyl carbonate or diethyl carbonate).

[0109] Lithium salts can be used without particular restrictions, as long as they are compounds 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: F - Cl - ,Br - I- NO3 - N(CN)2 - BF4 - CF3CF2SO3 - (CF3SO2)2N - (FSO2)2N - CF3CF2(CF3)2CO - (CF3SO2)2CH - (SF5)3C - (CF3SO2)3C - CF3(CF2)7SO3 - CF3CO2 - CH3CO2 - SCN - and (CF3CF2SO2)2N - 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 concentrations ranging from 0.1 M to 2.0 M. If the concentration of the lithium salt is included within the above range, excellent electrolyte performance can be obtained because the electrolyte can have suitable conductivity and viscosity, and lithium ions can move efficiently.

[0110] To improve battery life, suppress capacity reduction, and enhance discharge capacity, the electrolyte may contain at least one additive in addition to the electrolyte components mentioned above. Examples of additives include alkylene carbonate halides such as difluoroethylene carbonate, pyridine, triethyl phosphite, triethanolamine, cyclic ethers, ethylenediamine, (condensed) glycol dimethyl ethers, hexamethylphosphoric triamine, nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted alkylene ketones, N,N-substituted imidazolidinyl ethers, ethylene glycol dialkyl ethers, ammonium salts, pyrrole, 2-methoxyethanol, or aluminum trichloride. In this case, the additive content can range from 0.1% to 5% by weight, based on the total weight of the electrolyte.

[0111] Because lithium secondary batteries containing the positive electrode active material according to the invention have excellent performance, they are suitable for: portable devices such as mobile phones, laptops and digital cameras; and electric vehicles such as hybrid electric vehicles (HEVs) and electric vehicles (EVs).

[0112] There are no particular limitations on the shape of the lithium secondary battery of the present invention, but cylindrical, prismatic, bag-shaped or coin-shaped batteries made from cans can be used.

[0113] The lithium secondary battery according to the present invention can be used not only as a battery cell for use as a power source for small devices, but also as a unit battery in medium and large battery modules containing multiple battery cells.

[0114] Therefore, a battery module containing a lithium secondary battery as a unit cell and a battery pack containing the battery module are provided.

[0115] Battery modules or battery packs can be used as a power source for at least one medium to large-sized device, including: power tools; electric vehicles, including electric vehicles (EVs), hybrid electric vehicles, and plug-in hybrid electric vehicles (PHEVs); or energy storage systems.

[0116] In the following description, examples of the invention will be presented in a manner readily practiced by those skilled in the art. However, the invention may be embodied in many different forms and should not be construed as limited to the examples set forth herein.

[0117] Preferred Implementation Examples and Comparative Examples Example 1 To achieve a ratio of 1:1.03 (Ni+Co+Mn): a composite transition metal hydroxide in the form of secondary particles formed by the aggregation of tens to hundreds of primary particles, the composite transition metal hydroxide is constructed with the following composition: Ni... 0.885 Co 0.035 Mn 0.08 (OH)2, average particle size (D) 50 (4.20 μm) and LiOH were mixed, and Al(OH)3 (KC DAEJOO), Y2O3 (Neo Performance Materials) and ZrO2 (R&F) were added to it in amounts of 1,400 ppm, 1,000 ppm and 1,500 ppm based on the total weight of the complex transition metal hydroxide, respectively, and mixed to prepare a mixture.

[0118] The mixture was sintered at 890°C for 6 hours to obtain a first-sintered product, and then ground at room temperature to achieve an average particle size (D). 50 The thickness is 3.80 μm.

[0119] To achieve a ratio of (Ni+Co+Mn):Li of 1:1 between the total molar number of transition metals (Ni+Co+Mn) in the composite transition metal hydroxide and the molar number of lithiums (Li) in LiOH, the ground primary sintered product was mixed with LiOH and subjected to a secondary sintering at 820°C for 9 hours to obtain a secondary sintered product. The secondary sintered product was then ground at room temperature to obtain an average particle size (D). 50 The lithium composite transition metal oxide (LiNi) is a single-particle form with a particle size of 3.80 μm. 0.87836 Co 0.03493 Mn 0.07985 Al 0.00499 Y 0.00027 Zr 0.0016 O2).

[0120] After uniformly mixing single-particle lithium composite transition metal oxide with Co(OH)₂ (Huayou Cobalt) and Al(OH)₃ (KC DAEJOO), the mixture was heat-treated at 700°C for 5 hours and then at 500°C for 3 hours in an oxygen atmosphere to prepare a positive electrode active material in which a coating containing Co and Al is formed on the single-particle lithium composite transition metal oxide. In this case, Co(OH)₂ was 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 single-particle lithium composite transition metal oxide was 0.02, and Al(OH)₃ was mixed in an amount of 0.05 parts by weight based on 100 parts by weight of the single-particle lithium composite transition metal oxide.

[0121] Example 2 To achieve a ratio of 1:1.03 (Ni+Co+Mn): a composite transition metal hydroxide in the form of secondary particles formed by the aggregation of tens to hundreds of primary particles, the composite transition metal hydroxide is constructed with the following composition: Ni... 0.885 Co 0.035 Mn 0.08 (OH)2, average particle size (D) 50 (4.20 μm) and LiOH were mixed, and Al(OH)3 (KC DAEJOO), Y2O3 (Neo Performance Materials) and ZrO2 (R&F) were added to it in amounts of 1,400 ppm, 2,000 ppm and 1,500 ppm based on the total weight of the complex transition metal hydroxide, respectively, and mixed to prepare a mixture.

[0122] The mixture was sintered at 890°C for 6 hours to obtain a first-sintered product, and then ground at room temperature to achieve an average particle size (D). 50 The thickness is 3.80 μm.

[0123] To achieve a ratio of (Ni+Co+Mn):Li of 1:1 between the total molar number of transition metals (Ni+Co+Mn) in the composite transition metal hydroxide and the molar number of lithiums (Li) in LiOH, the ground primary sintered product was mixed with LiOH and subjected to a secondary sintering at 820°C for 9 hours to obtain a secondary sintered product. The secondary sintered product was then ground at room temperature to obtain an average particle size (D). 50 The lithium composite transition metal oxide (LiNi) is a single-particle form with a particle size of 3.80 μm. 0.87813 Co 0.03492 Mn 0.07983 Al 0.00499 Y 0.00054 Zr 0.00159 O2).

[0124] After uniformly mixing single-particle lithium composite transition metal oxide with Co(OH)₂ (Huayou Cobalt) and Al(OH)₃ (KC DAEJOO), the mixture was heat-treated at 700°C for 5 hours and then at 500°C for 3 hours in an oxygen atmosphere to prepare a positive electrode active material in which a coating containing Co and Al is formed on the single-particle lithium composite transition metal oxide. In this case, Co(OH)₂ was 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 single-particle lithium composite transition metal oxide was 0.02, and Al(OH)₃ was mixed in an amount of 0.05 parts by weight based on 100 parts by weight of the single-particle lithium composite transition metal oxide.

[0125] Example 3 To achieve a ratio of 1:1.03 (Ni+Co+Mn): a composite transition metal hydroxide in the form of secondary particles formed by the aggregation of tens to hundreds of primary particles, the composite transition metal hydroxide is constructed with the following composition: Ni... 0.885 Co 0.035 Mn 0.08 (OH)2, average particle size (D) 50The mixture was prepared by mixing Al(OH)3 (KC DAEJOO), Y2O3 (Neo Performance Materials) and ZrO2 (R&F) in amounts of 2,800 ppm, 1,000 ppm and 1,500 ppm based on the total weight of the complex transition metal hydroxides.

[0126] The mixture was sintered at 890°C for 6 hours to obtain a first-sintered product, and then ground at room temperature to achieve an average particle size (D). 50 The thickness is 3.80 μm.

[0127] To achieve a ratio of (Ni+Co+Mn):Li of 1:1 between the total molar number of transition metals (Ni+Co+Mn) in the composite transition metal hydroxide and the molar number of lithiums (Li) in LiOH, the ground primary sintered product was mixed with LiOH and subjected to a secondary sintering at 820°C for 9 hours to obtain a secondary sintered product. The secondary sintered product was then ground at room temperature to obtain an average particle size (D). 50 The lithium composite transition metal oxide (LiNi) is a single-particle form with a particle size of 3.80 μm. 0.87338 Co 0.03493 Mn 0.07985 Al 0.00998 Y 0.00027 Zr 0.00159 O2).

[0128] After uniformly mixing single-particle lithium composite transition metal oxide with Co(OH)₂ (Huayou Cobalt) and Al(OH)₃ (KC DAEJOO), the mixture was heat-treated at 700°C for 5 hours and then at 500°C for 3 hours in an oxygen atmosphere to prepare a positive electrode active material in which a coating containing Co and Al is formed on the single-particle lithium composite transition metal oxide. In this case, Co(OH)₂ was 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 single-particle lithium composite transition metal oxide was 0.02, and Al(OH)₃ was mixed in an amount of 0.05 parts by weight based on 100 parts by weight of the single-particle lithium composite transition metal oxide.

[0129] Example 4 To achieve a ratio of 1:1.03 (Ni+Co+Mn): a composite transition metal hydroxide in the form of secondary particles formed by the aggregation of tens to hundreds of primary particles, the composite transition metal hydroxide is constructed with the following composition: Ni... 0.885 Co 0.035 Mn 0.08 (OH)2, average particle size (D) 50 (4.20 μm) and LiOH were mixed, and Al(OH)3 (KC DAEJOO), Y2O3 (Neo Performance Materials) and ZrO2 (R&F) were added to it in amounts of 1,400 ppm, 1,000 ppm and 3,000 ppm based on the total weight of the complex transition metal hydroxide, respectively, and mixed to prepare a mixture.

[0130] The mixture was sintered at 890°C for 6 hours to obtain a first-sintered product, and then ground at room temperature to achieve an average particle size (D). 50 The thickness is 3.80 μm.

[0131] To achieve a ratio of (Ni+Co+Mn):Li of 1:1 between the total molar number of transition metals (Ni+Co+Mn) in the composite transition metal hydroxide and the molar number of lithiums (Li) in LiOH, the ground primary sintered product was mixed with LiOH and subjected to a secondary sintering at 820°C for 9 hours to obtain a secondary sintered product. The secondary sintered product was then ground at room temperature to obtain an average particle size (D). 50 The lithium composite transition metal oxide (LiNi) is a single-particle form with a particle size of 3.80 μm. 0.87651 Co 0.03486 Mn 0.07968 Al 0.00498 Y 0.00027 Zr 0.0037 O2).

[0132] After uniformly mixing single-particle lithium composite transition metal oxide with Co(OH)₂ (Huayou Cobalt) and Al(OH)₃ (KC DAEJOO), the mixture was heat-treated at 700°C for 5 hours and then at 500°C for 3 hours in an oxygen atmosphere to prepare a positive electrode active material in which a coating containing Co and Al is formed on the single-particle lithium composite transition metal oxide. In this case, Co(OH)₂ was 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 single-particle lithium composite transition metal oxide was 0.02, and Al(OH)₃ was mixed in an amount of 0.05 parts by weight based on 100 parts by weight of the single-particle lithium composite transition metal oxide.

[0133] Comparative Example 1 Except that Y2O3 was not added during the preparation of the mixture, the lithium composite transition metal oxide (composition: LiNi) in single-particle form was prepared in the same manner as in Example 1. 0.8786 Co 0.03494 Mn 0.07987 Al 0.00499 Zr 0.0016 A positive electrode active material containing Co and Al is formed on O2.

[0134] Comparative Example 2 Except that Al(OH)3 was not added during the preparation of the mixture, the lithium composite transition metal oxide (composition: LiNi) in single-particle form was prepared in the same manner as in Example 1. 0.88336 Co 0.03493 Mn 0.07985 Y 0.00027 Zr 0.0015 A positive electrode active material containing Co and Al is formed on 9O2).

[0135] Comparative Example 3 Except that no ZrO2 was added during the preparation of the mixture, the lithium composite transition metal oxide (composition: LiNi) in single-particle form was prepared in the same manner as in Example 1. 0.87976 Co 0.03499 Mn 0.07998 Al 0.005 Y 0.00027 A positive electrode active material containing Co and Al is formed on O2.

[0136] Experimental Example Experimental Example 1: Particle Size Analysis of Positive Electrode Active Materials 0.01 g of each of the positive electrode active material (powder) prepared in Examples 1 to 4 and Comparative Examples 1 to 3 was placed in a vial containing 30 ml of ultrapure water and 500 μl of dispersant. After dispersing the positive electrode active material with an ultrasonic generator for 1 minute, the dispersion was placed in a particle size analyzer (PSA) (Microtrac MRB, S3500) to obtain the D of each positive electrode active material. 10 D 50 and D 90 Value, and calculate α=(D) 90 -D 10 ) / D 50 The value of D. In this case, D 10 D 50 and D 90 These refer to the particle size at 10%, 50%, and 90% of the volumetric cumulative distribution based on particle size, respectively.

[0137] In addition, 3 g of each of the positive electrode active material (powder) prepared in Examples 1 to 4 and Comparative Examples 1 to 3 were then granulated using an automatic pelletizer (Carver Inc., 3887.4) at a pressure of 6,780.6 kgf / cm³. 2 Pellets were prepared by pressing under pressure (by placing 3 g of positive electrode active material (powder) into a circular particle holder with a diameter of 13 mm and applying force up to 9,000 kgf). To re-powder the particles, they were crushed in a mortar for 1 minute. 0.01 g of the crushed positive electrode active material was placed in a vial containing 30 ml of ultrapure water and 500 μl of dispersant. After dispersing the positive electrode active material using an ultrasonic generator for 1 minute, the dispersion was placed in a particle size analyzer (PSA) (Microtrac MRB, S3500) to obtain the D of each positive electrode active material. 10 D 50 and D 90 The value of , and calculate β=(D 90 -D 10 ) / D 50 The value of .

[0138] For reference, crushing with a mortar and pestle does not affect the average particle size of the positive electrode active material.

[0139] The values ​​of α and β are calculated by substituting them into mathematical formula 1, and are shown in Table 1 below.

[0140] [Table 1]

[0141] Experiment Example 2: Evaluation of Battery Performance The positive electrode active materials, carbon black conductive materials, and polyvinylidene fluoride (PVDF) binder prepared in Examples 1 to 4 and Comparative Examples 1 to 3 were mixed in an N-methylpyrrolidone (NMP) solvent at a ratio of 96:2:2 to prepare a positive electrode slurry. The positive electrode slurry was coated on one surface of an aluminum current collector, dried at 150°C, and then calendered to prepare the positive electrode. Using a lithium metal electrode as the negative electrode, an electrode assembly is prepared by placing a porous polyethylene membrane between the positive and negative electrodes. The electrode assembly is then placed in a battery case, and an electrolyte is injected into the case to prepare each half-cell. In this case, the electrolyte is 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.

[0143] Each half-cell thus prepared was charged to 4.3 V at 0.1 C in constant current-constant voltage (CC-CV) mode at 25 °C and discharged to 3.0 V at a constant current of 0.1 C. The initial charge capacity and initial discharge capacity were measured, and the initial efficiency and DC internal resistance (DCIR) were calculated. The results are shown in Table 2 below. For reference, the initial efficiency value is the percentage of the initial discharge capacity relative to the initial charge capacity, and the DCIR value is calculated by dividing the difference between the voltage of each half-cell after discharging at a constant current of 0.1 C for 60 seconds and the initial voltage by the applied current.

[0144] Furthermore, the capacity of the lithium secondary battery was measured by repeating 50 charge-discharge cycles at a constant current of 0.33 at 45°C within the range of 3.0 V to 4.25 V. The percentage of the discharge capacity of the 50th cycle relative to the discharge capacity of the 1st cycle was defined as the capacity retention rate, and the capacity retention rate is shown in Table 2 below. Additionally, the percentage of the DCIR obtained by dividing the voltage drop (ΔV) over 60 seconds in the 50th discharge cycle by the current, relative to the DCIR obtained by dividing the voltage drop (ΔV) over 60 seconds in the 1st discharge cycle by the current, was defined as the resistance increase rate, and the resistance increase rate is shown in Table 2 below.

[0145] [Table 2]

[0146] Referring to Tables 1 and 2, for batteries containing the positive electrode active materials of Examples 1 to 4 respectively, since the batteries contain Ni, Co, Mn, Al, Zr and Y and satisfy Mathematical Formula 1 as described in this specification, it can be confirmed that the battery capacity, initial efficiency, lifespan and resistivity are all excellent.

[0147] It can be confirmed that, compared with the battery containing the positive electrode active material of Example 1, the batteries containing the positive electrode active materials of Comparative Examples 1 to 3 respectively have lower initial discharge capacity, and their initial efficiency, lifetime, and resistance performance are all reduced. Because the positive electrode active material of Comparative Example 1 does not contain Y, its grain growth is problematic, and therefore it does not satisfy Mathematical Formula 1 as described in this specification, resulting in a decrease in the performance of the battery containing it. Furthermore, because the positive electrode active material of Comparative Example 2 does not contain Al, it exhibits a form with increased cation mixing due to numerous defects, resulting in a decrease in the performance of the battery containing it. Furthermore, because the positive electrode active material of Comparative Example 3 does not contain Zr, which can improve particle strength, it does not satisfy Mathematical Formula 1 as described in this specification, resulting in a decrease in the performance of the battery containing it.

Claims

1. A positive electrode active material, said positive electrode active material comprising lithium composite transition metal oxide in single-particle form, The lithium composite transition metal oxide comprises Ni, Co, Mn, Al, and M1. The M1 is selected from at least one of Zr, Y, K, Sr and Ba, and Satisfying mathematical formula 1: [Mathematical Expression 1] ｜1-α / β｜≤0.1 in, In mathematical formula 1, α is (D) 90 -D 10 ) / D 50 The value, and β represents the concentration of the positive electrode active material at 1,000 kgf / cm². 2 Up to 7,000 kgf / cm 2 (D) after rolling 90 -D 10 ) / D 50 The value of .

2. The positive electrode active material according to claim 1, wherein the lithium composite transition metal oxide has a layered structure.

3. The positive electrode active material according to claim 1, wherein the lithium composite transition metal oxide has an average particle size (D) of 3.00 μm to 8.00 μm. 50 ).

4. The positive electrode active material according to claim 1, wherein the lithium composite transition metal oxide is doped with Al and M1.

5. The positive electrode active material according to claim 1, wherein the Al content is from 500 ppm to 3,000 ppm based on the total weight of the lithium composite transition metal oxide.

6. The positive electrode active material according to claim 1, wherein the content of M1 is from 100 ppm to 5,000 ppm based on the total weight of the lithium composite transition metal oxide.

7. The positive electrode active material according to claim 1, wherein the lithium composite transition metal oxide contains more than 60 mol% nickel based on the total molar number of metals other than lithium.

8. 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 M1 e M2 f ]O 2-y A y In chemical formula 1, M1 is selected from at least one of Zr, Y, K, Sr and Ba. M2 is selected from at least one of B, Ba, Ce, Cr, Mg, V, Ti, Fe, Zn, Si, Nb, Ga, Sn, Mo, W, and P. A is selected from at least one of F, Cl, Br, I, and S, and 1.0 ≤ x ≤ 1.3, 0.6 ≤ a < 1, 0.0 <b≤0.4,0.0<c≤0.4,0.0<d≤0.01,0.0<e≤0.005,0.0≤f≤0.2,a+b+c+d+e+f=1,0≤y≤0.2。 9. A method for preparing a positive electrode active material, the method comprising the following steps: (A) A mixture is prepared by mixing a positive electrode active material precursor containing Ni, Co and Mn, an aluminum-containing raw material, an M1-containing raw material and a first lithium-containing raw material; (B) A one-time sintered product is prepared by sintering the mixture at a temperature of 800°C to 950°C; and (C) A secondary sintered product is prepared by mixing a second lithium-containing raw material with the primary sintered product and then performing a secondary sintering at a temperature of 680°C to 850°C. The M1 is selected from at least one of Zr, Y, K, Sr and Ba, and Based on the total weight of the positive electrode active material precursor, the mixing amount of the M1-containing raw material is from 100 ppm to 5,000 ppm.

10. The method according to claim 9, wherein the method further comprises a step (B') of grinding the primary sintering product prior to step (C).

11. The method according to claim 9, further comprising the step of grinding the secondary sintering product (C').

12. A positive electrode comprising the positive electrode active material according to any one of claims 1 to 8.

13. A lithium secondary battery, the lithium secondary battery comprising: The positive electrode as described in claim 12; negative electrode; A membrane disposed between the positive electrode and the negative electrode; and Electrolytes.

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