Positive electrode active material, its manufacturing method, and positive electrode and lithium secondary battery including the same

Abstract

The present invention relates to a positive electrode active material in a single particle form, the positive electrode active material including a lithium composite transition metal oxide in a single particle form, the lithium composite transition metal oxide including Al, Y, and Zr, a method for producing the positive electrode active material, and a positive electrode and a lithium secondary battery including the positive electrode active material.

Description

[Technical Field]

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2022-0080870, filed June 30, 2022, and all contents disclosed in the documents of this Korean patent application are incorporated herein by reference.

[0002] The present invention relates to a positive electrode active material containing a lithium composite transition metal oxide in the form of a single particle, a method for producing the same, and a positive electrode and a lithium secondary battery containing the same. [Background technology]

[0003] Recently, the development of single-particle cathode materials has been accelerating in order to solve the structural and thermal stability issues of secondary-particle cathode materials. Specifically, when secondary-particle cathode materials are applied to lithium secondary batteries, they generate a large amount of gas, causing the battery volume to expand. Furthermore, increasing the nickel content in the cathode material to achieve high capacity increases the risk of fire. Therefore, there is a growing need for the development of single-particle cathode materials. However, single-particle cathode materials have a problem of low specific surface area and poor resistance characteristics.

[0004] Therefore, there is a need to develop a single particle type cathode material that has excellent stability and can improve the initial efficiency and resistance characteristics of a battery when applied to the battery. Summary of the Invention [Problem to be solved by the invention]

[0005] The present invention is an invention for solving the above problems, and an object of the present invention is to provide a positive electrode active material including a lithium transition metal composite oxide in a single particle form, which has excellent structural stability and can improve the initial efficiency, resistance characteristics, etc. of a battery when applied to the battery.

[0006] Another object of the present invention is to provide a manufacturing method for manufacturing the positive electrode active material.

[0007] Another object of the present invention is to provide a lithium secondary battery containing the above positive electrode active material and having improved initial efficiency, resistance characteristics, and the like. [Means for solving the problem]

[0008] In order to solve the above problems, the present invention provides a positive electrode active material, a method for producing a positive electrode active material, a positive electrode, and a lithium secondary battery.

[0009] (1) The present invention provides a positive electrode active material comprising a lithium composite transition metal oxide in the form of a single particle, the lithium composite transition metal oxide comprising Al, Y, and Zr.

[0010] (2) In the present invention, in the above (1), the lithium transition metal composite oxide has an average particle size (D 50 ) is 2.5 μm to 5.5 μm.

[0011] (3) The present invention provides the positive electrode active material according to (1) or (2) above, wherein the Al content is 500 ppm to 3,000 ppm based on the total weight of the lithium composite transition metal oxide.

[0012] (4) The present invention provides the positive electrode active material according to any one of (1) to (3) above, wherein the Y is contained in an amount of 100 ppm to 2,000 ppm relative to the total weight of the lithium composite transition metal oxide.

[0013] (5) The present invention provides the positive electrode active material according to any one of (1) to (4) above, wherein the Zr content is 500 ppm to 5,000 ppm relative to the total weight of the lithium composite transition metal oxide.

[0014] (6) The present invention provides a positive electrode active material according to any one of the above (1) to (5), wherein the lithium transition metal composite oxide contains nickel in an amount of 60 mol % or more relative to the total number of moles of metals other than lithium.

[0015] (7) The present invention provides a positive electrode active material according to any one of the above (1) to (6), wherein the lithium composite transition metal oxide has a composition represented by the following chemical formula 1: [Chemical formula 1] Li x [Ni a Co b Mn c Al d Y e Zr f M1 g ]O 2-y A y In the above Chemical Formula 1, M1 is one or more selected from B, Ti, W, Nb, Sr, Mo, Mg, P, V, Ta, Ga, and Ca; A is one or more selected from F, Cl, Br, I and S; 0.9≦x≦1.2, 0.6≦a<1, 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である。

[0016] (8) The present invention provides a positive electrode active material according to any one of (1) to (7) above, further comprising a coating portion containing Co formed on the lithium composite transition metal oxide in the form of a single particle.

[0017] (9) The present invention provides the positive electrode active material according to (8), wherein the coating portion further contains Al, Zr, or a combination thereof.

[0018] (10) The present invention provides a method for producing a cathode active material, the method comprising the steps of: (A) mixing a cathode active material precursor, which is a composite transition metal hydroxide, a composite transition metal oxyhydroxide, or a combination thereof, a first lithium-containing raw material, an aluminum-containing raw material, an yttrium-containing raw material, and a zirconium-containing raw material to produce a mixture; (B) primarily firing the mixture at a temperature of 820°C to 950°C to produce a primarily fired product; and (C) selectively mixing a second lithium-containing raw material with the primarily fired product, followed by secondary firing at a temperature of 700°C to 850°C to produce a secondary fired product.

[0019] (11) The present invention provides the method for producing a positive electrode active material according to (10), further comprising, before the step (C), a step (B') of pulverizing the primary fired product.

[0020] (12) The present invention provides a method for producing a positive electrode active material according to (10) or (11), further comprising the step (C') of pulverizing the secondary fired product.

[0021] (13) The present invention provides a method for producing a positive electrode active material according to any one of (10) to (12), further comprising the step of (D) mixing the secondary fired product with a cobalt-containing coating material and then heat-treating the mixture.

[0022] (14) The present invention provides the method for producing a cathode active material according to (13), wherein, when mixing the secondary fired product with the cobalt-containing coating material in step (D), an aluminum-containing coating material, a zirconium-containing coating material, or a combination thereof is further mixed.

[0023] (15) The present invention provides the method for producing a positive electrode active material according to (13) or (14), 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 fired product (A) is 0.01 to 0.03.

[0024] (16) The present invention provides the method for producing a positive electrode active material according to (14), wherein the aluminum-containing coating material is mixed in an amount of 0.03 to 0.10 parts by weight per 100 parts by weight of the secondary fired product.

[0025] (17) The present invention provides the method for producing a positive electrode active material according to any one of the above (13) to (16), wherein the heat treatment is carried out in an oxygen atmosphere.

[0026] (18) The present invention provides the method for producing a positive electrode active material according to any one of the above (13) to (17), wherein the heat treatment is carried out at a temperature of 600°C to 800°C.

[0027] (19) The present invention provides a positive electrode containing the positive electrode active material according to any one of (1) to (9) above.

[0028] (20) The present invention provides a lithium secondary battery comprising the positive electrode according to (19) above, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte. [Effects of the Invention]

[0029] The positive electrode active material of the present invention includes a lithium composite transition metal oxide in the form of a single particle, and the lithium composite transition metal oxide includes Al, Y, and Zr, and can improve the initial efficiency, resistance characteristics, capacity characteristics, life characteristics, etc. of a lithium secondary battery.

[0030] Furthermore, according to the method for producing a positive electrode active material of the present invention, the above-mentioned positive electrode active material can be produced effectively. [Brief explanation of the drawings]

[0031] [Figure 1] 1 shows TEM EDX-Mapping data of the positive electrode active material of Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0032] The present invention will now be described in more detail to facilitate understanding of the present invention.

[0033] The terms and words used in this specification and claims should not be interpreted as being limited to their ordinary or dictionary meanings, but should be interpreted as having meanings and concepts that are consistent with the technical idea of ​​the present invention, based on the principle that inventors can appropriately define the concepts of terms in order to best explain their inventions.

[0034] In this specification, the terms "comprises," "includes," "has," and the like are intended to specify the presence of embodied features, numbers, steps, components, or combinations thereof, but are not intended to preclude the possible presence or addition of one or more different features, numbers, steps, components, or combinations thereof.

[0035] In this specification, the term "on" refers not only to a case where one structure is formed immediately on top of another structure, but also to a case where a third structure is interposed between the structures.

[0036] In this specification, the term "single-particle positive electrode active material" refers to a positive electrode active material consisting of 10 or less primary particles, in contrast to a spherical secondary particle positive electrode active material produced by a conventional method, which is formed by aggregating tens to hundreds of primary particles. Specifically, in the present invention, the single-particle positive electrode active material may be a single particle consisting of one primary particle, or may be a secondary particle formed by aggregating several primary particles.

[0037] The term "primary particle" refers to the smallest particle unit that can be recognized when observing a positive electrode active material through a scanning electron microscope, and the term "secondary particle" refers to a secondary structure formed by aggregation of multiple primary particles.

[0038] As used herein, the term "average particle size (D 50)" means the particle size at 50% of the volume cumulative distribution of particle size. The average particle size is determined by dispersing the powder to be measured in a dispersion medium, introducing it into a commercially available laser diffraction particle size measuring device (for example, S3500 manufactured by Microtrac), measuring the difference in diffraction pattern depending on the particle size when the particles pass through a laser beam, and calculating the particle size distribution. The particle size at 50% of the volume cumulative distribution of particle size in the measuring device is then calculated. 50 can be measured.

[0039] positive electrode active material The present invention provides a positive electrode active material including a lithium composite transition metal oxide in the form of a single particle, the lithium composite transition metal oxide including Al, Y, and Zr. The lithium composite transition metal oxide may have a layered structure.

[0040] The present inventors discovered that when a positive electrode active material includes a lithium composite transition metal oxide in a single particle form and the lithium composite transition metal oxide includes Al, Y, and Zr as dopants, the structural stability of the positive electrode active material is increased, cation mixing is reduced, and the grain size is large, approximately 500 nm to 4 μm, thereby improving the initial efficiency, resistance characteristics, capacity characteristics, and life characteristics of a lithium secondary battery, leading to the completion of the present invention. Specifically, the present inventors discovered that a positive electrode active material in a single particle form with a small average particle size requires Zr and Al as dopants to achieve structural stability, and that when Al is included as a dopant, the grain size does not increase. To solve this problem, the present inventors completed the present invention by simultaneously including Y.

[0041] According to the present invention, the lithium composite transition metal oxide in the form of a single particle has an average particle size (D 50 The average particle diameter (D ) of the lithium composite transition metal oxide may be 2.5 μm to 5.5 μm, specifically 2.5 μm or more, or 3.0 μm or more, and 4.5 μm or less, or 5.5 μm or less. 50) within the above range, the electrochemical performance can be optimized. 50 If the thickness is less than 2.5 μm, there are problems that the battery life characteristics are reduced and the amount of gas generated is increased, and if it exceeds 5.5 μm, there are problems that the capacity characteristics and resistance characteristics of the battery are reduced.

[0042] According to the present invention, the Al may be contained in a content of 500 ppm to 3,000 ppm based on the total weight of the lithium composite transition metal oxide, which stabilizes the internal crystalline structure of the positive electrode active material and improves the capacity and resistance characteristics of the battery.

[0043] According to the present invention, the Y may be contained in a content of 100 ppm to 2,000 ppm based on the total weight of the lithium composite transition metal oxide, in which case the grain size contained in one particle satisfies the range of about 500 nm to 4 μm, thereby improving the capacity characteristics and life characteristics of the battery.

[0044] According to the present invention, the Zr may be contained in a content of 500 ppm to 5,000 ppm based on the total weight of the lithium composite transition metal oxide, in which case Zr is stably doped into the lithium layer, improving structural stability during lithium insertion and desorption, thereby improving the life and resistance characteristics of the battery.

[0045] According to the present invention, the lithium composite transition metal oxide may contain nickel in an amount of 60 mol% or more, specifically 80 mol% or more, and more specifically 85 mol% or more, based on the total moles of metals other than lithium. That is, the lithium composite transition metal oxide may be a high-nickel (High Ni) lithium composite transition metal oxide. In this case, the energy density of a lithium secondary battery can be improved.

[0046] 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.

[0047] [Chemical formula 1] Li x [Ni a Co b Mn c Al d Y e Zr f M1 g ]O 2-y A y

[0048] In the above Chemical Formula 1, M1 is one or more selected from B, Ti, W, Nb, Sr, Mo, Mg, P, V, Ta, Ga, and Ca; A is one or more selected from F, Cl, Br, I and S; 0.9≦x≦1.2, 0.6≦a<1, 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である。

[0049] The a represents the atomic fraction of nickel among the metal elements in the lithium composite transition metal oxide, and may be 0.6≦a<1, 0.8≦a≦0.98, or 0.85≦a≦0.95.

[0050] The b represents the atomic fraction of cobalt among the metal elements in the lithium composite transition metal oxide, and may be 0≦b≦0.4, 0.01≦b≦0.2, or 0.01≦b≦0.15.

[0051] The c represents the atomic fraction of manganese among the metal elements in the lithium composite transition metal oxide, and may be 0≦c≦0.4, 0.01≦c≦0.2, or 0.01≦c≦0.15.

[0052] The d represents the atomic fraction of aluminum among the metal elements in the lithium composite transition metal oxide, and is 0 <d≦0.01、0.002≦d≦0.008または0.003≦d≦0.006であることができる。

[0053] The e represents the atomic fraction of yttrium among the metal elements in the lithium composite transition metal oxide, and is 0 <e≦0.0006、0.0001≦e≦0.0005または0.0002≦e≦0.0003であることができる。

[0054] The f represents the atomic fraction of zirconium among the metal elements in the lithium composite transition metal oxide, and is 0 <f≦0.005、0.001≦f≦0.003または0.001≦f≦0.002であることができる。

[0055] The g represents the atomic fraction of the M1 element among the metal elements in the lithium composite transition metal oxide, and may be 0≦g≦0.2, 0≦g≦0.1, or 0≦g≦0.05.

[0056] According to the present invention, the positive electrode active material may further include a coating portion containing Co formed on the single-particle lithium composite transition metal oxide. The coating portion may further include Al, Zr, or a combination thereof. When the positive electrode active material further includes the coating portion, the amount of residual lithium by-products may be reduced, structural stability may be increased, battery life characteristics and resistance characteristics may be improved, and the amount of gas generation may also be reduced. Here, the coating portion may have the form of a thin film and may be formed entirely or locally on the lithium composite transition metal oxide.

[0057] The Co present in the coating portion may be included in a content of 0.5 mol % to 3 mol % based on the total number of moles of metals other than lithium contained in the lithium composite transition metal oxide, thereby further reducing residual lithium by-products and further improving the lifespan and resistance characteristics.

[0058] The Al present in the coating portion may be contained in a content of 300 ppm to 10,000 ppm based on the total weight of the lithium composite transition metal oxide, which may increase structural stability and further improve life characteristics, resistance characteristics, etc.

[0059] Method for producing positive electrode active material The present invention provides a method for producing the above-mentioned positive electrode active material. That is, the positive electrode active material according to the present invention is produced by the following method for producing a positive electrode active material.

[0060] The method for producing a positive electrode active material according to the present invention includes the steps of: (A) mixing a positive electrode active material precursor, which is a composite transition metal hydroxide, a composite transition metal oxyhydroxide, or a combination thereof, a first lithium-containing raw material, an aluminum-containing raw material, an yttrium-containing raw material, and a zirconium-containing raw material to produce a mixture; (B) primarily firing the mixture at a temperature of 820°C to 950°C to produce a primary fired product; and (C) selectively mixing a second lithium-containing raw material with the primary fired product, followed by secondary firing at a temperature of 700°C to 850°C to produce a secondary fired product.

[0061] The aluminum-containing raw material may be at least one selected from Al(OH)3, Al2O3, AlCl3, Al(NO)3, AlSO4, and Al2S3, specifically at least one selected from Al(OH)3, Al2O3, and Al(NO)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.

[0062] 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 2000 ppm based on the total weight of the positive electrode active material precursor.

[0063] The zirconium-containing source material is Zr(OH)4, ZrO2, Zr(NO3)4, ZrCl4, ZrS2, Zr(SO4)2, and CH 12 The zirconium-containing raw material may be one or more selected from Zr(OH) and ZrO, more specifically, ZrO. The zirconium-containing raw material may be added in an amount of 500 ppm to 5000 ppm based on the total weight of the positive electrode active material precursor.

[0064] When the mixture is primarily fired at a temperature of 820° C. to 950° C., the primary particles of the positive electrode active material precursor are aggregated to produce a primarily fired product in the form of single particles.

[0065] When the primary firing temperature is within the above range, primary particles of the positive electrode active material precursor aggregate to form a structurally stable primary fired product in the form of single particles. When the primary firing temperature is less than 820°C, the primary particles may not aggregate sufficiently, and when it exceeds 950°C, the structurally unstable fired product may have low crystallinity.

[0066] According to the present invention, the primary firing may be performed in an oxygen atmosphere to prevent the lithium transition metal oxide from degenerating into a rock salt structure.

[0067] According to the present invention, the primary firing can be carried out for 3 to 12 hours, specifically 6 to 12 hours, and more specifically 9 to 12 hours, in order to aggregate the primary particles and improve the crystallinity of the primary fired product.

[0068] The primary fired product is subjected to secondary firing at a temperature of 700 to 850°C, whereby lithium is inserted into the primary fired product to produce a secondary fired product, which is a lithium transition metal composite oxide in the form of a single particle.

[0069] When the secondary firing temperature is within the above range, lithium is inserted into the rock salt structure that may be formed on the surface of the primary firing product due to the high temperature during the primary firing, restoring the layered structure and reducing lithium by-products. On the other hand, when the secondary firing temperature is less than 700°C, the low temperature causes a problem of slow lithium insertion rate, and when it exceeds 850°C, the high temperature causes a problem of the surface of the primary firing product degenerating into a rock salt structure, leaving lithium by-products.

[0070] According to the present invention, the secondary firing may be performed in an oxygen atmosphere to prevent the lithium transition metal oxide from degenerating into a rock salt structure.

[0071] According to the present invention, the secondary baking can be carried out for 3 to 12 hours, specifically 6 to 12 hours, and more specifically 9 to 12 hours, in order to increase the crystallinity of the crystal structure inside the positive electrode active material.

[0072] The method for producing a cathode active material according to the present invention may further include, before step (C), a step (B') of pulverizing the primary fired product. In step (B'), the primary fired product is pulverized to an average particle size (D 50 ) can be pulverized to a size of 2.5 μm to 5.5 μm.

[0073] The method for producing a positive electrode active material according to the present invention may further include (C') a step of pulverizing the secondary fired product. two The next fired product was measured to determine the average particle size (D 50 ) can be pulverized to a size of 2.5 μm to 5.5 μm.

[0074] The pulverization in steps (B') and (C') can be carried out using a pin mill, ACM, jet mill, etc. Meanwhile, the pin mill can be carried out at 18,000 rpm, the ACM can be carried out using equipment manufactured by Hosokawa Corporation under conditions of classification at 6,000 rpm and pulverization at 12,000 rpm, and the jet mill can be carried out using equipment manufactured by ZM Solution under conditions of a pulverization pressure of 6 bar and classification at 3,500 rpm.

[0075] The positive electrode active material according to the present invention may be prepared by adding the lithium-containing raw material in two separate steps or all at once. That is, the lithium-containing raw material may be added all at once before the primary firing, or may be added separately before the primary firing and before the secondary firing.

[0076] In the case where the lithium-containing raw material is added twice, the cathode active material according to the present invention can be prepared by, for example, first firing the mixture prepared in step (A) at a temperature of 820°C to 950°C to obtain a first fired product, and then heating the first fired product at room temperature to obtain a particle size (D 50 The second lithium-containing raw material is mixed with the crushed primary fired material and subjected to secondary firing at a temperature of 700°C to 850°C to obtain a secondary fired material, and the secondary fired material is then crushed at room temperature to obtain an average particle size (D 50 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 cathode active material precursor to the number of moles of lithium (Li) contained in the first lithium-containing raw material is 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 cathode 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 to 1:1.10.

[0077] When the lithium-containing raw material is added at once, the cathode active material according to the present invention can be prepared by, for example, first firing the mixture prepared in step (A) at a temperature of 820°C to 950°C, immediately lowering the temperature to 700°C to 850°C (without lowering the temperature to room temperature), and then second firing at a temperature of 700°C to 850°C to obtain a second fired product. The second fired product is then subjected to a process of calcining at room temperature to obtain an average particle size (D 50 ) to 2.5 μm to 5.5 μm. Here, 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 1:1.00 to 1:1.10. In addition, the primary firing temperature may be higher than the secondary firing temperature.

[0078] The method for manufacturing a cathode active material according to the present invention may further include (D) a step of mixing the secondary-calcined product with a cobalt-containing coating material and then heat-treating the mixture, in which case a coating portion containing Co is formed on the secondary-calcined product (single-particle lithium composite transition metal oxide).

[0079] According to the present invention, in step (D), when mixing the secondary fired product with the cobalt-containing coating material, an aluminum-containing coating material, a zirconium-containing coating material, or a combination thereof may be further mixed in. In this case, the coating portion may further contain Al, Zr, or a combination thereof in addition to Co.

[0080] According to the present invention, the cobalt-containing coating material may 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 fired product is 0.01 to 0.03. In this case, there is an advantage that lithium by-products can be controlled in a manufacturing process of a cathode active material that does not include a water washing process.

[0081] The cobalt-containing coating material may be one or more selected from Co(OH)2, Co3O4, CoO, (CH3CO2)2Co, CoCl2, and CoSO4·xH2O, and may be Co(OH)2.

[0082] 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 fired product, thereby ensuring structural stability and improving lifespan, resistance, and gas generation.

[0083] The aluminum-containing coating material may be one or more selected from Al(OH)3, Al2(SO4)3·xH2O, Al2O3, Al(NO3)3·9H2O, AlCl3, and C2H5O4Al, and may be Al(OH)3.

[0084] The zirconium-containing coating material is selected from the group consisting of Zr(OH)4, ZrO2, Zr(NO3)4, ZrCl4, ZrS2, Zr(SO4)2 and CH 12 O8Zr.

[0085] According to the present invention, the heat treatment can be carried out in an oxygen atmosphere to prevent the lithium transition metal oxide from degenerating into a rock salt structure.

[0086] According to the present invention, the heat treatment can be carried out at a temperature of 600°C to 800°C, specifically 650°C to 780°C, and more specifically 680°C to 720°C, so that the coating portion can be formed to an appropriate thickness.

[0087] According to the present invention, the heat treatment can be carried out for 1 to 10 hours, specifically 2 to 8 hours, and more specifically 3 to 6 hours in order to increase the crystallinity of the coating portion.

[0088] positive electrode The present invention provides a positive electrode containing the positive electrode active material.

[0089] The positive electrode may include a positive electrode current collector and a positive electrode active material layer formed on the positive electrode current collector, and the positive electrode active material layer may include the positive electrode active material.

[0090] The positive electrode current collector may include a highly conductive metal, and is not particularly limited as long as it is easily adhered to the positive electrode active material layer and is non-reactive within the voltage range of the battery. Examples of the positive electrode current collector include stainless steel, aluminum, nickel, titanium, calcined carbon, and aluminum or stainless steel whose surfaces are surface-treated with carbon, nickel, titanium, silver, etc. The positive electrode current collector typically has a thickness of 3 μm to 500 μm, and fine irregularities may be formed on the surface of the current collector to enhance the adhesive strength of the positive electrode active material. The positive electrode current collector may be used in various forms, such as a film, sheet, foil, mesh, porous material, foam, or nonwoven fabric.

[0091] The positive electrode active material layer may optionally contain a conductive material and a binder in addition to the positive electrode active material. The positive electrode active material may be contained in an amount of 80 wt % to 99 wt %, more specifically 85 wt % to 98.5 wt %, based on the total weight of the positive electrode active material layer. Within this range, excellent capacity characteristics can be exhibited.

[0092] The conductive material is used to impart conductivity to the electrode. Any conductive material can be used without particular limitations, as long as it does not cause chemical changes in the battery and has electronic conductivity. Specific examples include graphite, such as natural graphite or artificial graphite; carbon-based materials, such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black, and carbon fiber; metal powder or metal fiber, such as copper, nickel, aluminum, and silver; conductive tubes, such as carbon nanotubes; conductive whiskers, such as zinc oxide and potassium titanate; conductive metal oxides, such as titanium oxide; and conductive polymers, such as polyphenylene derivatives. These materials can be used alone or in combination. The conductive material can be present in an amount of 0.1 wt % to 15 wt % based on the total weight of the positive electrode active material layer.

[0093] The binder improves adhesion between positive electrode active material particles and between the positive electrode active material and the current collector. Specific examples of the binder 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 polymer (EPDM), sulfonated EPDM, styrene-butadiene rubber (SBR), fluororubber, polyacrylic acid, polymers in which hydrogen is substituted with Li, Na, or Ca, or various copolymers thereof. These may be used alone or in combination. The binder may be contained in an amount of 0.1% by weight to 15% by weight based on the total weight of the positive electrode active material layer.

[0094] The positive electrode can be manufactured by a conventional method for manufacturing a positive electrode, except for using the positive electrode active material. Specifically, the positive electrode can be manufactured by applying a composition for forming a positive electrode active material layer, which is prepared by dissolving or dispersing the positive electrode active material and, optionally, a binder, a conductive material, and a dispersant in a solvent, onto a positive electrode current collector, followed by drying and rolling, or by casting the composition for forming a positive electrode active material layer onto a separate support, peeling it off from the support, and laminating the resulting film onto a positive electrode current collector.

[0095] The solvent may be a solvent commonly used in the art, such as dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), dimethylformamide (DMF), acetone, or water, and may be used alone or in combination. The amount of the solvent used is sufficient to dissolve or disperse the positive electrode active material, conductive material, binder, and dispersant, taking into consideration the coating thickness of the slurry and the manufacturing yield, and to provide a viscosity that allows excellent thickness uniformity during subsequent coating for manufacturing a positive electrode.

[0096] Lithium secondary battery The present invention provides a lithium secondary battery including the positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte.

[0097] The lithium secondary battery may optionally further include a battery container that houses the electrode assembly of the positive electrode, the negative electrode, and the separator, and a sealing member that seals the battery container.

[0098] The negative electrode may include a negative electrode current collector and a negative electrode active material layer disposed on the negative electrode current collector.

[0099] The negative electrode current collector may be any material that does not cause chemical changes in the battery and has high conductivity, and examples of such materials include copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surfaces treated with carbon, nickel, titanium, silver, or the like, and aluminum-cadmium alloys. The negative electrode current collector typically has a thickness of 3 μm to 500 μm. As with the positive electrode current collector, the current collector may have fine irregularities on its surface to enhance the binding strength of the negative electrode active material. The negative electrode current collector may be used in various forms, such as a film, sheet, foil, mesh, porous material, foam, or nonwoven fabric.

[0100] The negative electrode active material layer may optionally contain a binder and a conductive material in addition to the negative electrode active material.

[0101] The negative electrode active material may be a compound capable of reversible intercalation and deintercalation of lithium. Specific examples thereof include carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber, and amorphous carbon; metallic compounds capable of alloying with lithium such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloys, Sn alloys, and Al alloys; and SiO. βExamples of the negative electrode active material include metal oxides capable of doping and dedoping lithium, such as SnO2, vanadium oxide, and lithium vanadium oxide (0<β<2); and composites containing the metallic compounds and carbonaceous materials, such as Si-C composites and Sn-C composites. These may be used alone or in combination. A thin film of metallic lithium may also be used as the negative electrode active material. The carbon material may be either low-crystalline carbon or high-crystalline carbon. Representative examples of low-crystalline carbon include soft carbon and hard carbon, while representative examples of high-crystalline carbon include amorphous, plate-like, flake-like, spherical, or fibrous natural or artificial graphite, kish graphite, pyrolytic carbon, mesophase pitch-based carbon fiber, mesocarbon microbeads, mesophase pitches, and high-temperature fired carbon such as petroleum or coal tar pitch-derived cokes. The negative electrode active material may be included in an amount of 80 wt% to 99 wt% of the total weight of the negative electrode active material layer.

[0102] The binder in the negative electrode active material layer is a component that helps bind the conductive material, active material, and current collector together, and is typically 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 such binders include polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated EPDM, styrene-butadiene rubber, nitrile-butadiene rubber, fluororubber, and various copolymers thereof.

[0103] The conductive material in the negative electrode active material layer is a component for further improving the conductivity of the negative electrode active material and may be added in an amount of 10 wt % or less, preferably 5 wt % or less, based on the total weight of the negative electrode active material layer. The conductive material is not particularly limited as long as it does not cause chemical changes in the battery and is conductive. Examples of such conductive materials include graphite such as natural graphite and artificial graphite; carbon black such as acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal black; conductive fibers such as carbon fiber and metal fiber; carbon fluoride; metal powders such as aluminum and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives.

[0104] The negative electrode may be manufactured by coating a negative electrode active material layer-forming composition, prepared by dissolving or dispersing a negative electrode active material, and optionally a binder and a conductive material, in a solvent, on a negative electrode current collector and drying the coating. Alternatively, the negative electrode active material layer-forming composition may be cast on a separate support, and then peeled off from the support to obtain a film, which may be laminated on the negative electrode current collector.

[0105] The separator separates the negative electrode and the positive electrode and provides a path for lithium ions to move. Any separator commonly used in lithium secondary batteries can be used without particular limitations. In particular, a separator with low resistance to electrolyte ion movement and excellent electrolyte humidification is preferred. Specifically, a porous polymer film, such as a porous polymer film made of a polyolefin-based polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, or an ethylene / methacrylate copolymer, or a laminate structure of two or more layers thereof can be used. Conventional porous nonwoven fabrics, such as nonwoven fabrics made of high-melting-point glass fibers or polyethylene terephthalate fibers, can also be used. To ensure heat resistance or mechanical strength, a separator coated with a ceramic component or a polymer material can also be used, and can be selectively used in a single-layer or multi-layer structure.

[0106] Examples of the electrolyte include, but are not limited to, organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel-type polymer electrolytes, solid inorganic electrolytes, molten inorganic electrolytes, etc. Specific examples of the electrolyte include an organic solvent and a lithium salt.

[0107] The organic solvent may be any solvent that can act as a medium through which ions involved in the electrochemical reaction of the battery can move. Specifically, examples of the organic solvent include ester solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, and ε-caprolactone; ether solvents such as dibutyl ether and tetrahydrofuran; ketone solvents such as cyclohexanone; aromatic hydrocarbon solvents such as benzene and fluorobenzene; dimethylcarbonate (DMC), diethylcarbonate (DEC), ethylmethylcarbonate (EMC), ethylene carbonate (EC), and propylene carbonate. Examples of solvents that can be used include carbonate-based solvents such as ethylene carbonate (PC), alcohol-based solvents such as ethyl alcohol and isopropyl alcohol, nitriles such as R-CN (where R is a hydrocarbon group having 2 to 20 carbon atoms and having a linear, branched, or cyclic structure, and may contain a double-bonded aromatic ring or an ether bond), amides such as dimethylformamide, dioxolanes such as 1,3-dioxolane, and sulfolanes. Among these, carbonate-based solvents are preferred, and mixtures of cyclic carbonates (e.g., ethylene carbonate or propylene carbonate) with high ionic conductivity and a high dielectric constant, which can improve the charge / discharge performance of batteries, and low-viscosity linear carbonate compounds (e.g., ethyl methyl carbonate, dimethyl carbonate, or diethyl carbonate) are more preferred.

[0108] The lithium salt can be any compound that can provide lithium ions used in lithium secondary batteries without any particular limitations. Specifically, the anion of the lithium salt can be 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 lithium salt may be at least one selected from the group consisting of: 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 concentration of the lithium salt is preferably in the range of 0.1M to 2.0M. When the lithium salt concentration is within this range, the electrolyte has appropriate conductivity and viscosity, thereby exhibiting excellent electrolyte performance and allowing lithium ions to migrate effectively.

[0109] In addition to the electrolyte components, the electrolyte may further contain one or more additives, such as haloalkylene carbonate compounds such as difluoroethylene carbonate, pyridine, triethyl phosphite, triethyl alcohol amine, cyclic ethers, ethylenediamine, n-glyme, hexaphosphoric acid triamide, nitrobenzene derivatives, sulfur, quinoneimine dyes, N-substituted oxazolidinones, N,N-substituted imidazolidines, ethylene glycol dialkyl ethers, ammonium salts, pyrrole, 2-methoxyethyl alcohol, or aluminum trichloride, for the purposes of improving battery life characteristics, suppressing battery capacity reduction, and improving battery discharge capacity. Here, the additives may be contained in an amount of 0.1 wt % to 5 wt % based on the total weight of the electrolyte.

[0110] A lithium secondary battery including the positive electrode active material according to the present invention exhibits excellent initial efficiency, resistance characteristics, capacity characteristics, and life characteristics, and is therefore useful in portable devices such as mobile phones, notebook computers, and digital cameras, and in the field of electric vehicles such as hybrid electric vehicles (HEVs) and electric vehicles (EVs).

[0111] The external shape of the lithium secondary battery of the present invention is not particularly limited, and may be a cylindrical shape using a can, a square shape, a pouch shape, a coin shape, or the like.

[0112] The lithium secondary battery according to the present invention can be used as a battery cell used as a power source for a small device, and can also be preferably used as a unit battery in a medium- to large-sized battery module including a large number of battery cells.

[0113] Thus, a battery module including the lithium secondary battery as a unit cell and a battery pack including the same are provided.

[0114] The battery module or battery pack may be used as a power source for one or more medium- to large-sized devices, such as a power tool; an electric vehicle (EV), a hybrid electric vehicle, and an electric vehicle (PHEV), including a plug-in hybrid electric vehicle; or a power storage system.

[0115] While the present invention may be embodied in various different forms, it is to be understood that the invention is not limited to the specific embodiments set forth herein, and that the invention may be embodied in various different forms without departing from the spirit or scope of the present invention. [Example]

[0116] Examples and Comparative Examples Example 1 Composite transition metal hydroxides (composition: Ni) in the form of secondary particles formed by the aggregation of tens to hundreds of primary particles. 0.885 Co 0.035 Mn 0.08 (OH)2, average particle size (D 50 A mixture was prepared by mixing a composite transition metal hydroxide containing Ni, Co, Mn, and LiOH such that the ratio of the total number of moles of transition metals (Ni, Co, Mn) contained in the composite transition metal hydroxide to the number of moles of lithium (Li) contained in the LiOH ((Ni, Co, Mn, Li)) was 1:0.98. To this mixture was added Al(OH) (manufactured by Dazhou KC Co.) in an amount of 1400 ppm based on the total weight of the composite transition metal hydroxide, YO (manufactured by Neo Performance Co.) in an amount of 1000 ppm based on the total weight of the composite transition metal hydroxide, and ZrO (manufactured by R&F Co.) in an amount of 1500 ppm based on the total weight of the composite transition metal hydroxide.

[0117] The mixture was first fired at 830°C for 6 hours to obtain a first fired product, and the first fired product was then cooled to room temperature to obtain a powder with an average particle size (D 50 ) was crushed to 3.8 μm.

[0118] The crushed primary calcined product and LiOH were mixed so that the ratio of the total number of moles of transition metals (Ni + Co + Mn) contained in the composite transition metal hydroxide to the number of moles of lithium (Li) contained in LiOH ((Ni + Co + Mn):Li) was 1:0.04, and the secondary calcination was performed at 760°C for 9 hours to obtain a secondary calcined product. The secondary calcined product was then crushed at room temperature to obtain a powder with an average particle size (D 50 ) is 3.8 μm. 0.87836 Co 0.03493 Mn 0.07985 Al 0.00499 Y 0.00027 Zr 0.0016 O2) was obtained.

[0119] The single particle lithium composite transition metal oxide was uniformly mixed with Co(OH)2 (manufactured by Huayou Co., Ltd.) and Al(OH)3 (manufactured by Dazhou KC Co., Ltd.), and then heat-treated in an oxygen atmosphere at a temperature of 700°C for 5 hours to obtain a positive electrode active material (composition: LiNi 0.85761 Co 0.05489 Mn 0.07978 Al 0.00586 Y 0.00027 Zr 0.00159 Here, the 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 the 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.

[0120] Example 2 Composite transition metal hydroxides (composition: Ni) in the form of secondary particles formed by the aggregation of tens to hundreds of primary particles. 0.885 Co 0.035 Mn 0.08 (OH)2, average particle size (D 50A mixture was prepared by mixing a composite transition metal hydroxide containing Ni, Co, Mn, and LiOH such that the ratio of the total number of moles of transition metals (Ni, Co, Mn) contained in the composite transition metal hydroxide to the number of moles of lithium (Li) contained in the LiOH ((Ni, Co, Mn, Li)) was 1:0.98. To this mixture was added Al(OH) (manufactured by Dazhou KC Co.) in an amount of 1400 ppm based on the total weight of the composite transition metal hydroxide, YO (manufactured by Neo Performance Co.) in an amount of 2000 ppm based on the total weight of the composite transition metal hydroxide, and ZrO (manufactured by R&F Co.) in an amount of 1500 ppm based on the total weight of the composite transition metal hydroxide.

[0121] The mixture was first fired at 830°C for 6 hours to obtain a first fired product, and the first fired product was then cooled to room temperature to obtain a powder with an average particle size (D 50 ) was crushed to 3.8 μm.

[0122] The crushed primary calcined product and LiOH were mixed so that the ratio of the total number of moles of transition metals (Ni + Co + Mn) contained in the composite transition metal hydroxide to the number of moles of lithium (Li) contained in LiOH ((Ni + Co + Mn):Li) was 1:0.04, and the secondary calcination was performed at 760°C for 9 hours to obtain a secondary calcined product. The secondary calcined product was then crushed at room temperature to obtain a powder with an average particle size (D 50 ) is 3.8 μm. 0.87813 Co 0.03492 Mn 0.07983 Al 0.00499 Y 0.00054 Zr 0.00159 O2) was obtained.

[0123] The single particle lithium composite transition metal oxide was uniformly mixed with Co(OH)2 (manufactured by Huayou Co., Ltd.) and Al(OH)3 (manufactured by Dazhou KC Co., Ltd.), and then heat-treated in an oxygen atmosphere at a temperature of 700°C for 5 hours to obtain a positive electrode active material (composition: LiNi 0.85738 Co 0.05487 Mn 0.07976 Al 0.00586 Y 0.00054 Zr 0.00159Here, the 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 the 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.

[0124] Example 3 Composite transition metal hydroxides (composition: Ni) in the form of secondary particles formed by the aggregation of tens to hundreds of primary particles. 0.885 Co 0.035 Mn 0.08 (OH)2, average particle size (D 50 A mixture was prepared by mixing a composite transition metal hydroxide containing Ni, Co, Mn, and LiOH such that the ratio of the total number of moles of transition metals (Ni, Co, Mn) contained in the composite transition metal hydroxide to the number of moles of lithium (Li) contained in the LiOH ((Ni, Co, Mn, Li)) was 1:0.98. To this mixture was added Al(OH) (manufactured by Dazhou KC Co.) in an amount of 2800 ppm based on the total weight of the composite transition metal hydroxide, YO (manufactured by Neo Performance Co.) in an amount of 1000 ppm based on the total weight of the composite transition metal hydroxide, and ZrO (manufactured by R&F Co.) in an amount of 1500 ppm based on the total weight of the composite transition metal hydroxide.

[0125] The mixture was first fired at 830°C for 6 hours to obtain a first fired product, and the first fired product was then cooled to room temperature to obtain a powder with an average particle size (D 50 ) was crushed to 3.8 μm.

[0126] The crushed primary calcined product and LiOH were mixed so that the ratio of the total number of moles of transition metals (Ni + Co + Mn) contained in the composite transition metal hydroxide to the number of moles of lithium (Li) contained in LiOH ((Ni + Co + Mn):Li) was 1:0.04, and the secondary calcination was performed at 760°C for 9 hours to obtain a secondary calcined product. The secondary calcined product was then crushed at room temperature to obtain a powder with an average particle size (D 50 ) is 3.8 μm. 0.87338 Co 0.03493Mn 0.07985 Al 0.00998 Y 0.00027 Zr 0.00159 O2) was obtained.

[0127] The single particle lithium composite transition metal oxide was uniformly mixed with Co(OH)2 (manufactured by Huayou Co., Ltd.) and Al(OH)3 (manufactured by Dazhou KC Co., Ltd.), and then heat-treated in an oxygen atmosphere at a temperature of 700°C for 5 hours to obtain a positive electrode active material (composition: LiNi 0.85262 Co 0.05489 Mn 0.07978 Al 0.01085 Y 0.00027 Zr 0.00159 Here, the 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 the 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.

[0128] Example 4 Composite transition metal hydroxides (composition: Ni) in the form of secondary particles formed by the aggregation of tens to hundreds of primary particles. 0.885 Co 0.035 Mn 0.08 (OH)2, average particle size (D 50 A mixture was prepared by mixing a composite transition metal hydroxide containing Ni, Co, Mn, and LiOH such that the ratio of the total number of moles of transition metals (Ni, Co, Mn) contained in the composite transition metal hydroxide to the number of moles of lithium (Li) contained in the LiOH ((Ni, Co, Mn, Li)) was 1:0.98. To this mixture was added Al(OH) (manufactured by Dazhou KC Co.) in an amount of 1400 ppm based on the total weight of the composite transition metal hydroxide, YO (manufactured by Neo Performance Co.) in an amount of 1000 ppm based on the total weight of the composite transition metal hydroxide, and ZrO (manufactured by R&F Co.) in an amount of 3500 ppm based on the total weight of the composite transition metal hydroxide.

[0129] The mixture was first fired at 830°C for 6 hours to obtain a first fired product, and the first fired product was then cooled to room temperature to obtain a powder with an average particle size (D 50 ) was crushed to 3.8 μm.

[0130] The crushed primary calcined product and LiOH were mixed so that the ratio of the total number of moles of transition metals (Ni + Co + Mn) contained in the composite transition metal hydroxide to the number of moles of lithium (Li) contained in LiOH ((Ni + Co + Mn):Li) was 1:0.04, and the secondary calcination was performed at 760°C for 9 hours to obtain a secondary calcined product. The secondary calcined product was then crushed at room temperature to obtain a powder with an average particle size (D 50 ) is 3.8 μm. 0.87651 Co 0.03486 Mn 0.07968 Al 0.00498 Y 0.00027 Zr 0.0037 O2) was obtained.

[0131] The single particle lithium composite transition metal oxide was uniformly mixed with Co(OH)2 (manufactured by Huayou Co., Ltd.) and Al(OH)3 (manufactured by Dazhou KC Co., Ltd.), and then heat-treated in an oxygen atmosphere at a temperature of 700°C for 5 hours to obtain a positive electrode active material (composition: LiNi 0.85576 Co 0.05481 Mn 0.07961 Al 0.00585 Y 0.00027 Zr 0.0037 Here, the 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 the 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.

[0132] Comparative Example 1 Composite transition metal hydroxides (composition: Ni) in the form of secondary particles formed by the aggregation of tens to hundreds of primary particles. 0.885 Co0.035 Mn 0.08 (OH)2, average particle size (D 50 A mixture of Ni, Co, Mn, LiOH and Al(OH)3 (manufactured by Dazhou KC Co.) was prepared in an amount of 1400 ppm based on the total weight of the composite transition metal hydroxide, and ZrO2 (manufactured by R&F Co.) was added in an amount of 1500 ppm based on the total weight of the composite transition metal hydroxide.

[0133] The mixture was first fired at 830°C for 6 hours to obtain a first fired product, and the first fired product was then cooled to room temperature to obtain a powder with an average particle size (D 50 ) was crushed to 3.8 μm.

[0134] The crushed primary calcined product and LiOH were mixed so that the ratio of the total number of moles of transition metals (Ni + Co + Mn) contained in the composite transition metal hydroxide to the number of moles of lithium (Li) contained in LiOH ((Ni + Co + Mn):Li) was 1:0.04, and the secondary calcination was performed at 760°C for 9 hours to obtain a secondary calcined product. The secondary calcined product was then crushed at room temperature to obtain a powder with an average particle size (D 50 ) is 3.8 μm. 0.8786 Co 0.03494 Mn 0.07987 Al 0.00499 Zr 0.0016 O2) was obtained.

[0135] The single particle lithium composite transition metal oxide was uniformly mixed with Co(OH)2 (manufactured by Huayou Co., Ltd.) and Al(OH)3 (manufactured by Dazhou KC Co., Ltd.), and then heat-treated in an oxygen atmosphere at a temperature of 700°C for 5 hours to obtain a positive electrode active material (composition: LiNi 0.85784 Co 0.0549 Mn 0.0798 Al 0.00586 Zr 0.0016Here, the 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 the 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.

[0136] Comparative Example 2 Composite transition metal hydroxides (composition: Ni) in the form of secondary particles formed by the aggregation of tens to hundreds of primary particles. 0.885 Co 0.035 Mn 0.08 (OH)2, average particle size (D 50 A mixture was prepared by mixing a composite transition metal hydroxide containing 1000 ppm of Y2O3 (manufactured by Neo Performance) and 1500 ppm of ZrO2 (manufactured by R&F) based on the total weight of the composite transition metal hydroxide.

[0137] The mixture was first fired at 830°C for 6 hours to obtain a first fired product, and the first fired product was then cooled to room temperature to obtain a powder with an average particle size (D 50 ) was crushed to 3.8 μm.

[0138] The crushed primary calcined product and LiOH were mixed so that the ratio of the total number of moles of transition metals (Ni + Co + Mn) contained in the composite transition metal hydroxide to the number of moles of lithium (Li) contained in LiOH ((Ni + Co + Mn):Li) was 1:0.04, and the secondary calcination was performed at 760°C for 9 hours to obtain a secondary calcined product. The secondary calcined product was then crushed at room temperature to obtain a powder with an average particle size (D 50 ) is 3.8 μm. 0.88336 Co 0.03493 Mn 0.07985 Y 0.00027 Zr 0.00159O2) was obtained.

[0139] The single particle lithium composite transition metal oxide was uniformly mixed with Co(OH)2 (manufactured by Huayou Co., Ltd.) and Al(OH)3 (manufactured by Dazhou KC Co., Ltd.), and then heat-treated in an oxygen atmosphere at a temperature of 700°C for 5 hours to obtain a positive electrode active material (composition: LiNi 0.86259 Co 0.05489 Mn 0.07978 Al 0.00088 Y 0.00027 Zr 0.00159 Here, the 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 the 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.

[0140] Comparative Example 3 Composite transition metal hydroxides (composition: Ni) in the form of secondary particles formed by the aggregation of tens to hundreds of primary particles. 0.885 Co 0.035 Mn 0.08 (OH)2, average particle size (D 50 A mixture of Ni, Co, Mn, and LiOH was prepared by mixing the composite transition metal hydroxide (Ni, Co, Mn, Li) and LiOH such that the ratio of the total number of moles of transition metals (Ni, Co, Mn) contained in the composite transition metal hydroxide to the number of moles of lithium (Li) contained in the LiOH ((Ni, Co, Mn, Li)) was 1:0.98. To the mixture was added 1400 ppm of Al(OH)3 (manufactured by Dazhou KC Co.) based on the total weight of the composite transition metal hydroxide, and 1000 ppm of Y2O3 (manufactured by Neo Performance Co.) based on the total weight of the composite transition metal hydroxide, and the mixture was mixed to prepare a mixture.

[0141] The mixture was first fired at 830°C for 6 hours to obtain a first fired product, and the first fired product was then cooled to room temperature to obtain a powder with an average particle size (D 50 ) was crushed to 3.8 μm.

[0142] The crushed primary calcined product and LiOH were mixed so that the ratio of the total number of moles of transition metals (Ni + Co + Mn) contained in the composite transition metal hydroxide to the number of moles of lithium (Li) contained in LiOH ((Ni + Co + Mn):Li) was 1:0.04, and the secondary calcination was performed at 760°C for 9 hours to obtain a secondary calcined product. The secondary calcined product was then crushed at room temperature to obtain a powder with an average particle size (D 50 ) is 3.8 μm. 0.87976 Co 0.03499 Mn 0.07998 Al 0.005 Y 0.00027 O2) was obtained.

[0143] The single particle lithium composite transition metal oxide was uniformly mixed with Co(OH)2 (manufactured by Huayou Co., Ltd.) and Al(OH)3 (manufactured by Dazhou KC Co., Ltd.), and then heat-treated in an oxygen atmosphere at a temperature of 700°C for 5 hours to obtain a positive electrode active material (composition: LiNi 0.85901 Co 0.05494 Mn 0.07991 Al 0.00587 Y 0.00027 Here, the 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 the 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.

[0144] Experimental example Experimental Example 1: Analysis of positive electrode active material In order to confirm how the dopants Al, Y, and Zr are present in the positive electrode active material prepared in Example 1 and how the coating portion containing Co and Al is formed, a TEM (Transmission Electron Microscope) (Titan Bulb G2 600-300) EDX-Mapping analysis was performed, and the TEM EDX-Mapping data is shown in FIG. 1.

[0145] Referring to FIG. 1, in the case of the cathode active material prepared in Example 1, it can be seen that the dopants Al, Y, and Zr are uniformly distributed without any concentration gradient within the particles, and that a coating containing Co and Al is formed on the surface of the particles in the form of a thin film.

[0146] Experimental Example 2: Confirmation of the amount of residual lithium present in the secondary fired product The amount of residual lithium present in each of the secondary fired products produced in Examples 1 to 4 and Comparative Examples 1 to 3, that is, the contents of Li2CO3 and LiOH, was confirmed by the following method.

[0147] Specifically, 5 g of each of the secondary fired products produced in Examples 1 to 4 and Comparative Examples 1 to 3 was added to 100 g of distilled water, mixed for 5 minutes, and then filtered. After filtering, the amounts of Li2CO3 and LiOH dissolved in the distilled water were measured by titration (using 0.1 N HCl) using a pH meter, and the results are shown in Table 1.

[0148] [Table 1]

[0149] Experimental Example 3: Evaluation of battery characteristics The positive electrode active materials prepared in Examples 1 to 4 and Comparative Examples 1 to 3, carbon black conductive material, and polyvinylidene fluoride (PVDF) binder were mixed in an N-methylpyrrolidone (NMP) solvent at a ratio of 96:2:2 to prepare positive electrode slurries. The positive electrode slurries were applied to one side of an aluminum current collector, dried at 150°C, and rolled to prepare positive electrodes.

[0150] A lithium metal electrode was used as the negative electrode, and a porous polyethylene separator was interposed between the positive and negative electrodes to prepare an electrode assembly. The electrode assembly was then placed inside a battery case, and an electrolyte solution was injected into the case to prepare a half-cell. The electrolyte solution was prepared by dissolving 1.0 M LiPF6 in an organic solvent mixture of ethylene carbonate (EC): ethyl methyl carbonate (EMC): diethyl carbonate (DEC) in a volume ratio of 3:4:3.

[0151] Each half-cell thus prepared was charged at 0.1 C in CC-CV mode at 25°C to 4.3 V, and then discharged at a constant current of 0.1 C to 3.0 V, while measuring the initial charge capacity and initial discharge capacity. The initial efficiency and DC internal resistance (DCIR) were calculated and are shown in Table 2 below. For reference, the initial efficiency value is the percentage value of the initial discharge capacity relative to the initial charge capacity, and the DCIR value is calculated by dividing the difference between the voltage at 60 seconds and the initial voltage while discharging at a constant current of 0.1 C by the applied current.

[0152] The capacity of the lithium secondary battery was measured by repeating 50 charge-discharge cycles at 45°C and in the range of 3.0 to 4.25 V at a constant current of 0.33 C, and the capacity retention rate was calculated as the percentage of the discharge capacity at the 50th cycle relative to the discharge capacity at the first cycle, and this is shown in Table 2 below. The resistance increase rate was calculated as the percentage of DCIR, which was calculated by dividing the voltage drop (ΔV) for 60 seconds at the 50th discharge cycle by the current, relative to DCIR, which was calculated by dividing the voltage drop (ΔV) for 60 seconds at the first discharge cycle by the current, and this is shown in Table 2 below.

[0153] [Table 2]

[0154] Referring to Table 2, it can be seen that the batteries containing the positive electrode active materials of Examples 1 to 4 have high initial efficiency and capacity retention rate, and low initial resistance and resistance increase rate.

[0155] In contrast, the positive electrode active material of Comparative Example 1 does not contain Y, which causes problems with grain growth, and it can be confirmed that the initial efficiency and capacity retention characteristics of the battery containing this are reduced. Also, the positive electrode active material of Comparative Example 2 does not contain Al, which causes high defects and increased cation mixing, which can be confirmed that the initial efficiency and capacity retention characteristics of the battery containing this are reduced. Also, the positive electrode active material of Comparative Example 3 does not contain Zr, which maintains structural stability, and it can be confirmed that the initial resistance and resistance increase rate are high.

Claims

1. It contains a lithium composite transition metal oxide in the form of a single particle, the lithium transition metal composite oxide contains Al, Y, and Zr; The lithium composite transition metal oxide has a single particle shape, and the coating portion includes Co and is formed on the single particle shape of the lithium composite transition metal oxide. The lithium composite transition metal oxide is a positive electrode active material having a composition represented by the following chemical formula 1: [Chemical formula 1] Li x [Nia Co b Mn c Al d Y e Zr f M1 g ] O 2-y A y In the above Chemical Formula 1, M1 is one or more selected from B, Ti, W, Nb, Sr, Mo, Mg, P, V, Ta, Ga, and Ca; A is one or more selected from F, Cl, Br, I and S; 0.9≦x≦1.2, 0.6≦a<1, 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.

2. The lithium composite transition metal oxide has an average particle size (D ５０ 2. The positive electrode active material according to claim 1, wherein the average particle size is 2.5 μm to 5.5 μm.

3. 2. The positive electrode active material according to claim 1, wherein the Al is contained in an amount of 500 ppm to 3,000 ppm based on the total weight of the lithium composite transition metal oxide.

4. 2. The positive electrode active material according to claim 1, wherein the Y is contained in an amount of 100 ppm to 2,000 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 Zr is contained in an amount of 500 ppm to 5,000 ppm based on the total weight of the lithium composite transition metal oxide.

6. 2. The positive electrode active material according to claim 1, wherein the lithium composite transition metal oxide contains nickel in an amount of 60 mol% or more relative to the total number of moles of metals other than lithium.

7. The positive electrode active material of claim 1 , wherein the coating further comprises Al, Zr, or a combination thereof.

8. (A) mixing a positive electrode active material precursor, which is a composite transition metal hydroxide, a composite transition metal oxyhydroxide, or a combination thereof, a first lithium-containing source material, an aluminum-containing source material, an yttrium-containing source material, and a zirconium-containing source material to produce a mixture; (B) primary firing the mixture at a temperature of 820°C to 950°C to produce a primary fired product; (C) selectively mixing a second lithium-containing raw material with the primary fired product, and then secondary firing at a temperature of 700°C to 850°C to produce a secondary fired product.

9. The method for producing a positive electrode active material according to claim 8 , further comprising, before step (C), (B′) pulverizing the primary fired product.

10. The method for producing a positive electrode active material according to claim 8 , further comprising: (C′) a step of pulverizing the secondary fired product.

11. The method for producing a positive electrode active material according to claim 8 , further comprising the step (D) of heat-treating the secondary fired product after mixing the secondary fired product with the cobalt-containing coating material.

12. 12. The method of claim 11, wherein when mixing the secondary fired product with the cobalt-containing coating material in step (D), an aluminum-containing coating material, a zirconium-containing coating material, or a combination thereof is further mixed.

13. The cobalt-containing coating material is 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 (A) of metals other than lithium contained in the secondary fired product is 0.01 to 0.

03. The method for producing a positive electrode active material according to claim 11.

14. The method for producing a positive electrode active material according to claim 12, wherein the aluminum-containing coating material is mixed in an amount of 0.03 to 0.10 parts by weight based on 100 parts by weight of the secondary fired product.

15. The method for producing a positive electrode active material according to claim 11 , wherein the heat treatment is carried out in an oxygen atmosphere.

16. The method for producing a positive electrode active material according to claim 11, wherein the heat treatment is carried out at a temperature of 600°C to 800°C.

17. A positive electrode comprising the positive electrode active material according to claim 1 .

18. The positive electrode according to claim 17 ; a negative electrode; a separator interposed between the positive electrode and the negative electrode; and an electrolyte.

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