Cathode active material for lithium secondary battery and lithium secondary battery comprising same

Abstract

The present embodiments relate to a cathode active material for a lithium secondary battery and a lithium secondary battery comprising same. The cathode active material for a lithium secondary battery, according to an embodiment, comprises: a nickel-containing metal oxide in a single-particle form; and a doping element doped on the nickel-containing metal oxide, wherein the doping element may include Al, Y, and Zr.

Description

Cathode active material for lithium secondary batteries and lithium secondary batteries containing the same

[0001] These examples relate to a positive electrode active material for a lithium secondary battery and a lithium secondary battery including the same.

[0002] Driven by the recent explosive demand for electric vehicles and the growing demand for longer driving ranges, the development of high-capacity, high-energy-density secondary batteries to meet these demands is actively underway worldwide. In particular, high-nickel NCM cathode materials with high nickel content are being used to meet these demands.

[0003] However, as the nickel content increases, the particle strength decreases, causing microcracks to occur during charge and discharge. In addition, this increases the specific surface area of ​​the cathode material, which increases the reaction with the electrolyte, leading to the problem of increased gas generation. In addition, the structural instability of unstable Ni 3+ Ni is stable 2+ The phenomenon of cation mixing, which is converted into stable NiO by reduction, increases. Therefore, it is difficult to apply this as a cathode active material for lithium-ion batteries for electric vehicles or energy storage.

[0004] To solve this problem, a method was proposed to manufacture the cathode material in the form of a single particle with the primary particle size maximized, rather than in the form of a multi-particle secondary particle in which the primary particles are clumped together, and then apply it.

[0005] However, in general, in order to manufacture a cathode material in the form of a single particle, firing must be performed at a higher temperature than for a multi-particle one, and at this time, over-firing often occurs, causing layered structure crystal defects, which deteriorates electrochemical characteristics such as capacity and output and increases resistance.

[0006] In this embodiment, it is intended to provide a positive electrode active material for a lithium secondary battery having excellent electrochemical properties, improved life and resistance properties, and excellent particle strength, and a lithium secondary battery including the same.

[0007] According to one embodiment, a cathode active material for a lithium secondary battery includes a nickel-containing metal oxide in the form of a single particle; and a doping element doped into the nickel-containing metal oxide; and the doping element may include Al, Y, and Zr.

[0008] A positive electrode for a lithium secondary battery according to another embodiment may include the positive electrode according to one embodiment.

[0009] A lithium secondary battery according to another embodiment may include the positive electrode for a lithium secondary battery according to one embodiment.

[0010] According to the present embodiment, by doping a nickel-containing metal oxide in the form of a single particle with at least three doping elements, specifically, doping elements including Al, Y and Zr, the crystal structure can be stabilized and the particle strength can be improved at the same time.

[0011] Accordingly, in this embodiment, a cathode active material having excellent electrochemical properties and improved lifespan and resistance characteristics can be realized in the form of a single particle.

[0012] The terms first, second, and third, etc., are used to describe, but are not limited to, various parts, components, regions, layers, and / or sections. These terms are used only to distinguish one part, component, region, layer, or section from another part, component, region, layer, or section. Accordingly, a first part, component, region, layer, or section described below may be referred to as a second part, component, region, layer, or section without departing from the scope of the present invention.

[0013] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the present invention. As used herein, the singular forms "singular" and "comprising" include plural forms as well, unless the context clearly dictates otherwise. The word "comprising" as used herein specifies a particular feature, region, integer, step, operation, element, and / or component, but does not exclude the presence or addition of other features, regions, integers, steps, operations, elements, and / or components.

[0014] When a part is referred to as being "on" or "over" another part, it can be directly on or over the other part, or there may be other parts intervening. Conversely, when a part is referred to as being "directly on" another part, there are no other parts intervening.

[0015] Although not defined otherwise, all terms, including technical and scientific terms, used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention pertains. Terms defined in commonly used dictionaries are further interpreted to have meanings consistent with the relevant technical literature and the present disclosure, and are not to be construed as ideal or overly formal unless otherwise defined.

[0016] Also, unless otherwise stated, % means weight%, and 1 ppm is 0.0001 weight%.

[0017] In this specification, the term "combination(s) thereof" described in the expression in the Makushi format means one or more mixtures or combinations selected from the group consisting of the components described in the expression in the Makushi format, and means including any one or more selected from the group consisting of said components.

[0018] Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art can easily implement them. However, the present invention may be implemented in various different forms and is not limited to the embodiments described herein.

[0019]

[0020] Cathode active material for lithium secondary batteries

[0021] As described above, the positive electrode active material in the form of a single particle may be over-calcined, which may cause defects in the layered crystal structure, resulting in a problem of reduced high-temperature life and resistance characteristics.

[0022] However, in this embodiment, this problem was solved by doping the metal oxide using at least three types of doping elements.

[0023] Specifically, a cathode active material for a lithium secondary battery according to one embodiment includes a nickel-containing metal oxide in the form of a single particle; and a doping element doped into the nickel-containing metal oxide; and the doping element may include Al, Y, and Zr.

[0024] In this specification, a single particle may include at least one of a single crystal structure consisting of a single particle and a structure in which 2 to 20 or 2 to 10 particles are clumped together and can be distinguished as a single lump when observing a cross-section of the powder through a scanning electron microscope (SEM). Here, one particle means one grain or crystallite.

[0025] As in this example, the single particle-type active material has a smaller specific surface area than the conventional secondary particle-type positive electrode active material formed by the agglomeration of tens to hundreds of primary particles, thereby reducing the amount of gas generated by side reactions with the electrolyte. In addition, the particle strength is large, which can suppress particle breakage during rolling and reduce the occurrence of cracks due to repeated charging and discharging. Accordingly, it has superior lifespan and safety compared to secondary particles, and has the advantage of being able to realize high energy density of the electrode.

[0026] However, as previously mentioned, single-particle cathode active materials are manufactured through sintering at higher temperatures than conventional secondary particle cathode active materials. In this process, oversintering often occurs, which can lead to layered crystal defects.

[0027] In this embodiment, by doping the nickel-containing metal oxide with at least three doping elements including Al, Y, and Zr, crystal defects such as an increase in the cation mixing ratio due to high-temperature firing can be prevented, and the crystal grain size within a single particle and the average particle diameter of a single particle can be efficiently increased during the firing process.

[0028] In this specification, “crystal grain” means a distinct region in which atoms within a primary particle form a lattice structure with a certain direction.

[0029] Here, the content of Al may be in the range of 200 ppm to 1,800 ppm, and more specifically, in the range of 500 ppm to 1,500 ppm, based on the entire nickel-containing metal oxide. When the content of Al satisfies the above range, the layered structure can be effectively suppressed from deteriorating into a spinel structure. Although the layered structure facilitates the desorption and insertion of lithium ions, the spinel structure does not allow for smooth movement of lithium ions. Therefore, by suppressing the deterioration of the layered structure into a spinel structure, the movement of lithium ions can be facilitated, and as a result, the electrochemical characteristics of the battery can be improved.

[0030] The content of Y may be in the range of 400 ppm to 2,000 ppm, and more specifically, in the range of 700 ppm to 1,700 ppm, based on the entire nickel-containing metal oxide. When the content of Y satisfies the above range, grain growth can be promoted, thereby efficiently increasing the crystal grain size within a single particle and the average particle diameter of the single particle. In addition, since the degree of single particle formation can be increased, the particle strength can be improved.

[0031] The content of Zr may be in the range of 1,200 ppm to 2,800 ppm, and more specifically, in the range of 1,500 ppm to 2,500 ppm, based on the entire doped nickel-containing metal oxide. When the content of Zr satisfies the above range, the shrinkage of the path of lithium ions during the charging and discharging process of the battery can be alleviated, thereby stabilizing the layered structure. Accordingly, the cation mixing ratio can be reduced, and as a result, the resistance characteristics and life characteristics can be improved.

[0032] In the present embodiment, the cation mixing ratio of nickel cations in the lithium layer within the crystal structure of the doped nickel-containing metal oxide may be 1.5% or less, more specifically, in the range of 0.8% to 1.2% or 0.69% to 1.1%. When the cation mixing ratio satisfies the above range, a lithium secondary battery having excellent resistance characteristics and lifespan characteristics can be realized.

[0033] Meanwhile, the content of nickel in the nickel-containing metal oxide of the present embodiment may be 0.8 mol or more, more specifically, 0.8 mol to 0.99 mol, 0.82 mol to 0.95 mol, or 0.82 mol to 0.93 mol, based on 1 mol of the total of transition metals included in the doped nickel-containing metal oxide. When the nickel content satisfies the above range, a high-capacity battery can be realized.

[0034] The nickel-containing metal oxide further includes cobalt, and the content of the cobalt may be 0.06 mol or less, more specifically, greater than 0 and 0.06 mol or less, based on 1 mol of the total of transition metals included in the doped nickel-containing metal oxide.

[0035] In addition, the nickel-containing metal oxide further includes manganese, and the content of the manganese may be 0.15 mol or less, more specifically, in the range of 0.05 mol to 0.1 mol, based on 1 mol of the total of transition metals included in the doped nickel-containing metal oxide.

[0036] More specifically, the nickel-containing metal oxide can be represented by the following chemical formula 1.

[0037] [Chemical Formula 1]

[0038] Li a [Ni x Co y Mn z M1 w1 M2 w2 ]O2

[0039] In the above chemical formula 1, 0.8≤a≤1.2, 0.8≤x≤0.99, 0 <y≤0.06, 0<z≤0.14, 0<w1≤0.1, 0≤w2≤0.05이고, x+y+z+w1+w2=1이고, M1은 Al, Y 및 Zr이고, M2는 B, Al, Mg, Ti, Nb, W, Sc, Si, V, Fe, Y, Mo, Ce, Hf, Ta, La 및 Sr 중 1종 이상을 포함한다.

[0040] In the chemical formula 1, the total content of the doping elements M1 and M2 may be greater than 0 and less than or equal to 0.2 mol, more specifically, in the range of 0.0005 mol to 0.1 mol, 0.0005 mol to 0.08 mol, 0.0005 mol to 0.04 mol, or 0.001 mol to 0.03 mol, based on 1 mol of the total of nickel, cobalt, manganese, and the doping elements. In the chemical formula, the content of the doping element refers to the doping amount of the doping element included in the positive electrode active material finally obtained.

[0041] Meanwhile, the average particle diameter (D50) of the cathode active material according to the present embodiment may be 3 μm or more, and more specifically, 3 μm to 6 μm. When the average particle diameter of the single-particle cathode active material satisfies the above range, a lithium secondary battery with excellent electrochemical properties, such as lifespan characteristics and resistance increase rate, can be realized. In addition, it has a very advantageous effect because it can also increase the energy density per volume.

[0042] The cathode active material of the present embodiment has a very low fine particle generation rate. Specifically, when the cathode active material is pressed five times using a roll press with a press gauge of 0.01 mm, the total value of fine particles smaller than 1 μm may be 2% or less. When the fine particle generation rate satisfies the above range, high-temperature life and resistance characteristics can be improved.

[0043] In addition, the peak temperature of the positive electrode active material of the present embodiment obtained through differential scanning calorimetry (DSC) analysis may be 230°C or higher, more specifically, in the range of 230°C to 280°C.

[0044]

[0045] anode

[0046] In another embodiment, a positive electrode is provided, comprising a current collector and a positive electrode active material layer positioned on one surface of the current collector and comprising a positive electrode active material manufactured according to one embodiment described above.

[0047] The characteristics of the positive electrode active material constituting the positive electrode active material layer are the same as described above. Therefore, a detailed description of the positive electrode active material will be omitted.

[0048] The above-mentioned collector may be, for example, made of stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, etc.

[0049] Meanwhile, the positive electrode active material layer may include a binder and a conductive material.

[0050] At this time, the binder plays a role of improving the adhesion between the positive electrode active material particles and the adhesive strength between the positive electrode active material and the positive electrode current collector. Specific examples include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer rubber (EPDM rubber), sulfonated-EPDM, styrene butadiene rubber (SBR), fluororubber, or various copolymers thereof, and one kind alone or a mixture of two or more kinds thereof may be used, but is not limited thereto. The binder may be included in an amount of 1 to 30 wt% based on the total weight of the positive electrode active material layer.

[0051] And, the conductive material is used to provide conductivity to the electrode, and in the battery to be formed, as long as it does not cause a chemical change and has electronic conductivity, it can be used without any special restrictions. Specific examples include graphite such as natural graphite or artificial graphite; carbon-based materials such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, summer black, and carbon fiber; metal powder or metal fiber such as copper, nickel, aluminum, and silver; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives, and the like. One type alone or a mixture of two or more types among these may be used, but the present invention is not limited thereto. The conductive material may typically be included in an amount of 1 to 30 wt% based on the total weight of the positive electrode active material layer.

[0052] The above positive electrode can be manufactured according to a conventional positive electrode manufacturing method, except that the above positive electrode active material is used.

[0053] Specifically, the positive electrode can be manufactured by applying a composition for forming a positive electrode active material layer, including the positive electrode active material described above and optionally a binder, a conductive agent, or a solvent, on a positive electrode current collector, followed by drying and rolling. At this time, the types and contents of the positive electrode active material, binder, and conductive agent are as described above.

[0054] The solvent may be a solvent generally used in the relevant technical field, such as dimethylsulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, or water. One of these may be used alone or a mixture of two or more thereof may be used. The amount of the solvent used is sufficient to dissolve or disperse the positive electrode active material, conductive material, and binder, taking into account the coating thickness and manufacturing yield of the slurry, and to have a viscosity that can exhibit excellent thickness uniformity when applied thereafter for manufacturing the positive electrode.

[0055] Alternatively, the positive electrode may be manufactured by casting the composition for forming the positive electrode active material layer on a separate support, and then laminating the resulting film on a positive electrode current collector by peeling it off from the support.

[0056]

[0057] lithium secondary battery

[0058] In another embodiment, a lithium secondary battery including the positive electrode is provided.

[0059] The lithium secondary battery may specifically include a positive electrode, a negative electrode positioned opposite the positive electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte, wherein the positive electrode is as described above. In addition, the lithium secondary battery may optionally further include a battery container that houses an electrode assembly including the positive electrode, the negative electrode, and the separator, and a sealing member that seals the battery container.

[0060] In the above lithium secondary battery, the negative electrode may include a negative electrode current collector and a negative electrode active material layer positioned on the negative electrode current collector.

[0061] The negative electrode current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery, and for example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., aluminum-cadmium alloy, etc. can be used. In addition, the negative electrode current collector can typically have a thickness of 3 to 500 ㎛, and like the positive electrode current collector, fine unevenness can be formed on the surface of the current collector to strengthen the bonding strength of the negative electrode active material. For example, it can be used in various forms such as a film, a sheet, a foil, a net, a porous body, a foam, a non-woven fabric, etc.

[0062] The negative electrode active material layer may optionally include a binder and a conductive material together with the negative electrode active material. As an example, the negative electrode active material layer may be manufactured by applying a composition for forming a negative electrode active material layer comprising the negative electrode active material and optionally a binder and a conductive material onto a negative electrode current collector and drying the composition, or by casting the negative electrode forming composition onto a separate support and then laminating the resulting film onto a negative electrode current collector by peeling the film off from the support.

[0063] As the negative electrode active material, a compound capable of reversible intercalation and deintercalation of lithium may be used. Specific examples thereof include carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber, and amorphous carbon; metallic compounds capable of alloying with lithium, such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloy, Sn alloy, and Al alloy; metallic oxides capable of doping and dedoping lithium, such as SiOβ (0 < β < 2), SnO2, vanadium oxide, and lithium vanadium oxide; or composites comprising the metallic compounds and carbonaceous materials, such as Si-C composites or Sn-C composites, and any one or a mixture of two or more of these may be used. In addition, a metallic lithium thin film may be used as the negative electrode active material. In addition, both low-crystalline carbon and high-crystalline carbon may be used as the carbonaceous material. Representative examples of low-crystalline carbon include soft carbon and hard carbon, and representative examples of high-crystalline carbon include natural graphite or artificial graphite in the form of amorphous, plate-like, flaky, spherical, or fiber-like forms, Kish graphite, pyrolytic carbon, mesophase pitch-based carbon fiber, meso-carbon microbeads, mesophase pitches, and high-temperature calcined carbon such as petroleum or coal tar pitch derived cokes.

[0064] The above binder and conductive material may be the same as those described above for the positive electrode.

[0065] Next, depending on the type of lithium secondary battery, a separator may be present between the positive and negative electrodes. Such separators may include polyethylene, polypropylene, polyvinylidene fluoride, or multilayer films of two or more layers thereof, and mixed multilayer films such as a polyethylene / polypropylene two-layer separator, a polyethylene / polypropylene / polyethylene three-layer separator, or a polypropylene / polyethylene / polypropylene three-layer separator may also be used.

[0066] In addition, in the lithium secondary battery, examples of the electrolyte include, but are not limited to, organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel-type polymer electrolytes, solid inorganic electrolytes, and molten inorganic electrolytes that can be used in the manufacture of lithium secondary batteries.

[0067] Specifically, the organic liquid electrolyte may include an organic solvent and a lithium salt.

[0068] The organic solvent may be used without any particular limitation as long as it can serve as a medium through which ions involved in the electrochemical reaction of the battery can move. Specifically, the organic solvent may include ester solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, and ε-caprolactone; ether solvents such as dibutyl ether or tetrahydrofuran; ketone solvents such as cyclohexanone; aromatic hydrocarbon solvents such as benzene and fluorobenzene; Carbonate solvents such as dimethylcarbonate (DMC), diethylcarbonate (DEC), methylethylcarbonate (MEC), ethylmethylcarbonate (EMC), ethylene carbonate (EC), and propylene carbonate (PC); alcohol solvents such as ethyl alcohol and isopropyl alcohol; nitriles such as R-CN (wherein R is a C2 to C20 linear, branched, or cyclic hydrocarbon group, and may include a double-bonded aromatic ring or an ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; or sulfolanes can be used. Among these, a carbonate solvent is preferable, and a mixture of a cyclic carbonate (e.g., ethylene carbonate or propylene carbonate, etc.) having high ionic conductivity and high dielectric constant that can improve the charge / discharge performance of the battery and a linear carbonate compound having low viscosity (e.g., ethyl methyl carbonate, dimethyl carbonate, or diethyl carbonate, etc.) is more preferable.In this case, the performance of the electrolyte may be improved when the cyclic carbonate and the chain carbonate are mixed and used in a volume ratio of about 1:1 to about 1:9.

[0069] The lithium salt may be used without any particular limitation as long as it is a compound capable of providing lithium ions used in a lithium secondary battery. Specifically, the lithium salt may be LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAl04, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2. LiCl, LiI, or LiB(C2O4)2. It is preferable that the concentration of the lithium salt be used within the range of 0.1 to 2.0 M. When the concentration of the lithium salt is within the above range, the electrolyte can exhibit excellent electrolyte performance because it has appropriate conductivity and viscosity, and lithium ions can move effectively.

[0070]

[0071] As described above, a lithium secondary battery including a cathode active material according to the present invention stably exhibits excellent discharge capacity, output characteristics, and capacity retention, and is therefore useful in portable devices such as mobile phones, laptop computers, and digital cameras, and electric vehicles such as hybrid electric vehicles (HEVs).

[0072]

[0073] Hereinafter, embodiments of the present invention will be described in detail. However, these are presented as examples and the present invention is not limited thereto, and the present invention is defined only by the scope of the claims set forth below.

[0074]

[0075] Example 1

[0076] (1) Manufacturing of positive electrode active material

[0077] Ni0.90 Co 0.03 Mn 0.07 After preparing a precursor of (OH)2 composition, a mixture was prepared by uniformly mixing LiOH·H2O (Samsung Chemical, battery grade) as a lithium raw material and Y2O3, ZrO2 and Al(OH)3 as doping raw materials into the precursor.

[0078] At this time, the molar ratio of lithium (Li) to the total metal (Me) excluding lithium (Li / Me) was designed to be 1.05, and doping raw materials were added so that Zr was 2000 ppm, Y was 1200 ppm, and Al was 1000 ppm based on the above precursor.

[0079] The above mixture was placed in a kiln with an oxygen atmosphere and pre-fired at 680°C for 6.5 hours to obtain a pre-fired product. Afterwards, the obtained pre-fired product was placed in a kiln with an oxygen atmosphere and heated to 890°C for 3 hours (1 st After step), it was fired at 940℃ for 1 hour (2 nd step) and then fired at 780℃ for 11 hours (3 rd The sintered product was obtained by sintering using a 3-step method.

[0080] The above-mentioned sintered material was crushed to produce a cathode active material in the form of single particles doped with Al, Y, and Zr.

[0081] (2) Manufacturing of monocells

[0082] (1) A monocell was manufactured using the positive electrode active material manufactured in the following manner.

[0083] Specifically, a positive electrode active material, a conductive agent (acetylene black), and a polyvinylidene fluoride binder (trade name: KF1120) were mixed in a weight ratio of 96.5:1.5:2, and the mixture was added to an N-methyl-2-pyrrolidone solvent so that the solid content was about 30 wt% to prepare a positive electrode active material slurry.

[0084] The above slurry was coated on an aluminum foil (Al foil, thickness: 15 ㎛), which is a positive electrode collector, using a doctor blade, dried, and rolled to manufacture a positive electrode. The loading amount of the positive electrode was about 15-16 mg / cm2, and the rolling density was about 3.5 g / cm 3 It was.

[0085] A monocell was manufactured using the above positive electrode, graphite negative electrode, electrolyte, and polypropylene separator in a conventional manner. Here, the electrolyte was prepared by dissolving 0.7 M LiPF6 and 0.3 M LiFSI in a mixed solvent of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) (mixing ratio EC:EMC = 3:7 volume %) to prepare a mixed solution, and then used.

[0086]

[0087] Comparative Example 1

[0088] In Example 1 (1), when manufacturing a positive electrode active material, a mixture was manufactured by uniformly mixing Zr2O and Al(OH)3 as doping raw materials, and a positive electrode active material was manufactured in the same manner as Example 1, except that the doping raw materials were added so that Zr was 2000 ppm and Al was 1000 ppm based on the precursor.

[0089]

[0090] Experimental Example 1 - Measurement of particle breakage

[0091] The degree of particle breakage was measured using the positive electrodes manufactured according to Example 1 and Comparative Example 1, and the results are shown in Table 1 below.

[0092] Specifically, 10 g of the positive electrode active material was mixed with 3.5 g of NMP, cast on a 20 μm thick aluminum foil (Al foil) (70 mm x 210 mm), and dried in a 120°C convection oven for 30 minutes. Then, a sample was prepared by covering the aluminum foil coated with the positive electrode active material with an aluminum foil of the same size.

[0093] The above sample was pressed 5 times using a roll press with a press gauge of 0.01 mm to obtain 2 g of active material particles. The amount of fine particles generated was analyzed by particle size analysis using a Malvern (MS3000) analyzer using the obtained active material particles. The degree of particle breakage was indicated by the sum of the Vol% of fine particles less than 1 μm in the particle size analysis results.

[0094] Breakage of particle size Example 11.85 vol% Comparative example 12.28 vol%

[0095] Referring to Table 1, it can be confirmed that the rate of occurrence of fine particles in Example 1, a positive electrode active material manufactured by doping three types of doping elements, is very low compared to Comparative Example 1, a positive electrode active material manufactured by doping only two types of doping elements.

[0096] Experimental Example 2 - DSC Measurement

[0097] (1) Manufacturing of coin-shaped half-cells

[0098] According to the examples and comparative examples, a CR2032 coin cell was manufactured using a positive electrode active material using the following method.

[0099] Specifically, a positive electrode active material, a conductive agent (acetylene black FX35, Denka), and a polyvinylidene fluoride binder (trade name: KF9709) were mixed in a weight ratio of 96.5:1.5:2 95:2.2:2.8, and the mixture was added to an N-methyl-2-pyrrolidone solvent so that the solid content was about 65 to 69 wt% to prepare a positive electrode active material slurry.

[0100] The above slurry was coated on an aluminum foil (Al foil, thickness: 20 μm), which is a positive electrode collector, using a doctor blade, dried, and rolled to manufacture a positive electrode. The loading amount of the positive electrode was about 15-16 mg / cm2, and the rolling density was about 3.5 g / cm 3 It was.

[0101] A 2032 coin-type half-cell was manufactured using the above positive electrode, lithium metal negative electrode (400 μm thick, NEBA), electrolyte, and polypropylene polyethylene separator by a conventional method. The electrolyte was prepared by dissolving 1 M LiPF6 in a mixed solvent of ethylene carbonate, dimethyl carbonate, and diethyl carbonate (mixing ratio EC:DMC:DEC=1:2:1 volume %) to prepare a mixed solution.

[0102] (2) DSC measurement

[0103] Differential scanning calorimetry (DSC) analysis was performed using the coin cell manufactured in (1). Specifically, the coin cell was charged to 4.25 V under an initial 0.1 C charge condition, and then the half cell was disassembled to obtain only the positive electrode separately, which was then washed five times with dimethyl carbonate to prepare it. The washed positive electrode was immersed in a DSC crucible with an electrolyte, and the temperature was increased to 350°C. The heat change was measured using a Mettler Toledo DSC1 star system. The obtained DSC peak temperatures are shown in Table 2 below.

[0104] Distinction DSC peak temperature (℃) Example 1232 Comparative Example 1223

[0105] Referring to Table 2, it can be seen that the thermal stability of the positive electrode active material according to Example 1 is superior to that of the positive electrode active material of Comparative Example 1.

[0106] Experimental Example 3 - Capacity Retention Rate Measurement

[0107] After a formation cycle of 0.1C / 0.1C constant current charge / discharge within a voltage range of 2.5 to 4.25 V at 45°C, a constant current charge / discharge test was performed at 0.5C / 1C, and the capacity retention was calculated through the capacity measured every 50 cycles from the 50th to the 700th cycle compared to the first cycle capacity. The results are shown in Table 3 below.

[0108]

[0109] Experimental Example 4 - Measurement of Resistance Increase Rate

[0110] The resistance increase rate was calculated as a percentage (%) of the resistance increase rate measured every 50 cycles from the 50th to the 700th cycle compared to the resistance measured at the first 0.5C charge / 1.0C discharge at high temperature (45℃). The resistance (direct current internal resistance: DC-IR (Direct current internal resistance)) was calculated by measuring the voltage value 60 seconds after applying the discharge current in a 4.25 V charging state and calculating it as '(voltage before current application - voltage 60 seconds after current application) / applied current'. The results are shown in Table 3 below.

[0111] CycleCap. retention [%]ΔDCIR [%]Example 1Comparative Example 1Example 1Comparative Example 15097.897.55.77.010096.696.210.912.815095.394.915.718.920094.293.820.023.925093.292.524.930.230092.191.429.535.135091.490.3 35.241.040090.389.240.746.945088.987.847.853.850087.686.753.759.955085.985.163.269.160084.684.169.875.765083.983.473.979.470082.582.282.387.7

[0112] Referring to Table 3, it can be confirmed that the positive electrode active material according to Example 1 has superior capacity retention and resistance characteristics even when the cycle increases compared to the positive electrode active material according to Comparative Example 1.

[0113] Example 5 - Measurement of cation mixing ratio

[0114] For the positive electrode active materials manufactured according to Example 1 and Comparative Example 1, the cation mixing ratio was measured using the following method. The results are shown in Table 4 below.

[0115] 1) Sample structure analysis using Rigaku's smart lab equipment

[0116] 2) Smart lab equipment configuration

[0117] Goniometer radius: 300.0 mm

[0118] Rotating anode x-ray tube (DPTA-II)

[0119] Theta_s arm: BB Slit

[0120] CBO(cross beam optics for Cu target)

[0121] Soller slit 5.0 deg, 10 mm Incident slit

[0122] Theta_d arm: 8.0mm Receiving slit

[0123] Diffracted beam monochromator (DBM) unit for D / teX Ultra, D / teX Ultra

[0124] Sample stage: ASC-6 (auto sample changer), Reflection knife edge

[0125] 2) Apply 45kV, 200mA (9kW) to the Cu anode to generate X-rays.

[0126] 3) The equipment optics are set to Incident slit 1 / 2 deg, Receiving slit 8.0 mm.

[0127] 4) XRD measurement was performed at Scan 10~80°, Step 0.02°, 10° / min.

[0128] 5) Cation Mixing figures are calculated using Rigaku's SmartLab Studio II x64 v4.2.82.0 S / W to calculate Li / Ni%.

[0129] 6) Calculation is done using WPPF (Whole powder pattern fitting) in S / W.

[0130]

[0131] Classification cation mixing [%] Example 11.1 Comparative Example 11.7

[0132] Referring to Table 3, it can be seen that the cation mixing ratio of the positive electrode active material manufactured according to Example 1 is significantly lower than that of Comparative Example 1.

[0133] The present invention is not limited to the above-described embodiments, but can be manufactured in a variety of different forms. Those skilled in the art will appreciate that the present invention can be implemented in other specific forms without altering the technical spirit or essential characteristics of the present invention. Therefore, the embodiments described above should be understood as illustrative in all respects and not restrictive.

Claims

1. Nickel-containing metal oxide in the form of single particles; and A doping element doped into the nickel-containing metal oxide; A cathode active material for a lithium secondary battery, wherein the above doping elements include Al, Y and Zr.

2. In paragraph 1, A cathode active material for a lithium secondary battery, wherein the cation mixing ratio of nickel cations in a lithium layer within the crystal structure of the doped nickel-containing metal oxide is 1.5% or less.

3. In paragraph 1, A positive electrode active material for a lithium secondary battery, wherein the content of Al is in the range of 200 ppm to 1,800 ppm based on the nickel-containing metal oxide.

4. In paragraph 1, A positive electrode active material for a lithium secondary battery, wherein the content of Y is in the range of 400 ppm to 2,000 ppm based on the nickel-containing metal oxide.

5. In paragraph 1, A positive electrode active material for a lithium secondary battery, wherein the content of Zr is in the range of 1,200 ppm to 2,800 ppm based on the nickel-containing metal oxide.

6. In paragraph 1, A positive electrode active material for a lithium secondary battery, wherein the content of the nickel is 0.8 mol or more based on 1 mol of the total of transition metals included in the nickel-containing metal oxide.

7. In paragraph 1, The above nickel-containing metal oxide further contains cobalt, A positive electrode active material for a lithium secondary battery, wherein the content of the cobalt is 0.06 mol or less based on 1 mol of the total of transition metals included in the doped nickel-containing metal oxide.

8. In paragraph 7, The above nickel-containing metal oxide further contains manganese, A positive electrode active material for a lithium secondary battery, wherein the manganese content is 0.15 mol or less based on 1 mol of the total of transition metals included in the nickel-containing metal oxide.

9. In paragraph 1, The above nickel-containing metal oxide is a positive electrode active material for a lithium secondary battery represented by the following chemical formula 1: [Chemical Formula 1] Li a [Ni x Co y Mr z M1 w1 M2 w2 ]O2 In the above chemical formula 1, 0.8≤a≤1.2, 0.8≤x≤0.99, 0 <y≤0.06, 0<z≤0.14, 0<w1≤0.05, 0≤w2≤0.05이고, x+y+z+w1+w2=1이고, M1은 Al, Y 및 Zr이고, M2는 B, Al, Mg, Ti, Nb, W, Sc, Si, V, Fe, Y, Mo, Ce, Hf, Ta, La 및 Sr 중 1종 이상을 포함한다.

10. In paragraph 1, A cathode active material for a lithium secondary battery, wherein the average particle diameter (D50) of the cathode active material is 3 μm or more.

11. In paragraph 1, The above positive electrode active material is a positive electrode active material for a lithium secondary battery, wherein the sum of fine particles smaller than 1㎛ is 2 vol% or less when pressed 5 times with a press gauge of 0.01 mm using a roll press.

12. In paragraph 1, A cathode active material for lithium secondary batteries, the peak temperature of which is 230°C or higher, obtained through differential scanning calorimetry (DSC) analysis.

13. A positive electrode for a lithium secondary battery comprising the positive electrode active material of any one of claims 1 to 12.

14. A lithium secondary battery comprising the positive electrode for a lithium secondary battery of Article 13.