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

Abstract

The present invention relates to a positive electrode active material capable of implementing a battery with improved initial capacity characteristics and lifespan characteristics, and a positive electrode and a lithium secondary battery comprising same, wherein the positive electrode active material comprises a lithium nickel-based oxide and has an average KAM value (total sum of KAM values of all pixels] / [total number of pixels]) of 0° (exclusive) to 1.0° (inclusive), obtained from a kernel average misorientation map (KAM Map) derived from electron backscatter diffraction (EBSD) analysis.

Description

Cathode active material, cathode and lithium secondary battery containing same

[0001] Cross-citation with related applications

[0002] This application claims the benefit of priority from Korean Patent Application No. 10-2024-0113969, filed August 26, 2024, the entire contents of which are incorporated herein by reference.

[0003] Technology field

[0004] The present invention relates to a positive electrode active material, a positive electrode including the same, and a lithium secondary battery.

[0005]

[0006] With the recent increase in technological development and demand for mobile devices and electric vehicles, the demand for secondary batteries as an energy source is rapidly increasing.

[0007] A lithium secondary battery is generally composed of a positive electrode, a negative electrode, a separator, and an electrolyte, and the positive electrode and negative electrode include an active material capable of intercalation and deintercalation of lithium ions.

[0008] Meanwhile, the cathode active material used in lithium secondary batteries is typically manufactured by mixing a cathode active material precursor with a lithium raw material and then firing it. However, this process poses the problem of local strain and deformation within the cathode active material particles due to various factors. Specifically, the cathode active material can experience subtle lattice changes as crystal planes are pushed (glided) or distorted during particle growth or by external stimuli.

[0009] Meanwhile, when intra-particle stress and strain are high, deformation can easily occur due to external physical and / or chemical reactions, thereby accelerating degradation. Therefore, it is necessary to control the particle properties to reduce intra-particle stress and strain.

[0010]

[0011] The object of the present invention is to provide a cathode active material capable of implementing a battery with improved initial capacity characteristics and lifespan characteristics, and a cathode including the same.

[0012]

[0013] To solve the above problem, the present invention provides a positive electrode active material, and a positive electrode and a lithium secondary battery including the same.

[0014]

[0015] (1) The present invention provides a cathode active material including a lithium nickel-based oxide, wherein an average KAM value ([sum of KAM values ​​of all pixels] / [total number of pixels]) obtained from a Kernel Average Misorientation Map (KAM Map) obtained from electron backscatter diffraction (EBSD) analysis is greater than 0° and less than or equal to 1.0°.

[0016] (2) The present invention provides a positive electrode active material in (1) above, wherein the lithium nickel-based oxide has a nickel content of 60 mol% or more among all metals excluding lithium.

[0017] (3) The present invention provides a positive electrode active material in (1) or (2), wherein the lithium nickel-based oxide has a composition represented by the following chemical formula 1.

[0018] [Chemical Formula 1]

[0019] Li x Ni a Co b M 1 c M 2 d O2

[0020] In the above chemical formula 1,

[0021] M 1 is Mn, Al or a combination thereof,

[0022] M2 is at least one selected from the group consisting of Zr, Y, Mo, B, W, Ti, V, Ce, Hf, La, Ba, F, P, S, Nb, Ta, Sc and Cr,

[0023] 0.9≤x≤1.1, 0.6≤a<1, 0 <b<0.4, 0<c<0.4, 0≤d≤0.2이다.

[0024] (4) The present invention provides a positive electrode active material having a KAM value of 0° or more and 5° or less in any one of the above (1) to (3).

[0025] (5) The present invention provides a positive electrode active material in any one of the above (1) to (4), wherein the lithium nickel-based oxide is in the form of a single particle or a secondary particle.

[0026] (6) The present invention relates to an average particle diameter (D) in any one of the above (1) to (5) 50 ) provides a positive electrode active material having a diameter of 1㎛ or more and 30㎛ or less.

[0027] (7) The present invention provides a positive electrode active material according to any one of the above (1) to (6), wherein the positive electrode active material further includes a coating layer formed on the lithium nickel-based oxide, and the coating layer includes at least one selected from the group consisting of Zr, Y, Mo, B, W, Ti, V, Ce, Hf, La, Ba, F, P, S, Nb, Ta, Sc and Cr.

[0028] (8) The present invention provides a positive electrode comprising a positive electrode active material according to any one of (1) to (7).

[0029] (9) The present invention provides a lithium secondary battery including a positive electrode according to (8).

[0030]

[0031] The cathode active material according to the present invention has less stress and strain within the particles, and thus can improve the initial capacity characteristics and life characteristics of a battery including the cathode active material.

[0032]

[0033] Figure 1 is a KAM Map obtained from EBSD analysis of the positive electrode active material of Example 1.

[0034] Figure 2 is a KAM Map obtained from EBSD analysis of the positive electrode active material of Example 2.

[0035] Figure 3 is a KAM Map obtained from EBSD analysis of the positive electrode active material of Example 3.

[0036] Figure 4 is a KAM Map obtained from EBSD analysis of the positive electrode active material of Example 4.

[0037] Figure 5 is a KAM Map obtained from EBSD analysis of the positive electrode active material of Comparative Example 1.

[0038]

[0039] Terms or words used in this specification and claims should not be interpreted as limited to their usual or dictionary meanings, but should be interpreted as meanings and concepts that conform to the technical spirit of the present invention, based on the principle that the inventor can appropriately define the concept of the term to explain his or her own invention in the best possible manner.

[0040] It should be understood that the terms “include,” “comprising,” or “having” used in this specification are intended to specify the presence of a feature, number, step, component, or combination thereof, but do not preclude the possibility of the presence or addition of one or more other features, numbers, steps, components, or combinations thereof.

[0041] The term "on" in this specification means not only when a configuration is formed directly on top of another configuration, but also when a third configuration is interposed between these configurations.

[0042] In this specification, the term "single-particle positive electrode active material" refers to a positive electrode active material composed of 50 or fewer single-crystal particles, as opposed to a spherical secondary particle-shaped positive electrode active material formed by agglomeration of hundreds of primary particles manufactured by a conventional method. Specifically, the single-particle positive electrode active material in the present invention may be a single single-crystal particle, or may be an aggregate of 2 to 50, 2 to 40, 2 to 30, 2 to 20, 2 to 15, 2 to 10, or 2 to 5 single-crystal particles. In this case, "primary particle" refers to the smallest particle unit recognized when the positive electrode active material is observed through a scanning electron microscope.

[0043] In this specification, the average particle diameter (D 50 ) means the particle size based on 50% of the volume cumulative particle size distribution of the positive electrode active material precursor, positive electrode active material or lithium nickel oxide powder. The average particle diameter (D 50 ) can be measured using a laser diffraction method. For example, after dispersing the positive electrode active material powder in a dispersion medium, it can be measured by introducing it into a commercially available laser diffraction particle size measuring device (e.g., Microtrac MT 3000), irradiating it with ultrasonic waves of about 28 kHz at an output of 60 W, obtaining a volume cumulative particle size distribution graph, and then finding the particle size corresponding to 50% of the volume cumulative amount.

[0044]

[0045] Hereinafter, the present invention will be described in detail.

[0046]

[0047] positive electrode active material

[0048] The present invention provides a cathode active material including a lithium nickel-based oxide, wherein an average KAM value ([sum of KAM values ​​of all pixels] / [total number of pixels]) obtained from a Kernel Average Misorientation Map (KAM Map) obtained from electron backscatter diffraction (EBSD) analysis is greater than 0° and less than or equal to 1.0°.

[0049]

[0050] The inventors of the present invention have found that when a cathode active material includes a lithium nickel-based oxide and an average KAM value ([sum of KAM values ​​of all pixels] / [total number of pixels]) obtained from an electron backscatter diffraction (EBSD) analysis satisfies a range of more than 0° and less than 1.0°, the stress and strain within the particle are reduced, thereby improving the initial capacity characteristics and life characteristics of the battery, and have completed the present invention.

[0051] The Kernel Average Misorientation Map (KAM Map) obtained from the above electron backscatter diffraction (EBSD) analysis has an image size of 5 to 500 ㎛ × 5 to 500 ㎛ (width × height). In addition, the KAM Map has a resolution (number of pixels constituting the image) of 200 to 2,000 × 200 to 2,000 (number of horizontal pixels × number of vertical pixels), and the total number of pixels constituting the image is 40,000 to 4,000,000. An appropriate range for each of the number of horizontal pixels and the number of vertical pixels may be 250 to 1,500 or less.

[0052] In the present invention, a pixel is the smallest unit that constitutes an image of a display.

[0053]

[0054] The above KAM (Kernel Average Misorientation) value is the average of the decision orientation differences between the center pixel and its surrounding neighboring pixels for each pixel, and the above average KAM value can be obtained by dividing the KAM values ​​of all pixels obtained from the Kernel Average Misorientation Map (KAM Map) by the total number of pixels.

[0055] According to the present invention, the average KAM value may be greater than 0°, greater than 0.10°, greater than 0.20°, greater than 0.30°, greater than 0.31°, greater than 0.32°, greater than 0.33°, greater than 0.34°, greater than 0.35°, greater than 0.36°, or greater than 0.37°, and may be less than or equal to 0.51°, less than or equal to 0.52°, less than or equal to 0.53°, less than or equal to 0.54°, less than or equal to 0.55°, less than or equal to 0.56°, less than or equal to 0.57°, less than or equal to 0.58°, less than or equal to 0.59°, less than or equal to 0.60°, less than or equal to 0.70°, less than or equal to 0.80°, less than or equal to 0.90°, or less than or equal to 1.0°. The average KAM value may preferably be greater than 0° and less than or equal to 0.60°.

[0056] Meanwhile, when the average KAM value exceeds 1.0°, the deformation within the particle is high, which reduces structural stability during electrochemical reaction, causing problems such as reduced capacity and lifespan, increased resistance, and increased gas.

[0057]

[0058] According to the present invention, the KAM value may be 0° or more and 5° or less. In this case, deformation within a specific angle based on the center pixel can be maintained, the structural stability of the particle can be maintained, and the electrochemical properties can be improved.

[0059]

[0060] According to the present invention, the lithium nickel-based oxide may have a nickel content of 60 mol% or more, 70 mol% or more, 80 mol% or more, or 85 mol% or more among all metals excluding lithium. In this case, the capacity characteristics of a battery including the positive electrode active material may be improved. The lithium nickel-based oxide may be a positive electrode material having a layered structure.

[0061] According to the present invention, the lithium nickel-based oxide may have a composition represented by the following chemical formula 1.

[0062] [Chemical Formula 1]

[0063] Li x Ni a Co b M 1 c M 2 d O2

[0064] In the above chemical formula 1,

[0065] M 1 is Mn, Al or a combination thereof,

[0066] M 2 is at least one selected from the group consisting of Zr, Y, Mo, B, W, Ti, V, Ce, Hf, La, Ba, F, P, S Nb, Ta, Sc and Cr,

[0067] 0.9≤x≤1.1, 0.6≤a<1, 0 <b<0.4, 0<c<0.4, 0≤d≤0.2이다.

[0068] The above x may be 0.9 or more, 0.95 or more, 0.98 or more, or 1.0 or more, and 1.01 or less, 1.02 or less, 1.05 or less, or 1.1 or less. In this case, the structural stability may be improved so that the lithium ion movement path may not be restricted.

[0069] The above a refers to the atomic fraction of nickel among all metals excluding lithium, and may be 0.60 or more, 0.65 or more, 0.8 or more, or 0.85 or more, and may be 0.95 or less, 0.98 or less, or less than 1.0. In this case, the capacity can be improved with a high energy density.

[0070] The above b refers to the atomic fraction of cobalt among all metals excluding lithium, and may be 0.01 or more, 0.10 or less, 0.20 or less, 0.30 or less, or less than 0.40.

[0071] The above c is M among all metals except lithium 1 It means the atomic fraction of , which can be 0.01 or more, 0.10 or less, 0.20 or less, 0.30 or less, or less than 0.40.

[0072] The above d is M among all metals except lithium 2 It means the atomic fraction of , which can be 0 or more, 0.02 or less, 0.05 or less, 0.10 or less, or 0.20 or less. In this case, the structural stability can be further improved, and the capacity and lifespan can be improved.

[0073] Above M 1 When including this Al, the content of aluminum may be 500 ppm to 3000 ppm relative to the total weight of the lithium nickel-based oxide.

[0074] Above M 2 It may preferably be Zr, Y or a combination thereof. At this time, the content of yttrium may be 100 ppm to 2000 pm based on the total weight of the lithium nickel-based oxide. And, the content of zirconium may be 500 ppm to 5000 pm based on the total weight of the lithium nickel-based oxide.

[0075]

[0076] According to the present invention, the lithium nickel-based oxide may be in the form of a single particle or a secondary particle. When the lithium nickel-based oxide is in the form of a single particle, the crystal grain boundaries are smaller than those of the secondary particles, and structural stability is enhanced, thereby improving the life characteristics of the battery and reducing the amount of gas generated. In addition, when the lithium nickel-based oxide is in the form of a secondary particle, lithium ions can easily move through the crystal grain boundaries, thereby improving the initial resistance of the battery.

[0077]

[0078] According to the present invention, the positive electrode active material has an average particle diameter (D 50 ) may be 1㎛ or more and 30㎛ or less. The average particle diameter (D) of the positive electrode active material 50 ) can be specifically 1㎛ or more, 2㎛ or more, 3㎛ or more, or 3.5㎛ or more, and can be 10㎛ or less, 11㎛ or less, 12㎛ or less, 13㎛ or less, 14㎛ or less, 15㎛ or less, 16㎛ or less, 17㎛ or less, 18㎛ or less, 19㎛ or less, 20㎛ or less, 25㎛ or less, or 30㎛ or less. In this case, the performance of the battery can be improved by increasing the positive electrode rolling density.

[0079]

[0080] According to the present invention, the positive electrode active material further includes a coating layer formed on the lithium nickel-based oxide, and the coating layer may include at least one selected from the group consisting of Zr, Y, Mo, B, W, Ti, V, Ce, Hf, La, Ba, F, P, S, Nb, Ta, Sc, and Cr. The coating layer may preferably include Co, Al, and / or B.

[0081] Meanwhile, when the coating layer includes Co, the content of cobalt may be 1 mol% to 3 mol% relative to the molar number of metal elements other than lithium present in the lithium nickel-based oxide.

[0082] Additionally, when the coating layer includes Al, the content of aluminum may be 200 ppm to 3000 ppm relative to the total weight of the lithium nickel-based oxide.

[0083] Additionally, when the coating layer includes B, the content of boron may be 200 ppm to 3000 ppm relative to the total weight of the lithium nickel-based oxide.

[0084]

[0085] The lattice of the cathode active material can be induced to change slightly as the crystal plane is pushed (glided) or distorted during particle growth or by external stimuli.

[0086] The inventors of the present invention controlled the positive electrode active material to have an average KAM value ([sum of KAM values ​​of all pixels] / [total number of pixels]) obtained from a Kernel Average Misorientation Map (KAM Map) obtained from electron backscatter diffraction (EBSD) analysis exceeding 0° and 1.0° or less through the following manufacturing method.

[0087]

[0088] The cathode active material according to the present invention can be manufactured by a manufacturing method comprising: (A) a step of mixing a cathode active material precursor with a lithium raw material, and then performing a first firing at a temperature of 700°C to 1000°C in an air atmosphere or an oxygen atmosphere to obtain a first fired product; (B) a step of pulverizing the first fired product, and then performing a second firing at a temperature of 700°C to 1100°C to obtain a second fired product; and (C) a step of optionally mixing a coating raw material after pulverizing the second fired product, and then performing a heat treatment at a temperature of 300°C to 900°C.

[0089] According to the present invention, the step (C) may be (i) crushing the secondary sintered product and then heat-treating it at a temperature of 300°C to 900°C, or (ii) crushing the secondary sintered product and then mixing the coating raw material and heat-treating it at a temperature of 300°C to 900°C.

[0090]

[0091] According to the present invention, the positive electrode active material precursor may have a composition represented by the following chemical formula 2.

[0092] [Chemical Formula 2]

[0093] Ni a' Co b' Mn c' M 3 d' (OH)2

[0094] In the above chemical formula 2,

[0095] M 3 is at least one selected from the group consisting of Al, Zr, Y, Mo, B, W, Ti, V, Ce, Hf, La, Ba, F, P, S Nb, Ta, Sc and Cr,

[0096] 0.6≤a'<1, 0 <b'<0.4, 0<c'<0.4, 0≤d'≤0.2이다.

[0097] According to the present invention, the lithium raw material may be a lithium-containing sulfate, nitrate, acetate, carbonate, oxalate, citrate, halide, hydroxide or oxyhydroxide, and for example, Li2CO3, LiNO3, LiNO2, LiOH, LiOH H2O, LiH, LiF, LiCl, LiBr, LiI, CH3COOLi, Li2O, Li2SO4, CH3COOLi, Li3C6H5O7 or a mixture thereof.

[0098]

[0099] According to the present invention, when mixing the positive electrode active material precursor with the lithium raw material, a doping raw material can be further mixed.

[0100] The above doping raw material may be at least one selected from the group consisting of Al, Zr, Y, Mo, B, W, Ti, V, Ce, Hf, La, Ba, F, P, S, Nb, Ta, Sc, and Cr. Preferably, the above doping raw material may include Y, Zr, and / or Al doping elements.

[0101] Meanwhile, when the doping element is Y, the yttrium raw material can be mixed in an amount such that the yttrium in the final cathode active material is 100 ppm to 2000 ppm based on the total weight of the lithium nickel-based oxide.

[0102] Additionally, when the doping element is Zr, the zirconium raw material may be mixed in an amount such that the zirconium in the final cathode active material is 500 ppm to 5000 ppm based on the total weight of the lithium nickel-based oxide.

[0103] Additionally, when the doping element is Al, the aluminum raw material may be mixed in an amount such that aluminum in the final positive electrode active material is 500 ppm to 3000 ppm based on the total weight of the lithium nickel-based oxide.

[0104]

[0105] According to the present invention, particles are formed through the first firing, and the density of the crystals is further increased through the second firing.

[0106]

[0107] According to the present invention, the primary calcination can be performed for 5 to 20 hours. In this case, the particles can sufficiently grow, thereby forming a positive electrode active material with excellent electrochemical properties.

[0108]

[0109] According to the present invention, the reason for pulverizing the primary sintered product is to appropriately control the particle size and shape of the particles by disintegrating the agglomerated positive electrode materials. The pulverization of the primary sintered product can be performed using a jet mill pulverizer, a ball mill pulverizer, a pin mill pulverizer, etc. At this time, the pulverization pressure, the feeding speed, the stirring speed, etc. can be adjusted to control the positive electrode active material to have the desired particle size and shape. Specifically, the pulverization of the primary sintered product can be performed under a pulverization pressure of 1.5 bar to 2.5 bar and a feeding speed of 600 rpm to 1200 rpm. In addition, the pulverization of the primary sintered product can be performed under a stirring speed of 10,000 rpm to 20,000 rpm. For reference, when a pin mill pulverizer is used, there are no separate pulverization pressure and feeding speed conditions, so the particle size and shape of the positive electrode active material can be controlled by adjusting the stirring speed.

[0110]

[0111] According to the present invention, the secondary firing can be performed for 5 to 20 hours. In this case, structural and morphological stability of the particles can be induced, thereby forming a positive electrode active material with excellent electrochemical properties.

[0112] The above secondary firing can be performed under an oxygen atmosphere.

[0113]

[0114] According to the present invention, the reason for crushing the secondary sintered product is to appropriately control the particle size and shape of the particles by crushing the agglomerated positive electrode materials. The crushing of the secondary sintered product can be performed using a jet mill crusher, a ball mill crusher, a pin mill crusher, etc. At this time, the crushing pressure and the feeding speed can be adjusted to control the positive electrode active material to have the desired particle size and shape. Specifically, the crushing of the primary sintered product can be performed under a crushing pressure of 1.5 bar to 2.5 bar and a feeding speed of 600 rpm to 1200 rpm. In addition, the crushing of the secondary sintered product can be performed under a stirring speed of 10,000 rpm to 20,000 rpm.

[0115]

[0116] According to the present invention, the coating raw material may include coating elements such as Co, Al, and B.

[0117] Meanwhile, when the coating element is Co, the coating raw material may be cobalt hydroxide such as Co(OH)2, and the cobalt raw material may be mixed in an amount such that cobalt in the final positive electrode active material is 1 mol% to 3 mol% relative to the molar number of metal elements other than lithium present in the lithium nickel-based oxide.

[0118] Additionally, when the coating element is Al, the aluminum raw material may be aluminum hydroxide such as Al(OH)3, and the aluminum raw material may be mixed in an amount such that aluminum in the final positive electrode active material is 200 ppm to 3000 ppm based on the total weight of the lithium nickel-based oxide.

[0119] Additionally, when the coating element is B, the boron source material may be H3BO3, and the boron source material may be mixed in an amount such that boron in the final positive electrode active material is 200 ppm to 3000 ppm based on the total weight of the lithium nickel-based oxide.

[0120]

[0121] According to the present invention, the heat treatment can be performed for 1 to 20 hours. In this case, the crystallinity of the particle surface can be increased, thereby forming a positive electrode active material with excellent electrochemical properties.

[0122] The above heat treatment can be performed under an air atmosphere.

[0123]

[0124] According to the present invention, when the first firing, second firing, and heat treatment temperatures are exceeded, the layered structure of the positive electrode active material may not grow completely or crystallite growth may not occur properly, resulting in high misorientation within the interface or crystallite.

[0125]

[0126] anode

[0127] The present invention provides a positive electrode comprising the positive electrode active material.

[0128] According to one embodiment of the present invention, the 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.

[0129] According to one embodiment of the present invention, the positive electrode current collector may include a highly conductive metal, and is not particularly limited as long as it is easily adhered to by the positive electrode active material layer and does not react within the voltage range of the battery. The positive electrode current collector may be made of, for example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, etc. In addition, the positive electrode current collector may typically have a thickness of 3 ㎛ to 500 ㎛, and fine unevenness may be formed on the surface of the current collector to increase the adhesive strength of the positive electrode active material. For example, the positive electrode current collector may 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.

[0130] According to one embodiment of the present invention, the positive electrode active material layer may optionally include a conductive material and a binder, together with the positive electrode active material, as needed. In this case, the positive electrode active material may be included in an amount of 80 wt% to 99 wt%, more specifically 85 wt% to 98.5 wt%, based on the total weight of the positive electrode active material layer, and excellent capacity characteristics may be exhibited within this range.

[0131] According to one embodiment of the present invention, the conductive material is used to provide conductivity to the electrode, and in the battery to be formed, any conductive material that does not cause a chemical change and has electronic conductivity can be used without particular limitation. 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 fiber; metal powders or metal fibers such as copper, nickel, aluminum, and silver; conductive tubes such as carbon nanotubes; 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 of these may be used alone or a mixture of two or more may be used. The conductive material may be included in an amount of 0.1 wt% to 15 wt% based on the total weight of the positive electrode active material layer.

[0132] According to one embodiment of the present invention, the binder serves to improve adhesion between positive electrode active material particles and adhesion between the positive electrode active material and the current collector. Specific examples include polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylalcohol, polyacrylonitrile, polymethyl methacrylate, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene butadiene rubber (SBR), fluoroelastomer, polyacrylic acid, and polymers in which hydrogens of these are substituted with Li, Na, or Ca, or various copolymers thereof, and one of these may be used alone or a mixture of two or more thereof. The above binder may be included in an amount of 0.1 wt% to 15 wt% based on the total weight of the positive electrode active material layer.

[0133] According to one embodiment of the present invention, the positive electrode can be manufactured according to a conventional positive electrode manufacturing method, except that the positive electrode active material described above is used. Specifically, the positive electrode can be manufactured by applying a composition for forming a positive electrode active material layer, which is manufactured by dissolving or dispersing the positive electrode active material and optionally a binder, a conductive material, and a dispersant in a solvent as needed, onto a positive electrode current collector, followed by drying and rolling, or by casting the composition for forming a positive electrode active material layer onto a separate support, and then laminating the film obtained by peeling it from the support onto a positive electrode current collector.

[0134] According to one embodiment of the present invention, the solvent may be a solvent generally used in the art, such as dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), dimethylformamide (DMF), acetone, or water, and one of these may be used alone or as a mixture of two or more. The amount of the solvent used is sufficient to dissolve or disperse the positive electrode active material, conductive material, binder, and dispersant in consideration of 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.

[0135]

[0136] lithium secondary battery

[0137] The present invention provides a lithium secondary battery including the positive electrode.

[0138]

[0139] According to one embodiment of the present invention, the lithium secondary battery may include the positive electrode; the negative electrode; a separator interposed between the positive electrode and the negative electrode, and an electrolyte. In addition, the lithium secondary battery may optionally further include a battery container that houses the electrode assembly of the positive electrode, the negative electrode, and the separator, and a sealing member that seals the battery container.

[0140] According to one embodiment of the present invention, the negative electrode may include a negative electrode current collector and a negative electrode active material layer positioned on the negative electrode current collector.

[0141] According to one embodiment of the present invention, 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.

[0142] According to one embodiment of the present invention, the negative electrode active material layer may optionally include a binder and a conductive material together with the negative electrode active material.

[0143] According to one embodiment of the present invention, a compound capable of reversible intercalation and deintercalation of lithium may be used as the negative electrode active material. 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 alloy, Sn alloy, or Al alloy; SiO β(0<β<2), SnO2, 바나듐 산화물, 리튬 바나듐 산화물과 같이 리튬을 도프 및 탈도프할 수 있는 금속산화물; 또는 Si-C 복합체 또는 Sn-C 복합체과 같이 상기 금속질 화합물과 탄소질 재료를 포함하는 복합물 등을 들 수 있으며, 이들 중 어느 하나 또는 둘 이상의 혼합물이 사용될 수 있다. 또한, 상기 음극활물질로서 금속 리튬 박막이 사용될 수도 있다. 또한, 탄소재료는 저결정성 탄소 및 고결정성 탄소 등이 모두 사용될 수 있다. 저결정성 탄소로는 연화탄소 (soft carbon) 및 경화탄소 (hard carbon)가 대표적이며, 고결정성 탄소로는 무정형, 판상, 인편상, 구형 또는 섬유형의 천연 흑연 또는 인조 흑연, 키시 흑연 (Kish graphite), 열분해 탄소 (pyrolytic carbon), 액정 피치계 탄소섬유 (mesophase pitch based carbonfiber), 탄소 미소구체 (meso-carbon microbeads), 액정피치 (Mesophase pitches) 및 석유와 석탄계 코크스 (petroleum or coal tar pitch derived cokes) 등의 고온 소성탄소가 대표적이다. 상기 음극 활물질은 음극 활물질층의 전체 중량을 기준으로 80 중량% 내지 99 중량%로 포함될 수 있다.

[0144] According to one embodiment of the present invention, the binder of the negative electrode active material layer is a component that assists in bonding between the conductive material, the active material, and the current collector, and is typically added in an amount of 0.1 wt% to 10 wt% based on the total weight of the negative electrode active material layer. Examples of such binders include polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene-butadiene rubber, nitrile-butadiene rubber, fluororubber, and various copolymers thereof.

[0145] According to one embodiment of the present invention, the conductive material of the 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 wt% or less, preferably 5 wt% or less, based on the total weight of the negative electrode active material layer. The conductive material is not particularly limited as long as it has conductivity without causing a chemical change in the battery, and examples thereof include graphite such as natural graphite or artificial graphite; carbon black such as acetylene black, Ketjen black, channel black, furnace black, lamp black, and thermal black; conductive fibers such as carbon fiber or metal fiber; 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; and conductive materials such as polyphenylene derivatives.

[0146] According to one embodiment of the present invention, the negative electrode can be manufactured by applying and drying a composition for forming a negative electrode active material layer, which is prepared by dissolving or dispersing a negative electrode active material, and optionally a binder and a conductive material in a solvent, on a negative electrode current collector, or by casting the composition for forming a negative electrode active material layer on a separate support, and then laminating the film obtained by peeling it off from the support on a negative electrode current collector.

[0147] According to one embodiment of the present invention, the separator separates the negative electrode and the positive electrode and provides a passage for lithium ions to move. Any separator commonly used in lithium secondary batteries can be used without particular limitation, and in particular, one having low resistance to ion movement of the electrolyte and excellent electrolyte moisture retention capacity is preferable. Specifically, a porous polymer film, for example, a porous polymer film made of a polyolefin polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, and an ethylene / methacrylate copolymer, or a laminated structure of two or more layers thereof, may be used. In addition, a conventional porous nonwoven fabric, for example, a nonwoven fabric made of high-melting-point glass fiber, polyethylene terephthalate fiber, etc. may also be used. In addition, a coated separator containing a ceramic component or a polymer material to secure heat resistance or mechanical strength may be used, and may optionally be used in a single-layer or multi-layer structure.

[0148] According to one embodiment of the present invention, the electrolyte may include, but is not limited to, an organic liquid electrolyte, an inorganic liquid electrolyte, a solid polymer electrolyte, a gel-type polymer electrolyte, a solid inorganic electrolyte, a molten inorganic electrolyte, etc. that can be used in the manufacture of a lithium secondary battery. As a specific example, the electrolyte may include an organic solvent and a lithium salt.

[0149] According to one embodiment of the present invention, the organic solvent may be used without 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), ethylmethylcarbonate (EMC), ethylenecarbonate (EC), and propylene carbonate (PC); alcohol solvents such as ethyl alcohol and isopropyl alcohol; nitriles such as R-CN (where R is a linear, branched, or cyclic hydrocarbon group having 2 to 20 carbon atoms 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.

[0150] According to one embodiment of the present invention, 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 anion of the lithium salt is 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 - At least one selected from the group consisting of may be used, and 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 to use the concentration of the lithium salt within the range of 0.1 M 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.

[0151] According to one embodiment of the present invention, in addition to the electrolyte components, the electrolyte may further include one or more additives, such as, for example, a haloalkylene carbonate compound such as difluoroethylene carbonate, pyridine, triethylphosphite, triethanolamine, a cyclic ether, ethylene diamine, n-glyme, hexaphosphoric acid triamide, nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinones, N,N-substituted imidazolidines, ethylene glycol dialkyl ethers, ammonium salts, pyrrole, 2-methoxyethanol, or aluminum trichloride, for the purpose of improving the life characteristics of the battery, suppressing battery capacity decrease, and improving the discharge capacity of the battery. At this time, the additives may be included in an amount of 0.1 wt% to 5 wt% based on the total weight of the electrolyte.

[0152]

[0153] A lithium secondary battery including a cathode active material according to the present invention stably exhibits excellent initial capacity characteristics and life characteristics, 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) and electric vehicles (EVs).

[0154] There is no particular limitation on the external shape of the lithium secondary battery of the present invention, but it may be a cylindrical shape using a can, a square shape, a pouch shape, or a coin shape.

[0155] 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 be preferably used as a unit battery in a medium- to large-sized battery module including a plurality of battery cells.

[0156] Accordingly, according to one embodiment of the present invention, a battery module including the lithium secondary battery as a unit cell and a battery pack including the same are provided.

[0157] According to one embodiment of the present invention, the battery module or battery pack can be used as a power source for one or more medium- to large-sized devices, such as a power tool; an electric vehicle (EV), a hybrid electric vehicle, and a plug-in hybrid electric vehicle (PHEV); or a power storage system.

[0158]

[0159] 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.

[0160]

[0161] Examples and Comparative Examples

[0162] Example 1

[0163] Ni 0.88 Co 0.05 Mn 0.07 It has a composition represented by (OH)2 and an average particle diameter (D 50 ) was mixed with a positive electrode active material precursor having a diameter of 4.3 μm and LiOH at a molar ratio of 1:1.02, and the first fired product was manufactured by first firing at 720°C for 10 hours in an oxygen atmosphere. The first fired product was pulverized with a pin-mill pulverizer (stirring speed: 18000 rpm), and then second fired at 700°C for 10 hours in an oxygen atmosphere to manufacture LiNi 0.88 Co 0.05 Mn 0.07 A secondary sintered product having a composition represented by O2 was manufactured.

[0164] The above secondary fired product is crushed with a pin-mill crusher (stirring speed: 18000 rpm), the crushed secondary fired product and powdered H3BO3 are mixed in an amount such that B becomes 1000 ppm based on the total weight of the secondary fired product, and heat-treated at 500°C for 5 hours in an air atmosphere to form a coating layer containing boron (B) on a lithium nickel-based oxide in the form of secondary particles, and the average particle diameter (D) is 50 ) was manufactured as a positive electrode active material having a diameter of 4.3㎛.

[0165]

[0166] Example 2

[0167] Ni 0.88 Co 0.03 Mn 0.09 It has a composition represented by (OH)2 and an average particle diameter (D 50 ) was mixed with a positive electrode active material precursor of 3.5㎛ and LiOH in a molar ratio of 1:1.03, and the first fired product was manufactured by first firing at 880°C for 10 hours in an oxygen atmosphere. The first fired product was pulverized with a pin-mill pulverizer (stirring speed: 18000 rpm), and then second fired at 780°C for 9 hours in an oxygen atmosphere to manufacture LiNi 0.88 Co 0.03 Mn 0.09 A secondary sintered product having a composition represented by O2 was manufactured.

[0168] The above secondary calcined product is pulverized with a pin-mill pulverizer (stirring speed: 18,000 rpm), the pulverized secondary calcined product and powdered Co(OH)2 (Huayou Cobalt Co.) are mixed at a molar ratio of 1:0.02, and heat-treated at 700°C for 5 hours in an oxygen atmosphere to form a coating layer containing cobalt (Co) on a lithium nickel oxide in the form of a single particle, LiNi 0.86 Co 0.05 Mn 0.089 It has a composition represented by O2 and an average particle size (D 50 ) was manufactured as a positive electrode active material having a diameter of 3.5㎛.

[0169]

[0170] Example 3

[0171] Ni 0.93 Co 0.04 Mn 0.03 It has a composition represented by (OH)2 and an average particle diameter (D 50 ) was mixed with a positive electrode active material precursor having a diameter of 9.6 μm and LiOH in a molar ratio of 1:1.03, and the first fired product was manufactured by first firing at 910°C for 10 hours in an oxygen atmosphere. The first fired product was pulverized with a pin-mill pulverizer (stirring speed: 18000 rpm), and then second fired at 750°C for 9 hours in an oxygen atmosphere to manufacture LiNi 0.93 Co 0.04 Mn 0.03 A secondary sintered product having a composition represented by O2 was manufactured.

[0172] The above secondary fired product is crushed with a pin-mill crusher (stirring speed: 18000 rpm), the crushed secondary fired product and powdered H3BO3 are mixed in an amount such that B becomes 1000 ppm based on the total weight of the secondary fired product, and heat-treated at 500°C for 5 hours in an air atmosphere to form a coating layer containing boron (B) on a lithium nickel-based oxide in the form of a single particle, and the average particle diameter (D) is 50 ) was manufactured as a positive electrode active material having a diameter of 9.6㎛.

[0173]

[0174] Example 4

[0175] Ni 0.86 Co 0.10 Mn 0.04 It has a composition represented by (OH)2 and an average particle diameter (D 50 ) was mixed with a positive electrode active material precursor having a diameter of 4.2 μm and LiOH in a molar ratio of 1:1.04, and the first fired product was manufactured by first firing at 900°C for 10 hours in an oxygen atmosphere. The first fired product was pulverized with a pin-mill pulverizer (stirring speed: 18000 rpm), and then second fired at 820°C for 9 hours in an oxygen atmosphere to manufacture LiNi 0.86 Co 0.10 Mn0.04 A secondary fired product having a composition represented by O2 was manufactured. The secondary fired product was pulverized with a pin-mill pulverizer (stirring speed: 18,000 rpm) and then heat-treated at 740°C for 5 hours under an oxygen atmosphere to obtain an average particle size (D 50 ) was manufactured as a positive electrode active material (lithium nickel oxide in the form of single particles) with a diameter of 4.2㎛.

[0176]

[0177] Comparative Example 1

[0178] Ni 0.88 Co 0.05 Mn 0.07 It has a composition represented by (OH)2 and an average particle diameter (D 50 ) was mixed with a positive electrode active material precursor having a diameter of 4.3 μm and LiOH at a molar ratio of 1:1.02, and the first fired product was manufactured by first firing at 720°C for 10 hours in an oxygen atmosphere. The first fired product was pulverized with a pin-mill pulverizer (stirring speed: 18000 rpm), and then second fired at 700°C for 9 hours in an oxygen atmosphere to manufacture LiNi 0.88 Co 0.05 Mn 0.07 It has a composition represented by O2 and an average particle size (D 50 ) was manufactured as a positive electrode active material having a diameter of 4.3㎛.

[0179]

[0180] Experimental example

[0181] Experimental Example 1

[0182] Each of the positive electrode active materials manufactured in Examples 1 to 4 and Comparative Example 1, carbon black (Denka, DenkaBlack) as a conductive material, and PVdF (Kureha, KF1300) as a binder were added to a solvent, N-methylpyrrolidone (NMP) (Daejung Chemicals & Metals Co., Ltd.), at a weight ratio of 95:3:2 to manufacture a composition for forming a positive electrode active material layer.

[0183] The composition for forming the positive electrode active material layer was applied to one surface of an aluminum foil current collector having a thickness of 20 μm, and dried at 135°C for 3 hours to manufacture a positive electrode including a positive electrode active material layer.

[0184]

[0185] Using an ion milling system (JEOL, IB-19530CCP), each anode manufactured at 6 kV for 2 hours was cross-sectioned, and then analyzed by scanning electron microscopy (SEM) (FEI, Quanta 250 FEG). In the case of secondary particles, SEM images containing one to several secondary particles were obtained, and in the case of single particles, SEM images containing one to several thousand single particles were obtained. The SEM images were analyzed by electron backscatter diffraction (EBSD) (EDAX, Velocity Super). The analysis conditions were an acceleration voltage of 20 kV, a spot size of 5, a working distance of 16 mm, and the specimen was maintained at 70° to the detector.

[0186] Afterwards, from the data obtained from electron backscatter diffraction (EBSD) analysis (EBSD analysis image), in the case of secondary particles, the particle diameter of the secondary particle cross-section is the average particle diameter (D 50 ) was cropped into an image containing only one secondary particle, which is similar to the level of a single particle, and an image containing from one to several thousand single particles was cropped (image cropping) into an image containing only one to several thousand single particles in the case of a single particle. For reference, when cropping the image, in each of Examples 1 to 4 and Comparative Example 1, the image sizes were 5 µm x 5 µm (Example 1), 300 µm x 50 µm (Example 2), 12 µm x 12 µm (Example 3), 40 µm x 35 µm (Example 4), and 5 µm x 4 µm (Comparative Example 1).

[0187] From the cropped EBSD analysis image, a Kernel Average Misorientation Map (KAM Map) was obtained through the NPAR and Clean-up (Pseudo-symmetry) processes (a process that reduces the probability of misinterpretation due to the OIM software not properly processing results from low-quality Kikuchi patterns during analysis) processes (using the OIM Analysis program of EDAX), which are processes to offset noise without disturbing the fine grain structure information. The KAM Map was obtained from the 1st to 4th neighboring pixels of the kernel pixel, and the misorientation value between the kernel pixel and the nth neighboring pixels was calculated. Figures 1 to 5 are KAM Maps of the positive electrode active materials of Example 1 (Figure 1), Example 2 (Figure 2), Example 3 (Figure 3), Example 4 (Figure 4), and Comparative Example 1 (Figure 5), respectively. The average KAM values ​​([sum of KAM values ​​of all pixels] / [total number of pixels]) obtained from the Kernel Average Misorientation Map (KAM Map) obtained from electron backscatter diffraction (EBSD) analysis are shown in Table 1 below.

[0188] Meanwhile, the image sizes and resolutions of the KAM Maps of FIGS. 1 to 5 are as follows. The KAM Map images of FIGS. 1 to 5 are images with a total of 100,000 to 400,000 image pixels.

[0189] - Figure 1: Image size = 5㎛×5㎛, resolution = 500×500

[0190] - Figure 2: Image size = 300㎛×50㎛, resolution = 1500×250

[0191] - Figure 3: Image size = 12㎛×12㎛, resolution = 480×480

[0192] - Figure 4: Image size = 40㎛×35㎛, resolution = 571×500

[0193] - Figure 5: Image size = 5㎛×4㎛, resolution = 500×400

[0194]

[0195] Average KAM value (°) Example 10.37 Example 20.45 Example 30.51 Example 40.36 Comparative example 11.07

[0196] Experimental Example 2

[0197] (Half-cell manufacturing)

[0198] Each of the positive electrode active materials manufactured in Examples 1 to 4 and Comparative Example 1, carbon black (Denka, DenkaBlack) as a conductive material, and PVdF (Kureha, KF1300) as a binder were added to a solvent, N-methylpyrrolidone (NMP) (Daejung Chemicals & Metals Co., Ltd.), at a weight ratio of 95:3:2 to manufacture a composition for forming a positive electrode active material layer.

[0199] The composition for forming the positive electrode active material layer was applied to one surface of an aluminum foil current collector having a thickness of 20 μm, and dried at 135°C for 3 hours to form a positive electrode active material layer. Subsequently, the positive electrode was manufactured by rolling using a roll pressing method so that the porosity of the positive electrode active material layer became 20% by volume after rolling.

[0200] An electrode assembly was manufactured using lithium metal as an anode together with the above-mentioned anode, a porous polyethylene separator was interposed between the anode and the cathode, and the electrode assembly was placed inside a case, and an electrolyte was injected into the case to manufacture a coin half-cell. At this time, the electrolyte was manufactured by dissolving 1.0 M lithium hexafluorophosphate (LiPF6) in an organic solvent composed of ethylene carbonate / ethyl methyl carbonate / diethyl carbonate (EC:DMC:EMC mixed volume ratio = 3:4:3).

[0201] (Evaluation of electrochemical properties)

[0202] (1) Initial charge / discharge capacity evaluation

[0203] The half-cells manufactured above were each charged at 25°C with a constant current (CC) of 0.1C until the voltage reached 4.25V, and then charged at a constant voltage (CV) of 4.25V until the charge current reached 0.05C (cut-off current) to measure the charge capacity of the first cycle. After leaving the cells for 20 minutes, they were discharged at a constant current of 0.1C until the voltage reached 3.0V to measure the discharge capacity of the first cycle. The results are shown in Table 2 below. In addition, the percentage of the discharge capacity to the charge capacity was defined as the initial efficiency (%) and is shown in Table 2 below.

[0204] (2) Capacity maintenance rate evaluation

[0205] The half-cells manufactured above were each charged to 4.25 V in CC (0.2 C)-CV (Cut-off current: 0.05 C) mode at 25°C, and then discharged to 2.5 V at 0.2 C to perform an activation process (formation). Subsequently, they were charged to 4.25 V in CC (0.5 C)-CV (Cut-off current: 0.05 C) mode at 45°C, and then discharged to 3.0 V at 1.0 C, which constitutes one cycle, for 30 cycles, and the discharge capacity at each cycle was measured.

[0206] And, the percentage of the discharge capacity of the 30th cycle to the discharge capacity of the first cycle is referred to as the capacity retention rate (%) and is shown in Table 2 below.

[0207]

[0208] Charge capacity (mAh)Discharge capacity (mAh)Initial efficiency (%)Capacity retention rate (%)Example 1230.5208.590.593.4Example 2231.0206.289.396.5Example 3216.5185.085.597.1Example 4230.8208.490.393.6Comparative example 1227.4202.989.292.8

[0209] Referring to Table 2 above, it can be confirmed that the batteries including the positive electrode active materials of Examples 1, 2, and 4 not only have higher initial efficiencies but also have excellent capacity retention compared to the battery including the positive electrode active material of Comparative Example 1. In addition, it can be confirmed that the battery including the positive electrode active material of Example 3 has significantly better capacity retention compared to the battery including the positive electrode active material of Comparative Example 1.

[0210] This is because when the average KAM value ([sum of KAM values ​​of all pixels] / [total number of pixels]) obtained from the Kernel Average Misorientation Map (KAM Map) obtained from electron backscatter diffraction (EBSD) analysis satisfies a range of greater than 0° and less than or equal to 1.0°, the stress and strain within the particle are small.

Claims

1. A cathode active material comprising lithium nickel oxide, A cathode active material having an average KAM value ([sum of KAM values ​​of all pixels] / [total number of pixels]) obtained from a Kernel Average Misorientation Map (KAM Map) obtained from electron backscatter diffraction (EBSD) analysis of greater than 0° and less than or equal to 1.0°.

2. In claim 1, The above lithium nickel-based oxide is a positive electrode active material having a nickel content of 60 mol% or more among all metals excluding lithium.

3. In claim 1, The above lithium nickel-based oxide is a positive electrode active material having a composition represented by the following chemical formula 1: [Chemical Formula 1] Li x Ni a Co b M 1 c M 2 d O2 In the above chemical formula 1, M 1 is Mn, Al or a combination thereof, M 2 is at least one selected from the group consisting of Zr, Y, Mo, B, W, Ti, V, Ce, Hf, La, Ba, F, P, S, Nb, Ta, Sc and Cr, 0.9≤x≤1.1, 0.6≤a<1, 0 <b<0.4, 0<c<0.4, 0≤d≤0.2이다.

4. In claim 1, A positive electrode active material having a KAM value of 0° or more and 5° or less.

5. In claim 1, The above lithium nickel-based oxide is a cathode active material in the form of single particles or secondary particles.

6. In claim 1, Average particle diameter (D 50 ) is a positive electrode active material having a particle size of 1㎛ or more and 30㎛ or less.

7. In claim 1, The above positive electrode active material further includes a coating layer formed on the lithium nickel-based oxide, A cathode active material, wherein the coating layer comprises at least one selected from the group consisting of Zr, Y, Mo, B, W, Ti, V, Ce, Hf, La, Ba, F, P, S, Nb, Ta, Sc and Cr.

8. A positive electrode comprising a positive electrode active material according to any one of claims 1 to 7.

9. A lithium secondary battery comprising a positive electrode according to claim 8.

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