Positive electrode active material for lithium secondary batteries, method for manufacturing the same, and lithium secondary battery containing the same

Abstract

The present invention relates to a single-particle nickel-containing layered lithium transition metal oxide, having a volume-based average particle size (Dv50) of 5 to 8 μm, and containing small-particle single particles consisting of one primary particle and medium-particle quasi-single particles consisting of multiple primary particles, and exhibiting maximum peaks in the particle size range of 0.7 to 1.2 μm and 2.5 to 4.0 μm in number-based particle size distribution curve analysis.

Description

[Technical Field]

[0001] The present invention relates to a positive electrode active material for lithium secondary batteries, a method for producing the same, and a lithium secondary battery containing the same, and more specifically, to a single-particle positive electrode active material for lithium secondary batteries, a method for producing the same, and a lithium secondary battery containing the same. [Background technology]

[0002] With the increasing adoption of electric vehicles in pursuit of carbon neutrality, and the surge in demand for energy storage devices such as ESS (Energy Storage Systems) for renewable energy use, lithium-ion batteries have become an irreplaceable, core energy storage element. In particular, since the characteristics of lithium-ion batteries are greatly influenced by the cathode material, research on cathode materials accounts for the largest proportion of lithium-ion battery research.

[0003] While research on NCM cathode materials, which are layered nickel-based cathode active materials with added cobalt and manganese, is active among cathode materials, conventional research has focused more on secondary particle active materials formed by the aggregation of primary particles. However, such secondary particle active materials have a large specific surface area and low particle strength, leading to problems such as cracking and life degradation due to gas generation. In response to this, the development of single-particle cathode materials composed of a single primary particle is progressing, and these are mainly produced for use as fine-particle cathode materials with an average particle size of approximately 3-5 μm in bimodal cathode materials.

[0004] The aforementioned small-particle single particles possess excellent mechanical particle strength characteristics, resulting in superior lifespan and stability. However, due to their small size, the rolling density is low, which limits the ability to increase the electrode energy density.

[0005] To address this, attempts were made to increase the electrode energy density by increasing the particle size of individual particles. However, arbitrarily increasing the particle size of individual particles leads to a problem where the lithium ion migration path becomes longer, resulting in a decrease in the electrochemical properties related to lithium diffusion (capacity, charge / discharge efficiency, and power characteristics). [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] One objective of the present invention is to provide a positive electrode active material for lithium secondary batteries, a method for producing the same, and a lithium secondary battery containing the same, which can improve electrode energy density as a single-particle positive electrode active material and uniformly improve battery capacity, charge / discharge efficiency, and life characteristics. [Means for solving the problem]

[0007] One embodiment of the present invention provides a single-particle nickel-containing layered lithium transition metal oxide having a volume-based average particle size (Dv50) of 5 to 8 μm, containing small-particle single particles consisting of one primary particle and medium-particle quasi-single particles consisting of multiple primary particles, and having peaks in the particle size range of 0.7 to 1.2 μm and the particle size range of 2.5 to 4.0 μm in number-based particle size distribution curve analysis.

[0008] The positive electrode active material can have a compressible density of 3.6 g / cc or more after applying a pressure of 9 tons.

[0009] The number ratio of single particles to quasi-single particles (single particle:quasi-single particle) can be 8:2 to 5:5.

[0010] The positive electrode active material for the lithium secondary battery can satisfy the following formula 1.

[0011] [Formula 1] Volume-based average particle size (Dv50) - Number-based average particle size (Dn50) ≥ 3.5 μm

[0012] The lithium transition metal oxide may contain 60 mol% or more of nickel based on the total number of moles of the transition metal.

[0013] The lithium transition metal oxide can further contain a grain growth promoting element which is Zr, Al, B or a combination thereof.

[0014] The content of the grain growth promoting element can be 0.1 to 1 mol% based on the total number of moles of the transition metals.

[0015] The positive electrode active material can further include a coating layer containing Co, Al or a combination thereof on the lithium transition metal oxide.

[0016] The lithium transition metal oxide can be represented by the following Chemical Formula 1.

[0017] [Chemical Formula 1] Li a [Ni x Co y Mn z M1 w1 M2 w2 O2

[0018] In Chemical Formula 1, 0.8 ≦ a ≦ 1.2, 0.60 ≦ x < 1, 0 ≦ y ≦ 0.4, 0 ≦ z ≦ 0.4, 0 ≦ w1 ≦ 0.01, 0 ≦ w2 ≦ 0.2, x + y + z + w1 + w2 = 1, M1 is Zr, Al, B or a combination thereof, and M2 is Y, Mg, Ti, Nb, W, Sc, Si, V, Fe, Y, Mo, Ce, Hf, Ta, La, Sr or a combination thereof.

[0019] Another embodiment of the present invention provides a positive electrode for a lithium secondary battery including the positive electrode active material described above.

[0020] Another embodiment of the present invention provides a lithium secondary battery including the positive electrode for a lithium secondary battery.

Advantages of the Invention

[0021] A positive electrode active material for a lithium secondary battery according to one embodiment of the present invention has a medium-sized volume-based average particle size, and by including small and medium-sized particles, the electrode energy density can be greatly improved.

[0022] Furthermore, in the positive electrode active material for lithium secondary batteries according to one embodiment of the present invention, the small-particle active material is a single particle consisting of one primary particle, and the medium-particle active material is a quasi-single particle consisting of multiple primary particles, thereby enabling uniform improvement of battery capacity, charge / discharge efficiency, and life characteristics. [Brief explanation of the drawing]

[0023] [Figure 1] This is an SEM image of the cathode active material produced by Example 1. [Figure 2] This is an SEM image of the cathode active material produced by Comparative Example 1. [Figure 3] This is an SEM image of the cathode active material produced by Comparative Example 2. [Figure 4] This graph shows the particle size distribution curves based on the number of particles of the positive electrode active material produced by Example 1, Comparative Example 1, and Comparative Example 2. [Modes for carrying out the invention]

[0024] The terms "first," "second," and "third," etc., are used to describe various parts, components, regions, layers, and / or sections, but are not limited to these. These terms are used solely to distinguish one part, component, region, layer, or section from another part, component, region, layer, or section. Accordingly, the first part, component, region, layer, or section described below may be referred to as the second part, component, region, layer, or section, without departing from the scope of the invention.

[0025] The technical terms used herein are for the sole purpose of referring to specific embodiments and are not intended to limit the invention. The singular form used herein also includes the plural form unless the context clearly indicates the opposite. The meaning of “includes” as used in this specification is to embody a particular characteristic, area, element, stage, operation, element and / or component, and does not preclude the presence or addition of other characteristics, areas, elements, stages, operations, elements and / or components.

[0026] When a part is described as being "on top of" or "above" another part, it may be directly above or directly above the other part, or the other part may be interposed between them. In contrast, when a part is described as being "directly above" another part, the other part is not interposed between them.

[0027] Unless otherwise defined, all terms used herein, including technical and scientific terms, have the same meaning as those generally understood by a person of ordinary skill in the art to which this invention pertains. Terms defined in commonly used dictionaries are to be interpreted as having the meaning consistent with the relevant technical literature and the present disclosures, and not as ideal or highly formal unless otherwise defined.

[0028] Also, unless otherwise specified, % means weight percent, and 1 ppm is 0.0001 weight percent.

[0029] In this specification, the term “their combinations (groups)” as expressed in Markush notation means one or more mixtures or combinations selected from the group of components expressed in Markush notation, and means including one or more selected from the group of components.

[0030] The embodiments of the present invention will be described in detail below so that they can be easily implemented by a person with ordinary skill in the art to which the present invention pertains. However, the present invention can be realized in a variety of different forms and is not limited to the embodiments described herein.

[0031] One embodiment of the present invention provides a positive electrode active material for lithium secondary batteries, which is a single-particle nickel-containing layered lithium transition metal oxide with a volume-based average particle size (Dv50) of 5 to 8 μm, and includes small-particle single particles consisting of one primary particle and medium-particle quasi-single particles consisting of multiple primary particles, and has peaks in the particle size range of 0.7 to 1.2 μm and the particle size range of 2.5 to 4.0 μm in number-based particle size distribution curve analysis.

[0032] The positive electrode active material for a lithium secondary battery according to one embodiment of the present invention is composed of single-particle systems.

[0033] In this specification, "single particle" is a term used to distinguish it from positive electrode active material particles in the form of secondary particles formed by the aggregation of tens to hundreds of primary particles, which have been commonly used in the past. The term includes both a single particle consisting of one primary particle and aggregate particles of 30 or fewer primary particles. The "secondary particle" refers to an aggregate formed by the physical or chemical bonding between primary particles, i.e., a secondary structure, without any intentional aggregation or assembly process for the primary particles.

[0034] The aforementioned "primary particle" refers to the smallest particle unit that can be distinguished as a single unit when observing a cross-section of the positive electrode active material using a scanning electron microscope (SEM), and can consist of one crystal grain or multiple crystal grains.

[0035] In one embodiment of the present invention, the positive electrode active material for a lithium secondary battery is composed of single-particle systems, which increases particle strength and suppresses particle breakage during rolling. It also prevents cracks from forming between primary particles when charging and discharging is repeated, and reduces the specific surface area, thereby decreasing the amount of gas generated by side reactions with the electrolyte.

[0036] A positive electrode active material for a lithium secondary battery according to one embodiment of the present invention has a volume-based average particle size (Dv50) of 5 to 8 μm, more specifically, 5.2 to 8 μm, 5.5 to 8 μm, or 6 to 8 μm.

[0037] In this specification, the volume-based average particle size (Dv50) can be defined as the particle size corresponding to 50% of the cumulative volume in the particle size distribution curve. The average particle size (Dv50) can be measured, for example, using the laser diffraction method. The laser diffraction method can generally measure particle sizes from the submicron region to several millimeters, and can obtain highly reproducible and high-resolution results.

[0038] Because the average particle size of the positive electrode active material is sufficiently large within the aforementioned range, the tap density can be further improved compared to conventional small-particle single-particle materials, and as a result, the electrode energy density can be significantly improved.

[0039] Furthermore, the positive electrode active material for lithium secondary batteries according to one embodiment of the present invention includes both small-particle single particles consisting of one primary particle and medium-particle quasi-single particles consisting of multiple primary particles.

[0040] In this specification, "single particle" means a single particle consisting of one primary particle, and "quasi-single particle" means a single particle consisting of multiple primary particles.

[0041] By including both small and medium-sized particles in the positive electrode active material, the effect of improving electrode energy density can be further maximized.

[0042] The positive electrode active material according to the present invention has a volume-average particle size in the medium particle size range, with small particle sizes being single particles and medium particle sizes being quasi-single particles. This makes it possible to further improve the capacity, charge / discharge efficiency, and lifespan characteristics of the battery compared to an active material consisting only of single particles and an active material consisting only of quasi-single particles.

[0043] Furthermore, the aforementioned quasi-single particles can be spherical. This can further improve the electrochemical properties of the battery. In this specification, "spherical" does not necessarily mean a perfect sphere, but includes similar spherical shapes.

[0044] A positive electrode active material for a lithium secondary battery according to one embodiment of the present invention has peaks in the particle size range of 0.7 to 1.2 μm and the particle size range of 2.5 to 4.0 μm in number-based particle size distribution curve analysis.

[0045] In this specification, the number-based particle size distribution curve of the active material refers to the number-based particle size distribution curve measured using Malvern's Mastersizer 3000 equipment. This product is the most widely used laser diffraction particle size analyzer in the world. It provides a particle analysis solution down to the nanoscale and is a suitable analytical instrument for active materials containing multiple small particle sizes, as in the present invention.

[0046] In this case, the particles that form a peak in the 0.7–1.2 μm range may be mostly small single particles, while the particles that form a peak in the 2.5–4.0 μm range may be mostly medium-sized quasi-single particles.

[0047] When the range of the peak on the particle size distribution curve satisfies the aforementioned range, the aforementioned improvement in electrode energy density and the electrochemical properties of the battery can be desirablely achieved.

[0048] In particular, the positive electrode active material for the lithium secondary battery may have a number-based average particle size (Dn50) of 1.5 μm or less.

[0049] In this specification, the number-based average particle size (Dn50) can be defined as the particle size corresponding to 50% of the cumulative number of particles in the particle size distribution curve. The number-based average particle size (Dn50) can be measured, for example, using the laser diffraction method.

[0050] In other words, in a positive electrode active material according to one embodiment, the number-based average particle size (Dn50) in the aforementioned range can be significantly smaller than the volume-based average particle size (Dv50) in the medium particle size range described above. This means that there are many small-particle active materials, and as a result, the presence of multiple small particles with excellent particle strength allows the small particles to effectively fill the gaps between medium-particle particles, dramatically improving the rolling density. Furthermore, the short diffusion distance of the small particles improves the capacity and efficiency of the positive electrode active material.

[0051] More specifically, the positive electrode active material for the lithium secondary battery can satisfy the following formula 1.

[0052] [Formula 1] Volume-based average particle size (Dv50) - Number-based average particle size (Dn50) ≥ 3.5 μm

[0053] The technical significance of the positive electrode active material satisfying Equation 1 is the same as described above.

[0054] Furthermore, the positive electrode active material for the lithium secondary battery may have a particle size reference (Dn10) of 1.0 μm or less. Also, the positive electrode active material for the lithium secondary battery may have a particle size reference (Dn90) of 4 to 5.8 μm.

[0055] In this specification, the number-based particle size (Dn10) and the number-based particle size (Dn90) can be defined as the particle size corresponding to 10% and 90% of the cumulative number of particles in the particle size distribution curve, respectively.

[0056] When the number-based particle size (Dn10) and number-based particle size (Dn90) of the positive electrode active material satisfy the above range, the electrochemical properties of the battery can be more desirablely achieved.

[0057] Furthermore, the positive electrode active material for lithium secondary batteries according to one embodiment of the present invention can have a compressive density of 3.6 g / cc or more after applying a pressure of 9 tons. This physical property corresponds to the concept of the rolling density of the active material during electrode manufacturing, and having such a high compressive density can improve the electrode energy density.

[0058] In this specification, the compressive density of the active material after applying a pressure of 9 tons can be measured by loading 3g of the active material sample into a 13mm diameter pellet, applying a pressure of 9 tons using a Caver hydraulic press, and observing the change in the pellet's height before and after pressure application. The specific calculation formula is as follows.

[0059] [Formula 1] Density after applying a pressure of 9 tons = Weight of active material sample (3g) / (Φ * (1.3cm / 2)) 2 *(Change in height before and after pressure application))

[0060] In the above calculation formula 1, Φ represents pi.

[0061] On the other hand, the average number of primary particles within the quasi-single particle may be 20 or less, and more specifically, 15 or less. If the average number of primary particles within the quasi-single particle becomes very large, it will acquire polycrystalline properties, resulting in weaker particle strength, increased specific surface area, and potentially degrading the battery's lifespan characteristics.

[0062] Furthermore, the number ratio of single particles to quasi-single particles (single particle:quasi-single particle) can be 8:2 to 5:5. In this specification, the number ratio of single particles to quasi-single particles can be derived through the measurement of the number of single particles and quasi-single particles calculated by image software in a (25 μm) × (20 μm) 2D image observed on a 5,000x magnification SEM (scanning electron microscope) image. When the number ratio of single particles to quasi-single particles satisfies the above range, the aforementioned effects of improving electrode energy density and battery electrochemical properties can be more desirablely achieved.

[0063] On the other hand, the lithium transition metal oxide may contain 60 mol% or more of nickel based on the total moles of the transition metal, and more specifically, 70, 80, or 90 mol% or more. High capacity characteristics can be achieved by including such a high nickel content.

[0064] The lithium transition metal oxide may further contain grain growth promoting elements composed of Zr, Al, B, or combinations thereof. By further containing grain growth promoting elements in the lithium transition metal oxide, the firing temperature for lithium transition metal oxide formation can be lowered, crystal defects such as an increase in the positive ion mixing ratio due to high-temperature firing can be prevented, and the average particle size of single particles can be efficiently increased during the firing process.

[0065] The content of the grain growth promoting element may be 0.1 to 1 mol% based on the total number of moles of the transition metal, and more specifically, it may be 0.3 to 1 mol%. More specifically, the content of Zr may be 0.1 to 0.3 mol% based on the total number of moles of the transition metal. The content of Al may be 0.2 to 1 mol% based on the total number of moles of the transition metal. The content of B may be 0.1 to 1 mol% based on the total number of moles of the transition metal.

[0066] When the content of grain growth promoting elements satisfies the aforementioned range, the effects of adding grain growth promoting elements and the effect of preventing deterioration of electrochemical properties due to excessive addition can be achieved uniformly.

[0067] The positive electrode active material may further include a coating layer on the lithium transition metal oxide containing Co, Al, or a combination thereof. By further including a coating layer of the above composition in the positive electrode active material, side reactions with the electrolyte can be suppressed, the structural stability of the active material can be improved, and the battery life characteristics can be further improved.

[0068] Such lithium transition metal oxides according to the present invention can be represented more specifically by the following chemical formula 1.

[0069] [Chemical Formula 1] Li a [Ni x Co y Mn z M1 w1 M2 W2 O2

[0070] In Chemical Formula 1 above, 0.8 ≦ a ≦ 1.2, 0.60 ≦ x < 1, 0 ≦ y ≦ 0.4, 0 ≦ z ≦ 0.4, 0 ≦ w1 ≦ 0.01, 0 ≦ w2 ≦ 0.2, x + y + z + w1 + w2 = 1, M1 is Zr, Al, B or a combination thereof, and M2 is Y, Mg, Ti, Nb, W, Sc, Si, V, Fe, Y, Mo, Ce, Hf, Ta, La, Sr or a combination thereof.

[0071] In the lithium transition metal oxide of Chemical Formula 1 above, lithium can be contained in a content corresponding to a, that is, 0.8 ≦ a ≦ 1.2. If a is too small, the capacity may decrease. If a is too large, the strength of the fired positive electrode active material may increase and it may become difficult to pulverize, and the amount of gas generation may increase due to an increase in lithium by-products. Considering the effect of improving the capacity characteristics of the positive electrode active material by controlling the lithium content and the balance of sinterability during the production of the active material, the lithium can more preferably be contained in a content of 0.9 ≦ a ≦ 1.1.

[0072] In the lithium transition metal oxide of Chemical Formula 1 above, nickel can be contained in a content corresponding to x, that is, 0.6 ≦ x < 1, 0.6 ≦ x ≦ 0.97, 0.80 ≦ x ≦ 0.97 or 0.90 ≦ x ≦ 0.97. If the nickel content is too low, it may be difficult to increase the capacity of the battery. If the nickel content is too high, the battery life and safety may decrease due to a decrease in the structural stability of the active material.

[0073] In the lithium transition metal oxide of chemical formula 1, the cobalt content can be in the range corresponding to y, i.e., 0 ≤ y ≤ 0.4, 0 ≤ y ≤ 0.2, or 0 ≤ y ≤ 0.1. If the cobalt content is too low, it may be difficult to simultaneously achieve sufficient rate characteristics and a high powder density of the active material. If the cobalt content is too high, the overall cost of the raw materials may increase and the reversible capacity may decrease.

[0074] In the lithium transition metal oxide of chemical formula 1, manganese can be present in an amount corresponding to z, i.e., 0 ≤ z ≤ 0.4. If the manganese content is too low, the production cost will increase and the stability of the active material may decrease. If the manganese content is too high, the capacity and output characteristics of the battery may decrease.

[0075] In the lithium transition metal oxide of chemical formula 1, M1 can be contained in an amount corresponding to w1, i.e., 0 ≤ w1 ≤ 0.01. In this case, M1 is a grain growth promoting element and is Zr, Al, B, or a combination thereof.

[0076] In the lithium transition metal oxide of chemical formula 1, M2 can be contained in an amount equivalent to w2, i.e., 0 ≤ w2 ≤ 0.2. In this case, M2 is another doping element, which is Y, Mg, Ti, Nb, W, Sc, Si, V, Fe, Y, Mo, Ce, Hf, Ta, La, Sr, or a combination thereof.

[0077] A method for producing a positive electrode active material for a lithium secondary battery according to another embodiment of the present invention includes the steps of: preparing a nickel-containing transition metal precursor; forming a mixture containing the transition metal precursor and a lithium raw material, and then performing a final calcination to form a lithium transition metal oxide with an increased number of primary particles; post-calcining the lithium transition metal oxide; and pulverizing the post-calcined lithium transition metal oxide to form a lithium transition metal oxide containing small-sized single particles consisting of one primary particle and medium-sized quasi-single particles consisting of multiple primary particles.

[0078] The following describes, step by step, a method for producing a positive electrode active material for a lithium secondary battery according to another embodiment of the present invention.

[0079] First, prepare a nickel-containing transition metal precursor.

[0080] The transition metal precursor may be a transition metal hydroxide or a transition metal oxide.

[0081] The transition metal hydroxide is a positive electrode active material precursor and may be produced, for example, by adding a complexing agent-containing solution and a pH adjusting agent-containing solution to a transition metal-containing solution containing a nickel raw material and selectively a cobalt raw material or a manganese raw material, and causing a coprecipitation reaction.

[0082] The transition metal oxide may be produced by calcining a transition metal hydroxide in an oxygen or air atmosphere at a temperature of 250 to 650°C.

[0083] In this case, the average particle size (D50) of the transition metal precursor can be 5 μm or more. When the average particle size of the transition metal precursor satisfies the above range, single-particle lithium transition metal oxides of medium particle size, which are the target of the present invention, can be easily obtained.

[0084] Next, a mixture containing the transition metal precursor and lithium raw material is formed, and then calcined to form a lithium transition metal oxide with an increased number of primary particles.

[0085] More specifically, through the aforementioned calcination process, single-particle lithium transition metal oxides consisting of multiple primary particles can be formed.

[0086] Subsequently, the grown lithium transition metal oxide is calcined.

[0087] In the method for producing an active material according to one embodiment of the present invention, the firing process is carried out in two stages as described above.

[0088] In this case, the main firing temperature may be higher than the post-firing temperature, and the main firing time may be shorter than the post-firing time.

[0089] Through high-temperature, short-duration main firing, the number of primary particles within a single particle can be grown within an appropriate range. Through low-temperature, long-duration post-firing, crystal rearrangement can be induced to relieve the internal stress increased during high-temperature main firing and reduce the nickel cation mixing phenomenon. Furthermore, through the aforementioned series of high-temperature, short-duration and low-temperature, long-duration firings, the formation of active material containing small-particle single particles and medium-particle quasi-single particles can be made easier.

[0090] More specifically, conventional single particle manufacturing methods, such as a one-stage firing method involving high temperature and long firing time, have the problem of generating nickel positive ion mixing (cation mixing) and producing Rocksalt impurities. On the other hand, the manufacturing method according to one embodiment of the present invention can prevent the above problem through high temperature and short firing time and low temperature and long firing time, and can appropriately grow the number of primary particles within the single particle so that the final produced active material contains small-sized single particles and medium-sized single particles consisting of multiple primary particles.

[0091] In this case, the main firing temperature may be 850 to 900°C, and the main firing time may be 5 to 9 hours. Furthermore, the post-firing temperature may be 760 to 820°C, and the post-firing time may be 9 to 12 hours. When the main firing temperature and time, and the post-firing temperature and time, satisfy the above ranges, the active material composition and physical properties targeted by the present invention can be achieved more easily.

[0092] The lithium raw material can be lithium-containing sulfates, nitrates, acetates, carbonates, oxalates, citrates, halogen compounds, hydroxides, or oxyhydroxides, and is not particularly limited as long as it is soluble in water. Specifically, the lithium raw material can be, but is not limited to, Li2CO3, LiNO3, LiNO2, LiOH, LiOH·H2O, LiH, LiF, LiCl, LiBr, LiI, CH3COOLi, Li2O, Li2SO4, CH3COOLi, Li3C6H5O7, or a combination thereof.

[0093] The aforementioned firing can be carried out in an oxygen or air atmosphere. When firing is performed in the aforementioned atmosphere, the local oxygen partial pressure increases, which can improve the crystallinity of the positive electrode active material.

[0094] On the other hand, other doping elements can be added during the lithium transition metal oxide formation step. In this case, the other doping raw materials are added during the mixture formation process and then calcined, thereby doping the lithium transition metal oxide with other doping elements.

[0095] On the other hand, the transition metal precursor prepared in the step of preparing the transition metal precursor, or the lithium transition metal oxide formed in the step of forming a lithium transition metal oxide with an increased number of primary particles by calcination, may further contain grain growth promoting elements, which are Zr, Al, B, or combinations thereof. That is, the grain growth promoting elements can be doped in the transition metal precursor formation step, or they can be doped in the lithium transition metal oxide formation step, which is the active material.

[0096] In this case, the content of the grain growth promoting element may be 0.1 to 1 mol% based on the total number of moles of transition metal in the transition metal precursor or the lithium transition metal oxide. More specifically, the content of Zr may be 0.1 to 0.3 mol% based on the total number of moles of transition metal in the transition metal precursor or the lithium transition metal oxide. The content of Al may be 0.3 to 0.8 mol% based on the total number of moles of transition metal in the transition metal precursor or the lithium transition metal oxide. The content of B may be 0.1 to 1 mol% based on the total number of moles of transition metal.

[0097] As mentioned above, introducing pressure growth promoting elements and adjusting their content has the same technical significance as previously described, so it will be omitted here.

[0098] Next, the post-calcined lithium transition metal oxide is crushed to form lithium transition metal oxides containing small-sized single particles consisting of one primary particle and medium-sized quasi-single particles consisting of multiple primary particles. Thus, the positive electrode active material according to the present invention can be obtained.

[0099] In this case, the grinding pressure during grinding can be 2 to 4 bar.

[0100] Furthermore, the stirring speed of the grinding classifier can be set to 1,500 to 3,000 rpm.

[0101] By ensuring that the grinding pressure and classifier stirring speed during grinding meet the aforementioned ranges, it becomes easier to form small-particle single particles and medium-particle quasi-single particles with the particle size distribution and particle number targeted by the present invention as described above.

[0102] Another embodiment of the present invention provides a positive electrode active material for lithium secondary batteries in which a precursor can be obtained in this manner, and bimodal single particles and quasi-single particles can be formed through a simple process of calcination and pulverization. More specifically, conventional methods for producing bimodal positive electrode active materials require multiple calcination and subsequent mixing steps, in which small-particle active material is produced from a small-particle precursor through a first calcination step, and large-particle active material is produced from a large-particle precursor through a second calcination step separate from the first calcination step, and these small-particle and large-particle active materials are mixed. On the other hand, the positive electrode active material according to the present invention does not require a separate calcination step to produce small-particle and medium-particle active materials, and can be produced through a single calcination and pulverization step, offering process economic advantages.

[0103] If necessary, the step of forming a lithium transition metal oxide that optionally includes single particles consisting of one primary particle and spherical single particles consisting of multiple primary particles may further include the step of forming a coating layer containing Co, Al, or a combination thereof.

[0104] More specifically, the single-particle lithium transition metal oxide can be mixed with a Co raw material, an Al raw material, or a combination thereof, and then heat-treated to form a coating layer. The technical significance of forming the coating layer is the same as described above and will therefore be omitted.

[0105] Another embodiment of the present invention provides a positive electrode for a lithium secondary battery containing the positive electrode active material described above.

[0106] Another embodiment of the present invention provides a lithium secondary battery including the positive electrode. More specifically, the lithium secondary battery may include a positive electrode; a negative electrode; a separator; and an electrolyte.

[0107] Furthermore, the lithium secondary battery may selectively further include a battery container for housing the electrode assembly of the positive electrode, negative electrode, and separator, and a sealing member for sealing the battery container.

[0108] 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, which contains the positive electrode active material described above.

[0109] The positive electrode current collector is not particularly limited as long as it does not cause chemical changes in the battery and is conductive. For example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surfaces treated with carbon, nickel, titanium, silver, etc., can be used. The positive electrode current collector usually has a thickness of 3 to 500 μm, and fine irregularities can be formed on the surface of the positive electrode current collector to enhance the adhesion of the positive electrode active material. For example, it can be used in various forms such as film, sheet, foil, net, porous material, foam, nonwoven fabric, etc.

[0110] The positive electrode active material layer may include a binder and / or conductive material together with the positive electrode active material described above.

[0111] In this case, the binder plays a role in improving the adhesion between positive electrode active material particles and the adhesion 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, recycled cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer rubber (EPDM rubber), sulfonated EPDM, styrene-butadiene rubber (SBR), fluororubber, or various copolymers thereof. One of these can be used alone or a mixture of two or more, but is not limited thereto. The binder can be contained in an amount of 1 to 30% by weight relative to the total weight of the positive electrode active material layer.

[0112] The conductive material is used to impart conductivity to the electrodes and can be used in the battery without any special restrictions, as long as it does not cause chemical changes and has electronic conductivity. Specific examples include graphite such as natural graphite or artificial graphite; carbon-based materials such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, and carbon fiber; metal powders or metal fibers such as copper, nickel, aluminum, and silver; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives. One of these can be used alone or in mixtures of two or more, but this is not limited to these examples. The conductive material can usually be contained in an amount of 1 to 30% by weight relative to the total weight of the positive electrode active material layer.

[0113] The positive electrode can be manufactured by a conventional positive electrode manufacturing method, except that the positive electrode active material is used.

[0114] Specifically, the positive electrode can be manufactured by applying a composition for forming a positive electrode active material layer, which includes the positive electrode active material described above and, if necessary, selectively a binder, conductive material, or solvent, onto a positive electrode current collector, followed by drying and rolling. In this case, the types and contents of the positive electrode active material, binder, and conductive material are the same as those described above.

[0115] The solvent may be any solvent commonly used in the art, such as dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, or water. One of these may be used alone or in mixtures of two or more. The amount of solvent used should be sufficient to dissolve or disperse the cathode active material, conductive material, and binder, taking into consideration the coating thickness and production yield of the slurry, and to have a viscosity that allows for excellent thickness uniformity when applied for cathode manufacturing.

[0116] Alternatively, the positive electrode can also be manufactured by casting the positive electrode active material layer forming composition onto a separate support, peeling it off the support, and then laminating the resulting film onto the positive electrode current collector.

[0117] The negative electrode may include a negative electrode current collector and a negative electrode active material layer located on the negative electrode current collector.

[0118] The negative electrode current collector is not particularly limited as long as it does not cause chemical changes in the battery and has high conductivity. For example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., and aluminum-cadmium alloy can be used. The negative electrode current collector usually has a thickness of 3 to 500 μm, and, similar to the positive electrode current collector, fine irregularities can be formed on the surface of the current collector to strengthen the bonding force of the negative electrode active material. For example, it can be used in various forms such as film, sheet, foil, net, porous material, foam, and nonwoven fabric.

[0119] The negative electrode active material layer may selectively include a binder and a conductive material along with the negative electrode active material. For example, the negative electrode active material layer can be manufactured by applying a negative electrode active material layer forming composition, which includes the negative electrode active material and selectively a binder and a conductive material, onto a negative electrode current collector and drying it, or by casting the negative electrode forming composition onto a separate support, peeling it off the support, and laminating the resulting film onto the negative electrode current collector.

[0120] As the negative electrode active material, compounds capable of reversible intercalation and deintercalation of lithium can be used. Specific examples include carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber, and amorphous carbon; metallic compounds capable of alloying with lithium, such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloys, Sn alloys, or Al alloys; metallic oxides that can be doped and dedoped with lithium, such as SiOβ (0<β<2), SnO2, vanadium oxide, and lithium vanadium oxide; or composites containing the metallic compounds and carbonaceous materials, such as Si-C composites or Sn-C composites. One or more of these can be used. Furthermore, a metallic lithium thin film can also be used as the negative electrode active material. In addition, all types of carbon materials, including low-crystalline carbon and high-crystalline carbon, can be used. Typical examples of low-crystalline carbon include soft carbon and hard carbon, while typical examples of high-crystalline carbon include amorphous, plate-like, flake-like, spherical, or fibrous natural or artificial graphite, kish graphite, pyrolytic carbon, mesophase pitch-based carbon fiber, meso-carbon microbeads, mesophase pitches, and high-temperature calcined carbon such as petroleum and coal pitch-derived cokes.

[0121] The aforementioned binder and conductive material may be the same as those described earlier for the positive electrode.

[0122] The separator separates the negative and positive electrodes, providing a pathway for lithium ions to move. Any separator commonly used in lithium-ion secondary batteries can be used without special restrictions, and it is particularly desirable that it exhibits low resistance to ion movement in the electrolyte and excellent electrolyte moisture absorption capacity. Specifically, porous polymer films, such as those made from polyolefin polymers like ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer, and ethylene / methacrylate copolymer, or laminated structures of two or more layers thereof, can be used. Alternatively, ordinary porous nonwoven fabrics, such as those composed of high-melting-point glass fibers or polyethylene terephthalate fibers, can also be used. Furthermore, coated separators containing ceramic components or polymeric substances to ensure heat resistance or mechanical strength can be used, and they can be selectively used in single-layer or multi-layer structures.

[0123] The aforementioned electrolytes can be, 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.

[0124] Specifically, the organic liquid electrolyte may contain an organic solvent and a lithium salt.

[0125] The organic solvent can be used without special limitations as long as it can act as a medium through which ions involved in the electrochemical reaction of the battery can move. Specifically, the organic solvent may be an ester solvent such as methyl acetate, ethyl acetate, γ-butyrolactone, or ε-caprolactone; or dibutyl ether. A variety of solvents can be used, including ether solvents such as ether or tetrahydrofuran; ketone solvents such as cyclohexanone; aromatic hydrocarbon solvents such as benzene and fluorobenzene; carbonate solvents such as dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (MEC), ethyl methyl carbonate (EMC), ethylene carbonate (EC), and propylene carbonate (PC); alcohol solvents such as ethyl alcohol and isopropyl alcohol; tolyls such as R-CN (where R is a linear, branched, or cyclic hydrocarbon group of C2-C20, and may include a double-bonded aromatic ring or ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; or sulfolanes. Among these, carbonate-based solvents are preferred, and a mixture of a cyclic carbonate (e.g., ethylene carbonate or propylene carbonate) having high ionic conductivity and high dielectric constant, which can improve the charge and discharge performance of the battery, and a low-viscosity linear carbonate compound (e.g., ethyl methyl carbonate, dimethyl carbonate, or diethyl carbonate) is even more preferable. In this case, mixing the cyclic carbonate and linear carbonate in a volume ratio of approximately 1:1 to approximately 1:9 can result in superior electrolyte performance.

[0126] The lithium salt can be any compound capable of providing lithium ions for use in lithium secondary batteries, without any special limitations. Specifically, the lithium salt can be LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAlO4, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2, LiCl, LiI, or LiB(C2O4)2, etc. The lithium salt concentration is preferably used within the range of 0.1 to 2.0 M. When the lithium salt concentration falls within this range, the electrolyte has appropriate conductivity and viscosity, exhibiting excellent electrolyte performance and allowing lithium ions to move effectively.

[0127] In addition to the electrolyte components, the electrolyte may further contain one or more additives for the purpose of improving battery life characteristics, suppressing battery capacity reduction, and improving battery discharge capacity, such as haloalkylene carbonate compounds like difluoroethylene carbonate, pyridine, triethyl phosphate, triethanolamine, cyclic ethers, ethylenediamine, n-glyme, hexamethyl phosphate triamide, nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinone, N,N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salts, pyrrole, 2-methoxyethanol, or aluminum trichloride. In this case, the additive may be contained in an amount of 0.1 to 5% by weight relative to the total weight of the electrolyte.

[0128] 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.

[0129] The aforementioned battery module or battery pack can be used as a power source for one or more medium-to-large devices, including power tools; electric vehicles (EVs), hybrid electric vehicles, and plug-in hybrid electric vehicles (PHEVs); or power storage systems. [Examples]

[0130] The following examples illustrate the realization of the present invention in more detail. However, the following examples are merely preferred embodiments of the present invention, and the present invention is not limited to these examples.

[0131] Example 1 (1) Manufacture of positive electrode active material (Preparation of transition metal hydroxide) An average particle size (D50) of 7 μm was obtained by a general coprecipitation method (Ni 0.96 Co 0.03 Mn 0.01 A hydroxide with a )(OH)2 composition was prepared.

[0132] (Castration) 200g of the transition metal hydroxide and LiOH·H2O as lithium raw material 90.556g of the mixture was mixed with 20.403g of ZrO and 30.850g of Al(OH) as grain growth promoters. The mixture was then fired at 860°C for 3.8 hours, followed by firing at 790°C for 9.8 hours.

[0133] (Grinding) The calcined material was then ground at a grinding pressure of 2-4 bar and a classifier stirring speed of 1,500-3,000 rpm to form single-particle lithium transition metal oxide. At this time, the number of moles of lithium (Li), zirconium (Zr), and aluminum (Al) per mole of transition metal in the lithium transition metal oxide corresponds to 1.00, 0.0015, and 0.005 moles, respectively.

[0134] (Coating) Subsequently, 130 g of the lithium transition metal oxide was mixed with 0.560 g of LiOH·H2O, 2.504 g of Co(OH), and 30.189 g of Al(OH) to produce a mixture. This mixture was then heat-treated at 650-700°C for 15 hours to produce a positive electrode active material on which a coating layer containing 2 mol% Co and 0.2 mol% Al was formed on the surface.

[0135] (2) Manufacturing of lithium secondary batteries The slurry for manufacturing the electrode plate was prepared by mixing the manufactured positive electrode active material, conductive material (carbon black, denkablack), and binder (PVDF, KF1100) in a ratio of 96.5:1.5:2 wt%, and adjusting the viscosity by adding NMP (N-Methyl-2-pyrrolidone) so that the solid content was approximately 30%. The manufactured slurry was coated onto 15 μm thick aluminum foil using a Doctor blade, and then dry-rolled. The electrode loading amount was 15.0 mg / cm². 2 The rolling density (25°C, 20kN) is 3.6 g / cm³. 3 That was it.

[0136] The electrolyte used was 1M LiPF6in EC:DMC:EMC=3:4:3 (vol%) with 3.0 vol% VC added relative to the total electrolyte volume. Coin cells were fabricated using a PP separation membrane and a lithium anode (200 μm, honzometal).

[0137] Comparative Example 1 The positive electrode active material and lithium secondary battery were manufactured in the same manner as in Example 1, except that the grinding step was omitted.

[0138] Comparative Example 2 (1) Manufacture of positive electrode active material (Preparation of transition metal hydroxide) The average particle size (D50) is 3.5 μm (Ni) obtained by a general coprecipitation method. 0.96 Co 0.03 Mn 0.01 A hydroxide with a )(OH)2 composition was prepared.

[0139] (Casturing) 200 g of the transition metal hydroxide was mixed with 90.556 g of LiOH·H2O as a lithium raw material, 20.403 g of ZrO and 30.850 g of Al(OH) as grain growth promoters. The mixture was then calcined at 830°C for 3.8 hours, followed by calcination at 750°C for 9.8 hours.

[0140] (Grinding) The calcined material was then ground at a grinding pressure of 1 to 4 bar and a classifier stirring speed of 3,000 to 5,000 rpm to form single-particle lithium transition metal oxides. At this time, the number of moles of lithium (Li), zirconium (Zr), and aluminum (Al) per mole of transition metal in the lithium transition metal oxide was 1.00, 0.0015, and 0.005 moles, respectively.

[0141] (Coating) Subsequently, 130 g of the lithium transition metal oxide was mixed with 0.560 g of LiOH·H2O, 2.504 g of Co(OH), and 30.189 g of Al(OH) to produce a mixture. This mixture was then heat-treated at 650-700°C for 15 hours to produce a positive electrode active material on which a coating layer containing 2 mol% Co and 0.2 mol% Al was formed on the surface. Subsequently, the lithium secondary battery was manufactured in the same manner as in Example 1.

[0142] Experimental Example 1: SEM Image Observation of Active Material SEM (scanning electron microscope) images of the positive electrode active materials produced by the examples and comparative examples were observed and are shown in Figures 1 to 3, in the order of Example 1 and Comparative Examples 1 and 2, respectively.

[0143] Referring to Figures 1 to 3, it was confirmed that in Example 1, both single particles consisting of only one primary particle and quasi-single particles consisting of only multiple primary particles were included. It was also confirmed that single particles were smaller than quasi-single particles. Furthermore, it was confirmed that quasi-single particles had a nearly spherical shape, while single particles had an angular polyhedral shape.

[0144] On the other hand, in Comparative Example 2, which did not undergo a grinding process, it was confirmed that the process was carried out only with quasi-single particles.

[0145] Furthermore, in the case of Comparative Example 3, it was confirmed that the particle size was small and the process was performed only with a single particle.

[0146] Experimental Example 2: Evaluation of Active Material Properties The various physical properties of the positive electrode active materials produced by the examples and comparative examples were evaluated, and the results are summarized in Table 1 below.

[0147] (1) Evaluation of particle size distribution curve based on number For the active material powder, the particle size distribution curve based on the number of particles was evaluated using the laser diffraction method, and the particle sizes corresponding to the maximum peaks for small and medium particle sizes were measured. The results are shown in Figure 4 and Table 1, respectively.

[0148] (2) Volume-based average particle size (Dv50) evaluation For the active material powder, the particle size corresponding to 50% of the cumulative volume was measured using the laser diffraction method.

[0149] (3) Evaluation of particle size based on number (Dn10, Dn50, Dn90) For the active material powder, the particle size corresponding to 10%, 50%, and 90% of the cumulative particle count was measured using the laser diffraction method.

[0150] (4) Equation 1 evaluation Based on the above results, the value of Equation 1, defined as volume-based average particle size (Dv50) - number-based average particle size (Dn50), was calculated.

[0151] (5) Compression density (9 tons) evaluation The density was evaluated after applying a pressure of 9 tons. Specifically, 3g of the active material sample was loaded into a 13mm diameter pellet, and then a pressure of 9 tons was applied using a Caver hydraulic press. The density was then measured by the change in pellet height before and after the pressure was applied, and the specific calculation formula is as follows.

[0152] [Formula 1] Density after applying a pressure of 9 tons = Weight of active material sample (3g) / (Φ * (1.3cm / 2)) 2 *(Change in height before and after pressure application))

[0153] In the above calculation formula 1, Φ represents pi.

[0154] [Table 1]

[0155] Referring to Table 1, in the case of Example 1, which consists of bimodal particles and satisfies other conditions, a high compressive density and improved electrode energy density were expected. However, in the case of Comparative Examples 1 and 2, which consist of only single particles or only quasi-single particles, it was confirmed that the compressive density was low. Furthermore, in the case of Example 1, it was confirmed that it had an appropriate peak particle size on the particle size distribution curve and that other physical properties were appropriately obtained.

[0156] Experimental Example 3: Evaluation of Battery Electrochemical Properties The electrochemical properties of lithium secondary batteries manufactured according to the examples and comparative examples were evaluated, and the results are shown in Table 2 below. The specific experimental methods are as follows.

[0157] (1) Initial charge and discharge capacity, initial efficiency evaluation After fabricating lithium secondary battery half-cells, they were aged at 25°C for 12 hours before undergoing charge-discharge tests. For initial capacity evaluation, a reference capacity of 200mAh / g was used, and the cells were charged to 4.25V with a constant current of 0.1C. The voltage was then switched to a constant voltage and charging continued until the termination current reached 0.05C. After charging, a 10-minute rest period was observed, followed by discharging with a constant current of 0.1C (based on a reference capacity of 200mAh / g) until the voltage reached 2.5V.

[0158] (2) Evaluation of high-temperature life retention rate (45°C, 50 cycles) The high-temperature life retention rate was determined at 45°C. The battery was charged to 4.25V with a constant current of 0.5C, then switched to a constant voltage and charged until the termination current reached 0.05C. After charging, a 10-minute rest time was observed, followed by discharge at a constant current of 1.0C until the voltage reached 2.5V. Fifty charge-discharge cycles were performed under these conditions, and the capacity retention rate after the 50th cycle compared to the first cycle was calculated.

[0159] (3) Evaluation of the rate of increase in high temperature resistance (45°C, 50 cycles) The high-temperature resistance increase rate was determined at 45°C. The battery was charged to 4.25V with a constant current of 0.5C, then switched to a constant voltage and charged until the termination current reached 0.05C. After charging, a 10-minute rest time was observed, followed by discharge at a constant current of 1.0C until the voltage reached 2.5V. Fifty charge-discharge cycles were performed under these conditions, and the resistance increase rate after the 50th cycle compared to the first cycle was calculated.

[0160] [Table 2]

[0161] Referring to Table 2, it was confirmed that in Example 1, which included small-particle single particles and medium-particle quasi-single particles, and in which other physical properties such as the maximum peak range, number-based average particle size (Dn50), and Equation 1 value were appropriately adjusted, the capacity, initial efficiency, and high-temperature lifetime characteristics were all excellent.

[0162] On the other hand, in the case of Comparative Example 1, where physical properties such as the number-based average particle size (Dn50) and the value of Equation 1 exceeded the appropriate range, it was confirmed that the capacity and charge / discharge efficiency decreased.

[0163] Furthermore, in Comparative Example 2, where the volume-based average particle size (Dv50) was small and the material consisted only of single particles, and the physical properties such as the number-based average particle size (Dn50) and the value of Equation 1 exceeded the appropriate range, it was confirmed that the lifetime characteristics deteriorated.

[0164] While preferred embodiments of the present invention have been described above, the present invention is not limited thereto. Various modifications can be made within the scope of the claims, the detailed description of the invention, and the attached drawings, and these also naturally fall within the scope of the present invention.

[0165] Therefore, the substantial scope of the present invention is defined by the attached claims and their equivalents.

Claims

1. A single-particle nickel-containing layered lithium transition metal oxide, The volume-based average particle size (Dv50) is 5 to 8 μm. It includes small-sized single particles consisting of one primary particle and medium-sized quasi-single particles consisting of multiple primary particles, A positive electrode active material for lithium secondary batteries that exhibits peaks in the particle size range of 0.7 to 1.2 μm and the particle size range of 2.5 to 4.0 μm in number-based particle size distribution curve analysis.

2. The positive electrode active material for a lithium secondary battery according to claim 1, wherein the number-based average particle size (Dn50) is 1.6 μm or less.

3. A positive electrode active material for a lithium secondary battery according to claim 1 that satisfies the following formula 1: [Formula 1] Volume-based average particle size (Dv50) - Number-based average particle size (Dn50) ≥ 3.5 μm

4. The positive electrode active material for a lithium secondary battery according to claim 1, wherein the compressed density after applying a pressure of 9 tons is 3.6 g / cc or more.

5. The positive electrode active material for a lithium secondary battery according to claim 1, wherein the number ratio of single particles to quasi-single particles (single particle: quasi-single particle) is 8:2 to 5:

5.

6. The lithium transition metal oxide contains 60 mol% or more nickel based on the total number of moles of the transition metal, as described in claim 1.

7. The positive electrode active material for a lithium secondary battery according to claim 1, further comprising a grain growth promoting element, which is Zr, Al, B, or a combination thereof, as the lithium transition metal oxide.

8. The positive electrode active material for lithium secondary batteries according to claim 7, wherein the content of the grain growth promoting element is 0.1 to 1 mol% based on the total number of moles of transition metals.

9. The positive electrode active material for a lithium secondary battery according to claim 1, further comprising a coating layer containing Co, Al, or a combination thereof on the lithium transition metal oxide.

10. The lithium transition metal oxide is represented by the following chemical formula 1 and is the positive electrode active material for a lithium secondary battery according to claim 1: [Chemical formula 1] Li ａ [Ni ｘ Co ｙ Mn ｚ M1 ｗ１ M2 ｗ２ ]O ２ In the above chemical formula 1, 0.8 ≤ a ≤ 1.2, 0.60 ≤ x < 1, 0 ≤ y ≤ 0.4, 0 ≤ z ≤ 0.4, 0 ≤ w1 ≤ 0.01, 0 ≤ w2 ≤ 0.2, x + y + z + w1 + w2 = 1, M1 is Zr, Al, B or a combination thereof, and M2 is Y, Mg, Ti, Nb, W, Sc, Si, V, Fe, Y, Mo, Ce, Hf, Ta, La, Sr or a combination thereof.

11. A positive electrode for a lithium secondary battery comprising the positive electrode active material according to any one of claims 1 to 10.

12. A lithium secondary battery comprising a positive electrode for a lithium secondary battery as described in claim 11.

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