Method for producing positive electrode active material, positive electrode, and rechargeable lithium battery

Abstract

This invention relates to a method for preparing a positive electrode active material, a positive electrode, and a rechargeable lithium battery. The positive electrode includes a positive electrode active material, which comprises a lithium-nickel-based composite oxide and is in the form of single particles. The volumetric cumulative average particle size (D) of the positive electrode active material is measured using a particle size analyzer. 50 The ratio of the grain size of the positive electrode active material measured by backscattered electron diffraction after ion milling of the positive electrode was 1.6 to 1.8.

Description

Technical Field

[0001] The positive electrode active material, the positive electrode including the positive electrode active material, and the rechargeable lithium battery are disclosed. Background Technology

[0002] Rechargeable lithium-ion batteries are used in portable information devices such as cellular phones, laptops, and smartphones, where they offer high energy density and portability as a power source. Research has been conducted on using high-energy-density rechargeable lithium-ion batteries as a power source or energy storage source for hybrid or electric vehicles.

[0003] Various positive electrode active materials have been studied to enable rechargeable lithium batteries for a variety of applications. With the rapidly increasing demand for large-size, high-capacity, or high-energy-density rechargeable lithium batteries, there is a need to develop positive electrode active materials that offer increased capacity while ensuring stability and enabling operation at high voltages. Summary of the Invention

[0004] It provides positive electrode active materials that can achieve high density, high capacity, long cycle life and high energy density, as well as positive electrodes and rechargeable lithium batteries including them.

[0005] In some example embodiments, the positive electrode includes a positive electrode active material comprising a lithium-nickel-based composite oxide and in the form of (multiple) single particles, wherein the volumetric cumulative average particle size (D) of the positive electrode active material is measured using a particle size analyzer. 50 The ratio of the grain size of the positive electrode active material measured by backscattered electron diffraction after ion milling (ion polishing) of the positive electrode is about 1.6 to about 1.8.

[0006] In some example embodiments, the method for preparing the positive electrode active material includes: (i) preparing (preparing) a positive electrode active material precursor comprising a nickel-based composite hydroxide or a nickel-based composite oxide, the positive electrode active material precursor having a volume cumulative average particle size (D) of about 9 μm to about 25 μm. 50 (ii) mixing the positive electrode active material precursor and lithium feedstock, (iii) subjecting the mixture of the positive electrode active material precursor and lithium feedstock to a first heat treatment to obtain a preliminary (prepared) positive electrode active material in the form of secondary particles comprising a lithium nickel-based composite oxide and wherein a plurality of primary particles are agglomerated, (iv) pulverizing the preliminary positive electrode active material to prepare a pulverized product; and (iv) subjecting the pulverized product to a second heat treatment to obtain a positive electrode active material in the form of single particles.

[0007] In some example implementations, the positive electrode includes a current collector and a layer of positive electrode active material on the current collector.

[0008] In some example implementations, a rechargeable lithium battery is provided, comprising: the positive electrode; the negative electrode; and an electrolyte.

[0009] The positive electrode active material according to some exemplary embodiments can maximize capacity, minimize manufacturing costs, ensure long cycle life characteristics, improve high-voltage characteristics, and improve high-temperature storage characteristics. Rechargeable lithium batteries using the above-described positive electrode active material exhibit high initial charge / discharge capacity and efficiency even under high-voltage drive conditions, can have high energy density due to high agglomerate density, and can have long cycle life characteristics. Attached Figure Description

[0010] Figures 1 to 4 This is a schematic diagram illustrating a rechargeable lithium battery according to an embodiment of the present disclosure. Detailed Implementation

[0011] Specific embodiments will be described in detail below so that those skilled in the art can readily implement them. However, this disclosure may be embodied in many different forms and is not limited to the exemplary embodiments explicitly set forth herein.

[0012] The terminology used herein is for descriptive purposes only and is not intended to limit the scope of this disclosure. Unless the context clearly specifies otherwise, singular expressions include plural expressions.

[0013] As used in this article, "the combination thereof" refers to mixtures, laminates, complexes, copolymers, alloys, blends, reaction products, etc. of the components.

[0014] It should be understood that terms such as “comprising,” “including,” or “having” are intended to specify the presence of the features, numbers, steps, elements (elements) or combinations thereof embodied, but do not preclude the possibility of the presence or addition of one or more other features, numbers, steps, elements (elements) or combinations thereof.

[0015] In the accompanying drawings, for clarity, the thickness of layers, films, panels, regions, etc., is exaggerated, and the same reference numerals denote the same elements throughout the specification. It will be understood that when an element such as a layer, film, region, or substrate is referred to as being "on" another element, it may be directly on said other element, or there may be intermediate elements present. Conversely, when an element is referred to as being "directly on" another element, there are no intermediate elements present.

[0016] In addition, the term "layer" in this article includes not only shapes formed on the entire surface when viewed from a plan view, but also shapes formed on a portion of the surface.

[0017] The average particle size mentioned herein can be measured by methods well known to those skilled in the art, such as by a particle size analyzer, or by transmission electron microscopy or scanning electron microscopy images. Alternatively, the average particle size value can be obtained by measuring using dynamic light scattering, performing data analysis, counting the number of particles in each particle size range, and calculating the average particle size therefrom. Unless otherwise defined, the average particle size can mean the diameter (D) of particles having a cumulative volume of 50% of the particle size distribution. 50 As used herein, unless otherwise defined, mean particle size refers to the diameter of the particle having a cumulative volume of 50% of the particle size in a particle size distribution obtained by randomly measuring the size (diameter or major axis length) of approximately 20 particles in a scanning electron microscope image. 50 ).

[0018] Here, "or" will not be interpreted as exclusive; for example, "A or B" will be interpreted as including A, B, A+B, etc.

[0019] "Metals" include common metals, transition metals, and metalloids (semi-metals).

[0020] Positive electrode active material

[0021] In some example embodiments, the positive electrode active material comprises a lithium-nickel-based composite oxide and is in the form of multiple single particles, wherein the volume-cumulative average particle size (D) of the positive electrode active material is measured using a particle size analyzer. 50 The ratio of the grain size of the positive electrode active material, measured by backscattered electron diffraction after ion milling of the electrode including the positive electrode active material, is about 1.6 to about 1.8.

[0022] Typically, positive electrode active materials comprising lithium nickel-based composite oxides in single-particle form are prepared using precursors in the form of small single particles. However, rechargeable lithium batteries comprising such positive electrode active materials can have problems such as low capacity and efficiency. Therefore, embodiments of this disclosure address these problems by using precursors in the form of large secondary particles, which are then pulverized to prepare positive electrode active materials comprising lithium nickel-based composite oxides in single-particle form. The positive electrode active material prepared by this process has a grain size within a certain range, as measured by backscattered electron diffraction, and an average particle size (D) as measured by a particle size analyzer. 50 ) and their ratio. Furthermore, it has been demonstrated that rechargeable lithium batteries incorporating the aforementioned positive electrode active material exhibit excellent capacity and cycle life characteristics.

[0023] According to some embodiments of the present disclosure, the positive electrode active material includes a lithium nickel-based composite oxide. For example, the lithium nickel-based composite oxide can be represented by the following Chemical Formula 1.

[0024] [Chemical Formula 1]

[0025] Li a1 Ni x1 M 1 y1 M 2 z1 O 2-b1 X b1

[0026] 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 can each independently be one or more 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 can be different from each other, and X can be one or more of F, P, and S. In a further embodiment having Chemical Formula 1, 0.6 ≤ x1 ≤ 1, 0 ≤ y1 ≤ 0.4, and 0 ≤ z1 ≤ 0.4, or 0.8 ≤ x1 ≤ 1, 0 ≤ y1 ≤ 0.2, and 0 ≤ z1 ≤ 0.2, or 0.9 ≤ x1 < 1, 0 < y1 ≤ 0.1, and 0 ≤ z1 ≤ 0.1.

[0027] For example, the lithium nickel-based composite oxide can be a high-nickel-based positive electrode active material, which, based on 100 mol% of the metal other than lithium, has a nickel amount greater than or equal to about 80 mol%, greater than or equal to about 85 mol%, greater than or equal to about 90 mol%, greater than or equal to about 91 mol%, or greater than or equal to about 94 mol% and less than or equal to about 99 mol%. The high-nickel positive electrode active material can have a high capacity and can be applied to a high-capacity, high-density rechargeable lithium battery.

[0028] According to embodiments of this disclosure, the positive electrode active material comprising a lithium-nickel-based composite oxide is in the form of particles, which are single particles, and these single particles may have spherical, ellipsoidal, polyhedral, or irregular shapes. Multiple single particles may exist independently without grain boundaries, each consisting of a single particle, and may be represented as single particles, monolithic structures, integral structures, or non-agglomerated particles, wherein the particles do not aggregate but exist as independent phases in terms of morphology. Furthermore, a single particle may be represented as an integral particle or a single crystal, for example, a single crystal. Single particles may exist independently or aggregate together. For example, 2 to 10 single particles may aggregate and contact each other.

[0029] Based on 100% by weight of the total lithium-nickel-based composite oxide, the amount of lithium remaining on the surface of a single particle containing the lithium-nickel-based composite oxide can be about 1000 ppm or higher, for example, about 1500 ppm to about 2500 ppm. Specifically, based on 100% by weight of the total lithium-nickel-based composite oxide, the amount of LiOH remaining on the surface of a single particle including the lithium-nickel-based composite oxide can be about 0.2% by weight or higher, for example, about 0.2% by weight to about 0.5% by weight or about 0.3% by weight to about 0.5% by weight. Furthermore, based on 100% by weight of the total lithium-nickel-based composite oxide, the amount of Li2CO3 remaining on the surface of the lithium-nickel-based composite oxide can be about 0.3% by weight or higher, for example, about 0.3% by weight to about 1.0% by weight or about 0.4% by weight to about 1.0% by weight. The amounts of residual lithium, LiOH, and Li2CO3 can each be measured by HCl titration.

[0030] In some embodiments, the volume-cumulative average particle size (D) of the positive electrode active material is measured using a particle size analyzer. 50The ratio of the grain size of the positive electrode active material, measured by backscattered electron diffraction after ion milling of the electrode including the positive electrode active material, is in the range of about 1.6 to about 1.8, for example, about 1.65 to about 1.8, or about 1.66 to about 1.8. For example, after ion milling of the electrode including the positive electrode active material, the grain size of the positive electrode active material, measured by backscattered electron diffraction, may be about 1.3 μm to about 2.5 μm. More specifically, the grain size of the positive electrode active material may be about 1.4 μm to about 2.3 μm, about 1.5 μm to about 2.1 μm, about 1.55 μm to about 1.8 μm, about 1.55 μm to about 1.7 μm, about 1.6 μm to about 1.9 μm, or about 1.6 μm to about 1.7 μm. Here, the grain size can be measured by electron backscattered diffraction (EBSD) analysis. EBSD measurement equipment can be, for example, the QUANTAX EBSD from Bruker Corporation, and the sample can undergo ion polishing using a cross-sectional polisher (CP) (such as Ilion from Gatan, Inc.). EBSD can be measured, for example, using a Bruker Corporation e-flash HR EBSD detector at an accelerating voltage of 20 keV. Grain size can refer to the size of a single particle as measured by EBSD. In this case, the electrolyte is uniformly distributed rather than aggregated in specific areas, reducing surface degradation and extending high-temperature cycle life.

[0031] The volume-cumulative average particle size (D) of the positive electrode active material 50 The particle size can be from about 2.0 μm to about 4.0 μm, for example, from about 2.2 μm to about 3.8 μm, from about 2.4 μm to about 3.6 μm, from about 2.6 μm to about 3.4 μm, or from about 2.8 μm to about 3.2 μm. Here, the volumetric cumulative average particle size (D) 50 The positive electrode active material can be measured by a particle size analyzer (PSA), and the diameter of particles with a cumulative volume of 50% in the particle size distribution can be used as the average particle size.

[0032] D of the positive electrode active material 10 It can be about 1.0 μm to about 2.5 μm, for example about 1.1 μm to about 2.4 μm, about 1.2 μm to about 2.3 μm, about 1.3 μm to about 2.2 μm, about 1.4 μm to about 2.1 μm, or about 1.5 μm to about 2.0 μm. 10 It is the diameter of particles that have a cumulative volume of 10% in the particle size distribution, and can be measured by a particle size analyzer for positive electrode active materials.

[0033] D of the positive electrode active material90 It can be about 4.0 μm to about 7.0 μm, for example, about 4.2 μm to about 6.8 μm, about 4.4 μm to about 6.6 μm, about 4.6 μm to about 6.4 μm, or about 4.8 μm to about 6.2 μm. Here, D 90 It is the diameter of particles that have a cumulative volume of 90% in the particle size distribution, and can be measured by a particle size analyzer for positive electrode active materials.

[0034] The span value of the positive electrode active material can be from about 1.0 to about 1.4, for example from about 1.0 to about 1.3, from about 1.0 to about 1.2, or from about 1.0 to about 1.1. Here, the span value is referred to as (D 90 -D 10 ) / D 50 calculate.

[0035] Methods for preparing positive electrode active materials

[0036] In embodiments of this disclosure, a method for preparing a positive electrode active material includes: (i) preparing a nickel-based composite hydroxide or a nickel-based composite oxide having an average particle size (D) of about 9 μm to about 25 μm. 50 (i) a positive electrode active material precursor; (ii) mixing the positive electrode active material precursor and a lithium feedstock and subjecting the mixture to a first heat treatment to obtain a preliminary positive electrode active material in the form of secondary particles comprising a lithium nickel-based composite oxide and wherein a plurality of primary particles are agglomerated, and then pulverizing the material to prepare a pulverized product; and (iii) subjecting the pulverized product to a second heat treatment to obtain a positive electrode active material in the form of single particles.

[0037] Nickel-based composite hydroxides or nickel-based composite oxides are precursors to positive electrode active materials and can take the form of secondary particles formed by the aggregation of multiple primary particles. The average particle size (D) of the secondary particles... 50 The particle size can be approximately 9 μm to approximately 25 μm, approximately 11 μm to approximately 20 μm, or approximately 12 μm to approximately 18 μm. When the average particle size (D) of the precursor of the positive electrode active material... 50 Within these ranges, positive electrode active materials are prepared in single-particle form through a pulverization process, and grain size is measured by backscattered electron diffraction, while the volumetric cumulative average particle size (D) is measured by a particle size analyzer. 50 When the ratio is within the above range, a rechargeable lithium battery containing a positive electrode active material with excellent capacity and cycle life characteristics can be manufactured.

[0038] The positive electrode active material precursor can be a high-nickel positive electrode active material precursor, which has a nickel amount of greater than or equal to about 80 mol%, greater than or equal to about 85 mol%, greater than or equal to about 90 mol%, greater than or equal to about 91 mol%, or greater than or equal to about 94 mol% and less than or equal to about 99 mol% based on 100 mol% of the metal other than lithium in the nickel-based composite hydroxide or nickel-based composite oxide.

[0039] The nickel-based composite hydroxide can be represented, for example, by Chemical Formula 2.

[0040] [Chemical Formula 2]

[0041] Ni x2 M 3 y2 M 4 z2 (OH)2

[0042] In Chemical Formula 2, 0.3 ≤ x2 ≤ 1, 0 ≤ y2 ≤ 0.7, 0 ≤ z2 ≤ 0.7, and 0.9 ≤ x2 + y2 + z2 ≤ 1.1, M 3 and M 4 are each independently one or more 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 3 and M 4 can be different from each other. In a further embodiment having Chemical Formula 2, 0.6 ≤ x2 ≤ 1, 0 ≤ y2 ≤ 0.4, and 0 ≤ z2 ≤ 0.4, or 0.8 ≤ x2 ≤ 1, 0 ≤ y2 ≤ 0.2, and 0 ≤ z2 ≤ 0.2, or 0.9 ≤ x2 < 1, 0 < y2 ≤ 0.1, and 0 ≤ z2 ≤ 0.1.

[0043] The nickel-based composite oxide can be represented, for example, by Chemical Formula 3.

[0044] [Chemical Formula 3]

[0045] Ni x3 M 5 y3 M 6 z3 O

[0046] In Chemical Formula 3, 0.3 ≤ x3 ≤ 1, 0 ≤ y3 ≤ 0.7, 0 ≤ z3 ≤ 0.7, and 0.9 ≤ x3 + y3 + z3 ≤ 1.1, M 5 and M 6 are each independently one or more 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 M5 and M 6 In a further embodiment having Chemical Formula 3, 0.6 ≤ x3 ≤ 1, 0 ≤ y3 ≤ 0.4, and 0 ≤ z3 ≤ 0.4, or 0.8 ≤ x3 ≤ 1, 0 ≤ y3 ≤ 0.2, and 0 ≤ z3 ≤ 0.2, or 0.9 ≤ x3 < 1, 0 < y3 ≤ 0.1, and 0 ≤ z3 ≤ 0.1.

[0047] The method according to the present disclosure includes: mixing a positive electrode active material precursor and a lithium raw material and subjecting the mixture to a first heat treatment to obtain a preliminary positive electrode active material in the form of secondary particles including a lithium nickel-based composite oxide and in which a plurality of primary particles are agglomerated.

[0048] During the first heat treatment, the positive electrode active material precursor and the lithium raw material can be mixed at a molar ratio of about 1:0.9 to about 1:1.8, for example at a molar ratio of about 1:0.9 to about 1:1.5 or about 1:1 to about 1:1.2. The first heat treatment can be carried out in an oxygen atmosphere and can be carried out in a temperature range of, for example, about 750 °C to about 950 °C, or about 760 °C to about 900 °C, or about 770 °C to about 850 °C. The first heat treatment can be carried out for about 2 hours to about 20 hours, or about 4 hours to about 12 hours.

[0049] In the preliminary positive electrode active material, the volume-based average particle size (D 50 ) of the secondary particles can be about 10 μm to about 17 μm. The volume-based average particle size (D 50 ) of the primary particles forming the secondary particles can be about 1 μm to about 5 μm.

[0050] The method according to the present disclosure includes: pulverizing the preliminary positive electrode active material obtained by the first heat treatment to produce a pulverized product. Then, the pulverized product is subjected to a second heat treatment.

[0051] The pulverization can include pulverization as follows: using, for example, a jet mill of the Hosokawa Alpine Group (Blower 35 Hz, AFG 8000 rpm, Air 4 kgf / cm 2 ) to produce a product in the form of small particles having a particle size of about 3 μm to about 4 μm after pulverization.

[0052] The second heat treatment can be carried out in an oxygen atmosphere and can be carried out in a temperature range of, for example, about 600 °C to about 900 °C, or about 610 °C to about 800 °C, or about 620 °C to about 700 °C. The second heat treatment can be carried out for about 2 hours to about 20 hours or about 4 hours to about 18 hours.

[0053] Positive electrode active material in single-particle form can be prepared by a second heat treatment of the pulverized product. The ratio of the volumetric cumulative average particle size of the positive electrode active material, measured using a particle size analyzer, to the grain size, measured by backscattered electron diffraction after the electrode made using the prepared positive electrode active material has undergone ion milling treatment, can be from about 1.6 to about 1.8.

[0054] positive electrode

[0055] In some embodiments of this disclosure, the positive electrode includes a current collector and a layer of positive electrode active material on the current collector, wherein the positive electrode active material layer includes the aforementioned positive electrode active material. In addition to the aforementioned positive electrode active material, the positive electrode active material layer may further include other types of positive electrode active materials. Furthermore, the positive electrode active material layer may further include a binder, a conductive material, or a combination thereof.

[0056] adhesive

[0057] Binders improve the adhesion properties between the active material particles of the positive electrode and with the current collector. Examples of binders include polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide-containing polymers (ethylene oxide-containing polymers), polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, epoxy resin, (meth)acrylate resin, polyester resin, or nylon. However, this disclosure is not limited to these examples.

[0058] conductive materials

[0059] This includes conductive materials to provide electrode conductivity, and any electrically conductive material that does not cause chemical changes in the battery can be used as the conductive material. Examples of conductive materials include: carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fibers, carbon nanofibers, carbon nanotubes, etc.; metal-based materials including metal powders or metal fibers of copper, nickel, aluminum, silver, etc.; conductive polymers such as polyphenylene derivatives; or mixtures thereof.

[0060] Based on 100% by weight of the positive electrode active material layer, the amount of binder and conductive material may be from about 0.5% by weight to about 5% by weight.

[0061] The positive electrode current collector may include an aluminum thin film, but this disclosure is not limited thereto.

[0062] Rechargeable lithium batteries

[0063] In embodiments of this disclosure, the rechargeable lithium battery includes the aforementioned positive electrode, negative electrode, and electrolyte. As an example, the rechargeable lithium battery may include a positive electrode, a negative electrode, a separator between the positive and negative electrodes, and an electrolyte solution.

[0064] Depending on their shape, rechargeable lithium batteries can be cylindrical, prismatic, pouch-shaped, coin-shaped, etc. Figures 1 to 4 This is a schematic diagram illustrating a rechargeable lithium battery according to some example embodiments. Figure 1 Depicting a cylindrical battery, Figure 2 Depict a prismatic battery, and Figure 3 and 4 Depicts a pouch-shaped battery. (Reference) Figures 1 to 4 The rechargeable lithium battery 100 includes an electrode assembly 40 and a housing 50. The electrode assembly 40 has a separator 30 inserted between a positive electrode 10 and a negative electrode 20. The electrode assembly 40 is housed within the housing 50. The positive electrode 10, the negative electrode 20, and the separator 30 may be impregnated with an electrolyte solution (not shown). Figure 1 As shown, the rechargeable lithium battery 100 may include a sealing member 60 of the sealed housing 50. Additionally, as... Figure 2 As shown, the rechargeable lithium battery 100 may include a positive electrode lead connector 11, a positive electrode terminal 12, a negative electrode lead connector 21, and a negative electrode terminal 22. For example... Figure 3 and 4 As shown, the rechargeable lithium battery 100 includes electrode terminals 70, namely, a positive electrode terminal 71 and a negative electrode terminal 72, which form an electrical path for leading the current generated in the electrode assembly 40 to the outside of the battery 100.

[0065] Rechargeable lithium batteries can be rechargeable at high voltages or suitable for driving at high voltages. Furthermore, rechargeable lithium batteries exhibit improved characteristics under high voltage conditions.

[0066] Rechargeable lithium-ion batteries can be designed to operate in high-voltage regions, allowing charging to take place within a voltage range where the upper limit of charging voltage is greater than or equal to approximately 4.0 V. By employing positive electrode active materials and conductive materials, rechargeable lithium-ion batteries can provide high capacity and long cycle life characteristics even when charged at high voltages.

[0067] negative electrode

[0068] The negative electrode includes a current collector and a layer of negative electrode active material on the current collector, and the layer of negative electrode active material may include a negative electrode active material. The negative electrode may further include a binder, a conductive material, or a combination thereof.

[0069] Negative electrode active material

[0070] The negative electrode active material may include a material that reversibly intercalates / deintercalates lithium ions, lithium metal, a lithium metal alloy, a material capable of doping / de-doping lithium, or a transition metal oxide.

[0071] The material that reversibly intercalates / deintercalates lithium ions may include, for example, crystalline carbon, amorphous carbon, or a combination thereof as a carbon-based negative electrode active material. The crystalline carbon may be natural graphite or artificial graphite that is irregular, or in the form of flakes, scales, spheres, or fibers. The amorphous carbon may be soft carbon, hard carbon, a mesophase pitch carbonized product, calcined coke, etc.

[0072] The lithium metal alloy includes 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.

[0073] The material capable of doping / de-doping lithium may be a Si-based negative electrode active material and / or a Sn-based negative electrode active material. The Si-based negative electrode active material may include silicon, a silicon-carbon composite, SiO x (0 < x ≤ 2), a Si-Q alloy, or a combination thereof. In the formula Si-Q, Q is an element selected from the following: 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 a combination thereof, such as 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 a combination thereof. The Sn-based negative electrode active material may be Sn, SnO2, a Sn alloy, or a combination thereof.

[0074] The silicon-carbon composite may be a composite of silicon and amorphous carbon. The average particle size (D 50 ) may be, for example, about 0.5 μm to about 20 μm. The silicon-carbon composite may be in the form of silicon particles and amorphous carbon coated on the surface of the silicon particles. The silicon-carbon composite may include secondary particles (cores) in which silicon primary particles are aggregated and an amorphous carbon coating layer (shell) on the surface of the secondary particles. Amorphous carbon may also be present between the silicon primary particles. For example, the silicon primary particles may be coated with amorphous carbon. The secondary particles may be dispersed in an amorphous carbon matrix.

[0075] The silicon-carbon composite may further include crystalline carbon. For example, the silicon-carbon composite may include: a core including crystalline carbon and silicon particles, and an amorphous carbon coating layer on the surface of the core. The crystalline carbon may be artificial graphite, natural graphite, or a combination thereof. The amorphous carbon may include soft carbon or hard carbon, mesophase pitch carbonized products, and calcined coke.

[0076] If the silicon-carbon composite includes silicon and amorphous carbon, based on 100% by weight of the silicon-carbon composite, the amount of silicon may be about 10% to about 50% by weight, and the amount of amorphous carbon may be about 50% to about 90% by weight. Additionally, if the composite includes silicon, amorphous carbon, and crystalline carbon, based on 100% by weight of the silicon-carbon composite, the amount of silicon may be about 10% to about 50% by weight, the amount of crystalline carbon may be about 10% to about 70% by weight, and the amount of amorphous carbon may be about 20% to about 40% by weight.

[0077] The thickness of the amorphous carbon coating layer may be about 5 nm to about 100 nm. The average particle size (D 50 ) of the silicon particles (primary particles) may be about 10 nm to about 1 μm, or about 10 nm to about 200 nm. The silicon particles may exist as elemental silicon, in the form of a silicon alloy, or in an oxidized form. The oxidized form of silicon may be represented by SiO x (0 < x ≤ 2). The atomic content ratio of Si:O representing the degree of oxidation may be about 99:1 to about 33:67.

[0078] The Si-based negative electrode active material or the Sn-based negative electrode active material may be mixed with the 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 mixed and used, the mixing ratio may be a weight ratio of about 1:99 to about 90:10.

[0079] adhesive

[0080] A binder is used to make the negative electrode active material particles adhere to each other and also to make the negative electrode active material adhere to the current collector. The binder may be a non-aqueous binder, an aqueous binder, a dry binder, or a combination thereof.

[0081] The non-aqueous binder may include polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene-propylene copolymer, polystyrene, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamideimide, polyimide, or a combination thereof.

[0082] Waterborne adhesives may include styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, (meth)acrylonitrile-butadiene rubber, (meth)acrylic rubber, butyl rubber, fluororubber, polyethylene oxide, polyvinylpyrrolidone, polyepoxygenated alcohol, polyphosphazene, poly(meth)acrylonitrile, ethylene propylene diene copolymer, polyvinylpyridine, chlorosulfonated polyethylene, latex, polyester resin, (meth)acrylic resin, phenolic resin, epoxy resin, polyvinyl alcohol, or combinations thereof.

[0083] When an aqueous binder is used as the negative electrode binder, it may further include a cellulose compound capable of imparting viscosity. As a cellulose compound, one or more of carboxymethyl cellulose, hydroxypropyl methyl cellulose, methyl cellulose, or their alkali metal salts may be mixed and used. The alkali metal may be Na, K, or Li.

[0084] Dry adhesives can be polymeric materials that can be formed into fibers, and can be, for example, polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyethylene oxide, or combinations thereof.

[0085] conductive materials

[0086] This includes conductive materials to provide electrode conductivity, and any electrically conductive material that does not cause chemical changes in the battery can be used as the conductive material. Examples of conductive materials include: carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fibers, carbon nanofibers, carbon nanotubes, etc.; metal-based materials including metal powders or metal fibers of copper, nickel, aluminum, silver, etc.; conductive polymers such as polyphenylene derivatives; or mixtures thereof.

[0087] Based on 100% by weight of the negative electrode active material layer, the amount of negative electrode active material may be from about 95% by weight to about 99.5% by weight, and based on 100% by weight of the negative electrode active material layer, the amount of binder may be from about 0.5% by weight to about 5% by weight. For example, the negative electrode active material layer may include about 90% by weight to about 99% by weight of negative electrode active material, about 0.5% by weight to about 5% by weight of binder, and about 0.5% by weight to about 5% by weight of conductive material.

[0088] current collector

[0089] The 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. The current collector may be in the form of a foil, sheet, or foam. The thickness of the current collector may be, for example, about 1 μm to about 20 μm, about 5 μm to about 15 μm, or about 7 μm to about 10 μm.

[0090] electrolytes

[0091] The electrolyte used in rechargeable lithium batteries may be an electrolyte solution, which may include non-aqueous organic solvents and lithium salts.

[0092] Non-aqueous organic solvents are used as media for transporting ions that participate in the electrochemical reactions of a battery. Non-aqueous organic solvents can be carbonate (carbonate-based) solvents, ester (ester-based) solvents, ether (ether-based) solvents, ketone (ketone-based) solvents, or alcohol (alcohol-based) solvents, aprotic solvents, or combinations thereof.

[0093] Carbonate solvents may 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), and butyl carbonate (BC). Ester solvents may include methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methyl propionate, ethyl propionate, decanolactone, mevalonolactone, valproic acid lactone, caprolactone, etc. Ether solvents may include dibutyl ether, tetraethylene glycol dimethyl ether, diethylene glycol dimethyl ether, dimethoxyethane, 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, tetrahydrofuran, etc. Additionally, ketone solvents may include cyclohexanone, etc. Alcohol solvents may include ethanol, isopropanol, etc., and aprotic solvents may include nitriles such as R-CN (where R is a C2 to C20 straight-chain, branched or cyclic hydrocarbon group, and may include double bonds, aromatic rings or ether bonds, etc.); amides such as dimethylformamide; dioxolane such as 1,3-dioxolane, 1,4-dioxolane, etc.; sulfolane, etc.

[0094] Non-aqueous organic solvents can be used alone or in mixtures of two or more types. When two or more types are used in mixtures, the mixing ratio can be appropriately adjusted according to the desired battery performance, as is widely known to those skilled in the art.

[0095] When using carbonate solvents, cyclic carbonates and chain carbonates can be mixed and used together. Cyclic carbonates and chain carbonates can be mixed in a volume ratio of about 1:1 to about 1:9.

[0096] Non-aqueous organic solvents may further include aromatic hydrocarbon organic solvents. For example, carbonate solvents and aromatic hydrocarbon organic solvents may be mixed and used in a volume ratio of about 1:1 to about 30:1.

[0097] The electrolyte solution may further include vinylene carbonate, vinylene carbonate, or ethylene carbonate compounds to improve battery cycle life.

[0098] Examples of ethylene carbonate compounds include fluoroethylene carbonate, difluoroethylene carbonate, chloroethylene carbonate, dichloroethylene carbonate, bromoethylene carbonate, dibromoethylene carbonate, nitroethylene carbonate, and cyanoethylene carbonate.

[0099] Lithium salts dissolved in organic solvents supply lithium ions in batteries, enabling basic operation of rechargeable lithium batteries and improving lithium ion transport between the positive and negative electrodes. Examples of lithium salts include LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiAlO2, LiAlCl4, LiPO2F2, LiCl, LiI, LiN(SO3C2F5)2, Li(FSO2)2N (lithium bis(fluorosulfonyl)imide; LiFSI), LiC4F9SO3, and LiN(C x F 2x+1 SO2)(C y F 2y+1 The first of the following: 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).

[0100] The concentration of lithium salt can range from about 0.1 M to about 2.0 M. If the concentration of lithium salt is within this range, the electrolyte has suitable ionic conductivity and viscosity. Therefore, excellent performance can be achieved, and lithium ions can move efficiently.

[0101] diaphragm

[0102] Depending on the type of rechargeable lithium battery, a separator may be present between the positive and negative electrodes. The separator may include polyethylene, polypropylene, polyvinylidene fluoride, or multilayer films of two or more layers thereof, as well as hybrid multilayer films such as polyethylene / polypropylene bilayer separators, polyethylene / polypropylene / polyethylene trilayer separators, polypropylene / polypropylene / polypropylene trilayer separators, etc.

[0103] The membrane may include a porous substrate (substrate) and a coating layer on one or both surfaces of the porous substrate, comprising organic materials, inorganic materials or combinations thereof.

[0104] The porous substrate may be a polymer membrane formed from any of the following polymers: polyolefins (such as polyethylene and polypropylene), polyesters (such as polyethylene terephthalate and polybutylene terephthalate), polyacetal, polyamide, polyimide, polycarbonate, polyetherketone, polyaryletherketone, polyetherimide, polyamideimide, polybenzimidazole, polyethersulfone, polyphenylene ether, cyclic olefin copolymers, polyphenylene sulfide, polyethylene naphthalate, TEFLON®, and polytetrafluoroethylene, or copolymers or mixtures thereof.

[0105] The porous substrate may have a thickness of about 1 μm to about 40 μm, for example, about 1 μm to about 30 μm, about 1 μm to about 20 μm, about 5 μm to about 15 μm, or about 10 μm to about 15 μm.

[0106] Organic materials may include (meth)acrylic acid copolymers, which include a first structural unit and a second structural unit derived from (meth)acrylamide, wherein the second structural unit includes at least one structural unit derived from (meth)acrylic acid or (meth)acrylate and a structural unit derived from (meth)acryloylsulfamic acid or a salt thereof.

[0107] Inorganic materials may include inorganic particles selected from Al2O3, SiO2, TiO2, SnO2, CeO2, MgO, NiO, CaO, GaO, ZnO, ZrO2, Y2O3, SrTiO3, BaTiO3, Mg(OH)2, boehmite, and combinations thereof. However, embodiments of this disclosure are not limited to these examples. The average particle size (D) of the inorganic particles... 50 The wavelength can be from about 1 nm to about 2000 nm, for example from about 100 nm to about 1000 nm, or from about 100 nm to about 700 nm.

[0108] Organic and inorganic materials can be mixed in a single coating layer. In another embodiment, a coating layer comprising organic materials and a coating layer comprising inorganic materials can be stacked.

[0109] The thickness of the coating can be from about 0.5 μm to about 20 μm, for example from about 1 μm to about 10 μm, or from about 1 μm to about 5 μm.

[0110] The following describes embodiments and comparative examples of the present disclosure. However, the present disclosure is not limited to the following embodiments.

[0111] Example 1

[0112] 1. Preparation of the active material for the first positive electrode

[0113] With an average particle size of 14 μm (D50 Ni 0.94 Co 0.05 Mn 0.01 O and LiOH were mixed to have a molar ratio of (Ni+Co+Mn):Li = 1:1.05. The mixture was then heat-treated at 790 °C for 12 hours under an oxygen atmosphere to prepare LiNi. 0.94 Co 0.05 Mn 0.01 The lithium-nickel-based composite oxide is composed of O2 and has an average particle size of 14 μm (D 50 The secondary particles are in the form of primary particles with a particle size of about 3 μm.

[0114] By using a Hosokawa shot blasting machine with a 35Hz blower, 8000rpm AFG, and 4kgf / cm², 2 The prepared lithium-nickel-based composite oxide was pulverized under air conditions. The pulverized product was then subjected to a secondary heat treatment at 660°C for 16 hours under an oxygen atmosphere to prepare a particle size (D) with an average particle size of 2.98 μm. 50 The positive electrode active material is in the form of single particles.

[0115] 2. Preparation of rechargeable lithium battery cells

[0116] A slurry for the positive electrode active material layer was prepared by mixing 98.5 wt% of the positive electrode active material, 1.0 wt% of the polyvinylidene fluoride binder, and 0.5 wt% of the carbon nanotube conductive material. The slurry was coated onto an aluminum foil current collector, dried, and then compressed to form the positive electrode.

[0117] A negative electrode active material slurry was prepared by mixing 97.5 wt% graphite negative electrode active material, 1.5 wt% carboxymethyl cellulose, and 1 wt% styrene-butadiene rubber in an aqueous solvent. The negative electrode active material slurry was then coated onto a copper foil current collector, dried, and compressed to fabricate the negative electrode.

[0118] A rechargeable lithium-ion battery cell is manufactured using conventional methods by combining a positive electrode and a negative electrode with a polytetrafluoroethylene separator and an electrolyte solution prepared by mixing ethylene carbonate and dimethyl carbonate in a volume ratio of 3:7 and dissolving 1M LiPF6 in the mixed solvent.

[0119] Example 2

[0120] The positive electrode active material and rechargeable lithium battery cell were fabricated in essentially the same manner as in Example 1, except that: an average particle size (D) of 14 μm was used. 50 Ni 0.94 Co0.05 Mn 0.01 O was used to prepare particles with an average size of 14 μm (D 50 LiNi in the form of secondary particles 0.94 Co 0.05 Mn 0.01 O2, then using a Hosokawa jet mill with a 35Hz blower, 8000rpm AFG and 5.0kgf / cm², 2 Pulverization under air conditions was used to prepare particles with an average particle size (D) of 2.64 μm. 50 Lithium-nickel based composite oxides in single-particle form are used to prepare positive electrode active materials.

[0121] Example 3

[0122] The positive electrode active material and rechargeable lithium battery cell were fabricated in essentially the same manner as in Example 1, except that: an average particle size (D) of 14 μm was used. 50 Ni 0.94 Co 0.05 Mn 0.01 O was used to prepare particles with an average size of 14 μm (D 50 LiNi in the form of secondary particles 0.94 Co 0.05 Mn 0.01 O2, then using a Hosokawa jet mill with a 35Hz blower, 8000rpm AFG and 4.5kgf / cm 2 Pulverization under air conditions was used to prepare particles with an average particle size (D) of 2.74 μm. 50 Lithium-nickel based composite oxides in single-particle form are used to prepare positive electrode active materials.

[0123] Comparative Example 1

[0124] The positive electrode active material and rechargeable lithium battery cell were fabricated in essentially the same manner as in Example 1, except that: except for using an average particle size (D) of 4 μm. 50 Ni 0.94 Co 0.05 Mn 0.01 O was used to prepare particles with an average particle size (D) of 6 μm. 50 LiNi in the form of secondary particles 0.94 Co 0.05 Mn 0.01 O2, then using a Hosokawa jet mill with a 35Hz blower, 8000rpm AFG and 4.5kgf / cm 2Pulverization under air conditions was used to prepare particles with an average particle size (D) of 3.99 μm. 50 Lithium-nickel based composite oxides in single-particle form are used to prepare positive electrode active materials.

[0125] Comparative Example 2

[0126] The positive electrode active material and rechargeable lithium battery cell were fabricated in essentially the same manner as in Example 1, except that: except for using an average particle size (D) of 3.5 μm. 50 Ni 0.94 Co 0.05 Mn 0.01 O was used to prepare particles with an average particle size (D) of 6 μm. 50 LiNi in the form of secondary particles 0.94 Co 0.05 Mn 0.01 O2, then using a Hosokawa jet mill with a 35Hz blower, 8000rpm AFG and 4.5kgf / cm 2 Pulverization under air conditions was used to prepare particles with an average particle size (D) of 3.36 μm. 50 Lithium-nickel based composite oxides in single-particle form are used to prepare positive electrode active materials.

[0127] Comparative Example 3

[0128] The positive electrode active material and rechargeable lithium battery cell were fabricated in essentially the same manner as in Example 1, except that: except for using an average particle size (D) of 3 μm. 50 Ni 0.94 Co 0.05 Mn 0.01 O was used to prepare particles with an average particle size (D) of 6 μm. 50 LiNi in the form of secondary particles 0.94 Co 0.05 Mn 0.01 O2, then using a Hosokawa jet mill with a 35Hz blower, 8000rpm AFG and 4.5kgf / cm 2 Pulverization under air conditions was used to prepare particles with an average particle size (D) of 2.96 μm. 50 Lithium-nickel based composite oxides in single-particle form are used to prepare positive electrode active materials.

[0129] Comparative Example 4

[0130] The positive electrode active material and rechargeable lithium battery cell were fabricated in essentially the same manner as in Example 1, except that: except for using an average particle size (D) of 3 μm. 50 Ni 0.94 Co 0.05 Mn 0.01 O was used to prepare particles with an average particle size (D) of 6 μm. 50 LiNi in the form of secondary particles 0.94 Co 0.05 Mn 0.01 O2, then using a Hosokawa jet mill with a 35Hz blower, 8000rpm AFG and 4.0kgf / cm 2 Pulverization under air conditions was used to prepare particles with an average particle size (D) of 3.09 μm. 50 Lithium-nickel based composite oxides in single-particle form are used to prepare positive electrode active materials.

[0131] Measure the D of the positive electrode active material according to the examples and comparative examples 50 D 10 D 90 Span and grain size. The results are shown in Table 1 below. Here, D 50 D 10 and D 90 The particle size was measured using a Particle Size Analyzer (PSA) under the following conditions: pump speed 55%, ultrasonic dispersion of sample at 40 kHz, ultrasonic duration 60 s, run length 60 s, refractive index ratio of sample RI 1.6, e-factor 1.00, sample amount 0.20 g, and sample input of 1 mL of 10% sodium hexametaphosphate dispersant.

[0132] Span as (D 90 -D 10 ) / D 50 calculate.

[0133] Grain size was determined by backscattered electron diffraction (EBSD) analysis, with EBSD measurements performed using a Bruker QUANTAX EBSD detector and the sample ion-milled for 1.5 hours at 6 keV using an Ilion+ cross-section polisher (CP) from Gatan Inc. EBSD analysis was performed using an e-flash HR EBSD detector manufactured by Bruker Corp. at an accelerating voltage of 20 keV.

[0134] Table 1

[0135]

[0136] Evaluation Example 1: Surface Residual Lithium

[0137] The amount of residual lithium on the surface of the positive electrode active material according to the examples and comparative examples was measured by HCl titration. The results are shown in Table 2 below. Specifically, 10 g of each positive electrode active material was added to 100 ml of distilled water and then stirred at 300 rpm for 30 minutes. The pH change of the substance was then measured while HCl was added. Because unreacted residual lithium exists on the surface of the positive electrode active material in the form of Li2CO3, LiOH, etc., the amount of residual lithium on the surface of the positive electrode active material was measured by CO3 titration. 2- OH - Ions such as H+ in HCl + The reaction proceeds in a titration. The amount of HCl solution added is measured to calculate the amount of unreacted residual lithium. In Table 2, the amounts of Li₂CO₃ and LiOH are based on 100% by weight of the positive electrode active material. Total residual lithium (free Li) is measured in ppm and means 10% by weight of 100% by weight of the positive electrode active material. -4 weight%.

[0138] Table 2

[0139]

[0140] Typically, when using large-particle precursors, there is a problem of high residual lithium content on the surface. However, as shown in Table 2, based on 100% by weight of total lithium-nickel composite oxides, the examples have a residual lithium content of 2000 ppm or less, a LiOH content of 0.5% by weight or less, and a Li₂CO₃ content of 1.0% by weight or less. Therefore, the positive electrode active material prepared according to the examples using large-particle precursors has a significantly reduced residual lithium content on the surface.

[0141] Evaluation Example 2: Initial Charge / Discharge Capacity and Efficiency Evaluation

[0142] At 25°C, the rechargeable lithium-ion battery cells according to the embodiments and comparative examples were charged at a constant current of 0.2 C to an upper limit voltage of 4.3 V and then charged at a constant voltage to 0.05 C. The rechargeable lithium-ion battery cells were then discharged at 0.2 C to a cutoff voltage of 3.0 V for initial charging and discharging. The initial charge capacity, initial discharge capacity, and the ratio of the latter to the former as efficiency are shown in Table 3 below.

[0143] Evaluation Example 3: High Temperature Cyclic Life Characteristics

[0144] After the initial charge and discharge of Example 2, the cell was charged and discharged at 1.0 C for 50 cycles or more at 45°C within a voltage range of 3.0 V to 4.3 V to calculate the ratio of the discharge capacity at the 50th cycle to the initial discharge capacity. The results are shown in Table 3.

[0145] Table 3

[0146]

[0147] Referring to Table 3, it is confirmed that the embodiments achieve high initial charge / discharge capacity and initial charge and discharge efficiency, while simultaneously achieving excellent high-temperature cycle life characteristics. In other words, compared to the battery cell including positive electrode active material according to the comparative example, the battery cell including positive electrode active material according to the embodiments exhibits comparable or superior 0.2C charge capacity, improved initial charge and discharge efficiency, high-temperature cycle life characteristics, and in particular, exhibits a 0.2C discharge capacity of 220 mAh / g or higher. Therefore, the embodiments have superior characteristics.

[0148] Although this disclosure has been described in conjunction with exemplary embodiments, it will be understood that this disclosure is not limited to the disclosed embodiments. Rather, it is intended to cover a variety of modifications and equivalent arrangements.

[0149] <Figure Labels>

[0150] 100: Rechargeable lithium battery; 10: Positive electrode

[0151] 11: Positive electrode lead connector 12: Positive electrode terminal

[0152] 20: Negative electrode 21: Negative electrode lead connector

[0153] 22: Negative electrode terminal; 30: Diaphragm

[0154] 40: Electrode assembly; 50: Housing

[0155] 60: Sealing component; 70: Electrode terminal piece

[0156] 71: Positive electrode connector; 72: Negative electrode connector

Claims

1. Positive electrode, including: Positive electrode active materials, including lithium-nickel-based composite oxides, are in the form of single particles. The volume-cumulative average particle size (D) of the positive electrode active material, measured using a particle size analyzer, is... 50 The ratio of the grain size of the active material of the positive electrode, measured by backscattered electron diffraction after ion milling of the positive electrode, is 1.6 to 1.

8.

2. The positive electrode according to claim 1, wherein the lithium nickel-based composite oxide has a nickel content of greater than or equal to 80 mol% based on 100 mol% of the total metals of the lithium nickel-based composite oxide excluding lithium.

3. The positive electrode according to claim 1, wherein the lithium-nickel-based composite oxide is represented by chemical formula 1. Chemical formula 1 is: Li a1 Ni x1 M 1 y1 M 2 z1 O 2-b1 X b1 in, 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 is independently one or more 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 They are different from each other, and X is one or more of F, P and S.

4. The positive electrode according to claim 1, wherein, based on a total of 100% by weight of the lithium nickel-based composite oxide, (i) the amount of LiOH on the surface of the single particle is 0.2% by weight to 0.5% by weight, and (ii) the amount of Li2CO3 on the surface of the single particle is 0.3% by weight to 1.0% by weight.

5. The positive electrode according to claim 1, wherein the positive electrode active material has a grain size of 1.3 μm to 2.5 μm as measured by backscattered electron diffraction after ion milling of the positive electrode.

6. The positive electrode according to claim 1, wherein the volume-cumulative average particle size (D) of the positive electrode active material is... 50 The particle size ranges from 2.0 μm to 4.0 μm, and it was measured using a particle size analyzer.

7. The positive electrode according to claim 1, wherein the diameter (D) of particles having a cumulative volume of 10% in the particle size distribution of the positive electrode active material is... 10 The particle size ranges from 1.0 μm to 2.5 μm, and it was measured using a particle size analyzer.

8. The positive electrode according to claim 1, wherein the diameter (D) of particles having a cumulative volume of 90% in the particle size distribution of the positive electrode active material is... 90 The particle size ranges from 4.0 μm to 7.0 μm, and it was measured using a particle size analyzer.

9. The positive electrode according to claim 1, further comprising: current collector; The positive electrode active material layer on the current collector, The positive electrode active material layer includes the positive electrode active material.

10. A method for preparing a positive electrode active material, the method comprising: (i) Preparing a positive electrode active material precursor comprising a nickel-based composite hydroxide or a nickel-based composite oxide, said positive electrode active material precursor having a volume-cumulative average particle size (D0) of 9 μm to 25 μm. 50 ); (ii) Mix the positive electrode active material precursor and the lithium raw material; (iii) subjecting the mixture of the positive electrode active material precursor and the lithium raw material to a first heat treatment to obtain a preliminary positive electrode active material in the form of secondary particles comprising a lithium nickel-based composite oxide and wherein a plurality of primary particles are agglomerated. (iv) Crush the preliminary positive electrode active material to prepare the crushed product; and (v) The pulverized product is subjected to a second heat treatment to obtain a positive electrode active material in the form of single particles.

11. The method according to claim 10, wherein the nickel-based composite hydroxide is represented by chemical formula 2, and the nickel-based composite oxide is represented by chemical formula 3. Chemical formula 2 is: No x2 M 3 y2 M 4 z2 (OH)2 in, In chemical formula 2, 0.3 ≤ x² ≤ 1, 0 ≤ y² ≤ 0.7, 0 ≤ z² ≤ 0.7, and 0.9 ≤ x² + y² + z² ≤ 1.1, M 3 and M 4 Each is independently one or more 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 3 and M 4 They are different. Chemical formula 3 is In x3 M 5 y3 M 6 z3 SHE In chemical formula 3, 0.3 ≤ x³ ≤ 1, 0 ≤ y³ ≤ 0.7, 0 ≤ z³ ≤ 0.7, and 0.9 ≤ x³ + y³ + z³ ≤ 1.1, M 5 and M 6 Each is independently one or more 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 5 and M 6 They are different from each other.

12. The method of claim 10, wherein the first heat treatment is performed at a temperature of 750°C to 950°C for 2 to 20 hours.

13. The method of claim 10, wherein in the preliminary positive electrode active material, the volume-cumulative average particle size (D) of the secondary particles is... 50 The primary particles forming the secondary particles have a volumetric average particle size (D) of 10 μm to 17 μm. 50 The thickness ranges from 1 μm to 5 μm.

14. The method of claim 10, wherein the second heat treatment is performed at a temperature of 600°C to 900°C for 2 to 20 hours.

15. The method of claim 10, further comprising forming a positive electrode comprising the positive electrode active material, The volume-cumulative average particle size (D) of the positive electrode active material, measured using a particle size analyzer, is... 50 The ratio of the grain size of the active material of the positive electrode, measured by backscattered electron diffraction after ion milling of the positive electrode, is 1.6 to 1.

8.

16. The method of claim 15, wherein the positive electrode active material has a grain size of 1.3 μm to 2.5 μm as measured by backscattered electron diffraction after ion milling of the positive electrode.

17. The method of claim 10, wherein the positive electrode active material has a volumetric cumulative average particle size (D0) of 2.0 μm to 4.0 μm as measured by a particle size analyzer. 50 ).

18. A rechargeable lithium battery, comprising: The positive electrode according to any one of claims 1 to 9; negative electrode; and Electrolytes.

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