Cathode active material, and cathode and lithium secondary battery comprising same

Abstract

The present invention relates to a cathode active material in a single particle form, the cathode active material comprising: a lithium composite transition metal oxide in a single particle form that has a layered structure; and a coating part containing cobalt formed on the lithium composite transition metal oxide in a single particle form, wherein the cathode active material satisfies expression 1 or expression 2 described in the present specification. Furthermore, the present invention relates to a cathode and a lithium secondary battery comprising the cathode active material.

Description

Cathode active material, and cathode and lithium secondary battery containing the same

[0001] Cross-citation with related applications

[0002] This application claims the benefit of priority from Korean Patent Application No. 10-2023-0172675, filed December 1, 2023, the entire contents of which are incorporated herein by reference.

[0003] Technology field

[0004] The present invention relates to a cathode active material comprising a lithium composite transition metal oxide in the form of a single particle, and a cathode and a lithium secondary battery comprising the same.

[0005]

[0006] With the recent technological development and increasing demand for mobile devices and electric vehicles, the demand for secondary batteries as an energy source is rapidly increasing. Among these secondary batteries, lithium secondary batteries, which boast high energy density and voltage, long cycle life, and low self-discharge rates, are commercialized and widely used.

[0007] Lithium transition metal oxides such as lithium cobalt oxide such as LiCoO2, lithium nickel oxide such as LiNiO2, lithium manganese oxide such as LiMnO2 or LiMn2O4, and lithium iron phosphate oxide such as LiFePO4 have been developed as positive electrode 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.

[0008] Lithium composite transition metal oxides containing two or more transition metals developed to date are usually manufactured in the form of spherical secondary particles in which tens to hundreds of primary particles are aggregated. Recently, in order to solve the structural and thermal stability problems of the secondary particle-type positive electrode active material itself, the development of single-particle positive electrode active materials is accelerating. Specifically, when secondary particle-type positive electrode active materials are applied to lithium secondary batteries, there is a problem that a large amount of gas is generated, causing the volume of the battery to expand. In addition, when the nickel content in the positive electrode active material is increased for high capacity, the risk of fire also increases. Accordingly, the demand for the development of single-particle positive electrode active materials with excellent stability is increasing. However, single-particle positive electrode materials have the problem of poor resistance characteristics due to their low specific surface area.

[0009] Therefore, there is a need to develop a single-particle type cathode material that has excellent stability and can improve the initial efficiency and resistance characteristics of the battery when applied to the battery.

[0010]

[0011] The present invention is an invention for solving the above problems, and aims to provide a cathode active material that has excellent structural stability and can improve the initial efficiency and resistance characteristics of a battery when applied to a battery.

[0012] In addition, the present invention aims to provide a lithium secondary battery having improved initial efficiency, resistance characteristics, etc., including the positive electrode active material.

[0013]

[0014] To solve the above problem, the present invention provides a positive electrode active material, a positive electrode, and a lithium secondary battery.

[0015]

[0016] (1) The present invention provides a positive electrode active material comprising a lithium composite transition metal oxide in the form of a single particle having a layered structure; and a coating portion including cobalt formed on the lithium composite transition metal oxide; and satisfying the following formula 1 or formula 2.

[0017] [Formula 1]

[0018]

[0019] [Formula 2]

[0020]

[0021] In the above equations 1 and 2, is the ratio of the peak intensity corresponding to the LiCoO2Cu Kα1 diffraction peak position at 37° to 38° to the peak intensity of the (003) plane in the XRD spectrum of the positive electrode active material. is the ratio of the peak intensity corresponding to the LiCoO2Cu Kα1 diffraction peak position at 45° to 45.5° to the peak intensity of the (003) plane in the XRD spectrum of the positive electrode active material.

[0022] (2) In the present invention, in the above (1), the lithium composite transition metal oxide has an average particle diameter (D 50 ) provides a positive electrode active material having a diameter of 1.0㎛ to 5.0㎛.

[0023] (3) The present invention provides a positive electrode active material in (1) or (2), wherein the lithium composite transition metal oxide includes nickel (Ni), cobalt (Co), and manganese (Mn).

[0024] (4) The present invention provides a positive electrode active material in any one of the above (1) to (3), wherein the lithium composite transition metal oxide has a composition represented by the following chemical formula 1.

[0025] [Chemical Formula 1]

[0026] Li a Ni b Co c Mnd M 1 e O2

[0027] In the above chemical formula 1,

[0028] M 1 is at least one selected from Al, Zr, B, W, Mo, Cr, Nb, Mg, Hf, Ta, La, Ti, Sr, Ba, Ce, Sn, Y, Zn, F, P and S,

[0029] 0.9≤a≤1.1, 0.8≤b<1.0, 0 <c<0.2, 0<d<0.2, 0≤e≤0.1, b+c+d+e=1이다.

[0030] (5) The present invention provides a positive electrode active material in any one of the above (1) to (4), wherein the coating portion includes a thin film shape, a discontinuously formed island shape, or a combination thereof.

[0031] (6) The present invention provides a positive electrode active material in the form of a single particle in a region of 5 nm to 100 nm in the center direction from the surface of the positive electrode active material in any one of (1) to (5) above.

[0032] (7) The present invention provides a positive electrode comprising a positive electrode active material according to any one of (1) to (6).

[0033] (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.

[0034]

[0035] The cathode active material of the present invention comprises a lithium composite transition metal oxide in the form of a single particle; and a coating portion including cobalt formed on the lithium composite transition metal oxide in the form of a single particle; and satisfies Equation 1 or Equation 2 described herein, thereby improving the initial efficiency, resistance characteristics, capacity characteristics, life characteristics, etc. of a lithium secondary battery.

[0036]

[0037] Figure 1 is an XRD spectrum of the positive electrode active materials of Examples 1 to 3 and Comparative Examples 1 and 2.

[0038] Figure 2 is an SEM image of a sintered product of a manufacturing example.

[0039] Figure 3 is an SEM image of the positive electrode active material of Example 1.

[0040] Figure 4 is an SEM image of the positive electrode active material of Example 2.

[0041] Figure 5 is an SEM image of the positive electrode active material of Example 3.

[0042] Figure 6 is an SEM image of the positive electrode active material of Comparative Example 1.

[0043] Figure 7 is an SEM image of the positive electrode active material of Comparative Example 3.

[0044] Figure 8 is an SEM image of the positive electrode active material of Comparative Example 4.

[0045] Figure 9 is HAADF-STEM (High Angle Annular Dark Field - Scanning Transmission Electron Microscopy) element mapping data of a cross-sectional sample of a positive electrode active material of Example 2.

[0046]

[0047] Hereinafter, the present invention will be described in more detail to help understand the present invention.

[0048] 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.

[0049]

[0050] It should be understood that the terms “include,” “have,” or “have” 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.

[0051] In this specification, the term 'on' means not only when a configuration is formed directly on the top surface of another configuration, but also when a third configuration is interposed between these configurations.

[0052] In this specification, the term "single-particle positive electrode active material" refers to a positive electrode active material composed of 10 or fewer primary particles, in contrast to a spherical secondary particle positive electrode active material formed by agglomeration of tens to 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 particle composed of one primary particle, or may be a secondary particle in which several primary particles are agglomerated.

[0053] 'Primary particle' refers to the smallest particle unit recognized when observing a positive electrode active material through a scanning electron microscope, and 'secondary particle' refers to a secondary structure formed by the aggregation of multiple primary particles.

[0054] In this specification, the term 'average particle diameter (D 50 )' means the particle size at the 50% point of the volume cumulative distribution according to particle size. The above average particle size is calculated 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., S3500 from Microtrac), and measuring the difference in diffraction pattern according to particle size when the particles pass through the laser beam to calculate the particle size distribution, and calculating the particle diameter at the point where it becomes 50% of the volume cumulative distribution according to particle size in the measuring device, thereby obtaining D 50can be measured. Specifically, in this specification, D 50 The particle characteristics parameters of Microtrac's S3500 were set to Refractive index: 1.55, Transparency: Transparent, and Shape: Irregular. Then, the powder to be measured and 500 uL of a 10 wt% sodium hexa-metaphosphate aqueous solution were added to 25 ml of distilled water at 20% flow, and sonication was performed for 1 minute. This is the measured value.

[0055] In this specification, When the XRD spectrum of the positive electrode active material is normalized by setting the peak intensity of the (003) plane to 1, it means the peak intensity at a specific 2θ. That is, It means the ratio of the peak intensity at a specific 2θ to the peak intensity of the (003) plane in the XRD spectrum of the positive electrode active material.

[0056]

[0057] positive electrode active material

[0058] The present invention provides a cathode active material comprising a lithium composite transition metal oxide in the form of a single particle having a layered structure; and a coating portion including cobalt formed on the lithium composite transition metal oxide, and satisfying the following formula 1 or formula 2.

[0059] [Formula 1]

[0060]

[0061] [Formula 2]

[0062]

[0063] In the above equations 1 and 2,

[0064] is the ratio of the peak intensity corresponding to the LiCoO2Cu Kα1 diffraction peak position at 37° to 38° to the peak intensity of the (003) plane in the XRD spectrum of the positive electrode active material.

[0065] is the ratio of the peak intensity corresponding to the LiCoO2Cu Kα1 diffraction peak position at 45° to 45.5° to the peak intensity of the (003) plane in the XRD spectrum of the positive electrode active material.

[0066] At this time, the peak intensity corresponding to the LiCoO2Cu Kα1 diffraction peak position in the XRD spectrum of a specific positive electrode active material is the XRD peak intensity corresponding to the 2θ value corresponding to the position of the Cu Kα1 diffraction peak appearing in the XRD spectrum graph of LiCoO2.

[0067]

[0068] The present inventors have found that when a cathode active material comprises a lithium composite transition metal oxide in the form of a single particle; and a coating portion including cobalt formed on the lithium composite transition metal oxide in the form of a single particle; and satisfies Equation 1 or Equation 2, surface deterioration that may occur due to a high sintering temperature during the production of the cathode active material in the form of a single particle is reduced, and the residual lithium content is low, thereby improving the initial efficiency, resistance characteristics, capacity characteristics, life characteristics, etc. of a lithium secondary battery, and have completed the present invention.

[0069] When the positive electrode active material includes the coating portion, the amount of residual lithium byproducts can be reduced, structural stability can be increased, and thus the lifespan and resistance characteristics of the battery can be improved, and the amount of gas generated can also be reduced. At this time, the coating portion can have a thin film shape or a discontinuously formed island shape, and can be formed over the entire surface of the lithium composite transition metal oxide or can be formed locally.

[0070] Meanwhile, if the positive electrode active material according to the present invention does not satisfy the above formula 1 or formula 2, there is a problem in that the problem of the degenerated layer and residual lithium existing on the surface of the positive electrode active material in the form of a single particle cannot be improved.

[0071] Specifically, Equation 1( ) is less than 0 and Equation 2( ) is 1 or less, there is a problem that a deteriorated portion of the surface of the positive electrode active material in the form of a single particle still exists because the cobalt coating layer does not exist. In addition, when the value according to Equation 1 exceeds 15 and when the value according to Equation 2 exceeds 10, cobalt is diffused and exists inside the positive electrode active material in the form of a single particle, so in this case too, there is almost no cobalt coating layer on the surface of the positive electrode active material, so there is a problem that a deteriorated portion of the surface of the positive electrode active material still exists.

[0072] The values ​​according to the above formulas 1 and 2 are determined by a complex interaction of factors such as the presence or absence of a coating portion containing cobalt, the manufacturing method of the positive electrode active material, for example, the amount of cobalt-containing coating material added during the manufacturing of the positive electrode active material, and the heat treatment temperature, and are not determined by any one factor alone.

[0073]

[0074] According to the present invention, the lithium composite transition metal oxide has an average particle diameter (D 50 ) may be 1.0 ㎛ to 5.0 ㎛, specifically 1.0 ㎛ or more, 1.5 ㎛ or more, 2.0 ㎛ or more, 2.5 ㎛ or more, or 3.0 ㎛ or more, and 4.5 ㎛ or less, or 5.0 ㎛ or less. The average particle diameter (D of the lithium composite transition metal oxide 50 ) is within the above range, the amount of gas generated during charge / discharge behavior can be minimized and high capacity can be achieved.

[0075]

[0076] According to the present invention, the lithium composite transition metal oxide may include nickel (Ni), cobalt (Co), and manganese (Mn).

[0077] The above lithium composite transition metal oxide may contain nickel in an amount of 60 mol% or more, specifically, 80 mol% or more, and more specifically, 85 mol% or more, based on the total moles of metals excluding lithium. That is, the lithium composite transition metal oxide may be a high-nickel (High Ni) lithium composite transition metal oxide. In this case, the energy density of a lithium secondary battery can be improved.

[0078] According to the present invention, the lithium composite transition metal oxide may have a composition represented by the following chemical formula 1. In this case, the lithium composite transition metal oxide has a layered structure.

[0079] [Chemical Formula 1]

[0080] Li a Ni b Co c Mn d M 1 e O2

[0081] In the above chemical formula 1,

[0082] M 1 is at least one selected from Al, Zr, B, W, Mo, Cr, Nb, Mg, Hf, Ta, La, Ti, Sr, Ba, Ce, Sn, Y, Zn, F, P and S,

[0083] 0.9≤a≤1.1, 0.8≤b<1.0, 0 <c<0.2, 0<d<0.2, 0≤e≤0.1, b+c+d+e=1이다.

[0084] The above b refers to the atomic fraction of nickel among the metal elements in the lithium composite transition metal oxide, and may be 0.80 or more, 0.81 or more, 0.82 or more, 0.83 or more, 0.84 or more, 0.85 or more, 0.86 or more, 0.87 or more, 0.88 or more, 0.89 or more, or 0.90 or more, and may be 0.95 or less, 0.96 or less, 0.97 or less, 0.98 or less, 0.99 or less, or less than 1.0.

[0085] The above c refers to the atomic fraction of cobalt among the metal elements in the lithium composite transition metal oxide, and may be greater than 0, 0.001 or more, 0.002 or more, 0.003 or more, 0.004 or more, 0.005 or more, 0.006 or more, 0.007 or more, 0.008 or more, 0.009 or more, or 0.01 or more, and may be 0.05 or less, 0.06 or less, 0.07 or less, 0.08 or less, 0.09 or less, 0.10 or less, 0.11 or less, 0.12 or less, 0.13 or less, 0.14 or less, 0.15 or less, 0.16 or less, 0.17 or less, 0.18 or less, 0.19 or less, or less than 0.20.

[0086] The above d refers to the atomic fraction of manganese among the metal elements in the lithium composite transition metal oxide, and may be greater than 0, 0.005 or more, 0.01 or more, 0.015 or more, or 0.02 or more, and may be 0.04 or less, 0.05 or less, 0.06 or less, 0.07 or less, 0.08 or less, 0.09 or less, 0.10 or less, 0.11 or less, 0.12 or less, 0.13 or less, 0.14 or less, 0.15 or less, 0.16 or less, 0.17 or less, 0.18 or less, 0.19 or less, or less than 0.20.

[0087] The above e is M among the metal elements in the lithium composite transition metal oxide. 1It refers to the atomic fraction of an element, which can be 0 or greater, 0.007 or less, 0.008 or less, 0.009 or less, 0.01 or less, 0.05 or less, or 0.1 or less.

[0088] According to the present invention, the lithium composite transition metal oxide may be doped with zirconium and yttrium. In this case, the particle shape is improved and the structure is stabilized, thereby increasing the capacity and energy density of the battery.

[0089]

[0090] According to the present invention, the coating part may include a lithium cobalt-based oxide having a composition with a higher cobalt content than the lithium composite transition metal oxide. That is, the coating part has the same layered structure as the lithium composite transition metal oxide, but is composed of LiCo 1-x M x It may include a lithium cobalt-based oxide having a composition represented by O2 (wherein M is Ni, Co, Mn, Al or a combination thereof, and x is 0 or more and less than 1.0).

[0091]

[0092] According to the present invention, the coating portion may be in the form of a thin film, a discontinuously formed island, or a combination thereof. Alternatively, if the coating portion is a thin film, the film may have a wrinkled shape. In this case, a coating portion containing an appropriate amount of cobalt is formed on the surface of the positive electrode active material, thereby improving the surface degradation layer, thereby further improving the battery's capacity, initial efficiency, and resistance.

[0093]

[0094] According to the present invention, the coating portion may be a region extending from 5 nm to 100 nm from the surface of the positive electrode active material toward the center. That is, the coating portion may be a region extending from the surface to a specific point within a region extending from 5 nm to 100 nm toward the center of the positive electrode active material. In this case, a coating portion including an appropriate amount of cobalt is formed on the surface of the positive electrode active material, thereby improving the surface deterioration layer, thereby further improving the capacity, initial efficiency, and resistance of the battery.

[0095]

[0096] Meanwhile, the cobalt present in the coating portion may be included in an amount of 0.5 mol% to 3 mol% based on the total moles of metals excluding lithium included in the lithium composite transition metal oxide. In this case, residual lithium byproducts can be further reduced, and lifespan and resistance characteristics can be further improved.

[0097]

[0098] The cathode active material according to the present invention can be manufactured by a method for manufacturing a cathode active material, comprising: (A) mixing a cathode active material precursor, which is a composite transition metal hydroxide, a composite transition metal oxyhydroxide, or a combination thereof, and a lithium-containing raw material to manufacture a mixture; (B) firing the mixture to manufacture a sintered product; and (C) mixing the sintered product and a cobalt-containing coating material, and then performing a heat treatment.

[0099]

[0100] The lithium-containing raw material may be lithium-containing sulfate, nitrate, acetate, carbonate, oxalate, citrate, halide, hydroxide or oxyhydroxide, and is not particularly limited as long as it can be dissolved in water. Specifically, the lithium-containing raw material may be Li2CO3, LiNO3, LiNO2, LiOH, LiOHㆍH2O, LiH, LiF, LiCl, LiBr, LiI, CH3COOLi, Li2O, Li2SO4, CH3COOLi, or Li3C6H5O7, and any one of these or a mixture of two or more thereof may be used.

[0101] The above complex transition metal hydroxide, complex transition metal oxyhydroxide or combination thereof and the lithium-containing raw material may be mixed so that the ratio (Li / M) of the number of moles of lithium (Li) included in the lithium-containing raw material to the total number of moles (M) of transition metals included in the complex transition metal hydroxide, complex transition metal oxyhydroxide or combination thereof is 1.0 or more, 1.01 or more, or 1.02 or more, and 1.05 or less, 1.06 or less, 1.07 or less, 1.08 or less, 1.09 or less, or 1.10 or less.

[0102] When preparing the mixture in step (A) above, a raw material containing a doping element, for example, a raw material containing zirconium, a raw material containing yttrium, etc., may be further mixed.

[0103]

[0104] The above step (B) may be a step of manufacturing a sintered product by successively firing the mixture for the first time at 800°C to 900°C and for the second time at 700°C to 800°C under an air atmosphere. In this case, the second firing may be performed at a lower temperature than the first firing.

[0105]

[0106] The cobalt-containing coating material may be Co(OH)2, and the cobalt-containing coating material may be mixed in an appropriate amount capable of reacting with residual lithium present in the sintered product, for example, an amount corresponding to 2 mol% to 5 mol%, specifically 2 mol% to 3 mol%, based on the total moles of the sintered product.

[0107] The above heat treatment may be performed at 650°C to 800°C, specifically at 670°C to 770°C, to allow cobalt to sufficiently react only on the surface. Meanwhile, the heat treatment may include a first heat treatment at 650°C to 800°C, specifically at 670°C to 770°C, followed by a second heat treatment (similar to an annealing process) at 450°C to 550°C to remove defects on the surface of the positive electrode active material.

[0108]

[0109] anode

[0110] The present invention provides a positive electrode comprising the positive electrode active material.

[0111] 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.

[0112] 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 adhesion 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.

[0113] The above-mentioned 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.

[0114] The conductive material is used to provide conductivity to the electrode, and in the battery to be formed, as long as it does not cause a chemical change and has electronic conductivity, it can be used without any special restrictions. Specific examples include graphite such as natural graphite or artificial graphite; carbon-based materials such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, 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.

[0115] The above binder serves to improve the adhesion between positive electrode active material particles and the 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.

[0116] 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 agent, 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, peeling the film from the support, and laminating the resulting film onto a positive electrode current collector.

[0117] The solvent may be a solvent generally used in the relevant technical field, such as dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), dimethylformamide (DMF), acetone, or water. One of these may be used alone or a mixture of two or more thereof may be used. The amount of the solvent used is sufficient to dissolve or disperse the positive electrode active material, conductive material, 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.

[0118]

[0119] lithium secondary battery

[0120] The present invention provides a lithium secondary battery comprising: the positive electrode; the negative electrode; a separator interposed between the positive electrode and the negative electrode; and an electrolyte.

[0121]

[0122] The above lithium secondary battery may optionally further include a battery container that houses the electrode assembly of the positive electrode, negative electrode, and separator, and a sealing member that seals the battery container.

[0123]

[0124] The above negative electrode may include a negative electrode current collector and a negative electrode active material layer positioned on the negative electrode current collector.

[0125] The negative electrode current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery. 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.

[0126] The above negative electrode active material layer may optionally include a binder and a conductive material together with the negative electrode active material.

[0127] As the 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 alloy, Sn alloy, or Al alloy; SiO β(0<β<2), SnO2, vanadium oxide, lithium vanadium oxide, and other metal oxides capable of doping and dedoping lithium; or composites containing the above metallic compounds and carbonaceous materials, such as Si-C composites or Sn-C composites, and any one or a mixture of two or more of these may be used. In addition, a metallic lithium thin film may be used as the negative electrode active material. In addition, both low-crystalline carbon and high-crystalline carbon may be used as the carbonaceous material. Representative examples of low-crystalline carbon include soft carbon and hard carbon, and representative examples of high-crystalline carbon include natural graphite or artificial graphite in the form of amorphous, plate-like, flaky, spherical or fibrous shapes, 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 negative electrode active material may be included in an amount of 80 wt% to 99 wt% based on the total weight of the negative electrode active material layer.

[0128] The binder of the above-described 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.

[0129] The conductive material of the above-described 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.

[0130] The above negative electrode can be manufactured by applying and drying a composition for forming a negative electrode active material layer 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.

[0131] The above 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 any particular restrictions, 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.

[0132] Examples of the electrolyte include, but are not limited to, organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel-type polymer electrolytes, solid inorganic electrolytes, and molten inorganic electrolytes that can be used in the manufacture of lithium secondary batteries. As a specific example, the electrolyte may include an organic solvent and a lithium salt.

[0133] As the organic solvent, any solvent that can serve as a medium through which ions involved in the electrochemical reaction of the battery can move may be used without particular limitation. Specifically, the organic solvent includes 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, isopropyl alcohol, etc.; nitriles such as R-CN (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, etc. can be used. Among these, carbonate solvents are preferable, and a mixture of a cyclic carbonate (e.g., ethylene carbonate or propylene carbonate) having high ionic conductivity and high dielectric constant that can improve the charge / discharge performance of a battery and a low-viscosity linear carbonate compound (e.g., ethyl methyl carbonate, dimethyl carbonate, or diethyl carbonate) is more preferable.

[0134] The above lithium salt can be used without any special limitation as long as it is a compound that can provide lithium ions used in a lithium secondary battery. Specifically, the anion of the above 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.

[0135] In addition to the electrolyte components, the electrolyte may further include one or more additives, such as haloalkylene carbonate compounds such as difluoroethylene carbonate, pyridine, triethylphosphite, triethanolamine, cyclic ethers, 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.

[0136]

[0137] A lithium secondary battery including a cathode active material according to the present invention has excellent initial efficiency, resistance characteristics, 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).

[0138] 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.

[0139] 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.

[0140] Accordingly, a battery module including the lithium secondary battery as a unit cell and a battery pack including the same are provided.

[0141] The above 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.

[0142]

[0143] 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.

[0144]

[0145] Manufacturing example

[0146] A composite transition metal hydroxide in the form of secondary particles formed by the agglomeration of tens to hundreds of primary particles (composition: Ni) 0.96 Co 0.01 Mn 0.03 (OH)2, average particle size (D) 50): 4㎛) and Al(OH)3 were mixed in a molar ratio of 1:0.003, and LiOH·H2O was mixed so that the ratio of the total mole number of transition metals included in the composite transition metal hydroxide (Ni+Co+Mn) to the mole number of lithium included in LiOH (Li) ((Ni+Co+Mn):Li) was 1:1.025. Then, ZrO2 was additionally mixed in an amount such that Zr was 1500 ppm based on the total weight of the composite transition metal hydroxide, and Y2O3 was additionally mixed in an amount such that Y was 300 ppm based on the total weight of the composite transition metal hydroxide, thereby preparing a mixture. The above mixture was heated from room temperature to 835°C at a rate of 5°C / min, and then fired for the first time for 6 hours while maintaining the temperature at 835°C, then cooled to 770°C, and then fired for the second time while maintaining the temperature at 770°C for 12.5 hours to manufacture a fired product. The fired product had an average particle diameter (D 50 ) is 3.6㎛, and non-thermal grinding is performed using an air jet mill to produce a lithium composite transition metal oxide (composition: Li) having a layered structure and a single particle form. 1.025 Ni 0.9550 Co 0.0099 Mn 0.0298 Al 0.0034 Zr 0.0015 Y 0.0003 O2) was obtained.

[0147]

[0148] Examples and Comparative Examples

[0149] Example 1

[0150] The lithium composite transition metal oxide and Co(OH)2 manufactured in the manufacturing example were mixed in a molar ratio of 1:0.03, and Al(OH)3 was mixed so that Al was 500 ppm based on the total weight of the lithium composite transition metal oxide to manufacture a mixture. Under an oxygen atmosphere, the mixture was heated from room temperature to 675°C at a rate of 5°C / min, and then the temperature was maintained at 675°C for 5 hours while performing a first heat treatment, then the temperature was lowered to 500°C, and the temperature was maintained at 500°C for 3 hours while performing a second heat treatment, so that a coating portion including cobalt and aluminum was formed on the lithium composite transition metal oxide, and a positive electrode active material (composition: Li 1.0004 Ni 0.9341 Co 0.0298 Mn 0.0292 Al 0.0051 Zr 0.0015 Y 0.0003 O2, average particle size (D 50 ): 3.8㎛) was manufactured.

[0151]

[0152] Example 2

[0153] The lithium composite transition metal oxide and Co(OH)2 manufactured in the manufacturing example were mixed in a molar ratio of 1:0.03, and Al(OH)3 was mixed so that Al was 500 ppm based on the total weight of the lithium composite transition metal oxide to manufacture a mixture. Under an oxygen atmosphere, the mixture was heated from room temperature to 715°C at a rate of 5°C / min, and then the temperature was maintained at 715°C for 5 hours while performing a first heat treatment, then the temperature was lowered to 500°C, and the temperature was maintained at 500°C for 3 hours while performing a second heat treatment, so that a coating portion including cobalt and aluminum was formed on the lithium composite transition metal oxide (composition: Li 1.0004 Ni 0.9341 Co 0.0298 Mn 0.0292 Al 0.0051 Zr 0.0015 Y 0.0003 O2, average particle size (D 50 ): 3.8㎛) was manufactured.

[0154]

[0155] Example 3

[0156] The lithium composite transition metal oxide and Co(OH)2 manufactured in the manufacturing example were mixed in a molar ratio of 1:0.03, and Al(OH)3 was mixed so that Al was 500 ppm based on the total weight of the lithium composite transition metal oxide to manufacture a mixture. Under an oxygen atmosphere, the mixture was heated from room temperature to 765°C at a rate of 5°C / min, and then the temperature was maintained at 765°C for 5 hours while performing a first heat treatment, then the temperature was lowered to 500°C, and the temperature was maintained at 500°C for 3 hours while performing a second heat treatment, so that a coating portion including cobalt and aluminum was formed on the lithium composite transition metal oxide, and a positive electrode active material (composition: Li 1.0004 Ni 0.9341 Co 0.0298 Mn 0.0292 Al 0.0051 Zr 0.0015 Y 0.0003 O2, average particle size (D 50 ): 3.8㎛) was manufactured.

[0157]

[0158] Comparative Example 1

[0159] The lithium composite transition metal oxide manufactured in the manufacturing example was heated from room temperature to 715°C at a rate of 5°C / min without a coating raw material, and then subjected to a first heat treatment while maintaining the temperature at 715°C for 5 hours, then cooled to 500°C, and then subjected to a second heat treatment while maintaining the temperature at 500°C for 3 hours, thereby obtaining a positive electrode active material (composition: Li 1.025 Ni 0.9550 Co 0.0099 Mn 0.0298 Al 0.0034 Zr 0.0015 Y 0.0003 O2, average particle size (D 50 ): 3.8㎛) was manufactured.

[0160]

[0161] Comparative Example 2

[0162] A cathode material was manufactured by mixing the lithium composite transition metal oxide manufactured in the manufacturing example and LiCoO2 (aladin, Avention) in a molar ratio of 1:0.03.

[0163]

[0164] Comparative Example 3

[0165] The lithium composite transition metal oxide and Co(OH)2 manufactured in the manufacturing example were mixed in a molar ratio of 1:0.03, and Al(OH)3 was mixed so that Al was 500 ppm based on the total weight of the lithium composite transition metal oxide to manufacture a mixture. Under an oxygen atmosphere, the mixture was heated from room temperature to 615°C at a rate of 5°C / min, and then the temperature was maintained at 615°C for 5 hours while performing a first heat treatment, then the temperature was lowered to 500°C, and the temperature was maintained at 500°C for 3 hours while performing a second heat treatment, so that a coating portion including cobalt and aluminum was formed on the lithium composite transition metal oxide, and a positive electrode active material (composition: Li 1.0004 Ni 0.9341 Co 0.0298 Mn 0.0292 Al 0.0051 Zr 0.0015 Y 0.0003 O2, average particle size (D 50 ): 3.8㎛) was manufactured.

[0166]

[0167] Comparative Example 4

[0168] The lithium composite transition metal oxide and Co(OH)2 manufactured in the manufacturing example were mixed in a molar ratio of 1:0.03, and Al(OH)3 was mixed so that Al was 500 ppm based on the total weight of the lithium composite transition metal oxide to manufacture a mixture. Under an oxygen atmosphere, the mixture was heated from room temperature to 815°C at a rate of 5°C / min, and then the temperature was maintained at 815°C for 5 hours while performing a first heat treatment, then the temperature was lowered to 500°C, and the temperature was maintained at 500°C for 3 hours while performing a second heat treatment, so that a coating portion including cobalt and aluminum was formed on the lithium composite transition metal oxide (composition: Li 1.0004 Ni 0.9341 Co 0.0298 Mn 0.0292 Al 0.0051 Zr 0.0015 Y 0.0003 O2, average particle size (D 50 ): 3.8㎛) was manufactured.

[0169]

[0170]

[0171] Experimental example

[0172] Experimental Example 1: Analysis of positive electrode active material

[0173] - XRD analysis

[0174] Using XRD (Bruker, D8 Endeavor), XRD spectra of each of the positive electrode active materials of Examples 1 to 3 and Comparative Examples 1 to 4 were obtained and analyzed. At this time, the XRD measurement conditions were as follows.

[0175] - Voltage: 40kV

[0176] - Current: 40mA

[0177] - Power: 1600W

[0178] - Element: Cu

[0179] - Angle: 15~50°, Increment: 0.02° (10s per step)

[0180] The XRD spectrum of each positive electrode active material is shown in Fig. 1, and in the XRD spectrum, the peak intensity of the (003) plane, the peak intensity corresponding to the LiCoO2Cu Kα1 diffraction peak position at 37° to 38°, and the peak intensity corresponding to the LiCoO2Cu Kα1 diffraction peak position at 45° to 45.5° were confirmed, and the values ​​according to Equations 1 and 2 were calculated and shown in Table 1 below. At this time, the peak intensity corresponding to the LiCoO2Cu Kα1 diffraction peak position in the XRD spectrum of a specific positive electrode active material is the XRD peak intensity corresponding to the 2θ value corresponding to the position of the Cu Kα1 diffraction peak of LiCoO2 appearing in the XRD spectrum graph of Comparative Example 2, and specifically, it is the XRD peak intensity corresponding to the 2θ value corresponding to the position of the larger peak among the two peaks appearing at 37° to 38° or 45° to 45.5° in the XRD spectrum graph of Comparative Example 2 of Fig. 1.

[0181]

[0182] Classification 1 Example 2 Example 17.26 0.97 Example 211.07 5.50 Example 312.2 18.46 Comparative Example 120.6 218.05 Comparative Example 2-7.77-22.01 Comparative Example 3-0.65-6.22 Comparative Example 416.75 15.24

[0183] Referring to Table 1, it can be confirmed that the positive electrode active materials of Examples 1 to 3 satisfy Equation 1 or Equation 2 of the present invention, while the positive electrode active materials of Comparative Examples 1 to 4 deviate from it.

[0184]

[0185] - Analysis of positive electrode active material morphology and Co element

[0186] Using an electron probe microanalyzer (JEOL, JXA-iHP200F) (acceleration voltage: 15 kV, probe current: 20 mA, dwell time: 20 ms), SEM images of the sintered products of the manufacturing examples, the positive electrode active materials of Examples 1 to 3, and Comparative Examples 1, 3, and 4 were obtained, and these are shown in FIG. 2 (sintered products of the manufacturing examples), FIG. 3 (Example 1), FIG. 4 (Example 2), FIG. 5 (Example 3), FIG. 6 (Comparative Example 1), FIG. 7 (Comparative Example 3), and FIG. 8 (Comparative Example 4), respectively.

[0187] In addition, HAADF-STEM EDS (Energy-dispersive X-ray Spectroscopy) elemental mapping data of the cross-section sample of the positive electrode active material of Example 2 was obtained using a Thermo Fisher Scientific, Titan G2 ChemiSTEM 80-200 equipment, and the data is shown in Fig. 9. Meanwhile, the cross-section sample of the positive electrode active material was prepared by performing Ar ion milling for 2 hours using an argon ion milling system (HITACHI, IM-5000) (acceleration voltage: 6 kV).

[0188]

[0189] Referring to FIGS. 2 to 6, it can be confirmed that the positive electrode active materials of Examples 1 to 3 have a coating portion on the surface, whereas the positive electrode active material of Comparative Example 1 does not have a coating portion on the surface.

[0190] Referring to Fig. 9, it can be seen that Co is coated on the surface in the form of a thin film (in the form of a wrinkled film), and Al is coated in the form of an island. In addition, it can be seen that the coating portion is formed thinly in an area within 100 nm in the center direction from the surface of the positive electrode active material.

[0191]

[0192] Experimental Example 2: Battery Characteristics Evaluation

[0193] (Half-cell manufacturing)

[0194] Each of the positive electrode active materials manufactured in Examples 1 to 3 and Comparative Examples 1 to 4, the carbon black (Denka, DenkaBlack) conductive agent, and the PVdF (Kureha, KF1300) binder were added to an N-methylpyrrolidone (NMP) (Daejung Chemicals & Metals Co., Ltd.) solvent at a weight ratio of 95:3:2 to manufacture a composition for forming a positive electrode active material layer.

[0195] 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 ㎛, and dried at a temperature of 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.

[0196] A half-cell was manufactured using lithium metal as the cathode together with the above-mentioned positive electrode.

[0197] (Evaluation of initial characteristics of the battery)

[0198] The half-cells manufactured above were each charged at 25℃ with a constant current (CC) of 0.2C until 4.25V, then charged at a constant voltage (CV) of 4.25V until the charge current became 0.005mAh (cut-off current), left for 20 minutes, and then discharged at a constant current of 0.2C until 2.5V, and the initial charge capacity and initial discharge capacity were measured, and the direct current internal resistance (DCIR) was calculated, which are shown in Table 2 below. For reference, the DCIR value is a value calculated by dividing the difference between the voltage at 60 seconds and the initial voltage while discharging at a constant current of 0.2C by the applied current.

[0199] (Evaluation of battery cycle characteristics)

[0200] The half-cells manufactured above were each charged at 25°C with a constant current (CC) of 0.2C until the voltage reached 4.25V, and then charged at a constant voltage (CV) of 4.25V until the charge current reached 0.005mAh (cut-off current), left for 20 minutes, and then discharged at a constant current of 0.2C until the voltage reached 2.5V.

[0201] After that, the cell was moved to a chamber at 45℃, charged with a constant current of 0.5C until it reached 4.25V, then charged with a constant voltage (CV) of 4.25V until the charge current became 0.005mAh (cut-off current), and then discharged with a constant current of 1.0C until it reached 2.5V, and 50 cycles of charge and discharge were performed, which constituted one cycle. At this time, the percentage of the discharge capacity of the 50th cycle to the discharge capacity of the first cycle was defined as the capacity retention rate, and is shown in Table 2 below. In addition, the percentage of the DCIR value of the 50th cycle to the DCIR value of the first cycle was defined as the resistance increase rate, and is shown in Table 2 below. For reference, the DCIR value of the nth cycle is calculated by dividing the voltage difference between the fully charged state and 60 seconds after the start of the discharge by the current obtained while discharging to 2.5 V with a constant current of 1.0 C in the nth cycle.

[0202] Charge capacity (mAh / g)Discharge capacity (mAh / g)Initial efficiency (%)DCIR (Ω)Capacity retention rate (%)Resistance increase rate (%)Example 1243.4210.386.421.195.7172.7Example 2242.0212.687.919.996.2157.4Example 3242.0212.187.620.995.6161.7Comparative example 1245.7211.085.934.394.8201.5Comparative example 2240.3206.686.027.494.9196.1Comparative example 3240.6207.686.329.495.0190.3Comparative example 4240.2206.285.824.895.2177.2

[0203] Referring to Table 2, it can be confirmed that the batteries including the positive electrode active materials of Examples 1 to 3 are superior in initial efficiency, resistance characteristics, and life performance compared to the batteries including the positive electrode active materials of Comparative Examples 1 to 4.

[0204]

[0205] As a result, when the positive electrode active material includes a lithium composite transition metal oxide in the form of a single particle; and a coating portion including cobalt formed on the lithium composite transition metal oxide in the form of a single particle; and satisfies Equation 1 or Equation 2 described herein, it can be seen that surface deterioration that may occur due to a high sintering temperature during the production of the positive electrode active material in the form of a single particle is reduced, and the residual lithium content is low, so that the initial efficiency, resistance characteristics, capacity characteristics, life characteristics, etc. of a lithium secondary battery can be improved.

Claims

1. Lithium composite transition metal oxide in the form of a single particle having a layered structure; and A coating portion including cobalt formed on the lithium composite transition metal oxide; A cathode active material satisfying the following equation 1 or equation 2: [Formula 1] [Formula 2] In the above equations 1 and 2, LiCoO exists at 37°~38° for the peak intensity of (003) plane in the XRD spectrum of the cathode active material. 2 is the ratio of peak intensities corresponding to the Cu Kα1 diffraction peak positions, LiCoO exists at 45°~45.5° for the peak intensity of (003) plane in the XRD spectrum of the positive electrode active material. 2 It is the ratio of peak intensities corresponding to the Cu Kα1 diffraction peak positions.

2. In claim 1, The above lithium composite transition metal oxide has an average particle diameter (D 50 ) is a positive electrode active material having a diameter of 1.0㎛ to 5.0㎛.

3. In claim 1, The above lithium composite transition metal oxide is a cathode active material containing nickel (Ni), cobalt (Co) and manganese (Mn).

4. In claim 1, The above lithium composite transition metal oxide is a cathode active material having a composition represented by the following chemical formula 1: [Chemical Formula 1] Li a Ni b Co c Mr d M 1 e O 2 In the above chemical formula 1, M 1 is at least one selected from Al, Zr, B, W, Mo, Cr, Nb, Mg, Hf, Ta, La, Ti, Sr, Ba, Ce, Sn, Y, Zn, F, P and S, 0.9≤a≤1.1, 0.8≤b<1.0, 0 <c<0.2, 0<d<0.2, 0≤e≤0.1, b+c+d+e=1이다.

5. In claim 1, A cathode active material wherein the coating portion comprises a thin film shape, a discontinuously formed island shape, or a combination thereof.

6. In claim 1, The above coating portion is a single particle-shaped cathode active material having a region of 5 nm to 100 nm in the center direction from the surface of the cathode active material.

7. A positive electrode comprising a positive electrode active material according to any one of claims 1 to 6.

8. Anode according to claim 7; cathode; A separator interposed between the positive electrode and the negative electrode; and A lithium secondary battery comprising an electrolyte.

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