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

Abstract

The present invention relates to a cathode active material for a lithium secondary battery, comprising: a lithium metal oxide particle; and zirconium having a concentration gradient increasing from the center portion of the lithium metal oxide particle toward the surface portion thereof, wherein the slope value of the change in zirconium concentration increasing from the center portion of the lithium metal oxide particle toward the surface portion thereof is 0.001-0.2.

Description

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

[0001] The present invention relates to a positive electrode active material for a lithium secondary battery and a lithium secondary battery including the same.

[0002]

[0003] Lithium secondary batteries produce electrical energy through oxidation and reduction reactions when lithium ions are inserted / deintercalated from the positive and negative electrodes, while an organic electrolyte or polymer electrolyte is charged between the positive and negative electrodes, which are made of active materials capable of intercalating and deintercalating lithium ions.

[0004] Lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), lithium manganese oxide (LiMnO2 or LiMn2O4, etc.), and lithium iron phosphate compound (LiFePO4) have been used as cathode active materials for lithium secondary batteries. Among these, lithium cobalt oxide (LiCoO2) is widely used due to its high operating voltage and excellent capacity characteristics, and is applied as a cathode active material for high voltage. However, due to the rising price of cobalt (Co) and unstable supply, it is difficult to use it in large quantities as a power source in fields such as electric vehicles, and the need for the development of a cathode active material that can replace it has arisen.

[0005] Accordingly, a nickel-cobalt-manganese lithium composite transition metal oxide (hereinafter simply referred to as 'NCM-based lithium composite transition metal oxide') was developed in which some of the cobalt (Co) is replaced with nickel (Ni) and manganese (Mn).

[0006] High-nickel NCM cathode materials with a nickel content of 80% or more offer the advantage of high capacity, but suffer from poor stability in cycle-driven environments. To address this, research is being conducted to reduce reactivity with the electrolyte by doping or coating with various elements.

[0007] However, due to chronic problems of these positive electrode active materials, such as structural stability and side reactions with the electrolyte, there are limitations in increasing capacity, and much improvement is still needed.

[0008] Accordingly, there is a need to develop a cathode active material that can implement battery characteristics with excellent capacity and cycle life.

[0009]

[0010] One object of the present invention is to provide a cathode active material including a lithium metal oxide containing a high nickel content having a zirconium concentration gradient that increases from the center of the particle toward the surface, and a lithium secondary battery including the same.

[0011]

[0012] A cathode active material for a lithium secondary battery according to one embodiment of the present invention comprises lithium metal oxide particles; and zirconium having a concentration gradient that increases from the center of the lithium metal oxide particles toward the surface, wherein a gradient value of the concentration change of zirconium that increases from the center of the lithium metal oxide particles toward the surface is 0.001 to 0.2.

[0013] The slope value of the change in the concentration of zirconium increasing from the center toward the surface of the lithium metal oxide particle is 0.005 to 0.1.

[0014] The content of the above zirconium is 0.1 to 0.5 mol% based on the total metal excluding lithium in the above lithium metal oxide.

[0015] The above lithium metal oxide particles are represented by the following chemical formula 1.

[0016] [Chemical Formula 1]

[0017] Li x Ni a Co b Mn c Zr d M e O2

[0018] (Here, 0.80≤x≤1.20, 0.80≤a<1.0, 0≤b≤0.20, 0≤c≤0.20, 0 <d≤0.1, 0≤e≤0.1, a+b+c+d+e=1이고, M은 Al, V, Co, Mg, Ti, Y, Sr, Nb, Ba, Ca B, W, Sc, Si, Fe, Mo, Ce, Hf, Ta 및 La 중 선택되는 1종 이상이다.)

[0019] The crystal grain size of the lithium metal oxide is 90 nm to 135 nm.

[0020] The above lithium metal oxide has a ratio (C / A) of the c-axis length (C) to the a-axis length (A) in the range of 4.9410 to 4.9420.

[0021] The above lithium metal oxide further includes a coating layer containing the element boron (B).

[0022] The above cathode active material has a 30-cycle capacity retention rate of 92% or more measured in a coin half cell at an upper limit voltage of 4.3 V at 45°C.

[0023] The above positive electrode active material has a discharge capacity of 222.0 mAh / g or more.

[0024]

[0025] A cathode active material for a lithium secondary battery according to one embodiment of the present invention can realize excellent battery characteristics, including both discharge capacity and cycle life, of a battery to which the cathode active material is applied.

[0026]

[0027] Figure 1 shows a cross-sectional SEM image of a positive electrode active material manufactured according to an example and a comparative example.

[0028] Figure 2 shows the slope of the change in Zr concentration at each location from the center to the surface of positive electrode active material particles manufactured according to examples and comparative examples.

[0029] The terms first, second, and third, etc., are used to describe, but are not limited to, various parts, components, regions, layers, and / or sections. These terms are used only to distinguish one part, component, region, layer, or section from another part, component, region, layer, or section. Accordingly, a first part, component, region, layer, or section described below may be referred to as a second part, component, region, layer, or section without departing from the scope of the present invention.

[0030] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the present invention. As used herein, the singular forms "singular" and "comprising" include plural forms as well, unless the context clearly dictates otherwise. The word "comprising" as used herein specifies a particular feature, region, integer, step, operation, element, and / or component, but does not exclude the presence or addition of other features, regions, integers, steps, operations, elements, and / or components.

[0031] When a part is referred to as being "on" or "over" another part, it can be directly on or over the other part, or there may be other parts intervening. Conversely, when a part is referred to as being "directly on" another part, there are no other parts intervening.

[0032] Although not defined otherwise, all terms, including technical and scientific terms, used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention pertains. Terms defined in commonly used dictionaries are further interpreted to have meanings consistent with the relevant technical literature and the present disclosure, and are not to be construed as ideal or overly formal unless otherwise defined.

[0033] Also, unless otherwise stated, % means weight%, and 1 ppm is 0.0001 weight%.

[0034] In this specification, the term "combination(s) thereof" described in the expression in the Makushi format means one or more mixtures or combinations selected from the group consisting of the components described in the expression in the Makushi format, and means including any one or more selected from the group consisting of said components.

[0035] 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.

[0036] A method for manufacturing a positive electrode active material for a lithium secondary battery according to one embodiment of the present invention may relate to a positive electrode active material including a layered lithium metal oxide containing nickel.

[0037] The above lithium metal oxide may be a primary particle or a secondary particle formed by agglomeration of a plurality of primary particles.

[0038] In this specification, “secondary particle” means an aggregate, i.e., a secondary structure, in which tens to hundreds of primary particles are aggregated together by physical or chemical bonding between the primary particles without any intentional aggregation or assembly process for the primary particles.

[0039] The above “primary particle” refers to the smallest particle unit that can be distinguished as a single lump when observing the cross-section of the positive electrode active material through a scanning electron microscope (SEM), and may be composed of a single crystal grain or multiple crystal grains.

[0040] Meanwhile, the content of nickel in the lithium metal oxide may be high-nickel containing a high nickel content of 80 mol% or more based on the total molar number of metals excluding lithium.

[0041] However, when the nickel content in lithium metal oxide increases, the initial capacity characteristics are improved, but when charge and discharge are repeated, the highly reactive Ni +4 There is a problem that a large amount of ions are generated, causing structural collapse of the positive electrode active material, which increases the rate of deterioration of the positive electrode active material and reduces the life characteristics.

[0042] Accordingly, the inventors of the present invention have conducted repeated research on a method for manufacturing a positive electrode active material with improved life characteristics, and as a result, have completed the present invention by finding that when the positive electrode active material is doped with Zr and the Zr concentration has a concentration gradient that increases from the center of the positive electrode active material particle toward the surface, the structural stability of the positive electrode active material is effectively improved, and as a result, the high-temperature life characteristics of the battery are improved.

[0043]

[0044] The doping amount of Zr may be in the range of 0.001 mol to 0.007 mol, more specifically, 0.002 mol to 0.005 mol or 0.0035 mol to 0.005 mol, relative to 1 mol of the total of nickel, cobalt, manganese, and doping elements. When the doping amount of Zr satisfies the above range, the high-temperature lifespan and room-temperature lifespan characteristics of the lithium secondary battery can be significantly improved.

[0045] The doping amount of B may be in the range of 0.001 mol to 0.015 mol, more specifically, 0.005 mol to 0.01 mol, relative to 1 mol of the total of nickel, cobalt, manganese, and doping elements. When the doping amount of B satisfies the above range, the crystal grain size is reduced during the firing of the positive electrode active material, so the initial resistance value can be reduced, and the room temperature and high temperature life characteristics and thermal decomposition temperature can be increased.

[0046]

[0047] A cathode active material for a lithium secondary battery according to one embodiment of the present invention includes lithium metal oxide particles including nickel, cobalt, and manganese and zirconium (Zr), wherein the zirconium has a concentration gradient that increases from the center of the lithium metal oxide particles toward the surface.

[0048] In lithium metal oxide, Zr is Zr 4+ Since it exists in a state where Zr ions occupy Li sites, it acts as a kind of pillar and stabilizes the layered structure by alleviating the shrinkage of the lithium ion path during the charge and discharge process. This phenomenon can reduce cation mixing and increase the lithium diffusion coefficient, thereby increasing the cycle life.

[0049] Meanwhile, the Zr has a concentration gradient that increases from the center of the lithium metal oxide particle toward the surface, and the Zr concentration change gradient has a (+) value. Specifically, the Zr concentration change gradient value may be in the range of 0.001 to 0.2. More specifically, it may be 0.005 to 0.1, 0.008 to 0.08. In the present invention, all Zr concentration change gradients measured on two or more radii forming a predetermined angle from the center of the lithium metal oxide particle toward the surface satisfies the above range.

[0050] In the present invention, since the positive electrode active material includes lithium metal oxide particles containing zirconium having a positive gradient of concentration change, excellent performance with structural stability can be achieved despite a high nickel content.

[0051] The above Zr doping amount may be 0.05 to 0.7 mol% based on the total molar number of metals excluding lithium in the lithium metal oxide, and specifically, may be 0.1 to 0.5 mol%. When the Zr doping amount satisfies the above range, the discharge capacity and high-temperature life characteristics of the lithium secondary battery can be significantly improved.

[0052] If the above Zr doping amount is too small, the effect of improving the high-temperature life characteristics due to the improvement in the structural stability of the positive electrode active material may be minimal, and if the above Zr doping amount is too large, the discharge capacity characteristics may deteriorate.

[0053]

[0054] In one embodiment of the present invention, the lithium metal oxide particles may be represented by the following chemical formula 1.

[0055] [Chemical Formula 1]

[0056] Li x Ni a Co b Mn c Zr d M e O2

[0057] In the above chemical formula 1,

[0058] 0.80≤x≤1.20, 0.80≤a<1.0, 0≤b≤0.20, 0≤c≤0.20, 0 <d≤0.1, 0≤e≤0.1, a+b+c+d+e=1이고,

[0059]

[0060] M is at least one selected from Al, V, Co, Mg, Ti, Y, Sr, Nb, Ba, Ca B, W, Sc, Si, Fe, Mo, Ce, Hf, Ta, and La.

[0061] When the nickel content in the lithium metal oxide is 80 mol% or more relative to the total metal content excluding lithium, a cathode active material having high output characteristics can be realized. The cathode active material of the present embodiment having such a composition has a high energy density per volume, and thus has the advantage of improving the capacity of a battery to which it is applied.

[0062] The crystal grain size of the lithium metal oxide particles may be 90 nm to 135 nm, specifically 100 to 120 nm. When the crystal grain size satisfies the above range, the high-temperature life is improved without a decrease in the initial capacity.

[0063] Additionally, the lithium metal oxide may have an a-axis length (lattice parameter) of 2.8740 Å to 2.8755 Å, specifically, 2.8745 Å to 2.8750 Å.

[0064] Additionally, the lithium metal oxide may have a c-axis length (lattice parameter) of 14.2010 Å to 14.2070 Å, specifically, 14.2040 Å to 14.2065 Å.

[0065] Additionally, the ratio (C / A) of the c-axis length (C) to the a-axis length (A) may be in the range of 4.9410 to 4.9420.

[0066] When the a-axis length, c-axis length, and ratio of c-axis length to a-axis length of the lithium metal oxide particles satisfy the above ranges, both the discharge capacity and high-temperature life characteristics of the lithium secondary battery can be significantly improved.

[0067] The lithium metal oxide particles may be in the form of secondary particles including a plurality of primary particles, and the average particle diameter (D50) may be in the range of 10 to 15 μm.

[0068] Meanwhile, the lithium metal oxide may further include a coating layer containing a boron (B) element.

[0069] The above B content may be contained in a range of 400 to 1000 ppm based on the total mole number of metals excluding lithium in the lithium metal oxide. By coating B within the above range, both the life characteristics and capacity characteristics of the lithium secondary battery can be excellently implemented.

[0070] The cathode active material including the above lithium metal oxide particles has a discharge capacity of 222.0 mAh / g or more, specifically 223.0 mAh / g or more. In addition, the 30-cycle capacity retention rate measured in a coin half cell at an upper limit voltage of 4.3 V at 45°C is 92% or more, specifically 92.2% or more.

[0071]

[0072] The lithium metal oxide can be manufactured by a manufacturing method including a step of preparing a metal precursor; a first firing step of mixing the metal precursor, a lithium raw material, and a first Zr raw material and then firing the mixture to obtain a first fired product; and a second firing step of mixing the first fired product and a second Zr raw material and then firing the mixture to obtain a lithium metal oxide.

[0073] Hereinafter, a method for manufacturing the positive electrode active material of the present invention will be described in detail.

[0074] First, prepare a metal precursor.

[0075] The metal precursor is specifically a nickel-containing precursor, and the nickel content in the metal precursor may be 80 mol% or more based on the total mole number of the metal. Accordingly, the capacity and output characteristics of the battery can be more preferably implemented.

[0076] The above metal precursor can be manufactured according to the following manufacturing method.

[0077] For example, the precursor may be manufactured by adding a complex forming agent and a pH adjusting solution to a transition metal solution selectively containing a nickel-containing raw material, a cobalt-containing raw material, and a manganese-containing raw material, and performing a co-precipitation reaction.

[0078] The above nickel raw material is not particularly limited as long as it is used in the art for manufacturing a positive electrode active material precursor. For example, the nickel raw material may be a nickel-containing sulfate, acetate, nitrate, halide, sulfide, hydroxide, oxide or oxyhydroxide, and specifically, may be NiSO4, NiSO4·6H2O, Ni(OH)2, NiO, NiOOH, NiCO3·2Ni(OH)2·4H2O, NiC2O2·2H2O, Ni(NO3)2·6H2O, fatty acid nickel salt, nickel halide or a combination thereof, but is not limited thereto.

[0079] The above cobalt raw material is not particularly limited as long as it is used in the art for manufacturing a positive electrode active material precursor. For example, the cobalt raw material may be a cobalt-containing sulfate, acetate, nitrate, halide, sulfide, hydroxide, oxide, or oxyhydroxide, and specifically, CoSO 4, It may be, but is not limited to, CoSO4ㆍ7H2O, Co(OH)2, CoOOH, Co(OCOCH3)2ㆍ4H2O, Co(NO3)2ㆍ6H2O or a combination thereof.

[0080] The manganese raw material is not particularly limited as long as it is used in the art for manufacturing a precursor of a cathode active material. For example, the manganese raw material may be a manganese-containing sulfate, acetate, nitrate, halide, sulfide, hydroxide, oxide, oxyhydroxide, or a combination thereof, and specifically, may be a manganese salt such as MnSO4, MnCO3, Mn(NO3)2, manganese acetate, manganese dicarboxylic acid salt, manganese citrate, and manganese fatty acid salt, manganese oxide such as Mn2O3, MnO2, and Mn3O4, oxyhydroxide, manganese chloride, or a combination thereof, but is not limited thereto.

[0081] The above transition metal-containing solution may be prepared by adding a nickel raw material and optionally a cobalt raw material or a manganese raw material to a solvent, specifically, water, or a mixture of water and an organic solvent (e.g., alcohol, etc.) that can be uniformly mixed with water.

[0082] The above complexing agent-containing solution performs the role of forming a complex, and may include, but is not limited to, NH3, NH4OH, (NH4)2SO4, NH4NO3, NH4Cl, CH3COONH4, NH4CO3, or a combination thereof as a complexing agent. Meanwhile, the complexing agent-containing solution may be used in the form of an aqueous solution, and at this time, water or a mixture of water and an organic solvent (e.g., alcohol, etc.) that can be uniformly mixed with water may be used as a solvent.

[0083] The pH adjusting agent may be an aqueous solution containing a basic compound, and the basic compound may be a hydroxide of an alkali metal or alkaline earth metal such as NaOH, KOH or Ca(OH)2, a hydrate thereof or a combination thereof. The basic compound may also be used in the form of an aqueous solution, and in this case, water or a mixture of water and an organic solvent (specifically, alcohol, etc.) that is uniformly miscible with water may be used as the solvent. The pH adjusting agent may be added in an amount such that the pH of the reaction solution becomes 11 to 13.

[0084] Meanwhile, the above coprecipitation reaction can be performed at a temperature of 40°C to 70°C in an inert atmosphere such as nitrogen or argon, but is not limited thereto.

[0085] Nickel-cobalt-manganese hydroxide particles are produced by the above process and precipitated in the reaction solution. By adjusting the concentrations of the nickel-containing raw material, the cobalt-containing raw material, and the manganese-containing raw material, a precursor having a nickel (Ni) content of 60 mol% or more, specifically 80 mol% or more, based on the total metal content can be produced. The precipitated nickel-cobalt-manganese hydroxide particles can be separated by a conventional method and dried to obtain a nickel-cobalt-manganese precursor. The precursor may be secondary particles formed by agglomeration of primary particles.

[0086]

[0087] Next, a first firing step is performed in which the metal precursor, lithium raw material, and first Zr raw material are mixed and then fired for the first time to obtain a first fired product; and a second firing step is performed in which the first fired product is mixed with a second Zr raw material and then fired to obtain a lithium metal oxide.

[0088] Zr acts as a kind of filler because Zr ions occupy Li sites, alleviating the shrinkage of the lithium ion path during charge and discharge, thereby stabilizing the layered structure. This phenomenon can, in other words, reduce cation mixing and increase the lithium diffusion coefficient, thereby increasing the cycle life.

[0089] As a result, Zr doped in the transition metal site, such as cobalt or manganese, including nickel in lithium metal oxide, has a relatively strong bonding force with oxygen, which can improve the structural stability of the layered structure in the active material, thereby improving both the discharge capacity and high-temperature life characteristics of the battery.

[0090] The present invention dopes by separately introducing first Zr raw material and second Zr raw material through first and second firing as Zr raw materials. Accordingly, since the Zr element is located relatively more in the outer part compared to the center, the stress within the particle is minimized during lithium insertion / de-insertion due to charge / discharge, so that the structural stability of the active material can be more desirably improved, and as a result, the high-temperature life characteristics of the battery can be more desirably improved.

[0091] At this time, the weight ratio of the first Zr raw material to the input amount of the second Zr raw material (first Zr raw material: second Zr raw material) may be 0:100 to 95:5, and more specifically, 0:100 to 90:10, 0:100 to 80:20, or 0:100 to 75:25.

[0092] In the present invention, the Zr contained in the total Zr raw material, which is the sum of the first Zr raw material and the second Zr raw material, based on the total metal (excluding lithium) contained in the lithium metal oxide, can be adjusted to be 0.1 to 1.0 mol%, specifically 0.1 to 0.5 mol%.

[0093] If the amount of the Zr raw material input is too small, the effect of improving the high-temperature life characteristics due to the improvement in the structural stability of the positive electrode active material may be minimal, and if the amount of the Zr raw material input is too large, the discharge capacity characteristics may deteriorate.

[0094] The above Zr raw material may be at least one selected from Zr oxide, Zr hydroxide, or Zr alkoxide, and specifically may be Zr oxide (ZrO2).

[0095] Meanwhile, in the present invention, an Al raw material may be additionally mixed into the first Zr raw material and / or the second Zr raw material. The Al ions move to the tetragonal lattice site, thereby suppressing the layered structure from deteriorating into a spinel structure in which lithium ion movement is relatively difficult.

[0096] The above Al raw material may be at least one selected from Al(OH)3, Al(OH)3, Al2O3, Al2(SO4)3, Al(NO)3, or AlCl3.

[0097] The Al in the Al raw material may be mixed so that the content is 0.5 mol% or more, specifically 0.7 to 1.3 mol%, based on the total amount of metal in the precursor.

[0098] If the doped aluminum content in lithium metal oxide is too low, the improvement in lifespan characteristics due to improved structural stability of the active material may be minimal. However, if the doped aluminum content in lithium metal oxide is too high, capacity characteristics may be degraded.

[0099] The above first firing temperature may be 650 to 750°C, and specifically, 670 to 730°C, 680 to 720°C, or 690 to 710°C. When the first firing temperature satisfies the above range, there may be an advantage in that some lithium is diffused while removing moisture from the metal precursor and lithium raw material to form lithium metal oxide.

[0100] The secondary firing temperature may be 680 to 780°C, and specifically, 700 to 780°C, 720 to 760°C, or 740 to 760°C. When the secondary firing temperature satisfies the above range, there may be an advantage of improved capacity and life characteristics due to an increase in the layered structure and an improvement in structural stability.

[0101] At this time, the secondary firing temperature may be higher than the primary firing temperature, specifically 20 to 80°C higher, and more specifically 30 to 70°C, 40 to 60°C higher. In this way, since the secondary firing temperature is higher than the primary firing temperature, higher structural stability can be secured, which may have the advantage of improving capacity and life characteristics.

[0102] The above first and second firing times can be independently performed for 2 to 12 hours, and more specifically, for 3 to 8 hours. When the first and second firing times satisfy the above ranges, there may be an advantage of preventing underfiring and underfiring and improving capacity and life characteristics through an appropriate firing effect. The above firing time may refer to the firing temperature maintenance time.

[0103] Meanwhile, in this specification, Zr and Al raw materials are mainly mentioned as doping raw materials, but the effect of the doping raw material split injection doping according to the present invention can be implemented in the same way as long as the doping element is an element doped into the transition metal layer site in the layered structure of the lithium metal oxide during doping, and has a strong bonding force with oxygen and can implement the effect of improving structural stability. Specifically, it may include one or more elements selected from V, Co, Mg, Ti, Y, Sr, Nb, Ba, Ca B, W, Sc, Si, Fe, Mo, Ce, Hf, Ta, and La, and oxides, alkoxides, hydroxides, sulfates, nitrates, acetates, carbonates, oxalates, citrates, halides, or oxyhydroxides.

[0104] Accordingly, the present invention can be applied to doping raw materials such as Zr raw material, Al raw material, Mn raw material, Fe raw material, Co raw material, Ni raw material, or a combination thereof.

[0105] At this time, the ratio of the input amount of the doping raw material in the manufacturing method and the total input amount can be applied in the same manner as the Zr raw material.

[0106] The lithium raw material may include 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 raw material may be at least one selected from Li2CO3, LiNO3, LiNO2, LiOH, LiOHㆍH2O, LiH, LiF, LiCl, LiBr, LiI, CH3COOLi, Li2O, Li2SO4, CH3COOLi, or Li3C6H5O7.

[0107] The above lithium raw material can be mixed so that the molar ratio of lithium to metals other than lithium included in the final product lithium metal oxide is in the range of 0.90 to 1.20, specifically 1.00 to 1.10.

[0108]

[0109] Optionally, if necessary, after the step of forming the lithium metal oxide, a step of mixing the lithium metal oxide and the B raw material and then performing a coating heat treatment to form a B-containing coating layer may be further included.

[0110] By further forming a B-containing coating layer on the lithium metal oxide, the effect of improving the life characteristics can be more preferably implemented.

[0111] At this time, the amount of the B raw material input can be controlled so that the content of B based on the total mole number of lithium metal oxide is 400 to 1000 ppm. Accordingly, an appropriate amount of B is coated so that the life characteristics and capacity characteristics of the battery can be evenly and excellently implemented.

[0112] The above B raw material may be B(OH)3, but is not necessarily limited thereto.

[0113] The above coating heat treatment can be performed at a temperature of 250 to 350°C. When the temperature satisfies the above range during the coating heat treatment, the B coating is efficiently performed, and the effect of improving the life characteristics of the battery can be more preferably implemented.

[0114]

[0115] Through the above process, a lithium metal oxide represented by the above chemical formula 1, i.e., a positive electrode active material for a lithium secondary battery, can be manufactured.

[0116]

[0117] In addition, the method may include a step of crushing the secondary sintered product and mixing and heat-treating the crushed secondary sintered product with a coating raw material to form a coating layer.

[0118] In addition, a step of washing the secondary product after crushing may be further included, but the present invention is not particularly limited thereto.

[0119]

[0120] Another embodiment of the present invention provides a positive electrode for a lithium secondary battery including a positive electrode active material manufactured by the method for manufacturing a positive electrode active material described above.

[0121] More specifically, the positive electrode may include a positive electrode current collector and a positive electrode active material layer disposed on the positive electrode current collector, and including the positive electrode active material described above.

[0122] The positive electrode current collector is not particularly limited as long as it is conductive and does not cause a chemical change in the battery, and for example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, etc. may be used. In addition, the positive electrode current collector may typically have a thickness of 3 to 500 μm, and fine unevenness may be formed on the surface of the positive electrode 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, sheet, foil, net, porous body, foam, or non-woven fabric.

[0123] The above-described positive electrode active material layer may include a binder and / or a conductive material together with the above-described positive electrode active material.

[0124] At this time, the binder plays a role of improving the adhesion between the positive electrode active material particles and the adhesive strength between the positive electrode active material and the positive electrode current collector. Specific examples include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer rubber (EPDM rubber), sulfonated-EPDM, styrene butadiene rubber (SBR), fluororubber, or various copolymers thereof, and one kind alone or a mixture of two or more kinds thereof may be used, but is not limited thereto. The binder may be included in an amount of 1 to 30 wt% based on the total weight of the positive electrode active material layer.

[0125] And, the conductive material is used to provide conductivity to the electrode, and in the battery to be constructed, as long as it does not cause a chemical change and has electronic conductivity, it can be used without any special restrictions. Specific examples include graphite such as natural graphite or artificial graphite; carbon-based materials such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, summer black, and carbon fiber; metal powder or metal fiber such as copper, nickel, aluminum, and silver; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives, and the like. One type alone or a mixture of two or more types among these may be used, but the present invention is not limited thereto. The conductive material may typically be included in an amount of 1 to 30 wt% based on the total weight of the positive electrode active material layer.

[0126] The above positive electrode can be manufactured according to a conventional positive electrode manufacturing method, except that the above positive electrode active material is used.

[0127] Specifically, the positive electrode can be manufactured by applying a composition for forming a positive electrode active material layer, including the positive electrode active material described above and optionally a binder, a conductive agent, or a solvent, on a positive electrode current collector, followed by drying and rolling. At this time, the types and contents of the positive electrode active material, binder, and conductive agent are as described above.

[0128] The solvent may be a solvent generally used in the relevant technical field, such as dimethylsulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, or water. One of these may be used alone or a mixture of two or more thereof may be used. The amount of the solvent used is sufficient to dissolve or disperse the positive electrode active material, conductive material, and binder, taking into account the coating thickness and manufacturing yield of the slurry, and to have a viscosity that can exhibit excellent thickness uniformity when applied thereafter for manufacturing the positive electrode.

[0129] Alternatively, the positive electrode may be manufactured by casting the composition for forming the positive electrode active material layer on a separate support, and then laminating the resulting film on a positive electrode current collector by peeling it off from the support.

[0130]

[0131] Another embodiment of the present invention provides a lithium secondary battery including the positive electrode for a lithium secondary battery as described above.

[0132] The above lithium secondary battery may more specifically include a positive electrode; a negative electrode; a separator; and an electrolyte.

[0133] The above lithium secondary battery may optionally further include a battery container that houses an electrode assembly of the positive electrode, negative electrode, and separator, and a sealing member that seals the battery container.

[0134] 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.

[0135] 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.

[0136] The negative electrode active material layer may optionally include a binder and a conductive material together with the negative electrode active material. As an example, the negative electrode active material layer may be manufactured by applying a composition for forming a negative electrode active material layer comprising the negative electrode active material and optionally a binder and a conductive material onto a negative electrode current collector and drying the composition, or by casting the negative electrode forming composition onto a separate support and then laminating the resulting film onto a negative electrode current collector by peeling the film off from the support.

[0137] As the negative electrode active material, a compound capable of reversible intercalation and deintercalation of lithium may be used. Specific examples thereof include carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber, and amorphous carbon; metallic compounds capable of alloying with lithium, such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloy, Sn alloy, and Al alloy; metallic oxides capable of doping and dedoping lithium, such as SiOβ (0 < β < 2), SnO2, vanadium oxide, and lithium vanadium oxide; or composites comprising the metallic compounds and carbonaceous materials, such as Si-C composites or Sn-C composites, and any one or a mixture of two or more of these may be used. In addition, a metallic lithium thin film may be used as the negative electrode active material. In addition, both low-crystalline carbon and high-crystalline carbon may be used as the carbonaceous material. Representative examples of low-crystalline carbon include soft carbon and hard carbon, and representative examples of high-crystalline carbon include natural graphite or artificial graphite in the form of amorphous, plate-like, flaky, spherical, or fiber-like forms, Kish graphite, pyrolytic carbon, mesophase pitch-based carbon fiber, meso-carbon microbeads, mesophase pitches, and high-temperature calcined carbon such as petroleum or coal tar pitch derived cokes.

[0138] The above binder and conductive material may be the same as those described above for the positive electrode.

[0139]

[0140] The above separator separates the negative electrode and the positive electrode and provides a passage for lithium ions to move. Any separator commonly used as a separator in lithium secondary batteries can be used without any particular restrictions. In particular, a separator having low resistance to ion movement of the electrolyte and excellent electrolyte moisture absorption 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 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.

[0141]

[0142] The above electrolyte may include, but is 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.

[0143] Specifically, the organic liquid electrolyte may include an organic solvent and a lithium salt.

[0144] The organic solvent may be used without any particular limitation as long as it can serve as a medium through which ions involved in the electrochemical reaction of the battery can move. Specifically, the organic solvent may include ester solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, and ε-caprolactone; ether solvents such as dibutyl ether or tetrahydrofuran; ketone solvents such as cyclohexanone; aromatic hydrocarbon solvents such as benzene and fluorobenzene; Carbonate solvents such as dimethylcarbonate (DMC), diethylcarbonate (DEC), methylethylcarbonate (MEC), ethylmethylcarbonate (EMC), ethylene carbonate (EC), and propylene carbonate (PC); alcohol solvents such as ethyl alcohol and isopropyl alcohol; nitriles such as R-CN (wherein R is a C2 to C20 linear, branched, or cyclic hydrocarbon group, and may include a double-bonded aromatic ring or an ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; or sulfolanes can be used. Among these, a carbonate solvent is preferable, and a mixture of a cyclic carbonate (e.g., ethylene carbonate or propylene carbonate, etc.) having high ionic conductivity and high dielectric constant that can improve the charge / discharge performance of the battery and a linear carbonate compound having low viscosity (e.g., ethyl methyl carbonate, dimethyl carbonate, or diethyl carbonate, etc.) is more preferable.In this case, the performance of the electrolyte may be improved when the cyclic carbonate and the chain carbonate are mixed and used in a volume ratio of about 1:1 to about 1:9.

[0145] The lithium salt may be used without any particular limitation as long as it is a compound capable of providing lithium ions used in a lithium secondary battery. Specifically, the lithium salt may be LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAl04, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2. LiCl, LiI, or LiB(C2O4)2. It is preferable that the concentration of the lithium salt be used within the range of 0.1 to 2.0 M. When the concentration of the lithium salt is within the above range, the electrolyte can exhibit excellent electrolyte performance because it has appropriate conductivity and viscosity, and lithium ions can move effectively.

[0146] 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, hexamethylphosphoric 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 to 5 wt% based on the total weight of the electrolyte.

[0147] As described above, a lithium secondary battery including a cathode active material according to the present invention stably exhibits excellent discharge capacity, output characteristics, and capacity retention, and is therefore useful in portable devices such as mobile phones, laptop computers, and digital cameras, and electric vehicles such as hybrid electric vehicles (HEVs).

[0148] Accordingly, another embodiment of the present invention provides a battery module including the lithium secondary battery as a unit cell and a battery pack including the same.

[0149] 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.

[0150]

[0151] Hereinafter, embodiments of the present invention will be described in more detail through examples. However, the following examples are merely preferred embodiments of the present invention, and the present invention is not limited to the following examples.

[0152]

[0153] Example 1 (2-stage firing, Zr split input 70:30)

[0154] (1) Manufacturing of positive electrode active material

[0155] (Precursor preparation) Ni through coprecipitation reaction 0.9 Co 0.07 Mn 0.03 A metal precursor with the composition (OH)2 was prepared.

[0156] (1st firing) The metal precursor and the first Zr raw material of LiOH·H2O and ZrO2 prepared so that the molar ratio of lithium to the entire metal in the metal precursor (Li / Me) is 1.06 were introduced into a mixer and mechanically mixed to form a mixture.

[0157] Here, Al(OH)3 was added to the mixer so that the Al content was 0.7 to 1.3 mol% relative to the total metal excluding lithium in the lithium metal oxide.

[0158] Afterwards, the mixture was first fired at a temperature of 680 to 720°C in an oxygen atmosphere for 4 to 7 hours to form a first fired product, and then naturally cooled.

[0159] (Secondary firing) The first fired product and the first Zr raw material of ZrO2 were put into a mixer and mechanically mixed, and the resulting mixture was subjected to secondary firing at a temperature of 730 to 750°C for 4 to 7 hours in an oxygen atmosphere to form lithium metal oxide.

[0160] At this time, the input ratio of the first Zr raw material and the second Zr raw material (first Zr raw material: second Zr raw material) was set to 70:30 by weight.

[0161] The total input amount of the first Zr raw material and the second Zr raw material was set so that the content of Zr was 0.1 to 0.5 mol% based on the total mole number of metals excluding lithium in the lithium metal oxide.

[0162] (Washing and drying) After that, the lithium metal oxide was washed by placing it in distilled water at 9°C and stirring for 10 minutes, and the washed lithium metal oxide was vacuum dried at a temperature of 120°C for more than 6 hours.

[0163] (Coating) After that, the dried lithium metal oxide and B(OH)3 were mixed, and a coating heat treatment was performed at a temperature of 280℃ in an air atmosphere for 6 to 10 hours to form a coating layer. At this time, the amount of B(OH)3 added was such that the B content was 600 ppm based on the total weight of the lithium metal oxide.

[0164] (2) Manufacturing of coin-type half-cells

[0165] A coin-type half-cell was manufactured using the positive electrode active material manufactured above.

[0166] Specifically, a positive electrode active material, a carbon black conductive agent, and a polyvinylidene fluoride binder (trade name: KF1120) were mixed at a weight ratio of 96.5:1.5:1, and an appropriate amount of N-methyl-2-pyrrolidone solvent was added to the mixture to prepare a positive electrode active material slurry.

[0167] The above slurry was coated on an aluminum foil (Al foil, thickness: 20 ㎛), which is a positive electrode collector, using a doctor blade, dried, and rolled to manufacture a positive electrode. The loading amount of the positive electrode was about 15 to 17 mg / cm2, and the rolling density was about 3.4 to 3.6 g / cm 3 It was.

[0168]

[0169] *167 A 2032 coin-type half-cell was manufactured using the above positive electrode, lithium metal negative electrode (200 μm, Honzo metal), electrolyte, and polypropylene separator by a conventional method. The electrolyte was a mixed solution prepared by dissolving 1M LiPF6 in a mixed solvent of ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate (EMC) (mixing ratio EC:DMC:EMC=3:4:3 volume %).

[0170]

[0171] Example 2 (2-stage firing, Zr split input 30:70)

[0172] In the first and second firing stages, a positive electrode active material and a battery were manufactured in the same manner as in Example 1, except that the ratio of the input amounts of the first Zr raw material and the second Zr raw material was set to 30:70.

[0173]

[0174] Example 3 (2-stage firing, Zr split input 0:100)

[0175] A cathode active material and a battery were manufactured in the same manner as in Example 1, except that ZrO2 was not added in the first firing step and the entire amount of ZrO2 was added in the second firing step.

[0176]

[0177] Comparative Example 1 (2-stage firing, Zr split input 100:0)

[0178] A cathode active material and a battery were manufactured in the same manner as in Example 1, except that the entire amount of ZrO2 was added in the first firing step.

[0179]

[0180] Comparative Example 2 (1-stage firing)

[0181] Ni 0.9 Co 0.07 Mn 0.03 A cathode active material and a lithium secondary battery were manufactured in the same manner as in Example 1, except that a metal precursor having a composition of (OH)2 and LiOH·H2O, Al(OH)3 as a raw material for Al, and ZrO2 as a raw material for Zr were mixed, and then lithium metal oxide was formed through a first continuous firing at a temperature of 730 to 750°C for about 10 hours in an oxygen atmosphere. At this time, the amount of Zr raw material added was such that the doping content of Zr based on the total mole number of metals excluding lithium in the lithium metal oxide was 0.1 to 0.5 mol%. The content of Al with respect to the total metals excluding lithium in the lithium metal oxide was such that 0.7 to 1.3 mol%.

[0182]

[0183] Experimental Example 1: Evaluation of the slope of changes in Zr doping concentration

[0184] After CP (Cross section Polisher) was performed on the positive electrode active materials manufactured according to the examples and comparative examples, EDS (Energy-Dispersive Spectroscopy) line scan analysis for Zr element was performed, and the results are shown in FIGS. 1 to 4.

[0185] Fig. 1 is a cross-sectional SEM image of a positive electrode active material manufactured according to an example and a comparative example, and Fig. 2 shows the gradient of the change in Zr concentration at each location from the center to the surface of positive electrode active material particles manufactured according to an example and a comparative example.

[0186] In Fig. 1, arrows are shown positioned at a predetermined angle from the center of the cross-section of the positive electrode active material to the surface, but this is for convenience in explaining that the Zr concentration is measured on a straight line from the center to the surface, and does not mean the actual measurement position.

[0187] In Figure 2, the horizontal axis of each graph, Distance, means the distance from the center of the particle to the outermost surface concentration measurement point.

[0188] The Zr concentration was measured from the center of the particle to the outermost surface concentration measurement point, and the slope of the Zr concentration change was measured.

[0189] SEM analysis of the cross-section of the active material was performed using the ZEISS GeminiSEM 560 equipment. Afterwards, EDS Mapping and EDS line profile analysis of the cross-section were performed using the Bruker XFlash 7 EDS equipment installed in the GeminiSEM 560 equipment. After line profile analysis, the average intensity value according to the position of each element was obtained, and then a straight line was connected to calculate the slope.

[0190] Specifically, the intensity of the Zr element was measured 3 to 5 times at each position spaced apart from the particle center toward the surface at a predetermined interval (e.g., 0.5 μm), and the average value was calculated. A trend line was drawn on the dispersion diagram represented by the average value of the intensity at each position, and the slope of the trend line was taken as the slope of the change in Zr concentration.

[0191]

[0192] Referring to FIGS. 1 and 2, in the case of the positive electrode active materials manufactured according to Examples 1 and 3, it can be confirmed that the Zr concentration increases from the center of the positive electrode active material to the outermost surface, and the slopes of the change in Zr concentration measured on two or more radii forming a predetermined angle from the center of the lithium metal oxide particle toward the surface are all greater than 0 and fall within the range of 0.001 to 0.2 and the range of 0.005 to 0.1.

[0193] On the other hand, in the case of Comparative Example 1, it can be confirmed that among the two measured Zr concentration change slopes, one Zr concentration change slope is less than 0. In addition, in the case of Comparative Example 2, it can be confirmed that both of the two measured Zr concentration change slopes are less than 0.

[0194]

[0195] Experimental Example 2: XRD Analysis Results

[0196] The lattice constants of the positive electrode active materials manufactured according to the examples and comparative examples were obtained by X-ray diffraction measurement using CuKα rays. The measured a-axis length and c-axis length are shown in Table 1 below.

[0197] In addition, the crystalline size of the positive electrode active material was measured and shown in Table 1 below.

[0198] The XRD measurement conditions were 2θ = 10° to 90°, scan speed (° / min) = 10.8° / min, and step size was 0.01 / step, and the X-ray diffraction measurement test was performed.

[0199]

[0200] Experimental Example 3: Measurement of Residual Lithium and Particle Size

[0201] The residual lithium of the positive electrode active material was measured using the T50 model of METTLER TOLEDO, and the particle size was measured using the S3500 model of microtrac, and is shown in Table 1 below.

[0202]

[0203] Experimental Example 4: Evaluation of the initial discharge capacity of a battery

[0204] After aging the coin-type half-cell manufactured above at room temperature (25°C) for 10 hours, a charge / discharge test was performed.

[0205] Capacity evaluation was conducted with 200 mAh / g as the standard capacity, and charge / discharge conditions were applied with CC / CV 3.0~4.3 V and 1 / 20C cut-off.

[0206] The initial capacity was performed under 0.1C charge / 0.1C discharge conditions.

[0207] The results are shown in Table 1 below.

[0208]

[0209] Experimental Example 5: Evaluation of High-Temperature Battery Lifetime Characteristics

[0210] The coin-type half-cells manufactured above were charged to 4.3 V at a constant current of 0.5 C at 45°C, then switched to a constant voltage and charged until the termination current reached 0.05 C. After a 10-minute rest period after charging, they were discharged at a constant current of 1.0 C until the voltage reached 3.0 V. Under these charge-discharge cycle conditions, 30 charge-discharge cycles were performed, and the capacity retention rate of the 30th cycle was calculated compared to the first cycle.

[0211] The above measurement results are shown in Table 1 below.

[0212]

[0213] Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Crystalline size [nm] 108 109 113 106 122 A [Å] 2.875 2.874 8 2.874 5 2.875 22.874 2 C [Å] 14.20 6 114.20 47 14.20 55 14.20 59 14.20 47 C / A 4.94 125 4.94 11 14.94 19 04.94 084 4.94 214 Residual lithium content Li2CO3 [wt%] 0.4 0.4 0.3 3 0.3 8 0.27 Total [wt%] 0.75 0.76 0.70 74 0.6 Particle size D50 [㎛]13.413.413.413.413.4Initial Capacity(0.1C, 25 ℃)Charge [mAh / g]244.4244.2244.9240.3241.6Discharge [mAh / g]223.7223.3224.8219.2222.830th Cycle Life [%]_45℃ 0.5C / 1C92.292.792.99391.3

[0214] Referring to Table 1, it can be confirmed that in the case of Examples 1 to 3, the value of the ratio of the C-axis length to the A-axis length (C / A) in the XRD analysis is within the range of 4.9410 to 4.9420, whereas the values ​​of C / A in Comparative Examples 1 and 2 are outside the above range. In addition, referring to Table 1, in the case of Examples 1 to 3, it can be confirmed that the initial discharge capacity is 223.0 mAh / g or more and the 30-cycle high-temperature life efficiency is 92.0% or more, so that both the discharge capacity and high-temperature life characteristics of the battery are excellent.

[0215] On the other hand, in the case of Comparative Example 1, the initial discharge capacity was found to be less than 220.0 mAh / g, and in the case of Comparative Example 2, the high-temperature life efficiency was found to be less than 92%.

[0216] Therefore, it was confirmed that in the case of Comparative Examples 1 and 2, which did not satisfy the manufacturing conditions of the present invention, the discharge capacity and high-temperature life characteristics of the battery did not have excellent performance.

[0217]

[0218] Although the preferred embodiments of the present invention have been described above, the present invention is not limited thereto, and various modifications can be made within the scope of the patent claims, the detailed description of the invention, and the attached drawings, and it is obvious that this also falls within the scope of the present invention.

[0219] Accordingly, the actual scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. Lithium metal oxide particles; and Zirconium having a concentration gradient increasing from the center of the lithium metal oxide particle toward the surface; The slope value of the change in the concentration of zirconium increasing from the center toward the surface of the lithium metal oxide particle is 0.001 to 0.

2. Cathode active material for lithium secondary batteries.

2. In paragraph 1, The slope value of the change in the concentration of zirconium increasing from the center toward the surface of the lithium metal oxide particle is 0.005 to 0.

1. Cathode active material for lithium secondary batteries.

3. In paragraph 1, The content of the above zirconium is 0.1 to 0.5 mol% based on the total metal excluding lithium in the lithium metal oxide. Cathode active material for lithium secondary batteries.

4. In paragraph 1, The lithium metal oxide particles are represented by the following chemical formula 1: Cathode active material for lithium secondary batteries. [Chemical Formula 1] Li x Ni a Co b Mr c Zr d M e O2 (Here, 0.80≤x≤1.20, 0.80≤a<1.0, 0≤b≤0.20, 0≤c≤0.20, 0 <d≤0.1, 0≤e≤0.1, a+b+c+d+e=1이고, M은 Al, V, Co, Mg, Ti, Y, Sr, Nb, Ba, Ca B, W, Sc, Si, Fe, Mo, Ce, Hf, Ta 및 La 중 선택되는 1종 이상이다.) 5. In paragraph 1, The crystal grain size of the lithium metal oxide is 90 nm to 135 nm, Cathode active material for lithium secondary batteries.

6. In paragraph 1, The lithium metal oxide has a ratio of the c-axis length (C) to the a-axis length (A) (C / A) in the range of 4.9410 to 4.9420. Cathode active material for lithium secondary batteries.

7. In paragraph 1, The lithium metal oxide further includes a coating layer containing the element boron (B). Cathode active material for lithium secondary batteries.

8. In paragraph 1, The above cathode active material has a 30-cycle capacity retention rate of 92% or more measured in a coin half cell at an upper limit voltage of 4.3 V at 45°C. Cathode active material for lithium secondary batteries.

9. In paragraph 1, The above positive electrode active material has a discharge capacity of 222.0 mAh / g or more. Cathode active material for lithium secondary batteries.

10. A positive electrode for a lithium secondary battery comprising the positive electrode active material of paragraph 1.

11. A lithium secondary battery comprising the positive electrode for a lithium secondary battery of Article 10.

12. Step of preparing a metal precursor containing nickel; A step of mixing the above metal precursor, lithium raw material and first Zr raw material and then performing a first calcination to obtain a first calcined product; and A step of mixing the first sintered material and the second Zr raw material and then performing a second sintering to obtain lithium metal oxide; A method for manufacturing a cathode active material for a lithium secondary battery.

13. In paragraph 12, Based on the total weight of the first Zr raw material and the second Zr raw material, the amount of the second Zr raw material input is 100 wt% or less (excluding 0 wt%). A method for manufacturing a cathode active material for a lithium secondary battery.

14. In paragraph 12, Based on the total weight of the first Zr raw material and the second Zr raw material, the amount of the second Zr raw material input is 80 wt% or less (excluding 0 wt%). A method for manufacturing a cathode active material for a lithium secondary battery.

15. In paragraph 12, The sum of the input amounts of the first Zr raw material and the second Zr raw material is controlled so that the content of Zr in the lithium metal oxide is 0.1 to 0.5 mol% based on the total mole number of metals excluding lithium. A method for manufacturing a cathode active material for a lithium secondary battery.

16. In paragraph 12, The first Zr raw material and the second Zr raw material each independently include at least one selected from among Zr oxide, Zr hydroxide, and Zr alkoxide. A method for manufacturing a cathode active material for a lithium secondary battery.

17. In paragraph 12, The Zr concentration increases from the center of the lithium metal oxide particles to the outermost surface. A method for manufacturing a cathode active material for a lithium secondary battery.

18. In paragraph 12, The above first firing temperature is 650℃ to 750℃, A method for manufacturing a cathode active material for a lithium secondary battery.

19. In paragraph 12, The above secondary firing temperature is 680℃ to 820℃. A method for manufacturing a cathode active material for a lithium secondary battery.

20. In paragraph 12, The above secondary firing temperature is higher than the primary firing temperature. A method for manufacturing a cathode active material for a lithium secondary battery.

21. In paragraph 20, The above secondary firing temperature is 20℃ to 80℃ higher than the primary firing temperature. A method for manufacturing a cathode active material for a lithium secondary battery.

22. In paragraph 12, The above positive electrode active material precursor contains nickel (Ni) in an amount of 80 mol% or more among the total metal. A method for manufacturing a cathode active material for a lithium secondary battery.

23. In paragraph 12, The above first and second firings are performed in an oxygen atmosphere for 2 to 12 hours. A method for manufacturing a cathode active material for a lithium secondary battery.

24. In paragraph 12, After the step of forming the above lithium metal oxide, It further includes a step of mixing the lithium metal oxide and the B raw material and then performing a coating heat treatment to form a B-containing coating layer. A method for manufacturing a cathode active material for a lithium secondary battery.

25. In paragraph 24, The above coating heat treatment is performed at a temperature of 250 to 350°C. A method for manufacturing a cathode active material for a lithium secondary battery.

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