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

Abstract

To propose a method for manufacturing a nickel-based single-particle positive electrode active material as a new one step process by omitting a process of synthesizing a positive electrode active material precursor to reduce overall production cost and processing cost and to improve processability, and provide a method for manufacturing a positive electrode active material that can achieve uniform particle size distribution, high initial discharge capacity and initial discharge efficiency, and long cycle-life characteristics, and to provide a lithium secondary battery including the positive electrode active material manufactured according to the method.SOLUTION: A method for manufacturing a positive electrode active material according to an embodiment includes: introducing, into an aqueous solvent, lithium carbonate, nickel carbonate, and cobalt carbonate and mixing them to prepare a raw material mixture; wet-pulverizing the raw material mixture; spray-drying the pulverized raw material mixture to obtain a positive electrode active material precursor mixture; and subjecting the positive electrode active material precursor mixture to heat treatment to obtain a positive electrode active material in a form of single particles and including lithium nickel-cobalt-based composite oxide.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 containing the same, and a lithium secondary battery.

Background Art

[0002] Lithium secondary batteries having a high energy density and being easy to carry are mainly used as driving power sources for mobile information terminals such as mobile phones, notebook computers, and smartphones. Recently, research has been actively conducted on using lithium secondary batteries having a high energy density as driving power sources or power storage power sources for hybrid automobiles and electric vehicles.

[0003] In order to realize a lithium secondary battery suitable for such applications, various positive electrode active materials have been studied. Among them, lithium nickel-based oxides, lithium nickel manganese cobalt composite oxides, lithium nickel cobalt aluminum composite oxides, lithium cobalt oxides, etc. are mainly used as positive electrode active materials. Nickel-based positive electrode active materials are generally in the form of secondary particles formed by aggregation of a plurality of primary particles, but a method for producing them in the form of single particles by methods such as pulverization or high heat treatment has been proposed. The nickel-based positive electrode active material in the form of single particles can improve the life characteristics, and when mixed with the form of secondary particles, the energy density can be increased.

Summary of the Invention

Problems to be Solved by the Invention

[0004] A method for producing a nickel-based single-particle positive electrode active material in a new one-step process that omits the positive electrode active material precursor synthesis process to reduce the overall production cost and processing cost and improve the processability is proposed, and a method for producing a positive electrode active material with a uniform particle size distribution, high initial discharge capacity and initial discharge efficiency, and capable of realizing long life characteristics is provided.

Means for Solving the Problems

[0005] In one embodiment, lithium carbonate, nickel carbonate, and cobalt carbonate are added to an aqueous solvent and mixed to prepare a raw material mixture. The raw material mixture is wet-milled, and the milled product is spray dried to obtain a cathode active material precursor mixture. Then, the cathode active material precursor mixture is fired to provide a method for manufacturing a cathode active material including heat-treating a cathode active material including a lithium nickel-cobalt composite oxide and being in a single particle form.

[0006] In another embodiment, a cathode active material including a lithium nickel-cobalt composite oxide and being in a single particle form, wherein the average particle diameter (D 50 ) of the single particle is 0.5 μm to 8 μm and ((D 90 -D 10 ) / D 50 ) value is 0.7 to 1.30 is provided.

[0007] In another embodiment, a lithium secondary battery including a cathode including the cathode active material, an anode, and an electrolyte is provided.

Advantages of the Invention

[0008] The method for manufacturing a cathode active material according to one embodiment is a method for manufacturing a nickel-based single particle cathode active material, in which the precursor synthesis process is omitted, and the overall production cost and processing cost are significantly reduced, and the processability is improved. The cathode active material manufactured thereby can have a very uniform particle size distribution, and the lithium secondary battery to which this is applied can achieve a high initial discharge capacity and initial charge-discharge efficiency and exhibit excellent life characteristics.

Brief Description of the Drawings

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Mode for Carrying Out the Invention

[0010] Hereinafter, specific embodiments will be described in detail so that those having ordinary knowledge in this technical field can easily implement them. However, the present invention can be realized in various different forms and is not limited to the embodiments described here.

[0011] The terms used here are used only for explaining exemplary embodiments and are not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly has a different meaning.

[0012] Here, "these combinations" means a mixture, laminate, composite, copolymer, alloy, blend, reaction product, etc. of components.

[0013] Terms such as "include", "comprise", or "have" here are intended to specify that the implemented features, numbers, steps, components, or combinations thereof exist, and it should be understood that the existence or addition possibility of one or more other features, numbers, steps, components, or combinations thereof is not precluded in advance.

[0014] The thicknesses are enlarged for clearly showing various layers and regions in the drawings, and like parts are designated by like reference numerals throughout the specification. When a part such as a layer, film, region, plate, etc. is “on” or “upon” another part, this includes not only the case where it is directly on the other part, but also the case where there are other parts in between. Conversely, when a part is “directly on” another part, it means that there are no other parts in between.

[0015] Also, herein, the “layer” includes not only the shape formed on the entire surface when observed in a plan view, but also the shape formed on a partial surface.

[0016] The average particle diameter can be measured by methods widely known to those skilled in the art. For example, it can be measured with a particle size analyzer, or it can also be measured with a transmission electron microscope image or a scanning electron microscope image. As another method, after measuring using the dynamic light scattering method and performing data analysis to count the number of particles for each particle size range, the average particle diameter value can then be calculated therefrom. Unless otherwise defined, the average particle diameter can mean the diameter (D 50 ) of the particles having a cumulative volume of 50% by volume in the particle size distribution. Also, unless otherwise defined, the average particle diameter can be obtained by randomly measuring the sizes (diameter or major axis length) of more than 20 particles with a scanning electron microscope image to obtain a particle size distribution, and taking the diameter (D 50 ) of the particles having a cumulative volume of 50% by volume in the said particle size distribution as the average particle diameter.

[0017] Herein, “or” is not construed in an exclusive sense. For example, “A or B” is construed to include A, B, A + B, etc.

[0018] “Metal” is construed as a concept including common metals, transition metals, and metalloids.

[0019] Method for manufacturing a positive electrode active material In one embodiment, a method for manufacturing a positive electrode active material is provided, which includes introducing and mixing lithium carbonate, nickel carbonate, and cobalt carbonate into an aqueous solvent to prepare a raw material mixture, wet-milling the raw material mixture, spray-drying the milled product to obtain a positive electrode active material precursor mixture, and heat-treating the positive electrode active material precursor mixture to obtain a positive electrode active material containing a lithium nickel-cobalt composite oxide and being in a single particle form.

[0020] The manufacturing method is a method for synthesizing a positive electrode active material in a single particle form through a method of mixing lithium carbonate and a carbonate-based metal raw material, wet-milling, spray-drying, and then firing. The process of synthesizing a nickel-based hydroxide by a coprecipitation method or the like is omitted, which has the effect of reducing the precursor production cost and the precursor processing cost, etc. The processability is improved as a one-step process. Also, the positive electrode active material manufactured by this method shows a more uniform particle size distribution compared to the positive electrode active material produced by the existing method, and can realize more excellent capacity, efficiency, and life characteristics.

[0021] In the raw material mixture, carbonate-based metal raw materials such as nickel carbonate and cobalt carbonate are used, and lithium carbonate is used as the lithium raw material. If a carbonate-based metal raw material and lithium carbonate are used, during the subsequent heat treatment process, the carbonate will be decomposed in the temperature range of about 700 °C to 900 °C and fly away as CO2. Through such a carbonate decomposition process, the metal raw materials can react better, and it is understood that a nickel-based positive electrode active material in a single particle form can be effectively manufactured. For example, when using a hydroxide, oxide, nitrate, sulfate, oxyhydroxide, organic acid, or chloride form as the metal raw material, in some cases, the desired nickel-based positive electrode active material in a single particle form may not be effectively synthesized by the manufacturing method according to one embodiment, and there are also disadvantages that nitrate and sulfate forms may generate harmful substances.

[0022] In addition to nickel carbonate and cobalt carbonate, other metal raw materials may be further added to the raw material mixture. For example, a manganese raw material and / or an aluminum raw material may be further added. Thereby, specifically, a lithium nickel-cobalt-manganese composite oxide, a lithium nickel-cobalt-aluminum composite oxide, or a lithium nickel-cobalt-manganese-aluminum composite oxide can be synthesized. The manganese raw material may be manganese carbonate, and the aluminum raw material may be aluminum hydroxide, aluminum oxide, or a combination thereof. That is, at the stage of preparing the raw material mixture, manganese carbonate, aluminum hydroxide, aluminum oxide, or a combination thereof can be further mixed.

[0023] In the raw material mixture, the metal raw materials can be mixed in an appropriate molar ratio. For example, the metal raw materials can be mixed so that the nickel content is 30 mol% to 99 mol% and the cobalt content is 1 mol% to 70 mol% with respect to 100 mol% of the total metal excluding lithium in the produced cathode active material. As another example, the metal raw materials can be mixed so that the nickel content is 30 mol% to 98 mol%, the cobalt content is 1 mol% to 40 mol%, and the content of manganese and / or aluminum is 1 mol% to 40 mol%.

[0024] In the raw material mixture, lithium carbonate may be mixed so that the molar ratio of lithium to the total metal of the added metal raw materials is 0.9 to 1.8. For example, it may be mixed so that the ratio is 0.9 to 1.5, 0.9 to 1.2, 0.9 to 0.99, or 1.01 to 1.1. When the molar ratio of lithium satisfies the above range, a cathode active material with high capacity and excellent structural stability can be produced.

[0025] In the step of preparing the raw material mixture, the dopant raw material can be further mixed. The dopant may be other elements excluding Ni, Co, Mn, and Al, and can include, for example, B, Ba, Ca, Ce, Cr, Fe, Mg, Mo, Nb, Si, Sn, Sr, Ti, V, W, Zr, or combinations thereof. The raw material of the dopant may be in various compound forms such as carbonate, hydroxide, oxide, oxynitride, sulfate, etc.

[0026] In the manufacturing method according to an embodiment, the raw material mixture is not mixed dry, but is mixed wet, wet-milled, and spray-dried. The wet milling may be performed using general wet milling equipment. For example, the ball milling method using zirconia beads can be applied. The wet milling may be performed at a speed of, for example, 2000 rpm to 5000 rpm, or may be performed at 3000 rpm to 4000 rpm. Also, the wet milling may be performed for 5 minutes to 120 minutes, or 10 minutes to 60 minutes. The average particle size (D 50 ) of the particles in the milled composition may be wet-milled to be 1 μm or less, or 0.5 μm or less, or 0.1 μm or less. When wet milling is performed under such conditions, a nickel-based cathode active material in the form of single particles with uniform particle size can be effectively produced.

[0027] The spray drying can be performed using a general spray drying device. For example, the spray drying can be performed at a speed of 5 mm / min to 30 mm / min, or 10 mm / min to 15 mm / min. Also, the spray drying can be performed at a temperature of, for example, 150°C to 400°C, or 200°C to 300°C. Specifically, in the spray drying step, the hot air temperature can be set to 250°C to 300°C, and the exhaust hot air temperature can be set to 100°C to 150°C. When spray drying is performed under such conditions, a nickel-based cathode active material in the form of single particles with uniform particle size can be effectively obtained.

[0028] As an example, it is also possible to recover a part of Li2CO3 in the spray drying stage. For example, Li2CO3 dissolved in water vapor is discharged during the spray drying process, and it is possible to recover and regenerate Li2CO3 through the precipitation of this solution.

[0029] The spray-dried resultant may be a mixture of lithium carbonate and metal carbonate, which can be expressed as a cathode active material precursor mixture. The obtained cathode active material precursor mixture may be in an assembled form in which small particles of, for example, 1 μm or less are aggregated.

[0030] The heat treatment of the cathode active material precursor mixture obtained by spray drying can be carried out, for example, in an oxygen atmosphere in a temperature range of 800 °C to 1000 °C, and can be carried out in a temperature range of, for example, 800 °C to 980 °C, 820 °C to 950 °C. Further, the heat treatment can be carried out for 4 hours to 24 hours, and can be carried out for, for example, 5 hours to 10 hours. By performing the heat treatment under the above conditions, a nickel-based cathode active material in the form of single particles with uniform particle size can be effectively produced.

[0031] The obtained lithium nickel-cobalt composite oxide can be represented by Chemical Formula 1 as an example. [Chemical Formula 1] Li a1 Ni x1 Co y1 M 1 z1 O 2-b1 X b1

[0032] In the above Chemical Formula 1, 0.9 ≦ a1 ≦ 1.8, 0.3 ≦ x1 < 1, 0 < y1 ≦ 0.7, 0 ≦ z1 ≦ 0.4, 0.9 ≦ x1 + y1 + z1 ≦ 1.1, and 0 ≦ b1 ≦ 0.1, and M 1 is one or more elements selected from Al, B, Ba, Ca, Ce, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sn, Sr, Ti, V, W, Y, Zn, and Zr, and X is F, P, S, or a combination thereof.

[0033] In Chemical Formula 1, 0.9 ≦ a1 ≦ 1.5, or 0.9 ≦ a1 ≦ 1.2, or 1.01 ≦ a1 ≦ 1.1 may be satisfied, 0.3 ≦ x1 ≦ 0.99, 0.01 ≦ y1 ≦ 0.7, 0 ≦ z1 ≦ 0.4, or 0.3 ≦ x1 ≦ 0.9, 0.1 ≦ y1 ≦ 0.7, 0 ≦ z1 ≦ 0.4, or 0.4 ≦ x1 ≦ 0.9, 0.1 ≦ y1 ≦ 0.6, 0 ≦ z1 ≦ 0.4, or 0.5 ≦ x1 ≦ 0.8, 0.2 ≦ y1 ≦ 0.5, 0 ≦ z1 ≦ 0.3, or 0.5 ≦ x1 ≦ 0.7, 0.3 ≦ y1 ≦ 0.5, 0 ≦ z1 ≦ 0.2 may be satisfied.

[0034] As a more specific example, the lithium nickel-cobalt composite oxide can be represented by Chemical Formula 2. Chemical Formula 2 may be a lithium nickel-cobalt-manganese composite oxide, a lithium nickel-cobalt-aluminum composite oxide, or a lithium nickel-cobalt-manganese-aluminum composite oxide. [Chemical Formula 2] Li a2 Ni x2 Co y2 M 2 z2 M 3 w2 O 2-b2 X b2

[0035] In the above Chemical Formula 2, 0.9 ≦ a2 ≦ 1.8, 0.3 ≦ x2 ≦ 0.98, 0.01 ≦ y2 ≦ 0.4, 0.01 ≦ z2 ≦ 0.4, 0 ≦ w2 ≦ 0.1, 0.9 ≦ x2 + y2 + z2 + w2 ≦ 1.1, and 0 ≦ b2 ≦ 0.1, and M 2 is Al, Mn, or a combination thereof, and M 3 is one or more elements selected from B, Ba, Ca, Ce, Cr, Cu, Fe, Mg, Mo, Nb, Si, Sn, Sr, Ti, V, W, Y, Zn, and Zr, and X is F, P, S, or a combination thereof.

[0036] In Chemical Formula 2, 0.9 ≦ a2 ≦ 1.5, or 0.9 ≦ a2 ≦ 1.2, or 1.01 ≦ a2 ≦ 1.1 may hold, and 0.3 ≦ x2 ≦ 0.9, 0.01 ≦ y2 ≦ 0.4, 0.01 ≦ z2 ≦ 0.4, 0 ≦ w2 ≦ 0.1, or 0.5 ≦ x2 ≦ 0.8, 0.1 ≦ y2 ≦ 0.4, 0.1 ≦ z2 ≦ 0.4, 0 ≦ w2 ≦ 0.1, or 0.5 ≦ x2 ≦ 0.7, 0.1 ≦ y2 ≦ 0.4, 0.1 ≦ z2 ≦ 0.4, 0 ≦ w2 ≦ 0.1 may also hold.

[0037] The average particle diameter (D 50 ) of the produced single particles may be 0.5 μm to 8 μm, for example, 1 μm to 6 μm, or 2 μm to 5 μm, and as specific examples, it may be 2.5 μm to 5.0 μm, 2.5 μm to 3.8 μm, or 2.8 μm to 3.6 μm.

[0038] According to the production method of one embodiment, the produced single particles can have a uniform particle size distribution. That is, the ratio of particles much larger or much smaller than the average particle diameter (D 50 ) can be very small. For example, the span value of the produced single particles, that is, ((D 90 - D 10 ) / D 50 ) value may be 0.7 to 2.0, for example, 0.7 to 1.5, 0.7 to 1.3, or 0.8 to 1.3. As another example, D 10 of the single particles may be 1.5 μm to 2.5 μm, and D 90 may be 5.5 μm to 6.5 μm. When the span value of the single particles satisfies the above range, it means that the particle size is uniform, thereby improving the quality of the positive electrode active material, increasing the energy density, and further realizing excellent capacity, efficiency, and life characteristics. D 50 , D 10 , and D 90 may be measured by a particle size analyzer using the laser diffraction method for a single particle.

[0039] On the one hand, the method for manufacturing a positive electrode active material according to an embodiment can further include a step of coating the obtained positive electrode active material. The coating step can apply a dry coating method or a wet coating method, and the elements to be coated may be one or more elements selected from the group consisting of, for example, Al, B, Ca, Ce, Co, Cr, Fe, Mg, Mo, Nb, Si, Sn, Sr, Ta, V, W, Zn, and Zr.

[0040] In addition, the method for manufacturing the positive electrode active material can further include a step of mixing the obtained positive electrode active material in the form of single particles with another positive electrode active material in the form of secondary particles.

[0041] Positive electrode active material In one embodiment, a positive electrode active material includes a lithium nickel-cobalt composite oxide and is in the form of single particles, and the average particle diameter (D 50 ) of the single particles is 0.5 μm to 8 μm, and the value of ((D 90 - D 10 ) / D 50 ) is 0.7 to 1.30. This can be said to be the positive electrode active material manufactured through the aforementioned method, with uniform particle size and excellent performance can be achieved.

[0042] The average particle diameter (D 50 ) of the single particles may be, for example, 1 μm to 6 μm, or 2 μm to 5 μm, and the value of ((D 90 - D 10 ) / D 50 ) may be, for example, 0.7 to 1.50, 0.7 to 1.30, or 0.8 to 1.30. As an example, D 50 of the single particles is 2.5 μm to 5.0 μm, D 10 is 1.5 μm to 2.5 μm, and D 90 may be 5.5 μm to 6.5 μm. As a specific example, D 50 of the single particles may be, for example, 2.5 μm to 3.8 μm, or 2.8 μm to 3.6 μm. D 50 , D 10 , D 90 , ((D 90 - D10 ) / D 50 ) If the value satisfies the above range, uniform particle size can be achieved, and excellent capacity, efficiency, lifespan, and energy density characteristics can be realized. D 50 , D 10 , and D 90 may be measured by a particle size analyzer using the laser diffraction method for single particles.

[0043] Here, the lithium nickel-cobalt composite oxide can be represented by Chemical Formula 1, Chemical Formula 2, etc. as described above. Also, the content regarding the average particle size and span value of single particles is as described above.

[0044] Also, the cathode active material according to one embodiment can also include the single particles and a coating layer located on the surface of the single particles, and the coating layer can include one or more elements selected from the group consisting of Al, B, Ca, Ce, Co, Cr, Fe, Mg, Mo, Nb, Si, Sn, Sr, Ta, V, W, Zn, and Zr.

[0045] The single particles can also be used after being mixed with other cathode active materials in the form of secondary particles. In this case, the single particles may be included at 5 wt% - 60 wt%, or 5 wt% - 40 wt%, or 10 wt% - 30 wt% based on the total 100 wt% of the single particles and secondary particles.

[0046] Here, a single particle (single particle) means a particle that does not have a grain boundary inside the particle and exists alone and consists of one particle, and can mean a single particle that exists as an independent phase (phase) in which particles are not agglomerated morphologically, a monolith structure or a single body structure or non-agglomerated particles, and may be, for example, a single crystal (single crystal). Single particles may exist alone, or single particles may be aggregated with each other. For example, 2 to 10 single particles may be aggregated and in contact.

[0047] Positive electrode In one embodiment, a positive electrode for a lithium secondary battery including the aforementioned positive electrode active material is provided. For example, the positive electrode includes a positive electrode current collector and a positive electrode active material layer located on the positive electrode current collector, and the positive electrode active material layer includes the aforementioned positive electrode active material and may further selectively include a binder, a conductive material, or a combination thereof.

[0048] Binder The binder serves to well adhere the positive electrode active material particles to each other and also to well adhere the positive electrode active material to the current collector. Representative examples of the binder include, but are not limited to, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, a polymer containing ethylene oxide, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene butadiene rubber, (meth)acrylated styrene butadiene rubber, epoxy resin, (meth)acrylic resin, polyester resin, nylon, and the like.

[0049] Conductive material The conductive material is used to impart conductivity to the electrode, and in the configured battery, any electron conductive material that does not cause a chemical change can be used. Examples of the conductive material include carbon-based substances such as natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, carbon fiber, carbon nanofiber, carbon nanotube; metal-based substances in the form of metal powder or metal fiber containing copper, nickel, aluminum, silver, etc.; conductive polymers such as polyphenylene derivatives; or mixtures thereof.

[0050] The contents of the binder and the conductive material may each be 0.5 wt% to 5 wt% based on 100 wt% of the positive electrode active material layer.

[0051] Although Al can be used as the positive current collector, it is not limited thereto.

[0052] Lithium secondary battery In one embodiment, a lithium secondary battery including the aforementioned positive electrode, negative electrode, and electrolyte is provided. As an example, the lithium secondary battery can include a positive electrode, a negative electrode, a separator positioned between the positive electrode and the negative electrode, and an electrolytic solution.

[0053] Lithium secondary batteries can be classified into cylindrical, square, pouch, coin, etc. according to their form. FIGS. 1 to 4 are schematic views showing a lithium secondary battery according to one embodiment, and it can be said that FIG. 1 is circular, FIG. 2 is square, and FIGS. 3 and 4 are pouch-type battery forms. Referring to FIGS. 1 to 4, the lithium secondary battery 100 can include an electrode assembly 40 in which a separator 30 is interposed between a positive electrode 10 and a negative electrode 20, and a case 50 in which the electrode assembly 40 is incorporated. The positive electrode 10, negative electrode 20, and separator 30 may be impregnated with an electrolytic solution (not shown). The lithium secondary battery 100 can include a sealing member 60 for sealing the case 50 as shown in FIG. 1. Also in FIG. 2, the lithium secondary battery 100 can include a positive electrode lead tap 11, a positive electrode terminal 12, a negative electrode lead tap 21, and a negative electrode terminal 22. As shown in FIGS. 3 and 4, the lithium secondary battery 100 can include electrode taps 70, i.e., a positive electrode tap 71 and a negative electrode tap 72, which serve as electrical paths for guiding the current formed by the electrode assembly 40 to the outside.

[0054] Negative electrode The negative electrode can include a current collector and a negative electrode active material layer positioned on the current collector, and the negative electrode active material layer can include a negative electrode active material and can further include a binder, a conductive material, or a combination thereof.

[0055] Negative electrode active material The negative electrode active material includes a material capable of reversibly intercalating / deintercalating lithium ions, lithium metal, an alloy of lithium metal, a material capable of doping and undoping with lithium, or a transition metal oxide.

[0056] As the material capable of reversibly intercalating / deintercalating the lithium ions, a carbon-based negative electrode active material can be included, 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.

[0057] 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.

[0058] As the material capable of doping and undoping with lithium, an Si-based negative electrode active material or an Sn-based negative electrode active material can be used. As the Si-based negative electrode active material, 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 may be used. As the Sn-based negative electrode active material, Sn, SnO2, an Sn alloy, or a combination thereof may be used.

[0059] The silicon-carbon composite may be a composite of silicon and amorphous carbon. The average particle size (D 50 ) of the silicon-carbon composite particles may be, for example, 0.5 μm to 20 μm. According to one embodiment, the silicon-carbon composite may be in a form in which silicon particles are coated with amorphous carbon on the surface of the silicon particles. For example, it may include secondary particles (cores) formed by granulating primary silicon particles, and an amorphous carbon coating layer (shell) located on the surface of the secondary particles. The amorphous carbon may also be located between the primary silicon particles, and for example, the primary silicon particles may be coated with amorphous carbon. The secondary particles may be dispersed in an amorphous carbon matrix.

[0060] The silicon-carbon composite may further include crystalline carbon. For example, the silicon-carbon composite may include a core containing crystalline carbon and silicon particles and an amorphous carbon coating layer located on the surface of the core. 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.

[0061] When the silicon-carbon composite contains silicon and amorphous carbon, the content of silicon may be 10% by weight to 50% by weight based on 100% by weight of the silicon-carbon composite, and the content of amorphous carbon may be 50% by weight to 90% by weight. Also, when the composite contains silicon, amorphous carbon, and crystalline carbon, the content of silicon may be 10% by weight to 50% by weight based on 100% by weight of the silicon-carbon composite, the content of crystalline carbon may be 10% by weight to 70% by weight, and the content of amorphous carbon may be 20% by weight to 40% by weight.

[0062] Also, the thickness of the amorphous carbon coating layer may be 5 nm to 100 nm. The average particle size (D 50) may be from 10 nm to 1 μm, or may be from 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 is SiO x (0 < x < 2) can be expressed as such. At this time, the atomic content ratio of Si:O indicating the degree of oxidation may be from 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.

[0063] 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 may be from 1:99 to 90:10 by weight.

[0064] Binder The binder plays a role of making the negative electrode active material particles adhere well to each other and making 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.

[0065] 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.

[0066] The aqueous 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.

[0067] When using an aqueous binder as the negative electrode binder, it may further contain a cellulose-based compound capable of imparting viscosity. As this cellulose-based compound, one or more of carboxymethyl cellulose, hydroxypropyl methyl cellulose, methyl cellulose, or alkali metal salts thereof can be mixed and used. As the alkali metal, Na, K, or Li can be used.

[0068] The dry binder is a polymer substance capable of being fibrillated, and for example, it may be polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyethylene oxide, or a combination thereof.

[0069] Conductive material The conductive material is used to impart conductivity to the electrode, and in the battery being configured, any electron conductive material that does not cause a chemical change can be used. Specific examples include carbon-based substances such as natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, carbon fiber, carbon nanofiber, carbon nanotube; metal-based substances in the form of metal powder or metal fiber containing copper, nickel, aluminum, silver, etc.; conductive polymers such as polyphenylene derivatives; or mixtures thereof.

[0070] The content of the negative electrode active material may be 95 wt% to 99.5 wt% based on 100 wt% of the negative electrode active material layer, and the content of the binder may be 0.5 wt% to 5 wt% based on 100 wt% of the negative electrode active material layer. For example, the negative electrode active material layer may contain 90 wt% to 99 wt% of the negative electrode active material, 0.5 wt% to 5 wt% of the binder, and 0.5 wt% to 5 wt% of the conductive material.

[0071] Current collector The negative electrode current collector may contain, 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, or may be 5 μm to 15 μm, or 7 μm to 10 μm.

[0072] Electrolyte The electrolyte for the lithium secondary battery may be, for example, an electrolytic solution, which may contain a non-aqueous organic solvent and a lithium salt.

[0073] The non-aqueous organic solvent serves as a medium through which ions involved in the electrochemical reaction of the battery can move. The non-aqueous organic solvent may be a carbonate-based, ester-based, ether-based, ketone-based, or alcohol-based solvent, an aprotic solvent, or a combination thereof.

[0074] As carbonate solvents, 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. can be used. As ester solvents, methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methyl propionate, ethyl propionate, decanolide, mevalonolactone, valerolactone, caprolactone, etc. can be used. As ether solvents, dibutyl ether, tetraethylene glycol dimethyl ether, diethylene glycol dimethyl ether, dimethoxyethane, 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, tetrahydrofuran, etc. can be used. Also, as ketone solvents, cyclohexanone, etc. can be used. As alcohol solvents, ethyl alcohol, isopropyl alcohol, etc. can be used, and as aprotic solvents, nitriles such as R-CN (R is a linear, branched, or cyclic hydrocarbon group having 2 to 20 carbon atoms and can contain a double bond, aromatic ring, or ether group), amides such as dimethylformamide, dioxolanes such as 1,3-dioxolane, 1,4-dioxolane, sulfolane, etc. can be used.

[0075] The non-aqueous organic solvents can be used alone or in a mixture of two or more. When used in a mixture of two or more, the mixing ratio can be appropriately adjusted according to the intended battery performance, which should be widely understood by those skilled in the art.

[0076] When using carbonate solvents, cyclic carbonates and chain carbonates can be mixed and used, and the cyclic carbonate and the chain carbonate can be mixed at a volume ratio of 1:1 to 1:9.

[0077] The non-aqueous organic solvent may further contain an aromatic hydrocarbon-based organic solvent. For example, the carbonate solvent and the aromatic hydrocarbon-based organic solvent can be used by mixing them at a volume ratio of 1:1 to 30:1.

[0078] To improve the battery life, the electrolytic solution may further contain vinyl ethyl carbonate, vinylene carbonate, or an ethylene carbonate-based compound.

[0079] Typical examples of the ethylene carbonate-based compound include fluoroethylene carbonate, difluoroethylene carbonate, chloroethylene carbonate, dichloroethylene carbonate, bromoethylene carbonate, dibromoethylene carbonate, nitroethylene carbonate, cyanoethylene carbonate, and the like.

[0080] The lithium salt is dissolved in an organic solvent, acts as a source of lithium ions in the battery to enable the operation of a basic lithium secondary battery, and plays a role in promoting the movement of lithium ions between the positive electrode and the negative electrode. Typical examples of the lithium salt include LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiAlO2, LiAlCl4, LiPO2F2, LiCl, LiI, LiN(SO3C2F5)2, Li(FSO2)2N (lithium bis(fluorosulfonyl)imide; LiFSI), LiC4F9SO3, LiN(C x F 2x+1 SO2)(C y F 2y+1 SO2)(where x and y are integers from 1 to 20), lithium trifluoromethanesulfonate, lithium tetrafluoroethanesulfonate, lithium difluorobis(oxalato)phosphate (LiDFOB), lithium bis(oxalato)borate (LiBOB), and can include one or more selected therefrom.

[0081] The concentration of the lithium salt is preferably used within the range of 0.1 M to 2.0 M. If the concentration of the lithium salt is within the above range, the electrolyte has appropriate ionic conductivity and viscosity, so it can exhibit excellent performance and lithium ions can move effectively.

[0082] Separator Depending on the type of the lithium secondary battery, a separator may be present between the positive electrode and the negative electrode. As such a separator, polyethylene, polypropylene, polyvinylidene fluoride, or a multilayer film of two or more layers thereof can be used, and mixed multilayer films such as a two-layer separator of polyethylene / polypropylene, a three-layer separator of polyethylene / polypropylene / polyethylene, and a three-layer separator of polypropylene / polyethylene / polypropylene can of course be used.

[0083] The separator may include a porous substrate and a coating layer containing an organic substance, an inorganic substance, or a combination thereof located on one or both sides of the porous substrate.

[0084] The porous substrate may be a polymer selected from any one of polyolefins such as polyethylene and polypropylene, polyesters such as polyethylene terephthalate and polybutylene terephthalate, polyacetal, polyamide, polyimide, polycarbonate, polyether ketone, polyaryl ether ketone, polyether imide, polyamide imide, polybenzimidazole, polyether sulfone, polyphenylene oxide, cyclic olefin copolymer, polyphenylene sulfide, polyethylene naphthalate, glass fiber, Teflon (registered trademark), and polytetrafluoroethylene, or a polymer film formed of a copolymer or a mixture of two or more of these.

[0085] The porous substrate can have a thickness of about 1 μm to 40 μm, for example, a thickness of 1 μm to 30 μm, 1 μm to 20 μm, 5 μm to 15 μm, or 10 μm to 15 μm.

[0086] The organic substance may include a (meth)acrylic copolymer containing 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 (meth)acrylate and a structural unit derived from (meth)acrylamidosulfonic acid or a salt thereof.

[0087] The inorganic substance may include 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, but is not limited thereto. The average particle size (D 50 ) may be 1 nm to 2000 nm, for example, 100 nm to 1000 nm, or 100 nm to 700 nm.

[0088] The organic substance and the inorganic substance may be mixed and present in one coating layer, or may be present in a form in which a coating layer containing the organic substance and a coating layer containing the inorganic substance are laminated.

[0089] The thickness of each coating layer may be 0.5 μm to 20 μm, for example, 1 μm to 10 μm, or 1 μm to 5 μm.

[0090] Hereinafter, examples and comparative examples of the present invention will be described. The following examples are merely illustrative of the present invention, and the present invention is not limited to the following examples.

Examples

[0091] Example 1 1. Manufacture of positive electrode active material As raw materials, Li2CO3, NiCO3, CoCO3, and MnCO3 were put into distilled water and mixed so that the molar ratio became Ni:Co:Mn = 50:20:30 and the molar ratio of Li / (Ni + Co + Mn) became 1.03. This was put into a wet grinding device and ball-milled at about 3500 rpm for about 30 minutes using zirconia beads having a diameter of 0.65 mm. The average particle size (D 50 ) of the particles in the pulverized composition was pulverized so as to be about 0.5 μm or less.

[0092] The pulverized composition was spray-dried at about 245 °C at 15 mm / min using a spray dryer to produce a precursor mixture.

[0093] The precursor mixture was heat-treated at 950 °C for 8 hours in an oxygen atmosphere. Then, it was crushed and filtered to produce a positive electrode active material (Li 1.03 Ni 0.5 Co 0.2 Mn 0.3 O2) according to Example 1. FIG. 5 is an SEM image of the positive electrode active material produced in Example 1, and FIG. 6 is an enlarged image thereof. Referring to FIGS. 5 and 6, it can be seen that a positive electrode active material in the form of single particles having a uniform particle size distribution was produced.

[0094] 2. Manufacture of lithium secondary battery 98.5% by weight of the produced positive electrode active material, 1.0% by weight of a polyvinylidene fluoride binder, and 0.5% by weight of a carbon nanotube conductive material were mixed to produce a positive electrode active material layer slurry, which was coated on an aluminum foil current collector, dried, and rolled to produce a positive electrode.

[0095] A structure was produced between the positive electrode and a lithium metal counter electrode via a polytetrafluoroethylene separator, and after inserting this into a battery case, an electrolyte in which 1 M LiPF6 was dissolved in a solvent in which ethylene carbonate and dimethyl carbonate were mixed at a volume ratio of 3:7 was injected to produce a lithium secondary battery (half cell) in a normal manner.

[0096] Example 2 The positive electrode active material and the lithium secondary battery were produced in substantially the same manner as in Example 1, except that the raw materials were mixed at a molar ratio of Ni:Co:Mn = 60:10:30 and the firing temperature was changed to 900 °C.

[0097] Example 3 The positive electrode active material and the lithium secondary battery were produced in substantially the same manner as in Example 1, except that the raw materials were mixed at a molar ratio of Ni:Co:Mn = 65:5:30 and the firing temperature was changed to 850 °C.

[0098] Example 4 After obtaining the positive electrode active material by the method of Example 1, aluminum oxide was mixed so that aluminum was 1 part by weight with respect to 100 mol parts of the entire metal excluding lithium in the positive electrode active material, and secondary heat treatment was performed at 850 °C for 8 hours. After that, it was crushed, filtered, and a coated positive electrode active material was obtained. Otherwise, the positive electrode active material and the lithium secondary battery were produced in substantially the same manner as in Example 1.

[0099] Example 5 Using Al2O3 instead of MnCO3 as the raw material, Li 1.03 Ni 0.88 Co 0.1 Al 0.2 The positive electrode active material and the lithium secondary battery were produced in substantially the same manner as in Example 1, except that the positive electrode active material having a composition of O2 was produced and the firing temperature was changed to 820 °C.

[0100] Comparative Example 1 After producing nickel hydroxide by a general coprecipitation method, it was mixed with a lithium raw material by a dry method and heat-treated to obtain a positive electrode active material in the form of secondary particles, which was then pulverized to produce a single-particle positive electrode active material.

[0101] Specifically, nickel sulfate (NiSO4·6H2O), cobalt sulfate (CoSO4·7H2O), and manganese sulfate (MnSO4·H2O) were put into distilled water and mixed according to the molar ratio of Ni:Co:Mn = 55:15:30 to prepare a mixed metal raw material solution. In addition, ammonia water (NH4OH) and sodium hydroxide (NaOH) as a precipitating agent were prepared for complex compound formation.

[0102] First, ammonia water with a concentration of 0.25 M was put into the reactor. With a stirring power of 3.0 kW / m 3 , at a reaction temperature of 50 °C, the reaction was started while introducing the mixed metal raw material solution and the complexing agent at rates of 142 ml / min and 34 ml / min, respectively. The reaction was carried out for 30 hours while adding NaOH to maintain the pH. The reaction was terminated when the average size of the obtained particles reached about 14 μm. After washing the product, it was dried with hot air at about 150 °C for 24 hours to produce Ni 0.55 Co 0.15 Mn 0.30 (OH)2.

[0103] The precursor and Li2CO3 were dry-mixed according to the molar ratio of Li / (Ni + Co + Mn) = 1.03 and heat-treated at 920 °C for 8 hours to obtain a lithium nickel-cobalt-manganese composite oxide in the form of secondary particles. Through an air flow impact crusher, pulverization was carried out so that the average particle size (D 50 ) became about 2.5 μm to obtain a single-particle form cathode active material (Li 1.03 Ni 0.55 Co 0.15 Mn 0.30 O2).

[0104] Comparative Example 2 A cathode active material and a lithium secondary battery were produced in substantially the same manner as in Comparative Example 1, except that the raw materials were mixed at a molar ratio of Ni:Co:Mn = 60:10:30 and the firing temperature was changed to 900 °C.

[0105] Comparative Example 3 The positive electrode active material and the lithium secondary battery were manufactured in substantially the same manner as in Comparative Example 1, except that the raw materials were mixed at a molar ratio of Ni:Co:Mn = 62:6:32 and the firing temperature was changed to 850°C.

[0106] Comparative Example 4 As raw materials, Li2CO3, NiCO3, CoCO3, and MnCO3 were mixed dry and mixed to a molar ratio of Ni:Co:Mn = 60:10:30 and a molar ratio of Li / (Ni + Co + Mn) = 1.03. This was heat-treated at 900°C for 8 hours in an oxygen atmosphere to produce a positive electrode active material according to Comparative Example 4. Otherwise, the positive electrode active material and the lithium secondary battery were manufactured in substantially the same manner as in Example 1.

[0107] Evaluation Example 1: Particle size distribution evaluation For the positive electrode active materials manufactured in Examples 1 to 4 and Comparative Examples 1 to 4, the particle size distribution was analyzed using a particle size analyzer (Particle Size Analyzer) using the laser diffraction method, and the results are shown in Table 1 below.

[0108]

Table 1

[0109] Referring to Table 1, D 50 of the examples is 2.5 μm to 5.0 μm, D10 is 1.5 μm to 2.5 μm, D90 satisfies 5.5 μm to 6.5 μm, and ((D 90 - D 10 ) / D 50 ) value satisfies 1.29 or less, indicating that it has a very uniform particle size distribution.

[0110] Evaluation Example 2: Initial charge-discharge capacity, efficiency, and life characteristic evaluation The lithium secondary batteries manufactured in Examples 1 to 3 and Comparative Examples 1 to 4 were charged at a constant current of 0.2C to 4.45V at 25°C and then at a constant voltage to 0.05C, and then discharged at 0.2C to 3.0V to perform initial charge and discharge. The initial charge capacity and initial discharge capacity are shown in Table 2 below, and the initial charge-discharge efficiency, which is the ratio of the latter to the former, is shown as efficiency in Table 2 below.

[0111] Next, a cycle of charging at 1.0C and discharging at 1.0C in a voltage range of 3.0V to 4.45V was repeated 50 times at 45°C. The ratio of the discharge capacity in 50 cycles to the initial discharge capacity was calculated and shown as the life in Table 2 below.

[0112]

Table 2

[0113] Referring to Table 2, it can be seen that Examples 1 to 3 can achieve high initial discharge capacity, initial charge-discharge efficiency, and life characteristics. It was confirmed that Example 1 has a higher initial discharge capacity, higher initial charge-discharge efficiency, and better life characteristics even compared to Comparative Example 1 with a slightly higher nickel content. Comparing Example 2 and Comparative Example 2 with the same nickel content, it can be seen that Example 2 has an increased initial discharge capacity compared to Comparative Example 2, while the initial charge-discharge efficiency is greatly improved and the life characteristics are also improved. Similarly, it was confirmed that Example 3 with a similar nickel content has a slightly increased initial discharge capacity compared to Comparative Example 3, while the initial charge-discharge efficiency is improved and the life characteristics are significantly improved. Comparative Example 4, which used the same raw materials as the examples but applied the existing solid-phase mixing method, was confirmed to have a small initial discharge capacity, low initial charge-discharge efficiency, and particularly poor life characteristics.

[0114] Thus, the method for manufacturing a positive electrode active material according to one embodiment can omit the existing precursor synthesis process, simplify the overall method, and significantly reduce the production and processing costs. Moreover, it was confirmed that the produced single-particle-shaped positive electrode active material can have a uniform particle size and can achieve better initial discharge capacity, initial charge-discharge efficiency, and life characteristics in the high voltage region.

[0115] Although the preferred embodiments have been described in detail above, the scope of the rights of the present invention is not limited thereto, and various modifications and improvements made by those skilled in the art using the basic concepts defined in the following claims also belong to the scope of the rights of the present invention.

Explanation of reference numerals

[0116] 100: Lithium secondary battery 10: Positive electrode 11: Positive electrode lead tap 12: Positive electrode terminal 20: Negative electrode 21: Negative electrode lead tap 22: Negative electrode terminal 30: Separator 40: Electrode assembly 50: Case 60: Sealing member 70: Electrode tap 71: Positive electrode tap 72: Negative electrode tap

Claims

1. Charge lithium carbonate, nickel carbonate, and cobalt carbonate into an aqueous solvent, mix them to prepare a raw material mixture, wet grind the raw material mixture, spray dry the ground product to obtain a positive electrode active material precursor mixture, and heat-treat the positive electrode active material precursor mixture to obtain a positive electrode active material containing a lithium nickel-cobalt composite oxide and having a single particle form. A method for manufacturing a positive electrode active material, comprising:

2. In the step of preparing the raw material mixture, further mix manganese carbonate, aluminum hydroxide, aluminum oxide, or a combination thereof. The method for manufacturing a positive electrode active material according to Claim 1.

3. In the step of preparing the raw material mixture, further mix a dopant raw material, wherein the dopant includes B, Ba, Ca, Ce, Cr, Fe, Mg, Mo, Nb, Si, Sn, Sr, Ti, V, W, Zr, or a combination thereof. The method for manufacturing a positive electrode active material according to Claim 1.

4. The wet grinding is performed by using zirconia ball milling at 2000 rpm to 5000 rpm for 5 minutes to 120 minutes. The method for manufacturing a positive electrode active material according to Claim 1.

5. The wet grinding is to grind until the average particle size (D 50 ) of the ground particles becomes 0.5 μm or less. The method for producing a positive electrode active material according to claim 1.

6. The spray drying is performed by setting the hot air temperature to 200°C to 300°C and the exhaust hot air temperature to 100°C to 150°C. The method for manufacturing a positive electrode active material according to Claim 1.

7. The heat treatment of the positive electrode active material precursor mixture is performed in an oxygen atmosphere at a temperature range of 800°C to 1000°C for 4 hours to 24 hours. The method for manufacturing a positive electrode active material according to Claim 1.

8. The obtained lithium nickel-cobalt composite oxide is represented by Chemical Formula 1. The method for manufacturing a positive electrode active material according to Claim 1: [Chemical Formula 1] Li a1 Ni x1 Co y1 M 1 z1 O₂ -b1 X b1 In the above chemical formula (1), 0.9 ≤ a1 ≤ 1.8, 0.3 ≤ x1 < 1, 0 < y1 ≤ 0.7, 0 ≤ z1 ≤ 0.4, 0.9 ≤ x1 + y1 + z1 ≤ 1.1, and 0 ≤ b1 ≤ 0.1, and M 1 is one or more elements selected from Al, B, Ba, Ca, Ce, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sn, Sr, Ti, V, W, Y, Zn, and Zr, and X is F, P, S, or a combination thereof.

9. The obtained lithium nickel-cobalt composite oxide is represented by Chemical Formula 2. The method for manufacturing a positive electrode active material according to Claim 8: [Chemical Formula 2] Li a2 Ni x2 Co y2 M 2 z2 M 3 w2 O 2-b2 X b2 In the above Chemical Formula 2, 0.9 ≤ a2 ≤ 1.8, 0.3 ≤ x2 ≤ 0.98, 0.01 ≤ y2 ≤ 0.4, 0.01 ≤ z2 ≤ 0.4, 0 ≤ w2 ≤ 0.1, 0.9 ≤ x2 + y2 + z2 + w2 ≤ 1.1, and 0 ≤ b2 ≤ 0.1, and M 2 is Al, Mn, or a combination thereof, and M 3 is one or more elements selected from B, Ba, Ca, Ce, Cr, Cu, Fe, Mg, Mo, Nb, Si, Sn, Sr, Ti, V, W, Y, Zn, and Zr, and X is F, P, S, or a combination thereof.

10. The average particle size (D 50 ) of the produced single particles is 0.5 μm to 8 μm, and the method for producing a positive electrode active material according to claim 1.

11. The ((D 90 -D 10 ) / D 50 ) value of the manufactured single particles is 0.7 to 2.

0. The method for producing a positive electrode active material according to claim 1.

12. The method for manufacturing a positive electrode active material according to Claim 1 further includes a step of coating the obtained positive electrode active material.

13. The coating step includes dry-mixing the positive electrode active material and a coating raw material and heat-treating them, or charging the positive electrode active material and the coating raw material into an aqueous solvent, mixing them, drying, and then heat-treating them. The method for manufacturing a positive electrode active material according to Claim 12.

14. The coating element used in the coating step contains Al, B, Ca, Ce, Co, Cr, Fe, Mg, Mo, Nb, Si, Sn, Sr, Ta, V, W, Zn, Zr, or a combination thereof, and is a method for producing a positive electrode active material according to claim 12.

15. A positive electrode active material containing a lithium nickel-cobalt composite oxide and having a single particle form, The average particle size (D 50 ) of the single particles is 0.5 μm to 8 μm, and ((D 90 - D 10 ) / D 50 ) value is 0.7 to 1.30, the positive electrode active material.

16. The D of the single particle 50 is 2.5 μm to 5.0 μm, and D 10 is 1.5 μm to 2.5 μm, and D 90 is 5.5 μm to 6.5 μm, The positive electrode active material according to claim 15

17. A positive electrode manufactured by the method according to any one of claims 1 to 14, or a positive electrode containing the positive electrode active material according to claim 15 or 16, a negative electrode, and a lithium secondary battery including an electrolyte.

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