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 positive electrode active material for lithium secondary batteries that contains a single-particle form lithium transition metal oxide containing 50 to 70 mol% nickel based on the total moles of the transition metal, and satisfies the following formula 1. [Formula 1] Dv50 / Dn50≧3.0 In the above formula 1, Dv50 is the volume-based average particle size of the positive electrode active material, and Dn50 is the number-based average particle size of the positive electrode active material.

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 method for producing a single-particle positive electrode active material for lithium secondary batteries, a positive electrode active material produced therefrom, and a lithium secondary battery containing the same. [Background technology]

[0002] In a lithium-ion secondary battery, an organic or polymer electrolyte is filled between a positive electrode and a negative electrode, both made of an active material that allows for the insertion and deintercalation of lithium ions. Electrical energy is produced by oxidation and reduction reactions that occur when lithium ions are inserted into and deintercalated at the positive and negative electrodes.

[0003] Lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), lithium manganese oxide (LiMnO2 or LiMn2O4, etc.), and lithium iron phosphate compounds (LiFePO4) have been used as positive electrode active materials for lithium secondary batteries. Among these, lithium cobalt oxide (LiCoO2) has the advantage of a high operating voltage and excellent capacity characteristics, and is widely used as a positive electrode active material for high voltage applications. However, due to the rising price and unstable supply of cobalt (Co), there are limitations to its large-scale use as a power source in fields such as electric vehicles, and the need for developing alternative positive electrode active materials has emerged.

[0004] This led to the development of nickel-cobalt-manganese lithium composite transition metal oxides (hereinafter simply referred to as "NCM-based lithium composite transition metal oxides") in which some of the cobalt (Co) is replaced with nickel (Ni) and manganese (Mn). However, conventionally developed NCM-based lithium composite transition metal oxides generally have a secondary particle form in which primary particles are aggregated, resulting in a large specific surface area, low particle strength, and a high lithium byproduct content. This leads to a large amount of gas generation during cell operation, which reduces lifespan and stability.

[0005] Therefore, development is underway on cathode active materials in single-particle form, rather than the conventional secondary particle form. [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] Therefore, one objective of the present invention is to provide a lithium transition metal oxide in single-particle form, a positive electrode active material for lithium secondary batteries with improved capacity and high-temperature lifespan, a method for producing the same, and a lithium secondary battery containing the same. [Means for solving the problem]

[0007] One embodiment of the present invention provides a positive electrode active material for a lithium secondary battery that contains a lithium transition metal oxide in single-particle form containing 50 to 70 mol% nickel based on the total moles of the transition metal, and satisfies the following formula 1.

[0008] [Formula 1] Dv50 / Dn50≧3.0

[0009] In the above formula 1, Dv50 is the volume-based average particle size of the lithium transition metal oxide, and Dn50 is the number-based average particle size of the lithium transition metal oxide.

[0010] The positive electrode active material for the lithium secondary battery can satisfy the following equation 2.

[0011] [Formula 2] Dv50-Dn50 ≥ 2.5nm

[0012] In Equation 2 above, Dv50 is the volume-based average particle size of the lithium transition metal oxide, and Dn50 is the number-based average particle size of the lithium transition metal oxide.

[0013] The volume-based average particle size (Dv50) of the lithium transition metal oxide may be 3.5 to 4.5 μm.

[0014] The number-based average particle diameter (Dn50) of the lithium transition metal oxide may be 1 μm or less.

[0015] The size of the crystallites of the lithium transition metal oxide (Crystallite size) may be 190 nm or less.

[0016] The ratio of the c-axis lattice constant to the a-axis lattice constant (Lc / La) of the lithium transition metal oxide may be 4.955 or more.

[0017] The c-axis lattice constant (Lc) of the lithium transition metal oxide may be 14.2472 nm or more.

[0018] The a-axis lattice constant (La) of the lithium transition metal oxide may be 2.8752 nm or less.

[0019] The lithium transition metal oxide is represented by the following Chemical Formula 1.

[0020] [Chemical Formula 1] Li a [Ni x Co y Mn z M w O2

[0021] In Chemical Formula 1, 0.8 ≤ a ≤ 1.2, 0.5 ≤ x ≤ 0.7, 0 ≤ y ≤ 0.2, 0 ≤ z ≤ 0.4, 0 ≤ w ≤ 0.2, x + y + z + w = 1, and M is Zr, Al, B, Y, Mg, Ti, Nb, W, Sc, Si, V, Fe, Y, Mo, Ce, Hf, Ta, La, Sr, or a combination thereof.

[0022] Another embodiment of the present invention provides a method for producing a positive electrode active material for a lithium secondary battery, comprising the steps of: preparing a transition metal precursor containing 50 to 70 mol% nickel based on the total moles of the transition metal; mixing the transition metal precursor and a lithium raw material, and then performing primary and secondary calcination to form a lithium transition metal oxide; and primary and secondary crushing of the lithium transition metal oxide to form a lithium transition metal oxide in single-particle form, wherein the secondary calcination is performed in an oxygen (O2) atmosphere.

[0023] The aforementioned secondary crushing can be performed such that the volume-based average particle size (Dv50) of the lithium transition metal oxide is 3.5 to 4.5 μm.

[0024] The aforementioned primary crushing can be carried out at a stirring speed of 15,000 to 20,000 rpm.

[0025] The aforementioned secondary crushing can be carried out at a crushing pressure of 3.5 to 4.5 bar.

[0026] The aforementioned primary firing can be carried out in an air atmosphere.

[0027] The primary and secondary firings can each be carried out independently at a temperature of 900 to 960°C.

[0028] Another embodiment of the present invention provides a positive electrode for a lithium secondary battery containing the positive electrode active material described above.

[0029] Another embodiment of the present invention provides a lithium secondary battery including the positive electrode for the lithium secondary battery. [Effects of the Invention]

[0030] The positive electrode active material for a lithium secondary battery according to one embodiment of the present invention is in single-particle form, and by appropriately adjusting the ratio of the volume-based average particle size to the number-based average particle size, not only can the capacity and electrode energy density be improved, but the high-temperature life characteristics can also be improved. [Brief explanation of the drawing]

[0031] [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. [Modes for carrying out the invention]

[0032] The terms first, second, and third 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 other parts, components, regions, layers, or sections. 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 exceeding the scope of the present invention.

[0033] 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 wording expresses a clear opposite meaning. The meaning of “including” as used in this specification does not mean that a particular characteristic, area, integer, step, operation, element, and / or component is embodied in this specification, and does not exclude the presence or addition of other characteristics, areas, integers, steps, operations, elements, and / or components.

[0034] When referring to one part being "on top of" or "on" another part, it may be directly above or on top of the other part, or there may be another part between them. In contrast, when referring to one part being "directly on top of" another part, there is no other part in between.

[0035] Unless otherwise defined, all terms used herein, including technical and scientific terms, have the same meaning as that commonly understood by a person of ordinary skill in the art to which this invention pertains. Terms defined in commonly used dictionaries are further interpreted as having the meaning consistent with the relevant technical literature and the present disclosures, and are not interpreted as having an ideal or highly formal meaning unless otherwise defined.

[0036] Also, unless otherwise specified, % means weight percent, and 1 ppm is 0.0001 weight percent.

[0037] In this specification, the term “these combinations” as described in the Markush expression means one or more mixtures or combinations selected from the group of components described in the Markush expression, and means including one or more of the selected components.

[0038] The embodiments of the present invention will be described below in detail so that those with ordinary skill in the art to which the present invention pertains can easily implement them. However, the present invention can be realized in various different forms and is not limited to the embodiments described herein.

[0039] 1.Cathode active material A positive electrode active material for a lithium secondary battery according to one embodiment of the present invention comprises a lithium transition metal oxide in single-particle form. Compared to conventional secondary particles, the single-particle active material has a smaller specific surface area, reduces the amount of gas generated by side reactions with the electrolyte, has higher particle strength, can suppress particle cracking during rolling, and can reduce the occurrence of cracks due to repeated charging and discharging. As a result, it has the advantage of superior lifespan and safety compared to secondary particles, and can achieve a high energy density of the electrode.

[0040] 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 single particles consisting of one primary particle and aggregate particles of 30 or fewer primary particles. Furthermore, "secondary particle" refers to an aggregate, i.e., a secondary structure, in which tens to hundreds of primary particles are aggregated together by physical or chemical bonding between primary particles, without any intentional aggregation or assembly process for the primary particles.

[0041] On the other hand, the lithium transition metal oxide according to one embodiment of the present invention contains 50 to 70 mol% nickel based on the total moles of the transition metal. Conventionally, NCM-based (nickel-cobalt-manganese ternary system) cathode active materials have aimed to achieve high battery capacity by increasing the nickel content. However, if the nickel content is too high, there is a thermal propagation issue, i.e., a thermal safety problem, and since nickel is expensive, the manufacturing cost increases. Therefore, in order to ensure appropriate capacity and thermal safety characteristics while achieving economic efficiency, the nickel content of the lithium transition metal oxide according to the present invention is adjusted to the above range.

[0042] However, producing lithium transition metal oxides in single-particle form requires a higher firing temperature than in secondary-particle form, which inherently leads to a decrease in capacity characteristics compared to secondary particles.

[0043] As a result of extensive research to solve the aforementioned capacity characteristic degradation problem, the inventors have discovered that capacity characteristics can be improved by appropriately adjusting the ratio of volume-average particle size (Dv50) to number-average particle size (Dn50) of the lithium transition metal oxide. Furthermore, they have discovered that high-temperature lifetime characteristics are also improved simultaneously. This will be explained in more detail below.

[0044] The positive electrode active material for a lithium secondary battery according to one embodiment of the present invention satisfies the following formula 1.

[0045] [Formula 1] Dv50 / Dn50≧3.0

[0046] In Equation 1 above, Dv50 is the volume-based average particle size of the lithium transition metal oxide, and Dn50 is the number-based average particle size of the lithium transition metal oxide. More specifically, 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 number-based average particle size (Dn50) can be defined as the particle size corresponding to 50% of the cumulative number in the particle size distribution curve. The volume-based average particle size (Dv50) and the number-based average particle size (Dn50) can be measured, for example, using the laser diffraction method.

[0047] More specifically, the Dv50 / Dn50 value of the lithium transition metal oxide is 3.5, 4.0, or 4.3 or higher, and may be 5.0 or 4.8 or lower.

[0048] Furthermore, the positive electrode active material for the lithium secondary battery can further satisfy the following formula 2.

[0049] [Formula 2] Dv50-Dn50 ≥ 2.5nm

[0050] In Equation 2 above, Dv50 is the volume-based average particle size of the lithium transition metal oxide, and Dn50 is the number-based average particle size of the lithium transition metal oxide.

[0051] More specifically, the Dv50-Dn50 value of the lithium transition metal oxide is 2.7 nm or 3.0 nm or greater, and may be 3.5 nm or 3.2 nm or less.

[0052] By satisfying Formula 1 or Formula 2, the positive electrode active material for a lithium secondary battery according to one embodiment of the present invention can not only improve capacity and electrode energy density, but also improve high-temperature life characteristics.

[0053] More specifically, the fact that the positive electrode active material satisfies Equation 1 or Equation 2 means that the number of small-sized particles is relatively greater than the number of medium-sized or large-sized particles in the overall particle size distribution. This allows small-sized particles to be present among medium-sized or large-sized particles in the actual positive electrode, improving the electrode rolling density. Furthermore, as the number of pores within the electrode decreases, the diffusion path length of lithium ions decreases, which in turn improves the lithium ion diffusion rate. As a result, good electrode energy density, capacity, and initial efficiency can be achieved.

[0054] Furthermore, the inventors confirmed that when the positive electrode active material satisfies formula 1 or formula 2, both the electrochemical properties and the high-temperature lifetime properties improve. This is thought to be because reducing the number of pores within the electrode increases the lithium ion diffusion rate, promotes the electrochemical reaction, and reduces irreversible properties.

[0055] However, if the Dv50 / Dn50 or Dv50-Dn50 values ​​are too large, it means there are too many small particles, which can increase the surface area of ​​the active material in contact with the electrolyte and potentially lead to increased gas generation due to side reactions.

[0056] More specifically, the volume-based average particle size (Dv50) of the lithium transition metal oxide is 3.5 to 4.5 μm. If the volume-based average particle size (Dv50) is too small, the electrode rolling density decreases, which can degrade the electrode energy density. If the volume-based average particle size (Dn50) is too large, the crystal grains and particle size become too large, resulting in an excessively long lithium ion transfer length and degrading the capacity and power characteristics. Furthermore, as will be explained in the manufacturing method described later, the particle size distribution of the lithium transition metal oxide is ultimately determined by adjusting the process conditions of the crushing step. However, when the volume-based average particle size (Dv50) is adjusted to the aforementioned range during the crushing step, the physical properties of equations 1 and 2 described above can be more easily satisfied.

[0057] Furthermore, the number-based average particle size (Dn50) of the lithium transition metal oxide may be 1 μm or less. By satisfying the above range for the number-based average particle size (Dn50) of the lithium transition metal oxide, not only can the electrode energy density and capacity be improved, but the high-temperature lifetime characteristics can also be improved.

[0058] On the other hand, the crystallite size of the lithium transition metal oxide is 190 nm or less, and more specifically, 185 nm or less.

[0059] In this specification, "crystal grain" refers to a region in which atoms within a primary particle form a lattice structure in a specific direction, and "crystal grain size" can be measured using peak broadening of XRD data and can be quantitatively calculated through the Scherr equation.

[0060] Generally, the larger the crystal grain size of lithium transition metal oxides, the better the lifetime characteristics become, or the worse the capacity characteristics become. On the other hand, the cathode active material according to the present invention can improve high-temperature lifetime characteristics even when the crystal grain size decreases in this way. As a result, by keeping the crystal grain size of the lithium transition metal oxide within the aforementioned range, not only can the effect of improving capacity characteristics due to the reduction in crystal grain size be achieved, but the effect of improving high-temperature lifetime characteristics can also be achieved simultaneously. This is thought to be because, as will be described later, the c-axis lattice constant of the lithium transition metal oxide according to the present invention is sufficiently large, facilitating lithium ion intercalation and reducing irreversible reactions.

[0061] On the one hand, the ratio (Lc / La) of the c-axis lattice constant to the a-axis lattice constant of the lithium transition metal oxide is 4.955 or more, more specifically 4.9553 or more. That the ratio (Lc / La) of the c-axis lattice constant to the a-axis lattice constant of the lithium transition metal oxide satisfies the above range means that the c-axis lattice constant is sufficiently larger than the a-axis lattice constant. Thereby, a good inner-layered structure of the lithium transition metal oxide can be formed, and intercalation of lithium ions can be promoted. As a result, the capacity and initial efficiency of the battery can be improved.

[0062] More specifically, the c-axis lattice constant (Lc) of the lithium transition metal oxide may be 14.2472 nm or more. Also, the a-axis lattice constant (La) of the lithium transition metal oxide may be 2.8752 nm or less.

[0063] More specifically, the lithium transition metal oxide is represented by the following Chemical Formula 1.

[0064] [Chemical Formula 1] Li a [Ni x Co y Mn z M w O2

[0065] In Chemical Formula 1, 0.8 ≦ a ≦ 1.2, 0.5 ≦ x ≦ 0.7, 0 ≦ y ≦ 0.2, 0 ≦ z ≦ 0.4, 0 ≦ w ≦ 0.2, x + y + z + w = 1, and M is Zr, Al, B, Y, Mg, Ti, Nb, W, Sc, Si, V, Fe, Y, Mo, Ce, Hf, Ta, La, Sr, or a combination thereof.

[0066] In the lithium transition metal oxide of chemical formula 1, lithium is present in an amount corresponding to a, i.e., 0.8 ≤ a ≤ 1.2. If a is too small, the capacity decreases, and if a is too large, the strength of the calcined positive electrode active material increases, making it difficult to pulverize and increasing the amount of gas generated due to an increase in lithium byproducts. Considering the effect of controlling the lithium content on improving the capacity characteristics of the positive electrode active material and the balance of sinterability during the production of the active material, the lithium is more preferably present in an amount of 0.9 ≤ a ≤ 1.1.

[0067] In the lithium transition metal oxide of chemical formula 1, nickel is present in an amount corresponding to x, i.e., 0.5 ≤ x ≤ 0.7. If the nickel content is too low, it becomes difficult to increase the battery capacity, and if the nickel content is too high, the stability of the active material structure decreases, reducing battery life and thermal safety, and increasing manufacturing costs.

[0068] In the lithium transition metal oxide of chemical formula 1, cobalt is present in a content corresponding to y, i.e., 0 ≤ y ≤ 0.2 or 0.05 ≤ y ≤ 0.2. If the cobalt content is too low, it is difficult to simultaneously achieve sufficient rate characteristics and high powder density of the active material. If the cobalt content is too high, the overall cost of the raw materials increases and the reversible capacity decreases.

[0069] In the lithium transition metal oxide of chemical formula 1, manganese is present in an amount corresponding to z, i.e., 0 ≤ z ≤ 0.4 or 0.1 ≤ z ≤ 0.4. If the manganese content is too low, production costs increase and the stability of the active material decreases. If the manganese content is too high, the capacity and output characteristics of the battery decrease.

[0070] In the lithium transition metal oxide of chemical formula 1, M is present in an amount corresponding to w, i.e., 0 ≤ w ≤ 0.2. In this case, M is a doping element and is Zr, Al, B, Y, Mg, Ti, Nb, W, Sc, Si, V, Fe, Y, Mo, Ce, Hf, Ta, La, Sr, or a combination thereof.

[0071] 2. Method for manufacturing positive electrode active material Another embodiment of the present invention provides a method for producing a positive electrode active material for a lithium secondary battery, comprising the steps of: preparing a transition metal precursor containing 50 to 70 mol% nickel based on the total moles of the transition metal; mixing the transition metal precursor and a lithium raw material, and then performing primary and secondary calcination to form a lithium transition metal oxide; and primary and secondary crushing of the lithium transition metal oxide to form a lithium transition metal oxide in single-particle form, wherein the secondary calcination is performed in an oxygen (O2) atmosphere.

[0072] 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.

[0073] First, prepare a transition metal precursor containing 50-70 mol% nickel based on the total moles of the transition metal.

[0074] The transition metal precursor may be a transition metal hydroxide.

[0075] The transition metal hydroxide 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 then causing a coprecipitation reaction.

[0076] The nickel raw material is not particularly limited as long as it is used in the industry during the production of cathode active material precursors. For example, the nickel raw material is nickel-containing sulfate, acetate, nitrate, halide, sulfide, hydroxide, oxide or oxyhydroxide, and is specifically, but not limited to, 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 combinations thereof.

[0077] The aforementioned cobalt raw material is not particularly limited as long as it is used in the industry during the production of cathode active material precursors. For example, the aforementioned cobalt raw material is a cobalt-containing sulfate, acetate, nitrate, halide, sulfide, hydroxide, oxide or oxyhydroxide, and is specifically, but not limited to, CoSO4, CoSO4·7H2O, Co(OH)2, CoOOH, Co(OCOCH3)2·4H2O, Co(NO3)2·6H2O or a combination thereof.

[0078] The manganese raw material is not particularly limited as long as it is used in the industry during the production of cathode active material precursors. For example, the manganese raw material is a manganese-containing sulfate, acetate, nitrate, halide, sulfide, hydroxide, oxide, oxyhydroxide or a combination thereof, specifically a manganese salt such as MnSO4, MnCO3, Mn(NO3)2, manganese acetate, manganese dicarboxylate, manganese citrate and manganese fatty acid salts, manganese oxide such as Mn2O3, MnO2 and Mn3O4, oxyhydroxide, manganese chloride or a combination thereof, or is not limited thereto.

[0079] The transition metal-containing solution may be prepared by adding a nickel raw material and, selectively, a cobalt raw material or a manganese raw material to a solvent, specifically water, or a mixture of water and an organic solvent (e.g., alcohol) that can be homogeneously mixed with water.

[0080] The complexing agent-containing solution plays a role in complex formation and may, but is not limited to, NH3, NH4OH, (NH4)2SO4, NH4NO3, NH4Cl, CH3COONH4, NH4CO3, or combinations thereof as the complexing agent. On the other hand, the complexing agent-containing solution can be used in aqueous solution form, in which case water or a mixture of water and an organic solvent that can be homogeneously mixed with water (e.g., alcohol) can be used as the solvent.

[0081] The pH adjusting agent-containing solution may serve as a precipitant or pH adjuster and may contain alkali metal or alkaline earth metal hydroxides such as NaOH, KOH, or Ca(OH)2, their hydrates, or combinations thereof. Alternatively, the pH adjusting agent-containing solution may also be used in aqueous solution form, in which case water or a mixture of water and an organic solvent (e.g., alcohol) that is homogeneously miscible with water may be used as the solvent. In this case, the pH adjusting agent-containing solution may be added in an amount that brings the pH of the reaction solution to 11-13.

[0082] The aforementioned coprecipitation reaction can be carried out under an inert atmosphere such as nitrogen or argon, at a temperature of 30-70°C, and at a pH of 11-13.

[0083] Through the process described above, nickel-cobalt-manganese (-doped element) hydroxide particles are generated and precipitate in the reaction solution. The precipitated precursor particles can be separated by conventional methods, washed with water, and dried to obtain the precursor. The precursor may also be secondary particles formed by the aggregation of primary particles.

[0084] At this time, the molar ratio of nickel, cobalt, and manganese in the precursor can be adjusted by controlling the concentrations of the nickel raw material, cobalt raw material, and manganese raw material.

[0085] As a result, the nickel content in the transition metal precursor may be 50 to 70 mol% based on the total number of moles of the transition metal. The technical significance of adjusting the nickel content in the transition metal precursor is as described above and will therefore be omitted.

[0086] Next, the transition metal precursor and lithium raw material are mixed, and then primary and secondary calcination is performed to form a lithium transition metal oxide.

[0087] Conventionally, the formation of lithium transition metal oxides in single-particle form was carried out solely by a high-temperature, long-duration primary calcination. However, this method had problems with the electrochemical properties of the active material degrading due to over-calcination, such as nickel cation mixing and the formation of a Rocksalt impurity phase. In contrast, the manufacturing method according to the present invention prevents these problems by performing the calcination in two stages, thereby improving the particle strength of the active material and increasing the production volume.

[0088] At this time, the atmosphere during the primary firing is not particularly limited. For example, it can be carried out in an air or oxygen (O2) atmosphere, but more specifically, it can be carried out in an air atmosphere. When a high-nickel composition cathode active material is fired in an air atmosphere, layered crystal structure formation does not occur well, resulting in a significant decrease in electrochemical properties, so it is generally common to fire it in an oxygen atmosphere. On the other hand, when the nickel content is relatively low, as in the present invention, firing in an air atmosphere does not cause a significant decrease in electrochemical properties, and process costs can be reduced.

[0089] In particular, the secondary calcination is carried out in an oxygen (O2) atmosphere. More specifically, the oxygen atmosphere may have an oxygen partial pressure of 90%, 95%, 97%, or 99% or higher. Secondary calcination in an oxygen atmosphere allows for an appropriate increase in the proportion of small-particles, i.e., fine powder, during the crushing process described later, and the obtained positive electrode active material can satisfy the physical properties of formula 1 and other equations described above. This is thought to be because the particle strength of the lithium transition metal oxide obtained when performing secondary calcination in an oxygen atmosphere is weaker than when performing secondary calcination in an air atmosphere. In particular, unlike conventional techniques that arbitrarily increase the particle strength of lithium transition metal oxide to improve lifetime characteristics, the present invention makes it possible to simultaneously improve capacity and lifetime characteristics by forming a lithium transition metal oxide with somewhat weaker particle strength and then appropriately forming the proportion of fine powder through crushing.

[0090] The primary and secondary firings can each be carried out independently at temperatures of 900-960°C. If the primary and secondary firing temperatures are too low, single-particle lithium transition metal oxides will not form easily. If the primary and secondary firing temperatures are too high, over-firing will occur, and electrochemical properties such as capacity will deteriorate.

[0091] The aforementioned primary calcination can be carried out for 2 to 6 hours. If the primary calcination time is too short, there is a problem in that lithium ions cannot be properly inserted into the precursor, and if the primary calcination time is too long, there is a problem in that it becomes difficult to disintegrate due to overcalcination, and the production rate is reduced.

[0092] The aforementioned secondary firing can be performed for 7 to 14 hours. If the secondary firing time is too short, the particles will not develop the correct single-particle shape, and there will not be enough annealing time to create a layered structure, resulting in electrochemically inferior performance. If the secondary firing time is too long, there will be a problem of capacity reduction due to over-firing.

[0093] Next, the lithium transition metal oxide is subjected to primary and secondary decomposition to form lithium transition metal oxide in single-particle form.

[0094] By dividing the crushing process into primary and secondary crushing, aggregated secondary particles can be efficiently dissolved into single-particle form, increasing the proportion of small-particle size, i.e., fine powder, and allowing the obtained positive electrode active material to satisfy the physical properties of the aforementioned formula 1 or formula 2.

[0095] The aforementioned primary crushing can be carried out using crushing equipment commonly used in this industry. For example, the primary crushing can be carried out using a rotor mill, but is not necessarily limited to this.

[0096] At this time, the primary crushing can be carried out at a stirring speed of 15,000 to 20,000 rpm. When the stirring speed during primary crushing is within the above range, as primary crushing is carried out with appropriate force, the proportion of small-sized particles, i.e., fine powder, can be appropriately controlled, and the resulting positive electrode active material can satisfy the physical properties of Equation 1 and other formulas described above.

[0097] The aforementioned secondary crushing can be carried out using crushing equipment commonly used in this industry. For example, the secondary crushing is carried out using a jet mill, but is not necessarily limited to this.

[0098] At this time, the secondary crushing can be performed so that the volume-based average particle size (Dv50) of the lithium transition metal oxide is 3.5 to 4.5 μm. As the secondary crushing is adjusted so that the volume-based average particle size (Dv50) of the lithium transition metal oxide falls within the above range, the obtained positive electrode active material can more easily satisfy the physical properties of Equation 1 and other such formulas described above.

[0099] The aforementioned secondary crushing can be carried out at a crushing pressure of 3.5 to 4.5 bar, and more specifically, at a crushing pressure of 3.5 to 3.9 bar. When the crushing pressure during secondary crushing is within the above range, as secondary crushing is carried out with appropriate force, the resulting positive electrode active material, with its small particle size, i.e., the fine powder ratio, can be appropriately controlled, and the obtained material can satisfy the physical properties of Equation 1 and other formulas described above.

[0100] The aforementioned series of manufacturing methods can form a single-particle lithium transition metal oxide according to the present invention, and the obtained lithium transition metal oxide can satisfy physical properties such as those shown in Formula 1. This makes it possible to improve the electrode energy density and improve the capacity and high-temperature life characteristics of the battery.

[0101] 3. Positive electrode and lithium secondary battery Yet another embodiment of the present invention provides a positive electrode for a lithium secondary battery containing the positive electrode active material described above.

[0102] More specifically, the positive electrode may include a positive electrode current collector and a positive electrode active material layer disposed on the positive electrode current collector and containing the positive electrode active material described above.

[0103] The positive electrode current collector is not particularly limited as long as it does not induce 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, and nonwoven fabric.

[0104] The positive electrode active material layer may include a binder and / or conductive material together with the positive electrode active material described above.

[0105] At this time, 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, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer rubber (EPDM rubber), sulfonated EPDM, styrene-butadiene rubber (SBR), fluororubber, or various copolymers thereof, and one or more of these can be used, but are not limited to these. The binder is contained in an amount of 1 to 30% by weight relative to the total weight of the positive electrode active material layer.

[0106] 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 is usually included in an amount of 1 to 30% by weight relative to the total weight of the positive electrode active material layer.

[0107] The positive electrode can be manufactured by a conventional positive electrode manufacturing method, except that the positive electrode active material is used.

[0108] 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 optionally a binder, conductive material, or solvent, onto 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 material are as described above.

[0109] The solvent is a solvent commonly used in the art, and includes dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, or water. One of these can be used alone or a mixture of two or more. The amount of solvent used is 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 uniformity of thickness during subsequent coating for cathode manufacturing.

[0110] 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.

[0111] Yet another embodiment of the present invention provides a lithium secondary battery including the positive electrode for a lithium secondary battery described above.

[0112] The lithium secondary battery may more specifically include a positive electrode; a negative electrode; a separator; and an electrolyte.

[0113] The lithium secondary battery may optionally further include a battery container housing the electrode assembly comprising the positive electrode, negative electrode, and separator, and a sealing member for sealing the battery container.

[0114] The negative electrode may include a negative electrode current collector and a negative electrode active material layer located on the negative electrode current collector.

[0115] The negative electrode current collector is not particularly limited as long as it does not induce 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.

[0116] The negative electrode active material layer may selectively include a binder and a conductive material together with the negative electrode active material. The negative electrode active material layer can also be manufactured, for example, 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.

[0117] 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 capable of doping and dedoping 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 mixtures can be used. Furthermore, a metallic lithium thin film can also be used as the negative electrode active material. In addition, both low-crystalline carbon and high-crystalline carbon can be used as the carbon material. 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 or coal tar pitch-derived cokes.

[0118] The binder and conductive material are the same as those described earlier for the positive electrode.

[0119] The separator separates the negative and positive electrodes and provides a passage for lithium ions to move. Any separator commonly used in lithium secondary batteries can be used without particular limitations, but those with low resistance to electrolyte ion movement and excellent electrolyte moisture absorption capacity are particularly preferred. 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 made from high-melting-point glass fibers or polyethylene terephthalate fibers, can be used. Furthermore, coated separators containing ceramic components or polymeric substances can be used to ensure heat resistance or mechanical strength, and can be selectively used in single-layer or multi-layer structures.

[0120] The electrolytes mentioned above 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.

[0121] Specifically, the organic liquid electrolyte may contain an organic solvent and a lithium salt.

[0122] The organic solvent can be any solvent that can act as a medium through which ions involved in the electrochemical reaction of the battery can move, without any particular limitations. Specifically, the organic solvents 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; dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (MEC), and ethyl methyl carbonate (ethylmethyl Carbonate solvents such as carbonate (EMC), ethylene carbonate (EC), and propylene carbonate (PC); alcoholic solvents such as ethyl alcohol and isopropyl alcohol; nitriles such as R-CN (where R is a linear, branched, or cyclic hydrocarbon group of C2-C20, which may include a double-bonded aromatic ring or ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; or sulfolanes can be used. Among these, carbonate 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 that 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 more preferred. In this case, mixing cyclic carbonates and linear carbonates in a volume ratio of approximately 1:1 to 1:9 allows the electrolyte to perform optimally.

[0123] The lithium salt can be any compound capable of providing lithium ions for use in lithium secondary batteries, without any particular 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 concentration of the lithium salt is preferably within the range of 0.1 to 2.0 M. When the concentration of the lithium salt falls within this range, the electrolyte has appropriate conductivity and viscosity, exhibiting excellent electrolyte performance and allowing lithium ions to move effectively.

[0124] 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 is present in an amount of 0.1 to 5% by weight relative to the total weight of the electrolyte.

[0125] As described above, the lithium secondary battery containing the positive electrode active material according to the present invention exhibits excellent discharge capacity, output characteristics, and capacity retention rate stably, making it useful in portable devices such as mobile phones, laptop computers, and digital cameras, as well as in the electric vehicle field, such as hybrid electric vehicles (HEVs).

[0126] Thus, yet another embodiment of the present invention provides a battery module and a battery pack including the lithium secondary battery as a unit cell.

[0127] 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]

[0128] The following examples illustrate the realization of the present invention in more detail.

[0129] However, the following embodiments are merely preferred embodiments of the present invention, and the present invention is not limited to the following embodiments.

[0130] Example 1 (1) Manufacture of positive electrode active material (Mixed)Ni 0.6 Co 0.1 Mn 0.3 A (OH)2 composition precursor and LiOH·H2O were added to a mixer and mechanically mixed so that the molar ratio of lithium to the transition metal in the precursor (Li / M) was 1.07 to form a mixture.

[0131] (Primary calcination) The mixture was then heated to 940°C in an air atmosphere, followed by primary calcination at a constant temperature of 940°C for 4 hours, and then allowed to cool naturally. After that, the primary calcined material was crushed using a rotor mill.

[0132] (Secondary calcination) The crushed primary calcined material was then subjected to secondary calcination at a constant temperature of 940°C for 10 hours in an oxygen atmosphere with an oxygen partial pressure of 99%, and then allowed to cool naturally to form lithium transition metal oxide.

[0133] (Primary crushing) The lithium transition metal oxide was then subjected to primary crushing using a rotor mill at a stirring speed of 17,000 rpm.

[0134] (Secondary crushing) Subsequently, secondary crushing was performed using a jet mill at a grinding pressure of 3.7 bar to form single-particle lithium transition metal oxide.

[0135] The final composition of the obtained lithium transition metal oxide is Li 1.07 Ni 0.6 Co 0.1 Mn 0.3 It was O2.

[0136] (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, denka black), and binder (PVDF, KF9700) in a ratio of 95.0:2.0:3.0 wt%, and adjusting the viscosity by adding NMP (N-Methyl-2-pyrrolidone) so that the solid content was approximately 60%. The manufactured slurry was coated onto 20 μm thick aluminum foil using a Doctor blade, and then dried and rolled. The electrode loading amount was 16.0 mg / cm². 2 The rolling density (25°C, 20kN) is 3.5g / cm³. 3 That was the case.

[0137] The electrolyte used was 1M LiPF6in EC:DMC:DEC=1:2:1 (vol%) with 2.0 vol% VC added relative to the total electrolyte volume. Coin cells were manufactured using a PP separation membrane and a lithium anode (400 μm, Niba metal).

[0138] Example 2 The positive electrode active material and lithium secondary battery were manufactured in the same manner as in Example 1, except that the secondary firing step was performed for 11 hours.

[0139] Comparative Example 1 The cathode active material and lithium secondary battery were manufactured in the same manner as in Example 1, except that in the secondary calcination step, secondary calcination was performed in an air atmosphere with an oxygen partial pressure of 21%, followed by secondary crushing using a jet mill at a grinding pressure of 4.1 bar.

[0140] Comparative Example 2 The cathode active material and lithium secondary battery were manufactured in the same manner as in Example 1, except that in the secondary calcination step, secondary calcination was performed for 9 hours in an air atmosphere with an oxygen partial pressure of 21%, followed by secondary crushing using a jet mill at a grinding pressure of 4.1 bar.

[0141] Comparative Example 3 The cathode active material and lithium secondary battery were manufactured in the same manner as in Example 1, except that in the secondary firing step, secondary firing was performed for 8 hours in an air atmosphere with an oxygen partial pressure of 21%, followed by secondary crushing using a jet mill at a grinding pressure of 4.0 bar.

[0142] Experimental Example 1: SEM image of cathode active material SEM images of the positive electrode active materials produced in Example 1 and Comparative Example 1 were observed and are shown in Figures 1 and 2, respectively.

[0143] Referring to Figures 1 and 2, it was confirmed that the positive electrode active materials of the examples and comparative examples had a single-particle morphology.

[0144] Experimental Example 2: Evaluation of the physical properties of the positive electrode active material The properties of the positive electrode active materials of the examples and comparative examples were evaluated by catabolism, and these are shown in Table 2.

[0145] (1) Dv50 and Dn50, Dv50 / Dn50, Dv50-Dn50 evaluation Using the laser diffraction method, the volume-based average particle size (Dv50) was determined by measuring the particle size corresponding to 50% of the cumulative volume, and the number-based average particle size (Dn50) was determined by measuring the particle size corresponding to 50% of the cumulative number. Subsequently, Dv50 / Dn50 and Dv50-Dn50 were calculated using these values.

[0146] (2) Grain size, a-axis lattice constant (La), c-axis lattice constant (Lc), Lc / La evaluation Using Bruker's D8 Discover with GADDS XRD equipment, we measured the XRD data of the active material. Using the Reitveld refinement method built into Bruker's DIFFRAC.TOPAS program, we determined the crystal size, a-axis lattice constant (La), and c-axis lattice constant (Lc). We then calculated Lc / La by dividing the c-axis lattice constant (Lc) by the a-axis lattice constant (La).

[0147] [Table 1]

[0148] [Table 2]

[0149] [Table 3]

[0150] Referring to Tables 1 to 3, in Examples 1 and 2, where the active material manufacturing process conditions were appropriately controlled, such as performing secondary calcination in an oxygen atmosphere and secondary crushing, it was confirmed that Dv50 / Dn50, Dv50-Dn50, and other XRD properties were appropriately obtained within the range of the present invention. On the other hand, in Comparative Examples 1 to 3, where calcination was performed in an air atmosphere during secondary calcination, it was confirmed that Dv50 / Dn50, Dv50-Dn50, and other XRD properties exceeded the range of the present invention.

[0151] Experimental Example 3: Evaluation of Electrochemical Properties of Lithium Secondary Batteries The electrochemical properties of the lithium secondary batteries of the examples and comparative examples were evaluated using the following method and are shown in Table 4.

[0152] (1) Initial capacity and initial efficiency evaluation After fabricating lithium secondary battery half-cells, aging was performed at 25°C for 12 hours, followed by charge-discharge tests at 25°C. For initial capacity evaluation, 200mAh / g was used as the reference capacity. The cells were charged to 4.4V with a constant current of 0.1C, 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 0.1C with a reference capacity of 200mAh / g until the voltage reached 2.5V.

[0153] (2) Evaluation of high-temperature life characteristics (high-temperature capacity retention rate) (45°C, 50 cycles) After fabricating the lithium secondary battery half-cell, it was charged at 45°C with a constant current of 0.5C to 4.4V, then switched to a constant voltage and charged until the termination current reached 0.05C. After charging, there was a 10-minute rest time, followed by discharge at a constant current of 1.0C until it reached 2.5V. Fifty charge-discharge cycles were performed under these conditions, and the capacity retention rate at the 50th cycle relative to the first cycle was calculated.

[0154] (3) Evaluation of the rate of increase in high temperature resistance (45°C, 50 cycles) After fabricating the lithium secondary battery half-cell, it was charged at 45°C with a constant current of 0.5C to 4.4V, then switched to a constant voltage and charged until the termination current reached 0.05C. After charging, there was a 10-minute rest time, followed by discharge at a constant current of 1.0C until it reached 2.5V. This charge-discharge cycle was performed 50 times, and the resistance increase rate from the first cycle to the 50th cycle was calculated.

[0155] [Table 4]

[0156] Referring to Table 4, it was confirmed that in Examples 1 and 2, where the physical properties of the positive electrode active material, such as those in Formula 1, satisfy the range of the present invention, the initial charge capacity, discharge capacity, initial efficiency, high-temperature life characteristics, and high-temperature resistance characteristics are all excellent. On the other hand, in Comparative Examples 1 to 3, where the physical properties of the positive electrode active material, such as those in Formula 1, exceed the range of the present invention, it was confirmed that the initial charge capacity, discharge capacity, initial efficiency, high-temperature life characteristics, and high-temperature resistance characteristics are lower compared to the Examples.

[0157] Although preferred embodiments of the present invention have been described above, the present invention is not limited thereto, and can be implemented in various ways 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.

[0158] Therefore, the substantial scope of the present invention can be defined by the attached claims and their equivalents.

Claims

1. It contains a lithium transition metal oxide in single-particle form containing 50 to 70 mol% nickel based on the total moles of the transition metal, Positive electrode active material for lithium secondary batteries that satisfies the following formula 1: [Formula 1] Dv50 / Dn50≧3.0 In the above formula 1, Dv50 is the volume-based average particle size of the positive electrode active material, and Dn50 is the number-based average particle size of the positive electrode active material.

2. The positive electrode active material for a lithium secondary battery according to claim 1 that satisfies the following formula 2: [Formula 2] Dv50-Dn50≧2.5nm In the above formula 2, Dv50 is the volume-based average particle size of the positive electrode active material, and Dn50 is the number-based average particle size of the positive electrode active material.

3. The positive electrode active material for a lithium secondary battery according to claim 1, wherein the volume-based average particle size (Dv50) of the lithium transition metal oxide is 3.5 to 4.5 μm.

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

5. The positive electrode active material for a lithium secondary battery according to claim 1, wherein the crystal grain size of the lithium transition metal oxide is 190 nm or less.

6. The positive electrode active material for a lithium secondary battery according to claim 1, wherein the ratio of the c-axis lattice constant to the a-axis lattice constant (Lc / La) of the lithium transition metal oxide is 4.955 or more.

7. The positive electrode active material for a lithium secondary battery according to claim 1, wherein the c-axis lattice constant (Lc) of the lithium transition metal oxide is 14.2472 nm or greater.

8. The positive electrode active material for a lithium secondary battery according to claim 1, wherein the a-axis lattice constant (La) of the lithium transition metal oxide is 2.8752 nm or less.

9. The lithium transition metal oxide is the positive electrode active material for a lithium secondary battery according to claim 1, represented by the chemical formula 1: [Chemical formula 1] Li ａ [Ni ｘ Co ｙ Mn ｚ M ｗ ]O ２ In the above chemical formula 1, 0.8 ≤ a ≤ 1.2, 0.5 ≤ x ≤ 0.7, 0 ≤ y ≤ 0.2, 0 ≤ z ≤ 0.4, 0 ≤ w ≤ 0.2, x + y + z + w = ​​1, and M is Zr, Al, B, Y, Mg, Ti, Nb, W, Sc, Si, V, Fe, Y, Mo, Ce, Hf, Ta, La, Sr, or a combination thereof.

10. A step of preparing a transition metal precursor containing 50-70 mol% nickel based on the total moles of the transition metal; The steps of mixing the transition metal precursor and lithium raw material, then performing primary and secondary calcination to form a lithium transition metal oxide; and The step includes primary and secondary decomposition of the lithium transition metal oxide to form a lithium transition metal oxide in single-particle form, The aforementioned secondary firing involves oxygen (O ２ ) It is done in a certain atmosphere. A method for producing positive electrode active material for lithium secondary batteries.

11. The method for producing a positive electrode active material for a lithium secondary battery according to claim 10, wherein the secondary crushing is performed such that the volume-based average particle size (Dv50) of the lithium transition metal oxide is 3.5 to 4.5 μm.

12. The method for producing a positive electrode active material for a lithium secondary battery according to claim 10, wherein the primary crushing is performed at a stirring speed of 15,000 to 20,000 rpm.

13. The method for producing a positive electrode active material for a lithium secondary battery according to claim 10, wherein the secondary crushing is performed at a crushing pressure of 3.5 to 4.5 bar.

14. The method for producing a positive electrode active material for a lithium secondary battery according to claim 10, wherein the primary firing is carried out in an air atmosphere.

15. The method for producing a positive electrode active material for a lithium secondary battery according to claim 10, wherein the primary firing and the secondary firing are each carried out independently at a temperature of 900 to 960°C.

16. A positive electrode for a lithium secondary battery comprising the positive electrode active material described in any one of claims 1 to 9.

17. A lithium secondary battery comprising a positive electrode for a lithium secondary battery as described in claim 16.

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