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, comprising a single-particle type lithium metal oxide containing 50 to 70 mol% nickel based on the total number of moles of metal excluding lithium, and satisfying the following formulas 1 and 2. [Formula 1] 3.0 μm ≤ Dv50 ≤ 5.0 μm [Formula 2] Dv50-Dn50 ≤ 2.0 μm In equations 1 and 2 above, Dv50 is the volume-based average particle size of the lithium metal oxide, and Dn50 is the number-based average particle size of the lithium metal oxide.

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, electrical energy is produced by oxidation and reduction reactions that occur when lithium ions are inserted into / deintercalated from the positive and negative electrodes, with an organic or polymer electrolyte filling the space between the positive and negative electrodes, which are made of an active material that allows for the insertion and deintercalation of lithium ions.

[0003] Lithium-ion rechargeable batteries have used lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), lithium manganese oxide (LiMnO2 or LiMn2O4, etc.), and lithium phosphate compounds (LiFePO4) as positive electrode active materials. Among these, lithium cobalt oxide (LiCoO2) has the advantages 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 rising cobalt (Co) prices and unstable supply, 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 is emerging.

[0004] To this end, nickel-cobalt-manganese lithium composite transition metal oxides (hereinafter simply referred to as "NCM-based lithium composite transition metal oxides") were developed in which some of the cobalt (Co) is replaced with nickel (Ni) and manganese (Mn).

[0005] 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, a large contact area with the electrolyte, increased gas generation, and weak particle strength, which can lead to particle cracking during the electrode rolling process. Consequently, there have been problems with the deterioration of battery safety and lifespan characteristics.

[0006] Therefore, development is underway on single-particle positive electrode active materials, rather than the conventional secondary particle form. Single-particle positive electrode active materials can solve many of the problems associated with secondary particles and improve the safety and lifespan characteristics of batteries. However, even with the same single-particle positive electrode active material, if the firing and crushing process conditions are not properly controlled, the particle strength may deteriorate, and the aforementioned battery performance improvement effect may become minimal. [Overview of the project] [Problems that the invention aims to solve]

[0007] In contrast, one objective of the present invention is to provide a lithium metal oxide in single-particle form with improved particle strength, a positive electrode active material for lithium secondary batteries that can maximize the safety and lifespan characteristics of the battery, a method for producing the same, and a lithium secondary battery containing the same. [Means for solving the problem]

[0008] One embodiment of the present invention provides a positive electrode active material for a lithium secondary battery that contains a lithium metal oxide in single-particle form containing 50 to 70 mol% nickel based on the total number of moles of metal excluding lithium, and satisfies the following formulas 1 and 2.

[0009] [Formula 1] 3.0 μm ≤ Dv50 ≤ 5.0 μm

[0010] [Formula 2] Dv50-Dn50 ≤ 2.0 μm

[0011] In the above formulas 1 and 2, Dv50 is the volume-based average particle size of the lithium metal oxide, and Dn50 is the number-based average particle size of the lithium metal oxide.

[0012] The positive electrode active material for the lithium secondary battery can satisfy the following formula 3.

[0013] [Formula 3] Dv50 / Dn50 ≦ 2.0

[0014] In the above formula 3, Dv50 is the volume-based average particle size of the lithium metal oxide, and Dn50 is the number-based average particle size of the lithium metal oxide.

[0015] The Dn50 may be 2.0 to 3.0 μm.

[0016] The Dn10 of the lithium metal oxide may be 1.0 μm or more (however, Dn10 is the particle size corresponding to 10% of the cumulative number of lithium metal oxide particles).

[0017] The lithium metal oxide may be in a single particle form.

[0018] The lithium metal oxide may have an average crystallite size of 255 nm or more.

[0019] The lithium metal oxide may have an a-axis lattice constant of 2.8751 Å or more.

[0020] When the lithium metal oxide is pressurized at a pressure of 1.7 tonf / cm 2 , the ratio of fine powder with a particle size of 1 μm or less may be 3.0% or less.

[0021] The lithium metal oxide may be represented by the following chemical formula 1.

[0022] [Chemical Formula 1] Li a [Ni x Coy Mn z M w ]O2

[0023] 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, Sn, Sb, Zn, Cu, Ge, Mo, Ru, Ir, or a combination thereof.

[0024] 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 metal precursor containing 50 to 70 mol% nickel based on the total number of moles of metal; mixing the metal precursor and a lithium raw material, and then performing primary and secondary calcination to form a lithium metal oxide; and crushing the lithium metal oxide to form a lithium metal oxide in single-particle form, wherein the primary and secondary calcination are performed in an air atmosphere.

[0025] The primary and secondary firings can each be carried out independently at a temperature of 900 to 960°C.

[0026] The primary firing time may be shorter than the secondary firing time.

[0027] The aforementioned primary firing time may be 2 to 6 hours.

[0028] The aforementioned secondary firing time may be 7 to 14 hours.

[0029] Another embodiment of the present invention provides a positive electrode for a lithium secondary battery containing the positive electrode active material described above.

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

[0031] A positive electrode active material for a lithium secondary battery according to one embodiment of the present invention includes a lithium metal oxide in single-particle form, and the particle strength can be maximized by appropriately controlling the volume-based average particle size and number-based average particle size of the lithium metal oxide. This makes it possible to maximize the safety and lifespan characteristics of the battery. [Brief explanation of the drawing]

[0032] [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 Example 2. [Figure 3] This is an SEM image of the cathode active material produced according to Example 3. [Figure 4] This is an SEM image of the cathode active material produced by Comparative Example 1. [Figure 5] This is an SEM image of the cathode active material produced by Comparative Example 2. [Figure 6] This is an SEM image of the cathode active material produced by Comparative Example 3. [Modes for carrying out the invention]

[0033] 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.

[0034] 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.

[0035] 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.

[0036] 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.

[0037] Also, unless otherwise specified, % means weight percent, and 1 ppm is 0.0001 weight percent.

[0038] 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.

[0039] 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.

[0040] 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. Therefore, it has the advantage of superior lifespan and safety compared to secondary particles, and can achieve a high energy density of the electrode.

[0041] On the other hand, 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. It is a concept that includes a single particle 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 by physical or chemical bonding between primary particles without any intentional aggregation or assembly process for the primary particles.

[0042] Furthermore, in this specification, "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 may consist of one crystal grain or multiple crystal grains. Also, "crystal grain" refers to a divided region within a primary particle in which the atoms form a lattice structure in a certain direction.

[0043] On the other hand, the lithium metal oxide according to one embodiment of the present invention contains 50 to 70 mol% nickel based on the total number of moles of metal excluding lithium. 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 possibility of thermal propagation issues, i.e., thermal safety issues, and the price of nickel is high, which may increase manufacturing costs. Therefore, the lithium metal oxide according to the present invention adjusts the nickel content to the above range in order to ensure appropriate capacity and thermal safety characteristics while also achieving economic efficiency.

[0044] However, if the calcination and crushing process conditions are not properly controlled, lithium metal oxide in this single-particle form can generate a considerable amount of very small fine particles. These multiple fine particles can react with the electrolyte, increasing gas generation and potentially degrading the battery's safety and lifespan.

[0045] Furthermore, the inventors have confirmed that when a large number of fine particles are present among the lithium metal oxide particles, applying a predetermined pressure to the active material while degrading the particle strength generates a large number of secondary fine particles (experimental results for this will be explained in detail in the experimental examples described later). The predetermined pressure application can correspond to the pressure applied during the electrode rolling process. Therefore, the large number of fine particles present immediately after the synthesis of the lithium metal oxide can generate a large number of secondary fine particles as pressure is applied during the rolling process for actual cathode realization. This may further accelerate the deterioration of the battery's safety and lifespan characteristics.

[0046] In response to this, the inventors of the present invention have completed the present invention as a result of extensive research on particle size distribution to maximize the particle strength of single-particle positive electrode active material. Furthermore, as described later, the particle size distribution can be obtained by precisely controlling the firing and crushing process conditions during the manufacturing of the positive electrode active material. This will be explained in more detail in the manufacturing method described later.

[0047] The positive electrode active material for a lithium secondary battery according to one embodiment of the present invention satisfies the following equation 1.

[0048] [Formula 1] 3.0 μm ≤ Dv50 ≤ 5.0 μm

[0049] More specifically, the Dv50 may be 3.5 μm or 3.8 μm or larger, or 4.5 μm or smaller.

[0050] Furthermore, the positive electrode active material for a lithium secondary battery according to one embodiment of the present invention satisfies the following formula 2.

[0051] [Formula 2] Dv50-Dn50 ≤ 2.0 μm

[0052] The Dv50-Dn50 valency may more specifically be 1.5 μm to 2.0 μm.

[0053] Furthermore, the positive electrode active material for lithium secondary batteries according to the present invention can satisfy the following formula 3.

[0054] [Formula 3] Dv50 / Dn50 ≤ 2.0

[0055] In Equation 3 above, Dv50 is the volume-based average particle size of the lithium metal oxide, and Dn50 is the number-based average particle size of the lithium metal oxide.

[0056] The aforementioned Dv50 / Dn50 price may more specifically be 1.6 to 2.0.

[0057] In equations 1 to 3 above, Dv50 is the volume-based average particle size of the lithium metal oxide, and Dn50 is the number-based average particle size of the lithium 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.

[0058] The positive electrode active material for lithium secondary batteries according to the present invention satisfies the above formula 1, thereby enabling the simultaneous and desirable realization of electrochemical characteristics such as high electrode density, capacity, and output. More specifically, if Dv50 is too small, the density of the positive electrode active material may become too small, potentially reducing the electrode density and consequently lowering the electrode energy density. If Dv50 is too large, lithium ion mobility may decrease, potentially reducing capacity and output characteristics. Therefore, when the positive electrode active material satisfies formula 1, the electrode density and capacity characteristics can be appropriately improved simultaneously, enabling the realization of high electrode energy density.

[0059] The positive electrode active material for lithium secondary batteries according to the present invention can maximize the battery's safety and lifespan characteristics by satisfying Equation 2 or Equation 3. The difference between Dv50 and Dn50, or the Dv50 / Dn50 value, can be used as a substitute for the proportion of fine particles within the lithium metal oxide particles. More specifically, generally, the Dv50 value can represent a value greater than the Dn50 value. In this case, the closer the Dn50 value is to the Dv50 value, the lower the proportion of fine particles becomes. Therefore, when the positive electrode active material satisfies Equation 2 or Equation 3, the proportion of fine particles decreases, and for the same reasons as described above, the battery's safety and lifespan characteristics can be improved.

[0060] More specifically, Dn50 may be 2.0 to 3.0 μm, and more specifically, 2.0 to 2.51 μm.

[0061] On the other hand, the Dn10 of the lithium metal oxide may be 1.0 μm or larger, and more specifically, 1.0 to 1.435 μm. A sufficiently large Dn10 value of the lithium metal oxide reduces the proportion of fine particles within the lithium metal oxide particles, and for the same reasons as described above, the safety and lifespan characteristics of the battery can be improved.

[0062] The aforementioned Dn10 can be defined as the particle size corresponding to 10% of the cumulative number of particles in the particle size distribution curve. The particle number reference particle size Dn10 can be measured, for example, using the laser diffraction method.

[0063] Furthermore, the lithium metal oxide may be in single-particle form. In this specification, "single particle" means a single particle consisting of only one primary particle. Also, in this specification, "single-particle form" of lithium metal oxide means that the proportion of single particles consisting of only one primary particle among a plurality of lithium metal oxide particles is 90% or more. When the lithium metal oxide is in single-particle form, the particle strength is further improved, and the aforementioned effects of improving the safety and lifespan characteristics of the battery can be more desirablely realized.

[0064] Furthermore, the lithium metal oxide may have an average crystallite size of 255 nm or more, and more specifically, 260 nm or more. Such a sufficiently large average crystallite size of the lithium metal oxide further improves particle strength, allowing for a more desirable realization of the aforementioned improvements in battery safety and lifespan. In this specification, the "average crystallite size" can be measured using peak loading of XRD data and quantitatively calculated by Scherrer quantification. Moreover, the average crystallite size of the lithium metal oxide can be easily obtained by precisely controlling the firing process conditions during the production of the positive electrode active material.

[0065] Furthermore, the lithium metal oxide may have an a-axis lattice constant of 2.8751 Å or greater. The a-axis lattice of the lithium metal oxide can increase as the average crystal grain size of the lithium metal oxide increases, and such a sufficiently large a-axis lattice constant further improves particle strength, thereby more desirablely realizing the aforementioned effects of improving battery safety and lifespan characteristics. On the other hand, in this specification, the "a-axis lattice constant" can be measured using peak loading of XRD data and can be quantitatively calculated by Scherrer quantification. Moreover, the a-axis lattice constant of the lithium metal oxide can also be easily obtained by precisely controlling the firing process conditions during the production of the positive electrode active material.

[0066] Therefore, the lithium metal oxide silver particle strength according to the present invention is maximized to 1.7 tonf / cm². 2 The proportion of fine powder with a particle size of 1 μm or less when pressurized at the specified pressure may be 3.0% or less.

[0067] The aforementioned physical properties can be measured more specifically by the following method: After placing a 3.00 g sample of positive electrode active material into a mold with a diameter of 1.3 cm, measure the pressure at 1.7 tonf / cm². 2Pressurize with the force of . After that, put the pressurized pellet-shaped positive electrode active material into the induction and pulverize it to crush the massive particles. After that, after adding 0.01 g of the positive electrode active material to 10 wt% (NaPO3)6 1 mL as a dispersant, perform ultrasonic treatment for 1 minute. After that, perform particle size analysis using a Malvern (MS3000) device, measure the volume percentage of fine powder with a particle size of 1 μm or less, and the fine powder ratio can be measured.

[0068] The lithium metal oxide may be more specifically represented by the following Chemical Formula 1.

[0069] [Chemical Formula 1] Li a [Ni x Co y Mn z M w O2

[0070] 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, Sn, Sb, Zn, Cu, Ge, Mo, Ru, Ir, or a combination thereof.

[0071] In the lithium transition metal oxide of Chemical Formula 1, 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 pulverization may become difficult, and the gas generation amount 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 be more preferably contained in a content of 0.9 ≤ a ≤ 1.1.

[0072] In the lithium transition metal oxide of chemical formula 1, nickel may be 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 battery life and thermal safety will decrease due to a decrease in the structural stability of the active material, and manufacturing costs may increase.

[0073] In the lithium transition metal oxide of chemical formula 1, cobalt may be 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 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 or 0.1 ≤ 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 power characteristics of the battery may decrease.

[0075] In the lithium transition metal oxide of chemical formula 1, M may be present in an amount corresponding to w, i.e., 0 ≤ w ≤ 0.2. In this case, M may be a doping element such as Zr, Al, B, Y, Mg, Ti, Nb, W, Sc, Si, V, Fe, Y, Mo, Ce, Hf, Ta, La, Sr, or a combination thereof.

[0076] 2. Method for manufacturing positive electrode active material The particle size-related properties of the positive electrode active material for lithium secondary batteries according to one embodiment of the present invention, including the Dv50-Dn50 value, can be obtained by precisely controlling the firing and crushing process conditions. The method for manufacturing the positive electrode active material will be described below.

[0077] 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 metal precursor containing 50 to 70 mol% nickel based on the total number of moles of metal; mixing the metal precursor and a lithium raw material, and then performing primary and secondary calcination to form a lithium metal oxide; and crushing the lithium metal oxide to form a lithium metal oxide in single-particle form, wherein the primary and secondary calcination are performed in an air atmosphere.

[0078] The following describes in detail, 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 metal precursor containing 50-70 mol% nickel based on the total number of moles of the metal.

[0080] The metal precursor may be, for example, a metal hydroxide.

[0081] The aforementioned metal hydroxide can 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.

[0082] The nickel raw material is not particularly limited as long as it is used in the production of cathode active material precursors in the industry. For example, the nickel raw material is a nickel-containing sulfate, acetate, nitrate, halogen compound, sulfide, hydroxide, oxide or oxyhydroxide, and may specifically be, but not limited to, NiSO4, NiSO4·6H2O, Ni(OH)2, NiO, NiOOH, NiCO3·2Ni(OH)2·4H2O, NiC2O2·2H2O, Ni(NO32)·6H2O, fatty acid nickel salt, nickel halide, or a combination thereof.

[0083] The aforementioned cobalt raw material is not particularly limited as long as it is used in the production of cathode active material precursors in this industry. For example, the aforementioned cobalt raw material may be cobalt-containing sulfates, acetates, nitrates, halogen compounds, sulfides, hydroxides, oxides, or oxyhydroxides, and may specifically be, but not limited to, CoSO4, CoSO4·7H2O, Co(OH)2, CoOOH, Co(OCOCH3)2·4H2O, Co(NO3)2·6H2O, or combinations thereof.

[0084] 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 may be manganese-containing sulfates, acetates, nitrates, halogen compounds, sulfides, hydroxides, oxides, oxyhydroxides, or combinations thereof, and may, but is not limited to, manganese salts such as MnSO4, MnCO3, Mn(NO3)2, manganese acetate, manganese dicarboxylate salts, manganese citrate and manganese fatty acid salts, manganese oxides such as Mn2O3, MnO2, and Mn3O4, oxyhydroxides, manganese chloride, or combinations thereof.

[0085] 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 an organic solvent (e.g., alcohol) that can be homogeneously mixed with water, and a mixture of water.

[0086] The complexing agent-containing solution plays a role in complex formation, and the complexing agent may include, but is not limited to, NH3, NH4OH, (NH4)2SO4, NH4NO3, NH4Cl, CH3COONH4, NH4CO3, or combinations thereof. 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.

[0087] The pH adjusting agent-containing solution may serve as a precipitating agent 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 be used in the form of an aqueous solution, 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.

[0088] 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.

[0089] Through this process, 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 be secondary particles formed by the aggregation of primary particles.

[0090] At this time, the concentrations of nickel, cobalt, and manganese raw materials can be adjusted to control the molar ratio of nickel, cobalt, and manganese in the precursor.

[0091] Therefore, the nickel-resistant content of the metal precursor may be 50 to 70 mol% based on the total number of moles of metal. The technical significance of adjusting the nickel-resistant content of the metal precursor is as described above and will therefore be omitted.

[0092] Next, the metal precursor and lithium raw material are mixed, and then primary and secondary calcination are performed to form lithium metal oxide.

[0093] Conventionally, the formation of lithium transition metal oxides in single-particle form was carried out by only a primary calcination at high temperature for a long time. However, in this case, there was a problem in that the electrochemical properties of the active material deteriorated due to the nickel cation mixing phenomenon and the generation of a Rocksalt impurity phase caused by overcalcination. On the other hand, the manufacturing method according to the present invention can prevent the above problems by performing the calcination in two stages, can improve the particle strength of the active material, and can increase the production volume.

[0094] At this time, both the primary and secondary firings are carried out in an air atmosphere. Compared to when the firing atmosphere is an oxygen (O2) atmosphere, when it is carried out in an air atmosphere, the amount of fine particles decreases, the Dn50 value increases, and particle size-related physical properties, including the Dv50-Dn50 value, can be appropriately obtained within the scope of the present invention, thereby improving particle strength. The inventors believe this is because when the cathode material is fired, individual particles may aggregate and grow, or only the crystallinity of individual particles may increase, and therefore the particle growth mechanism may change during firing depending on the CO2 and O2 fractions in the atmosphere.

[0095] The aforementioned air atmosphere may more specifically be an air atmosphere in which the partial pressure of oxygen is 21% or less.

[0096] Furthermore, the primary and secondary firings can each be carried out independently at temperatures of 900-960°C. If the firing temperature is too low, single-particle lithium metal oxide may not form easily, and as the amount of fine particles increases, the Dn50 value may become too small, potentially degrading the particle strength. If the firing temperature is too high, over-firing may cause a decrease in electrochemical properties such as capacity and output, and the grinding pressure (Jet-Mill) may become too large, potentially leading to an increase in fine particles and a decrease in the Dn50 value, thus degrading the particle strength.

[0097] Furthermore, the primary firing time may be shorter than the secondary firing time. When the primary firing time is shorter than the secondary firing time, the amount of fine particles decreases, the Dn50 value increases, and particle size-related physical properties, including the Dv50-Dn50 value, can be appropriately obtained within the scope of the present invention, thereby improving particle strength.

[0098] The aforementioned primary firing time may more specifically be 2 to 6 hours. If the primary firing time is too short, the Dn50 value may become too small as the amount of fine particles increases, potentially degrading the particle strength. If the primary firing time is too long, two Jet-Mill crushing processes are required, and as a result, the amount of fine particles increases, potentially degrading the particle strength by making the Dn50 value too small.

[0099] The aforementioned secondary firing time may more specifically be 7 to 14 hours. If the secondary firing time is too short, the Dn50 value may become too small due to an increase in ungrown particles, potentially degrading the particle strength. If the secondary firing time is too long, the Dn50 value may become too small due to an increase in Jet-Mill pressure for crushing overfired particles, potentially degrading the particle strength.

[0100] Next, the lithium metal oxide is crushed to form lithium metal oxide in single-particle form.

[0101] The above decomposition can be carried out in two stages: primary decomposition and secondary decomposition. By dividing the decomposition into primary and secondary decomposition, aggregated secondary particles can be efficiently broken down into single-particle forms.

[0102] The aforementioned primary crushing can be carried out using crushing equipment commonly used in this industry. For example, the primary crushing is carried out using a rotor mill, but is not necessarily limited to this.

[0103] 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 satisfies the above range, the fine particles are appropriately reduced as the primary crushing is carried out with appropriate force, and various physical properties such as the Dn50 and Dv50-Dn50 values ​​of lithium metal oxide can be appropriately realized within the scope of the present invention.

[0104] 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.

[0105] 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 3.0 to 5.0 μm. By adjusting the secondary crushing so that the volume-based average particle size (Dv50) of the lithium transition metal oxide falls within the above range, various physical properties of the obtained lithium metal oxide, such as Dn50 and Dv50-Dn50 values, can be appropriately realized within the scope of the present invention.

[0106] The aforementioned secondary crushing can be carried out at a crushing pressure of 2.1 to 5.4 bar. When the crushing pressure during secondary crushing meets the above range, as secondary crushing is carried out with appropriate force, the amount of fine particles is appropriately reduced, and various physical properties such as the Dn50 and Dv50-Dn50 values ​​of the lithium metal oxide can be appropriately implemented within the scope of the present invention.

[0107] Through the series of manufacturing methods described above, a single-particle lithium metal oxide according to the present invention may be formed, and the obtained lithium metal oxide can satisfy the scope of the present invention in terms of various physical properties, such as the Dv50-Dn50 value.

[0108] 3. Positive electrode and lithium secondary battery Another embodiment of the present invention provides a positive electrode for a lithium secondary battery containing the positive electrode active material described above.

[0109] 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, which includes the positive electrode active material described above.

[0110] 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.

[0111] The positive electrode active material layer may include a binder and / or conductive material together with the positive electrode active material described above.

[0112] 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, 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 or more of these can be used, but are not limited to these. The binder may be included in an amount of 1 to 30% by weight relative to the total weight of the positive electrode active material layer.

[0113] 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 included in an amount of 1 to 30% by weight relative to the total weight of the positive electrode active material layer.

[0114] The positive electrode can be manufactured by a conventional positive electrode manufacturing method, except that the positive electrode active material is used.

[0115] 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.

[0116] 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 such that, considering the coating thickness of the slurry and the production yield, it is sufficient to have a viscosity that dissolves or disperses the positive electrode active material, conductive material, and binder, and subsequently exhibits excellent thickness uniformity when coated for positive electrode production.

[0117] Alternatively, the positive electrode can also be manufactured by casting the positive electrode active material layer forming composition onto another support, peeling it off the support, and then laminating the resulting film onto the positive electrode current collector.

[0118] Another embodiment of the present invention provides a lithium secondary battery including the positive electrode for lithium secondary batteries described above.

[0119] The lithium secondary battery may more specifically include a positive electrode; a negative electrode; a separator; and an electrolyte.

[0120] The lithium secondary battery may optionally further include a battery container for housing the electrode assembly comprising the positive electrode, negative electrode, and separator, and a sealing member for sealing the battery container.

[0121] The negative electrode may include a negative electrode current collector and a negative electrode active material layer located on the negative electrode current collector.

[0122] 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 like 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.

[0123] The negative electrode active material layer may selectively contain 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 another support, peeling it off the support, and laminating the resulting film onto the negative electrode current collector.

[0124] 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 can be used in mixtures. 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 or coal tar pitch-derived cokes.

[0125] The binder and conductive material may be the same as those described earlier for the positive electrode.

[0126] The separator, which separates the negative and positive electrodes and provides a pathway for lithium ions to move, can be used without special restrictions as long as it is the type normally used as a separator in lithium secondary batteries. In particular, it is desirable that it has low resistance to ion movement of the electrolyte while having excellent electrolyte moisture absorption capacity. Specifically, porous polymer films, such as porous polymer films made from polyolefin polymers such as 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 nonwoven fabrics composed of high-melting-point glass fibers or polyethylene terephthalate fibers, can also 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.

[0127] 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.

[0128] Specifically, the organic liquid electrolyte may contain an organic solvent and a lithium salt.

[0129] The aforementioned 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 aforementioned 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; and dimethyl carbonate (DMC) and diethyl carbonate (DE). C) Carbonate solvents such as methylethyl carbonate (MEC), ethyl methyl 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-based solvents are preferred, and a mixture of a cyclic carbonate (e.g., ethylene carbonate or propylene carbonate) with 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, using a mixture of cyclic carbonate and linear carbonate in a volume ratio of approximately 1:1 to approximately 1:9 can bring out the best performance of the electrolyte.

[0130] The lithium salt can be used without any special restrictions, as long as it is a compound that can provide lithium ions for use in lithium secondary batteries. 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 used 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, so it can exhibit excellent electrolyte performance and lithium ions can move effectively.

[0131] In addition to the electrolyte components, the electrolyte may further contain one or more additives for purposes such as 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 included in an amount of 0.1 to 5% by weight relative to the total weight of the electrolyte.

[0132] 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).

[0133] Therefore, yet 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.

[0134] 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]

[0135] 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.

[0136] Example 1 (1) Manufacturing of positive electrode active material (Mixed)Ni 0.6 Co 0.1 Mn 0.3 A mixture was formed by mechanically mixing a precursor with an (OH)2 composition and LiOH·H2O in a mixer such that the molar ratio (Li / M) of lithium to the transition metal in the precursor was 1.07.

[0137] (Primary calcination) After the mixture was heated to 930°C in an air atmosphere with an oxygen partial pressure of 21%, it was subjected to primary calcination at a constant temperature of 930°C for 4 hours, and then allowed to cool naturally. Subsequently, the primary calcined material was crushed using a rotor mill.

[0138] (Secondary calcination) After the above-mentioned crushed primary calcined material was subjected to secondary calcination at a constant temperature of 930°C for 12 hours in an air atmosphere with an oxygen partial pressure of 21%, and then allowed to cool naturally to form lithium metal oxide.

[0139] The aforementioned primary and secondary firings were all performed inside the Lab Box.

[0140] (Primary crushing) The lithium metal oxide was then subjected to primary crushing using a rotor mill at a stirring speed of 18,000 rpm.

[0141] (Secondary crushing) Subsequently, lithium transition metal oxides in single-particle form were formed by secondary crushing using a jet mill at a crushing pressure of 4.0 bar.

[0142] The final composition of the lithium transition metal oxide obtained is Li 1.07 Ni 0.6 Co 0.1 Mn 0.3 It was O2.

[0143] (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%, adding NMP (N-Methyl-2-pyrrolidone), and adjusting the viscosity so that the solid content was approximately 60%. The manufactured slurry was coated onto a 20 μm thick aluminum foil using a Doctor blade, and then dry-rolled. The electrode rolling amount was 16.0 mg / cm². 2 The rolling density (25°C, 20kN) is 3.5g / cm³. 3 That was the case.

[0144] 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 fabricated using a PP separation membrane and a lithium anode (400 μm, Nibametal).

[0145] Example 2 The positive electrode active material and lithium secondary battery were manufactured in the same manner as in Example 1, except that the primary firing time was set to 4 hours in the primary firing stage and the secondary firing time was set to 10 hours in the secondary firing stage.

[0146] Example 3 The positive electrode active material and lithium secondary battery were manufactured in the same manner as in Example 1, except that the primary firing time was set to 4 hours in the primary firing stage and the secondary firing time was set to 8 hours in the secondary firing stage.

[0147] Example 4 A positive electrode active material and a lithium secondary battery were manufactured in the same manner as in Example 1, except that the primary firing time was set to 4 hours in the primary firing stage and the secondary firing time was set to 10 hours in the secondary firing stage, and both the primary and secondary firings were performed in an RHK firing furnace.

[0148] Example 5 A positive electrode active material and a lithium secondary battery were manufactured in the same manner as in Example 1, except that the primary firing time was set to 4 hours in the primary firing stage and the secondary firing time was set to 9 hours in the secondary firing stage, and both the primary and secondary firings were performed in an RHK firing furnace.

[0149] Example 6 A positive electrode active material and a lithium secondary battery were manufactured in the same manner as in Example 1, except that the primary firing time was set to 4 hours in the primary firing stage and the secondary firing time was set to 8 hours in the secondary firing stage, and both the primary and secondary firings were performed in an RHK firing furnace.

[0150] 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 firing process was not divided into primary and secondary firing, but rather carried out in a single primary firing for 14 hours, and the primary firing was performed in an RHK firing furnace.

[0151] Comparative Example 2 A positive electrode active material and a lithium secondary battery were manufactured in the same manner as in Example 1, except that the primary firing time was set to 4 hours in the primary firing stage and the secondary firing time was set to 10 hours in the secondary firing stage, and both the primary and secondary firings were carried out in an oxygen (O2) atmosphere with an oxygen partial pressure of 96% or higher.

[0152] Comparative Example 3 A positive electrode active material and a lithium secondary battery were manufactured in the same manner as in Example 1, except that the primary firing time was set to 4 hours in the primary firing stage, the secondary firing time was set to 11 hours in the secondary firing stage, and both the primary and secondary firings were carried out in an oxygen (O2) atmosphere with an oxygen partial pressure of 96% or higher.

[0153] Table 1 below summarizes the process conditions for the examples and comparative examples.

[0154] [Table 1]

[0155] Experimental Example 1: Evaluation of Cathode Active Material SEM Image SEM (scanning electron microscope) images of the positive electrode active materials produced by Examples 1-3 and Comparative Examples 1-3 were observed and are shown in Figures 1-6, respectively.

[0156] Referring to Figures 1 to 6, it was confirmed that the positive electrode active materials in the examples and comparative examples were in single-particle form.

[0157] Experimental Example 2: Evaluation of the physical properties of the positive electrode active material (1) Dv50 and Dn50, Dv50 / Dn50, Dv50-Dn50, Dn10 evaluation Using the laser diffraction method, the particle size corresponding to 50% of the cumulative volume was measured to determine the volume-based average particle size (Dv50). The particle sizes corresponding to 50% and 10% of the cumulative number were then measured to determine the number-based average particle size (Dn50) and Dn10. Subsequently, Dv50 / Dn50 and Dv50-Dn50 were calculated using these values.

[0158] (2) 1.7 tonf / cm 2 Evaluation of the ratio of fine particles with a particle size of 1 μm or less when pressure is applied. After placing 3.00 g of positive electrode active material sample into a 1.3 cm diameter mold, the pressure was increased to 1.7 tonf / cm². 2 Pressurization was applied using the force of [unspecified force]. Subsequently, the pressurized pellet-shaped positive electrode active material was placed in an induction chamber and pulverized to break up any clumpy particles. Then, 0.01 g of positive electrode active material was added to 61 mL of 10 wt% (NaPO3) as a dispersant, and sonication was performed for 1 minute. After that, particle size analysis was performed using Malvern (MS3000) equipment, and the volume % of fine powder with a particle size of 1 μm or less was measured to determine the fine powder ratio.

[0159] (3) Evaluation of average grain size and a-axis lattice constant Peak broadening and scherrequation were applied to XR Ddata to evaluate the average grain size and a-axis lattice constant.

[0160] [Table 2]

[0161] Referring to Table 2, in the example where the firing and crushing process conditions were appropriately controlled, it was confirmed that the amount of fine particles decreased, the Dn50 value became sufficiently large, and various physical properties such as the Dv50-Dn50 value were appropriately obtained within the range of the present invention. Furthermore, it was confirmed that the average crystal grain size and a-axis lattice constant were large. As a result, it was confirmed that the fine particle ratio was excellent at a level of 3.0% or less when pressure was applied, and the particle strength was greatly improved. On the other hand, in Comparative Example 1, where the firing was not divided into primary and secondary firing but only primary firing was performed for a long time, it was confirmed that the Dn50 value became small, and various physical properties such as the Dv50-Dn50 value fell outside the range of the present invention. Furthermore, it was confirmed that the average crystal grain size and a-axis lattice constant were smaller compared to the example. As a result, it was confirmed that the fine particle ratio deteriorated to a level of 4.4% when pressure was applied compared to the example.

[0162] Furthermore, in Comparative Examples 2 and 3, where the primary and secondary firings were carried out in an oxygen (O2) atmosphere instead of an air atmosphere, the Dn50 value was significantly smaller, and it was confirmed that various physical properties, such as the Dv50-Dn50 value, deviated significantly from the scope of the present invention. It was also confirmed that the average crystal grain size and a-axis lattice constant were smaller compared to the examples. Consequently, it was confirmed that the fine powder ratio under pressure application was significantly lower than that of the examples, at a level exceeding 6.0%.

[0163] Experimental Example 3: Evaluation of Electrochemical Properties of Lithium-ion Secondary Batteries (1) Initial capacity and initial efficiency evaluation After fabricating lithium secondary battery half-cells, charge-discharge tests were conducted after aging at 25°C for 10 hours. For initial capacity evaluation, a reference capacity of 200mAh / g was used, and the cells were charged to 4.4V with a constant current of 0.1C. Then, the charging was switched to a constant voltage and continued until the termination current reached 0.05C. After charging, a 10-minute rest time was allowed, and then the cells were discharged to 2.5V with a constant current of 0.1C, using a reference capacity of 200mAh / g.

[0164] (2) Evaluation of the rate of increase in high-temperature resistance (45°C, 50 cycles) After fabricating a lithium secondary battery half-cell, it was charged at 45°C with a constant current of 0.2C to 4.4V, 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 with a constant current of 1.0C until it reached 2.5V. This charge-discharge cycle was performed 50 times, and the resistance increase rate after the 50th cycle was calculated compared to the first cycle.

[0165] [Table 3]

[0166] Referring to Table 3, in the example, it was confirmed that the life characteristics were significantly superior to those of the comparative example as a result of appropriately controlling various physical properties, including the Dv50-Dn50 value, within the range of the present invention. On the other hand, in the comparative example, it was confirmed that the life characteristics were significantly worse compared to the example as a result of exceeding the range of the present invention, including the Dv50-Dn50 value. This was 1.7 tonf / cm². 2 The ratio of fine powder during application is proportional to the ratio of fine powder generated during electrode pressing. By adjusting this property, it is possible to control the amount of fine powder generated during electrode fabrication, thereby improving the battery's lifespan characteristics (high-temperature resistance increase rate).

[0167] On the other hand, it was confirmed that the capacitance characteristics of the examples and comparative examples were at almost the same level. As a result, it was confirmed that in the case of the examples according to the present invention, various physical properties, including the Dv50-Dn50 values, were appropriately controlled within the range of the present invention, resulting in improved lifetime characteristics without significant degradation of capacitance characteristics.

[0168] 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.

[0169] Therefore, the substantial scope of the present invention is defined by the attached claims and their equivalents.

Claims

1. It contains a lithium metal oxide in single-particle form, which contains 50 to 70 mol% nickel based on the total number of moles of metals excluding lithium. Positive electrode active material for lithium secondary batteries that satisfies the following equations 1 and 2: [Formula 1] 3.0μm≦Dv50≦5.0μm [Formula 2] Dv50-Dn50≦2.0μm In the above formulas 1 and 2, Dv50 is the volume-based average particle size of the lithium metal oxide, and Dn50 is the number-based average particle size of the lithium metal oxide.

2. A positive electrode active material for a lithium secondary battery according to claim 1, satisfying the following formula 3: [Formula 3] Dv50 / Dn50≦2.0 In the above formula 3, Dv50 is the volume-based average particle size of the lithium metal oxide, and Dn50 is the number-based average particle size of the lithium metal oxide.

3. The positive electrode active material for a lithium secondary battery according to claim 1, wherein the Dn50 is 2.0 to 3.0 μm.

4. The positive electrode active material for a lithium secondary battery according to claim 1, wherein the Dn10 of the lithium metal oxide is 1.0 μm or larger (wherein Dn10 is a particle size corresponding to 10% of the cumulative number of lithium metal oxide particles).

5. The lithium metal oxide is in the form of a single particle, as described in claim 1, for a positive electrode active material for a lithium secondary battery.

6. The lithium metal oxide has an average crystal grain size of 255 nm or more, as described in claim 1, for a positive electrode active material for a lithium secondary battery.

7. The lithium metal oxide has an a-axis lattice constant of 2.8751 Å or more, as described in claim 1, for a positive electrode active material for a lithium secondary battery.

8. The lithium metal oxide is 1.7 tonf / cm² ２ The positive electrode active material for a lithium secondary battery according to claim 1, wherein when pressurized with the specified pressure, the proportion of fine powder with a particle size of 1 μm or less is 3.0% or less.

9. The lithium 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 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, Sn, Sb, Zn, Cu, Ge, Mo, Ru, Ir, or a combination thereof.

10. A step of preparing a metal precursor containing 50-70 mol% nickel based on the total number of moles of the metal; The steps of mixing the metal precursor and lithium raw material, then performing primary and secondary calcination to form lithium metal oxide; and The step includes crushing the lithium metal oxide to form a lithium metal oxide in single-particle form, A method for producing a positive electrode active material for a lithium secondary battery, wherein the primary and secondary firings are carried out in an air atmosphere.

11. 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.

12. The method for producing a positive electrode active material for a lithium secondary battery according to claim 10, wherein the primary firing time is shorter than the secondary firing time.

13. The method for producing a positive electrode active material for a lithium secondary battery according to claim 10, wherein the primary firing time is 2 to 6 hours.

14. The method for producing a positive electrode active material for a lithium secondary battery according to claim 10, wherein the secondary firing time is 7 to 14 hours.

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

16. A lithium secondary battery comprising a positive electrode for a lithium secondary battery as described in claim 15.

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