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

Abstract

To provide a positive electrode active material and a method for manufacturing the same, as well as a positive electrode containing the same and a lithium secondary battery, which ensure economic efficiency, high capacity, and long life characteristics, and improve high voltage and high temperature characteristics. [Solution] In one embodiment, a method for producing a positive electrode active material is provided, comprising the steps of: (i) preparing a coating solution having a pH of 12.5 to 14 by adding an aluminum raw material and sodium hydroxide to an aqueous solvent; (ii) preparing a first mixed solution by adding core particles containing a lithium nickel-based composite oxide to the coating solution; (iii) preparing a second mixed solution by adding a cobalt raw material to the first mixed solution; and (iv) drying and heat-treating the second mixed solution to obtain a positive electrode active material.

Description

[Technical Field]

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

[0002] Lithium-ion batteries, which offer high energy density while being easily portable, are primarily used as power sources for mobile information terminals such as mobile phones, laptops, and smartphones. Recently, research has been actively conducted on using high-energy-density lithium-ion batteries as power sources or energy storage sources for hybrid and electric vehicles.

[0003] To realize lithium secondary batteries suitable for such applications, various cathode active materials are being investigated. Among these, lithium nickel-based oxides, lithium nickel manganese cobalt composite oxides, lithium nickel cobalt aluminum composite oxides, and lithium cobalt oxides are mainly used as cathode active materials. In recent years, with the rapid increase in demand for large, high-capacity, or high-energy-density lithium secondary batteries, there is a need to develop cathode active materials that simultaneously improve stability and performance. [Overview of the project] [Problems that the invention aims to solve]

[0004] The present invention provides a positive electrode active material and a method for manufacturing the same, which ensure economic efficiency, high capacity, and long life characteristics, and improve high voltage and high temperature characteristics, as well as a positive electrode containing the same and a lithium secondary battery. [Means for solving the problem]

[0005] In one embodiment, a method for producing a positive electrode active material is provided, comprising the steps of: (i) preparing a coating solution with a pH of 12.5 to 14 by adding an aluminum raw material and sodium hydroxide to an aqueous solvent; (ii) preparing a first mixed solution by adding core particles containing a lithium nickel-based composite oxide to the coating solution; (iii) preparing a second mixed solution by adding a cobalt raw material to the first mixed solution; and (iv) drying and heat-treating the second mixed solution to obtain a positive electrode active material.

[0006] In another embodiment, a positive electrode active material is provided comprising core particles containing a lithium nickel composite oxide; and a coating layer located on the surface of the core particles and containing aluminum and cobalt, wherein the positive electrode active material contains sodium, and the sodium content is 0.08% to 0.2% by weight relative to 100% by weight of the total metal excluding lithium in the lithium nickel composite oxide.

[0007] In another embodiment, the present invention includes a current collector; and a positive electrode active material layer located on the current collector; wherein the positive electrode active material layer provides a positive electrode containing the positive electrode active material.

[0008] In another embodiment, a lithium secondary battery comprising the positive electrode; negative electrode; and electrolyte is provided. [Effects of the Invention]

[0009] One embodiment of the positive electrode active material maximizes capacity while minimizing production costs, ensures long lifespan, and improves high-voltage and high-temperature characteristics. A lithium secondary battery to which this positive electrode active material is applied can exhibit high initial charge / discharge capacity and efficiency even under high-voltage driving conditions, and can achieve long lifespan characteristics under high-voltage and high-temperature conditions. [Brief explanation of the drawing]

[0010] [Figure 1] This is a schematic diagram showing a lithium secondary battery according to one embodiment. [Figure 2] This is a drawing schematically showing a lithium secondary battery according to an embodiment. [Figure 3] This is a drawing schematically showing a lithium secondary battery according to an embodiment. [Figure 4] This is a drawing schematically showing a lithium secondary battery according to an embodiment.

Embodiments for Carrying Out the Invention

[0011] Hereinafter, specific embodiments will be described in detail so that those having ordinary knowledge in this technical field can easily implement them. However, the present invention can be implemented in various different forms and is not limited to the embodiments described herein.

[0012] The terms used herein are for the purpose of describing exemplary embodiments only and are not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly indicates a different meaning.

[0013] Here, "these combinations" means a mixture, laminate, composite, copolymer, alloy, blend, reaction product, etc. of components.

[0014] The terms such as "comprising", "including" or "having" herein are intended to specify the presence of implemented features, numbers, steps, components, or combinations thereof, and it should be understood that they do not preclude the possibility of the presence or addition of one or more other features, numbers, steps, components, or combinations thereof in advance.

[0015] In the drawings, for the purpose of clearly showing various layers and regions, the thickness is enlarged for display, and the same drawing reference numerals are given to similar parts throughout the specification. When a part such as a layer, film, region, plate, etc. is "on" or "above" another part, this includes not only the case where it is "directly above" the other part but also the case where there is another part in between. Conversely, when a part is "directly above" another part, it means that there is no other part in between.

[0016] Here, "layer" includes not only the shapes formed on the entire surface when observed in a plan view, but also the shapes formed on some of the surfaces.

[0017] The average particle size can be measured by methods known to those skilled in the art, for example, by a particle size analyzer, or by transmission electron microscope images or scanning electron microscope images. Alternatively, it can be measured using dynamic light scattering, and after performing data analysis to count the number of particles for each particle size range, the average particle size value can be calculated from there. Unless otherwise defined, the average particle size is the diameter (D) of the particle with a cumulative volume of 50% in the particle size distribution. 50 ) can mean. Also, unless otherwise defined, the average particle size is obtained by measuring the size (diameter or length of the long axis) of more than 20 random particles in a scanning electron microscope image to obtain a particle size distribution, and the diameter (D) of the particle whose cumulative volume is 50% in the particle size distribution. 50 ) may be used as the average particle size.

[0018] Here, "or" is not interpreted as having an exclusive meaning; for example, "A or B" is interpreted as including A, B, A+B, etc.

[0019] Here, "metal" is interpreted as a concept that includes general metals, transition metals, and semimetals.

[0020] Method for manufacturing positive electrode active material In one embodiment, a method for producing a positive electrode active material is provided, comprising the steps of: (i) preparing a coating solution with a pH of 12.5 to 14 by adding an aluminum raw material and sodium hydroxide to an aqueous solvent; (ii) preparing a first mixed solution by adding core particles containing a lithium nickel-based composite oxide to the coating solution; (iii) preparing a second mixed solution by adding a cobalt raw material to the first mixed solution; and (iv) drying and heat-treating the second mixed solution to obtain a positive electrode active material.

[0021] Conventional positive electrode active materials degrade when washed with low-pH washing water during the washing and coating steps, leading to a decrease in the efficiency of lithium secondary batteries. Therefore, by adjusting the pH of the washing water during washing, the outflow of lithium and oxygen from the positive electrode active material is minimized to prevent degradation. This allows for the formation of a very thin and uniform coating layer on the surface of the positive electrode active material, improving the efficiency and stability of lithium secondary batteries.

[0022] One embodiment is a salt-dissolution wet coating method in which a coating solution is first prepared by adding aluminum raw material and sodium hydroxide to an aqueous solvent, a positive electrode active material containing lithium nickel-based composite oxide is added and mixed thereto, a cobalt raw material is mixed in, and then the coating layer is formed by drying and heat treatment.

[0023] The aqueous solvent may include distilled water, an alcoholic solvent, or a combination thereof. The aluminum raw material may, for example, be aluminum sulfate. Aluminum sulfate is an optimal raw material for forming a uniform aluminum coating layer on a lithium nickel composite oxide. The aluminum raw material is a raw material for forming an aluminum coating layer, and the aluminum content in the aluminum raw material relative to 100 mol% of the total metal excluding lithium in the lithium nickel composite oxide may be 0.1 mol% to 1.0 mol%, for example, 0.1 mol% to 0.9 mol%, 0.3 mol% to 0.7 mol%, 0.2 mol% to 0.5 mol%, or 0.1 mol% to 0.3 mol%. By introducing the aluminum raw material within the above range, a thin coating layer with a uniform thickness on the level of several to several hundred nanometers can be formed, which can reduce the amount of gas generated by lithium secondary batteries under high voltage or high temperature operating conditions and improve high capacity and long life characteristics.

[0024] Sodium hydroxide is a raw material used to adjust the pH of the coating solution. The sodium content in sodium hydroxide relative to 100 mol% of the total metal excluding lithium in the lithium nickel composite oxide may be between 2.0 mol% and 8.0 mol%, for example, 3.0 mol% to 8.0 mol%, 4.0 mol% to 8.0 mol%, 4.0 mol% to 6.0 mol%, 5.0 mol% to 8.0 mol%, or 5.5 mol% to 7.0 mol%. By adding sodium hydroxide so that the sodium content falls within the above range, the outflow of lithium and oxygen from the positive electrode active material is minimized, preventing degradation. This allows for the formation of a very thin and uniform coating layer on the surface of the positive electrode active material, improving the efficiency and stability of the lithium secondary battery.

[0025] The coating solution prepared by adding aluminum raw material to the aqueous solvent may have a pH of 1.5 to 3.5, but a coating solution can also be prepared by adding sodium hydroxide, in which case the pH of the coating solution will be 12.5 to 14, for example, 13.0 to 13.5, 12.8 to 13.9, or 12.8 to 13.4. When the pH of the coating solution falls within the above range, the outflow of lithium and oxygen from the positive electrode active material is minimized, preventing degradation, and thereby a very thin and uniform coating layer can be formed on the surface of the positive electrode active material, improving the efficiency and stability of the lithium secondary battery.

[0026] The step of preparing the first mixed solution by adding core particles containing lithium nickel-based composite oxide to the coating solution can be carried out for 5 to 80 minutes, for example, 5 to 60 minutes, or 5 to 40 minutes. At this time, the pH of the first mixed solution may be 10 to 14, for example, 10 to 13.5, or 10 to 13. When the pH of the first mixed solution falls within this range, it is advantageous for forming a coating layer of uniform thickness.

[0027] The aforementioned lithium nickel-based composite oxide is represented by the following chemical formula 1. [Chemical formula 1] Li a1 Nix1 M 1 y1 M 2 z1 O 2-b1 X b1

[0028] In Chemical Formula 1, 0.9 ≤ a1 ≤ 1.8, 0.3 ≤ x1 ≤ 1, 0 ≤ y1 ≤ 0.7, 0 ≤ z1 ≤ 0.7, 0.9 ≤ x1 + y1 + z1 ≤ 1.1, and 0 ≤ b1 ≤ 0.1, and M 1 and M 2 are each independently one or more elements selected from the group consisting of Al, B, Ba, Ca, Ce, Co, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sn, Sr, Ti, V, W, Y, Zn, and Zr, and X is one or more elements selected from the group consisting of F, P, and S. At this time, M 1 and M 2 may be different elements from each other.

[0029] In Chemical Formula 1, 0.6 ≤ x1 ≤ 1, 0 ≤ y1 ≤ 0.4, and 0 ≤ z1 ≤ 0.4 may also be satisfied, or 0.8 ≤ x1 ≤ 1, 0 ≤ y1 ≤ 0.2, and 0 ≤ z1 ≤ 0.2 may also be satisfied, or 0.9 ≤ x1 < 1, 0 < y1 ≤ 0.1, and 0 ≤ z1 ≤ 0.1 may also be satisfied.

[0030] As an example, a high-nickel cathode active material in which the content of nickel relative to 100 mol% of the metal excluding lithium from the lithium nickel-based composite oxide is 80 mol% or more, 85 mol% or more, 90 mol% or more, 91 mol% or more, or 94 mol% or more and 99 mol% or less may be used. The high-nickel cathode active material can achieve a high capacity and can be applied to a high-capacity and high-density lithium secondary battery.

[0031] The core particles containing the lithium nickel-based composite oxide may be in particle form, and the particles may be in secondary particle form formed by the aggregation of a plurality of primary particles, single particles, or a combination thereof. The secondary particles and single particles may be spherical, ellipsoidal, polyhedronal, or irregular in shape, and the primary particles constituting the secondary particles may be spherical, ellipsoidal, plate-shaped, or a combination thereof.

[0032] The average particle size (D) of the core particles 50 The particle size (D) may be 10 μm to 25 μm, for example, 11 μm to 20 μm, or 12 μm to 18 μm. Here, the average particle size (D) 50 The particle size may be obtained by randomly measuring the size (diameter or length of the major axis) of more than 20 particles from scanning electron microscope images of the positive electrode active material to obtain a particle size distribution, and then taking the diameter of the particle with a cumulative volume of 50% from the particle size distribution as the average particle size.

[0033] The cobalt raw material may, for example, be cobalt sulfate. Cobalt sulfate is an optimal raw material for forming a uniform cobalt coating layer on a lithium nickel composite oxide. The cobalt raw material is a raw material for forming the coating layer, and the cobalt content in the cobalt raw material relative to 100 mol% of the total metal excluding lithium in the lithium nickel composite oxide may be 1.0 mol% to 5.0 mol%, for example, 1.5 mol% to 4.5 mol%, 2.0 mol% to 4.0 mol%, 2.0 mol% to 3.0 mol%, or 2.5 mol% to 3.5 mol%. By adding the cobalt raw material within the above range, a thin coating layer with a uniform thickness on the level of several to several hundred nanometers can be formed, reducing the amount of gas generated in lithium secondary batteries under high voltage or high temperature operating conditions, and improving high capacity and long life characteristics.

[0034] In the sodium hydroxide and cobalt raw materials added to the aqueous solvent, the molar ratio of the sodium content in the sodium hydroxide to the cobalt content in the cobalt raw material may be 1.5:1 to 3:1, for example, 1.5:1 to 2.5:1, 1.5:1 to 2:1, or 2:1 to 3:1. When the molar ratio of the sodium content in the sodium hydroxide to the cobalt content in the cobalt raw material falls within the above range, the outflow of lithium and oxygen from the positive electrode active material is minimized, preventing degradation. This allows for the formation of a very thin and uniform coating layer on the surface of the positive electrode active material, improving the efficiency and stability of the lithium secondary battery.

[0035] The preparation of the second mixed solution by adding the cobalt raw material to the first mixed solution can be carried out over a period of 5 to 80 minutes, for example, 5 to 60 minutes, or 5 to 40 minutes. The pH of the second mixed solution after stirring may be 9 to 13, for example, 9 to 12, or 9 to 11. When the pH of the second mixed solution falls within this range, it is advantageous for forming a coating layer of uniform thickness.

[0036] The step of drying the second mixed solution can be understood as a step of removing the solvent, and can be carried out at, for example, 40°C to 240°C, 100°C to 220°C, or 150°C to 200°C.

[0037] The heat treatment step after the drying step can be understood as a step to form a coating layer, and can be carried out, for example, in an oxygen atmosphere at a temperature range of 700°C to 850°C, 750°C to 840°C, or 800°C to 830°C for 2 to 20 hours, or 3 to 10 hours.

[0038] positive electrode active material In one embodiment, a positive electrode active material is provided comprising core particles containing a lithium nickel composite oxide; and a coating layer located on the surface of the core particles and containing aluminum and cobalt, wherein the positive electrode active material contains sodium, and the sodium content relative to 100% by weight of the total metal excluding lithium in the lithium nickel composite oxide is 0.08% by weight to 0.2% by weight.

[0039] core particles In one embodiment, the positive electrode active material includes core particles containing a lithium nickel-based composite oxide, and contains sodium, with the sodium content being 0.08% to 0.2% by weight relative to 100% by weight of the total metal excluding lithium in the lithium nickel-based composite oxide.

[0040] As previously mentioned, lithium nickel-based composite oxides are well-documented, so a detailed explanation will be omitted.

[0041] The positive electrode active material contains sodium, and the sodium content relative to 100% by weight of the total metal excluding lithium in the lithium nickel composite oxide is 0.08% to 0.2% by weight, for example, 0.1% to 0.2% by weight, 0.1% to 0.18% by weight, 0.082% to 0.173% by weight, or 0.1% to 0.15% by weight. When the core particles contain sodium within the above range, the outflow of lithium and oxygen from the positive electrode active material is minimized, preventing degradation. This allows for the formation of a very thin and uniform coating layer on the surface of the positive electrode active material, improving the efficiency and stability of the lithium secondary battery.

[0042] coating layer In one embodiment, the positive electrode active material further includes a coating layer located on the surface of the core particles and containing aluminum and cobalt. The aluminum content in the coating layer relative to 100 at% of the total metal excluding lithium in the positive electrode active material may be 0.1 at% to 1.0 at%, for example, 0.12 at% to 0.9 at%, 0.14 at% to 0.8 at%, 0.16 at% to 0.7 at%, 0.18 at% to 0.6 at%, or 0.2 at% to 0.5 at%. The cobalt content in the coating layer relative to 100 at% of the total metal excluding lithium in the positive electrode active material may be 1.0 to 4.0 at%, for example, 1.2 at% to 3.8 at%, 1.4 at% to 3.6 at%, 1.6 at% to 3.4 at%, 1.8 at% to 3.2 at%, or 2.0 at% to 3.0 at%.

[0043] The aluminum content in the coating layer refers only to the aluminum contained in the coating layer, and is independent of the aluminum contained in the core particles. Similarly, the cobalt content in the coating layer refers only to the cobalt contained in the coating layer, and is independent of the cobalt contained in the core particles. When the aluminum and cobalt content in the coating layer meets the aforementioned ranges, it is possible to form a uniform, thin coating layer, preventing an increase in the resistance of the positive electrode active material, effectively suppressing side reactions with the electrolyte, and improving the lifespan characteristics of lithium secondary batteries under high voltage and high temperature conditions. For example, if the aluminum or cobalt content in the coating layer is too high, a uniform coating layer may not be formed, or the resistance may increase, reducing the charge-discharge efficiency and lifespan characteristics. Conversely, if the aluminum or cobalt content in the coating layer is too low, a coating layer of appropriate thickness may not be formed, reducing the effect of suppressing side reactions with the electrolyte. The aluminum and cobalt content in the coating layer can be measured, for example, by scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) or X-ray photoelectron spectroscopy (XPS) on the surface of the positive electrode active material.

[0044] In one embodiment, the coating layer may be, for example, a film that continuously encloses the surface of the core particles, or it may be a shell that encloses the entire surface of the core particles. This is distinct from a structure in which only a part of the surface of the core particles is partially coated. According to one embodiment, the coating layer can be formed in a form that completely encloses the surface of the core particles and has a very thin and uniform thickness. As a result, the positive electrode active material does not experience increased resistance or decreased capacity, its structural stability is improved, side reactions with the electrolyte are effectively suppressed, and gas generation under high voltage and high temperature conditions is reduced, enabling long-life characteristics.

[0045] In one embodiment, the thickness of the coating layer may be 30 nm to 500 nm, for example, 30 nm to 450 nm, 30 nm to 400 nm, 30 nm to 350 nm, 30 nm to 300 nm, 30 nm to 250 nm, 30 nm to 200 nm, 30 nm to 150 nm, 50 nm to 500 nm, 80 nm to 500 nm, or 100 nm to 500 nm. When the coating layer satisfies the aforementioned thickness range, the coating does not increase resistance or decrease capacitance, improves the structural stability of the positive electrode active material, and effectively suppresses side reactions with the electrolyte. The thickness of the coating layer may be measured by, for example, TOF-SIMS, XPS, or EDS analysis, and the thickness range of the coating layer may be measured by TEM-EDS line profile.

[0046] One embodiment of the coating layer is characterized by being thin, at the level of several to several hundred nanometers, and having a uniform thickness. For example, the thickness deviation of the coating layer within a single positive electrode active material particle may be 20% or less, 18% or less, or 15% or less. Here, the thickness deviation of the coating layer refers to the thickness of the coating layer within a single positive electrode active material particle. The thickness deviation of the coating layer can be, for example, calculated by measuring the thickness of more than 10 points from an electron microscope image of the cross-section of a single positive electrode active material particle, calculating the arithmetic mean, dividing the absolute value of the difference between one data point and the arithmetic mean by the arithmetic mean, and then multiplying by 100. When the thickness deviation or standard deviation of the coating layer satisfies the above range, it means that a coating layer of uniform thickness is formed in a good form on the surface of the positive electrode active material particle, thereby improving the structural stability of the positive electrode active material, effectively suppressing side reactions with the electrolyte, and minimizing resistance increase and capacity decrease due to the coating.

[0047] On the other hand, the coating layer may further contain nickel in addition to aluminum and cobalt. The nickel may be present in the core particles and may have entered during the coating layer formation process, and its content is not particularly limited. In one embodiment, the coating layer selectively contains nickel while containing aluminum and cobalt, and is formed to a thin and uniform thickness, which can improve the high-voltage characteristics of the positive electrode active material and enhance its lifespan.

[0048] Furthermore, the coating layer may contain sulfur in addition to aluminum. The sulfur may be introduced during the process of adding aluminum sulfate or cobalt sulfate to the aluminum raw material used to form the aluminum coating layer, and its content is not particularly limited. One embodiment of the coating layer selectively contains sulfur while containing aluminum and cobalt, which can improve the high-voltage characteristics of the positive electrode active material and extend its lifespan.

[0049] positive electrode In one embodiment, the system includes a current collector and a positive electrode active material layer located on the current collector, wherein the positive electrode active material layer provides a positive electrode containing the aforementioned positive electrode active material. The positive electrode active material layer may further contain other types of positive electrode active materials in addition to the aforementioned positive electrode active material. The positive electrode active material layer may also selectively further contain a binder, a conductive material, or a combination thereof.

[0050] binder The binder plays a role in ensuring that the positive electrode active material particles adhere well to each other and that the positive electrode active material adheres well to the current collector. Typical examples of binders include, but are not limited to, polyvinyl alcohol, carboxymethylcellulose, hydroxypropylcellulose, diacetylcellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, epoxy resin, (meth)acrylic resin, polyester resin, and nylon.

[0051] conductive material Conductive materials are used to impart conductivity to electrodes, and any electronically conductive material that does not undergo chemical changes can be used in the battery that is constructed from them. Examples of conductive materials include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjenblack, carbon fibers, carbon nanofibers, and carbon nanotubes; metallic materials containing copper, nickel, aluminum, silver, etc., in the form of metal powders or metal fibers; conductive polymers such as polyphenylene derivatives; or mixtures thereof.

[0052] The content of the binder and conductive material may be 0.5% to 5% by weight, respectively, based on 100% by weight of the positive electrode active material layer.

[0053] Al foil can be used as the current collector, but it is not limited to this.

[0054] Lithium-ion battery In one embodiment, a lithium secondary battery is provided that includes the positive electrode, negative electrode, and electrolyte described above. As an example, the lithium secondary battery may include a positive electrode, a negative electrode, a separator located between the positive electrode and the negative electrode, and an electrolyte.

[0055] Lithium secondary batteries can be classified into cylindrical, prismatic, pouch-type, coin-type, and other types depending on their form. Figures 1 to 4 are schematic diagrams showing a lithium secondary battery according to one embodiment, with Figure 1 being cylindrical, Figure 2 being prismatic, and Figures 3 and 4 being pouch-type batteries. Referring to Figures 1 to 4, the lithium secondary battery 100 may 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, negative electrode 20, and separator 30 are impregnated with an electrolyte (not shown). The lithium secondary battery 100 may include a sealing member 60 that seals the case 50, as shown in Figure 1. Also, in Figure 2, the lithium secondary battery 100 may include a positive electrode lead tab 11 and a positive electrode terminal 12, a negative electrode lead tab 21, and a negative electrode terminal 22. As shown in Figures 3 and 4, the lithium secondary battery 100 may include electrode tabs 70, namely a positive electrode tab 71 and a negative electrode tab 72, which serve as electrical pathways for guiding the current formed in the electrode assembly 40 to the outside.

[0056] A lithium secondary battery according to one embodiment may be capable of being charged at a high voltage or suitable for being driven at a high voltage. For example, the upper limit charging voltage of the lithium secondary battery may be 4.45V or higher, and may be 4.45V to 4.7V, 4.45V to 4.6V, or 4.45V to 4.55V, etc. By applying the positive electrode active material according to one embodiment, the amount of gas generated can be significantly reduced even when charged at a high voltage, and high capacity and long life characteristics can be achieved.

[0057] negative electrode The negative electrode may include a current collector and a negative electrode active material layer located on the current collector, the negative electrode active material layer including a negative electrode active material and may further include a binder, a conductive material, or a combination thereof.

[0058] negative electrode active material The negative electrode active material includes a substance capable of reversibly inserting / de-inserting lithium ions, lithium metal, an alloy of lithium metal, a lithium-doped and de-doped substance, or a transition metal oxide.

[0059] The material capable of reversibly inserting / deinserting lithium ions is a carbon-based anode active material, which may include, for example, crystalline carbon, amorphous carbon, or a combination thereof. Examples of crystalline carbon include graphite such as amorphous, plate-like, flake-like, spherical, or fibrous natural or artificial graphite, while examples of amorphous carbon include soft carbon or hard carbon, mesophase pitch carbide, and calcined coke.

[0060] As the lithium metal alloy, 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 is used.

[0061] As the substance capable of being doped and undoped with lithium, a Si-based negative electrode active material or a Sn-based negative electrode active material can be used. As the Si-based negative electrode active material, silicon, a silicon-carbon composite, SiOx (0 < x ≤ 2), a Si-Q alloy (where Q is an element selected from alkali metals, alkaline earth metals, group 13 elements, group 14 elements (excluding Si), group 15 elements, group 16 elements, transition metals, rare earth elements, and combinations thereof, for example, Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Tc, Re, Bh, Fe, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Tl, Ge, P, As, Sb, Bi, S, Se, Te, Po, and combinations thereof), or a combination thereof may be used. As the Sn-based negative electrode active material, Sn, SnO2, a Sn alloy, or a combination thereof may be used.

[0062] The silicon-carbon composite may be a composite of silicon and amorphous carbon. The average particle diameter (D 50 ) may be, for example, 0.5 μm to 20 μm. According to one embodiment, the silicon-carbon composite may be in a form in which silicon particles are coated with amorphous carbon on the surface of the silicon particles. For example, it may include secondary particles (cores) formed by granulating primary silicon particles and an amorphous carbon coating layer (shell) located on the surface of the secondary particles. The amorphous carbon is also located between the primary silicon particles, and for example, the primary silicon particles may be coated with amorphous carbon. The secondary particles may be dispersed and present in an amorphous carbon matrix.

[0063] The silicon-carbon composite may further contain crystalline carbon. For example, the silicon-carbon composite may include a core containing crystalline carbon and silicon particles and an amorphous carbon coating layer located on the surface of the core. The crystalline carbon may be artificial graphite, natural graphite, or a combination thereof. Examples of the amorphous carbon include soft carbon, hard carbon, mesophase pitch carbide, and calcined coke.

[0064] When the silicon-carbon composite contains silicon and amorphous carbon, the content of silicon may be 10% to 50% by weight based on 100% by weight of the silicon-carbon composite, and the content of amorphous carbon may be 50% to 90% by weight. When the composite contains silicon, amorphous carbon, and crystalline carbon, the content of silicon may be 10% to 50% by weight based on 100% by weight of the silicon-carbon composite, the content of crystalline carbon may be 10% to 70% by weight, and the content of amorphous carbon may be 20% to 40% by weight.

[0065] Also, the thickness of the amorphous carbon coating layer may be 5 nm to 100 nm. The average particle size (D 50 ) of the silicon particles (primary particles) may be 10 nm to 1 μm, or 10 nm to 200 nm. The silicon particles may exist alone as silicon, in the form of a silicon alloy, or in an oxidized form. The oxidized form of silicon is represented by SiOx (0 < x ≤ 2). At this time, the atomic content ratio of Si:O indicating the degree of oxidation may be 99:1 to 33:67. In this specification, unless otherwise defined, the average particle size (D 50 ) means the diameter of the particles with a cumulative volume of 50% in the particle size distribution.

[0066] The Si-based negative electrode active material or the Sn-based negative electrode active material can be used by mixing with a carbon-based negative electrode active material. When the Si-based negative electrode active material or the Sn-based negative electrode active material and the carbon-based negative electrode active material are used in combination, the mixing ratio may be 1:99 to 90:10 by weight.

[0067] binder The binder plays a role in ensuring that the negative electrode active material particles adhere well to each other and that the negative electrode active material adheres well to the current collector. As the binder, a non-aqueous binder, an aqueous binder, a dry binder, or a combination thereof can be used.

[0068] Examples of non-aqueous binders include polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene propylene copolymer, polystyrene, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamide-imide, polyimide, or combinations thereof.

[0069] The water-based binder may be selected from styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, (meth)acrylonitrile-butadiene rubber, (meth)acrylic rubber, butyl rubber, fluororubber, polyethylene oxide, polyvinylpyrrolidone, polyepichlorohydrin, polyphosphazene, poly(meth)acrylonitrile, ethylene propylene diene copolymer, polyvinylpyridine, chlorosulfonated polyethylene, latex, polyester resin, (meth)acrylic resin, phenolic resin, epoxy resin, polyvinyl alcohol, and combinations thereof.

[0070] When using an aqueous binder as the negative electrode binder, it may further contain a cellulosic compound that can impart viscosity. This cellulosic compound can be a mixture of one or more carboxymethylcellulose, hydroxypropylmethylcellulose, methylcellulose, or alkali metal salts thereof. The alkali metal can be Na, K, or Li.

[0071] The dry binder is a polymeric substance that can be formed into fibers, and may be, for example, polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyethylene oxide, or a combination thereof.

[0072] conductive material Conductive materials are used to impart conductivity to electrodes, and any electronically conductive material that does not undergo chemical changes in the battery that is constructed can be used. Specific examples include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjenblack, carbon fibers, carbon nanofibers, and carbon nanotubes; metallic materials containing copper, nickel, aluminum, silver, etc., in the form of metal powders or metal fibers; conductive polymers such as polyphenylene derivatives; or mixtures thereof.

[0073] The content of the negative electrode active material may be 95% to 99.5% by weight relative to 100% by weight of the negative electrode active material layer, and the content of the binder may be 0.5% to 5% by weight relative to 100% by weight of the negative electrode active material layer. For example, the negative electrode active material layer may contain 90% to 99% by weight of the negative electrode active material, 0.5% to 5% by weight of the binder, and 0.5% to 5% by weight of the conductive material.

[0074] Current collector The negative electrode current collector may include, for example, indium (In), copper (Cu), magnesium (Mg), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), aluminum (Al), germanium (Ge), lithium (Li), or alloys thereof, and may be in the form of foil, sheet, or foam. The thickness of the negative electrode current collector may be, for example, 1 μm to 20 μm, 5 μm to 15 μm, or 7 μm to 10 μm.

[0075] electrolyte The electrolyte for lithium secondary batteries may, for example, be an electrolyte solution, which may contain a non-aqueous organic solvent and a lithium salt.

[0076] Non-aqueous organic solvents act as a medium through which ions involved in the electrochemical reactions of the battery can move. Non-aqueous organic solvents may be carbonate, ester, ether, ketone, or alcoholic solvents, aprotic solvents, or combinations thereof.

[0077] As carbonate-based solvents, dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), methyl ethyl carbonate (MEC), ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate (BC) can be used. As ester-based solvents, methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methyl propionate, ethyl propionate, decanolide, mevalonolactone, valerolactone, and caprolactone can be used. As ether-based solvents, dibutyl ether, tetraglyme, diglyme, dimethoxyethane, 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, and tetrahydrofuran can be used. Furthermore, ketone solvents such as cyclohexanone can be used. As alcoholic solvents, ethyl alcohol and isopropyl alcohol can be used, and as aprotic solvents, nitriles such as R-CN (where R is a linear, branched, or cyclic hydrocarbon group having 2 to 20 carbon atoms, and can include double bonds, aromatic rings, or ether groups); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane and 1,4-dioxolane; and sulfolanes can be used.

[0078] Non-aqueous organic solvents can be used alone or in combination of two or more, and the mixing ratio when using two or more can be appropriately adjusted according to the desired battery performance, which is widely understood by those working in the field.

[0079] When using carbonate-based solvents, cyclic carbonates and linear carbonates can be mixed, and the cyclic carbonates and linear carbonates can be mixed in a volume ratio of 1:1 to 1:9.

[0080] Non-aqueous organic solvents may further include aromatic hydrocarbon organic solvents. For example, carbonate solvents and aromatic hydrocarbon organic solvents can be mixed and used in a volume ratio of 1:1 to 30:1.

[0081] The electrolyte may further contain vinyl ethyl carbonate, vinylene carbonate, or ethylene carbonate compounds to improve battery life.

[0082] Typical examples of the aforementioned ethylene carbonate compounds include fluoroethylene carbonate, difluoroethylene carbonate, chloroethylene carbonate, dichloroethylene carbonate, bromoethylene carbonate, dibromoethylene carbonate, nitroethylene carbonate, and cyanoethylene carbonate.

[0083] Lithium salts are substances that dissolve in organic solvents and act as a source of lithium ions in batteries, enabling the operation of basic lithium secondary batteries and facilitating the movement of lithium ions between the positive and negative electrodes. Typical examples of lithium salts include LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiAlO2, LiAlCl4, LiPO2F2, LiCl, LiI, LiN(SO3C2F5)2, Li(FSO2)2N (lithium bis(fluorosulfonyl)imide; LiFSI), LiC4F9SO3, and LiN(C x F 2x+1 SO2)(C y F2y+1 It may contain one or more selected from SO2) (where x and y are integers from 1 to 20), lithium trifluoromethanesulfonate, lithium tetrafluoroethanesulfonate, lithium difluorobis(oxalate)phosphate (LiDFBOP), and lithium bis(oxalate) borate (LiBOB).

[0084] The lithium salt concentration is preferably used within the range of 0.1 M to 2.0 M. When the lithium salt concentration falls within this range, the electrolyte has appropriate ionic conductivity and viscosity, resulting in excellent performance and effective lithium ion movement.

[0085] Separator Depending on the type of lithium secondary battery, a separator may be present between the positive and negative electrodes. Such separators can be made of polyethylene, polypropylene, polyvinylidene fluoride, or multilayer films of two or more layers of these materials. Mixed multilayer films such as polyethylene / polypropylene two-layer separators, polyethylene / polypropylene / polyethylene three-layer separators, and polypropylene / polyethylene / polypropylene three-layer separators can also be used.

[0086] The separator may include a porous substrate and a coating layer comprising organic, inorganic, or a combination thereof located on one or both sides of the porous substrate.

[0087] The porous substrate may be a polymer film formed from one polymer selected from polyethylene, polyolefins such as polypropylene, polyesters such as polyethylene terephthalate and polybutylene terephthalate, polyacetal, polyamide, polyimide, polycarbonate, polyetherketone, polyaryletherketone, polyetherimide, polyamideimide, polybenzimidazole, polyethersulfone, polyphenylene oxide, cyclic olefin copolymer, polyphenylene sulfide, polyethylene naphthalate, glass fiber, and polytetrafluoroethylene (e.g., Teflon®), or from a copolymer or mixture of two or more of these polymers.

[0088] The porous substrate can have a thickness of approximately 1 μm to 40 μm, for example, 1 μm to 30 μm, 1 μm to 20 μm, 5 μm to 15 μm, or 10 μm to 15 μm.

[0089] The organic material may include a (meth)acrylic copolymer comprising a first structural unit derived from (meth)acrylamide, and a second structural unit comprising at least one of a structural unit derived from (meth)acrylic acid or (meth)acrylate and a structural unit derived from (meth)acrylamide sulfonic acid or a salt thereof.

[0090] The inorganic material may include, but is not limited to, inorganic particles selected from Al2O3, SiO2, TiO2, SnO2, CeO2, MgO, NiO, CaO, GaO, ZnO, ZrO2, Y2O3, SrTiO3, BaTiO3, Mg(OH)2, boehmite, and combinations thereof. The average particle size (D) of the inorganic particles is 50 The wavelength range may be 1 nm to 2000 nm, for example, 100 nm to 1000 nm or 100 nm to 700 nm.

[0091] The organic and inorganic materials can exist mixed together in a single coating layer, or in a form where a coating layer containing organic materials and a coating layer containing inorganic materials are stacked on top of each other.

[0092] The thickness of the coating layer may be 0.5 μm to 20 μm, for example, 1 μm to 10 μm, or 1 μm to 5 μm.

[0093] Examples and comparative examples of the present invention are described below. However, the following examples are merely illustrative examples of the present invention, and the present invention is not limited to the following examples.

[0094] Example 1 1. Manufacturing of positive electrode active material Nickel sulfate (NiSO4·6H2O), cobalt sulfate (CoSO4·7H2O), and manganese sulfate (MnSO4·H2O) were dissolved in distilled water as metal raw materials in a molar ratio of 95:4:1 to prepare a mixed solution. Ammonia water (NH4OH) was prepared for complex compound formation, and sodium hydroxide (NaOH) was prepared as a precipitant.

[0095] After adding a 10 wt% aqueous ammonia solution to a continuous reactor, a mixed metal raw material solution is continuously added, and sodium hydroxide is added to maintain the pH of the reactor at 11. The reaction proceeds slowly for approximately 80 hours, and once the reaction stabilizes, the overflow product is collected, washed, and dried to obtain the final precursor. This yields nickel-based composite hydroxide (Ni) in the form of aggregated primary particles. 0.95 Co 0.04 Mn 0.01 (OH)2) is obtained, and the area is washed and dried.

[0096] By mixing nickel-based composite hydroxide and LiOH so that the molar ratio of lithium to the total amount of metal in the nickel-based composite hydroxide is 1.04, and performing a first heat treatment at approximately 750°C for 15 hours in an oxygen atmosphere, a lithium nickel-based composite oxide (Li) is produced. 1.04 Ni 0.95 Co 0.04 Mn0.01 O2) is obtained. The average particle size of the obtained lithium nickel-based composite oxide is approximately 15 μm, and it is in the form of secondary particles formed by the aggregation of primary particles.

[0097] Distilled water, sodium hydroxide, and aluminum sulfate were added to a 1 L reactor, and the mixture was stirred at approximately 350 rpm for about 5 minutes to dissolve the salt and produce a coating solution. It was confirmed that the salt in the coating solution was completely dissolved and colorless and transparent. The prepared lithium nickel-based composite oxide was added to the coating solution while it was being continuously stirred for 1 minute, and the mixture was stirred for about 30 minutes to produce the first mixed solution. Cobalt sulfate was added to the first mixed solution and stirred to produce the second mixed solution. At this time, the aluminum content of the aluminum sulfate was 0.2 mol%, the sodium content of the sodium hydroxide was 6.0 mol%, and the cobalt content of the cobalt sulfate was 3.0 mol%, relative to 100 mol% of the total metal excluding lithium from the positive electrode active material.

[0098] The solvent was removed from the second mixed solution using an aspirator and a filter press, and the coated product was obtained by vacuum drying at 190°C.

[0099] The aforementioned coated product was subjected to a second heat treatment at 730°C for 8 hours in an oxygen atmosphere to produce a positive electrode active material.

[0100] 2. Manufacturing of lithium-ion batteries A cathode active material layer slurry was prepared by mixing 98.5% by weight of the manufactured cathode active material, 1.0% by weight of polyvinylidene fluoride binder, and 0.5% by weight of carbon nanotube conductive material. This slurry was then coated onto an aluminum foil current collector, dried, and rolled to produce the cathode.

[0101] A negative electrode active material slurry was prepared by mixing 97.5% by weight of graphite negative electrode active material, 1.5% by weight of carboxymethylcellulose, and 1% by weight of styrene-butadiene rubber in an aqueous solvent. The negative electrode active material slurry was coated onto a copper foil current collector, and the negative electrode was produced by drying and rolling.

[0102] A lithium secondary battery was manufactured using a conventional method, employing a polytetrafluoroethylene separator and an electrolyte solution prepared by dissolving 1M LiPF6 in a solvent containing a 3:7 volume ratio mixture of ethylene carbonate and dimethyl carbonate.

[0103] Examples 2 to 4 In the production of the positive electrode active material, the positive electrode active material and lithium secondary battery were manufactured in substantially the same manner as in Example 1, except that the aluminum content of aluminum sulfate, sodium content of sodium hydroxide, and cobalt content of cobalt sulfate were changed as shown in Table 1 below, relative to 100 mol% of the total metal excluding lithium from the positive electrode active material.

[0104] Comparative Examples 1 to 4 In the production of the positive electrode active material, the positive electrode active material and lithium secondary battery were manufactured in substantially the same manner as in Example 1, except that the aluminum content of aluminum sulfate, sodium content of sodium hydroxide, and cobalt content of cobalt sulfate were changed as shown in Table 1 below, relative to 100 mol% of the total metal excluding lithium from the positive electrode active material.

[0105] Evaluation Example 1: Measurement of sodium content in positive electrode active material The sodium content in the positive electrode active materials produced in the above examples and comparative examples was measured using inductively coupled plasma-atomic emission spectroscopy (ICP-AES) and is shown in Table 1 below.

[0106] [Table 1]

[0107] Referring to Table 1, the examples show that when a coating solution with a pH of 12.5 to 14 is first prepared by adding aluminum raw material and sodium hydroxide to an aqueous solvent, a positive electrode active material containing lithium nickel-based composite oxide is added and mixed, a cobalt raw material is mixed, and then drying and heat treatment is performed to form a coating layer, it can be confirmed that the sodium content in the positive electrode active material is 0.082% to 0.173% by weight.

[0108] Evaluation Example 2: Evaluation of Initial Charge / Discharge Capacity and Efficiency The lithium secondary batteries manufactured in the examples and comparative examples were charged at 25°C with a constant current of 0.2C up to an upper voltage limit of 4.45V, then with a constant voltage down to 0.05C, and finally discharged at 0.2C down to a cutoff voltage of 3.0V to perform initial charge and discharge. Table 2 below shows the initial charge capacity, initial discharge capacity, and the efficiency calculated as the ratio of the latter to electrons.

[0109] Evaluation Example 3: Characteristics of High-Temperature Life Following the initial charge and discharge cycle in Evaluation Example 2, the charge and discharge cycles were repeated more than 50 times at 45°C in a voltage range of 3.0V to 4.45V at 1.0C. The ratio of the discharge capacity after 50 cycles to the initial discharge capacity was calculated and is shown in Table 2 below.

[0110] [Table 2]

[0111] Referring to Table 2, it can be seen that in the example where a coating solution with a pH of 12.5 to 14 was first prepared by adding aluminum raw material and sodium hydroxide to an aqueous solvent, a positive electrode active material containing lithium nickel-based composite oxide was added and mixed, a cobalt raw material was mixed, and a coating layer was formed by drying and heat treatment, and the sodium content relative to 100 mol% of the total metal excluding lithium in the positive electrode active material was 0.082% to 0.173% by weight, the charge-discharge efficiency and high-temperature life characteristics were improved compared to the comparative example where this was not the case.

[0112] Although preferred embodiments have been described in detail above, the scope of the present invention is not limited thereto. Various modifications and improvements by those skilled in the art, utilizing the basic concepts defined in the claims, also fall within the scope of the present invention. [Explanation of Symbols]

[0113] 100: Lithium-ion rechargeable battery 10: Positive electrode 11: Positive lead tab 12: Positive terminal 20: Negative electrode 21: Negative lead tab 22: Negative terminal 30: Separator 40: Electrode Assembly 50: Case 60: Sealing member 70: Electrode Tab 71: Positive Tab 72: Negative electrode tab

Claims

1. (i) A step of preparing a coating solution with a pH of 12.5 to 14 by adding aluminum raw material and sodium hydroxide to an aqueous solvent; (ii) A step of preparing a first mixed solution by adding core particles containing lithium nickel-based composite oxide to the coating solution; (iii) The step of preparing a second mixed solution by adding a cobalt raw material to the first mixed solution; and (iv) A step of drying and heat-treating the second mixed solution to obtain a positive electrode active material; A method for producing a positive electrode active material containing the active material.

2. The method for producing a positive electrode active material according to claim 1, wherein the aluminum content in the aluminum raw material is 0.1 mol% to 1.0 mol% relative to 100 mol% of the total metal excluding lithium in the lithium nickel composite oxide.

3. The method for producing a positive electrode active material according to claim 1, wherein the sodium content in the sodium hydroxide is 2.0 mol% to 8.0 mol% relative to 100 mol% of the total metal excluding lithium in the lithium nickel composite oxide.

4. The method for producing a positive electrode active material according to claim 1, wherein the pH of the first mixed solution is 10 to 13.

5. A method for producing a positive electrode active material according to claim 1, wherein the nickel content is 80 mol% or more relative to 100 mol% of the total metal excluding lithium from the lithium nickel composite oxide.

6. The lithium nickel-based composite oxide is represented by chemical formula 1, and is a method for producing a positive electrode active material according to claim 1: [Chemical formula 1] Li a1 Ni x1 M 1 y1 M 2 z1 O 2-b1 X b1 In Chemical Formula 1, 0.9 ≦ a1 ≦ 1.8, 0.3 ≦ x1 ≦ 1, 0 ≦ y1 ≦ 0.7, 0 ≦ z1 ≦ 0.7, 0.9 ≦ x1 + y1 + z1 ≦ 1.1, and 0 ≦ b1 ≦ 0.1, and M 1 and M 2 and M 1 and M 2 are each independently one or more elements selected from the group consisting of Al, B, Ba, Ca, Ce, Co, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sn, Sr, Ti, V, W, Y, Zn, and Zr, and M and M are different elements from each other, and X is one or more elements selected from the group consisting of F, P, and S.

7. The method for producing a positive electrode active material according to claim 1, wherein the cobalt content in the cobalt raw material is 1.0 mol% to 5.0 mol% relative to 100 mol% of the total metal excluding lithium in the lithium nickel composite oxide.

8. The method for producing a positive electrode active material according to claim 1, wherein the molar ratio of the sodium content in the sodium hydroxide to the cobalt content in the cobalt raw material is 1.5:1 to 3:

1.

9. The method for producing a positive electrode active material according to claim 1, wherein the pH of the second mixed solution is 9 to 11.

10. Core particles containing lithium nickel-based composite oxides; and A positive electrode active material comprising a coating layer located on the surface of the core particles and containing aluminum and cobalt; The positive electrode active material contains sodium, The positive electrode active material has a sodium content of 0.08% to 0.2% by weight relative to 100% by weight of the total metal excluding lithium in the lithium nickel composite oxide.

11. The positive electrode active material according to claim 10, wherein the nickel content relative to 100 mol% of the total metal excluding lithium from the lithium nickel composite oxide is 80 mol% or more.

12. The lithium nickel-based composite oxide is the positive electrode active material according to claim 10, represented by chemical formula 1: [Chemical formula 1] Li a1 Ni x1 M 1 y1 M 2 z1 O 2-b1 X b1 In chemical formula 1, 0.9 ≤ a1 ≤ 1.8, 0.3 ≤ x1 ≤ 1, 0 ≤ y1 ≤ 0.7, 0 ≤ z1 ≤ 0.7, 0.9 ≤ x1 + y1 + z1 ≤ 1.1, and 0 ≤ b1 ≤ 0.1, M 1 and M 2 Each of these is independently one or more elements selected from the group consisting of Al, B, Ba, Ca, Ce, Co, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sn, Sr, Ti, V, W, Y, Zn, and Zr, M 1 and M 2 X is a distinct element from one another, and X is one or more elements selected from the group consisting of F, P, and S.

13. The positive electrode active material according to claim 10, wherein the sodium content relative to 100% by weight of the total metal excluding lithium in the lithium nickel composite oxide is 0.082% by weight to 0.173% by weight.

14. Current collector; and A positive electrode active material layer located on the current collector; Includes, The positive electrode active material layer comprises a positive electrode containing the positive electrode active material described in any one of claims 10 to 13.

15. A lithium secondary battery comprising a positive electrode; a negative electrode; and an electrolyte; as described in claim 14.

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