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

Abstract

To provide a method for manufacturing a positive electrode active material including core particles in a single particle form effectively at relatively low sintering temperature without using an alkali-based growth promotor, and provide a positive electrode active material manufactured by the method, in which the structure is stable, impurities do not remain, the resistance does not increase, and the long life can be achieved.SOLUTION: A positive electrode active material includes core particles in a single particle form including layered lithium nickel composite oxide, and a coating layer existing on a surface of the core particles and containing cobalt and zirconium. The lithium nickel composite oxide of the core particle contains aluminum and zirconium. For 100 mol% of the entire metals excluding lithium, the nickel content is 60 mol% or more, the aluminum content is 0.8 mol% to 1.5 mol%, the zirconium content is 0.1 mol% to 0.3 mol%, and a ratio (Al / Zr) of the aluminum content to the zirconium content is 5 or more.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a positive electrode active material, a method for producing the same, a positive electrode, and a lithium secondary battery. [Background technology]

[0002] Lithium secondary batteries, which have high energy density yet are easy to carry, are widely used as power sources for mobile information terminals such as mobile phones, laptops, and smartphones. Recently, active research has been conducted into using high-energy-density lithium secondary batteries as power sources for hybrid and electric vehicles or as power storage sources.

[0003] To realize lithium secondary batteries that meet these requirements, various positive electrode active materials have been investigated, among which lithium nickel oxide, lithium nickel manganese cobalt composite oxide, lithium nickel cobalt aluminum composite oxide, and lithium cobalt oxide are mainly used as positive electrode active materials.

[0004] However, in recent years, the demand for larger size, higher capacity, higher energy density, and improved productivity of lithium secondary batteries has increased, necessitating the development of new methods for manufacturing positive electrode active materials. Summary of the Invention [Problem to be solved by the invention]

[0005] One embodiment of the present invention provides a method for effectively producing a cathode active material including core particles in a single particle form at a relatively low firing temperature without using an alkali-based grain growth accelerator, thereby reducing clumping between particles and providing an economical method with a simple overall manufacturing process. As a result, a cathode active material is provided that is structurally stable, does not contain residual impurities, does not increase resistance, and can achieve a long life. [Means for solving the problem]

[0006] In one embodiment of the present invention, there is provided a positive electrode active material comprising: a core particle in the form of a single particle, which includes a layered lithium-nickel composite oxide; and a coating layer located on the surface of the core particle and containing cobalt and zirconium, wherein the lithium-nickel composite oxide of the core particle contains aluminum and zirconium, and the nickel content is 60 mol % or more relative to 100 mol % of all metals excluding lithium, the aluminum content is 0.8 mol % to 1.5 mol %, and the zirconium content is 0.1 mol % to 0.3 mol %, and the ratio of the aluminum content to the zirconium content (Al / Zr) is 5 or more.

[0007] In another embodiment of the present invention, there is provided a method for producing a positive electrode active material, including the steps of: preparing a nickel-based composite hydroxide by performing a co-precipitation reaction by maintaining a mixture of a nickel precursor and a metal precursor at a pH of 11 to 12 for 30 hours or more; mixing the nickel-based composite hydroxide, anhydrous lithium hydroxide, an aluminum raw material, and a zirconium raw material, and performing a first heat treatment to obtain secondary particles comprising a layered lithium-nickel-based composite oxide and formed by agglomeration of a plurality of primary particles; pulverizing the secondary particles; and introducing the pulverized product, the cobalt-coating raw material, and the zirconium-coating raw material into an aqueous solvent, mixing them, and then performing a second heat treatment to obtain a positive electrode active material.

[0008] In yet another embodiment of the present invention, there is provided a positive electrode comprising a positive electrode current collector and a positive electrode active material layer located on the positive electrode current collector and including the above-described positive electrode active material.

[0009] In yet another embodiment of the present invention, there is provided a lithium secondary battery including the above-described positive electrode, negative electrode, and electrolyte. [Effects of the Invention]

[0010] The cathode active material according to one embodiment of the present invention can be synthesized by a simple method at a relatively low heat treatment temperature. Since the synthesis process does not use an alkaline grain growth promoter, no residue remains, resistance does not increase, and the cathode active material is structurally stable, thereby enabling the lithium secondary battery to have long life characteristics. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a cross-sectional view schematically illustrating a lithium secondary battery according to an embodiment. [Figure 2] 1 is a cross-sectional view schematically illustrating a lithium secondary battery according to an embodiment. [Figure 3] 1 is a cross-sectional view schematically illustrating a lithium secondary battery according to an embodiment. [Figure 4] 1 is a cross-sectional view schematically illustrating a lithium secondary battery according to an embodiment. [Figure 5] 1 shows the results of SEM-EDS analysis for component analysis of a coating layer located on the surface of the positive electrode active material prepared in Example 1. [Figure 6] 1 is a graph showing the life characteristics of the lithium secondary batteries produced in Example 1, Example 2 and Comparative Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0012] DETAILED DESCRIPTION OF THE INVENTION The following detailed description of the present invention is given by way of example only and is not intended to limit the scope of the present invention, which is defined solely by the claims.

[0013] Unless otherwise specified in this specification, when a layer, film, region, plate, or other part is said to be "on" another part, this includes not only the case where it is "directly on" the other part, but also the case where there is another part in between.

[0014] Unless otherwise stated herein, the singular can also include the plural. Furthermore, unless otherwise stated, "A or B" means "including A, including B, or including A and B."

[0015] As used herein, "combinations thereof" refers to mixtures, laminates, composites, copolymers, alloys, blends, reaction products, and the like of compositions.

[0016] Unless otherwise defined herein, particle size refers to the average particle size. Furthermore, particle size refers to the average particle size (D50), which refers to the diameter of particles with a cumulative volume of 50% in a particle size distribution. The average particle size (D50) can be measured by methods well known to those skilled in the art, such as using a particle size analyzer or a transmission electron microscope or scanning electron microscope image. Alternatively, the average particle size (D50) can be measured using a measuring device using dynamic light scattering, and data analysis can be performed to count the number of particles in each particle size range, after which the average particle size (D50) can be calculated. Alternatively, the average particle size (D50) can be measured using a laser diffraction method. More specifically, in measurements using the laser diffraction method, the particles to be measured are dispersed in a dispersion medium, then introduced into a commercially available laser diffraction particle size measuring device (e.g., MT3000 manufactured by Microtrac), and irradiated with ultrasonic waves of approximately 28 kHz at an output of 60 W, after which the average particle size (D50) based on 50% of the particle size distribution measured by the measuring device can be calculated.

[0017] It should be understood that the terms "comprise," "include," "comprise," or "have" are intended to specify the presence of embodied features, numbers, steps, components, or combinations thereof, but do not preclude the possible presence or addition of one or more other features, numbers, steps, components, or combinations thereof.

[0018] The term "metal" is understood to include general metals, transition metals, and metalloids (semimetals).

[0019] positive electrode active material In one embodiment, a positive electrode active material is provided, comprising: core particles in the form of single particles, the core particles including a layered lithium-nickel composite oxide; and a coating layer located on the surface of the core particles, the coating layer including cobalt and zirconium; wherein the lithium-nickel composite oxide of the core particles includes aluminum and zirconium, and the nickel content is 60 mol % or more relative to 100 mol % of all metals excluding lithium, the aluminum content is 0.8 mol % to 1.5 mol %, and the zirconium content is 0.1 mol % to 0.3 mol %, and the ratio of the aluminum content to the zirconium content (Al / Zr) is 5 or more.

[0020] High-nickel-based positive electrode active materials, with a nickel content of approximately 60 mol% or more, can achieve high energy density and have been actively developed in recent years. However, these high-nickel-based positive electrode active materials have limitations, including structural degradation during charge and discharge, surface side reactions with the electrolyte, and degradation due to particle cracking. Therefore, there is a need to develop positive electrode active materials that can achieve high energy density and long life characteristics.

[0021] High-nickel cathode active materials that achieve high capacity typically use secondary particles formed by the aggregation of multiple primary particles. However, recently, single particle structures have been considered to achieve longer life and reduce gas generation. However, increasing the firing temperature to produce single particles increases the clumping between particles, which can lead to reduced productivity.

[0022] Research has been proposed to add alkaline grain growth promoters during the synthesis of single particles to eliminate clumping and lower the firing temperature, but this has the problem of the residual grain growth promoter acting as resistance within the positive electrode after firing, shortening its lifespan.In addition, the need for a washing process to remove the residual grain growth promoter and residual salt increases manufacturing costs and complicates the process.

[0023] Therefore, in one embodiment, a positive electrode active material is provided that can be effectively synthesized even with a heat treatment at a relatively low temperature, is economical, is advantageous for mass production, has high structural stability, and can achieve excellent life characteristics.

[0024] The positive electrode active material can be synthesized by a heat treatment at a relatively low temperature and contains a layered lithium nickel composite oxide as a core particle in order to achieve excellent life characteristics.

[0025] For example, the lithium-nickel composite oxide of the core particle may be a high-nickel oxide having a nickel content of 60 mol% or more relative to 100 mol% of all metals excluding lithium. The nickel content of the layered lithium-nickel composite oxide may be, for example, 65 mol% or more, 70 mol% or more, 75 mol% or more, 80 mol% or more, 85 mol% or more, 90 mol% or more, 91 mol% or more, or 94 mol% or more, relative to 100 mol% of all metals excluding lithium, and may be 99 mol% or less, or 98 mol% or less.

[0026] In one embodiment, the lithium-nickel composite oxide of the core particle contains, in addition to nickel, specific amounts of aluminum and zirconium as dopants. The aluminum content may be 0.8 mol% to 1.5 mol%, for example, 0.8 mol% to 1.4 mol%, 0.8 mol% to 1.3 mol%, or 0.9 mol% to 1.2 mol%, based on 100 mol% of all metals excluding lithium. The zirconium content may be 0.1 mol% to 0.3 mol%, for example, 0.1 mol% to 0.2 mol%, based on 100 mol% of all metals excluding lithium.

[0027] For example, the ratio of aluminum to zirconium (Al / Zr) in the lithium nickel composite oxide of the core particle may be 5 or more, for example, 5 to 20, 5 to 15, or 5 to 10. Here, the ratio of aluminum to zirconium may be a molar ratio. When the ratio of aluminum to zirconium satisfies the above range, the composite oxide can be synthesized at a relatively low firing temperature without using an alkali-based grain growth additive, and high structural stability and long life characteristics can be achieved.

[0028] In one embodiment, the lithium nickel-based composite oxide is represented by the following Chemical Formula 1: [Chemical formula 1] Li a1 Ni x1 M 1 y1 Al z1 Zr w1 O 2-b1 X b1

[0029] In the above Chemical Formula 1, 0.9≦a1≦1.2, 0.6≦x1≦0.991, 0≦y1≦0.391, 0.008≦z1≦0.015, 0.001≦w1≦0.003, 0.9≦x1+y1+z1+w1≦1.1, and 0≦b1≦0.1; M 1 is one or more elements selected from B, Ba, Ca, Ce, Co, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sn, Sr, Ti, V, W, Y, and Zn, and X is one or more elements selected from F, P, and S.

[0030] In Chemical Formula 1, a1 may be 0.9≦a1≦1.1, 0.9≦a1≦1.05, or 0.9≦a1≦1. Also, x1 may be 0.7≦x1≦0.991 and 0≦y1≦0.291, or 0.8≦x1≦0.991 and 0≦y1≦0.191, or 0.9≦x1≦0.991 and 0≦y1≦0.091. z1, which indicates the Al content, may be, for example, 0.008≦z1≦0.014, 0.008≦z1≦0.013, or 0.009≦z1≦0.012. w1, which indicates the Zr content, may be, for example, 0.001≦w1≦0.002.

[0031] In Chemical Formula 1, 5≦z1 / w1 is satisfied, and may be, for example, 5≦z1 / w1≦20, 5≦z1 / w1≦15, or 5≦z1 / w1≦10.

[0032] A more specific example of the lithium nickel-based composite oxide is represented by the following chemical formula 2. [Chemical formula 2] Li a2 Ni x2 Co v2 M 2 y2 Al z2 Zr w2 O 2-b2 X b2

[0033] In the above chemical formula 2, 0.9≦a2≦1.2, 0.6≦x2<0.991, 0 <v2≦0.391、0≦y2≦0.391、0.008≦z2≦0.015、0.001≦w2≦0.003、0.9≦x2+v2+y2+z2+w2≦1.1、および0≦b2≦0.1であり、M 2 is one or more elements selected from B, Ba, Ca, Ce, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sn, Sr, Ti, V, W, Y, and Zn, and X is one or more elements selected from F, P, and S.

[0034] The formula 2 also satisfies 5≦z2 / w2, and may be, for example, 5≦z2 / w2≦20, 5≦z2 / w2≦15, or 5≦z2 / w2≦10.

[0035] The positive electrode active material has a core particle in the form of a single particle to ensure structural stability and long life. Here, a single particle refers to a particle that exists independently without grain boundaries and consists of a single particle. Morphologically, the particles may exist as an independent phase without aggregation, such as a monolith structure, a single structure, or a non-aggregated particle. For example, the single particle may be a single crystal. The single particles may exist independently or may be clustered together. For example, 2 to 9 single particles may be clustered together and in contact with each other.

[0036] In one embodiment, the single particles may be present singly or up to five single particles may be attached to each other.

[0037] As an example, the average particle diameter (D 50 ) is 1 μm to 4 μm, and may be, for example, 1.5 μm to 4 μm, 2 μm to 4 μm, or 2 μm to 3.8 μm. Single particles that satisfy this particle size range are structurally stable and can increase the energy density of the positive electrode, thereby improving the long-life characteristics of lithium secondary batteries. Here, the average particle size is determined by, for example, measuring the sizes (particle size, major axis, or length of the major axis) of 20 or so particles randomly selected from a scanning electron microscope image to obtain a particle size distribution, and then determining the size (D) of particles whose cumulative volume accounts for 50% by volume. 50 ) can be calculated.

[0038] The positive electrode active material includes a coating layer to improve the surface stability and ionic conductivity of the positive electrode active material and ensure excellent life characteristics.

[0039] The positive electrode active material includes a coating layer containing cobalt and zirconium located on the surface of the core particle, which improves the structural stability of the core particle and effectively suppresses side reactions with the electrolyte, thereby improving capacity characteristics and charge / discharge efficiency.

[0040] In one embodiment, the coating layer may be formed continuously on the core or in the form of discontinuous islands. For example, in the coating layer, one or more selected from cobalt (Co) and zirconium (Zr) may be present in the form of islands.

[0041] For example, the coating layer may further contain nickel, manganese, etc., which flow in from the core due to diffusion or other actions during the manufacturing process in addition to cobalt and zirconium, but the coating layer may contain cobalt and zirconium in the largest amounts and be a layer whose main components are these.

[0042] For example, the thickness of the coating layer may be 5 nm to 500 nm, e.g., 10 nm to 300 nm, or 50 nm to 200 nm. Within this range, the coating layer does not act as a resistor, does not reduce capacity, and can achieve the effect of improving life characteristics. Here, the thickness of the coating layer can be measured, for example, by SEM, TEM, TOF-SIMS, XPS, or EDS analysis, and for example, can be measured by EDS line profile analysis of a cross section of the positive electrode active material.

[0043] In one embodiment, the cobalt content of the coating layer is 0.5 mol% to 5 mol%, for example, 0.7 mol% to 4 mol%, 0.8 mol% to 3 mol%, or 1 mol% to 2 mol%, relative to 100 mol% of all metals in the positive electrode active material excluding lithium. By setting the cobalt content within this range, the coating layer does not act as a resistor, does not reduce capacity, and can effectively improve life characteristics.

[0044] For example, the zirconium content of the coating layer may be 0.1 mol% to 3 mol%, for example, 0.2 mol% to 2 mol%, or 0.3 mol% to 1 mol%, relative to 100 mol% of all metals in the positive electrode active material excluding lithium. By setting the content in this range, the coating layer does not act as a resistor, preventing a decrease in capacity and improving life characteristics.

[0045] In one embodiment, the coating layer has a cobalt content (W co ) to the zirconium content (W zr ) molar ratio (W zr / W co ) is 1.1 to 10, and may be, for example, 1.5 to 9, 2 to 8, or 5 to 7. Within this range, the effects of adding cobalt and zirconium to the coating layer can be balanced with each other.

[0046] Method for producing positive electrode active material In one embodiment, there is provided a method for producing a positive electrode active material, including: (i) a step of preparing a nickel-based composite hydroxide by carrying out a coprecipitation reaction in which a mixture of a nickel precursor and a metal precursor is maintained at a pH of 11 to 12 for 30 hours or more; (ii) a step of mixing the nickel-based composite hydroxide, anhydrous lithium hydroxide, an aluminum raw material, and a zirconium raw material and performing a first heat treatment to obtain secondary particles containing a layered lithium-nickel-based composite oxide and formed by agglomeration of a plurality of primary particles; (iii) a step of pulverizing the secondary particles; and (iv) a step of introducing the pulverized product, the cobalt-coating raw material, and the zirconium-coating raw material into an aqueous solvent, mixing them, and then performing a second heat treatment to obtain a positive electrode active material.

[0047] The manufacturing method relates to a method for manufacturing a positive electrode active material according to one embodiment, and according to the manufacturing method, a high-nickel positive electrode active material in a single particle form can be effectively manufactured at a relatively low firing temperature and by a simple method without adding an alkali-based grain growth promoter, thereby improving productivity and economy.

[0048] According to the above-described manufacturing method, when the nickel-based composite hydroxide and the lithium raw material are mixed and heat-treated, an aluminum raw material and a zirconium raw material may be added together and then calcined. It is understood that the aluminum raw material and the zirconium raw material simultaneously function as dopants and grain growth promoters. The addition of the aluminum raw material and the zirconium raw material promotes grain growth, enabling the effective synthesis of single particles at a lower temperature than conventional single particle synthesis methods. This also suppresses particle aggregation and improves productivity. Conventional alkaline grain growth promoters and fluxes have the problem of remaining after calcination, acting as resistance within the positive electrode and reducing its lifespan. However, according to one embodiment, the aluminum raw material and the zirconium raw material are used as dopants for the positive electrode active material, preventing them from remaining on the surface of the positive electrode active material particles, thereby improving lifespan characteristics.

[0049] The method for producing the positive electrode active material will be specifically described below.

[0050] The nickel-based composite hydroxide is a precursor of core particles in the positive electrode active material and can be synthesized by a co-precipitation reaction. In the co-precipitation reaction, the nickel precursor can be nickel hydroxide, oxide, nitrate, sulfate, carbonate, or a combination thereof. The metal precursor can be one or more selected from metal-containing hydroxides, oxides, nitrates, sulfates, and carbonates. Here, the metal of the metal precursor can be one or more elements selected from B, Ba, Ca, Ce, Co, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sn, Sr, Ti, V, W, Y, and Zn.

[0051] In one embodiment, in addition to the nickel precursor and the metal precursor, a complexing agent and a pH adjuster may be used in the co-precipitation reaction. The complexing agent adjusts the reaction rate of precipitate formation in the co-precipitation reaction and may include, for example, ammonium hydroxide (NH4OH), citric acid, or a combination thereof. The concentration of the complexing agent may be 0.1 to 1.5 M, for example, 0.1 to 1.4 M, or 0.5 to 1.4 M. The pH adjuster controls the pH of the reaction mixture and may include, for example, sodium hydroxide (NaOH), sodium carbonate (Na2CO3), sodium oxalate (Na2CO4), or a combination thereof.

[0052] The coprecipitation reaction is carried out by maintaining a pH of 11 to 12 for 30 hours or more. When this condition is met, the nickel-based composite hydroxide obtained by the coprecipitation reaction can have a dense morphology. In one embodiment, the coprecipitation reaction can be carried out in one step by maintaining the pH range for 30 hours or more. For example, the coprecipitation reaction can be carried out at a pH of 11.5 to 12, 11.6 to 11.9, or 11.7 to 11.8, for 30 to 50 hours, 32 to 45 hours, or 35 to 40 hours.

[0053] The nickel-based composite hydroxide is represented by, for example, the following chemical formula 11. [Chemical formula 11] Ni x11 M 1 y11 (OH)2

[0054] In the formula 11, 0.6≦x11≦1, 0≦y11≦0.4, and 0.9≦x11+y11≦1.1; M 1 is one or more elements selected from B, Ba, Ca, Ce, Co, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sn, Sr, Ti, V, W, Y, and Zn.

[0055] In Chemical Formula 11, 0.7 ≦ x11 ≦ 1, 0 ≦ y11 ≦ 0.3, or 0.8 ≦ x11 ≦ 1, 0 ≦ y11 ≦ 0.2, or 0.9 ≦ x11 < 1, 0 < y11 ≦ 0.1 may hold.

[0056] The nickel-based composite hydroxide is specifically represented by the following Chemical Formula 12 as an example. [Chemical Formula 12] Ni x12 Co v12 M 2 y12 (OH)2 In Chemical Formula 12, 0.6 ≦ x12 < 1, 0 < v12 ≦ 0.4, 0 ≦ y12 ≦ 0.4, and 0.9 ≦ x12 + v12 + y12 ≦ 1.1, and M 2 is one or more elements selected from B, Ba, Ca, Ce, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sn, Sr, Ti, V, W, Y, and Zn.

[0057] The nickel-based composite hydroxide is in a particulate form and can have a dense structure. When this is satisfied, core particles in a single-particle form with excellent structural stability can be effectively obtained. As an example, the average particle diameter (D 50 ) of the nickel-based composite hydroxide is 10 μm to 20 μm, and can be, for example, 10 μm to 18 μm, or 12 μm to 16 μm. Here, the average particle diameter (D 50 ) can be measured through a SEM image. The nickel-based composite hydroxide is large-particle, and can be, for example, a large-particle precursor.

[0058] The nickel-based composite hydroxide can be, for example, non-crystalline, which can be confirmed by X-ray diffraction analysis.

[0059] Next, (ii) the nickel-based composite hydroxide, anhydrous lithium hydroxide, an aluminum raw material, and a zirconium raw material are mixed and subjected to a first heat treatment. Thereby, a layered lithium nickel-based composite oxide is included, and secondary particles formed by aggregation of a plurality of primary particles are produced.

[0060] For example, in step (ii), the lithium content of the anhydrous lithium hydroxide is 0.9 to 1.2 molar parts, for example, 0.9 to 1.1 molar parts, or 0.9 to 1.05 molar parts, relative to 1 molar part of the total of all the metals in the nickel-based composite hydroxide, the aluminum in the aluminum raw material, and the zirconium in the zirconium raw material, and for example, more than 1 molar part but less than 1.1 molar parts, for example, 1.01 to 1.04 molar parts. By appropriately adjusting the molar ratio of the lithium raw material, core particles in the form of single particles having a stable structure and good quality can be effectively produced.

[0061] In the step (ii), anhydrous lithium hydroxide is used as the lithium raw material. By using anhydrous lithium hydroxide as the lithium raw material, the charging amount can be increased, which contributes to improving the production amount per hour.

[0062] The anhydrous lithium hydroxide (LiOH) may have an average particle size (D 50 After drying, lithium hydroxide hydrate (LiOH·HO) with an average particle size (D 50 The anhydrous lithium hydroxide can be produced by pulverizing the powder once after drying, without pulverizing it before drying. The drying can be carried out, for example, under vacuum conditions at a temperature of 50°C to 200°C for 0.5 to 20 hours.

[0063] According to this method for producing anhydrous lithium hydroxide, the process for obtaining anhydrous lithium salt is simple, optimal process conditions can be maintained, the conversion rate to Li2CO3 is low (5% or less), and high-purity anhydrous lithium hydroxide can be obtained. After anhydrous lithium hydroxide is pulverized, the powder's fluidity rapidly decreases, making additional processing after pulverization generally very difficult. For example, when the pulverized material is dried, the heat generated during drying causes fine particles to entangle and form tight agglomerates, necessitating an additional pulverization step. However, the pulverization step increases the particle agglomeration strength, making pulverization difficult. Furthermore, as the number of steps increases, the conversion rate to Li2CO3 increases due to the increase in specific surface area, making it difficult to obtain high-quality anhydrous lithium hydroxide. According to one embodiment of the method for producing anhydrous lithium hydroxide, anhydrous lithium hydroxide is dried under specific conditions and then pulverized once to a specific size, resulting in a simple process and high-quality anhydrous lithium hydroxide. Furthermore, additional processing steps can be easily performed after pulverization.

[0064] In one embodiment, when anhydrous lithium hydroxide is used as the lithium source instead of lithium hydroxide hydrate, the amount of unnecessary gas and moisture generated during heat treatment can be reduced, improving processability and the quality of the cathode active material. In addition, the input of unnecessary heavy materials such as HO can be eliminated, increasing the heat treatment yield and improving productivity.

[0065] The average particle size (D 50 ) is, for example, about 450 μm to 550 μm, 480 μm to 500 μm, and the average particle size (D 50 ) may be about 3 μm to 25 μm or about 5 μm to 20 μm.

[0066] In one embodiment, the aluminum content of the aluminum raw material is 0.8 mol% to 1.5 mol%, for example, 0.8 mol% to 1.4 mol%, 0.8 mol% to 1.3 mol%, or 0.9 mol% to 1.2 mol%, relative to a total of 100 mol% of all metals in the nickel-based composite hydroxide, aluminum in the aluminum raw material, and zirconium in the zirconium raw material.

[0067] For example, the zirconium content of the zirconium raw material may be 0.1 mol % to 0.3 mol %, for example, 0.1 mol % to 0.2 mol %, relative to a total of 100 mol % of all metals in the nickel-based composite hydroxide, aluminum in the aluminum raw material, and zirconium in the zirconium raw material.

[0068] In one embodiment, the ratio of the aluminum content to the zirconium content (Al / Zr) may be 5 or greater, for example, 5-20, 5-15, or 5-10.

[0069] The aluminum raw material and the zirconium raw material described above are understood to function as dopant raw materials and also as grain growth promoters, and by adding each of them in the above content ranges, optimal single particles can be obtained in the form of core particles.

[0070] The aluminum raw material may be, for example, aluminum oxide, such as Al2O3, and the zirconium raw material may be, for example, zirconium oxide, specifically ZrO2.

[0071] According to an embodiment of the present invention, a method for manufacturing a cathode active material can perform a heat treatment (i.e., a first heat treatment) at a lower temperature than conventional single particle synthesis methods. That is, even when heat treatment is performed at a relatively low temperature, a desired single particle shape with good morphology can be obtained as the core particle of the cathode active material. This simplifies the process, improves economy, and reduces particle aggregation problems, thereby improving productivity and processability.

[0072] For example, the first heat treatment may be performed in an oxidizing gas atmosphere, and the oxidizing gas may be air or oxygen. For example, the first heat treatment may be performed in an air atmosphere or an atmosphere containing 50% or more by volume of oxygen, for example, 60% or more by volume, 80% or more by volume, or 90% or more by volume of oxygen.

[0073] In one embodiment, the first heat treatment may be performed at a temperature of 900° C. or less, or 890° C. or less, or 850° C. or less, or 810° C. or less, for example, 700° C. to 900° C., 710° C. to 890° C., 730° C. to 850° C., or 750° C. to 810° C. The first heat treatment may be performed for, for example, 4 hours to 20 hours, 5 hours to 15 hours, 6 hours to 12 hours, or 8 hours to 10 hours.

[0074] In one embodiment, a method for manufacturing a positive electrode active material may be performed without adding an alkali-based grain growth promoter or flux during the process of mixing a nickel-based composite hydroxide, a lithium raw material, an aluminum raw material, and a zirconium raw material and heat-treating the mixture, thereby preventing an increase in resistance due to residue after heat-treatment, improving the life characteristics of a lithium secondary battery, and eliminating the need for an additional process for removing the residue, thereby improving processability and economy.

[0075] The first heat treatment can produce secondary particles containing a layered lithium nickel composite oxide and consisting of a plurality of agglomerated primary particles. At this time, the primary particles constituting the secondary particles have sufficiently grown into single crystals due to the addition of the aluminum raw material and the zirconium raw material, and the secondary particles have a dense structure, so that core particles with excellent structural stability can be effectively obtained.

[0076] In one embodiment, the secondary particles may be large particles. By using such large particle precursors in the process described below, the cake produced during the manufacturing process has low hardness and is easy to crush, thereby improving productivity per hour.

[0077] As an example, the average particle size of the secondary particles (D 50 The average particle size of the secondary particles (D) is 10 μm to 20 μm, for example, 10 μm to 18 μm, or 12 μm to 16 μm. 50 ) can be measured through SEM images.

[0078] The average particle size of the primary particles constituting the secondary particles (D 50 The average particle size (D) of the primary particles is 1 μm to 4 μm, for example, 1.5 μm to 4 μm, 2 μm to 4 μm, or 2 μm to 3.5 μm. 50 ) may be measured through an SEM image of the surface of the secondary particle. The secondary particle may be composed of a plurality of primary particles and pores formed between the primary particles, and may have a dense structure rather than a hollow structure.

[0079] The obtained layered lithium nickel-based composite oxide is represented by Chemical Formula 1, which has been described above.

[0080] Next, (iii) the obtained secondary particles are pulverized. Pulverizing the secondary particles in step (iii) means breaking the secondary particles, and is understood to be a process in which the primary particles that made up the secondary particles are separated from each other to become individual single particles. Through the pulverization process, core particles of the positive electrode active material in the form of single particles can be obtained.

[0081] According to the above manufacturing method, when the nickel-based composite hydroxide and the lithium raw material are mixed and heat-treated, the aluminum raw material and the zirconium raw material are added together and heat-treated, so that the primary particles can be broken down into single particles of a sufficient size at a relatively low temperature of 900°C or less, and secondary particles in which such primary particles are aggregated can be obtained, and by pulverizing these, the desired single particle form can be made into core particles of the positive electrode active material.

[0082] The pulverization can be carried out using a jet mill or an air classifier mill (ACM). When pulverization is carried out using a jet mill, the air pressure is adjusted so that the volume density of the pulverized product is 0.2 g / cm. 3 ~0.5g / cm 3 The pressure can be appropriately adjusted to about 2 to 8 bar, or 4 to 6 bar, for example. The grinding step can be carried out for, for example, 10 to 120 minutes, for example, 10 to 80 minutes, 10 to 60 minutes, or 20 to 50 minutes.

[0083] Then, (iv) the milled product, the cobalt-coating raw material, and the zirconium-coating raw material are mixed in an aqueous solvent and then subjected to a second heat treatment to obtain a cathode active material. For example, the cobalt-coating raw material may be a hydroxide, oxide, sulfate, nitrate, carbonate, or a combination thereof containing cobalt. For example, the zirconium-coating raw material may be a hydroxide, oxide, sulfate, nitrate, carbonate, or a combination thereof containing zirconium.

[0084] For example, the aqueous solvent may be a commonly used one, such as water, distilled water, an alcohol-based solvent, or a combination thereof.

[0085] In one embodiment, the method may further include drying the milled product, the cobalt-coated raw material, and the zirconium-coated raw material before the second heat treatment, after mixing them together. For example, the drying before the second heat treatment may be performed at 80°C to 300°C, 90°C to 250°C, 100°C to 200°C, 150°C to 200°C, or 180°C to 200°C.

[0086] For example, the second heat treatment may be performed in an oxidizing gas atmosphere, and the oxidizing gas may be air or oxygen. For example, the second heat treatment may be performed in an air atmosphere or an atmosphere containing 50% or more by volume of oxygen.

[0087] In one embodiment, the second heat treatment may be performed at 500°C to 900°C, 600°C to 800°C, or 650°C to 750°C. The second heat treatment may be performed in an oxidizing gas atmosphere for, for example, 8 hours to 20 hours, 10 hours to 18 hours, or 12 hours to 16 hours. When this condition is satisfied, a positive electrode active material having excellent surface stability and improved life characteristics may be effectively produced.

[0088] In one embodiment, the method for manufacturing a cathode active material includes adjusting the cobalt content of the cobalt coating raw material to 0.5 mol% to 5 mol%, for example, 0.7 mol% to 4 mol%, 0.8 mol% to 3 mol%, or 1 mol% to 2 mol%, based on 100 mol% of all metals excluding lithium in the final cathode active material. By adjusting the cobalt content within this range, the coating layer does not act as a resistor, thereby preventing a decrease in capacity and effectively improving life characteristics.

[0089] In one embodiment, the method for manufacturing a cathode active material includes adjusting the zirconium content of the zirconium coating raw material to 0.1 mol% to 3 mol%, for example, 0.2 mol% to 2 mol%, or 0.3 mol% to 1 mol%, based on 100 mol% of all metals excluding lithium in the final cathode active material. By adjusting the zirconium content within this range, the coating layer does not act as a resistor, thereby improving the lifespan without reducing capacity.

[0090] Lithium secondary battery In one embodiment, there is provided a lithium secondary battery comprising: a positive electrode; a negative electrode; and an electrolyte; wherein the positive electrode comprises: a positive electrode current collector; and a positive electrode active material layer located on the positive electrode current collector and including the positive electrode active material produced by the above-described production method.

[0091] For example, a lithium secondary battery may include a positive electrode, a negative electrode, a separator positioned between the positive electrode and the negative electrode, and an electrolyte.

[0092] Lithium secondary batteries can be classified into cylindrical, prismatic, pouch, and coin types depending on their shape. FIGS. 1 to 4 are schematic diagrams showing a lithium secondary battery according to an embodiment, where FIG. 1 shows a circular battery, FIG. 2 shows a prismatic battery, and FIGS. 3 and 4 show pouch-type battery configurations. Referring to FIGS. 1 to 4, a lithium secondary battery 100 may include an electrode assembly 40 having a positive electrode 10 and a negative electrode 20 with a separator 30 interposed therebetween, and a case 50 in which the electrode assembly 40 is housed. The positive electrode 10, the negative electrode 20, and the separator 30 may be impregnated with an electrolyte (not shown). As shown in FIG. 1, the lithium secondary battery 100 may include a sealing member 60 that seals the case 50. Also, in FIG. 2, the lithium secondary battery 100 may include a positive electrode lead tab 11, a positive electrode terminal 12, a negative electrode lead tab 21, and a negative electrode terminal 22. As shown in FIGS. 3 and 4, the lithium secondary battery 100 may include electrode tabs 70, i.e., a positive electrode tab 71 and a negative electrode tab 72, which serve as electrical paths for conducting current generated in the electrode assembly 40 to the outside.

[0093] positive electrode The positive electrode includes a positive electrode current collector and a positive electrode active material layer disposed on the positive electrode current collector. The positive electrode active material layer may optionally further include a binder, a conductive material, or a combination thereof.

[0094] positive electrode active material The positive electrode active material may be a compound capable of reversible intercalation / deintercalation of lithium (lithiated insertion compound), as described above in relation to the method for manufacturing the positive electrode active material.

[0095] binder The binder serves to firmly adhere the positive electrode active material particles to each other and to firmly adhere the positive electrode active material to the current collector. Representative examples of binders include, but are not limited to, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, epoxy resin, (meth)acrylic resin, polyester resin, and nylon.

[0096] Conductive material The conductive material is used to impart electrical conductivity to the electrode, and any material that is electron-conductive and does not cause chemical changes in the battery that is constructed can be used. Examples of conductive materials include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, carbon fiber, carbon nanofiber, and carbon nanotube; metal-based materials in the form of metal powder or metal fiber containing copper, nickel, aluminum, silver, etc.; conductive polymers such as polyphenylene derivatives; and mixtures thereof.

[0097] The content of the binder and the conductive material may be 0.5% by weight to 5% by weight, respectively, relative to 100% by weight of the positive electrode active material layer.

[0098] The positive electrode current collector may be made of Al, but is not limited to this.

[0099] negative electrode The negative electrode may include a negative electrode current collector; and a negative electrode active material layer located on the negative electrode current collector. The negative electrode active material layer includes a negative electrode active material, and may further include a binder, a conductive material, or a combination thereof.

[0100] negative electrode active material The negative electrode active material includes a material capable of reversibly inserting / desorbing lithium ions, lithium metal, an alloy of lithium metal, a material capable of doping and undoping lithium, or a transition metal oxide.

[0101] Examples of the material capable of reversibly inserting / desorbing the lithium ions include carbon-based negative electrode active materials, which can include, for example, crystalline carbon, amorphous carbon, or a combination thereof. Examples of the crystalline carbon include graphite such as amorphous, plate-like, flaky, spherical, or fibrous natural graphite or artificial graphite, and examples of the amorphous carbon include soft carbon or hard carbon, mesophase pitch carbide, calcined coke, and the like.

[0102] As the alloy of the lithium metal, an alloy of lithium and a metal selected from Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, and Sn can be used.

[0103] As the material capable of doping and undoping lithium, an Si-based negative electrode active material or an Sn-based negative electrode active material can be used. The Si-based negative electrode active material can be silicon, a silicon-carbon composite, SiOx (0 < x < 2), an Si-Q alloy (where Q is an element selected from alkali metals, alkaline earth metals, group 13 elements, group 14 elements (excluding Si), group 15 elements, group 16 elements, transition metals, rare earth elements, and combinations thereof, for example, Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Tc, Re, Bh, Fe, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Tl, Ge, P, As, Sb, Bi, S, Se, Te, Po, and combinations thereof), or a combination thereof. The Sn-based negative electrode active material can be Sn, SnO2, an Sn alloy, or a combination thereof.

[0104] The silicon-carbon composite may be a composite of silicon and amorphous carbon. 50 ) may be, for example, 0.5 μm to 20 μm. According to one embodiment, the silicon-carbon composite may be in the form of silicon particles, and the surfaces of the silicon particles may be coated with amorphous carbon. For example, it may include secondary particles (cores) formed by granulating primary silicon particles, and an amorphous carbon coating layer (shell) located on the surfaces of the secondary particles. The amorphous carbon may also be located between the primary silicon particles, for example, the primary silicon particles may be coated with amorphous carbon. The secondary particles may be dispersed in an amorphous carbon matrix.

[0105] The silicon-carbon composite may further include crystalline carbon. For example, the silicon-carbon composite may include a core including crystalline carbon and silicon particles, and an amorphous carbon coating layer located on the core surface. The crystalline carbon may be artificial graphite, natural graphite, or a combination thereof. Examples of the amorphous carbon include soft carbon, hard carbon, mesophase pitch carbide, and calcined coke.

[0106] When the silicon-carbon composite contains silicon and amorphous carbon, the silicon content may be 10 to 50% by weight and the amorphous carbon content may be 50 to 90% by weight, based on 100% by weight of the silicon-carbon composite.Alternatively, when the composite contains silicon, amorphous carbon, and crystalline carbon, the silicon content may be 10 to 50% by weight, the crystalline carbon content may be 10 to 70% by weight, and the amorphous carbon content may be 20 to 40% by weight, based on 100% by weight of the silicon-carbon composite.

[0107] The thickness of the amorphous carbon coating layer may be 5 nm to 100 nm. 50) can be 10 nm to 1 μm, or 10 nm to 200 nm. The silicon particles may exist alone as silicon, or in the form of a silicon alloy, or in an oxidized form. The oxidized form of silicon can be represented by SiO x (0 < x < 2). At this time, the atomic content ratio of Si:O indicating the degree of oxidation can be 99:1 to 33:67. In this specification, unless otherwise defined, the average particle size (D 50 ) means the diameter of the particle with a cumulative volume of 50% by volume in the particle size distribution.

[0108] The Si-based negative electrode active material or the Sn-based negative electrode active material can be used by mixing with a carbon-based negative electrode active material. When the Si-based negative electrode active material or the Sn-based negative electrode active material and the carbon-based negative electrode active material are used in combination, the mixing ratio can be 1:99 to 90:10 by weight.

[0109] Binder The binder serves to make the negative electrode active material particles adhere well to each other and also make the negative electrode active material adhere well to the current collector. As the binder, a non-aqueous binder, an aqueous binder, a dry binder or a combination thereof can be used.

[0110] Examples of the non-aqueous binder include polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene-propylene copolymer, polystyrene, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamideimide, polyimide or a combination thereof.

[0111] The water-based binder may be selected from styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, (meth)acrylonitrile-butadiene rubber, (meth)acrylic rubber, butyl rubber, fluororubber, polyethylene oxide, polyvinylpyrrolidone, polyepichlorohydrin, polyphosphazene, poly(meth)acrylonitrile, ethylene propylene diene copolymer, polyvinylpyridine, chlorosulfonated polyethylene, latex, polyester resin, (meth)acrylic resin, phenolic resin, epoxy resin, polyvinyl alcohol, and combinations thereof.

[0112] When an aqueous binder is used as the negative electrode binder, a cellulose-based compound that can impart viscosity may be further included. The cellulose-based compound may be a mixture of one or more of carboxymethyl cellulose, hydroxypropyl methyl cellulose, methyl cellulose, or alkali metal salts thereof. The alkali metal may be sodium, potassium, or lithium.

[0113] The dry binder can be a fiberizable polymeric material such as polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyethylene oxide, or a combination thereof.

[0114] Conductive material The conductive material is used to impart conductivity to the electrode and can be any material that is electron-conductive and does not cause chemical changes in the battery. Specific examples include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, carbon fiber, carbon nanofiber, and carbon nanotube; metal-based materials in the form of metal powder or metal fiber, including copper, nickel, aluminum, and silver; conductive polymers such as polyphenylene derivatives; and mixtures thereof.

[0115] The content of the negative electrode active material may be 95% to 99.5% by weight, and the content of the binder may be 0.5% to 5% by weight, relative to 100% by weight of the negative electrode active material layer. For example, the negative electrode active material layer may contain 90% to 99% by weight of the negative electrode active material, 0.5% to 5% by weight of the binder, and 0.5% to 5% by weight of the conductive material.

[0116] The negative electrode current collector may include, for example, indium (In), copper (Cu), magnesium (Mg), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), aluminum (Al), germanium (Ge), lithium (Li), or an alloy thereof, and may be in the form of a foil, sheet, or foam. The thickness of the negative electrode current collector may be, for example, 1 μm to 20 μm, 5 μm to 15 μm, or 7 μm to 10 μm.

[0117] electrolyte The electrolyte for a lithium secondary battery can be, for example, an electrolytic solution, which can include a non-aqueous organic solvent and a lithium salt.

[0118] The non-aqueous organic solvent serves as a medium through which ions involved in the electrochemical reactions of the battery can migrate, and can be a carbonate-based, ester-based, ether-based, ketone-based, or alcohol-based solvent, an aprotic solvent, or a combination thereof.

[0119] Examples of carbonate solvents that can be used include dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), methyl ethyl carbonate (MEC), ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), etc. Examples of ester solvents that can be used include methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methyl propionate, ethyl propionate, decanolide, mevalonolactone, valerolactone, caprolactone, etc. Examples of ether solvents that can be used include dibutyl ether, tetraglyme, diglyme, dimethoxyethane, 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, and tetrahydrofuran. Examples of ketone solvents that can be used include cyclohexanone. Examples of alcohol solvents that can be used include ethyl alcohol and isopropyl alcohol. Examples of aprotic solvents that can be used include nitriles such as R-CN (where R is a linear, branched, or cyclic hydrocarbon group having 2 to 20 carbon atoms, which may contain a double bond, an aromatic ring, or an ether group); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane and 1,4-dioxolane; and sulfolanes.

[0120] The non-aqueous organic solvent may be used alone or in combination of two or more kinds. When a mixture of two or more kinds is used, the mixing ratio may be appropriately adjusted depending on the desired battery performance, which is widely understood by those skilled in the art.

[0121] When a carbonate-based solvent is used, a cyclic carbonate and a chain carbonate can be mixed and used, and the cyclic carbonate and the chain carbonate can be mixed in a volume ratio of 1:1 to 1:9.

[0122] The non-aqueous organic solvent may further include an aromatic hydrocarbon organic solvent. For example, a carbonate solvent and an aromatic hydrocarbon organic solvent may be mixed in a volume ratio of 1:1 to 30:1.

[0123] The electrolyte may further contain vinyl ethyl carbonate, vinylene carbonate or ethylene carbonate based compounds to improve the battery life.

[0124] Representative examples of the ethylene carbonate compounds include fluoroethylene carbonate, difluoroethylene carbonate, chloroethylene carbonate, dichloroethylene carbonate, bromoethylene carbonate, dibromoethylene carbonate, nitroethylene carbonate, and cyanoethylene carbonate.

[0125] Lithium salts are substances that dissolve in organic solvents and act as a source of lithium ions within the battery, enabling basic lithium secondary battery operation and facilitating the movement of lithium ions between the positive and negative electrodes. Representative examples of lithium salts include LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiAlO2, LiAlCl4, LiPO2F2, LiCl, LiI, LiN(SO3C2F5)2, Li(FSO2)2N (lithium bis(fluorosulfonyl)imide; LiFSI), LiC4F9SO3, and LiN(C x F 2x+1 SO2)(C y F 2y+1 SO2) (x and y are integers of 1 to 20), lithium trifluoromethanesulfonate, lithium tetrafluoroethanesulfonate, lithium difluorobis(oxalate)phosphate (LiDFBOP), and lithium bis(oxalate)borate (LiBOB).

[0126] The concentration of the lithium salt is preferably within the range of 0.1 M to 2.0 M. When the concentration of the lithium salt is within the above range, the electrolyte has appropriate ionic conductivity and viscosity, thereby exhibiting excellent performance and allowing lithium ions to migrate effectively.

[0127] Separator Depending on the type of lithium secondary battery, a separator may be present between the positive and negative electrodes. Such separators may be made of polyethylene, polypropylene, polyvinylidene fluoride, or multilayer films of two or more of these. Of course, 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.

[0128] The separator may include a porous substrate and a coating layer including an organic material, an inorganic material, or a combination thereof located on one or both sides of the porous substrate.

[0129] The porous substrate may be a polymer membrane formed of any one polymer selected from polyolefins such as polyethylene and polypropylene, polyesters such as polyethylene terephthalate and polybutylene terephthalate, polyacetal, polyamide, polyimide, polycarbonate, polyether ketone, polyaryl ether ketone, polyetherimide, polyamide imide, polybenzimidazole, polyethersulfone, polyphenylene oxide, cyclic olefin copolymer, polyphenylene sulfide, polyethylene naphthalate, glass fiber, Teflon (registered trademark), and polytetrafluoroethylene, or a copolymer or mixture of two or more of these polymers.

[0130] The porous substrate can have a thickness of about 1 μm to 40 μm, for example, 1 μm to 30 μm, 1 μm to 20 μm, 5 μm to 15 μm, or 10 μm to 15 μm.

[0131] The organic material may include a (meth)acrylic copolymer including a first structural unit derived from (meth)acrylamide and a second structural unit including at least one of a structural unit derived from (meth)acrylic acid or a (meth)acrylate and a structural unit derived from (meth)acrylamidosulfonic acid or a salt thereof.

[0132] The inorganic material may include, but is not limited to, inorganic particles selected from Al2O3, SiO2, TiO2, SnO2, CeO2, MgO, NiO, CaO, GaO, ZnO, ZrO2, Y2O3, SrTiO3, BaTiO3, Mg(OH)2, boehmite, and combinations thereof. The average particle size (D 50 ) is 1 nm to 2000 nm, and can be, for example, 100 nm to 1000 nm, or 100 nm to 700 nm.

[0133] The organic material and the inorganic material may be mixed in one coating layer, or may be stacked in a coating layer containing an organic material and a coating layer containing an inorganic material.

[0134] The thickness of each of the coating layers may be 0.5 μm to 20 μm, for example, 1 μm to 10 μm, or 1 μm to 5 μm.

[0135] Examples of the present invention and comparative examples are described below. The following examples are merely illustrative of the present invention, and the present invention is not limited to the following examples.

[0136] Example 1 1. Production of positive electrode active material (1) Production of nickel-based composite hydroxide Nickel-based composite hydroxide was produced by the following coprecipitation method. A metal raw material mixed solution was prepared by dissolving nickel sulfate, cobalt sulfate, and manganese sulfate in distilled water as a solvent so that the molar ratio of Ni:Co:Mn was 95:4:1. A diluted solution of ammonia water (NH4OH) was prepared as a complexing agent, and sodium hydroxide (NaOH) was prepared as a pH adjuster. The concentration of the ammonia water was 10 wt%, and the concentration of the sodium hydroxide was 20 wt%. The prepared metal raw material mixed solution, ammonia water, and sodium hydroxide were each placed into a reactor.

[0137] The pH inside the reactor was adjusted to 11.75 and the mixture was stirred for 37 hours to synthesize a nickel-based composite hydroxide.

[0138] The slurry solution in the reactor was filtered, washed with high-purity distilled water, and then dried in a hot air oven at 180°C for 24 hours to obtain nickel-based composite hydroxide (Ni 0.95 Co 0.04 Mn 0.01 The obtained nickel-based composite hydroxide was in the form of secondary particles formed by the aggregation of multiple primary particles, and the average particle size of the secondary particles (D 50 ) was approximately 15 μm.

[0139] (2) Manufacturing of positive electrode active material The prepared nickel-based composite hydroxide was mixed with anhydrous lithium hydroxide, Al2O3, and ZrO2. At this time, the anhydrous lithium salt was mixed so that the molar ratio of lithium to all metals in the nickel-based composite hydroxide was 1.05. Furthermore, Al2O3 was mixed so that Al was 1 mol%, and ZrO2 was mixed so that Zr was 0.1 mol%, out of a total of 100 mol% of all metals in the nickel-based composite hydroxide, Al in Al2O3, and Zr in ZrO2.

[0140] The mixture was subjected to a first heat treatment at 810°C for 8 hours in an atmosphere containing 90% by volume of oxygen. 1.00 Ni 0.939 Co 0.04 Mn 0.01 Al 0.01Zr 0.001 O2, and is observed in the form of secondary particles when observed through an SEM image. The average particle size of the secondary particles measured through an SEM image (D 50 ) is about 15 μm, and the average particle size of the primary particles that make up the secondary particles (D 50 ) was approximately 3 μm.

[0141] The material obtained by the first heat treatment was pulverized for 20 minutes in a jet mill at an air pressure of about 5 bar, and the pulverized product was observed through an SEM image to be single particles with an average particle size of about 3 μm.

[0142] The milled product was washed in a distilled water solvent, and then Co(OH)2 and Zr(OH)2 were added and mixed to form a cobalt and zirconium coating. The distilled water was then removed, and the product was dried at 190°C. The product was then subjected to a second heat treatment at 710°C for 12 hours in an atmosphere containing 50% by volume of oxygen to form single particles. This resulted in a positive electrode active material with a 50-nm-thick coating layer containing Co and Zr on the single particle core. The cobalt content of the coating layer was designed to be 2 mol% based on 100% by weight of the total metals (excluding lithium) in the final positive electrode active material, and the Zr content of the coating layer was designed to be 0.3 mol% based on 100% by weight of the total metals (excluding lithium) in the final positive electrode active material.

[0143] 2. Lithium secondary battery manufacturing 98.5 wt% of the prepared positive electrode active material, 1.0 wt% of polyvinylidene fluoride binder, and 0.5 wt% of carbon nanotube conductive material were mixed to prepare a positive electrode active material layer slurry, which was then coated on an aluminum foil current collector, dried, and rolled to prepare a positive electrode. The prepared positive electrode contained the positive electrode active material in the form of pulverized single particles.

[0144] A structure was prepared using the positive electrode and the negative lithium counter electrode via a polytetrafluoroethylene separator, and inserted into a battery case. An electrolyte solution prepared by dissolving 1M LiPF6 in a solvent mixed with ethylene carbonate and dimethyl carbonate in a volume ratio of 3:7 was then injected to prepare a half-cell lithium secondary battery in a conventional manner.

[0145] Example 2 A cathode active material and a lithium secondary battery were manufactured in substantially the same manner as in Example 1, except that ZrO was mixed so that Zr was 0.2 mol % relative to 100 mol % of all metals excluding lithium in the finally obtained cathode active material.

[0146] Comparative Example 1 A cathode active material and a lithium secondary battery were manufactured using substantially the same method as in Example 1, except that ZrO2 was not added during the preparation of the cathode active material. In Comparative Example 1, the primary particles that constitute the secondary particles were not single-crystallized to a sufficient size during the heat treatment process at 810°C, and the secondary particles were not pulverized during the jet mill process. Therefore, compared with Examples 1 and 2, it was confirmed that when Al and Zr were doped by adding a certain amount of Al2O3 and ZrO2 during the first heat treatment under the same heat treatment temperature conditions, grain growth of the core particles, i.e., growth of the primary particles, or single-crystallization of the primary particles was promoted.

[0147] Comparative Example 2 A cathode active material and a lithium secondary battery were manufactured in substantially the same manner as in Example 1, except that ZrO2 was mixed so that the Zr content in the final cathode active material was 0.3 mol% relative to 100 mol% of all metals excluding lithium. Comparative Example 2 is a case where the Al / Zr ratio was 3.33, which is less than 5.

[0148] Comparative Example 3 When producing nickel-based composite hydroxide, the pH condition was increased to 12.3, and the average particle size (D 50A nickel-based composite hydroxide in the form of secondary particles having small particles with an average particle size (D ) of about 3 μm was obtained, and the average particle size (D 50 A positive electrode active material and a lithium secondary battery were manufactured in substantially the same manner as in Example 1, except that small secondary particles with a particle size of about 3 μm were obtained.

[0149] Comparative Example 4 A positive electrode active material and a lithium secondary battery were manufactured in substantially the same manner as in Example 1, except that Co(OH)2 was not mixed and cobalt coating was not performed in the preparation of the positive electrode active material.

[0150] Evaluation example 1: Evaluation of coating layer components SEM-EDS analysis was performed to evaluate the components in the coating layer of the positive electrode active material prepared in Example 1, and the results are shown in Figure 5. Here, SEM-EDS was performed using a Philips FEI Titan 80-300 at an accelerating voltage of 15 kV.

[0151] Referring to FIG. 5, it can be seen that the coating layer located on the surface of the positive electrode active material prepared in Example 1 contains cobalt (Co) and zirconium (Zr).

[0152] Evaluation example 2: Life characteristics evaluation The lithium secondary batteries produced in Example 1, Example 2, and Comparative Example 1 were initially charged and discharged at a constant current of 0.2 C to 4.45 V and a constant voltage of 0.05 C at 25°C, followed by discharging at 0.2 C to 3.0 V. Subsequently, a cycle of charging and discharging at 1.0 C in the voltage range of 3.0 V to 4.45 V at 45°C was repeated 61 times. The ratio of the discharge capacity at each cycle to the initial discharge capacity is shown in FIG. 6.

[0153] 6, it can be seen that in Comparative Example 1, the core particles of the positive electrode active material did not undergo single crystallization, and the capacity retention rate decreased with cycling. In contrast, Examples 1 and 2 exhibited excellent life characteristics.

[0154] Evaluation example 3: Charge amount evaluation A charging amount test was carried out using the positive electrode active materials prepared in Example 1 and Comparative Example 3, and the test results are shown in Table 1.

[0155] [Table 1]

[0156] Referring to the experimental results in Table 1 above, when the cathode active material prepared according to Comparative Example 3 was used, the use of a small-particle precursor resulted in significant aggregation of the single particles, resulting in separation between the upper and lower ends. This resulted in a difference in the XRD properties between the upper and lower ends.

[0157] In contrast, when the cathode active material prepared according to Example 1 was used, a large-particle precursor was used during the preparation process, and it was confirmed that there was no separation between the upper and lower ends, and there was little aggregation, resulting in a uniform cathode active material layer with little difference in the XRD properties between the upper and lower ends.

[0158] Evaluation example 4: Charge / discharge efficiency evaluation The lithium secondary batteries manufactured in Example 1 and Comparative Examples 2 to 4 were initially charged and discharged as in Evaluation Example 2, and then cycled 60 times by charging at 1.0 C and discharging at 1.0 C in a voltage range of 3.0 V to 4.45 V at 45°C. The charge capacity, discharge capacity, and charge / discharge efficiency, which is the ratio of the latter to the former, were measured and are shown in Table 2 below.

[0159] [Table 2]

[0160] Referring to Table 2, it can be seen that when the positive electrode active material prepared using the large particle precursor according to Example 1 was used, the charge capacity and discharge capacity were excellent, and the charge / discharge efficiency was also high.

[0161] On the other hand, when the cathode active material prepared according to Comparative Example 2 was used, the initial charge / discharge capacity, efficiency, and lifespan characteristics were observed to be reduced, presumably due to overgrowth of primary particles during the core particle formation process. Furthermore, when the cathode active material prepared according to Comparative Example 3 using a small particle precursor was used, the charge / discharge capacity and efficiency were not only somewhat low, but also poor. Furthermore, when the cathode active material prepared according to Comparative Example 4 was used, the charge / discharge capacity and efficiency were somewhat low due to the absence of cobalt in the coating layer.

[0162] Although the preferred embodiments have been described in detail above, the scope of the present invention is not limited to these, and various modifications and improvements made by those skilled in the art using the basic concepts defined in the claims also fall within the scope of the present invention. [Explanation of symbols]

[0163] 100 Lithium secondary battery 10 positive electrode 11 Positive electrode lead tab 12 Positive terminal 20 negative electrode 21 Negative electrode lead tab 22 Negative terminal 30 Separator 40 Electrode assembly 50 cases 60 Sealing member 70 Electrode tab 71 Positive electrode tab 72 Negative electrode tab

Claims

1. a core particle that includes a layered lithium nickel composite oxide and has a single particle form; and a coating layer located on the surface of the core particle and containing cobalt and zirconium; Including, The lithium-nickel-based composite oxide of the core particles contains aluminum and zirconium, and the nickel content is 60 mol % or more relative to 100 mol % of all metals excluding lithium, the aluminum content is 0.8 mol % to 1.5 mol %, the zirconium content is 0.1 mol % to 0.3 mol %, and the molar ratio of the aluminum content to the zirconium content (Al / Zr) is 5 or more.

2. The positive electrode active material according to claim 1 , wherein the lithium nickel-based composite oxide is represented by the following chemical formula 1: [Chemical formula 1] Li a1 N x1 M 1 y1 A z1 Zhr w1 O 2-b1 X b1 In the formula 1, 0.9≦a1≦1.2, 0.6≦x1≦0.991, 0≦y1≦0.391, 0.008≦z1≦0.015, 0.001≦w1≦0.003, 0.9≦x1+y1+z1+w1≦1.1, and 0≦b1≦0.1; M 1 is one or more elements selected from B, Ba, Ca, Ce, Co, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sn, Sr, Ti, V, W, Y, and Zn, and X is one or more elements selected from F, P, and S.

3. 2. The positive electrode active material according to claim 1, wherein the core particles have an average particle size of 1 μm to 4 μm.

4. The cathode active material of claim 1, wherein the coating layer has a thickness of 5 nm to 500 nm.

5. 2. The positive electrode active material according to claim 1, wherein the lithium nickel composite oxide has a nickel content of 80 mol % to 99 mol % relative to 100 mol % of all metals excluding lithium.

6. 2. The positive electrode active material of claim 1, wherein the cobalt content of the coating layer is 0.5 mol % to 5 mol % relative to 100 mol % of all metals excluding lithium in the positive electrode active material.

7. 2. The positive electrode active material according to claim 1, wherein the zirconium content of the coating layer is 0.1 mol % to 3 mol % relative to 100 mol % of all metals in the positive electrode active material excluding lithium.

8. a step of carrying out a coprecipitation reaction by maintaining a mixture of a nickel precursor and a metal precursor at a pH of 11 to 12 for 30 hours or more to prepare a nickel-based composite hydroxide; a step of mixing the nickel-based composite hydroxide, anhydrous lithium hydroxide, an aluminum raw material, and a zirconium raw material and performing a first heat treatment to obtain secondary particles containing a layered lithium-nickel-based composite oxide and formed by agglomeration of a plurality of primary particles; pulverizing the secondary particles; adding and mixing the pulverized product, the cobalt coating raw material, and the zirconium coating raw material into an aqueous solvent, and then performing a second heat treatment to obtain a positive electrode active material; A method for producing a positive electrode active material, comprising:

9. 9. The method for producing a positive electrode active material according to claim 8, wherein the metal of the metal precursor is one or more elements selected from B, Ba, Ca, Ce, Co, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sn, Sr, Ti, V, W, Y, and Zn.

10. 9. The method for producing a positive electrode active material according to claim 8, wherein, relative to a total of 100 mol% of all metals in the nickel-based composite hydroxide, aluminum in the aluminum raw material, and zirconium in the zirconium raw material, the aluminum content of the aluminum raw material is 0.8 mol% to 1.5 mol%, the zirconium content of the zirconium raw material is 0.1 mol% to 0.3 mol%, and a ratio of the aluminum content to the zirconium content (Al / Zr) is 5 or more.

11. The method for producing a positive electrode active material according to claim 8, wherein the nickel-based composite hydroxide has an average particle size of 10 μm to 20 μm and is in an amorphous state.

12. The aluminum source is aluminum oxide, The method for producing a positive electrode active material according to claim 8 , wherein the zirconium raw material is zirconium oxide.

13. 9. The method for producing a cathode active material according to claim 8, wherein the cobalt content of the cobalt coating raw material is adjusted to 0.5 mol % to 5 mol % and the zirconium content of the zirconium coating raw material is adjusted to 0.1 mol % to 3 mol % relative to 100 mol % of all metals excluding lithium in the finally obtained cathode active material.

14. The first heat treatment is performed in an oxidizing gas atmosphere at 700°C to 900°C for 4 hours to 20 hours, 9. The method for producing a positive electrode active material according to claim 8, wherein the second heat treatment is carried out in an oxidizing gas atmosphere at 500° C. to 900° C. for 8 hours to 20 hours.

15. The method for producing a positive electrode active material according to claim 8, wherein the nickel-based composite hydroxide is represented by the following chemical formula 11: [Chemical formula 11] Ni x11 M 1 y11 (OH) 2 In the formula 11, 0.6≦x11≦1, 0≦y11≦0.4, and 0.9≦x11+y11≦1.1; M 1 is one or more elements selected from B, Ba, Ca, Ce, Co, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sn, Sr, Ti, V, W, Y, and Zn.

16. The average particle size of the secondary particles is 10 μm to 20 μm, 9. The method for producing a positive electrode active material according to claim 8, wherein the average particle size of the primary particles constituting the secondary particles is 1 μm to 4 μm.

17. a positive electrode current collector, and A positive electrode active material layer located on the positive electrode current collector, the positive electrode active material layer comprising the positive electrode active material according to any one of claims 1 to 7. a positive electrode.

18. The positive electrode according to claim 17 . a negative electrode, and electrolyte A lithium secondary battery comprising:

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