Cathode active material for lithium secondary battery, and method for manufacturing same

Abstract

A cathode active material for a lithium secondary battery, according to one embodiment of the present invention, is composed of a core part, which includes manganese, nickel and cobalt, and a boron-containing coating layer positioned on the outer surface of the core part, and can comprise a lithium metal oxide represented by chemical formula 1. [Chemical formula 1] Li1+xNiaCobMncBdMeO2-yDy In chemical formula 1, 0.1≤x≤0.15, 0.20≤a≤0.35, 0.05≤b≤0.15, 0.4≤c≤0.55, 0≤d≤0.1, 0.015≤y≤0.05, and x+a+b+c+d+e=1, M is at least one selected from Al, Ti, Nb, Ta, W, Zr, Y, Mg, Sc, Si, V, Fe, Mo, Ce, Hf, La, Sr, Sn, Sb, Zn, Cu, Ge, Mo, Ru and Ir, and D is at least one selected from F, Cl, Br and I.

Description

Cathode active material for lithium secondary batteries and method for producing the same

[0001] The present invention relates to a lithium manganese oxide-based positive electrode active material and a method for producing the same.

[0002]

[0003] Driven by the recent explosive demand for electric vehicles and the need for increased driving range, the development of high-capacity, high-energy-density lithium secondary batteries to meet these demands is actively underway worldwide.

[0004] The above lithium secondary battery is manufactured by using a material capable of reversible intercalation / deintercalation of lithium ions as a positive electrode and negative electrode active material, and filling an organic electrolyte or polymer electrolyte between the positive electrode and negative electrode.

[0005] A representative material used as a positive electrode active material in lithium secondary batteries is a lithium composite oxide. The lithium composite oxide includes oxides in which Ni, Co, Mn, or Al are composited.

[0006] Lithium composite oxides, such as commercialized nickel-cobalt-manganese (NCM), contain cobalt as an essential element to achieve a balance between electrochemical properties and stability, which are in a trade-off relationship.

[0007] However, with the recent rapid growth of the lithium secondary battery market, the cost of raw materials has also increased, facing another challenge of cost reduction. In particular, cathode active materials account for the largest proportion of costs in lithium secondary batteries, and among them, cobalt, an essential element in lithium composite oxides such as nickel-cobalt-manganese (NCM), is not only the most expensive metal, but also has relatively high supply and demand instability. Therefore, the market demand for cathode active materials that can reduce costs by adopting cobalt-free compositions is increasing.

[0008] Lithium-rich layered lithium transition metal oxides have a very high capacity of over 240 mAh / g and are attracting attention as candidates for next-generation cathode active materials, and research on them is actively being conducted recently.

[0009] Lithium-rich layered lithium metal oxide has a low content of Ni, which is expensive as a raw material, and a high content of Mn, which is relatively inexpensive, compared to general NCM cathode active materials, making it a material with good cost competitiveness. It also has high capacity because charge and discharge occur using not only the redox of the transition metal but also the redox of oxygen. To achieve ideal capacity and life performance, the oxidation state of Ni must be divalent and the oxidation state of Mn must be tetravalent. However, during the initial charge, some irreversible oxygen oxidation / reduction reactions create Mn3 on the particle surface, which induces Mn dissolution or causes side reactions with the electrolyte, resulting in voltage decrease and lifespan degradation. Therefore, by forming LiBO2 with low ionic resistance on the particle surface through a boron surface coating, side reactions can be suppressed, and the formation of Mn3, which occurs due to the irreversible oxygen oxidation / reduction reaction during the initial charge, can be suppressed, preventing voltage decrease and lifespan degradation.

[0010] As mentioned above, when boron is coated, the average oxidation value of Ni is increased, so that Mn is reduced by some irreversible oxygen oxidation / reduction reactions during initial charging. 3+ Suppresses formation and from the second charge / discharge, Ni 2+ , Mn 4+ It maintains ideal charge / discharge efficiency, capacity, and life performance. In addition, the formation of boron compounds with high ionic conductivity suppresses electrolyte side reactions without interfering with the movement of lithium ions during charge / discharge on the particle surface. However, since the degree of irreversible oxygen reaction varies depending on the composition of the lithium-excess layered lithium metal oxide, the electrochemical performance can vary significantly depending on the amount of boron coating, so optimization of the coating amount is important.

[0011]

[0012] One object of the present invention is to provide a lithium manganese-based positive electrode active material having improved capacity and cycle characteristics, and a lithium secondary battery including the same.

[0013]

[0014] A cathode active material for a lithium secondary battery according to one embodiment of the present invention comprises a core portion including manganese, nickel, and cobalt; and a boron-containing coating layer positioned on the outer surface of the core portion; and may include a lithium metal oxide represented by the following chemical formula 1.

[0015] [Chemical Formula 1]

[0016] Li 1+x Ni a Co b Mn c B d M e O 2-y D y

[0017] In the above chemical formula 1, 0.1≤x≤0.15, 0.20≤a≤0.35, 0.05≤b≤0.15, 0.4≤c≤0.55, 0≤d≤0.1, 0.015≤y≤0.05, x+a+b+c+d+e=1, M is at least one selected from Al, Ti, Nb, Ta, W, Zr, Y, Mg, Sc, Si, V, Fe, Mo, Ce, Hf, La, Sr, Sn, Sb, Zn, Cu, Ge, Mo, Ru, and Ir, and D is at least one selected from F, Cl, Br, and I.

[0018] The lithium metal oxide may contain 0.05 wt% to 2.0 wt% of boron based on the total weight of the lithium metal oxide.

[0019] The lithium metal oxide may contain 0.05 wt% to 2.0 wt% of boron based on the total weight of the lithium metal oxide.

[0020] The above coating layer may include lithium boron oxide (LiBO2).

[0021] In XPS (X-ray Photoelectron Spectroscopy), the amount of boron contained in a thickness region from the outermost surface of the surface of the lithium metal oxide to a depth of 10 nm may be 85% or more of the total boron content in the lithium metal oxide.

[0022] The thickness of the above coating layer may be 1 nm to 100 nm.

[0023] The above lithium metal oxide may have a crystal grain size of 40 nm to 70 nm as analyzed in XRD analysis.

[0024] The above positive electrode active material may have an average particle diameter (D50) of 2.0 ㎛ to 15.0 ㎛.

[0025] A method for manufacturing a cathode active material for a lithium secondary battery according to another embodiment of the present invention may include the steps of: preparing a metal precursor including manganese, nickel, and cobalt; dry mixing the metal precursor, a lithium raw material, and a halogen raw material and then calcining them to form a lithium metal oxide; and mixing the lithium metal oxide and a boron raw material and heat-treating them. The heat treatment may be performed at a temperature of 250 to 350°C.

[0026] In the step of mixing the lithium metal oxide and boron raw material and performing heat treatment, the heat treatment can be performed for 1 to 10 hours.

[0027] The step of mixing the lithium metal oxide and the boron raw material and performing heat treatment may be performed in a dry air atmosphere, an air atmosphere from which carbon dioxide has been removed, or an oxygen atmosphere.

[0028] In the step of dry mixing the above metal precursor, lithium raw material, and halogen raw material and then calcining to form lithium metal oxide, the calcination can be performed at a temperature of 700 to 950°C.

[0029] Another embodiment of the present invention provides a positive electrode for a lithium secondary battery, comprising: a current collector; and a positive electrode active material layer positioned on at least one surface of the current collector, the positive electrode active material layer including the positive electrode active material for a lithium secondary battery.

[0030] Another embodiment of the present invention provides a lithium secondary battery including the positive electrode for the lithium secondary battery.

[0031]

[0032] The positive electrode active material according to one embodiment of the present invention can implement a lithium secondary battery having excellent discharge capacity and cycle performance.

[0033]

[0034] Figure 1 is a graph showing the results of SEM analysis of the positive electrode active material according to Example 1.

[0035] Figure 2 is a graph showing the results of SEM analysis of the positive electrode active material according to Comparative Example 1.

[0036] Figure 3 is a graph showing the XPS analysis results of positive electrode active materials according to examples and comparative examples.

[0037]

[0038] In this specification, the terms first, second, and third, etc. are used to describe various parts, components, regions, layers, and / or sections, but are not limited thereto. 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.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] 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.

[0044]

[0045] 1. Cathode active material for lithium secondary batteries

[0046] A cathode active material for a lithium secondary battery according to one embodiment of the present invention comprises a core portion including manganese, nickel, and cobalt; and a boron-containing coating layer positioned on the outer surface of the core portion; and may include a lithium metal oxide including a lithium metal oxide represented by the following chemical formula 1.

[0047] [Chemical Formula 1]

[0048] Li 1+x Ni a Co b Mn c B d M e O 2-y D y

[0049] In the above chemical formula 1, 0.1≤x≤0.15, 0.25≤a≤0.35, 0.05≤b≤0.15, 0.45≤c≤0.55, 0≤d≤0.1, 0.01≤y≤0.1, x+a+b+c+d+e=1, M is at least one selected from Al, Ti, Nb, Ta, W, Zr, Y, Mg, Sc, Si, V, Fe, Mo, Ce, Hf, La, Sr, Sn, Sb, Zn, Cu, Ge, Mo, Ru, and Ir, and D is at least one selected from F, Cl, Br, and I.

[0050]

[0051] The lithium metal oxide may contain 0.2 wt% to 2.0 wt% of boron based on the total weight of the lithium metal oxide, and specifically, 0.5 wt% to 2.0 wt%, 1.0 wt% to 1.5 wt%.

[0052] In addition, in XPS (X-ray Photoelectron Spectroscopy), the amount of boron contained in a region from the outermost surface of the surface of the lithium metal oxide to a depth of 10 nm may be 50% or more of the total boron content in the lithium metal oxide, and specifically, may be 85% or more, 90% or more, or 100%.

[0053] By including boron in the above range, the average oxidation value of Ni contained in the positive electrode active material is increased, thereby reducing Mn by some irreversible oxygen oxidation / reduction reactions during initial charging. 3+ Suppresses formation and Ni from the second charge / discharge 2+ , Mn 4+ By maintaining the charge / discharge efficiency, capacity, and life performance deterioration, it is possible to prevent the deterioration of the charge / discharge efficiency and capacity. In addition, by forming a boron-containing coating layer with high ionic conductivity on the surface of the lithium metal oxide, it is possible to prevent the deterioration of the electrochemical performance of the battery by suppressing electrolyte side reactions without interfering with the movement of lithium ions on the surface of the lithium metal oxide particles during charge / discharge, which is preferable. If the boron content is below the above range, it is difficult to achieve the intended effect due to the addition of boron, and if the boron content exceeds the above range, the problem of a decrease in capacity may occur.

[0054] Although lithium metal oxide has a low nickel content, it can undergo oxidation / reduction reactions not only with the potential metal but also with anions (oxygen) during battery operation. Furthermore, excess lithium can exist in the transition metal layer as well as the lithium layer, increasing the efficiency of lithium ion insertion and deintercalation. This results in an initial discharge capacity of over 240 mAh / g, significantly improving capacity characteristics compared to conventional NCM cathode materials. Furthermore, it offers excellent cost-effectiveness, as the content of relatively expensive nickel and cobalt can be reduced and the content of inexpensive manganese can be increased.

[0055] However, lithium metal oxides with a high lithium and manganese content utilize oxygen oxidation / reduction reactions in addition to transition metal oxidation / reduction reactions due to their high lithium content and relatively low transition metal content compared to conventional cathode materials. Because these oxygen oxidation / reduction reactions are driven by high voltage during the initial charge, oxygen gas generation accelerates during subsequent cycles, degrading structural stability and reducing lifespan characteristics.

[0056] Accordingly, in the lithium metal oxide according to the present invention, some of the oxygen sites are replaced with halogen elements. As the halogen element is replaced in the lithium metal oxide, the sintering temperature for forming the lithium metal oxide can be reduced by about 100 to 200°C, and the irreversible oxygen redox reaction that typically occurs in lithium and manganese-excess oxides during charge / discharge can be suppressed, thereby improving the life characteristics.

[0057] The above halogen element may be F, Cl, Br, I or a combination thereof, and more specifically may be F.

[0058] However, in lithium and manganese-excess oxides that do not contain halogen elements, oxygen, the only anion in the composition, exists in an oxidation state of -2. However, if a halogen element with an oxidation state of -1 is substituted, the oxidation states of nickel and manganese may change. Changes in the oxidation states of nickel and manganese may cause structural instability of the active material, which may result in problems such as reduced lifespan characteristics.

[0059] In addition, the molar ratio of the halogen element to the lithium metal oxide may be 0.015 to 0.05. If the molar ratio of the halogen element is too low, the life-cycle characteristic improvement effect due to the halogen element doping mentioned above may be minimal. If the molar ratio of the halogen element is too large, the oxidation number change of nickel and manganese may occur too greatly, which may actually deteriorate the life-cycle characteristic. In addition, when the molar ratio of the halogen element satisfies the above range, the average oxidation numbers of nickel, cobalt, and manganese can be better implemented within the range according to the present invention.

[0060]

[0061] According to one embodiment of the present invention, the molar ratio of lithium to the lithium metal oxide of the positive electrode active material may be 1.05 to 1.20, more specifically, 1.10 to 1.18. If the molar ratio of lithium is too low, the average oxidation number of manganese may decrease, which may impair the structural stability of the active material and deteriorate the capacity and life characteristics. If the molar ratio of lithium is too high, the average oxidation number of nickel may increase, which may impair the structural stability of the active material and deteriorate the capacity and life characteristics.

[0062] In one embodiment of the present invention, the positive electrode active material may have a molar ratio (Ni / Me) of nickel (Ni) to a metal (Me) including lithium in the lithium metal oxide of 0.2 to 0.3, more specifically, 0.1 to 0.2. If the molar ratio of nickel is too low, the amount of nickel oxidation / reduction involved in capacity development during charge / discharge may be limited, resulting in a decrease in capacity. If the molar ratio of nickel is too high, the average oxidation number of manganese may decrease, thereby hindering the structural stability of the active material and deteriorating capacity and lifespan characteristics.

[0063] In one embodiment of the present invention, the positive electrode active material may have a molar ratio of cobalt (Co) to the total metal (Me) including lithium in the lithium metal oxide of 0.001 to 0.1, more specifically 0.02 to 0.1, or 0.02 to 0.08. If the molar ratio of cobalt is too low, the structural stability of the active material may be impaired and the capacity and lifespan characteristics may be reduced. However, if the molar ratio of cobalt, which does not undergo oxidation / reduction reactions during charge / discharge, is too large, the capacity may be reduced.

[0064] In one embodiment of the present invention, the positive electrode active material may have a molar ratio (Mn / Me) of manganese (Mn) to the total metal (Me) including lithium in the lithium metal oxide of 0.2 to 0.30, more specifically 0.22 to 0.28, 0.24 to 0.26. If the molar ratio of manganese is too low, the capacity may be limited due to oxidation of oxygen during initial charging, resulting in a decrease in capacity. If the molar ratio of manganese is too high, the specific capacity due to oxidation of oxygen during initial charging may increase, causing an irreversible oxygen oxidation / reduction reaction, resulting in a decrease in life characteristics.

[0065] According to one embodiment of the present invention, the positive electrode active material may include lithium boron oxide in the coating layer.

[0066] According to one embodiment of the present invention, the positive electrode active material has a peak B1s intensity (I) that appears between 192.0 and 193.0 eV on the surface of the lithium metal oxide in XPS (X-ray photoelectron spectroscopy). o ), the peak B1s intensity (I ) appears between 192.0 and 193.0 eV at a depth of 10 nm from the surface toward the inner center. i ) intensity ratio (I i / I o ) can be between 0.5 and 1.0.

[0067] The above intensity ratio (I i / Io ) is within the above range, a boron-containing coating layer is effectively formed on the surface of the lithium metal oxide, which is advantageous in improving the electrochemical performance of the positive electrode active material.

[0068] According to one embodiment of the present invention, the positive electrode active material may have a coating layer thickness of 1 nm to 100 nm.

[0069] When the thickness of the coating layer is within the above range, it is preferable to improve the cycle life while maintaining excellent charge / discharge capacity of the lithium secondary battery.

[0070] The positive electrode active material according to one embodiment of the present invention may have an average crystallite size obtained by XRD analysis of 40 nm to 100 nm, and specifically, 50 nm to 70 nm.

[0071] In the present invention, the crystal grain size can be calculated by the following Scherrer equation 1.

[0072] τ=(K*λ) / (β*coaθ) (1)

[0073] In the above equation 1, K is a shape factor, λ is an x-ray wavelength, β is a full width at half maximum, and θ is a Bragg angle. In the present invention, the shape factor is generally 1.0, but may vary depending on the crystallite.

[0074] When the crystal grain size according to XRD analysis is within the above range, the lithium metal oxide forms a stable structure, which is desirable because it can exhibit excellent cycle performance while maintaining high capacity.

[0075] The positive electrode active material according to one embodiment of the present invention may be a secondary particle formed by agglomerating a plurality of primary particles.

[0076] According to one embodiment of the present invention, the positive electrode active material may have an average particle diameter (D50) of 2.0 to 15.0 μm, and specifically, 9.0 μm to 13.0 μm.

[0077] When the average particle size of the positive electrode active material for the lithium secondary battery satisfies the above range, it is preferable because the volume density of the battery to which it is applied can be improved.

[0078] In the present invention, “average particle diameter (D50)” means the average of the particle diameters of 3 to 10 consecutively positioned particles observed in an SEM image. Meanwhile, the particle diameter can be calculated as the average of the longest length (major axis) in the cross-section of the particle observed in the SEM image and the longest length (minor axis) among the lengths perpendicular to the major axis.

[0079] Meanwhile, in this specification, “secondary particle” means an aggregate, i.e., a secondary structure, in which tens to hundreds of primary particles are aggregated by physical or chemical bonding between the primary particles without an intentional aggregation or assembly process for the primary particles. The “primary particle” refers to the smallest particle unit that can be distinguished as a single lump when observing a positive electrode active material through a scanning electron microscope (SEM), and may be composed of a single crystal grain or multiple crystal grains. In this specification, “crystal grain” means a distinct region in the form of a lattice structure in a certain direction of atoms within a primary particle.

[0080]

[0081] 2. Method for manufacturing positive electrode active material

[0082] A method for manufacturing a cathode active material according to another embodiment of the present invention may include the steps of: preparing a metal precursor including manganese, nickel, and cobalt; dry mixing the metal precursor, lithium raw material, and halogen raw material and then calcining them to form a lithium metal oxide; and mixing the lithium metal oxide and boron raw material and performing a heat treatment.

[0083] Hereinafter, a method for manufacturing the positive electrode active material of the present invention will be described in detail.

[0084]

[0085] First, prepare a step of preparing a metal precursor containing manganese, nickel, and cobalt.

[0086] The above metal precursor may be manufactured by, for example, adding a complexing agent-containing solution and a pH adjusting agent-containing solution to a metal-containing solution including a nickel raw material, a manganese raw material, and a cobalt raw material, and performing a co-precipitation reaction.

[0087] 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.

[0088] 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.

[0089] 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.

[0090] The above metal-containing solution may be prepared by adding nickel raw material, manganese raw material, and cobalt 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.

[0091] The above complexing agent-containing solution performs the function 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 the 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 the solvent.

[0092] The above pH adjusting agent-containing solution acts as a precipitant or pH adjusting agent, and may include an alkaline compound such as 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. Meanwhile, the pH adjusting agent-containing solution may also 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 the solvent. At this time, the pH adjusting agent-containing solution may be added in an amount such that the pH of the reaction solution becomes 10 to 13.

[0093] The above coprecipitation reaction can be performed under an inert atmosphere such as nitrogen or argon, can be performed at a temperature of 30 to 70°C, and can be performed at a pH of 10 to 13.

[0094] Nickel-manganese-cobalt hydroxide particles are generated through the above process and precipitated within the reaction solution. The precipitated precursor particles can be separated, washed, and dried using conventional methods to obtain the precursor. The precursor may be a secondary particle formed by the agglomeration of primary particles.

[0095] At this time, the molar ratio of nickel, cobalt, and manganese in the precursor can be controlled by adjusting the concentrations of the nickel raw material, cobalt raw material, and manganese raw material. That is, the concentrations of the nickel raw material, cobalt raw material, and manganese raw material can be controlled so that the molar ratio of nickel, cobalt, and manganese in the final product, lithium metal oxide, falls within the range according to the present invention.

[0096]

[0097] Next, a step of dry mixing the above metal precursor, lithium raw material, and halogen raw material and then calcining them to form a lithium metal oxide is performed.

[0098] The above metal precursor, lithium raw material, and halogen raw material can be appropriately mixed to satisfy the composition range of the positive electrode active material targeted in the present invention.

[0099] In addition, the lithium raw material may be a solid raw material, and lithium-containing sulfate, nitrate, acetate, carbonate, oxalate, citrate, halide, hydroxide or oxyhydroxide may be used, and is not particularly limited as long as it can be dissolved in water. Specifically, the lithium raw material may be Li2CO3, LiNO3, LiNO2, LiOH, LiOHㆍH2O, LiH, LiF, LiCl, LiBr, LiI, CH3COOLi, Li2O, Li2SO4, CH3COOLi, Li3C6H5O7 or a combination thereof, but is not limited thereto.

[0100] The above halogen source material may be, but is not necessarily limited to, lithium fluoride (LiF), polytetrafluoroethylene (PTFE), or a combination thereof.

[0101] The above sintering can be performed at a temperature of 700 to 950°C. If the sintering temperature is too low, uniform crystallinity cannot be secured, which may result in deterioration of capacity and life characteristics, and if the sintering temperature is too high, ionic resistance within the positive electrode particles may increase, which may result in deterioration of output characteristics.

[0102] The above firing can be performed for 1 to 20 hours, or 5 to 15 hours. If the firing time is too short, uniform crystallinity cannot be secured, which may result in reduced capacity and life characteristics, and if the firing time is too long, the process cost may increase.

[0103] The above-mentioned firing can be performed in a dry air, carbon dioxide-free air atmosphere, or oxygen atmosphere. Accordingly, there is an advantage in that side reactions occurring during the drying process can be suppressed.

[0104] Meanwhile, during the above mixing, a doping raw material may be further mixed. The doping raw material may further mix one or more of the doping elements Ti, Nb, Ta, Zr, B, Y, Mg, Sc, Si, V, Fe, Mo, Ce, Hf, La, Sr, Sn, Sb, Zn, Cu, Ge, Mo, Ru, and Ir. The type and mixing amount of the doping raw material may be adjusted depending on the composition of the intended positive electrode active material of the present invention.

[0105]

[0106] Next, a heat treatment step can be performed by mixing the lithium metal oxide formed in the above-mentioned sintering process and the boron raw material.

[0107] The above lithium metal oxide and boron raw material can be appropriately mixed to satisfy the composition range of the positive electrode active material targeted in the present invention.

[0108] The above heat treatment temperature may be 200 to 400°C, and specifically 250 to 350°C.

[0109] Meanwhile, the heat treatment time may be 1 to 10 hours, and specifically 2 to 7 hours.

[0110] If the heat treatment temperature is below the above temperature range and the heat treatment time is below the above time range, there is a problem that boron does not properly form oxide, making it difficult to obtain the desired performance improvement effect. If the heat treatment temperature exceeds the above temperature range and the heat treatment time exceeds the above time range, boron may excessively penetrate into the positive electrode active material, failing to effectively form a coating layer, resulting in a problem that the performance of the battery may deteriorate.

[0111]

[0112] The above heat treatment can be performed in a dry air or carbon dioxide-free air atmosphere. Performing the heat treatment in the above atmosphere may have the advantage of suppressing the generation of surface impurities due to reactions with moisture or carbon dioxide.

[0113]

[0114] The above heat treatment can be performed in an air atmosphere or an oxygen atmosphere.

[0115] Afterwards, a step of crushing the obtained metal oxide can be additionally performed.

[0116] The above-mentioned disintegration can be performed after cooling the metal oxide to 50 to 200°C. Cooling to the above-mentioned cooling temperature can suppress the reaction between external moisture and the sintered product and suppress the increase of residual lithium.

[0117] The above disintegration can be performed by a method commonly performed in the art.

[0118] The above-mentioned crushing can be performed using, for example, a rotor mill, a ball mill, a pin mill, a jet mill, a bead mill, or a roll mill, but is not limited thereto.

[0119] The positive electrode active material for a lithium secondary battery obtained through the above manufacturing method has been specifically described above, and is therefore omitted here.

[0120]

[0121] 3. Bipolar

[0122] In another embodiment of the present invention, a positive electrode is provided, which includes a current collector and a positive electrode active material layer positioned on at least one surface of the current collector.

[0123] The characteristics of the positive electrode active material constituting the positive electrode active material layer are the same as described above. Therefore, a detailed description of the positive electrode active material will be omitted.

[0124] The 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 adhesive strength of the positive electrode active material. For example, it may be used in various forms such as a film, sheet, foil, net, porous body, foam, or non-woven fabric.

[0125] Meanwhile, the positive electrode active material layer may include a binder and a conductive material.

[0126] 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.

[0127] And, the conductive material is used to provide conductivity to the electrode, and in the battery to be formed, as long as it does not cause a chemical change and has electronic conductivity, it can be used without any special restrictions. Specific examples include graphite such as natural graphite or artificial graphite; carbon-based materials such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, summer black, and carbon fiber; metal powder or metal fiber such as copper, nickel, aluminum, and silver; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives, and the like. One type alone or a mixture of two or more types among these may be used, but the present invention is not limited thereto. The conductive material may typically be included in an amount of 1 to 30 wt% based on the total weight of the positive electrode active material layer.

[0128] 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.

[0129] 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.

[0130] 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.

[0131] 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.

[0132] The structure and manufacturing method of the positive electrode are not limited in the present invention.

[0133]

[0134] 4. Lithium secondary battery

[0135] In another embodiment of the present invention, a lithium secondary battery including the positive electrode is provided.

[0136] The lithium secondary battery may specifically include a positive electrode, a negative electrode positioned opposite the positive electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte, wherein the positive electrode is as described above. In addition, the lithium secondary battery may optionally further include a battery container that houses an electrode assembly including the positive electrode, the negative electrode, and the separator, and a sealing member that seals the battery container.

[0137] In the above lithium secondary battery, the negative electrode may include a negative electrode current collector and a negative electrode active material layer positioned on the negative electrode current collector.

[0138] 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.

[0139] 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.

[0140] 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.

[0141] The above binder and conductive material may be the same as those described above for the positive electrode.

[0142] Next, depending on the type of lithium secondary battery, a separator may be present between the positive and negative electrodes. Such separators may include polyethylene, polypropylene, polyvinylidene fluoride, or multilayer films of two or more layers thereof, and mixed multilayer films such as a polyethylene / polypropylene two-layer separator, a polyethylene / polypropylene / polyethylene three-layer separator, or a polypropylene / polyethylene / polypropylene three-layer separator may also be used.

[0143] In addition, in the lithium secondary battery, examples of the electrolyte include, but are not limited to, organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel-type polymer electrolytes, solid inorganic electrolytes, and molten inorganic electrolytes that can be used in the manufacture of lithium secondary batteries.

[0144] Specifically, the organic liquid electrolyte may include an organic solvent and a lithium salt.

[0145] 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.

[0146] 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.

[0147] The structure and manufacturing method of the battery are not limited in the present invention.

[0148] 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).

[0149]

[0150] 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.

[0151]

[0152] (Manufacturing of positive electrode active materials)

[0153] Example 1

[0154] (Metal precursor preparation)

[0155] Ni 0.33 Co 0.09 Mn 0.58 A metal precursor with the composition (OH)2 was prepared.

[0156]

[0157] (Firing)

[0158] After mixing the metal precursor with LiOH·H2O so that the molar ratio of lithium to the entire metal in the metal precursor is 1.12 and LiF whose content is adjusted so that the molar ratio of F to lithium metal oxide is 0.05, the metal precursor is fired at 750°C for 10 hours in a dry air atmosphere to obtain Li 1.12 Ni 0.33 Co 0.09 Mn 0.58 O 1.95 F 0.05 A lithium metal oxide having the following composition was prepared.

[0159]

[0160] (Coating layer formation)

[0161] The lithium metal oxide and H3BO3 manufactured above were mixed and heat-treated at 300°C for 6 hours in a dry air atmosphere to manufacture a positive electrode active material having a boron-containing coating layer formed thereon.

[0162] At this time, H3BO3 was mixed to contain 1000 ppm of boron based on the total weight of the final positive electrode active material.

[0163]

[0164] Example 2, Comparative Examples 1 to 5

[0165] A cathode active material was manufactured in the same manner as in Example 1, except that the boron content was changed to a different amount based on the total weight of the final cathode active material.

[0166] The composition of the positive electrode active material manufactured according to Example 2 and Comparative Examples 1 to 5 is shown in Table 1 below.

[0167]

[0168] B content (ppm)F molar ratio (y)Li molar ratio (1+x)Ni molar ratio (a)Co molar ratio (b)Mn molar ratio (c)Example 11,0000.051.120.290.080.51Example 21,5000.051.120.290.080.51Comparative example 100.051.120.290.080.51Comparative example 21000.051.120.290.080.51Comparative example 33000.051.120.290.080.51Comparative example 42,0000.051.090.290.080.51Comparative example 53,0000.051.140.290.080.51 Comparative example 65,0000.051.120.290.080.51 Comparative example 710,0000.051.120.290.080.51

[0169]

[0170] (Lithium secondary battery manufacturing)

[0171] The slurry for manufacturing the electrode plate was mixed with the above-mentioned positive electrode active material: conductive material (carbon black, Denka black): binder (PVDF, KF1100) = 92.5:3.5:4 wt%, and the viscosity was adjusted so that the solid content was approximately 30% by adding NMP (N-Methyl-2-pyrrolidone). The manufactured slurry was coated on a 15 μm thick Al foil using a doctor blade, and then dried and rolled. The electrode loading was 14.6 mg / cm 2 and the rolling density (25℃, 20kN) was 3.1 g / cm 3 It was.

[0172] The electrolyte was 1M LiPF6in EC:DMC:EMC=3:4:3 (vol%), with 3.0 vol% VC added to the total amount of the electrolyte, and a coin cell was manufactured using a PP separator and a lithium negative electrode (200 μm, Honzo metal).

[0173]

[0174] Evaluation Example 1: SEM image of positive electrode active material

[0175] SEM (scanning electron microscope) images of the positive electrode active materials manufactured according to Example 1 and Comparative Example 1 were observed and are shown in FIGS. 1 and 2.

[0176] Referring to FIG. 1, it was confirmed that the positive electrode active material according to the present invention is a secondary particle formed by agglomeration of multiple primary particles.

[0177] In addition, referring to FIGS. 1 and 2, in the case of Example 1, it can be confirmed that when boron coating was applied, the primary particle shape had better inter-particle contact. This is believed to be advantageous for improving the output characteristics of the battery.

[0178]

[0179] Evaluation Example 2: XPS Analysis of Positive Electrode Active Material

[0180] XPS analysis was performed on the positive electrode active material manufactured according to Example 1 and Comparative Example 1, and the results are shown in Fig. 3.

[0181] X-ray photoelectron spectroscopy (XPS) is a method for analyzing the constituent elements and their electronic states of a sample by measuring the energy of photoelectrons generated by irradiating the sample, particularly the sample surface, with X-rays. In particular, XPS can be used for qualitative and quantitative analysis of elements present within a few nanometers of the surface, as well as analyzing the chemical bonding state that determines the characteristics of the sample.

[0182] The manufactured positive electrode active material was measured using XPS (Kratos product, Axis-NOVA X light source Monochromated-Al-Kα (1486.6 eV); measurement depth: 10 nm).

[0183] In addition, the types of boron-containing compounds included in the positive electrode active material and the boron content and ratio according to each type of compound were calculated through XPS analysis results and are shown in Table 2 below.

[0184] B in Table 2 below_LiBO2 is the B content (by weight) contained in LiBO2, and B _BO3 is the B content (by weight) contained in BO3, and B _Total is the B content (by weight) contained in the positive electrode active material.

[0185] B content (ppm) XPS analysis results at a depth of 10 nm from the top surface Content of B in LiBO2 % relative to total B (B _LiBO2 / B _Total ) Content of B in BO3 % of total B (B _BO3 / B _Total ) Content of B in BO3 relative to B in LiBO2 % (B _LiBO2 / B _BO3 ) Example 11,00010000 Example 21,50010000 Comparative Example 10---Comparative Example 210010000 Comparative Example 330010000 Comparative Example 42,00089.5%10.5%11.7% Comparative Example 53,00060.1%39.9%20.2% Comparative Example 65,00031.4%68.6%218.9% Comparative Example 710,00018.4%81.6%443.5%

[0186] Referring to Fig. 3 and Table 2, it can be confirmed that in Example 1, LiBO2 was formed on the particle surface with an appropriate amount of boron coating. On the other hand, in Comparative Example 1, the corresponding peak did not appear because boron coating was not applied.

[0187] Additionally, in the case of Comparative Examples 6 and 7, it can be confirmed that BO3 compounds as well as LiBO2 were formed due to an increase in the amount of boron coating. This is thought to be due to an increase in the content of boron oxide, a form of boron compound that is undesirable for battery performance, ultimately resulting in a deterioration in battery performance.

[0188]

[0189] Evaluation Example 3 - Electrochemical Characteristics Evaluation Analysis

[0190] (1) Initial capacity and initial efficiency evaluation

[0191] After fabricating a half-cell of a lithium secondary battery, it was aged at 45°C for 12 hours and then subjected to a charge-discharge test at 25°C. To evaluate the initial capacity, 200 mAh / g was used as the reference capacity and the battery was charged to 4.7 V at a constant current of 0.1 C. After a rest time of 20 minutes after charging, the battery was discharged to 2.5 V at a constant current of 0.1 C, using 200 mAh / g as the reference capacity. The measurement results are shown in Table 3 below.

[0192]

[0193] (2) Output characteristics evaluation

[0194] Next, each battery was charged under the same conditions as above, and then discharged at a constant current of 2C and 0.2C, respectively, until the battery voltage became 2.5 V, thereby obtaining the discharge capacities at 2C and 0.2C. The output characteristics of the battery were evaluated by expressing the ratio of the discharge capacity at 2C to the discharge capacity at 0.2C (2C / 0.2C discharge capacity ratio) as a percentage (%), and the results are shown in Table 3 below.

[0195]

[0196] (3) High-temperature life characteristics evaluation (45℃, 50 cycles)

[0197] After fabricating a lithium secondary battery half-cell, it was charged to 4.5 V at 45°C with a constant current of 0.5 C. After a rest period of 20 minutes, it was discharged at a constant current of 0.5 C until it reached 2.5 V. Under these charge-discharge cycle conditions, 50 charge-discharge cycles were performed, and the capacity retention rate of the 50th cycle compared to the first cycle was calculated, and the results are shown in Table 3 below.

[0198]

[0199] First cycle (0.1C) Output characteristics Life characteristics Charge capacity (mAh / g) Discharge capacity (mAh / g) Initial efficiency (%) 2C discharge capacity / 0.2C discharge capacity (%) 1st discharge capacity / 50th discharge capacity Example 1281.2251.089.388.9% 98.5 Example 2273.1245.089.787.1% 95.2 Comparative example 1270.8218.980.885.6% 96.6 Comparative example 2275.3228.583.086.3% 95.1 Comparative example 3268.2218.581.586.6% 97.5 Comparative example 4264.9226.585.588.7% 94.2 Comparative example 5269.1230.185.588.5%93.8Comparative example 6261.3219.684.088.3%91.5Comparative example 7255.8212.883.287.9%89.1

[0200] Referring to Table 3 above, it can be confirmed that in the case of an example in which the B content satisfies the range of the present invention, the initial discharge capacity and initial efficiency are excellent, and at the same time, the output characteristics and life characteristics are also excellent.

[0201] On the other hand, in Comparative Example 1 where no B-containing coating layer is formed, and Comparative Examples 2 to 5 where the B content is outside the range of the present invention, it can be confirmed that the initial charging and equation capacity, and initial efficiency are significantly lower than in the examples.

[0202] 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.

[0203] Accordingly, the actual scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. Core portion containing manganese, nickel and cobalt; and It is composed of a boron-containing coating layer located on the outer surface of the core portion; Comprising a lithium metal oxide represented by the following chemical formula 1, Cathode active material for lithium secondary batteries: [Chemical Formula 1] Li 1+x Ni a Co b Mr c B d M e O 2-y D y In the chemical formula 1, 0.1≤x≤0.15, 0.20≤a≤0.35, 0.05≤b≤0.15, 0.4≤c≤0.55, 0≤d≤0.1, 0.015≤y≤0.05, x+a+b+c+d+e=1, M is at least one selected from Al, Ti, Nb, Ta, W, Zr, Y, Mg, Sc, Si, V, Fe, Mo, Ce, Hf, La, Sr, Sn, Sb, Zn, Cu, Ge, Mo, Ru, and Ir, and D is at least one selected from F, Cl, Br, and I.

2. In paragraph 1, Containing 0.05 wt% to 2.0 wt% of boron based on the total weight of the lithium metal oxide, Cathode active material for lithium secondary batteries.

3. In paragraph 2, Containing 0.05 wt% to 2.0 wt% of boron based on the total weight of the lithium metal oxide, Cathode active material for lithium secondary batteries.

4. In paragraph 1, The above coating layer comprises lithium boron oxide (LiBO2). Cathode active material for lithium secondary batteries.

5. In paragraph 1, In XPS (X-ray Photoelectron Spectroscopy), the amount of boron contained in a thickness region from the outermost surface of the surface of the lithium metal oxide to a depth of 10 nm is 85% or more of the total boron content in the lithium metal oxide. Cathode active material for lithium secondary batteries.

6. In paragraph 1, The thickness of the above coating layer is 1 nm to 100 nm. Cathode active material for lithium secondary batteries.

7. In paragraph 1, The above lithium metal oxide has a crystal grain size of 40 nm to 70 nm as analyzed by XRD analysis. Cathode active material for lithium secondary batteries.

8. In paragraph 1, The above positive electrode active material has an average particle diameter (D50) of 2.0㎛ to 15.0㎛. Cathode active material for lithium secondary batteries.

9. A step of preparing a metal precursor containing manganese, nickel and cobalt; A step of dry mixing the above metal precursor, lithium raw material and halogen raw material and then calcining to form lithium metal oxide; and A step of mixing the lithium metal oxide and the boron raw material and performing heat treatment; The above heat treatment is performed at a temperature of 250 to 350°C. Method for manufacturing a cathode active material for a lithium secondary battery.

10. In paragraph 9, In the step of mixing and heat-treating the lithium metal oxide and boron raw material, The above heat treatment is performed for 1 to 10 hours. Method for manufacturing a cathode active material for a lithium secondary battery.

11. In paragraph 9, The step of mixing and heat-treating the lithium metal oxide and boron raw material is as follows: Whether it is performed in a dry air or carbon dioxide-free air atmosphere or oxygen atmosphere, Method for manufacturing a cathode active material for a lithium secondary battery.

12. In paragraph 9, In the step of dry mixing the above metal precursor, lithium raw material and halogen raw material and then calcining to form lithium metal oxide, The above firing is performed at a temperature of 700 to 950°C. Method for manufacturing a cathode active material for a lithium secondary battery.

13. The entire house; and A cathode active material layer comprising a cathode active material for a lithium secondary battery according to any one of claims 1 to 8, located on at least one surface of the above-mentioned collector; Cathode for lithium secondary batteries.

14. Containing a positive electrode for a lithium secondary battery according to Article 13, Lithium secondary battery.

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