Positive electrode active material, positive electrode and lithium secondary battery comprising the same

Abstract

The present invention relates to a single-particle type positive electrode active material capable of improving the lifespan characteristics and gas generation characteristics of a lithium secondary battery, comprising a core portion; and a surface portion formed on the core portion; wherein the single-particle type comprises a lithium nickel-based oxide particle, wherein the single-particle type is a single particle form consisting of one primary particle or a form formed by aggregating two to ten primary particles, wherein the lithium nickel-based oxide particle is doped with a doping element including aluminum (Al), titanium (Ti), and tungsten (W), wherein the surface portion has a higher concentration of Al, Ti, and W than the core portion, and wherein the surface portion has a region in which the concentration of Ti and W is higher than other regions of the surface portion in a region of 15 nm to 25 nm from the surface of the lithium nickel-based oxide particle toward the center of the particle. The invention also relates to a positive electrode active material comprising the same and a lithium secondary battery.

Description

Technology Field

[0001] The present invention relates to a positive electrode active material, a positive electrode containing the same, and a lithium secondary battery, and more specifically, to a positive electrode active material in the form of a single particle, a positive electrode containing the same, and a lithium secondary battery. Background Technology

[0003] With the recent increase in technological development and demand for mobile devices and electric vehicles, the demand for rechargeable batteries as an energy source is rapidly rising. Among these rechargeable batteries, lithium-ion batteries, which possess high energy density and voltage, long cycle life, and low self-discharge rate, have been commercialized and are widely used.

[0004] Lithium transition metal oxides, such as lithium cobalt oxide like LiCoO2, lithium nickel oxide like LiNiO2, and lithium manganese oxide like LiMnO2 or LiMn2O4, have been developed as cathode active materials for lithium secondary batteries, and recently, Li[Ni a Co b Mn c ]O2, Li[Ni a Co b Al c ]O2, Li[Ni a Co b Mn c Al d Lithium composite transition metal oxides containing two or more transition metals, such as O2, have been developed and are widely used.

[0005] Lithium composite transition metal oxides containing two or more transition metals developed to date are typically manufactured in the form of spherical secondary particles formed by the aggregation of tens to hundreds of primary particles. Recently, however, to address structural and thermal stability issues inherent in secondary particle-type cathode active materials, the development of single-particle cathode active materials composed of 10 or fewer primary particles is accelerating. Specifically, when secondary particle-type cathode active materials are applied to lithium secondary batteries, they generate a large amount of gas, leading to the problem of battery volume expansion. Furthermore, increasing the nickel content within the cathode active material to achieve high capacity raises the risk of fire. Consequently, there is a growing demand for the development of single-particle cathode active materials with superior stability. However, single-particle cathode active materials exhibit high resistance, which causes rapid lifespan degradation or increased resistance; therefore, technology to reduce surface resistance is required. The problem to be solved

[0007] The present invention aims to solve the above-mentioned problems by providing a single-particle cathode active material capable of improving the lifespan characteristics and gas generation characteristics of a lithium secondary battery.

[0008] In addition, the present invention aims to provide a lithium secondary battery having improved lifespan characteristics and gas generation characteristics by including the above-mentioned positive electrode active material. means of solving the problem

[0010] To solve the above problem, the present invention provides a positive electrode active material, a positive electrode, and a lithium secondary battery.

[0012] (1) The present invention provides a positive electrode active material comprising a lithium nickel-based oxide particle in the form of a single particle, comprising a core portion; and a surface portion formed on the core portion; wherein the single particle form is a single particle form consisting of one primary particle or a form formed by aggregating two to ten primary particles, and the lithium nickel-based oxide particle is doped with a doping element including aluminum (Al), titanium (Ti), and tungsten (W), and the surface portion has a higher concentration of Al, Ti, and W than the core portion, and the surface portion has a region in which the concentration of Ti and W is higher than other regions of the surface portion in the region of 15 nm to 25 nm from the surface of the lithium nickel-based oxide particle toward the center of the particle.

[0013] (2) The present invention provides a positive electrode active material in which, in (1) above, the surface portion is a region within 30 nm from the surface to the center of the particle.

[0014] (3) The present invention provides an anode active material in which, in (1) or (2), the surface portion comprises a monoclinic phase (C2 / m).

[0015] (4) The present invention provides a positive electrode active material in any one of (1) to (3), wherein the lithium nickel-based oxide has a cobalt (Co) content of 10 mol% or less among the total transition metals.

[0016] (5) The present invention provides a positive electrode active material in any one of (1) to (4), wherein the lithium nickel-based oxide does not contain cobalt (Co).

[0017] (6) The present invention provides a positive electrode active material in which, in any one of (1) to (5), the lithium nickel-based oxide has a composition represented by the following chemical formula 1.

[0018] [Chemical Formula 1]

[0019] Li 1+x1 Mn a1 Ni b1 Al c1 Ti d1 W e1 M 1 f1 O 2-y1 A y1

[0020] In the above chemical formula 1,

[0021] M 1 It is one or more selected from Zr, Y, Cu, Sr, Mn, Mg, Mo, B, Sn, Fe, Zn, and Si, and

[0022] A is one or more selected from F, Cl, Br, I, and S, and

[0023] -0.1≤x1≤0.1, 0 <a1<1, 0<b1<1, 0<c1≤0.1 0<d1≤0.1, 0<e1≤0.1, 0≤f1<0.1, 0≤y1≤0.2이다.

[0024] (7) The present invention provides a positive electrode comprising a positive electrode active material according to any one of (1) to (6).

[0025] (8) The present invention provides a lithium secondary battery comprising: a positive electrode according to (7); a negative electrode; a separator interposed between the positive electrode and the negative electrode; and an electrolyte. Effects of the invention

[0027] The positive electrode active material of the present invention comprises a single-particle lithium nickel-based oxide particle doped with aluminum (Al), titanium (Ti), and tungsten (W), wherein the surface portion of the lithium nickel-based oxide particle is doped in a manner in which the concentrations of Al, Ti, and W are higher than those of the core portion, and the surface portion has a region in which the concentrations of Ti and W are higher than other regions of the surface portion in a region of 15 nm to 25 nm from the surface of the lithium nickel-based oxide particle toward the center of the particle, thereby enabling the stable performance of the existing positive electrode active material in the core portion while simultaneously forming a High Entropy compound in the surface portion to secure structural stability and lower surface resistance, thereby improving the lifespan characteristics and gas generation characteristics of the lithium secondary battery.

[0028] The positive electrode and lithium secondary battery according to the present invention may have excellent lifespan characteristics and gas generation characteristics. Brief explanation of the drawing

[0030] Figure 1 is an SEM image of the positive electrode active material of Example 1. Figure 2 is an SEM image of the positive electrode active material of Comparative Example 1. Figure 3 is an SEM image of the positive electrode active material of Comparative Example 2. Figure 4 is an HAADF-STEM image and EDS data of the cross-section of the positive active material of Example 1. Figure 5 shows the HAADF-STEM image and EDS data of the cross-section of the positive active material of Comparative Example 2. Figure 6 is an HR-(S)TEM image of the cross-section of the positive active material of Example 1. Figure 7 is an HR-(S)TEM image of the cross-section of the positive active material of Comparative Example 2. Specific details for implementing the invention

[0031] Hereinafter, the present invention will be described in more detail to aid in understanding the invention.

[0032] Terms and words used in this specification and claims should not be interpreted as being limited to their ordinary or dictionary meanings, but should be interpreted in a meaning and concept consistent with the technical spirit of the invention, based on the principle that the inventor can appropriately define the concept of the terms to best describe his invention.

[0034] In this specification, terms such as 'comprising,' 'having,' or 'having' are intended to specify the existence of the implemented features, numbers, steps, components, or combinations thereof, and should be understood as not excluding in advance the existence or addition of one or more other features, numbers, steps, components, or combinations thereof.

[0035] In this specification, the term "on" means not only cases where one configuration is formed on the immediate upper surface of another configuration, but also cases where a third configuration is interposed between these configurations.

[0036] In this specification, the term 'single particle form' refers to a form composed of 10 or fewer primary particles, as opposed to a spherical secondary particle form formed by the aggregation of tens to hundreds of primary particles manufactured by conventional methods. Specifically, in the present invention, the single particle form may be a single particle composed of one primary particle, or a secondary particle form formed by the aggregation of 2 to 10 primary particles.

[0037] 'Primary particles' refer to the smallest unit of particles recognized when observing the positive electrode active material through a scanning electron microscope, and 'secondary particles' refer to a secondary structure formed by the aggregation of multiple primary particles.

[0038] In this specification, 'D measured by PSA (particle size analyzer)' 50 ' refers to the particle size at the 50% point of the cumulative volume distribution according to particle size. The above D 50The particle size can be measured by dispersing the powder to be measured in a dispersion medium, introducing it into a commercially available laser diffraction particle size measuring device (e.g., Microtrac's S3500), measuring the difference in diffraction patterns according to particle size as the particles pass through a laser beam to calculate the particle size distribution, and calculating the particle diameter at the point where the cumulative volume distribution according to particle size in the measuring device is 50%.

[0040] positive electrode active material

[0041] The present invention provides a positive electrode active material comprising a lithium nickel-based oxide particle in a single particle form, the core portion and a surface portion formed on the core portion; wherein the single particle form is a single particle form consisting of one primary particle or a form formed by aggregating two to ten primary particles, the lithium nickel-based oxide particle is doped with a doping element including aluminum (Al), titanium (Ti), and tungsten (W), the surface portion has a higher concentration of Al, Ti, and W than the core portion, and the surface portion has a region in which the concentration of Ti and W is higher than in other regions of the surface portion in a region of 15 nm to 25 nm from the surface of the lithium nickel-based oxide particle toward the center of the particle. The lithium nickel-based oxide may have a layered structure.

[0043] The inventors have discovered that a positive electrode active material comprises a lithium nickel-based oxide particle in the form of a single particle, comprising a core portion and a surface portion formed on the core portion, wherein the single particle form is a single particle form consisting of one primary particle or a form formed by aggregating two to ten primary particles, and wherein the lithium nickel-based oxide particle is doped with a doping element including aluminum (Al), titanium (Ti), and tungsten (W), and wherein the surface portion has a higher concentration of Al, Ti, and W than the core portion, and wherein the surface portion has a region in which the concentration of Ti and W is higher than other regions of the surface portion in the region of 15 nm to 25 nm from the surface of the lithium nickel-based oxide particle toward the center of the particle, thereby enabling a compound with a high-entropy structure to achieve surface structural stability and lower surface resistance to achieve high conductivity, and thus improve the lifespan characteristics and gas generation characteristics of a lithium secondary battery, and have completed the present invention.

[0044] That is, the positive electrode active material according to the present invention comprises single-particle lithium nickel-based oxide particles doped with aluminum (Al), titanium (Ti), and tungsten (W), wherein Al, Ti, and W are each more doped in the surface portion than in the core portion, and there exists a region in the surface portion in which the concentration of Ti and W is higher than in other regions of the surface portion in the region of 15 nm to 25 nm from the surface of the lithium nickel-based oxide particles toward the center of the particles, thereby increasing the entropy of the surface layer to secure structural stability and thereby having the effect of lowering surface resistance.

[0045] Meanwhile, when lithium nickel-based oxide particles are not doped with aluminum (Al), titanium (Ti), or tungsten (W), the initial resistance is high due to the low electrical conductivity of the single particles, and this leads to accelerated degradation in lifespan due to the formation of SEI during long-term cycles. Furthermore, when the surface portion of the lithium nickel-based oxide particles is not doped with a higher concentration of Al, Ti, and W than the core portion, it is not possible to confirm both effects of improved lifespan and increased conductivity through reduced resistance.

[0047] According to the present invention, the surface portion may be a region within 30 nm from the surface to the center of the particle on the surface of the lithium nickel-based oxide particle. In this case, the surface layer is coated with a High Entropy doping structure without changing the structure of the core portion, thereby having the advantage of improving resistance and lifespan while maintaining the existing capacity.

[0049] According to the present invention, the surface portion may include a monoclinic phase (C2 / m). In this case, there is an advantage of lowering surface resistance by ensuring structural stability in the surface portion.

[0051] According to the present invention, the lithium nickel-based oxide may have a cobalt (Co) content of 10 mol% or less among the total transition metals. Specifically, the lithium nickel-based oxide may not contain cobalt (Co). For reference, the lower the cobalt content, the higher the resistance, which has the advantage of increasing the effect of the coating.

[0053] According to the present invention, the lithium nickel-based oxide may have a composition represented by the following chemical formula 1.

[0054] [Chemical Formula 1]

[0055] Li 1+x1 Mn a1 Ni b1 Al c1 Ti d1W e1 M 1 f1 O 2-y1 A y1

[0056] In the above chemical formula 1,

[0057] M 1 It is one or more selected from Zr, Y, Cu, Sr, Mn, Mg, Mo, B, Sn, Fe, Zn, and Si, and

[0058] A is one or more selected from F, Cl, Br, I, and S, and

[0059] -0.1≤x1≤0.1, 0 <a1<1, 0<b1<1, 0<c1≤0.1 0<d1≤0.1, 0<e1≤0.1, 0≤f1<0.1, 0≤y1≤0.2이다.

[0060] According to the present invention, in the above formula 1, x1 may be -0.1 or more, -0.09 or more, -0.08 or more, -0.07 or more, -0.06 or more, -0.05 or more, -0.04 or more, -0.03 or more, -0.02 or more, -0.01 or more, or 0 or more, and may be 0.06 or less, 0.07 or less, 0.08 or less, 0.09 or less, or 0.1 or less. When x1 satisfies the above range, high capacity characteristics and high energy density per unit volume can be realized.

[0061] According to the present invention, in Formula 1, a1 represents the atomic fraction of manganese among the metal elements in the lithium nickel-based oxide, and may be greater than 0, 0.3 or less, 0.4 or less, 0.5 or less, 0.6 or less, 0.7 or less, 0.8 or less, 0.9 or less, or less than 1.0. When a1 satisfies the above range, high capacity characteristics can be achieved. In addition, high-temperature stability is increased, and side reactions with the electrolyte can be relatively reduced.

[0062] According to the present invention, in Formula 1, b1 represents the atomic fraction of cobalt among the metal elements in the lithium nickel-based oxide, and may be greater than 0, 0.1 or more, 0.2 or more, 0.3 or more, 0.4 or more, or 0.5 or more, and less than 1.0. When b1 satisfies the above range, high capacity characteristics can be realized. In addition, stability can be improved during the charge / discharge process and rate characteristics can be improved.

[0063] According to the present invention, in the above formula 1, c1 represents the atomic fraction of aluminum among the metal elements in the lithium nickel-based oxide, and may be greater than 0, 0.02 or less, 0.03 or less, 0.04 or less, 0.05 or less, 0.06 or less, 0.07 or less, 0.08 or less, 0.09 or less, or 0.10 or less. When c1 satisfies the above range, the lifespan in long-term cycles can be improved and rate characteristics can be enhanced.

[0064] According to the present invention, in the above formula 1, d1 represents the atomic fraction of titanium among the metal elements in the lithium nickel-based oxide, and may be greater than 0, 0.02 or less, 0.03 or less, 0.04 or less, 0.05 or less, 0.06 or less, 0.07 or less, 0.08 or less, 0.09 or less, or 0.10 or less. When d1 satisfies the above range, side reactions with the electrolyte at the surface are suppressed, thereby improving the lifespan.

[0065] According to the present invention, in the above formula 1, e1 represents the atomic fraction of tungsten among the metal elements in the lithium nickel-based oxide, and may be greater than 0, 0.02 or less, 0.03 or less, 0.04 or less, 0.05 or less, 0.06 or less, 0.07 or less, 0.08 or less, 0.09 or less, or 0.10 or less. When e1 satisfies the above range, it has the effect of enabling stable capacity expression by securing a Li migration pathway.

[0066] According to the present invention, in the above formula 1, f1 is M among the metal elements in the lithium nickel-based oxide. 1 It refers to the atomic fraction of an element, which may be 0 or greater, 0.01 or less, 0.02 or less, 0.03 or less, 0.04 or less, 0.05 or less, 0.06 or less, 0.07 or less, 0.08 or less, 0.09 or less, or 0.10 or less. When f1 satisfies the above range, the stability of the crystal structure of the positive active material can be improved and the particle shape can be improved.

[0068] According to the present invention, the lithium nickel-based oxide may be doped with Al in an amount greater than 0 mol% and less than or equal to 2 mol% to ensure structural stability and improve lifespan.

[0069] According to the present invention, the lithium nickel-based oxide may be doped with more than 0 mol% and less than or equal to 2 mol% of Ti to ensure structural stability and improve resistance.

[0070] According to the present invention, the lithium nickel-based oxide may be doped with W of more than 0 mol% and less than or equal to 2 mol% to secure capacity.

[0072] According to the present invention, the positive active material is D measured by a PSA (particle size analyzer). 50 This can be 2㎛ to 18㎛. D of the positive electrode active material measured by a PSA (particle size analyzer) 50If it falls within the above range, the lifespan and capacity characteristics of the battery containing it are both improved, and the electrochemical performance can be optimized.

[0074] The positive active material according to the present invention may be manufactured by the following method for manufacturing a positive active material, but is not limited thereto.

[0075] A single-particle cathode active material according to the present invention can be manufactured by a method for manufacturing a cathode active material comprising: (A) a step of manufacturing a first sintered product by mixing a cathode active material precursor (complex transition metal hydroxide) and a lithium-containing raw material such that the ratio (M:Li) of the total number of moles of transition metal (M) included in the cathode active material precursor and the number of moles of lithium (Li) included in the lithium-containing raw material is 1:0.97 to 1.02, and then performing a first sintering at 850 to 950°C; and (B) a step of manufacturing a second sintered product by mixing the first sintered product, an Al raw material, a Ti raw material, a W raw material, and a lithium raw material such that the molar ratio (Li' / M') of lithium to transition metal in the final cathode active material is 1.00 to 1.10, and then performing a second sintering at 650 to 750°C. At this time, the cathode active material according to the present invention can be manufactured by appropriately controlling the ratio of raw materials, the calcination temperature, etc. Meanwhile, the lithium raw material of step (A) and the lithium raw material of step (B) may be different. For example, if the lithium raw material of step (A) is Li2CO3, the lithium raw material of step (B) may be LiOH.

[0077] (A) Step

[0078] Step (A) above is a step of preparing a first calcined product by mixing a positive electrode active material precursor (complex transition metal hydroxide) and a lithium-containing raw material such that the molar ratio of lithium to transition metal (Li / Me) is 0.97 to 1.02, and then performing a first calcination at 850 to 950°C.

[0080] According to the present invention, the positive active material precursor may have a composition represented by the following chemical formula 2.

[0081] [Chemical Formula 2]

[0082] Mn a2 Ni b2 M 2 c2 (OH)2

[0083] In the above chemical formula 2,

[0084] M 2 is one or more selected from Zr, Y, Al, W, Cu, Sr, Mn, Ti, Mg, Mo, B, Sn, Fe, Zn, and Si, and

[0085] 0 <a2≤0.3, 0.5≤b2<1,0≤c2≤0.2이다.

[0087] According to the present invention, the lithium-containing raw material may be a lithium-containing sulfate, nitrate, acetate, carbonate, oxalate, citrate, halide, hydroxide, or oxyhydroxide, and is not particularly limited as long as it is soluble in water. Specifically, the lithium-containing raw material may be Li2CO3, LiNO3, LiNO2, LiOH, LiOH·H2O, LiH, LiF, LiCl, LiBr, LiI, CH3COOLi, Li2O, Li2SO4, CH3COOLi, or Li3C6H5O7, and any one or more of these may be used.

[0088] According to the present invention, the positive electrode active material precursor and the lithium-containing raw material are mixed such that the ratio (M:Li) of the total number of moles of transition metal (M) included in the positive electrode active material precursor and the number of moles of lithium (Li) included in the lithium-containing raw material is 1:0.97 to 1.02. In this case, in order to proceed with coating while adding Li in step B, a lower number of moles of Li compared to the final Li / Me ratio must be added in step A.

[0090] According to the present invention, the first firing is performed at 850 to 950°C. In this case, if a sufficient temperature is not applied, there is a problem that single particles are not formed.

[0091] According to the present invention, the primary firing can be performed under an oxygen atmosphere or an atmospheric atmosphere.

[0092] According to the present invention, the first firing can be performed for 5 to 20 hours. In this case, a sufficient amount of heat must be applied for single-particle formation to proceed.

[0094] (B) Step

[0095] Step (B) above is a step of manufacturing a second sintered product by mixing the first sintered product, Al raw material, Ti raw material, W raw material, and lithium raw material so that the molar ratio of lithium to transition metal (Li' / M') in the final cathode active material is 1.00 to 1.10, and then performing a second sintering at 650 to 750°C.

[0097] According to the present invention, the Al raw material may be one or more selected from Al2O3, Al(OH)3, AlCl3, AlF3, and Al2(SO4)3, specifically one or more selected from Al2O3, Al(OH)3, and AlF3, and more specifically Al2O3.

[0098] According to the present invention, the Ti raw material may be one or more selected from TiO2, Ti2O3 and TiCl4, and more specifically, may be TiO2.

[0099] According to the present invention, the W raw material may be one or more selected from WO3, WC, and H2WO4, and more specifically, may be WO3.

[0100] According to the present invention, the lithium-containing raw material may be a lithium-containing sulfate, nitrate, acetate, carbonate, oxalate, citrate, halide, hydroxide, or oxyhydroxide, and is not particularly limited as long as it is soluble in water. Specifically, the lithium-containing raw material may be Li2CO3, LiNO3, LiNO2, LiOH, LiOH·H2O, LiH, LiF, LiCl, LiBr, LiI, CH3COOLi, Li2O, Li2SO4, CH3COOLi, or Li3C6H5O7, and any one or more of these may be used.

[0101] According to the present invention, the primary calcined product and the lithium-containing raw material are mixed such that the molar ratio of lithium to transition metal (Li' / M') in the final cathode active material is 1.00 to 1.10. In this case, as Li melts, a structure in the form of a High Entropy doping is formed and distributed on the surface, forming a band-shaped coating layer.

[0103] According to the present invention, the secondary calcination is performed at 650 to 750°C. In this case, if the temperature is too high, doping occurs, and if it is too low, Li does not melt, resulting in a problem where sufficient compound formation is not achieved.

[0104] According to the present invention, the secondary firing can be performed under both an oxygen atmosphere and an atmospheric atmosphere.

[0105] According to the present invention, the secondary firing can be performed for 5 to 20 hours. In this case, if it is done for too long, doping occurs, and if it is done for too short, there is a problem that a sufficient coating layer is not formed.

[0107] anode

[0108] The present invention provides a positive electrode comprising the above positive electrode active material.

[0109] The above positive electrode may include a positive electrode current collector and a positive electrode active material layer formed on the positive electrode current collector, and the positive electrode active material layer may include the positive electrode active material.

[0110] The above positive current collector may include a highly conductive metal, and is not particularly limited as long as it facilitates the adhesion of the positive active material layer and is non-reactive within the voltage range of the battery. The above positive current collector may be, for example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface treated with carbon, nickel, titanium, silver, etc. Additionally, the above positive current collector may typically have a thickness of 3 μm to 500 μm, and may form fine irregularities on the surface of the current collector to increase the adhesion of the positive active material. It may be used in various forms, such as films, sheets, foils, nets, porous bodies, foams, and nonwoven fabrics.

[0111] The positive active material layer may include, together with the positive active material, a conductive material and a binder as needed. In this case, the positive active material may be included in an amount of 80% to 99% by weight, more specifically 85% to 98.5% by weight, based on the total weight of the positive active material layer, and may exhibit excellent capacity performance within this range.

[0112] The above conductive material is used to impart conductivity to the electrode, and in the battery being constructed, it may be used without special limitations as long as it possesses electronic conductivity without causing chemical changes. 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, thermal black, and carbon fibers; metal powder or metal fibers such as copper, nickel, aluminum, and silver; conductive tubes such as carbon nanotubes; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives, and one of these alone or a mixture of two or more may be used. The above conductive material may be included in an amount of 0.1% to 15% by weight relative to the total weight of the positive electrode active material layer.

[0113] The above binder serves to improve the adhesion between positive active material particles and the adhesion between the positive active material and the current collector. Specific examples include polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, polymethyl methacrylate, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene butadiene rubber (SBR), fluororubber, polyacrylic acid, and polymers in which hydrogens thereof are substituted with Li, Na, or Ca, or various copolymers thereof, and one of these alone or a mixture of two or more may be used. The above binder may be included in an amount of 0.1% to 15% by weight relative to the total weight of the positive active material layer.

[0114] The above-described anode may be manufactured according to a conventional anode manufacturing method, except for using the above-described anode active material. Specifically, the above-described anode may be manufactured by applying a composition for forming an anode active material layer, prepared by dissolving or dispersing the above-described anode active material and, optionally, a binder, a conductive material, and a dispersant in a solvent, onto an anode current collector, followed by drying and rolling, or by casting the composition for forming an anode active material layer onto a separate support and then laminating the film obtained by peeling from the support onto an anode current collector.

[0115] The above solvent may be a solvent generally used in the relevant technical field, and may include dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), dimethylformamide (DMF), acetone, or water, and one of these alone or a mixture of two or more may be used. The amount of the above solvent used is sufficient if it is sufficient to dissolve or disperse the anode active material, conductive material, binder, and dispersant, taking into account the coating thickness of the slurry and the manufacturing yield, and to have a viscosity that can exhibit excellent thickness uniformity when coated for anode manufacturing thereafter.

[0117] lithium secondary battery

[0118] The present invention provides a lithium secondary battery comprising: the anode; the cathode; a separator and an electrolyte interposed between the anode and the cathode.

[0120] The above lithium secondary battery may optionally further include a battery container that accommodates the electrode assembly of the positive electrode, negative electrode, and separator, and a sealing member that seals the battery container.

[0122] The above cathode may include a cathode current collector and a cathode active material layer located on the cathode current collector.

[0123] The above-mentioned negative 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., and aluminum-cadmium alloy may be used. In addition, the above-mentioned negative current collector may typically have a thickness of 3 μm to 500 μm, and, similar to the positive current collector, fine irregularities may be formed on the surface of the current collector to strengthen the bonding strength of the negative active material. For example, it may be used in various forms such as a film, sheet, foil, net, porous body, foam, nonwoven fabric, etc.

[0124] The above-mentioned cathode active material layer may optionally include a binder and a conductive material together with the cathode active material.

[0125] As the above-mentioned negative electrode active material, a compound capable of reversible intercalation and deintercalation of lithium may be used. Specific examples 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 alloys, Sn alloys, or Al alloys; and SiO₂ βExamples include metal oxides capable of doping and dedoping lithium, such as (0<β<2), SnO2, vanadium oxide, and lithium vanadium oxide; or composites comprising the metal compound and carbonaceous material, such as Si-C composites or Sn-C composites, and any one or more of these may be used. Additionally, a metallic lithium thin film may be used as the negative electrode active material. Furthermore, the carbon material may include low-crystallinity carbon and high-crystallinity carbon. Representative examples of low-crystallinity carbon include soft carbon and hard carbon, while representative examples of high-crystallinity carbon include amorphous, plate-like, flake-like, spherical, or fibrous natural or artificial graphite, 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. The above-mentioned cathode active material may be included in an amount of 80% to 99% by weight based on the total weight of the cathode active material layer.

[0126] The binder of the above-mentioned negative electrode active material layer is a component that assists in the bonding between the conductive material, the active material, and the current collector, and is typically added in an amount of 0.1% to 10% by weight based on the total weight of the negative electrode active material layer. Examples of such binders include polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene-butadiene rubber, nitrile-butadiene rubber, fluororubber, and various copolymers thereof.

[0127] The conductive material of the above-mentioned negative electrode active material layer is a component for further improving the conductivity of the negative electrode active material, and may be added in an amount of 10% by weight or less, preferably 5% by weight or less, based on the total weight of the negative electrode active material layer. Such conductive material is not particularly limited as long as it is conductive without causing chemical changes in the battery, and for example, graphite such as natural graphite or artificial graphite; carbon black such as acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black; conductive fibers such as carbon fibers or metal fibers; fluorinated carbon; metal powder such as aluminum or nickel powder; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; conductive materials such as polyphenylene derivatives may be used.

[0128] The above cathode may be manufactured by applying and drying a composition for forming a cathode active material layer, prepared by dissolving or dispersing a cathode active material and optionally a binder and a conductive material in a solvent, onto a cathode current collector, or by casting the composition for forming a cathode active material layer onto a separate support and then laminating the film obtained by peeling from the support onto a cathode current collector.

[0129] The above separator separates the negative electrode and the positive electrode and provides a pathway for the movement of lithium ions. It can be used without special restrictions as long as it is commonly used as a separator in a lithium secondary battery, and it is particularly desirable that it has low resistance to the movement of electrolyte ions and excellent electrolyte wettability. Specifically, a porous polymer film, such as a porous polymer film made of a polyolefin-based polymer like ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer, and ethylene / methacrylate copolymer, or a laminated structure of two or more layers thereof may be used. In addition, a conventional porous nonwoven fabric, such as a nonwoven fabric made of high-melting-point glass fiber or polyethylene terephthalate fiber, may be used. Furthermore, a coated separator containing ceramic components or polymer materials may be used to ensure heat resistance or mechanical strength, and it may optionally be used in a single-layer or multi-layer structure.

[0130] Examples of the above electrolytes include organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel-type polymer electrolytes, solid inorganic electrolytes, molten inorganic electrolytes, etc., which can be used in the manufacture of lithium secondary batteries, but are not limited to these. As a specific example, the above electrolyte may include an organic solvent and a lithium salt.

[0131] The above-mentioned organic solvent may be used without special restrictions as long as it can serve as a medium through which ions involved in the electrochemical reaction of the battery can move. Specifically, the above-mentioned organic solvent may include ester-based solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, and ε-caprolactone; ether-based solvents such as dibutyl ether or tetrahydrofuran; ketone-based solvents such as cyclohexanone; aromatic hydrocarbon-based solvents such as benzene and fluorobenzene; and carbonate-based solvents such as dimethyl carbonate (DMC), diethyl carbonate (DEC), ethylmethyl carbonate (EMC), ethylene carbonate (EC), and propylene carbonate (PC). Alcohol-based solvents such as ethyl alcohol and isopropyl alcohol; nitriles such as R-CN (where R is a straight-chain, branched, or cyclic hydrocarbon group having 2 to 20 carbon atoms and may include a double bond-directing ring or ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; or sulfolanes may be used. Among these, carbonate-based solvents are preferred, 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 low-viscosity linear carbonate-based compound (e.g., ethylmethyl carbonate, dimethyl carbonate or diethyl carbonate, etc.) is more preferred.

[0132] The above lithium salt may be used without special restrictions as long as it is a compound capable of providing lithium ions used in lithium secondary batteries. Specifically, as the anion of the above lithium salt, F - , Cl - , Br - , I - , NO3 - , N(CN)2 - , BF4 - , CF3CF2SO3 - , (CF3SO2)2N - , (FSO2)2N - , CF3CF2(CF3)2CO - , (CF3SO2)2CH - , (SF5)3C - , (CF3SO2)3C - , CF3(CF2)7SO3 - , CF3CO2 - , CH3CO2 - , SCN - and (CF3CF2SO2)2N - The lithium salt may be at least one selected from the group consisting of LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAlO4, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2, LiCl, LiI, or LiB(C2O4)2. It is preferable to use the lithium salt within the range of 0.1 M to 2.0 M. When the concentration of the lithium salt falls within the above range, the electrolyte has appropriate conductivity and viscosity, so it can exhibit excellent electrolyte performance and lithium ions can move effectively.

[0133] In addition to the above electrolyte components, the above electrolyte may further include one or more additives for the purpose of improving battery life, suppressing battery capacity reduction, and improving battery discharge capacity, such as, for example, haloalkylene carbonate compounds like difluoroethylene carbonate, pyridine, triethylphosphite, triethanolamine, cyclic ether, ethylene diamine, n-glyme, triamide hexaphosphate, nitrobenzene derivative, sulfur, quinone imine dye, N-substituted oxazolidinone, N,N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2-methoxyethanol, or aluminum trichloride. In this case, the additive may be included in an amount of 0.1% to 5% by weight based on the total weight of the electrolyte.

[0135] Since the lithium secondary battery containing the positive electrode active material according to the present invention has excellent performance, it is useful in fields such as portable devices like mobile phones, laptop computers, and digital cameras, and electric vehicles such as hybrid electric vehicles (HEV) and electric vehicles (EV).

[0136] The external shape of the lithium secondary battery of the present invention is not particularly limited, but can be a cylindrical shape using a can, a prismatic shape, a pouch shape, or a coin shape.

[0137] The lithium secondary battery according to the present invention can be used not only as a battery cell used as a power source for a small device, but can also preferably be used as a unit cell in a medium-to-large battery module comprising a plurality of battery cells.

[0138] Accordingly, a battery module including the above-mentioned lithium secondary battery as a unit cell and a battery pack including the same are provided.

[0139] The above battery module or battery pack can be used as a power source for one or more medium-to-large devices, including a power tool; an electric vehicle (EV), a hybrid electric vehicle, and a plug-in hybrid electric vehicle (PHEV); or a power storage system.

[0141] Hereinafter, embodiments of the present invention are described in detail so that those skilled in the art can easily implement the invention. However, the present invention may be embodied in various different forms and is not limited to the embodiments described herein.

[0143] Examples and Comparative Examples

[0144] Example 1

[0145] Complex transition metal hydroxide (Composition: Mn 0.23 Ni 0.77 (OH)2, D 50 A mixture was prepared by mixing Li2CO3 and Al(OH)3 with the total number of moles of transition metal (Mn+Ni) contained in the complex transition metal hydroxide and the number of moles of lithium (Li) contained in Li2CO3 (Mn+Ni):Li, such that the ratio (Mn+Ni):Li was 1:0.97 and (Mn+Ni):Al was 1:0.01. The mixture was first calcined at 960°C for 18 hours under an oxygen atmosphere to produce a first calcined product.

[0146] The above primary calcined product, Al(OH)30.5 mol%, TiO20.2 mol%, WO30.2 mol%, and ZrO20.2 mol% were mixed, and LiOH was further mixed so that the ratio of the total number of moles of transition metals (Mn+Ni) contained in the primary calcined product to the number of moles of lithium (Li) contained in LiOH ((Mn+Ni):Li) was 1:1.05 to prepare a mixture. The above mixture was secondarily calcined at 860°C for 20 hours under an oxygen atmosphere to prepare an anode active material.

[0148] Comparative Example 1

[0149] The above Example 1 was prepared in the same manner as Example 1, except that in the first calcination, LiOH was mixed instead of Li2CO3 so that the (Mn+Ni):Li ratio was 1:0.97, and in the second calcination, Al(OH)3, TiO2, WO3, and ZrO2 were not added.

[0150] Complex transition metal hydroxide (Composition: Mn 0.23 Ni 0.77 (OH)2, D 50 A mixture was prepared by mixing LiOH and Al(OH)3 with the total number of moles of transition metal (Mn+Ni) contained in the complex transition metal hydroxide and the number of moles of lithium (Li) contained in LiOH (Mn+Ni):Li) such that the ratio (Mn+Ni):Li was 1:0.97 and (Mn+Ni):Al was 1:0.01. The mixture was first calcined at 960°C for 18 hours under an oxygen atmosphere to produce a first calcined product.

[0151] A mixture was prepared by further mixing the above primary calcined product and LiOH such that the ratio of the total number of moles of transition metals (Mn+Ni) contained in the primary calcined product to the number of moles of lithium (Li) contained in LiOH ((Mn+Ni):Li) was 1:1.05. The above mixture was secondarily calcined at 860°C for 20 hours under an oxygen atmosphere to prepare an anode active material.

[0154] Comparative Example 2

[0155] Complex transition metal hydroxide (Composition: Mn 0.23 Ni 0.77 (OH)2, D 50A mixture was prepared by mixing LiOH and Al(OH)3 with the total number of moles of transition metal (Mn+Ni) contained in the complex transition metal hydroxide and the number of moles of lithium (Li) contained in LiOH (Mn+Ni):Li) such that the ratio (Mn+Ni):Li was 1:0.97 and (Mn+Ni):Al was 1:0.01. The mixture was first calcined at 960°C for 18 hours under an oxygen atmosphere to produce a first calcined product.

[0156] The above primary calcined product, Al(OH)30.5 mol%, TiO20.2 mol%, WO30.2 mol%, and ZrO20.2 mol% were mixed, and LiOH was further mixed so that the ratio of the total number of moles of transition metals (Mn+Ni) contained in the primary calcined product to the number of moles of lithium (Li) contained in LiOH ((Mn+Ni):Li) was 1:1.05 to prepare a mixture. The above mixture was secondarily calcined at 860°C for 20 hours under an oxygen atmosphere to prepare an anode active material.

[0158] Experimental Example

[0159] Experimental Example 1: ICP Analysis

[0160] 0.1 g of each cathode active material prepared in the examples and comparative examples was taken, 1 ml of hydrochloric acid was added, and the cathode active material was dissolved by heating. Subsequently, a small amount of hydrogen peroxide was added to promote the reaction and completely dissolve the cathode active material to prepare a solution. Then, the solution was diluted with deionized water to a total volume of 10 ml to prepare an analytical sample. Using an ICP device (ICP-OES; Agilent 5110, Agilent Technologies), the weight ratio of constituent elements present in the analytical sample was measured, and the composition of the cathode active material, the content of Al (ppm), Ti (ppm), and W (ppm) present in the cathode active material are shown in Table 1 below.

[0161] division Antenna active material composition Example 1 Li 1.049 Mn 0.247 Ni 0.732 Al 0.015 Ti 0.002 W 0.002 Zr 0.002 O2 Comparative Example 1 Li 1.047 Mn 0.249 Ni 0.761 Al 0.01 O2 Comparative Example 2 Li 1.049 Mn 0.247 Ni 0.732 Al 0.015 Ti 0.002 W 0.002 Zr 0.002 O2

[0162] Referring to Table 1 above, it can be seen that the positive active material (lithium composite transition metal oxide) of Example 1 has a composition represented by Chemical Formula 1 described in this specification and includes Al, Ti, and W as doping elements.

[0164] Experimental Example 2: Analysis of Anode Active Material Shape

[0165] SEM images of each cathode active material prepared in the examples and comparative examples were obtained using an SEM (FEI, Inspect F), and are shown in FIG. 1 (Example 1), FIG. 2 (Comparative Example 1), and FIG. 3 (Comparative Example 2).

[0167] Referring to Fig. 1, it can be seen that the positive active material of Example 1 is in the form of a single particle.

[0169] Experimental Example 3: Analysis of Cathode Active Material Particle Size

[0170] 0.01 g of each cathode active material (powder) prepared in the examples and comparative examples was taken, placed in a vial containing 30 ml of ultrapure water and 500 µl of dispersant, dispersed using a sonicator for 1 minute, then placed in a PSA (Microtrac, S3500) and analyzed, D 50 We verified this and showed it in Table 2 below.

[0171] At this time, D 50 It refers to the particle size at the 50% point of the volume cumulative distribution according to particle size.

[0172] division D 50 (㎛) Example 1 3.68 Comparative Example 1 3.57 Comparative Example 2 3.60

[0174] Experimental Example 4: STEM-EDS Analysis

[0175] HAADF-STEM images and EDS data of the cross-sections of the cathode active materials prepared in Example 1 and Comparative Example 2 were obtained using a TFS Spectra300, quadruple EDS detector (acceleration voltage: 200 kV), and these are shown in FIG. 4 (Example 1) and FIG. 5 (Comparative Example 2).

[0177] Referring to Figures 4 and 5, it can be seen that the positive electrode active material of Example 1 has a higher concentration of Al, Ti, and W in the surface portion than in the core portion, and in the surface portion, there is a region of 15 nm to 25 nm from the surface of the lithium nickel-based oxide particles toward the center of the particles in which the concentration of Ti and W is higher than in other regions of the surface portion, whereas the positive electrode active material of Comparative Example 2 does not have a region in which the concentration of Ti and W is higher than in other regions of the surface portion.

[0179] Experimental Example 5: HR-STEM Analysis

[0180] For each cathode active material prepared in Example 1 and Comparative Example 2, HR-(S)TEM image analysis was performed and the results are shown in FIG. 6 (Example 1) and FIG. 7 (Comparative Example 2).

[0181] Specifically, HR-(S)TEM analysis was performed using a Thermo Fisher Scientific Spectra 300 (w / double Cs corrector, monochromator) at an acceleration voltage of 200 kV, and STEM was performed under conditions of a screen current of ~20 pA.

[0183] Referring to FIGS. 6 and 7, in the positive electrode active material of Example 1, a monoclinic phase by Ti and W is observed in a region of 15 nm to 25 nm from the surface of the lithium nickel-based oxide particles toward the center of the particles, where the concentration of Ti and W is higher than in other regions of the surface, whereas in the positive electrode active material of Comparative Example 2, it can be confirmed that it consists only of the R-3m structure of a general positive electrode active material.

[0185] Experimental Example 5: Evaluation of Battery Characteristics

[0186] - Evaluation of gas generation during high-temperature storage

[0187] An anode slurry was prepared by mixing 95.7 wt% of each anode active material prepared in the examples and comparative examples, 2 wt% of carbon black as a conductive material, and 2.3 wt% of polyvinylidene fluoride (PVDF) as a binder in an N-methylpyrrolidone (NMP) solvent. The anode slurry was applied to one side of an aluminum current collector, dried at 130°C, and then rolled to produce an anode.

[0188] An electrode assembly was manufactured by using graphite as the cathode and interposing a porous polyethylene separator between the anode and the cathode. The electrode assembly was placed inside a battery case, and a monocell was manufactured by injecting an electrolyte (additives: LiBF 40.2%, Esa 1%, LiFSI 0.3M, LiPF6 0.7M) in which 1M LiPF6 was dissolved in an organic solvent mixed with ethylene carbonate (EC):ethyl methyl carbonate (EMC) in a volume ratio of 3:7.

[0190] The above monocell was charged to 4.35V at 25°C under CC (0.1C)-CV (Cut-off current: 0.05C) conditions, discharged to 2.5V at 0.1C, and then charged to 4.35V under CC (0.1C)-CV (Cut-off current: 0.05C) conditions. Afterward, only the positive electrodes were removed from three monocells, washed with DMC (Di Methyl Carbonate), placed in a single pouch, 400 μm of electrolyte was injected, sealed, and stored in a chamber at 60°C. Starting two weeks after storage, the monocells were removed from the chamber at intervals of two and four weeks, and the difference between the original weight of the monocell and its weight in water was measured using a hydrometer (MATSUHAKU, TWD-150DM). The change in volume within the monocell was calculated, and the results are shown in Table 3 below.

[0191] division Volume change (%) Change rate (%) compared to Comparative Example 1 2 weeks 4 weeks Example 1 30.5 31.8 22.5 Comparative Example 1 95.5 141.1 100 Comparative Example 2 47.7 44.8 31.7

[0193] - Electrochemical performance evaluation

[0194] An anode slurry was prepared by mixing 95.7 wt% of each anode active material prepared in the examples and comparative examples, 2 wt% of carbon black as a conductive material, and 2.3 wt% of polyvinylidene fluoride (PVDF) as a binder in an N-methylpyrrolidone (NMP) solvent. The anode slurry was applied to one side of an aluminum current collector, dried at 130°C, and then rolled to produce an anode.

[0195] An electrode assembly was manufactured by using a lithium metal electrode as the negative electrode and interposing a porous polyethylene separator between the positive electrode and the negative electrode. The electrode assembly was placed inside a battery case, and a half-cell was manufactured by injecting an electrolyte (additives: vinyl carbonate (VC) 3%, protansulfone (PS) 0.5%, ethylene sulfate (ESA) 1%) in which 1M LiPF6 was dissolved in an organic solvent mixed with ethylene carbonate (EC):ethyl methyl carbonate (EMC):dimethyl carbonate (DMC) in a volume ratio of 3:3:4.

[0197] The above half-cell was charged to 4.4V at 25°C under CC (0.1C)-CV (Cut-off current: 0.05C) conditions, and then discharged to 2.5V at 0.1C (hereinafter referred to as the Formation cycle) to perform an activation process (formation). The half-cell that underwent the above activation process was charged to 4.4V at 25°C under CC (0.1C)-CV (Cut-off current: 0.05C) conditions, and then discharged to 2.5V at 0.1C (hereinafter referred to as 0 th After completing a cycle, the voltage was charged to 4.4V under CC (0.5C) - CV (Cut-off current: 0.05C) conditions, and then discharged to 2.5V at 2C to measure the 2C discharge capacity. Subsequently, the process of charging to 4.4V under CC (0.1C) - CV (Cut-off current: 0.05C) conditions at 45℃ and then discharging to 2.5V at 0.1C was repeated for 50 cycles (1 st Cycle ~ 50 th cycled.

[0198] At this time, 1 st Cycle and 50 th Resistance during a cycle and the resistance increase rate (= 1 st 50 for resistance during cycling th The percentage of resistance during a cycle was checked and shown in Table 4 below.

[0199] division 1 st Resistance (Ω) during a cycle 50 th Resistance (Ω) during a cycle Resistance increase rate (%) Example 1 18.7 27.4 146.9 Comparative Example 1 22.2 30.9 139.2 Comparative Example 2 17.9 27.2 151.6

[0201] Referring to Tables 3 and 4 above, it can be confirmed that the positive electrode active material of Example 1 has significantly less gas generation even during high-temperature storage, and that it has excellent lifespan characteristics due to the low rate of resistance increase during repeated cycles.

[0202] Meanwhile, the positive electrode active material of Comparative Example 1 does not contain Al, Ti, and W, so it can be confirmed that not only is the amount of gas generated significantly high during high-temperature storage, but the initial resistance of the battery containing the positive electrode active material is also high. Furthermore, the positive electrode active material of Comparative Example 2 does not have a region in the surface portion where the concentration of Ti and W is higher than other regions in the area of ​​15 nm to 25 nm from the surface of the lithium nickel-based oxide particles toward the center of the particles, so it can be confirmed that the effect of improving gas generation characteristics is small compared to the positive electrode active material of Example 1, and the resistance increase rate is high.

Claims

Claim 1 A positive electrode active material comprising a lithium nickel-based oxide particle in a single particle form, the core portion; and a surface portion formed on the core portion; wherein the single particle form is a single particle form consisting of one primary particle or a form formed by aggregating two to ten primary particles; wherein the lithium nickel-based oxide particle is doped with a doping element including aluminum (Al), titanium (Ti), and tungsten (W); wherein the surface portion has a higher concentration of Al, Ti, and W than the core portion; and wherein the surface portion has a region in which the concentration of Ti and W is higher than other regions of the surface portion in an area of ​​15 nm to 25 nm from the surface of the lithium nickel-based oxide particle toward the center of the particle. Claim 2 A positive electrode active material according to claim 1, wherein the surface portion is a region within 30 nm from the surface toward the center of the particle on the surface of the lithium nickel-based oxide particle. Claim 3 A positive active material according to claim 1, wherein the surface portion comprises a monoclinic phase (C2 / m). Claim 4 A positive electrode active material according to claim 1, wherein the lithium nickel-based oxide has a cobalt (Co) content of 10 mol% or less among the total transition metals. Claim 5 A positive electrode active material according to claim 1, wherein the lithium nickel-based oxide does not contain cobalt (Co). Claim 6 A positive electrode active material according to claim 1, wherein the lithium nickel-based oxide has a composition represented by the following chemical formula 1: [Chemical Formula 1]Li 1+x1 Mn a1 Ni b1 Al c1 Ti d1 W e1 M 1 f1 O 2-y1 A y1 In the above chemical formula 1, M 1 ... is one or more selected from Zr, Y, Cu, Sr, Mn, Mg, Mo, B, Sn, Fe, Zn, and Si, and A is one or more selected from F, Cl, Br, I, and S, and -0.1≤x1≤0.1, 0 <a1<1, 0<b1<1, 0<c1≤0.1 0<d1≤0.1, 0<e1≤0.1, 0≤f1<0.1, 0≤y1≤0.2이다. Claim 7 A positive electrode comprising a positive electrode active material according to any one of claims 1 to 6. Claim 8 A lithium secondary battery comprising: a positive electrode according to claim 7; a negative electrode; a separator interposed between the positive electrode and the negative electrode; and an electrolyte.

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