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

Abstract

To provide a positive electrode active material having high energy density and excellent high-temperature life.SOLUTION: The present invention relates to a positive electrode active material for a lithium secondary battery, a method for manufacturing the same, and a lithium secondary battery including the same, and more specifically, to a first particle containing a first lithium composite oxide. The first particle includes first primary particles extending radially from the center toward the surface thereof, and second primary particles provided on the surface, the first primary particles having an aspect ratio of 2 to 15, and the second primary particles having an aspect ratio of 0.7 to 3.SELECTED DRAWING: Figure 7

Description

Technical Field

[0001] The present invention relates to a positive electrode active material for a lithium secondary battery, a method for manufacturing the same, and a lithium secondary battery including the same. More specifically, the present invention relates to a positive electrode active material including a layered lithium compound, a method for manufacturing the same, and a lithium secondary battery including the same.

Background Art

[0002] Recently, with the rapid spread of electronic devices using batteries such as mobile phones, notebook computers, and electric vehicles, the demand for secondary batteries with high energy density and high capacity has been rapidly increasing. Therefore, research and development for improving the performance of lithium secondary batteries have been actively conducted.

[0003] A lithium secondary battery is a battery including a positive electrode and a negative electrode containing an active material capable of insertion (intercalation) and desorption (deintercalation) of lithium ions, and an electrolyte, and produces electrical energy by oxidation and reduction reactions when lithium ions are inserted / desorbed at the positive electrode and the negative electrode.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The problem to be solved by the present invention is to provide a positive electrode active material having a high energy density and excellent high-temperature life.

[0006] The problem to be solved by the present invention is to provide a lithium secondary battery having a high energy density and excellent high-temperature life.

Means for Solving the Problems

[0007] The positive electrode active material according to the concept of the present invention can include first particles containing a first lithium composite oxide. The first lithium composite oxide is represented by the following Chemical Formula 1. [Chemical Formula 1] Li a1 Ni x1 Ma 1-x1 O b1

[0008] In Chemical Formula 1, a1 is from 0.5 to 1.5, x1 is from 0.6 to 0.99, b1 is from 1.8 to 2.2, 1 - x1 is from 0.01 to 0.4, and Ma can include at least one element selected from the group consisting of Co, Al, Mn, Na, Mg, Ca, Y, Ti, Hf, V, Nb, Ta, Cr, Mo, W, Zr, Sr, La, Fe, Cu, Ag, Zn, Ga, C, Si, and Sn. The first particles include first primary particles extending radially from the center thereof toward the surface thereof and second primary particles provided on the surface. The aspect ratio of the first primary particles is from 2 to 15, and the aspect ratio of the second primary particles can be from 0.7 to 3.

[0009] The positive electrode active material according to another concept of the present invention can include first particles containing a first lithium composite oxide. The first lithium composite oxide is represented by the following Chemical Formula 1. [Chemical Formula 1] Li a1 Ni x1 Ma 1-x1 O b1

[0010] In Chemical Formula 1, a1 is from 0.5 to 1.5, x1 is from 0.6 to 0.99, b1 is from 1.8 to 2.2, 1 - x1 is from 0.01 to 0.4, and Ma can include at least one element selected from the group consisting of Co, Al, Mn, Na, Mg, Ca, Y, Ti, Hf, V, Nb, Ta, Cr, Mo, W, Zr, Sr, La, Fe, Cu, Ag, Zn, Ga, C, Si, and Sn. The first particle includes first primary particles extending in the radial direction from its center to its surface and second primary particles provided on the surface. The angle formed by the a-axis of the first primary particles and the radial direction is from 0° to 5°, and the angle formed by the a-axis of the second primary particles and the radial direction can be from 10° to 80°.

[0011] A lithium secondary battery according to another concept of the present invention can include the above-described positive electrode active material.

Advantages of the Invention

[0012] The positive electrode active material according to the present invention can include radial first primary particles and amorphous second primary particles provided at one end of the first primary particles. Through the morphology of the positive electrode active material, the positive electrode active material can have a uniform coating layer and can improve structural stability. The positive electrode active material according to the present invention can prevent the generation of internal cracks due to shrinkage and expansion, and thus can improve the charge-discharge capacity and life characteristics of the secondary battery.

Brief Description of the Drawings

[0013]

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Mode for Carrying Out the Invention

[0014] To fully understand the configuration and effects of the present invention, the preferred embodiments of the present invention will be described with reference to the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, can be realized in various forms, and various modifications can be made. The following embodiments are provided merely to complete the disclosure of the present invention through the description of the present embodiments and to fully inform those with ordinary knowledge in the technical field to which the present invention pertains of the scope of the invention.

[0015] As used herein, when a component is referred to as being on another component, it means that it is either directly formed on the other component or a third component can intervene therebetween. Also, in the drawings, the thickness of components is exaggerated for the efficient explanation of technical content. Parts denoted by the same reference numeral throughout the specification denote the same components.

[0016] Unless otherwise specified herein, singular forms can also include plural forms. Further, unless otherwise specified, "A or B" can mean "including A, including B, or including both A and B". The components referred to herein by "comprises" and / or "comprising" do not exclude the presence or addition of one or more other components.

[0017] As used herein, "these combinations" can mean mixtures of compositions, laminates, composites, copolymers, alloys, blends, reaction products, and the like.

[0018] Unless otherwise defined in this specification, the particle size can be the average particle size. Also, the particle size means the average particle size (D50) which is the diameter of the particle with a cumulative volume of 50% in the particle size distribution. The measurement of the average particle size (D50) can be carried out by methods widely known to those skilled in the art. For example, it can be measured with a particle size analyzer, or it can be measured from a transmission electron microscope (TEM) photograph or a scanning electron microscope (SEM) photograph. As another method, a measuring device using the dynamic light-scattering method can be used for measurement. After performing data analysis to count the number of particles for each particle size range, the average particle size (D50) value can be calculated therefrom. Or, it can be measured using the laser scattering method. In the case of measurement by the laser scattering method, specifically, after dispersing the particles to be measured in a dispersion medium, it is introduced into a commercially available laser scattering particle size measuring device (for example, MT3000 of Microtrac), irradiated with ultrasonic waves of about 28 kHz at an output of 60 W, and then the average particle size (D50) at the 50% standard of the particle size distribution can be calculated by the measuring device.

[0019] The term "atomic fraction" used in the present invention can be obtained from the results of analyzing the elements on the surface of the positive electrode active material CAM using an energy dispersive spectrometer (EDS), namely SEM-EDS and TEM-EDS. The atoms on the surface of the positive electrode active material CAM that collide with the electron beam can emit characteristic X-rays. The emitted X-rays are analyzed through an EDS detector to confirm the type and content of the corresponding elements. Here, the obtained content can correspond to the atomic fraction.

[0020] Figure 1 is a conceptual diagram briefly showing a lithium secondary battery according to an embodiment of the present invention. Referring to Figure 1, the lithium secondary battery can include a positive electrode 10, a negative electrode 20, a separator 30, and an electrolytic solution ELL.

[0021] The positive electrode 10 and the negative electrode 20 may be separated from each other via a separator 30. The separator 30 can be disposed between the positive electrode 10 and the negative electrode 20. The positive electrode 10, the negative electrode 20, and the separator 30 can be in contact with the electrolytic solution ELL. The positive electrode 10, the negative electrode 20, and the separator 30 can be immersed in the electrolytic solution ELL.

[0022] The electrolytic solution ELL can be a medium for transmitting lithium ions between the positive electrode 10 and the negative electrode 20. In the electrolytic solution ELL, the lithium ions can move through the separator 30 and toward the positive electrode 10 or the negative electrode 20.

[0023] Positive electrode 10 The positive electrode 10 for a lithium secondary battery can include a current collector COL1 and a positive electrode active material layer AML1 formed on the current collector COL1. The positive electrode active material layer AML1 contains a positive electrode active material and can further contain a binder and / or a conductive material. A detailed description of the positive electrode active material layer AML1 according to an embodiment of the present invention will be described later with reference to FIG. 6. Al can be used as the current collector COL1, but is not limited thereto.

[0024] Negative electrode 20 The negative electrode 20 for a lithium secondary battery includes a current collector COL2 and a negative electrode active material layer AML2 located on the current collector COL2. The negative electrode active material layer AML2 contains a negative electrode active material and can further contain a binder and / or a conductive material.

[0025] For example, the negative electrode active material layer AML2 can contain 90% to 99% by weight of the negative electrode active material, 0.5% to 5% by weight of the binder, and 0% to 5% by weight of the conductive material.

[0026] The binder serves to make the negative electrode active material particles adhere well to each other and to make the negative electrode active material adhere well to the current collector COL2. As the binder, a non-aqueous binder, an aqueous binder, a dry binder, or a combination thereof can be used.

[0027] 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.

[0028] Examples of the aqueous binder may include styrene-styrene rubber, (meth)acrylate styrene-styrene rubber, (meth)acrylonitrile-styrene rubber, (meth)acrylic rubber, butyl rubber, fluororubber, polyethylene oxide, polyvinyl pyrrolidone, polyepichlorohydrin, polyphosphazene, poly(meth)acrylonitrile, ethylene-propylene-diene copolymer, polyvinyl pyridine, chlorosulfonated polyethylene, latex, polyester resin, (meth)acrylic resin, phenol resin, epoxy resin, polyvinyl alcohol, and a combination thereof.

[0029] When using an aqueous binder as the negative electrode binder, a cellulose-based compound capable of imparting viscosity can be further included. Examples of this cellulose-based compound include carboxymethyl cellulose, hydroxypropyl methyl cellulose, methyl cellulose, or a mixture of one or more of their alkali metal salts. As the alkali metal, Na, K, or Li can be used.

[0030] The dry binder may be a polymer substance capable of being fibrillated, for example, polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyethylene oxide, or a combination thereof.

[0031] The conductive material is used to impart conductivity to the electrode, and in the battery being configured, any material can be used as long as it is an electron conductive material without causing a chemical change. Specific examples include carbon-based substances such as natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, carbon fiber, carbon nanofiber, carbon nanotube, etc.; metal-based substances containing copper, nickel, aluminum, silver, etc. in the form of metal powder or metal fiber; conductive polymers such as polyphenylene derivatives; or mixtures thereof.

[0032] As the current collector COL2, those selected from copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, a polymer substrate coated with a conductive metal, and combinations thereof can be used.

[0033] Negative electrode active material The negative electrode active material in the negative electrode active material layer AML2 includes a material capable of reversibly intercalating / deintercalating lithium ions, lithium metal, an alloy of lithium metal, a material capable of doping and dedoping lithium, or a transition metal oxide.

[0034] The material capable of reversibly intercalating / deintercalating the lithium ions is a carbon-based negative electrode active material, and can include, for example, crystalline carbon, amorphous carbon, or a combination thereof. Examples of the crystalline carbon can include graphite such as amorphous, plate-like, flake, spherical, or fibrous natural graphite or artificial graphite, and examples of the amorphous carbon can include soft carbon or hard carbon, mesophase pitch carbide, fired coke, etc.

[0035] 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.

[0036] As the substance capable of doping and undoping lithium, a Si-based negative electrode active material or a 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), a Si-Q alloy (wherein Q is selected from an alkali metal, an alkaline earth metal, a Group 13 element, a Group 14 element (excluding Si), a Group 15 element, a Group 16 element, a transition metal, a rare earth element, and combinations thereof), or a combination thereof. The Sn-based negative electrode active material can be Sn, SnO2, a Sn-based alloy, or a combination thereof.

[0037] The silicon-carbon composite can be a composite of silicon and amorphous carbon. According to one embodiment, the silicon-carbon composite can be in a form in which silicon particles are coated with amorphous carbon on the surface of the silicon particles. For example, it can include secondary particles (cores) assembled from primary silicon particles and a first coating layer (shell) of amorphous carbon located on the surface of the secondary particles. The amorphous carbon can also be located between the primary silicon particles, and for example, the primary silicon particles can be coated with amorphous carbon. The secondary particles can be dispersed in an amorphous carbon matrix.

[0038] The silicon-carbon composite may further include crystalline carbon. For example, the silicon-carbon composite can include a core containing crystalline carbon and silicon particles and a first coating layer of amorphous carbon located on the surface of the core.

[0039] 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.

[0040] Separator 30 A separator 30 may be present between the positive electrode 10 and the negative electrode 20 depending on the type of the lithium secondary battery. As such a separator 30, polyethylene, polypropylene, polyvinylidene fluoride, or a multilayer film of two or more layers thereof can be used, and a mixed multilayer film such as a polyethylene / polypropylene two-layer separator, a polyethylene / polypropylene / polyethylene three-layer separator, or a polypropylene / polyethylene / polypropylene three-layer separator can of course be used.

[0041] The separator 30 can include a porous substrate and a first coating layer including an organic substance, an inorganic substance, or a combination thereof located on one or both surfaces of the porous substrate.

[0042] The porous substrate can be a polymer film 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, 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 copolymer or mixture of two or more of these.

[0043] The organic substance can include a polyvinylidene fluoride-based polymer or a (meth)acrylic-based polymer.

[0044] The inorganic substance can 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.

[0045] The organic matter and the inorganic matter may exist mixed in one first coating layer, or may exist in a form in which a first coating layer containing the organic matter and a first coating layer containing the inorganic matter are laminated.

[0046] Electrolyte ELL The electrolytic solution ELL for a lithium secondary battery contains a non-aqueous organic solvent and a lithium salt.

[0047] The non-aqueous organic solvent serves as a medium through which ions involved in the electrochemical reaction of the battery can move.

[0048] The non-aqueous organic solvent can be a carbonate-based, ester-based, ether-based, ketone-based, or alcohol-based solvent, an aprotic solvent, or a combination thereof.

[0049] Examples of the carbonate-based solvent 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., which can be used.

[0050] Examples of the ester-based solvent include methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methyl propionate, ethyl propionate, decanolide, mevalonolactone, valerolactone, caprolactone, etc., which can be used.

[0051] As the ether solvent, dibutyl ether, tetraethylene glycol dimethyl ether, diglyme, dimethoxyethane, 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, tetrahydrofuran, etc. can be used. Also, as the ketone solvent, cyclohexanone, etc. can be used. As the alcohol solvent, ethyl alcohol, isopropyl alcohol, etc. can be used, and as the aprotic solvent, nitriles such as R-CN (R is a linear, branched, or cyclic hydrocarbon group having 2 to 20 carbon atoms and may contain a double bond, an aromatic ring, or an ether group); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane, 1,4-dioxolane; sulfolanes, etc. can be used.

[0052] The non-aqueous organic solvent can be used alone or in a mixture of two or more.

[0053] Also, when using a carbonate solvent, a cyclic carbonate and a chain carbonate 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.

[0054] 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. 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, 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(oxalate)phosphate (LiDFOB), lithium bis(oxalate)borate (LiBOB), and can include one or more selected therefrom.

[0055] Lithium secondary battery Lithium secondary batteries can be classified into cylindrical, rectangular, pouch, coin, etc. according to their form. Figures 2 to 5 are schematic views showing a lithium secondary battery according to an embodiment. Figure 2 shows a cylindrical type, Figure 3 shows a rectangular type, and Figures 4 and 5 show a pouch type battery form. Referring to Figures 2 to 4, the lithium secondary battery 100 can include an electrode assembly 40 with a separator 30 interposed between a positive electrode 10 and a negative electrode 20, and a case 50 in which the electrode assembly 40 is housed. The positive electrode 10, the negative electrode 20, and the separator 30 can be immersed in an electrolyte (not shown). The lithium secondary battery 100 can include a sealing member 60 for sealing the case 50 as shown in Figure 2. Also, in Figure 3, the lithium secondary battery 100 can 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 Figures 4 and 5, the lithium secondary battery 100 can include electrode tabs 70, i.e., a positive electrode tab 71 and a negative electrode tab 72, which serve as an electrical path for guiding the current formed by the electrode assembly 40 to the outside.

[0056] The lithium secondary battery according to an embodiment of the present invention can be applied to automobiles, mobile phones, and / or various forms of electrical devices, etc., but the present invention is not limited thereto.

[0057] FIG. 6 is an enlarged view showing the positive electrode active material layer of the lithium secondary battery according to an embodiment of the present invention. Referring to FIG. 6, as described above, the positive electrode active material layer AML1 (see FIG. 1) can include first particles PTC1, second particles PTC2, a conductive material CDM, and a binder BND. The plurality of first particles PTC1 and the plurality of second particles PTC2 can constitute the positive electrode active material according to an embodiment of the present invention. As one embodiment, the positive electrode active material layer AML1 can further include a plurality of aggregates ZAG. As one embodiment, the positive electrode active material layer AML1 can further include an additive that can serve as a sacrificial positive electrode.

[0058] The content of the positive electrode active materials (PTC1 and PTC2) in the positive electrode active material layer AML1 can be 90% by weight to 99.5% by weight with respect to 100% by weight of the positive electrode active material layer AML1. The contents of the binder BND and the conductive material CDM can be 0.5% by weight to 5% by weight, respectively, with respect to 100% by weight of the positive electrode active material layer AML1.

[0059] The binder BND can bond the first particles PTC1, the second particles PTC2, and the conductive material CDM to each other. As an example, the binder BND can include at least one selected from the group consisting of polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl fluoride, polyvinyl fluoride, a polymer containing ethylene oxide, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, (meth)acrylate styrene-butadiene rubber, epoxy resin, (meth)acrylic resin, polyester resin, and nylon, but is not limited thereto.

[0060] The conductive material CDM can be used to improve the conductivity of the positive electrode active material layer AML1. Any conductive material that does not cause a chemical change in the positive electrode active material layer AML1 can be used as the conductive material CDM without limitation. For example, the conductive material CDM can include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, carbon fiber, carbon nanofiber, carbon nanotube, etc.; metal-based materials containing copper, nickel, aluminum, silver, etc. in the form of metal powder or metal fiber; conductive polymers such as polyphenylene derivatives; or mixtures thereof.

[0061] Hereinafter, each of the first particle PTC1 and the second particle PTC2 will be described in more detail.

[0062] The first particle PTC1 can have a first average particle diameter APD1, and the second particle PTC2 can have a second average particle diameter APD2. The second average particle diameter APD2 may be smaller than the first average particle diameter APD1. For example, the first average particle diameter APD1 can be from 6.0 μm to 20.0 μm. The second average particle diameter APD2 can be from 1.0 μm to 5.0 μm. In the present invention, the first particle PTC1 may be referred to as a large particle, and the second particle PTC2 may be referred to as a small particle. Each of the first and second particles PTC1 and PTC2 can have a granular or spherical shape.

[0063] The positive electrode active material according to an embodiment of the present invention can be in a bimodal form including large particles (e.g., PTC1) and small particles (e.g., PTC2) having different average particle diameters. By filling the voids between the large particles with the small particles, the packing density of the positive electrode active material layer AML1 can be improved. In other words, the positive electrode active material layer AML1 according to the embodiment of the present invention can have a relatively high energy density per unit volume.

[0064] As one embodiment, the first particles PTC1 and the second particles PTC2 in the positive electrode active material CAM can have a weight ratio of 95:5 to 50:50. As another embodiment, the first particles PTC1 and the second particles PTC2 in the positive electrode active material CAM can have a weight ratio of 5:95 to 50:50. As an example, the weight of the first particles PTC1 in the positive electrode active material CAM may be greater than the weight of the second particles PTC2.

[0065] As one embodiment, the positive electrode active material can include only the first particles PTC1. In other words, the second particles PTC2 may be omitted.

[0066] The first particles PTC1 can include a first lithium composite oxide, and the second particles PTC2 can include a second lithium composite oxide. Each of the first and second lithium composite oxides can include nickel (Ni) and zirconium (Zr). Each of the first and second lithium composite oxides can further include at least one metal selected from the group consisting of cobalt (Co), manganese (Mn), and aluminum (Al).

[0067] For example, the first lithium composite oxide can be represented by the following Chemical Formula 1. [Chemical Formula 1] Li a1 Ni x1 Ma 1-x1 O b1

[0068] In Chemical Formula 1, a1 is from 0.5 to 1.5, x1 is from 0.6 to 0.99, b1 is from 1.8 to 2.2, and 1 - x1 can be from 0.01 to 0.4. Ma can include at least one element selected from the group consisting of Co, Al, Mn, Na, Mg, Ca, Y, Ti, Hf, V, Nb, Ta, Cr, Mo, W, Zr, Sr, La, Fe, Cu, Ag, Zn, Ga, C, Si, and Sn. As one embodiment, Ma can include Co, Al, and Mn. In the present invention, transition metals can also include post-transition metals such as Al.

[0069] The first lithium composite oxide can further contain boron (B) as a dopant. In one embodiment, the concentration of boron (B) in the first lithium composite oxide can be from 1 ppm to 2,000 ppm. However, since boron (B) is in extremely small amounts, it may not be detected in the first lithium composite oxide.

[0070] The second lithium composite oxide can be represented by the following Chemical Formula 2. [Chemical Formula 2] Li a2 Ni x2 Mb 1-x2 Fl w2 O b2

[0071] In Chemical Formula 2, a2 is from 0.5 to 1.5, x2 is from 0.6 to 0.99, b2 is from 1.8 to 2.2, and 1 - x2 can be from 0.01 to 0.4. w2 can be from 0.0005 to 0.01. Mb can contain at least one element selected from the group consisting of Co, Al, Mn, Na, Mg, Ca, Y, Ti, Hf, V, Nb, Ta, Cr, Mo, W, Zr, Sr, La, Fe, Cu, Ag, Zn, B, Ga, C, Si, and Sn. In one embodiment, Mb can contain Co, Al, and Mn. Fl can contain at least one element selected from the group consisting of Zr, Sr, Y, La, Mo, Ce, Nb, and S. Fl can be derived from the flux used in the firing of the second particle PTC2.

[0072] The Ma of the first lithium composite oxide and the ratio of the elements constituting it can be different from the Mb of the second lithium composite oxide and the ratio of the elements constituting it. For example, Ma of the first lithium composite oxide can contain Co and Al, and Mb of the second lithium composite oxide can contain Co and Mn. As another example, each of Ma and Mb can contain Co, Al, and Mn. At this time, the composition ratio of Al in Ma may be larger than the composition ratio of Al in Mb, and the composition ratio of Mn in Ma may be smaller than the composition ratio of Mn in Mb. The first lithium composite oxide can further contain boron (B) as a dopant. Boron (B) may be excluded from the second lithium composite oxide.

[0073] As one embodiment of the present invention, x1 which is the molar ratio of Ni in Chemical Formula 1 may be greater than 0.8. When the first lithium composite oxide has a high-content nickel composition (x1 > 0.8), the firing of the first lithium composite oxide can be carried out at a relatively low temperature. Therefore, in the manufacturing process of the positive electrode active material for a lithium secondary battery described later, the first particles PTC1 can be synthesized at a relatively low temperature. Ni in the first lithium composite oxide can affect the output and capacity of the lithium secondary battery. The present invention can provide a high-output lithium secondary battery by using the first lithium composite oxide having a high-content nickel composition. x2 which is the molar ratio of Ni in Chemical Formula 2 may also be greater than 0.8. However, x2 can be different from x1.

[0074] As the content of Ni in the first and second lithium composite oxides increases, the stability of the positive electrode or the secondary battery may decrease. As one embodiment of the present invention, the first and second lithium composite oxides can further contain Co, thereby improving the stability and capacity maintenance characteristics of the secondary battery.

[0075] As one embodiment of the present invention, the first particles PTC1 can have a polycrystal shape. The first particles PTC1 can contain secondary particles in which at least two or more primary particles are aggregated.

[0076] As one embodiment, the first particle PTC1 can include a first coating layer CTL1 on its surface. The first coating layer CTL1 can cover the entire surface or at least a part of the surface of the first particle PTC1. By coating the first particle PTC1 with the first coating layer CTL1, the structural collapse due to repeated charge and discharge can be effectively suppressed, and the normal temperature and high temperature life characteristics can be improved.

[0077] The first coating layer CTL1 can include, as a metal-containing compound, for example, a cobalt compound and a zirconium compound. The metal-containing compound can include a metal oxide, a metal hydroxide, a metal carbonate, or a combination thereof.

[0078] The first coating layer CTL1 can further include other metal or non-metal elements in addition to cobalt and zirconium. The first coating layer CTL1 may further include lithium, manganese, and / or nickel, etc. For example, the first coating layer CTL1 can include lithium cobalt zirconium oxide.

[0079] The content of cobalt relative to the total amount of transition metals (for example, Ni + Co + Al + Mn + Zr) in the first coating layer CTL1 can be 20 at% to 50 at%. The content of zirconium relative to the total amount of transition metals in the first coating layer CTL1 can be 0.001 at% to 1 at%. Or, the content of zirconium relative to the total amount of transition metals in the first coating layer CTL1 can be 0.002 at% or less. The content of cobalt in the first coating layer CTL1 may be greater than the content of zirconium. The ratio of cobalt to zirconium (Co / Zr) in the first coating layer CTL1 can be 10,000 or more.

[0080] As one embodiment of the present invention, the second particle PTC2 can have a single particle shape. A single particle can be meant to have no grain boundary within the particle, exist independently, and be composed of one particle. A single particle can mean a single particle, a monolith structure, a single body structure, or non-aggregated particles that exist as an independent phase in which particles are not mutually aggregated morphologically. As an example, the single particle can be a single crystal. The positive electrode active material according to one embodiment can exhibit improved life characteristics while realizing high capacity and high energy density by including the second particle PTC2 in a single particle form.

[0081] As one embodiment, the second particle PTC2 can include a second coating layer CTL2 on its surface. By coating the second particle PTC2 with the second coating layer CTL2, the structural collapse due to repeated charge and discharge can be effectively suppressed, and the normal temperature and high temperature life characteristics can be improved.

[0082] The second coating layer CTL2 can include, as a metal-containing compound, for example, a cobalt compound and a zirconium compound. The description of the second coating layer CTL2 can be the same as or similar to the description of the previous first coating layer CTL1.

[0083] The content of cobalt relative to the total amount of transition metals in the second coating layer CTL2 can be 20 at% to 50 at%. The content of zirconium relative to the total amount of transition metals in the second coating layer CTL2 can be 0.002 at% to 0.2 at%. As one embodiment, the content of cobalt in the second coating layer CTL2 may be smaller than the content of cobalt in the first coating layer CTL1. As one embodiment, the content of zirconium in the second coating layer CTL2 may be larger than the content of zirconium in the first coating layer CTL1.

[0084] According to an embodiment of the present invention, the second coating layer CTL2 of the second particle PTC2 can have a higher zirconium content than the first coating layer CTL1 of the first particle PTC1. Thereby, the ionic conductivity on the surface of the second particle PTC2 can be increased. In other words, even if the second particle PTC2 is fired at a relatively high temperature and has a single particle shape, the durability and capacity maintenance characteristics of the secondary battery can be improved through the second coating layer CTL2 having a relatively high zirconium content.

[0085] The composition of each of the first and second coating layers CTL1 and CTL2 can be obtained through quantitative analysis by performing scanning electron microscope-energy dispersive X-ray spectroscopy (SEM-EDS) on the particle surface. As a method for measuring the composition, in addition to SEM-EDS, inductively coupled plasma mass spectrometry (ICP-MS), inductively coupled plasma optical emission spectroscopy (ICP-OES), or the like can be used.

[0086] The first and second coating layers CTL1 and CTL2 according to an embodiment of the present invention may not be confirmed in an image through an electron microscope. The first and second coating layers CTL1 and CTL2 can be confirmed through the presence of cobalt and zirconium on the particle surface using SEM-EDS.

[0087] FIG. 7 is an enlarged view showing a cross section of the first particle according to an embodiment of the present invention. FIG. 8 is an enlarged view of the M region in FIG. 7, and is a cross-sectional view schematically showing the first primary particle and the second primary particle.

[0088] Referring to FIGS. 7 and 8, the first particle PTC1 can include a plurality of crystallites. The first particle PTC1 can include a plurality of primary particles PRP1-PRP3. The third primary particle PRP3 may be provided at the center of the first particle PTC1. The second primary particle PRP2 may be provided on the surface of the first particle PTC1. The first primary particle PRP1 may extend in the radial direction (RD) from the third primary particle PRP3 toward the second primary particle PRP2.

[0089] The crystallite can be the smallest unit in which the lithium composite oxide has one crystal direction. For example, the primary particles PRP1-PRP3 constituting the first particle PTC1 can correspond to the crystallites. The second particle PTC2 described above can be composed of one crystallite or can have a shape in which a plurality of crystallites are aggregated.

[0090] The first primary particle PRP1 can have a rod shape extending in the radial direction RD. The major axis of the first primary particle PRP1 can be substantially parallel to the radial direction RD. Each of the second primary particle PRP2 and the third primary particle PRP3 can have an amorphous shape with a small aspect ratio.

[0091] As an embodiment of the present invention, the third primary particle PRP3 may be omitted. In other words, the first primary particle PRP1 may extend from the center of the first particle PTC1 toward the second primary particle PRP2.

[0092] The average size of the crystal grains or primary particles of the first particle PTC1 can be measured through XRD analysis. The average size of the first primary particle PRP1 can have a first size. The average size of the second primary particle PRP2 can have a second size. The average size of the third primary particle PRP3 can have a third size. The first size can be from 200 nm to 3,000 nm. The second size can be from 100 nm to 1,500 nm. The third size can be from 100 nm to 900 nm. As an example, the first size may be larger than the second size. The first size can be from 1.5 times to 30 times the second size. Or, the first size can be from 1.5 times to 10 times the second size.

[0093] According to an embodiment of the present invention, the first primary particle PRP1 can have a first length LI1 in the radial direction RD. The first length LI1 can correspond to the first size. For example, the first length LI1 can be from 400 nm to 3,000 nm.

[0094] The first primary particle PRP1 can have a first width WI1 in a direction ND intersecting the radial direction RD. For example, the first width WI1 can be from 200 nm to 600 nm. The first width WI1 of the first primary particle PRP1 may gradually increase as it goes in the radial direction RD. In other words, the first width WI1 of the first primary particle PRP1 adjacent to the second primary particle PRP2 may be larger than the first width WI1 of the first primary particle PRP1 adjacent to the third primary particle PRP3.

[0095] The first primary particle PRP1 can have a relatively large aspect ratio (LI1 / WI1). As an example, the aspect ratio (LI1 / WI1) of the first primary particle PRP1 can be from 2 to 15. As an example, the aspect ratio (LI1 / WI1) of the first primary particle PRP1 can be from 5 to 10.

[0096] The first length LI1 of the first primary particle PRP1 adjacent to the second primary particle PRP2 may be greater than the first length LI1 of the first primary particle PRP1 adjacent to the third primary particle PRP3. Among the plurality of first primary particles PRP1, the length of the first primary particle PRP1 adjacent to the center of the first particle PTC1 may be smaller than the length of the first primary particle PRP1 adjacent to the surface of the first particle PTC1.

[0097] According to an embodiment of the present invention, the second primary particle PRP2 can have a second length LI2 in the radial direction RD. The second primary particle PRP2 can have a second width WI2 in a direction ND intersecting the radial direction RD. The second primary particle PRP2 can have a relatively small aspect ratio (LI2 / WI2). The aspect ratio (LI2 / WI2) of the second primary particle PRP2 can be from 0.7 to 3. As an example, the aspect ratio (LI2 / WI2) of the second primary particle PRP2 can be from 1 to 3. Each of the second length LI2 and the second width WI2 can correspond to the second size. For example, each of the second length LI2 and the second width WI2 can be from 100 nm to 1,500 nm.

[0098] According to an embodiment of the present invention, the first particle PTC1 can contain boron (B) as a dopant. Thereby, as shown in FIG. 8, the aspect ratio of the first primary particle PRP1 can be increased. As will be described later, the manufacturing method of the first particle PTC1 can include a first coating, a second coating, and a second firing. Therefore, the second primary particle PRP2 may be provided on the surface of the first particle PTC1. The second primary particle PRP2 having a small aspect ratio may be provided at one end of the first primary particle PRP1. Thereby, the insertion and desorption of lithium ions into the first particle PTC1 can be facilitated.

[0099] The first primary particle PRP1 can include a first side surface SIS1. The first side surface SIS1 can be arranged parallel to the radial direction RD. For example, the first side surface SIS1 can include a (003) plane.

[0100] By including boron (B) as a dopant, the area of the first side SIS1 of the first primary particle PRP1 can be increased. On the contrary, the areas of the (014) plane and the (104) plane of the first primary particle PRP1 can be relatively decreased.

[0101] The a-axis of the crystal structure of the first primary particle PRP1 can be arranged substantially parallel to the radial direction RD. As the area of the (003) plane of the first primary particle PRP1, i.e., the first side SIS1, increases, the aspect ratio (LI1 / WI1) of the first primary particle PRP1 increases, and the orientation of the first primary particle PRP1 can be increased. As an example, the angle formed by the radial direction RD and the a-axis of the first primary particle PRP1 can be from 0° to 5°. The c-axis of the crystal structure of the first primary particle PRP1 can intersect the radial direction RD perpendicularly. As an example, the angle formed by the radial direction RD and the c-axis of the first primary particle PRP1 can be from 80° to 100°.

[0102] As shown in FIG. 7, a particle boundary GRB may be provided between adjacent first primary particles PRP1. The particle boundary GRB can be substantially parallel to the radial direction RD. Metal ions (e.g., lithium ions) and electrolytes can move smoothly through the particle boundary GRB. As a result, the charge-discharge efficiency of the secondary battery including the first particle PTC1 can be improved.

[0103] The second primary particle PRP2 can have a relatively small aspect ratio (LI2 / WI2) and low orientation to the radial direction RD. The a-axis of the crystal structure of the second primary particle PRP2 is not parallel to the radial direction RD and can intersect. As an example, the angle formed by the radial direction RD and the a-axis of the second primary particle PRP2 can be from 10° to 80°. The direction of the a-axis of the second primary particle PRP2 can be random.

[0104] During the charge and discharge process, the second primary particle PRP2 can contract and expand in the c-axis direction. The contraction and expansion directions of the second primary particle PRP2 can be random. According to this embodiment, the second primary particle PRP2 can be selectively provided on the surface of the first particle PTC1. Thereby, even if the second primary particle PRP2 contracts and expands randomly, cracks may not occur inside the first particle PTC1. Through the random contraction and expansion of the second primary particle PRP2, the particle boundary GRB can be exposed at an appropriate level on the surface of the second primary particle PRP2. Thereby, the movement of lithium ions and electrolytes through the particle boundary GRB can be controlled at an appropriate level during the charge and discharge process.

[0105] More specifically, referring to FIG. 9A, a particle boundary GRB can be provided between adjacent first primary particles PRP1. The particle boundary GRB of the first particle PTC1 into which lithium ions are inserted can have a first interval ITV1.

[0106] Referring to FIG. 9B, during charging of the secondary battery, lithium ions can desorb from the first particle PTC1 and the first and second primary particles PRP1, PRP2 can contract. The primary particles can contract in the c-axis direction. Since the first primary particles PRP1 have substantially the same orientation with respect to each other, when the first primary particles PRP1 contract, the width WI1 of each of them can decrease. Due to the contraction of the first primary particles PRP1, the particle boundary GRB can increase to a second interval ITV2.

[0107] Since the second primary particle PRP2 has a random orientation, even if the second primary particle PRP2 contracts, its width WI2 may not change significantly compared to the first width WI1. In other words, when the first particle PTC1 contracts, the change amount of the width WI2 of the second primary particle PRP2 may be smaller than the change amount of the width WI1 of the first primary particle PRP1.

[0108] Therefore, even if a relatively large second interval ITV2 occurs in the particle boundary GRB, the second primary particle PRP2 can appropriately block the particle boundary GRB that has spread in the second interval ITV2. Therefore, it is possible to prevent the electrolyte from excessively penetrating into the particle boundary GRB, and it is possible to prevent side reactions and crack generation inside the first particle PTC1.

[0109] During the charge and discharge process of the lithium secondary battery, due to the insertion and desorption of lithium ions, the primary particles can contract and expand in the c-axis direction. The contraction and expansion of the primary particles can induce cracks inside the secondary particles. Due to the cracks, the electrolyte can flow into the inside of the secondary particles. A problem may occur in that an impurity phase is formed inside the secondary particles due to side reactions of the electrolyte flowing in through the cracks.

[0110] According to an embodiment of the present invention, the a-axis of the first primary particle PRP1 can be parallel to the radial direction RD, and the c-axis can be parallel to the direction ND intersecting the radial direction RD. Thereby, even if the first primary particle PRP1 contracts and expands in the direction ND, the generation of cracks inside the first particle PTC1 can be prevented. In addition, the randomly oriented second primary particles PRP2 can be selectively provided only on the surface of the first particle PTC1. Therefore, even if the second primary particle PRP2 contracts and expands, the generation of cracks inside the first particle PTC1 can be prevented. As a result, the positive electrode active material according to the embodiment of the present invention can improve the charge and discharge capacity and life characteristics of the secondary battery.

[0111] A grain boundary coating layer GCL can be provided on the first side surface SIS1 of the first primary particle PRP1. As an example, the grain boundary coating layer GCL can be provided at the particle boundary GRB. A first coating layer CTL1 may be provided on the second side surface SIS2 of the second primary particle PRP2. The first coating layer CTL1 can be substantially the same as the one described above.

[0112] The grain boundary coating layer GCL can be present inside the first PTC particle PTC1 rather than on the surface of the first PTC particle PTC1. The grain boundary coating layer GCL can be coated along the particle boundaries GRB inside the first PTC particle PTC1. Here, the inside of the first PTC particle PTC1 can mean the entire inside excluding the surface of the first PTC particle PTC1. For example, it can mean the entire inside from about 10 nm depth from the outer surface of the first PTC particle PTC1, or the region from 10 nm depth to about 2 μm depth.

[0113] By further including not only the first coating layer CTL1 but also the grain boundary coating layer GCL, the first PTC particle PTC1 according to the present embodiment has enhanced structural stability and can induce a uniform coating on the surface. By appropriately adjusting the metal content in the first coating layer CTL1, the initial charge-discharge efficiency and life characteristics can be improved without increasing the resistance.

[0114] The grain boundary coating layer GCL can contain, as a metal-containing compound, for example, a cobalt compound and a zirconium compound. The metal-containing compound can include a metal oxide, a metal hydroxide, a metal carbonate, or a combination thereof.

[0115] The grain boundary coating layer GCL can further contain other metal or non-metal elements in addition to cobalt and zirconium. The grain boundary coating layer GCL may further contain lithium, manganese, and / or nickel, etc. For example, the grain boundary coating layer GCL can contain lithium cobalt zirconium oxide.

[0116] The content of cobalt relative to the total amount of transition metals in the grain boundary coating layer GCL can be 20 at% to 50 at%. The content of zirconium relative to the total amount of transition metals in the grain boundary coating layer GCL can be 0.1 at% or less. As one embodiment, since the amount of zirconium in the grain boundary coating layer GCL is very small, it may not be measured.

[0117] The cobalt content in the grain boundary coating layer GCL can be different from the cobalt content in the first coating layer CTL1. As an embodiment, the cobalt content in the grain boundary coating layer GCL may be greater than the cobalt content in the first coating layer CTL1. The zirconium content in the grain boundary coating layer GCL may be less than the zirconium content in the first coating layer CTL1. The Co / Zr in the grain boundary coating layer GCL may be greater than the Co / Zr in the first coating layer CTL1.

[0118] The porosity of the core of the first particle PTC1 may be greater than the porosity of the shell. The core of the first particle PTC1 can be defined up to the region corresponding to half of the radius of the first particle PTC1 from the center of the first particle PTC1. The shell of the first particle PTC1 can be defined as the remaining region surrounding the core.

[0119] The ratio of the porosity of the core to the average porosity of the first particle PTC1 can be from 1.5 to 2.0. The core of the first particle PTC1 can be porous, and the shell of the first particle PTC1 can be dense. The shell of the first particle PTC1 can include not only the first coating layer CTL1 and the grain boundary coating layer GCL, but also the second primary particles PRP2 described with reference to FIGS. 9A and 9B above. Therefore, the shell of the first particle PTC1 can have a dense structure without voids.

[0120] The shell of the first particle PTC1 can contain nickel (Ni) and cobalt (Co). The ratio of nickel (Ni) to the total amount of nickel (Ni) and cobalt (Co) in the shell (Ni / (Ni + Co)) can be from 70 at% to 90 at%. Due to the shell of the first particle PTC1 according to this embodiment having the above contents of nickel (Ni) and cobalt (Co), the porosity can be reduced and it can become dense. The Ni content of the shell of the first particle PTC1 may be smaller than the Ni content of the core of the first particle PTC1. The Co content of the shell of the first particle PTC1 may be larger than the Co content of the core of the first particle PTC1.

[0121] Referring to FIG. 6 again, the second particle PTC2 can include at least one crystal grain. The average size of the crystal grains (e.g., PRP1 - PRP3) of the first particle PTC1 and the average size of the crystal grains of the second particle PTC2 can be measured through XRD analysis. For example, the average size of the crystal grains of the second particle PTC2 can be from 100 nm to 4,000 nm or from 500 nm to 1,500 nm. The average size of the crystal grains of the first particle PTC1 may be smaller than the average size of the crystal grains of the second particle PTC2. The average size of the crystal grains of the second particle PTC2 can be from 1.1 times to 3.5 times the average size of the crystal grains of the first particle PTC1.

[0122] According to an embodiment of the present invention, the second particle PTC2 can be formed by firing using a flux. Thereby, the crystal grains of the second particle PTC2 can be formed with a relatively large size. Therefore, the second particle PTC2 has relatively high durability and can prevent fine cracks inside the particles.

[0123] The aggregate ZAG can be provided in the space between the first and second particles PTC1 and PTC2. The aggregate ZAG can be derived from a coating agent described later. The aggregate ZAG can contain, as a metal-containing compound, for example, a cobalt compound and a zirconium compound. For example, the aggregate ZAG can be a mass formed by aggregating a part of the coating agent that was not coated on the surfaces of the first and second particles PTC1 and PTC2.

[0124] The first particle PTC1 can have the shape of a secondary particle. Fine micro-cracks can be easily formed inside the secondary particle during charge and discharge of the battery. However, the first particle PTC1 according to the embodiment of the present invention can prevent internal cracks through the orientation and arrangement of the primary particles shown in FIGS. 7 and 8. According to the embodiment of the present invention, the second particle PTC2 can have a single-particle shape. The second particle PTC2 can be more durable and denser than the first particle PTC1. Therefore, the second particle PTC2 can prevent the formation of fine cracks inside it. As a result, the stability and capacity maintenance characteristics of the secondary battery according to the present invention can be improved.

[0125] Since the average particle size of the second particle PTC2 is smaller than that of the first particle PTC1, the specific surface area of the second particle PTC2 can be larger than the specific surface area of the first particle PTC1. When the first and second particles PTC1 and PTC2 are applied to the positive electrode 10 in FIG. 1, the second particle PTC2 can come into contact with the electrolyte ELL more than the first particle PTC1. Therefore, more side reactions can occur between the second particle PTC2 and the electrolyte ELL than between the first particle PTC1 and the electrolyte ELL. According to the embodiment of the present invention, the second particle PTC2 can include a second coating layer CTL2 containing Co and Zr. The second coating layer CTL2 can prevent side reactions between the second particle PTC2 and the electrolyte ELL. In other words, the second coating layer CTL2 of the present invention can prevent the deterioration of the second particle PTC2 by the electrolyte ELL.

[0126] FIG. 10 is an enlarged view showing a cross-section of the first particle according to the comparative example of the present invention. Referring to FIG. 10, the first particle PTC1 according to the comparative example can exclude the second primary particles PRP2 on its surface. In other words, the second primary particles PRP2 arranged on the surface (or shell) of the first particle PTC1 can be omitted. One end of the first primary particle PRP1 extending in the radial direction may be exposed. One end of the first primary particle PRP1 extending in the radial direction can constitute the surface of the first particle PTC1.

[0127] As an example, in the manufacturing process of the first particle PTC1 according to the comparative example, the primary coating, secondary coating, and secondary firing described later can be omitted. By omitting the primary coating, secondary coating, and secondary firing, the second primary particles PRP2 may not be formed on the surface of the first particle PTC1.

[0128] FIG. 11A is a cross-sectional view schematically showing the first primary particle in a state where lithium ions are inserted in the first particle of the comparative example. FIG. 11B is a cross-sectional view schematically showing the first primary particle in a state where lithium ions are desorbed in the first particle of the comparative example.

[0129] Referring to FIG. 11A, a particle boundary GRB can be provided between the first primary particles PRP1 adjacent to each other. The particle boundary GRB of the first particle PTC1 into which lithium ions are inserted can have a first interval ITV1. As an example, the particle boundary GRB can be exposed through the surface of the first particle PTC1.

[0130] Referring to FIG. 11B, during charging of the secondary battery, lithium ions can desorb from the first particle PTC1 and the first primary particle PRP1 can contract. Due to the contraction of the first primary particle PRP1, the particle boundary GRB can increase to a second interval ITV2.

[0131] On the one hand, while lithium ions are desorbing, the particle boundary GRB exposed to the outside can become even larger. Through the enlarged particle boundary GRB, the electrolyte can easily penetrate into the interior of the first particle PTC1. Therefore, problems such as side reactions and crack generation can occur inside the first particle PTC1.

[0132] On the other hand, as described with reference to FIGS. 9A and 9B above, the first particle PTC1 according to the embodiment of the present invention can prevent the particle boundary GRB from being excessively exposed even when lithium ions desorb through the second primary particles PRP2 on the surface. The present invention can prevent the generation of impurity phases and crack generation inside the first particle PTC1.

[0133] FIG. 12 is a sequence diagram showing a method for manufacturing a first particle according to an embodiment of the present invention. Referring to FIG. 12, a precursor of the first particle can be prepared. The precursor can contain Ni and Ma of Chemical Formula 1 described above. Ma can be at least one element selected from the group consisting of Co, Al, Mn, Na, Mg, Ca, Y, Ti, Hf, V, Nb, Ta, Cr, Mo, W, Zr, Sr, La, Fe, Cu, Ag, Zn, B, Ga, C, Si, and Sn. For example, Ma can contain Co and Al.

[0134] As one embodiment, the precursor is obtained through a coprecipitation method. For example, the coprecipitation method can include dissolving a transition metal raw material substance in a solvent such as distilled water, and continuously introducing a transition metal salt solution into a reactor together with a chelating agent and a basic aqueous solution to cause precipitation. After the precipitate is recovered in slurry form, the slurry solution is filtered and dried to obtain a precursor that is a metal composite hydroxide or oxide.

[0135] In the present invention, the transition metal raw material substance can contain metal salts of at least one element selected from the group consisting of Ni, Co, Al, Mn, Na, Mg, Ca, Y, Ti, Hf, V, Nb, Ta, Cr, Mo, W, Zr, Sr, La, Fe, Cu, Ag, Zn, B, Ga, C, Si, and Sn. The metal salts can use sulfates, nitrates, acetates, halides, hydroxides, etc., and are not particularly limited as long as they can be dissolved in a solvent. The transition metal raw material substance according to the present embodiment can contain nickel salts, cobalt salts, and aluminum salts. The molar ratio of the transition metal raw material substance can be adjusted and mixed so that the cathode active material has high capacity characteristics. For example, x1 in Chemical Formula 1 can be determined by the molar ratio.

[0136] A precursor, a lithium source, and a dopant source can be mixed in a certain ratio to form a mixture (S100). For example, the precursor and the lithium source can be mixed at a molar ratio of about 1:1. The lithium source is not particularly limited as long as it is a substance generally used in the production of the cathode active material. For example, the lithium source can contain lithium salts such as lithium carbonate, lithium nitrate, lithium hydroxide, or lithium sulfate.

[0137] The dopant source can contain boron (B) in Chemical Formula 1 described above. The dopant source can be mixed at a molar ratio of 0.0003 to 0.2 with respect to the precursor. For example, the dopant source can contain boron oxide and / or boric acid.

[0138] The mixture can be put into a furnace and a primary firing process can be performed at a first temperature (S200). The first temperature can be 500°C to 1,000°C. More specifically, the first temperature can be 700°C to 900°C. The primary firing process can be performed in an oxidizing atmosphere such as air or oxygen. The heat treatment time of the primary firing process can be 5 hours to 30 hours. As another embodiment of the present invention, a preliminary firing can be additionally performed at 150°C to 800°C before the primary firing process.

[0139] The first particle PTC1 can be formed from a mixture containing a precursor, a lithium source, and a dopant source through a first firing process. Through the dopant source and the control of the first firing process, the first particle PTC1 can have a secondary particle shape as shown in FIG. 7. As an embodiment, a grinding process can be performed on the synthesized first particle PTC1. The ground first particle PTC1 can have the first average particle diameter APD1 described with reference to FIG. 6.

[0140] A first coating process can be performed on the first particle PTC1 (S300). As an embodiment, the first coating process can be a wet coating process. The first coating process can include coating cobalt (Co) on the first particle PTC1.

[0141] Specifically, the first particle PTC1 and the first coating raw material can be mixed. The first particle PTC1 and the first coating raw material can be put into a solvent (e.g., distilled water) and mixed. The first coating raw material can be a cobalt compound. For example, the cobalt compound can include cobalt oxide, but is not particularly limited thereto. The first particle PTC1 and the first coating raw material can be uniformly mixed through a stirrer. The first particle PTC1 can be filtered and dried.

[0142] Through the first coating process, not only the first coating layer CTL1 can be formed on the surface of the first particle PTC1, but also the grain boundary coating layer GCL can be formed inside the first particle PTC1. That is, by using the wet coating process, the grain boundary coating layer GCL can be smoothly formed.

[0143] A second coating process can be performed on the dried first particle PTC1 (S400). As an embodiment, the second coating process can be a dry coating process. The second coating process can include coating zirconium (Zr) on the first particle PTC1.

[0144] Specifically, the first particles PTC1 and the second coating raw material substance can be mixed without a solvent. The first particles PTC1 and the second coating raw material substance can be placed in a dry coating machine and stirred and mixed. The second coating raw material substance can be a zirconium compound. For example, the zirconium compound can include zirconia, but is not particularly limited thereto.

[0145] The first particles PTC1 after the secondary coating process is completed can be put into a furnace and a secondary firing process can be performed at a second temperature (S500). The second temperature can be from 150°C to 800°C. The second temperature can be lower than the first temperature of the primary firing process. The secondary firing process can be carried out in an oxidizing atmosphere such as air or oxygen.

[0146] By the secondary firing process, a first coating layer CTL1 can be formed from the cobalt compound and the zirconium compound provided on the first particles PTC1. On the other hand, a grain boundary coating layer GCL can be formed from the cobalt compound provided at the grain boundaries GRB inside the first particles PTC1.

[0147] The content of cobalt in the first coating layer CTL1 may be smaller than the content of cobalt in the grain boundary coating layer GCL. The content of zirconium in the first coating layer CTL1 may be larger than the content of zirconium in the grain boundary coating layer GCL. This is because when the secondary coating process is performed as a dry process, it is difficult for the zirconium compound to be provided at the grain boundaries GRB inside the first particles PTC1.

[0148] The second particles PTC2 can be formed in a manner similar to the first particles PTC1. The precursor of the second particles PTC2 can be formed with a smaller particle size than the precursor of the first particles PTC1. Also, in the primary firing process of the second particles PTC2, the dopant source can be excluded and a flux can be used instead.

[0149] The first particles PTC1 and the second particles PTC2 can be mixed with each other to produce a positive electrode active material according to an embodiment of the present invention. As one embodiment, the first particles PTC1 and the second particles PTC2 can be mixed at a weight ratio of 95:5 to 50:50. The first particles PTC1 and the second particles PTC2 may be mixed at a weight ratio of 5:95 to 50:50. By mixing the first particles PTC1 and the second particles PTC2 having different average particle sizes from each other, a positive electrode active material in a bimodal form can be prepared. As another embodiment, the second particles PTC2 may be omitted.

[0150] The positive electrode active material layer AML1 can be manufactured according to a normal positive electrode manufacturing method except that the positive electrode active material according to the embodiment of the present invention is used. Specifically, the positive electrode active materials PTC1, PTC2, the binder BND, and the conductive material CDM of the present invention can be dissolved or dispersed in a solvent to produce a mixture. The binder BND and the conductive material CDM can be the same as those described in the positive electrode active material layer AML1 of FIG. 6 above. After applying the mixture onto the current collector COL1, the positive electrode 10 can be manufactured by drying and rolling.

[0151] The solvent is a solvent generally used in the art, and can include, for example, at least one selected from dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, water, and combinations thereof.

[0152] As another embodiment, the mixture can be cast onto another support to produce a film, that is, the positive electrode active material layer AML1. The positive electrode 10 can be manufactured by laminating the positive electrode active material layer AML1 onto the current collector COL1.

[0153] Hereinafter, the present invention will be described in more detail through examples. However, these examples are for illustrative purposes of the present invention, and the scope of the present invention is not limited to these examples.

[0154] Example 1: Manufacture of positive electrode active material Production Example 1: Production of Large-Particle Precursors Large-particle precursors were produced using the coprecipitation method. Through the process described below, nickel-based metal hydroxide (Ni 0.90 Co 0.07 Al 0.03 (OH)2) was produced as the large-particle precursor.

[0155] Nickel sulfate (NiSO4·6H2O), cobalt sulfate (CoSO4·7H2O), and aluminum sulfate (Al2(SO4)3·H2O) were dissolved in distilled water as the solvent in a molar ratio of 90:7:3 to prepare a metal raw material mixture as the raw material substances of the nickel-based metal hydroxide. To form a complex compound, an aqueous ammonia (NH4OH) dilution and sodium hydroxide (NaOH) as a precipitant were prepared. Then, the metal raw material mixture, aqueous ammonia, and sodium hydroxide were introduced into the reactor. Sodium hydroxide was introduced to maintain the pH of the mixture in the reactor. The reaction was carried out for about 20 hours while stirring the mixture in the reactor.

[0156] The slurry solution in the reactor was filtered and washed with high-purity distilled water. The washed substance was dried in a hot air oven at 190 °C for 24 hours to obtain large-particle precursors (Ni 0.90 Co 0.07 Al 0.03 (OH)2) powder with a particle size of about 18 μm.

[0157] Production Example 2: Production of Large-Particle Lithium Composite Oxide The large-particle precursor of Production Example 1, anhydrous lithium hydroxide (LiOH), and boric acid (H3BO3) were dry-mixed using a Henschel mixer. Lithium: transition metal: boron were mixed in a molar ratio of about 1:1:0.01. The transition metal is the total of the transition metals contained in the large-particle precursor (Ni + Co + Al). The mixture was heat-treated (i.e., the first firing step) at about 800 °C for 10 hours in an oxygen atmosphere to synthesize first particles as the first lithium composite oxide. The first particles were pulverized with a jet mill at a pressure of 3 bar.

[0158] Cobalt oxide corresponding to 3 mol% with respect to the total transition metal of the first particles was introduced for wet coating (primary coating step). The first particles coated with cobalt were dried at 150 °C for 12 hours. After drying the first particles, zirconium oxide corresponding to 0.1 mol% with respect to the total transition metal of the first particles was introduced for dry coating (secondary coating step). The first particles additionally coated with zirconium were heat-treated at about 700 °C in an oxygen atmosphere for 15 hours (i.e., secondary firing step).

[0159] Example 2: Manufacture of lithium secondary battery 96 g of the cathode active material of Example 1, 2 g of polyvinylidene fluoride, 47 g of N-methylpyrrolidone as a solvent, and 2 g of carbon black as a conductive agent were mixed to produce an active material slurry.

[0160] The active material slurry was coated on an aluminum foil using a doctor blade to produce a thin electrode plate form. After drying the electrode plate at 135 °C for 3 hours or more, a cathode was produced through a rolling and vacuum drying process.

[0161] A 2032 type coin cell was produced using a lithium metal counter electrode as the counter electrode to the cathode. A separator (thickness: about 16 μm) made of a porous polyethylene (PE) film was interposed between the cathode and the lithium metal counter electrode. An electrolyte was injected to fabricate a 2032 type coin cell. As the electrolyte, a solution in which 1.1 M LiPF6 was dissolved in a solvent obtained by mixing ethylene carbonate (EC) and ethyl methyl carbonate EMC at a volume ratio of 3:5 was used.

[0162] Comparative Example 1: Manufacture of positive electrode active material A cathode active material was produced in the same manner as in Embodiment 1, except that the primary coating step, the secondary coating step, and the secondary firing step in Production Example 2 were omitted.

[0163] Evaluation Example 1: Shape analysis (SEM) inside the positive electrode active material After internal cross-section sampling of the positive electrode active material manufactured in Example 1, internal shape analysis was performed by photographing with a scanning electron microscope (SEM). Accordingly, the constituent shape of the primary particles inside the first particle was analyzed.

[0164] The scanning electron microscopes used were the S-4800 from Hitachi and the Magellan 400L from FEI company. The sample cross-section was pre-treated by milling for 1 hour at 6 kV and 320 μA using IM4000PLUS, Hitachi. Then, the scanning electron microscope analysis was performed at 3 - 30 keV.

[0165] The SEM images of the cross-section of the first particle of Example 1 are shown in FIGS. 13A, 13B, and 13C. Referring to FIGS. 13A to 13C, the radial first primary particle PRP1 and the surface second primary particle PRP2 as shown in FIG. 8 above can be confirmed. It can be confirmed that the first primary particle PRP1 has a high orientation in the radial direction RD, and it can be confirmed that the second primary particle PRP2 has a low orientation in the radial direction RD.

[0166] The SEM images of the cross-section of the first particle of Example 1 and the cross-section of the first particle of Comparative Example 1 are shown in FIGS. 14A and 14B, respectively. Referring to FIG. 14A, the radial first primary particle PRP1 and the surface second primary particle PRP2 as shown in FIG. 8 above can be confirmed. Referring to FIG. 14B, only the radial first primary particle PRP1 as shown in FIG. 10 above can be confirmed. That is, it can be confirmed that the second primary particle PRP2 is omitted in the first particle of Comparative Example 1.

[0167] In FIG. 14A, the average aspect ratio of the first primary particle PRP1 shown in the SEM image was measured to be about 8. The average aspect ratio of the second primary particle PRP2 shown in the SEM image was measured to be about 2.

[0168] Evaluation Example 2: Composition ratio and porosity analysis inside the positive electrode active material The content of nickel and cobalt in the shell of the first particles was measured through SEM performed in Evaluation Example 1 and energy dispersive X-ray spectroscopy (EDS) conducted in parallel therewith. The SEM-EDS analysis was performed targeting a depth of 500 nm from the exposed surface on the cross-section obtained by cutting the center of the particles. Also, the porosity of the first particles was measured through SEM image analysis of the particle cross-section. The results are shown in Table 1 below. Images showing the porosity of the first particles of Example 1 and the porosity of the first particles of Comparative Example 1 are shown in FIGS. 15A and 15B, respectively.

[0169]

Table 1

[0170] Referring to Table 1, FIG. 15A, and FIG. 15B, it can be confirmed that the first particles of Comparative Example 1 have a relatively high Ni content in the shell. On the contrary, it can be confirmed that the first particles of Example 1 have a relatively low Ni content in the shell. In other words, the first particles of Example 1 have a relatively high Co content in the shell. It can be confirmed that the first particles of Example 1 have a relatively high porosity in the core, while the porosity of the shell is relatively small. That is, it can be confirmed that the first particles of Example 1 include a porous core and a dense shell. It can be confirmed that the first particles of Comparative Example 1 have a relatively high porosity in the core and also a relatively high porosity in the shell. That is, it can be confirmed that all of the core and the shell of the first particles of Comparative Example 1 are porous. Since the amorphous second primary particles PRP2 described above constitute the shell of the first particles PTC1 of Example 1, the porosity of the shell can be reduced. This can also be confirmed by referring to FIGS. 9A and 9B above.

[0171] Evaluation Example 3: Shell / surface composition ratio and porosity analysis of the positive electrode active material Through the SEM-EDS analysis performed in Evaluation Example 2, an image showing the cobalt element in the first particle of Example 1 is shown in Fig. 16A. Further, an image showing the zirconium element in the first particle of Example 1 through the EDS analysis using a transmission electron microscope (TEM) is shown in Fig. 16B. The TEM-EDS analysis was performed using Titan Cubed G2 60-300 of FEI Company and Spectra 300 of Thermo Fisher Company.

[0172] Referring to Fig. 16A, it can be confirmed that cobalt exists in the form of a coating layer on the surface of the first particle. Further, it can be confirmed that cobalt exists in the form of a grain boundary coating layer at the particle boundaries inside the first particle. Referring to Fig. 16B, it can be confirmed that zirconium exists mainly in the form of a coating layer on the surface except inside the first particle.

[0173] Evaluation Example 4: Coating layer analysis of the positive electrode active material Through the SEM-EDS analysis performed in Evaluation Example 2, the contents of transition metals (Ni, Co, and Al) in the shell and core of the first particle of Example 1 were measured and compared. The results are shown in Figs. 17A to 17C.

[0174] Referring to Figs. 17A to 17C, the Al content in the core of the first particle and the Al content in the shell were generally the same at about 1.5 at%. On the other hand, it can be confirmed that the Ni content in the core of the first particle is higher than the Ni content in the shell. It can be confirmed that the Co content in the core of the first particle is lower than the Co content in the shell. This is because the cobalt coating layer is smoothly formed on the particle surface and the particle boundaries adjacent to the particle surface of the first particle in Example 1, resulting in a relatively increased Co content in the shell. On the other hand, it can be confirmed that it is difficult for the Co coating to reach the core of the first particle.

[0175] Through the SEM-EDS and TEM-EDS analyses performed in Evaluation Example 3, the cobalt and zirconium contents on the surface (i.e., the shell) of the first particle of Example 1 were measured, and the results are shown in Table 2 below.

[0176]

Table 2

[0177] Referring to Table 2, it can be confirmed that the cathode active material of Example 1 of the present invention has a relatively high cobalt content and zirconium content in the surface coating layer. Also, it can be confirmed that the ratio of the cobalt content to zirconium is relatively high.

[0178] Evaluation Example 5: HR-TEM analysis of the surface of the positive electrode active material For the first particles of Example 1 and the first particles of Comparative Example 1, the thickness of the surface disordered layer was measured with a high-resolution transmission electron microscope (HR-TEM). The results are shown in FIGS. 18A and 18B, respectively.

[0179] Referring to FIG. 18B, for the first particles of Comparative Example 1, it can be confirmed that the thickness of the surface disordered layer is relatively thick, ranging from 1.91 nm to 5.28 nm. Referring to FIG. 18A, for the first particles of Example 1, it can be confirmed that the thickness of the surface disordered layer is relatively thin, ranging from 0.89 nm to 3.71 nm. In other words, the first particles of Example 1 have relatively fewer surface defects, and thus the performance and lifespan of the active material can be improved.

[0180] Evaluation Example 6: XRD analysis of the positive electrode active material XRD analysis was performed on the cathode active material manufactured in Example 1, and the results are shown in FIG. 19.

[0181] Referring to Fig. 19, the ratio of the main peak intensity of the (003) plane to the secondary peak intensity of the (104) plane (I(003) / I(104)) and the full width at half maximum (FWHM) of the peak for the (003) plane were determined on the XRD spectrum. The crystal grain size was calculated using the full width at half maximum. It was confirmed that the first particles of Example 1 had a crystal grain size of 85.0 nm. It was confirmed that I(003) / I(104) of Example 1 was relatively large, and thus it was possible to confirm that the orientation of the (003) plane increased.

[0182] As a result, the positive electrode active material of Example 1 has high structural stability, and thus the life characteristics can be improved by the stable insertion and desorption of lithium ions.

[0183] Evaluation Example 7: Measurement of the angle between the a-axis and the radial direction of the primary particles constituting the positive electrode active material The core and shell of the first particles of Example 1 were measured with a high-resolution transmission electron microscope (HR-TEM), and the results are shown in Figs. 20 and 21, respectively. Referring to Fig. 20, the first primary particles constituting the core of the first particles of Example 1 can be confirmed. The angle between the a-axis of the first primary particles and the radial direction was measured at about 0°. In other words, it was possible to confirm that the a-axis of the first primary particles and the radial direction were substantially parallel to each other.

[0184] Referring to Fig. 21, the angle between the a-axis of the second primary particles constituting the shell of the first particles of Example 1 and the radial direction varied diversely. For example, the angle between the a-axis and the radial direction of any one of the second primary particles was measured at about 21°, while the angle between the a-axis and the radial direction of another one of the second primary particles was measured at about 42°. In other words, the direction of the a-axis of the second primary particles was random.

[0185] Evaluation Example 8: Life characteristics of the lithium secondary battery The capacity retention rate of the coin cell of Example 2 was evaluated as follows using a charge-discharge machine (manufacturer: TOYO, model: TOYO-3100).

[0186] For the evaluation of the initial capacity (1st charge capacity, 1st discharge capacity) and initial efficiency characteristics, the coin cells assembled were charged at a constant current of 0.2C until reaching 4.3V at 25°C, and then charged at a constant voltage until reaching a current of 0.05C. After the charging was completed, the cells were allowed to rest for about 10 minutes and then discharged at a constant current of 0.2C until the voltage reached 3V. For the evaluation of the capacity retention rate by repeated charge and discharge, the coin cells were charged at a constant current of 1C until reaching 4.4V at 45°C, and then charged at a constant voltage until reaching a current of 0.05C. After the charging was completed, the cells were allowed to rest for about 10 minutes and then discharged at a constant current of 1C until the voltage reached 3V. This was repeated 60 times for evaluation.

[0187] Coin cells were manufactured in the same manner as in Example 2 using the positive electrode active material of Comparative Example 1. The coin cells for Comparative Example 1 were evaluated in the same manner as above. The results are shown in Table 3 below.

[0188]

Table 3

[0189] Referring to Table 3, it can be confirmed that the capacity retention rate (i.e., life characteristics) of Comparative Example 1 is significantly lower than that of Example 1. In the case of Comparative Example 1, it is judged that due to the non-uniform coating layer and the form of the first particles as shown in FIG. 10, when the life is long, the deterioration of the particles is accelerated and the performance is rapidly reduced. In the case of Example 1, it can be confirmed that due to the particle form and the uniform coating layer as shown in FIG. 7, the resistance is reduced, the stability of the particles is improved, and the high-temperature long-life characteristics are improved.

[0190] Although the preferred embodiments of the present invention have been described above, the present invention is not limited thereto, and various modifications can be made within the scope of the claims, the detailed description of the invention, and the attached drawings, and it is natural that these also belong to the scope of the present invention.

Explanation of Reference Signs

[0191] AML1 positive electrode active material layer AML2 negative electrode active material layer APD1 first average particle size APD2 second average particle size BND binder CDM conductive material COL1 current collector COL2 current collector CTL1 first coating layer CTL2 second coating layer GCL grain boundary coating layer GRB particle boundary PTC1 first particle PRP1, PRP2, PRP3 primary particles PTC2 second particle ZAG aggregate

Claims

1. comprising first particles containing a first lithium composite oxide, wherein the first lithium composite oxide is represented by the following Chemical Formula 1, [Chemical Formula 1] Li a1 Ni x1 Ma 1-x1 O b1 (in Chemical Formula 1, a1 is from 0.5 to 1.5, x1 is from 0.6 to 0.99, b1 is from 1.8 to 2.2, 1 - x1 is from 0.01 to 0.4, Ma contains at least one element selected from the group consisting of Co, Al, Mn, Na, Mg, Ca, Y, Ti, Hf, V, Nb, Ta, Cr, Mo, W, Zr, Sr, La, Fe, Cu, Ag, Zn, Ga, C, Si, and Sn) the first particles include first primary particles extending in a radial direction from the center thereof toward the surface, and second primary particles provided on the surface, the aspect ratio of the first primary particles is from 2 to 15, the aspect ratio of the second primary particles is from 0.7 to 3, a positive electrode active material.

2. The positive electrode active material according to Claim 1, wherein an angle formed by the a-axis of the first primary particles and the radial direction is from 0° to 5°.

3. The positive electrode active material according to Claim 1, wherein the first primary particles include a (003) plane extending in the radial direction.

4. The first primary particles have a width in a direction intersecting the radial direction, and the width of the first primary particles increases as going in the radial direction, the positive electrode active material according to Claim 1.

5. The positive electrode active material according to Claim 1, wherein an angle formed by the a-axis of the second primary particles and the radial direction is from 10° to 80°.

6. The positive electrode active material according to Claim 1, wherein the second primary particles are provided at one end of the first primary particles.

7. the first particles further include third primary particles provided at the center thereof, the first primary particles extend from the third primary particles toward the second primary particles, and the aspect ratio of the third primary particles is from 0.7 to 3, the positive electrode active material according to Claim 1.

8. the first particles include a core and a shell, the content of Ni in the core is greater than the content of Ni in the shell, the content of Co in the shell is greater than the content of Co in the core, and the ratio of Ni to the total amount of Ni and Co in the shell (Ni / (Ni + Co)) is from 70 at% to 90 at%, the positive electrode active material according to Claim 1.

9. the first particles further include a first coating layer on the surface, and the first coating layer contains cobalt (Co) and zirconium (Zr), The content of cobalt with respect to the total amount of transition metals in the first coating layer is from 20 at% to 50 at%, The content of zirconium with respect to the total amount of transition metals in the first coating layer is from 0.001 at% to 1 at% in the positive electrode active material according to claim 1.

10. The first particles include a core and a shell, The ratio of the porosity of the core to the average porosity of the first particles is from 1.5 to 2.0 in the positive electrode active material according to claim 1.

11. The first particles have a first average particle size, The first average particle size is from 6.0 μm to 20.0 μm in the positive electrode active material according to claim 1.

12. Further comprising second particles containing a second lithium composite oxide, The first average particle size of the first particles is larger than the second average particle size of the second particles, The second lithium composite oxide is represented by the following Chemical Formula 2, [Chemical Formula 2] Li a2 Ni x2 Mb 1-x2 Fl w2 O b2 (In the Chemical Formula 2, a2 is from 0.5 to 1.5, x2 is from 0.6 to 0.99, b2 is from 1.8 to 2.2, 1 - x2 is from 0.01 to 0.4, w2 is from 0.0005 to 0.01, Mb includes at least one element selected from the group consisting of Co, Al, Mn, Na, Mg, Ca, Y, Ti, Hf, V, Nb, Ta, Cr, Mo, W, Zr, Sr, La, Fe, Cu, Ag, Zn, B, Ga, C, Si, and Sn, Fl includes at least one element selected from the group consisting of Zr, Sr, Y, La, Mo, Ce, Nb, and S) The positive electrode active material according to claim 1.

13. The size of the crystal grains of the second particles is larger than the average size of the first and second primary particles in the positive electrode active material according to claim 12.

14. Including first particles containing a first lithium composite oxide, The first lithium composite oxide is represented by the following Chemical Formula 1, [Chemical Formula 1] Li a1 Ni x1 Ma 1-x1 O b1 (In the Chemical Formula 1, a1 is from 0.5 to 1.5, x1 is from 0.6 to 0.99, b1 is from 1.8 to 2.2, 1 - x1 is from 0.01 to 0.4, Ma includes at least one element selected from the group consisting of Co, Al, Mn, Na, Mg, Ca, Y, Ti, Hf, V, Nb, Ta, Cr, Mo, W, Zr, Sr, La, Fe, Cu, Ag, Zn, Ga, C, Si, and Sn) The first particles include first primary particles extending radially from the center thereof toward the surface and second primary particles provided on the surface, The angle formed by the a-axis of the first primary particle and the radial direction is 0° to 5°. The angle formed by the a-axis of the second primary particle and the radial direction is 10° to 80°, a positive electrode active material.

15. The first particle further includes a first coating layer on the surface and a grain boundary coating layer on the side surface of the first primary particle. Each of the first coating layer and the grain boundary coating layer contains cobalt (Co) and zirconium (Zr). The Co / Zr of the grain boundary coating layer is greater than the Co / Zr of the first coating layer. The positive electrode active material according to claim 14.

16. The length of the first primary particle in the radial direction is 400 nm to 3,000 nm. The positive electrode active material according to claim 14.

17. The first particle has a first average particle size. The first average particle size is 6.0 μm to 20.0 μm. The positive electrode active material according to claim 14.

18. The first particle includes a core and a shell. The Ni content of the core is greater than the Ni content of the shell. The Co content of the shell is greater than the Co content of the core. The positive electrode active material according to claim 14.

19. The first particle includes a core and a shell. The ratio of the porosity of the core to the average porosity of the first particle is 1.5 to 2.

0. The positive electrode active material according to claim 14.

20. A lithium secondary battery including the positive electrode active material according to claim 1 or claim 14.

Images