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

Abstract

The present invention relates to a cathode active material for a lithium secondary battery, the material comprising a discrete-particle-type lithium metal oxide, which contains 50 to 70 mol% of nickel on the basis of the total number of moles of metals excluding lithium, and satisfying equations 1 and 2. [Equation 1] 3.0 μm ≤ Dv50 ≤ 5.0 μm [Equation 2] Dv50 - Dn50 ≤ 2.0 μm In equations 1 and 2, Dv50 is a volume-based average particle diameter of the lithium metal oxide, and Dn50 is a number-based average particle diameter of the lithium metal oxide.

Description

Positive electrode active material for lithium secondary batteries, method for producing the same, and lithium secondary batteries comprising the same

[0001] The present invention relates to a positive electrode active material for a lithium secondary battery, a method for producing the same, and a lithium secondary battery comprising the same, and more specifically, to a method for producing a positive electrode active material for a lithium secondary battery in the form of a single particle, a positive electrode active material produced therefrom, and a lithium secondary battery comprising the same.

[0002]

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

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

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

[0006] However, conventionally developed NCM-based lithium composite transition metal oxides are generally formed in the form of secondary particles composed of aggregated primary particles. This results in a large surface area, which in turn increases the area in contact with the electrolyte, thus increasing gas generation. Furthermore, the particle strength is weak, which can lead to particle breakage (cracking) during the electrode rolling process. Consequently, there have been problems with the deterioration of battery safety and lifespan characteristics.

[0007] Accordingly, development is underway on single-particle cathode active materials, rather than the conventional secondary particle form. Single-particle cathode active materials can significantly address the issues associated with previous secondary particles, thereby improving battery safety and cycle life. However, even with single-particle cathode active materials, if the sintering and disintegration process conditions are not properly controlled, particle strength may deteriorate, minimizing the aforementioned battery performance enhancements.

[0008]

[0009] Accordingly, one object of the present invention is to provide a cathode active material for a lithium secondary battery, which is a single particle-shaped lithium metal oxide with improved particle strength, capable of maximizing the safety and lifespan characteristics of the battery, a method for producing the same, and a lithium secondary battery including the same.

[0010]

[0011] One embodiment of the present invention provides a cathode active material for a lithium secondary battery, which comprises a lithium metal oxide in the form of a single particle containing 50 to 70 mol% of nickel based on the total molar number of metals excluding lithium, and satisfies the following formulas 1 and 2.

[0012] [Formula 1]

[0013] 3.0 μm ≤ Dv50 ≤ 5.0 μm

[0014] [Formula 2]

[0015] Dv50 - Dn50 ≤ 2.0 μm

[0016] In the above equations 1 and 2, Dv50 is the average particle diameter based on the volume of lithium metal oxide, and Dn50 is the average particle diameter based on the number of lithium metal oxide.

[0017]

[0018] The above positive electrode active material for a lithium secondary battery can satisfy the following equation 3.

[0019] [Formula 3]

[0020] Dv50 / Dn50 ≤ 2.0

[0021] In the above equation 3, Dv50 is the average particle diameter based on the volume of lithium metal oxide, and Dn50 is the average particle diameter based on the number of lithium metal oxide.

[0022]

[0023] The above Dn50 may be 2.0 to 3.0 μm.

[0024] The Dn10 of the above lithium metal oxide may be 1.0 μm or more (however, Dn10 is a particle size corresponding to 10% of the cumulative number of lithium metal oxide particles).

[0025] The above lithium metal oxide may be in the form of a single particle.

[0026] The above lithium metal oxide may have an average crystallite size of 255 nm or more.

[0027] The above lithium metal oxide may have an a-axis lattice constant of 2.8751 Å or more.

[0028] The above lithium metal oxide is 1.7 tonf / cm 2 When pressurized with a pressure of , the proportion of fine particles having a particle size of 1 μm or less may be 3.0% or less.

[0029] The above lithium metal oxide can be represented by the following chemical formula 1.

[0030] [Chemical Formula 1]

[0031] Li a [Ni x Coy Mn z M w ]O2

[0032] 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.

[0033]

[0034] Another embodiment of the present invention provides a method for producing a cathode active material for a lithium secondary battery, comprising the steps of: preparing a metal precursor containing 50 to 70 mol% of nickel based on the total mole number of metals; mixing the metal precursor and a lithium raw material, and then performing a first firing and a second firing to form a lithium metal oxide; and crushing the lithium metal oxide to form a lithium metal oxide in the form of single particles, wherein the first firing and the second firing are performed in an air atmosphere.

[0035] The above first firing and the above second firing can each be independently performed at a temperature of 900 to 960°C.

[0036] The above first firing time may be shorter than the above second firing time.

[0037] The above first firing time may be 2 to 6 hours.

[0038] The secondary firing time may be 7 to 14 hours.

[0039]

[0040] Another embodiment of the present invention provides a positive electrode for a lithium secondary battery comprising the positive electrode active material described above.

[0041] Another embodiment of the present invention provides a lithium secondary battery including the positive electrode for the lithium secondary battery.

[0042]

[0043] According to one embodiment of the present invention, a cathode active material for a lithium secondary battery comprises a lithium metal oxide in the form of a single particle, and the average particle diameter based on volume and the average particle diameter based on number of particles of the lithium metal oxide are appropriately controlled to maximize particle strength. Accordingly, the safety and life characteristics of the battery can be maximized.

[0044]

[0045] Figure 1 is a SEM image of a positive electrode active material manufactured according to Example 1.

[0046] Figure 2 is a SEM image of a positive electrode active material manufactured according to Example 2.

[0047] Figure 3 is a SEM image of a positive electrode active material manufactured according to Example 3.

[0048] Figure 4 is an SEM image of a positive electrode active material manufactured according to Comparative Example 1.

[0049] Figure 5 is an SEM image of a positive electrode active material manufactured according to Comparative Example 2.

[0050] Figure 6 is an SEM image of a positive electrode active material manufactured according to Comparative Example 3.

[0051] The terms first, second, and third, etc., are used to describe, but are not limited to, various parts, components, regions, layers, and / or sections. These terms are used solely to distinguish one part, component, region, layer, or section from another part, component, region, layer, or section. Accordingly, a first part, component, region, layer, or section described below may be referred to as a second part, component, region, layer, or section without departing from the scope of the present invention.

[0052] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the present invention. As used herein, the singular forms "singular" and "comprising" include plural forms as well, unless the context clearly dictates otherwise. The word "comprising" as used herein specifies a particular feature, region, integer, step, operation, element, and / or component, but does not exclude the presence or addition of other features, regions, integers, steps, operations, elements, and / or components.

[0053] When a part is referred to as being "on" or "over" another part, it can be directly on or over the other part, or there may be other parts intervening. Conversely, when a part is referred to as being "directly on" another part, there are no other parts intervening.

[0054] Although not defined otherwise, all terms, including technical and scientific terms, used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention pertains. Terms defined in commonly used dictionaries are further interpreted to have meanings consistent with the relevant technical literature and the present disclosure, and are not to be construed as ideal or overly formal unless otherwise defined.

[0055] Also, unless otherwise stated, % means weight%, and 1 ppm is 0.0001 weight%.

[0056] In this specification, the term "combination(s) thereof" described in the expression in the Makushi format means one or more mixtures or combinations selected from the group consisting of the components described in the expression in the Makushi format, and means including any one or more selected from the group consisting of said components.

[0057] Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art can easily implement them. However, the present invention may be implemented in various different forms and is not limited to the embodiments described herein.

[0058]

[0059] 1. Positive active material

[0060] According to one embodiment of the present invention, a cathode active material for a lithium secondary battery comprises a lithium transition metal oxide in the form of a single particle. Compared to conventional secondary particles, the single particle active material has a smaller specific surface area, which reduces the amount of gas generated by side reactions with the electrolyte. Furthermore, the single particle active material has a higher particle strength, which suppresses particle breakage during rolling, and reduces the occurrence of cracks during repeated charging and discharging. Accordingly, the single particle active material has superior lifespan and safety compared to secondary particles, and has the advantage of being able to realize a high energy density of the electrode.

[0061] Meanwhile, in this specification, the term “single particle” is used to distinguish it from the secondary particle type positive electrode active material particle formed by the aggregation of tens to hundreds of primary particles that have been commonly used in the past, and is a concept that includes a single particle composed of one primary particle and an aggregate particle of 30 or fewer primary particles. In addition, “secondary particle” means an aggregate, i.e., a secondary structure, formed by the physical or chemical bonding between tens to hundreds of primary particles without an intentional aggregation or assembly process for the primary particles.

[0062] In addition, in this specification, “primary particle” means the smallest particle unit that can be distinguished as a single lump when observing the cross-section of a positive electrode active material through a scanning electron microscope (SEM), and may be composed of a single crystal grain or multiple crystal grains. In addition, “crystal grain” means a distinct region in the form of a lattice structure in a certain direction formed by atoms within a primary particle.

[0063] Meanwhile, the lithium metal oxide according to one embodiment of the present invention contains 50 to 70 mol% of nickel based on the total mole number of metals excluding lithium. Conventional NCM (nickel-cobalt-manganese ternary) cathode active materials have attempted to implement high capacity of batteries by increasing the nickel content, but if the nickel content is too high, there may be a thermal propagation issue, i.e., a thermal safety problem, and the high nickel price may increase the manufacturing cost. Therefore, the lithium metal oxide according to the present invention has the nickel content adjusted to the above range in order to secure appropriate capacity and thermal safety characteristics while implementing economic feasibility.

[0064] However, if the sintering and disintegration process conditions are not properly controlled, lithium metal oxide particles in this single particle form can generate excessively small, fine particles. These numerous fine particles can cause side reactions with the electrolyte, increasing gas production and potentially reducing the safety and lifespan characteristics of the battery.

[0065] In addition, the inventors of the present invention confirmed that when a large number of fine particles are present among lithium metal oxide particles, the particle strength is deteriorated, and a large number of secondary fine particles are newly generated when a certain pressure is applied to the active material (the experimental results for this will be described in detail in the experimental examples described below). The above-mentioned application of a certain pressure may correspond to the pressure applied during the electrode rolling process. Therefore, a large number of fine particles present immediately after the synthesis of lithium metal oxide may newly generate a large number of secondary fine particles when pressure is applied during the rolling process for implementing an actual positive electrode. This may further accelerate the deterioration of the safety and life characteristics of the battery.

[0066] Accordingly, the inventors of the present invention have completed the present invention by conducting repeated research on the particle size distribution for maximizing the particle strength of single-particle positive electrode active materials. Furthermore, as described below, the particle size distribution can be achieved by precisely controlling the sintering and disintegration process conditions during the production of the positive electrode active material. This will be described in more detail in the manufacturing method described below.

[0067]

[0068] A positive electrode active material for a lithium secondary battery according to one embodiment of the present invention satisfies the following equation 1.

[0069] [Formula 1]

[0070] 3.0 μm ≤ Dv50 ≤ 5.0 μm

[0071] The above Dv50 may be more specifically 3.5 μm or 3.8 μm or more, and 4.5 μm or less.

[0072]

[0073] In addition, the positive electrode active material for a lithium secondary battery according to one embodiment of the present invention satisfies the following equation 2.

[0074] [Formula 2]

[0075] Dv50 - Dn50 ≤ 2.0 μm

[0076] The above Dv50 - Dn50 value may be more specifically 1.5 μm to 2.0 μm.

[0077]

[0078] In addition, the positive electrode active material for a lithium secondary battery according to the present invention can satisfy the following equation 3.

[0079] [Formula 3]

[0080] Dv50 / Dn50 ≤ 2.0

[0081] In the above equation 3, Dv50 is the average particle diameter based on the volume of lithium metal oxide, and Dn50 is the average particle diameter based on the number of lithium metal oxide.

[0082] The above Dv50 / Dn50 value may be more specifically 1.6 to 2.0.

[0083]

[0084] In the above equations 1 to 3, Dv50 is the volume-based average particle diameter of the lithium metal oxide, and Dn50 is the number-based average particle diameter of the lithium metal oxide. More specifically, the volume-based average particle diameter (Dv50) can be defined as a particle diameter corresponding to 50% of the volume accumulation amount in the particle diameter distribution curve of the particles. The number-based average particle diameter (Dn50) can be defined as a particle diameter corresponding to 50% of the number accumulation amount in the particle diameter distribution curve of the particles. The volume-based average particle diameter (Dv50) and the number-based average particle diameter (Dn50) can be measured using, for example, a laser diffraction method.

[0085]

[0086] When the positive electrode active material for a lithium secondary battery according to the present invention satisfies Equation 1, it is possible to simultaneously and preferably implement high electrode density and electrochemical characteristics such as capacity and output. More specifically, if Dv50 is too small, the density of the positive electrode active material may become too small, which may lower the electrode density and consequently lower the electrode energy density. If Dv50 is too large, lithium ion mobility may decrease, which may lower the capacity and output characteristics. Therefore, when the positive electrode active material satisfies Equation 1, the electrode density and capacity characteristics can be appropriately improved at the same time, making it possible to implement high energy density of the electrode.

[0087]

[0088] When the cathode active material for a lithium secondary battery according to the present invention satisfies Equation 2 or Equation 3, the safety and life characteristics of the battery can be maximized. The difference between Dv50 and Dn50, or the Dv50 / Dn50 value, can represent the proportion of fine particles in lithium metal oxide particles. More specifically, the Dv50 value can generally exhibit a value greater than the Dn50 value. At this time, as the Dn50 value approaches the Dv50 value, it can mean that the proportion of fine particles decreases. Therefore, when the cathode active material satisfies Equation 2 or Equation 3, the proportion of fine particles decreases, and for the same reasons as mentioned above, the safety and life characteristics of the battery can be improved.

[0089] The above Dn50 may be more specifically 2.0 to 3.0 μm, and more specifically 2.0 to 2.51 μm.

[0090]

[0091] Meanwhile, the Dn10 of the lithium metal oxide may be 1.0 μm or more, and more specifically, may be 1.0 to 1.435 μm. As the Dn10 value of the lithium metal oxide is sufficiently large, the proportion of fine particles within the lithium metal oxide particles may be reduced, and for the same reasons as mentioned above, the safety and life characteristics of the battery may be improved.

[0092] The above Dn10 can be defined as the particle diameter corresponding to 10% of the accumulated number of particles in the particle diameter distribution curve. The particle diameter based on the number (Dn10) can be measured using, for example, the laser diffraction method.

[0093]

[0094] In addition, the lithium metal oxide may be in the form of a single particle. In this specification, "single particle" means a single particle composed of only one primary particle. In addition, in this specification, the lithium metal oxide being in the form of a "single particle" means that the number ratio of single particles composed of only one primary particle among a plurality of lithium metal oxide particles is 90% or more. Since the lithium metal oxide is in the form of a single particle, the particle strength is further improved, and the aforementioned effects of improving the safety and life characteristics of the battery can be more preferably implemented.

[0095]

[0096] In addition, the lithium metal oxide may have an average crystallite size of 255 nm or more, and more specifically, 260 nm or more. Since the average crystallite size of the lithium metal oxide is sufficiently large, the particle strength is further improved, and the aforementioned effects of improving the safety and life characteristics of the battery can be more preferably implemented. Meanwhile, in the present specification, the “average crystallite size” can be estimated using peak broadening of XRD data, and can be quantitatively calculated using the Scherr equation. In addition, the average crystallite size of the lithium metal oxide can also be easily obtained by precisely controlling the sintering process conditions during the manufacture of the positive electrode active material.

[0097] In addition, the lithium metal oxide may have an a-axis lattice constant of 2.8751 Å or more. The a-axis lattice of the lithium metal oxide may increase as the average crystal grain size of the lithium metal oxide increases, and when the a-axis lattice constant is sufficiently large, the particle strength is further improved, so that the aforementioned effects of improving the safety and life characteristics of the battery may be more preferably implemented. Meanwhile, in the present specification, the “a-axis lattice constant” can be estimated using peak broadening of XRD data, and can be quantitatively calculated through the Scherr equation. In addition, the a-axis lattice constant of the lithium metal oxide can also be easily obtained by precisely controlling the sintering process conditions during the manufacture of the positive electrode active material.

[0098]

[0099] Accordingly, the lithium metal oxide according to the present invention has a particle strength of 1.7 tonf / cm 2 When pressurized with a pressure of , the proportion of fine particles having a particle size of 1 μm or less may be 3.0% or less.

[0100] The above properties can be measured more specifically by the following method. After placing 3.00 g of a positive electrode active material sample into a mold with a diameter of 1.3 cm, 1.7 tonf / cm 2 Pressurize with the force of . After that, the pressurized pellet-shaped positive electrode active material is put into a mortar and ground to break up the clumped particles. After that, 0.01 g of the positive electrode active material is added to 61 mL of 10 wt% (NaPO3) as a dispersant, and then ultrasonicated for 1 minute. After that, a particle size analysis is performed using Malvern (MS3000) equipment to measure the volume % of fine particles with a particle size of 1 μm or less, thereby measuring the fine particle ratio.

[0101]

[0102] The above lithium metal oxide can be more specifically represented by the following chemical formula 1.

[0103] [Chemical Formula 1]

[0104] Li a [Ni x Co y Mn z M w ]O2

[0105] 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.

[0106] In the lithium transition metal oxide of the above chemical formula 1, lithium may be included in a content corresponding to a, that is, 0.8≤a≤1.2. If a is too small, the capacity may be reduced, and if a is too large, the strength of the sintered positive electrode active material may be increased, making pulverization difficult, and the amount of gas generated may increase due to an increase in lithium byproducts. Considering the effect of improving the capacity characteristics of the positive electrode active material according to the control of the lithium content and the sinterability balance during the production of the active material, the lithium may be included in a content of 0.9≤a≤1.1 more preferably.

[0107] In the lithium transition metal oxide of the above chemical formula 1, nickel may be included in an amount corresponding to x, i.e., 0.5≤x≤0.7. If the nickel content is too low, it may be difficult to achieve high capacity of the battery, and if the nickel content is too high, the battery life and thermal safety may be reduced due to a decrease in the structural stability of the active material, and the manufacturing cost may increase.

[0108] In the lithium transition metal oxide of the above chemical formula 1, cobalt may be included in an amount 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 high powder density of the active material. If the cobalt content is too high, the overall cost of the raw material may increase and the reversible capacity may decrease.

[0109] In the lithium transition metal oxide of the above chemical formula 1, manganese may be included in a content 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 may increase and the stability of the active material may deteriorate. If the manganese content is too high, the capacity and output characteristics of the battery may deteriorate.

[0110] In the lithium transition metal oxide of the above chemical formula 1, M may be included in a content corresponding to w, that is, 0≤w≤0.2. At this time, M is a doping element and may be Zr, Al, B, Y, Mg, Ti, Nb, W, Sc, Si, V, Fe, Y, Mo, Ce, Hf, Ta, La, Sr, or a combination thereof.

[0111]

[0112] 2. Method for manufacturing positive electrode active material

[0113] The particle size-related properties, including the Dv50 - Dn50 values, of a positive electrode active material for a lithium secondary battery according to one embodiment of the present invention can be obtained by precisely controlling the sintering and crushing process conditions. Hereinafter, a method for manufacturing a positive electrode active material will be described.

[0114] Another embodiment of the present invention provides a method for producing a cathode active material for a lithium secondary battery, comprising the steps of: preparing a metal precursor containing 50 to 70 mol% of nickel based on the total mole number of metals; mixing the metal precursor and a lithium raw material, and then performing a first firing and a second firing to form a lithium metal oxide; and pulverizing the lithium metal oxide to form a lithium metal oxide in the form of single particles, wherein the first firing and the second firing are performed in an air atmosphere.

[0115] Hereinafter, a method for manufacturing a positive electrode active material for a lithium secondary battery according to another embodiment of the present invention will be described in detail step by step.

[0116]

[0117] First, a metal precursor containing 50 to 70 mol% of nickel based on the total mole number of metals is prepared.

[0118] The metal precursor may be, for example, a metal hydroxide.

[0119] The above metal hydroxide may be produced by a coprecipitation reaction by adding a solution containing a complexing agent and a solution containing a pH adjuster to a transition metal-containing solution including, for example, a nickel raw material and optionally a cobalt raw material or a manganese raw material.

[0120] The above nickel raw material is not particularly limited as long as it is used in the art for manufacturing a positive electrode active material precursor. For example, the nickel raw material may be a nickel-containing sulfate, acetate, nitrate, halide, sulfide, hydroxide, oxide, or oxyhydroxide, and specifically, may be NiSO4, NiSO4·6H2O, Ni(OH)2, NiO, NiOOH, NiCO3·2Ni(OH)2·4H2O, NiC2O2·2H2O, Ni(NO3)2·6H2O, fatty acid nickel salt, nickel halide, or a combination thereof, but is not limited thereto.

[0121] The above cobalt raw material is not particularly limited as long as it is used in the art for manufacturing a positive electrode active material precursor. For example, the cobalt raw material may be a cobalt-containing sulfate, acetate, nitrate, halide, sulfide, hydroxide, oxide, or oxyhydroxide, and specifically, CoSO 4, It may be, but is not limited to, CoSO4ㆍ7H2O, Co(OH)2, CoOOH, Co(OCOCH3)2ㆍ4H2O, Co(NO3)2ㆍ6H2O or a combination thereof.

[0122] The manganese raw material is not particularly limited as long as it is used in the art for manufacturing a precursor of a cathode active material. For example, the manganese raw material may be a manganese-containing sulfate, acetate, nitrate, halide, sulfide, hydroxide, oxide, oxyhydroxide, or a combination thereof, and specifically, may be a manganese salt such as MnSO4, MnCO3, Mn(NO3)2, manganese acetate, manganese dicarboxylic acid salt, manganese citrate, and manganese fatty acid salt, manganese oxide such as Mn2O3, MnO2, and Mn3O4, oxyhydroxide, manganese chloride, or a combination thereof, but is not limited thereto.

[0123] The above transition metal-containing solution may be prepared by adding a nickel raw material and optionally a cobalt raw material or a manganese raw material to a solvent, specifically, water, or a mixture of water and an organic solvent (e.g., alcohol, etc.) that can be uniformly mixed with water.

[0124] The above complexing agent-containing solution performs the function of forming a complex, and may include, but is not limited to, NH3, NH4OH, (NH4)2SO4, NH4NO3, NH4Cl, CH3COONH4, NH4CO3 or a combination thereof as the complexing agent. Meanwhile, the complexing agent-containing solution may be used in the form of an aqueous solution, and at this time, water or a mixture of water and an organic solvent (e.g., alcohol, etc.) that can be uniformly mixed with water may be used as the solvent.

[0125] The above pH adjusting agent-containing solution acts as a precipitant or pH adjusting agent, and may include an alkaline compound such as a hydroxide of an alkali metal or alkaline earth metal, such as NaOH, KOH, or Ca(OH)2, a hydrate thereof, or a combination thereof. Meanwhile, the pH adjusting agent-containing solution may also be used in the form of an aqueous solution, and at this time, water or a mixture of water and an organic solvent (e.g., alcohol, etc.) that can be uniformly mixed with water may be used as the solvent. At this time, the pH adjusting agent-containing solution may be added in an amount such that the pH of the reaction solution becomes 11 to 13.

[0126] The above coprecipitation reaction can be performed under an inert atmosphere such as nitrogen or argon, can be performed at a temperature of 30 to 70°C, and can be performed at a pH of 11 to 13.

[0127] Nickel-(cobalt-manganese-doped element) hydroxide particles are generated through the above process and precipitated within the reaction solution. The precipitated precursor particles can be separated, washed, and dried using conventional methods to obtain the precursor. The precursor may be a secondary particle formed by the agglomeration of primary particles.

[0128] At this time, the molar ratio of nickel, cobalt, and manganese in the precursor can be controlled by controlling the concentration of nickel raw material, cobalt raw material, and manganese raw material.

[0129] Accordingly, the content of nickel in the metal precursor may be 50 to 70 mol% based on the total mole number of the metal. The technical significance of controlling the content of nickel in the metal precursor is as described above and therefore is omitted.

[0130]

[0131] Next, the metal precursor and lithium raw material are mixed, and then subjected to primary and secondary calcination to form lithium metal oxide.

[0132] In the past, the formation of lithium transition metal oxides in the form of single particles was achieved by only performing a primary calcination at high temperatures for a long time. However, this resulted in problems such as nickel cation mixing due to over-calcination and the formation of Rocksalt impurities, which resulted in a deterioration in the electrochemical properties of the active material. On the other hand, the manufacturing method according to the present invention can prevent the above problems by performing the calcination in two stages, thereby improving the particle strength of the active material and increasing the production volume.

[0133] At this time, both the first and second firings are performed in an air atmosphere. When the firing atmosphere is performed in an air atmosphere compared to an oxygen (O2) atmosphere, the fine particles are reduced, the Dn50 value increases, and particle size-related properties including the Dv50 - Dn50 value are appropriately obtained within the range according to the present invention, so that the particle strength can be improved. The inventors believe that this is because when the cathode material is fired, the particles may grow together and aggregate, or only the crystallinity of individual particles may increase, and the particle growth mechanism during firing may vary depending on the atmospheric CO2 and O2 fractions.

[0134] The above air atmosphere may be, more specifically, an air atmosphere having an oxygen partial pressure of 21% or less.

[0135] In addition, the first firing and the second firing may be independently performed at a temperature of 900 to 960°C. If the firing temperature is too low, lithium metal oxide in the form of single particles may not be easily formed, and the Dn50 value may become too small as the fine particles increase, resulting in poor particle strength. If the firing temperature is too high, electrochemical characteristics such as capacity and output may deteriorate due to over-firing, and the pulverization pressure (Jet-Mill) may become too large, and the Dn50 value may become small as the fine particles increase accordingly, resulting in poor particle strength.

[0136] In addition, the first firing time may be shorter than the second firing time. When the first firing time is shorter than the second firing time, the fine particles decrease, the Dn50 value increases, and particle size-related properties, including the Dv50 - Dn50 value, are appropriately obtained within the range according to the present invention, so that the particle strength can be improved.

[0137] The above first firing time may be more specifically 2 to 6 hours. If the first firing time is too short, the Dn50 value may become too small due to the increase in fine particles, resulting in poor particle strength. If the first firing time is too long, two Jet-Mill crushing processes are required, resulting in a Dn50 value too small due to the increase in fine particles, resulting in poor particle strength.

[0138] The secondary firing time may be, more specifically, 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, resulting in poor particle strength. If the secondary firing time is too long, the Dn50 value may become too small due to an increase in the Jet-Mill pressure for crushing under-fired particles, resulting in poor particle strength.

[0139]

[0140] Next, the lithium metal oxide is crushed to form lithium metal oxide in the form of single particles.

[0141] The above disintegration can be performed by dividing it into primary and secondary disintegration. By performing the disintegration separately into primary and secondary disintegration, the agglomerated secondary particles can be efficiently released into the form of single particles.

[0142] The above primary disintegration can be performed using disintegration equipment commonly used in the art. For example, the above primary disintegration can be performed using a rotor mill, but is not necessarily limited thereto.

[0143] At this time, the first disintegration can be performed at a stirring speed of 15,000 to 20,000 rpm. When the stirring speed during the first disintegration satisfies the above range, the first disintegration is performed with an appropriate force, thereby appropriately reducing the fine particles, so that the Dn50, Dv50-Dn50 values ​​and other physical properties of the lithium metal oxide can be appropriately implemented within the range according to the present invention.

[0144] The secondary disintegration described above can be performed using disintegration equipment commonly used in the art. For example, the secondary disintegration can be performed using a jet mill, but is not necessarily limited thereto.

[0145] At this time, the secondary disintegration can be performed so that the volume-based average particle diameter (Dv50) of the lithium transition metal oxide becomes 3.0 to 5.0 μm. As the secondary disintegration is controlled so that the volume-based average particle diameter (Dv50) of the lithium transition metal oxide becomes within the above range, various physical properties of the obtained lithium metal oxide, such as Dn50 and Dv50-Dn50 values, can be appropriately implemented within the range according to the present invention.

[0146] The above secondary disintegration can be performed at a crushing pressure of 2.1 to 5.4 bar. When the crushing pressure satisfies the above range during the secondary disintegration, the secondary disintegration is performed with an appropriate force, thereby appropriately reducing the fine particles, so that the various physical properties of the lithium metal oxide, such as the Dn50 and Dv50-Dn50 values, can be appropriately implemented within the range according to the present invention.

[0147]

[0148] Through the above series of manufacturing methods, a lithium metal oxide in the form of a single particle according to the present invention can be formed, and the obtained lithium metal oxide can have various physical properties, such as Dv50-Dn50 values, satisfying the range according to the present invention.

[0149]

[0150] 3. Cathode ray and lithium secondary battery

[0151] Another embodiment of the present invention provides a positive electrode for a lithium secondary battery comprising the positive electrode active material described above.

[0152] More specifically, the positive electrode may include a positive electrode current collector and a positive electrode active material layer disposed on the positive electrode current collector, and including the positive electrode active material described above.

[0153] The positive electrode current collector is not particularly limited as long as it is conductive and does not cause a chemical change in the battery, and for example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, etc. may be used. In addition, the positive electrode current collector may typically have a thickness of 3 to 500 μm, and fine unevenness may be formed on the surface of the positive electrode current collector to increase the adhesion of the positive electrode active material. For example, it may be used in various forms such as a film, sheet, foil, net, porous body, foam, or non-woven fabric.

[0154] The above-described positive electrode active material layer may include a binder and / or a conductive material together with the above-described positive electrode active material.

[0155] At this time, the binder plays a role of improving the adhesion between the positive electrode active material particles and the adhesive strength between the positive electrode active material and the positive electrode current collector. Specific examples include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer rubber (EPDM rubber), sulfonated-EPDM, styrene butadiene rubber (SBR), fluororubber, or various copolymers thereof, and one kind alone or a mixture of two or more kinds thereof may be used, but is not limited thereto. The binder may be included in an amount of 1 to 30 wt% based on the total weight of the positive electrode active material layer.

[0156] And, the conductive material is used to provide conductivity to the electrode, and in the battery to be constructed, as long as it does not cause a chemical change and has electronic conductivity, it can be used without any special restrictions. Specific examples include graphite such as natural graphite or artificial graphite; carbon-based materials such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, summer black, and carbon fiber; metal powder or metal fiber such as copper, nickel, aluminum, and silver; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives, and the like. One type alone or a mixture of two or more types among these may be used, but the present invention is not limited thereto. The conductive material may typically be included in an amount of 1 to 30 wt% based on the total weight of the positive electrode active material layer.

[0157] The above positive electrode can be manufactured according to a conventional positive electrode manufacturing method, except that the above positive electrode active material is used.

[0158] Specifically, the positive electrode can be manufactured by applying a composition for forming a positive electrode active material layer, including the positive electrode active material described above and optionally a binder, a conductive agent, or a solvent, on a positive electrode current collector, followed by drying and rolling. At this time, the types and contents of the positive electrode active material, binder, and conductive agent are as described above.

[0159] The solvent may be a solvent generally used in the relevant technical field, such as dimethylsulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, or water. One of these may be used alone or a mixture of two or more thereof may be used. The amount of the solvent used is sufficient to dissolve or disperse the positive electrode active material, conductive material, and binder, taking into account the coating thickness and manufacturing yield of the slurry, and to have a viscosity that can exhibit excellent thickness uniformity when applied thereafter for manufacturing the positive electrode.

[0160] Alternatively, the positive electrode may be manufactured by casting the composition for forming the positive electrode active material layer on a separate support, and then laminating the resulting film on a positive electrode current collector by peeling it off from the support.

[0161]

[0162] Another embodiment of the present invention provides a lithium secondary battery including the positive electrode for a lithium secondary battery as described above.

[0163] The above lithium secondary battery may more specifically include a positive electrode; a negative electrode; a separator; and an electrolyte.

[0164] The above lithium secondary battery may optionally further include a battery container that houses an electrode assembly of the positive electrode, negative electrode, and separator, and a sealing member that seals the battery container.

[0165] The above negative electrode may include a negative electrode current collector and a negative electrode active material layer positioned on the negative electrode current collector.

[0166] The negative electrode current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery, and for example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., aluminum-cadmium alloy, etc. can be used. In addition, the negative electrode current collector can typically have a thickness of 3 to 500 ㎛, and like the positive electrode current collector, fine unevenness can be formed on the surface of the current collector to strengthen the bonding strength of the negative electrode active material. For example, it can be used in various forms such as a film, a sheet, a foil, a net, a porous body, a foam, a non-woven fabric, etc.

[0167] The negative electrode active material layer may optionally include a binder and a conductive material together with the negative electrode active material. As an example, the negative electrode active material layer may be manufactured by applying a composition for forming a negative electrode active material layer comprising the negative electrode active material and optionally a binder and a conductive material onto a negative electrode current collector and drying the composition, or by casting the negative electrode forming composition onto a separate support and then laminating the resulting film onto a negative electrode current collector by peeling the film off from the support.

[0168] As the negative electrode active material, a compound capable of reversible intercalation and deintercalation of lithium may be used. Specific examples thereof include carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber, and amorphous carbon; metallic compounds capable of alloying with lithium, such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloy, Sn alloy, and Al alloy; metallic oxides capable of doping and dedoping lithium, such as SiOβ (0 < β < 2), SnO2, vanadium oxide, and lithium vanadium oxide; or composites comprising the metallic compounds and carbonaceous materials, such as Si-C composites or Sn-C composites, and any one or a mixture of two or more of these may be used. In addition, a metallic lithium thin film may be used as the negative electrode active material. In addition, both low-crystalline carbon and high-crystalline carbon may be used as the carbonaceous material. Representative examples of low-crystalline carbon include soft carbon and hard carbon, and representative examples of high-crystalline carbon include natural graphite or artificial graphite in the form of amorphous, plate-like, flaky, spherical, or fiber-like forms, Kish graphite, pyrolytic carbon, mesophase pitch-based carbon fiber, meso-carbon microbeads, mesophase pitches, and high-temperature calcined carbon such as petroleum or coal tar pitch derived cokes.

[0169] The above binder and conductive material may be the same as those described above for the positive electrode.

[0170]

[0171] The above separator separates the negative electrode and the positive electrode and provides a passage for lithium ions to move. Any separator commonly used as a separator in lithium secondary batteries can be used without any particular restrictions. In particular, a separator having low resistance to ion movement of the electrolyte and excellent electrolyte moisture absorption capacity is preferable. Specifically, a porous polymer film, for example, a porous polymer film made of a polyolefin polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, and an ethylene / methacrylate copolymer, or a laminated structure of two or more layers thereof, may be used. In addition, a conventional porous nonwoven fabric, for example, a nonwoven fabric made of high-melting-point glass fiber, polyethylene terephthalate fiber, etc. may be used. In addition, a coated separator containing a ceramic component or a polymer material to secure heat resistance or mechanical strength may be used, and may optionally be used in a single-layer or multi-layer structure.

[0172]

[0173] The above electrolyte may include, but is not limited to, organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel-type polymer electrolytes, solid inorganic electrolytes, and molten inorganic electrolytes that can be used in the manufacture of lithium secondary batteries.

[0174] Specifically, the organic liquid electrolyte may include an organic solvent and a lithium salt.

[0175] The organic solvent may be used without any particular limitation as long as it can serve as a medium through which ions involved in the electrochemical reaction of the battery can move. Specifically, the organic solvent may include ester solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, and ε-caprolactone; ether solvents such as dibutyl ether or tetrahydrofuran; ketone solvents such as cyclohexanone; aromatic hydrocarbon solvents such as benzene and fluorobenzene; Carbonate solvents such as dimethylcarbonate (DMC), diethylcarbonate (DEC), methylethylcarbonate (MEC), ethylmethylcarbonate (EMC), ethylene carbonate (EC), and propylene carbonate (PC); alcohol solvents such as ethyl alcohol and isopropyl alcohol; nitriles such as R-CN (wherein R is a C2 to C20 linear, branched, or cyclic hydrocarbon group, and may include a double-bonded aromatic ring or an ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; or sulfolanes can be used. Among these, a carbonate solvent is preferable, and a mixture of a cyclic carbonate (e.g., ethylene carbonate or propylene carbonate, etc.) having high ionic conductivity and high dielectric constant that can improve the charge / discharge performance of the battery and a linear carbonate compound having low viscosity (e.g., ethyl methyl carbonate, dimethyl carbonate, or diethyl carbonate, etc.) is more preferable.In this case, the performance of the electrolyte may be improved when the cyclic carbonate and the chain carbonate are mixed and used in a volume ratio of about 1:1 to about 1:9.

[0176] The lithium salt may be used without any particular limitation as long as it is a compound capable of providing lithium ions used in a lithium secondary battery. Specifically, the lithium salt may be LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAl04, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2. LiCl, LiI, or LiB(C2O4)2. It is preferable that the concentration of the lithium salt be used within the range of 0.1 to 2.0 M. When the concentration of the lithium salt is within the above range, the electrolyte can exhibit excellent electrolyte performance because it has appropriate conductivity and viscosity, and lithium ions can move effectively.

[0177] In addition to the electrolyte components, the electrolyte may further include one or more additives, such as haloalkylene carbonate compounds such as difluoroethylene carbonate, pyridine, triethylphosphite, triethanolamine, cyclic ethers, ethylene diamine, n-glyme, hexamethylphosphoric acid triamide, nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinones, N,N-substituted imidazolidines, ethylene glycol dialkyl ethers, ammonium salts, pyrrole, 2-methoxyethanol, or aluminum trichloride, for the purpose of improving the life characteristics of the battery, suppressing battery capacity decrease, and improving the discharge capacity of the battery. At this time, the additives may be included in an amount of 0.1 to 5 wt% based on the total weight of the electrolyte.

[0178] As described above, a lithium secondary battery including a cathode active material according to the present invention stably exhibits excellent discharge capacity, output characteristics, and capacity retention, and is therefore useful in portable devices such as mobile phones, laptop computers, and digital cameras, and electric vehicles such as hybrid electric vehicles (HEVs).

[0179] Accordingly, another embodiment of the present invention provides a battery module including the lithium secondary battery as a unit cell and a battery pack including the same.

[0180] The above battery module or battery pack can be used as a power source for one or more medium- to large-sized devices, such as a power tool; an electric vehicle (EV), a hybrid electric vehicle, and a plug-in hybrid electric vehicle (PHEV); or a power storage system.

[0181]

[0182] Hereinafter, embodiments of the present invention will be described in more detail through examples. However, the following examples are merely preferred embodiments of the present invention, and the present invention is not limited to the following examples.

[0183]

[0184] Example 1

[0185] (1) Manufacturing of positive electrode active material

[0186] (Mixed) Ni 0.6 Co 0.1 Mn 0.3 (OH)2 composition precursor and LiOH·H2O were introduced into a mixer and mechanically mixed to form a mixture so that the molar ratio (Li / M) of lithium to the transition metal of the precursor was 1.07.

[0187] (1st firing) After that, the mixture was heated to 930°C through heat treatment in an air atmosphere with an oxygen partial pressure of 21%, and then 1st firing was performed at a constant temperature of 930°C for 4 hours, and then naturally cooled. Thereafter, the 1st fired material was pulverized using a rotor mill.

[0188] (Secondary firing) Afterwards, the above-mentioned crushed primary fired material was subjected to secondary firing at a constant temperature of 930°C for 12 hours through heat treatment in an air atmosphere with an oxygen partial pressure of 21%, and then naturally cooled to form lithium metal oxide.

[0189] Both the first and second firings were performed inside a Lab box.

[0190] (1st disintegration) After that, the lithium metal oxide was disintegrated for the first time using a rotor mill at a stirring speed of 18,000 rpm.

[0191] (Secondary disintegration) After secondary disintegration using a jet mill at a crushing pressure of 4.0 bar, lithium transition metal oxide in the form of single particles was formed.

[0192] The composition of the final obtained lithium transition metal oxide is Li 1.07 Ni 0.6 Co 0.1 Mn 0.3 It was O2.

[0193]

[0194] (2) Lithium secondary battery manufacturing

[0195] The slurry for manufacturing the electrode plate was mixed with the above-mentioned positive electrode active material: conductive material (carbon black, Denka black): binder (PVDF, KF9700) = 95.0:2.0:3.0 wt%, and the viscosity was adjusted so that the solid content was approximately 60% by adding NMP (N-Methyl-2-pyrrolidone). The manufactured slurry was coated on a 20 μm thick Al foil using a doctor blade, and then dried and rolled. The electrode loading was 16.0 mg / cm 2 and the rolling density (25 ℃, 20 kN) was 3.5 g / cm 3 It was.

[0196] The electrolyte was 1M LiPF6in EC:DMC:DEC=1:2:1 (vol%), with 2.0 vol% VC added to the total amount of the electrolyte, and a coin cell was manufactured using a PP separator and a lithium negative electrode (400 μm, Niba metal).

[0197]

[0198] Example 2

[0199] A positive electrode active material and a lithium secondary battery were manufactured in the same manner as in Example 1, except that the first firing time was 4 hours in the first firing step and the second firing time was 10 hours in the second firing step.

[0200]

[0201] Example 3

[0202] A positive electrode active material and a lithium secondary battery were manufactured in the same manner as in Example 1, except that the first firing time was 4 hours in the first firing step and the second firing time was 8 hours in the second firing step.

[0203]

[0204] Example 4

[0205] A cathode active material and a lithium secondary battery were manufactured in the same manner as in Example 1, except that the first firing time was 4 hours in the first firing step, the second firing time was 10 hours in the second firing step, and the first and second firings were performed in an RHK firing furnace.

[0206]

[0207] Example 5

[0208] A cathode active material and a lithium secondary battery were manufactured in the same manner as in Example 1, except that the first firing time was 4 hours in the first firing step, the second firing time was 9 hours in the second firing step, and the first and second firings were performed in an RHK firing furnace.

[0209]

[0210] Example 6

[0211] A cathode active material and a lithium secondary battery were manufactured in the same manner as in Example 1, except that the first firing time was 4 hours in the first firing step, the second firing time was 8 hours in the second firing step, and the first and second firings were performed in an RHK firing furnace.

[0212]

[0213] Comparative Example 1

[0214] A cathode active material and a lithium secondary battery were manufactured in the same manner as in Example 1, except that the sintering was not performed by dividing it into the first sintering and the second sintering, but was performed for 14 hours as the first sintering, and the first sintering was performed in an RHK sintering furnace.

[0215]

[0216] Comparative Example 2

[0217] A cathode active material and a lithium secondary battery were manufactured in the same manner as in Example 1, except that the first firing time was 4 hours in the first firing step, the second firing time was 10 hours in the second firing step, and both the first and second firings were performed in an oxygen (O2) atmosphere with an oxygen partial pressure of 96% or higher.

[0218]

[0219] Comparative Example 3

[0220] A cathode active material and a lithium secondary battery were manufactured in the same manner as in Example 1, except that the first firing time was 4 hours in the first firing step, the second firing time was 11 hours in the second firing step, and both the first and second firings were performed in an oxygen (O2) atmosphere with an oxygen partial pressure of 96% or higher.

[0221]

[0222] Table 1 below summarizes the process conditions for examples and comparative examples.

[0223] Classification1st firing2nd firingFiring furnaceTemperature (℃)Time (h)AtmosphereTemperature (℃)Time (h)AtmosphereExample 19304Air93012AirLab boxExample 29304Air93010AirLab boxExample 39304Air9308AirLab boxExample 49304Air93010AirRHKExample 59304Air9309AirRHKExample 69304Air9308AirRHKComparative example 193014AirXXXRHKComparative example 29304O293010O2Lab boxComparative example 39304O293011O2Lab box

[0224]

[0225] Experimental Example 1: Evaluation of SEM images of positive electrode active materials

[0226] SEM (scanning electron microscope) images of the positive electrode active materials manufactured according to Examples 1 to 3 and Comparative Examples 1 to 3 were observed, and are shown in FIGS. 1 to 6, respectively, in that order.

[0227] Referring to FIGS. 1 to 6, it was confirmed that the positive electrode active materials of the examples and comparative examples were in the form of single particles.

[0228]

[0229] Experimental Example 2: Evaluation of the properties of positive electrode active materials

[0230] (1) Dv50 and Dn50, Dv50 / Dn50, Dv50 - Dn50, Dn10 evaluation

[0231] The volume-based average particle diameter (Dv50) was measured by measuring the particle diameter corresponding to 50% of the volume accumulation amount using the laser diffraction method, and the number-based average particle diameter (Dn50) and Dn10 were measured by measuring the particle diameters corresponding to 50% and 10% of the number accumulation amount. Afterwards, Dv50 / Dn50 and Dv50 - Dn50 were calculated using these.

[0232] (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

[0233] After placing 3.00 g of positive electrode active material sample into a mold with a diameter of 1.3 cm, 1.7 tonf / cm 2 Pressurization was performed with the force of . Afterwards, the pressurized pellet-shaped positive electrode active material was put into a mortar and ground to break up the clumped particles. Afterwards, 0.01 g of the positive electrode active material was added to 61 mL of 10 wt% (NaPO3) as a dispersant, and ultrasonic treatment was performed for 1 minute. Afterwards, particle size analysis was performed using Malvern (MS3000) equipment to measure the volume % of fine particles with a particle size of 1 μm or less, and the fine particle ratio was determined.

[0234] (3) Evaluation of average grain size and a-axis lattice constant

[0235] The average grain size and a-axis lattice constant were evaluated by applying peak broadening and Scherr equation of XRD data.

[0236] DivisionDv50(μm)Dn50(μm)Dv50-Dn50(μm)Dv50 / Dn50Dn10(μm)1.7tonf / cm 2 Differential ratio at application (%)Average grain size (nm)a-axis lattice constant (Å)Example 14.122.821.31.4611.7401.32782.8778Example 23.992.81.191.4251.7501.52882.8752Example 33.862.521.341.5321.45022762.8752Example 44.052.511.541.6141.4202.32832.8765Example 53.972.381.591. 6681.2902.42802.8767Example 63.882.271.611.7091.2002.72692.8770Comparative Example 13.931.652.282.3820.9604.42472.8748Comparative Example 24.030.893.144.5280.5406.32122.8750Comparative Example 33.990.93.094.4330.5406.62152.8749

[0237] Referring to Table 2, in the case of the examples in which the sintering and disintegration process conditions were appropriately controlled, it was confirmed that the fine particles were reduced, the Dn50 value was sufficiently increased, and all physical properties such as the Dv50-Dn50 value were appropriately obtained within the range according to the present invention. In addition, it was confirmed that the average grain size and the a-axis lattice constant were largely realized. In addition, it was confirmed that the fine particle ratio was very excellent at a level of 3.0% or less when pressure was applied, and it was confirmed that the particle strength was greatly improved. On the other hand, in the case of Comparative Example 1, which was not performed separately into the first and second sinterings but was sintered for a long time with only the first sintering, the Dn50 value was small, and all physical properties such as the Dv50-Dn50 value were outside the range according to the present invention. In addition, it was confirmed that the average grain size and the a-axis lattice constant were realized smaller than in the examples. In addition, it was confirmed that the fine particle ratio was deteriorated to a level of 4.4% when pressure was applied, compared to the examples.

[0238] In addition, in the case of Comparative Examples 2 and 3, in which the first and second firings were performed in an oxygen (O2) atmosphere rather than an air atmosphere, the Dn50 value was significantly reduced, and it was confirmed that the overall physical properties, such as the Dv50-Dn50 values, were significantly outside the range according to the present invention. In addition, it was confirmed that the average grain size and the a-axis lattice constant were implemented smaller than in the examples. In addition, it was confirmed that the differentiation ratio when pressure was applied was significantly lower than in the examples, exceeding 6.0%.

[0239]

[0240] Experimental Example 3: Evaluation of Electrochemical Characteristics of Lithium Secondary Battery

[0241] (1) Initial capacity and initial efficiency evaluation

[0242] After fabricating a lithium secondary battery half-cell, it was aged at 25°C for 10 hours and then subjected to a charge-discharge test at 25°C. To evaluate the initial capacity, the reference capacity was set to 200 mAh / g, and the battery was charged to 4.4 V at a constant current of 0.1 C. Then, the battery was switched to a constant voltage and charged until the end current reached 0.05 C. After a 10-minute rest time after charging, the battery was discharged at a constant current of 0.1 C until the battery reached 2.5 V, using the reference capacity of 200 mAh / g.

[0243] (2) Evaluation of high temperature resistance increase rate (45℃, 50 cycles)

[0244] After fabricating a lithium secondary battery half-cell, it was charged to 4.4 V at a constant current of 0.2 C at 45°C, then switched to constant voltage and charged until the end current reached 0.05 C. After a rest time of 10 minutes after charging, it was discharged at a constant current of 1.0 C until it reached 2.5 V. Under these charge-discharge cycle conditions, 50 charge-discharge cycles were performed, and the resistance increase rate of the 50th cycle compared to the first cycle was calculated.

[0245] Initial charge capacity (mAh / g) Initial discharge capacity (mAh / g) Initial efficiency (%) Life cycle characteristics (high temperature resistance increase rate, %)Example 1214.0190.489.0%124.6%Example 2214.0192.089.8%135.3%Example 3215.8193.489.6%136.9%Example 4213.8191.289.5%112.0%Example 5209.7185.988.7%103.6%Example 6210.7187.388.9%106.4%Comparative Example 1212.9190.989.7%154.9%Comparative Example 2213.7193.690.6%138.5%Comparative Example 3213.6193.890.7%168.5%

[0246] Referring to Table 3, in the case of the examples, it was confirmed that the life characteristics were significantly superior to the comparative examples as a result of the various physical properties, including the Dv50 - Dn50 values, being appropriately controlled within the range according to the present invention. On the other hand, in the case of the comparative examples, it was confirmed that the life characteristics were significantly deteriorated compared to the examples as a result of the various physical properties, including the Dv50 - Dn50 values, being outside the range according to the present invention. This was 1.7 tonf / cm 2 It appears that the rate of differentiation during application is proportional to the rate of differentiation that occurs during electrode pressing, and that by controlling this property, the rate of differentiation that occurs during electrode production can be controlled, thereby improving the life characteristics (high-temperature resistance increase rate) of the battery.

[0247] Meanwhile, it was confirmed that the capacity characteristics of the examples and the comparative system were almost at the same level. Through this, it was confirmed that in the case of the examples according to the present invention, the life characteristics were improved without a significant deterioration in the capacity characteristics as a result of appropriately controlling all physical properties, including the Dv50 - Dn50 values, within the range according to the present invention.

[0248]

[0249] Although the preferred embodiments of the present invention have been described above, the present invention is not limited thereto, and various modifications can be made within the scope of the patent claims, the detailed description of the invention, and the attached drawings, and it is obvious that this also falls within the scope of the present invention.

[0250] Accordingly, the actual scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. Contains a lithium metal oxide in the form of a single particle containing 50 to 70 mol% of nickel based on the total moles of metals excluding lithium, A positive electrode active material for a lithium secondary battery, satisfying the following equations 1 and 2: [Formula 1] 3.0 μm ≤ Dv50 ≤ 5.0 μm [Formula 2] Dv50 - Dn50 ≤ 2.0 μm In the above equations 1 and 2, Dv50 is the average particle diameter based on the volume of lithium metal oxide, and Dn50 is the average particle diameter based on the number of lithium metal oxide.

2. In paragraph 1, A cathode active material for a lithium secondary battery satisfying the following equation 3: [Formula 3] Dv50 / Dn50 ≤ 2.0 In the above equation 3, Dv50 is the average particle diameter based on the volume of lithium metal oxide, and Dn50 is the average particle diameter based on the number of lithium metal oxide.

3. In paragraph 1, The above Dn50 is a positive electrode active material for a lithium secondary battery having a diameter of 2.0 to 3.0 μm.

4. In paragraph 1, The above lithium metal oxide has a Dn10 of 1.0 μm or more, and is a cathode active material for a lithium secondary battery (however, Dn10 is a particle size corresponding to 10% of the cumulative number of lithium metal oxide particles).

5. In paragraph 1, The above lithium metal oxide is a positive electrode active material for a lithium secondary battery in the form of a single particle.

6. In paragraph 1, The above lithium metal oxide is a positive electrode active material for a lithium secondary battery having an average crystallite size of 255 nm or more.

7. In paragraph 1, The above lithium metal oxide is a positive electrode active material for a lithium secondary battery having an a-axis lattice constant of 2.8751 Å or more.

8. In paragraph 1, The above lithium metal oxide is 1.7 tonf / cm 2 A positive electrode active material for a lithium secondary battery, wherein the proportion of fine particles having a particle size of 1 μm or less when pressurized is 3.0% or less.

9. In paragraph 1, The above lithium metal oxide is a positive electrode active material for a lithium secondary battery represented by the following chemical formula 1: [Chemical Formula 1] Li a [Ni x Co y Mr z M w ]O2 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 to 70 mol% of nickel based on the total mole number of metals; A step of forming a lithium metal oxide by mixing the above metal precursor and lithium raw material, and then performing a first firing and a second firing; and A step of crushing the lithium metal oxide to form a lithium metal oxide in the form of single particles is included. The above first firing and the above second firing are performed in an air atmosphere. A method for manufacturing a cathode active material for a lithium secondary battery.

11. In paragraph 10, A method for producing a positive electrode active material for a lithium secondary battery, wherein the first firing and the second firing are each independently performed at a temperature of 900 to 960°C.

12. In paragraph 10, A method for manufacturing a positive electrode active material for a lithium secondary battery, wherein the first firing time is shorter than the second firing time.

13. In paragraph 10, A method for manufacturing a positive electrode active material for a lithium secondary battery, wherein the first firing time is 2 to 6 hours.

14. In paragraph 10, A method for manufacturing a positive electrode active material for a lithium secondary battery, 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 of any one of claims 1 to 9.

16. A lithium secondary battery comprising the positive electrode for a lithium secondary battery of Article 15.

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