Positive electrode active material for lithium secondary batteries and lithium secondary batteries containing the same

Abstract

This embodiment relates to a positive electrode active material for a lithium secondary battery and a lithium secondary battery containing the same. The positive electrode active material for a lithium secondary battery according to one embodiment includes a single-particulate metal oxide containing 0.8 moles or more of nickel based on 1 mole of total metal excluding lithium; and a coating layer containing cobalt located on the surface of the metal oxide; wherein the metal oxide on which the coating layer is formed may have a particle size Dn10 of 1.1 μm or more for particles corresponding to 10% of the cumulative distribution of particle numbers.

Description

[Technical Field]

[0001] This embodiment relates to a positive electrode active material for a lithium secondary battery and a lithium secondary battery containing the same. [Background technology]

[0002] Recently, driven by the explosive demand for electric vehicles and the need for increased driving range, the development of high-capacity, high-energy-density secondary batteries to meet these needs is being actively pursued worldwide.

[0003] To meet these requirements, a technology has been proposed that uses a high-nickel NCM cathode material with a high Ni content and configured as secondary particles.

[0004] However, increasing the nickel content reduces particle strength, leading to microcracks during charging and discharging. This increases the specific surface area of ​​the positive electrode material, increasing the reaction with the electrolyte and thus increasing gas generation. Additionally, the weak strength of the secondary particles causes them to break during the electrode rolling process, increasing the amount of fine powder generated and degrading the battery's lifespan.

[0005] To address this, a proposal was made to increase the particle strength by increasing the size of the primary particles to the maximum extent possible and manufacturing the cathode material in single-particle form, thereby reducing the specific surface area.

[0006] However, in general, manufacturing single-particle cathode materials requires firing secondary particles at high temperatures. This often leads to over-firing, which causes crystal defects in the layered structure, resulting in a decrease in power output and lifetime characteristics. [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] In this embodiment, we aim to provide a positive electrode active material for lithium secondary batteries with excellent output and lifespan characteristics, and a lithium secondary battery containing the same. [Means for solving the problem]

[0008] According to one embodiment, the positive electrode active material for a lithium secondary battery includes a single-particulate metal oxide containing 0.8 moles or more of nickel based on 1 mole of total metal excluding lithium; and a coating layer containing cobalt located on the surface of the metal oxide; wherein the metal oxide on which the coating layer is formed may have a particle size Dn10 of 1.1 μm or more for particles corresponding to 10% of the cumulative distribution of particle numbers.

[0009] A positive electrode for a lithium secondary battery according to another embodiment may include a positive electrode active material according to one embodiment.

[0010] A lithium secondary battery according to another embodiment may include the positive electrode for the lithium secondary battery according to one embodiment. [Effects of the Invention]

[0011] According to this embodiment, the high-temperature life of the battery can be significantly improved by controlling the fineness of the particles to a certain level or higher based on the cumulative distribution of the number of particles in the single-particulate metal oxide. More specifically, when the particle size Dn10 of the particles corresponding to 10% of the cumulative distribution of the number of particles in the single-particulate metal oxide on which the coating layer is formed is 1.1 μm or larger, excellent high-temperature life and resistance characteristics of the lithium secondary battery can be ensured. [Brief explanation of the drawing]

[0012] [Figure 1] Figure 1 shows the particle size based on the cumulative distribution of particle numbers for the positive electrode active material produced in Examples 1 to 4 and Comparative Examples 1 to 2. [Modes for carrying out the invention]

[0013] The terms first, second, third, etc., are used to describe various parts, components, regions, layers, and / or sections, but are not limited to these. These terms are used solely to distinguish one part, component, region, layer, or section from other parts, components, regions, layers, or sections. Accordingly, the first part, component, region, layer, or section described below may be referred to as the second part, component, region, layer, or section, to the extent that it does not fall outside the scope of the present invention.

[0014] The technical terms used herein are for the sole purpose of referring to specific embodiments and are not intended to limit the invention. The singular forms used herein also include plural forms unless the text explicitly indicates otherwise. The meaning of “including” as used in this specification does not embody a particular characteristic, area, integer, step, operation, element, and / or component, thereby excluding the presence or addition of other characteristics, areas, integers, steps, operations, elements, and / or components.

[0015] When we say that one part is "on top of" another part, it means that it is either directly on top of the other part or that the other part is between them. In contrast, when we say that one part is "directly on top of" another part, it means that the other part is not between them.

[0016] Unless otherwise defined, all terms used herein, including technical and scientific terms, have the same meaning as those generally understood by a person of ordinary skill in the art to which this invention pertains. Terms defined in commonly used dictionaries are additionally interpreted to have the meaning consistent with the relevant technical literature and the present disclosure, and are not interpreted in an ideal or highly formal sense unless otherwise defined.

[0017] Also, unless otherwise specified, % refers to weight percent, and 1 ppm is 0.0001 weight percent.

[0018] As used herein, the term "these combinations" described in the MAXI format expression means one or more mixtures or combinations selected from the group of components described in the MAXI format expression, and means including any one or more selected from the group of components.

[0019] Hereinafter, embodiments of the present invention will be described in detail so that those having ordinary knowledge in the technical field to which the present invention pertains can easily implement them. However, the present invention can be realized in various different forms and is not limited to the embodiments described herein.

[0020] Positive electrode active material for lithium secondary battery As described above, the single-particle positive electrode active material has a problem that over-firing occurs, defects occur in the layered crystal structure, and the characteristics of output and high-temperature life deteriorate.

[0021] However, in this embodiment, such a problem is solved by controlling the particle size Dn10 of the particles corresponding to 10% of the cumulative distribution of the number of particles of the single-particle metal oxide formed with the coating layer to be 1.1 μm or more.

[0022] Specifically, the positive electrode active material for a lithium secondary battery according to one embodiment includes a single-particle metal oxide containing 0.8 mol or more of nickel based on 1 mol of the total metal excluding lithium; and a coating layer containing cobalt located on the surface of the metal oxide; and the metal oxide formed with the coating layer may have a particle size Dn10 of the particles corresponding to 10% of the cumulative distribution of the number of particles of 1.1 μm or more.

[0023] As used herein, a single particle is a single crystal structure composed of one particle or a form in which about 2 to 20 or about 2 to 10 particles are aggregated, and when observing the cross-section of the powder through a scanning electron microscope (SEM), it can include at least one structure classified as one lump. Here, one particle means one grain or crystallite.

[0024] As in this embodiment, the single-particle active material has a smaller specific surface area compared to conventional secondary-particle positive electrode active materials formed by the aggregation of tens to hundreds of primary particles. This reduces the amount of gas generated by side reactions with the electrolyte, and its higher particle strength suppresses particle cracking during rolling, thus reducing crack formation due to repeated charging and discharging. As a result, it offers superior lifespan and safety compared to secondary particles, and enables the realization of high energy density in the electrode.

[0025] However, in general, with single-particle active materials, the lithium ion migration distance can increase as the size of the crystal grains increases, which in turn leads to a problem of reduced capacity and high-temperature lifetime characteristics.

[0026] However, in the present invention, by controlling the fine powder content so that the particle size Dn10 of particles corresponding to 10% of the cumulative particle number distribution of the metal oxide on which the coating layer is formed is 1.1 μm or larger, more specifically in the range of 1.1 μm to 2.0 μm, a positive electrode active material with excellent high-temperature lifetime characteristics can be realized.

[0027] In this embodiment, the metal oxide on which the coating layer is formed can also satisfy the following formula 1.

[0028] [Formula 1] 1.1 ≤ Dv10 / Dn10 ≤ 2.2

[0029] In this embodiment, the metal oxide on which the coating layer is formed can also satisfy the following formula 2.

[0030] [Formula 2] 0.5 μm ≤ Dv10 - Dn10 ≤ 1.2 μm

[0031] In equations 1 and 2 above, Dv10 is the particle size distribution obtained from the volume of the metal oxide on which the coating layer is formed, and is the average particle size of the particles corresponding to the cumulative percentage of volume of 10%, while Dn10 is the average particle size of the particles at the point corresponding to 10% of the cumulative distribution of the number of particles when the metal oxide on which the coating layer is formed is accumulated from the smallest particles.

[0032] The volume-based average particle size Dv10 and the number-based average particle size Dn10 can be measured, for example, using the laser diffraction method.

[0033] Next, the metal oxide on which the coating layer is formed may have a particle size Dnmin of the particle corresponding to the minimum cumulative distribution of particle numbers of 1.0 μm or larger, more specifically, in the range of 1.0 μm to 1.4 μm.

[0034] In this embodiment, the positive electrode active material can dramatically improve the high-temperature lifespan characteristics of a lithium secondary battery by controlling the fine powder content to satisfy the particle size Dnmin, which corresponds to the minimum cumulative distribution of particle numbers, and equations 1 and / or 2.

[0035] Furthermore, the average particle size Dv50 of the metal oxide on which the coating layer is formed may be 5 μm or less, more specifically, in the range of 2 μm to 5 μm.

[0036] On the other hand, the single-particulate metal oxide may contain 0.8 moles or more of nickel based on 1 mole of total metal excluding lithium. The nickel content may be 0.8 moles or more, more specifically, in the range of 0.8 to 0.99 moles, 0.82 to 0.95 moles, or 0.82 to 0.93 moles, based on 1 mole of total metal excluding lithium. When the nickel content satisfies the above range, a high-capacity battery can be realized.

[0037] As mentioned above, single-particle positive electrode active materials are manufactured by firing at higher temperatures compared to conventional secondary-particle positive electrode active materials, which can lead to the occurrence of layered crystal defects. In this embodiment, by forming a coating layer containing cobalt on the surface of the metal oxide as described above, it is possible to prevent crystal defects such as an increase in the cation mixing ratio due to high-temperature firing, and to efficiently increase the crystal grain size within the single particle and the average particle size of the single particle during the firing process.

[0038] The cobalt content in the coating layer may be in the range of 0.035 moles to 0.08 moles, more specifically, 0.05 moles to 0.07 moles, based on the total metal content of the single-particulate metal oxide excluding lithium. When the cobalt content in the coating layer satisfies the above range, the crystal grains can be grown to an appropriate size, and the production cost can be appropriately adjusted, resulting in excellent economic efficiency.

[0039] Next, the coating layer may further contain aluminum. When aluminum is included in the coating layer along with cobalt, the output characteristics can be further improved.

[0040] On the other hand, in the positive electrode active material of this embodiment, the metal oxide may further contain cobalt and manganese. Here, the cobalt content in the metal oxide may be 0.05 moles or less, more specifically, greater than 0 and 0.05 moles or less, based on 1 mole of total metal excluding lithium.

[0041] Furthermore, the manganese content may be 0.1 moles or less, more specifically, in the range of 0.05 moles to 0.1 moles, based on 1 mole of total metal excluding lithium.

[0042] The metal oxide may further contain doping elements.

[0043] Here, the doping element may include, for example, at least one of Y, Al, Zr, Nb, Mo, W, Ti, Ce, Mg, B, P, V, Sr, and B. In this embodiment, the doping element may include, for example, Y, Al, and Zr.

[0044] At this time, the content of the doping element may be 0 or more and 0.2 moles or less, based on 1 mole of the total metal excluding lithium, more specifically in the range of 0.0005 moles to 0.1 moles, 0.0005 moles to 0.08 moles, 0.0005 moles to 0.04 moles, or 0.001 moles to 0.03 moles. Specifically, based on 1 mole of the total metal excluding lithium, the content of Y may be in the range of 400 ppm to 2,000 ppm, the content of Al may be in the range of 200 ppm to 1,800 ppm, and the content of Zr may be in the range of 1,200 ppm to 2,800 ppm.

[0045] In this embodiment, the doping element content refers to the amount of doping element contained in the final cathode active material.

[0046] positive electrode In other embodiments, a current collector and a positive electrode are provided, which is located on one surface of the current collector and includes a positive electrode active material layer containing the positive electrode active material manufactured according to the above-described embodiment.

[0047] The characteristics of the positive electrode active material constituting the positive electrode active material layer are the same as those described above. Therefore, a detailed explanation of the positive electrode active material will be omitted.

[0048] The current collector can be made of, for example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel with a surface treatment of carbon, nickel, titanium, silver, etc.

[0049] On the other hand, the positive electrode active material layer may include a binder and a conductive material.

[0050] At this time, the binder plays a role in improving the adhesion between positive electrode active material particles and the adhesion between the positive electrode active material and the positive electrode current collector. Specific examples include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer rubber (EPDM rubber), sulfonated EPDM, styrene-butadiene rubber (SBR), fluororubber, or various copolymers thereof, and one of these alone or a mixture of two or more can be used, but is not limited thereto. The binder may be included in an amount of 1 to 30% by weight relative to the total weight of the positive electrode active material layer.

[0051] The conductive material is used to impart conductivity to the electrodes and can be used without special limitations as long as it has electronic conductivity without causing chemical changes in the battery it is configured in. 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 powders or metal fibers such as copper, nickel, aluminum, and silver; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives. One of these can be used alone or a mixture of two or more, but it is not limited to these. The conductive material may usually be included in an amount of 1 to 30% by weight relative to the total weight of the positive electrode active material layer.

[0052] The positive electrode can be manufactured by a conventional positive electrode manufacturing method, except that the positive electrode active material is used.

[0053] Specifically, the positive electrode can be manufactured by applying a composition for forming a positive electrode active material layer, which includes the positive electrode active material described above and optionally a binder, conductive material, or solvent, onto a positive electrode current collector, followed by drying and rolling. At this time, the types and contents of the positive electrode active material, binder, and conductive material are the same as described above.

[0054] The solvent may be any solvent commonly used in the art, such as dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, or water. One of these can be used alone or a mixture of two or more. The amount of solvent used should be sufficient to dissolve or disperse the cathode active material, conductive material, and binder, taking into consideration the coating thickness and production yield of the slurry, and to have a viscosity that allows for excellent thickness uniformity when applied for cathode manufacturing.

[0055] Alternatively, the positive electrode can also be manufactured by casting the positive electrode active material layer forming composition onto a separate support, peeling it off the support, and then laminating the resulting film onto the positive electrode current collector.

[0056] Lithium-ion rechargeable battery Another embodiment provides a lithium secondary battery including the positive electrode.

[0057] The lithium secondary battery may specifically include a positive electrode, a negative electrode positioned opposite the positive electrode, a separator interposed between the positive and negative electrodes, and an electrolyte, wherein the positive electrode is the same as described above. The lithium secondary battery may also selectively further include a battery container housing the electrode assembly including the positive electrode, negative electrode, and separator, and a sealing member for sealing the battery container.

[0058] In the lithium secondary battery, the negative electrode may include a negative electrode current collector and a negative electrode active material layer located on the negative electrode current collector.

[0059] The negative electrode current collector is not particularly limited as long as it has high conductivity without causing chemical changes to the battery. For example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., and aluminum-cadmium alloy can be used. The negative electrode current collector can also typically have a thickness of 3 to 500 μm, and, similar to the positive electrode current collector, fine irregularities can be formed on the surface of the current collector to strengthen the bonding force of the negative electrode active material. For example, it can be used in a variety of forms such as films, sheets, foils, nets, porous materials, foams, and nonwoven fabrics.

[0060] The negative electrode active material layer may selectively include a binder and a conductive material along with the negative electrode active material. The negative electrode active material layer can also be manufactured, for example, by applying a negative electrode active material layer forming composition, which includes the negative electrode active material and selectively a binder and a conductive material, onto a negative electrode current collector and drying it, or by casting the negative electrode forming composition onto a separate support, peeling it off the support, and laminating the resulting film onto the negative electrode current collector.

[0061] As the negative electrode active material, compounds capable of reversible intercalation and deintercalation of lithium can be used. Specific examples include carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber, and amorphous carbon; metallic compounds capable of alloying with lithium, such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloys, Sn alloys, or Al alloys; and SiO2. βExamples include lithium-doped and dedoped metal oxides such as (0<β<2), SnO2, vanadium oxide, and lithium vanadium oxide; or composites containing the metallic compound and carbonaceous material, such as Si-C composites or Sn-C composites. One or more of these can be used as a mixture. A metallic lithium thin film can also be used as the negative electrode active material. In addition, both low-crystalline carbon and high-crystalline carbon can be used as the carbon material. Typical examples of low-crystalline carbon include soft carbon and hard carbon, while typical 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, meso-carbon microbeads, mesophase pitches, and high-temperature calcined carbon such as petroleum or coal tar pitch-derived cokes.

[0062] The binder and conductive material may be the same as those described for the positive electrode.

[0063] Next, depending on the type of lithium secondary battery, a separator may be present between the positive and negative electrodes. Such a separator may be polyethylene, polypropylene, polyvinylidene fluoride, or a multilayer film of two or more layers thereof. Mixed multilayer films such as a polyethylene / polypropylene two-layer separator, a polyethylene / polypropylene / polyethylene three-layer separator, or a polypropylene / polyethylene / polypropylene three-layer separator may also be used.

[0064] Furthermore, in the lithium secondary battery, the electrolyte can be an organic liquid electrolyte, an inorganic liquid electrolyte, a solid polymer electrolyte, a gel-type polymer electrolyte, a solid inorganic electrolyte, or a molten inorganic electrolyte, which can be used in the manufacture of lithium secondary batteries, and is not limited to these.

[0065] Specifically, the organic liquid electrolyte may contain an organic solvent and a lithium salt.

[0066] The organic solvent can be any solvent that can act as a medium through which ions involved in the electrochemical reaction of the battery can move, without any special limitations. Specifically, the organic solvent may be an ester solvent such as methyl acetate, ethyl acetate, γ-butyrolactone, or ε-caprolactone; or dibutyl ether. Other solvents that can be used include ether solvents such as 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), methyl ethyl carbonate (MEC), ethyl methyl carbonate (EMC), ethylene carbonate (EC), and propylene carbonate (PC); alcohol solvents such as ethyl alcohol and isopropyl alcohol; tolyls such as R-CN (where R is a linear, branched, or cyclic hydrocarbon group of C2 to C20, and can include a double-bonded aromatic ring or ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; or sulfolanes. Among these, carbonate-based solvents are preferred, and more preferably, a mixture of a cyclic carbonate (e.g., ethylene carbonate or propylene carbonate) having high ionic conductivity and high dielectric constant, which can improve the charge and discharge performance of the battery, and a low-viscosity linear carbonate compound (e.g., ethyl methyl carbonate, dimethyl carbonate, or diethyl carbonate). In this case, mixing the cyclic carbonate and the linear carbonate in a volume ratio of about 1:1 to about 1:9 can produce an electrolyte with excellent performance.

[0067] The lithium salt can be any compound capable of providing lithium ions for use in lithium secondary batteries, without any special limitations. Specifically, the lithium salt can be LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAlO4, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2, LiCl, LiI, or LiB(C2O4)2, etc. The concentration of the lithium salt is preferably within the range of 0.1 to 2.0 M. When the concentration of the lithium salt is within this range, the electrolyte has appropriate conductivity and viscosity, so it can exhibit excellent electrolyte performance and lithium ions can move effectively.

[0068] As described above, the lithium secondary battery containing the positive electrode active material according to the present invention exhibits excellent discharge capacity, output characteristics, and capacity retention rate stably, making it useful in portable devices such as mobile phones, laptop computers, and digital cameras, as well as in the electric vehicle field, such as hybrid electric vehicles (HEVs). [Examples]

[0069] The following describes embodiments of the present invention in detail. However, these are presented as examples only and do not limit the present invention; rather, the present invention is defined solely by the scope of the claims described below.

[0070] Example 1 (1) Manufacturing of positive electrode active material Ni 0.87 Co 0.03 Mn 0.10 After preparing a precursor with an (OH)2 composition, a mixture was produced by uniformly mixing the precursor with LiOH·H2O (SAMCHUN CHEMICALS, battery grade) as a lithium raw material, and Y2O3, ZrO2, and Al(OH)3 as doping raw materials.

[0071] At this time, the molar ratio of lithium (Li) to the total metal (Me) excluding lithium was designed to be 1.05, and based on the precursor, doping raw material substances were introduced so that Zr was 2000 ppm, Y was 1200 ppm, and Al was 1000 ppm.

[0072] After the mixture was put into a firing furnace in an oxygen atmosphere, it was pre-fired at 680 °C for 6.5 hours to obtain a pre-fired product. Then, after the obtained pre-fired product was put into a firing furnace in an oxygen atmosphere, the temperature was raised, and it was fired at 880 °C for 3 hours (1 st step), and then fired at 940 °C for 1 hour (2 nd step), and then fired at 780 °C for 11 hours (3 rd step) by a three-step method to obtain a fired product.

[0073] The fired product was crushed to obtain single-particle metal oxides doped with Al, Y, and Zr.

[0074] After dry-mixing Co(OH)2 and Al(OH)3 as coating raw material substances with the obtained single-particle metal oxides, a cathode active material with a coating layer formed was produced by heat-treating at 700 °C for 5 hours in an oxygen atmosphere. At this time, Co(OH)2 and Al(OH)3 were mixed based on the single-particle metal oxides with a content corresponding to 2.5 mol% of Co and a content corresponding to 1000 ppm of Al.

[0075] Example 2 Single-particle cathode active materials were produced in the same manner as in Example 1, except that firing (1 st step) was performed at 885 °C for 3 hours.

[0076] Example 3 Single-particle cathode active materials were produced in the same manner as in Example 1, except that firing (1 st step) was performed at 890 °C for 3 hours.

[0077] Example 4 Single-particle cathode active materials were produced in the same manner as in Example 1, except that firing (1 stA single-particle positive electrode active material was produced in the same manner as in Example 1, except that step) was performed.

[0078] Comparative Example 1 After pre-firing at 680°C for 6.5 hours to obtain pre-fired products, the obtained pre-fired products are placed in a firing furnace with an oxygen atmosphere, the temperature is increased, and they are fired at 900°C for 4 hours (1 st After step) then bake at 780°C for 11 hours (2 nd A single-particle positive electrode active material was produced in the same manner as in Example 1, except that the firing process was carried out using the method described in step 1.

[0079] Comparative Example 2 Bake at 910℃ for 4 hours (1 st A single-particle positive electrode active material was produced in the same manner as in Comparative Example 1, except that step 1 was performed.

[0080] The firing process conditions for the examples and comparative examples are summarized in Table 1 below.

[0081] [Table 1]

[0082] Experimental Example 1 - Measurement of Dn and Dv values The Dv and Dn values ​​were measured for the positive electrode active materials produced in Examples 1 to 4 and Comparative Examples 1 to 2 using the laser diffraction method. The results are shown in Tables 2 and 3 below.

[0083] Furthermore, Figure 1 shows a particle size graph based on the cumulative number distribution for the positive electrode active materials produced in Examples 1 to 4 and Comparative Examples 1 to 2.

[0084] [Table 2]

[0085] [Table 3]

[0086] Referring to Figure 1, Table 2, and Table 3, the positive electrode active materials produced in Examples 1 to 4 all have a particle size Dn10 of 1.1 μm or larger, which corresponds to 10% of the cumulative particle number distribution. However, in Comparative Examples 1 and 2, the particle size is 1.0 μm or smaller, indicating a high fine powder content.

[0087] Experimental Example 2: Manufacturing of coin cells and evaluation of high-temperature life retention rate (1) Manufacturing of coin cells Using the positive electrode active materials produced in the examples and comparative examples, CR2032 coin cells were manufactured by the following method.

[0088] Specifically, a cathode active material, a conductive material (acetylene black FX35, Denka Co., Ltd.), and a polyvinylidene fluoride binder (product name: KF9709) were mixed in a weight ratio of 96.5:1.5:295:2.2:2.8. This mixture was then added to an N-methyl-2-pyrrolidone solvent to produce a cathode active material slurry, with a solid content of approximately 65-69% by weight.

[0089] The slurry was coated onto an aluminum foil (20 μm thick), which served as the positive electrode current collector, using a doctor blade. After drying, the mixture was rolled to produce the positive electrode. The loading amount of the positive electrode was approximately 15-16 mg / cm³. 2 The rolling density is approximately 3.5 g / cm³. 3 That was the case.

[0090] A 2032 coin-type half-cell was manufactured using the aforementioned positive electrode, lithium metal negative electrode (400 μm thick, NEBA), electrolyte, and polypropylene polyethylene separator by a conventional method. The electrolyte was prepared by dissolving 1 M LiPF6 in a mixed solvent of ethylene carbonate, dimethyl carbonate, and diethyl carbonate (mixing ratio EC:DMC:DEC = 1:2:1 volume%) to produce a mixed solution, to which 2% by weight of vinylene carbonate (VC) was added.

[0091] (2) Measurement of capacitance retention rate and resistance increase rate The coin-type half-cells manufactured in (1) above were aged at room temperature (25°C) for 10 hours, and then a charge-discharge test was performed.

[0092] At 45°C, a formation cycle of constant current charge / discharge at 0.1C / 0.1C within a voltage of 2.5 to 4.25V was performed, followed by a constant current charge / discharge test at 0.5C / 1C. The capacity retention rate and DCIR increase rate were calculated at 50 cycles relative to the capacity of the first cycle.

[0093] DCIR = (V0 - V1 / )I 1 st , 50 th In each cycle, measurements are taken in the discharge disclosure step from the charged state. (V0: Voltage before current application, V1: Voltage after current application (10 seconds), I: Applied current) The results are shown in Table 4 below.

[0094] [Table 4]

[0095] Referring to Table 4, the positive electrode active materials of Examples 1 to 4, whose Dv10 / Dn10 and Dv10-Dn10 values ​​satisfy the range of the present invention, exhibit excellent performance, with a capacity retention rate of 93% or more and a resistance increase rate of 56.2% or less at high temperatures. In contrast, the positive electrode active materials of Comparative Examples 1 and 2, whose Dv10 / Dn10 and Dv10-Dn10 values ​​fall outside the range of the present invention, show deterioration in capacity retention rate and resistance increase rate at high temperatures compared to the examples.

[0096] The present invention is not limited to the embodiments described above and can be manufactured in a variety of different forms. Those with ordinary skill in the art to which the present invention pertains will understand that the invention can be implemented in other specific forms without altering the technical idea or essential features of the invention. Therefore, the embodiments described above should be understood to be illustrative and not limiting in all respects.

Claims

1. Single-particulate metal oxides containing 0.8 moles or more of nickel, based on 1 mole of total metal excluding lithium; and A coating layer containing cobalt, located on the surface of the metal oxide; Includes, The metal oxide on which the coating layer is formed has a particle size Dn10 of 1.1 μm or larger for particles that make up 10% of the cumulative distribution of particle numbers, and is a positive electrode active material for lithium secondary batteries.

2. The positive electrode active material for a lithium secondary battery according to claim 1, wherein the metal oxide on which the coating layer is formed has a particle size Dn10 of particles corresponding to 10% of the cumulative distribution of particle numbers in the range of 1.1 μm to 2.0 μm.

3. The metal oxide on which the coating layer is formed satisfies the following formula 1, wherein the positive electrode active material for a lithium secondary battery according to claim 1. [Formula 1] 1.1 ≤ Dv10 / Dn10 ≤ 2.2 (In Equation 1 above, Dv10 is the particle size distribution obtained from the volume of the metal oxide on which the coating layer is formed, and is the average particle size of the particles corresponding to the cumulative percentage of volume of 10%, while Dn10 is the average particle size of the particles at the point corresponding to 10% of the cumulative distribution of the number of particles when the metal oxide on which the coating layer is formed is accumulated from the smallest particles.)

4. The metal oxide on which the coating layer is formed satisfies the following formula 2, wherein the positive electrode active material for a lithium secondary battery according to claim 1. [Formula 2] 0.5μm≦Dv10-Dn10≦1.2μm (In Equation 2 above, Dv10 is the particle size distribution obtained from the volume of the metal oxide on which the coating layer is formed, and is the average particle size of the particles corresponding to the cumulative percentage of volume of 10%, while Dn10 is the average particle size of the particles at the point corresponding to 10% of the cumulative distribution of the number of particles when the metal oxide on which the coating layer is formed is accumulated from the smallest particles.)

5. The positive electrode active material for a lithium secondary battery according to claim 1, wherein the metal oxide on which the coating layer is formed has a particle size Dnmin of the particle corresponding to the minimum cumulative distribution of particle numbers of 1.0 μm or more.

6. The positive electrode active material for a lithium secondary battery according to claim 1, wherein the metal oxide on which the coating layer is formed has a particle size Dnmin of the particle corresponding to the minimum cumulative distribution of particle numbers in the range of 1.0 μm to 1.4 μm.

7. The positive electrode active material for a lithium secondary battery according to claim 1, wherein the average particle size Dv50 of the metal oxide on which the coating layer is formed is 5 μm or less.

8. The positive electrode active material for a lithium secondary battery according to claim 1, wherein the coating layer further comprises aluminum.

9. The positive electrode active material for a lithium secondary battery according to claim 1, wherein the cobalt content in the coating layer is in the range of 0.035 moles to 0.08 moles, based on the total amount of metal excluding lithium in the single-particulate metal oxide.

10. The aforementioned metal oxide further comprises cobalt and manganese, The positive electrode active material for a lithium secondary battery according to claim 1, wherein the cobalt content is 0.05 moles or less based on 1 mole of total metal excluding lithium.

11. The aforementioned metal oxide further contains a doping element, The positive electrode active material for a lithium secondary battery according to claim 10, wherein the doping element comprises at least one of Y, Al, Zr, Nb, Mo, W, Ti, Ce, Mg, B, P, V, Sr, and B.

12. A positive electrode for a lithium secondary battery, comprising the positive electrode active material described in any one of claims 1 to 11.

13. A lithium secondary battery comprising a positive electrode for a lithium secondary battery as described in claim 12.

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