Cathode active material precursor, cathode active material, cathode, and electrochemical device

Abstract

The present invention relates to a cathode active material comprising: 80 mol% or more of nickel among all metals excluding lithium; and at least one type of doping elements, wherein the at least one type of doping elements has an average value of a first doping uniformity index as defined by equation 1, measured for individual doping elements, of 16% or less, and a particle strength of 121 MPa or more. [Equation 1]First doping uniformity index=[NSD] / [Navg] wherein, in equation 1, [NSD] is a standard deviation value of a molar ratio of the individual doping elements to Mn in the entire cathode active material, and [Navg] is an average value of a molar ratio of the individual doping elements to Mn in the entire cathode active material.

Description

Cathode active material precursor, cathode active material, cathode, and electrochemical device

[0001] Cross-citation with related applications

[0002] This application claims the benefit of priority from Korean Patent Application No. 10-2024-0117212, filed August 29, 2024, the entire contents of which are incorporated herein by reference.

[0003] Technology field

[0004] The present invention relates to a cathode active material precursor, a cathode active material, a cathode, and an electrochemical device.

[0005]

[0006] The recent rapid proliferation of battery-powered electronic devices such as mobile phones, laptops, and electric vehicles has led to a rapid increase in demand for compact, lightweight, and relatively high-capacity secondary batteries. In particular, lithium secondary batteries, with their lightweight design and high energy density, are attracting attention as power sources for portable devices. Accordingly, active research and development efforts are underway to improve the performance of lithium secondary batteries.

[0007] Lithium secondary batteries produce electrical energy through oxidation and reduction reactions when lithium ions are inserted / deintercalated from the positive and negative electrodes, while charging an organic electrolyte or polymer electrolyte between the positive and negative electrodes, which are made of active materials capable of intercalating and deintercalating lithium ions.

[0008] 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.

[0009] Accordingly, a nickel-cobalt-manganese lithium composite transition metal oxide was developed in which some of the cobalt (Co) is replaced with nickel (Ni) and manganese (Mn). Conventional lithium nickel-cobalt-manganese oxides are usually in the form of spherical secondary particles in which tens to hundreds of primary particles are aggregated. However, in the case of lithium nickel-cobalt-manganese oxides in the form of secondary particles in which many primary particles are aggregated, there is a problem in that the primary particles are easily broken during the rolling process during the manufacture of the positive electrode, and cracks occur inside the particles during the charge and discharge process. When the particles of the positive electrode active material are broken or cracked, the contact area with the electrolyte increases, which increases the generation of gases and degradation of the active material due to side reactions with the electrolyte, and this causes a problem in that the life characteristics are reduced.

[0010] To address the above issues, a technique has been proposed to improve battery life by introducing dopants into the crystals of cathode active materials. However, if the dopants are not uniformly incorporated within the particles, localized doping or overdoping can occur, resulting in reduced electrochemical performance and, in turn, negatively impacting battery life.

[0011]

[0012] The present invention is intended to solve the above problems and to provide a positive electrode active material precursor capable of forming a positive electrode active material with improved doping uniformity and particle strength.

[0013] In addition, the present invention aims to provide a positive electrode active material manufactured from the positive electrode active material precursor, which has improved doping uniformity and particle breakage and initial resistance.

[0014] In addition, the present invention seeks to provide a cathode and electrochemical device having excellent resistance characteristics and high-temperature lifespan characteristics by applying the cathode active material.

[0015]

[0016] [1] The present invention provides a positive electrode active material comprising nickel in an amount of 80 mol% or more among all metals excluding lithium, and comprising at least one doping element, wherein the at least one doping element has an average value of a first doping uniformity index defined by the following formula 1 measured for each individual doping element of 16% or less, and a particle strength of 121 MPa or more.

[0017] [Formula 1]

[0018] First doping uniformity index = [N SD ] / [N avg ]

[0019] In the above equation 1, [N SD ] is the standard deviation value of the molar ratio of the individual doping elements to Mn in the entire positive electrode active material, and [N avg ] is the average value of the molar ratio of the individual doping elements to Mn in the entire positive electrode active material.

[0020] [2] The present invention relates to a positive electrode active material in which, in the above [1], the one or more types of doping elements have an average value of the first doping uniformity index defined by the above formula 1 measured for each individual doping element of 9.5% or less.

[0021] [3] The present invention relates to a positive electrode active material, wherein, in the above [1] or [2], the one or more doping elements have an average value of a second doping uniformity index defined by the following formula 2 measured for each individual doping element of 95% to 105%.

[0022] [Formula 2]

[0023] Second doping uniformity index = [N 1 / 2 ] / [N avg ]

[0024] In the above equation 2, [N 1 / 2 ] is D from the center of the positive electrode active material. 50 / 2 is the molar ratio of the individual doping elements relative to Mn measured at the position, [N avg ] is the average value of the molar ratio of the individual doping elements to Mn in the entire positive electrode active material.

[0025] [4] The present invention provides a positive electrode active material, wherein in at least one of the above [1] to [3], the positive electrode active material has a particle strength of 125 MPa or more and 135 MPa or less.

[0026] [5] The present invention provides a positive electrode active material having a crystallite size of (003) plane measured by X-ray diffraction analysis (XRD) of 107 nm or more in at least one of the above [1] to [4].

[0027] [6] The present invention, in at least one of the above [1] to [5], the positive electrode active material has an average particle diameter D 50 A positive electrode active material having a size of 7㎛ or more and 15㎛ or less is provided.

[0028] [7] The present invention provides a positive electrode active material, wherein in at least one of the above [1] to [6], the positive electrode active material has a sphericity of 0.91 or more.

[0029] [8] The present invention provides a positive electrode active material, wherein in at least one of the above [1] to [7], the positive electrode active material has a pore area ratio of 0.02 or more and 0.10 or less.

[0030] [9] The present invention provides a positive electrode active material, wherein, in at least one of the above [1] to [8], the doping element is included in an amount of 5,000 ppm to 15,000 ppm based on the total weight of the positive electrode active material.

[0031]

[0010] The present invention provides a positive electrode comprising at least one positive electrode active material among the above [1] to [9].

[0032]

[0011] The present invention provides an electrochemical device including the positive electrode of the above

[0010] .

[0033]

[0012] The present invention provides a positive electrode active material precursor comprising nickel in an amount of 80 mol% or more among the total metal, having a sphericity of 0.83 or more, and a pore area ratio (PAR) of 0.04 or more and 0.10 or less.

[0034]

[0013] The present invention provides a positive electrode active material precursor having a pore area ratio of 0.05 or more and 0.08 or less in the above

[0012] .

[0035]

[0014] The present invention provides a positive electrode active material precursor having a sphericity of 0.85 or more and 0.92 or more in the above

[0012] or

[0013] .

[0036]

[0015] The present invention, in at least one of the above

[0012] to

[0014] , has an average particle diameter D of a positive electrode active material precursor. 50 A positive electrode active material precursor having a size of 7㎛ or more and 15㎛ or less is provided.

[0037]

[0016] The present invention provides a positive electrode active material precursor having a crystallite size of the (001) plane measured by X-ray diffraction analysis (XRD) of 15 nm or more in at least one of the above

[0012] to

[0015] .

[0038]

[0017] The present invention provides a positive electrode active material precursor comprising cobalt in an amount of 1 mol% or more and 10 mol% or less among the total metals in at least one of

[0012] to ]16].

[0039]

[0040] The positive electrode active material precursor of the present invention has the effect of controlling the sphericity and pore area ratio (PAR) at the precursor level before firing, thereby improving the doping uniformity and particle strength of the positive electrode active material manufactured from the positive electrode active material precursor.

[0041] The positive electrode active material manufactured from the positive electrode active material precursor of the present invention has the effect of uniform doping throughout the positive electrode active material, excellent particle strength, improved initial resistance, and excellent electrochemical performance.

[0042] The positive electrode and electrochemical device of the present invention can have excellent initial resistance characteristics and excellent life characteristics and high-temperature life characteristics by applying the positive electrode active material.

[0043]

[0044] Figure 1 shows the results of measuring the amount of Al doping from the particle center to the surface using inductively coupled plasma optical emission spectroscopy (ICP-OES) for each of the positive electrode active materials manufactured using the positive electrode active material precursors manufactured in Examples 1 to 2 and Comparative Examples 1 to 4.

[0045] Figure 2 shows the results of measuring the doping amount of Zr from the particle center to the surface using inductively coupled plasma optical emission spectroscopy (ICP-OES) for each of the positive electrode active materials manufactured using the positive electrode active material precursors manufactured in Examples 1 to 2 and Comparative Examples 1 to 4.

[0046] Figure 3 shows the results of measuring the doping amount of Sr from the particle center to the surface using inductively coupled plasma optical emission spectroscopy (ICP-OES) for each of the positive electrode active materials manufactured using the positive electrode active material precursors manufactured in Examples 1 to 2 and Comparative Examples 1 to 4.

[0047] FIG. 4 shows the results of measuring the doping amount of Sb from the particle center to the surface using inductively coupled plasma optical emission spectroscopy (ICP-OES) for each of the positive electrode active materials manufactured using the positive electrode active material precursors manufactured in Examples 1 to 2 and Comparative Examples 1 to 4.

[0048]

[0049] Terms or words used in this specification and claims should not be interpreted as limited to their usual or dictionary meanings, but should be interpreted as meanings and concepts that conform to the technical spirit of the present invention, based on the principle that the inventor can appropriately define the concept of the term to explain his or her own invention in the best possible manner.

[0050] It should be understood that the terms “include,” “comprising,” or “having” used in this specification are intended to specify the presence of a feature, number, step, component, or combination thereof, but do not preclude the possibility of the presence or addition of one or more other features, numbers, steps, components, or combinations thereof.

[0051] In the present invention, "secondary particle" refers to a particle formed by the agglomeration of tens to hundreds of primary particles. More specifically, the secondary particle is an agglomerate of 50 or more primary particles.

[0052] In the present invention, "average particle diameter D 50 " means the particle size based on 50% of the volume cumulative particle size distribution of the target material. The average particle diameter (or center particle diameter) D 50 can be measured using the laser diffraction method. For example, after dispersing the target material in a dispersion medium, it can be measured by introducing it into a commercially available laser diffraction particle size measuring device (e.g., Microtrac MT 3000), irradiating it with ultrasonic waves of approximately 28 kHz at an output of 60 W, obtaining a volume-cumulative particle size distribution graph, and then calculating the particle size corresponding to 50% of the volume-cumulative amount.

[0053] In the present invention, “average value” may mean an arithmetic mean value.

[0054] In the present invention, "sphericity" is obtained by two-dimensionalizing the particles using a cross-sectional image obtained through scanning electron microscope (SEM) photography of the positive electrode active material precursor / positive electrode active material particles, and using an image analysis program for the two-dimensionalized image to determine the minimum particle diameter (D) of the particles. min , short diameter), maximum diameter (D max, a value derived from the diameter and area (Area), which means an average value of tens to hundreds of particles, preferably 300 particles in the present invention, and is specifically calculated through the following formula A.

[0055] [Formula A] Roundness = (4 x Area) / (π x (D max ) 2 )

[0056] For example, the sphericity can be measured by the following method.

[0057] A slurry is prepared by mixing the precursor / positive electrode active material for the positive electrode active material with carbon black, PVDF binder, and N-methylpyrrolidone at a weight ratio of 95:2:3, and the slurry is applied to one side of an aluminum current collector having a thickness of 20 μm. The applied slurry is dried to prepare an electrode, and the electrode is dried under Ar + Using ion beams The cross-section is cut using an ion milling device (manufacturer: Hitachi, product name: IM5000, acceleration voltage: 6 kV, ion beam current: 400 μA). The cross-section image of the electrode is obtained by scanning electron microscopy of the cut electrode cross-section. Afterwards, the minimum particle diameter (D) of the particle is determined using an image analysis program for the cross-section image of the electrode. min , short diameter), maximum diameter (D max , the diameter) and area (Area) are derived, and the sphericity of the positive electrode active material precursor / positive electrode active material can be derived from the arithmetic mean value calculated using the above formula A for the sphericity of tens to hundreds, or 300 positive electrode active material precursor / positive electrode active material particles.

[0058] In addition, since the sphericity in this specification is a value derived from a scanning electron microscope cross-sectional image, it is not substantially different from the meaning of 'circularity', but the value analyzed as circularity in image interpretation is expressed as sphericity considering that the positive electrode active material precursor / positive electrode active material particle is a three-dimensional particle.

[0059] In the present invention, the pore area ratio (PAR) refers to the ratio of the pore area to the internal area of ​​the positive electrode active material precursor / positive electrode active material particle. In this case, when measuring the pore area, the hollow portion located at the center of the positive electrode active material precursor / positive electrode active material particle may not be considered a pore.

[0060] Specifically, the pore area ratio (PAR) can be measured by a pore distribution analysis method by using a scanning electron microscope (SEM) image of the positive electrode active material precursor / positive electrode active material particles to make the particles into two-dimensional particles and analyzing the two-dimensional images using an image analysis program. For example, a positive electrode slurry is prepared by mixing the positive electrode active material precursor / positive electrode active material with carbon black, PVDF binder, and N-methylpyrrolidone at a weight ratio of 95:2:3, and the positive electrode slurry is applied to one surface of a 20 μm thick aluminum current collector. The applied positive electrode mixture layer is dried at 130°C to make an electrode, and the electrode is dried under Ar + Using ion beams The cross-section is cut using an ion milling device (manufacturer: Hitachi, product name: IM5000, acceleration voltage: 6 kV, ion beam current: 400 μA). The cross-section of the cut electrode is photographed using a scanning electron microscope (SEM) to obtain a cross-sectional image of the electrode active material layer. Thereafter, for the cross-sectional image of the electrode active material layer, the voids in the positive electrode active material precursor / positive electrode active material particles are indicated as shaded, and the dense parts in the positive electrode active material precursor / positive electrode active material particles are indicated as white using image analysis software WinRoof 6.1.1. The ratio of [shaded area / (shaded area + white area)] is calculated for each of 100 or more precursor particles among the measured positive electrode active material precursor / positive electrode active material, and the pore area ratio (PAR) can be obtained by calculating the arithmetic average value thereof.

[0061]

[0062] Hereinafter, the present invention will be described in detail.

[0063] The cathode active material precursor, cathode active material, cathode, and / or electrochemical device according to the present invention comprises at least one of the configurations disclosed below, and may comprise any combination between technically feasible configurations among the configurations below.

[0064]

[0065] Cathode active material precursor

[0066] The positive electrode active material precursor of the present invention may contain nickel in an amount of 80 mol% or more, 82 mol% or more, 85 mol% or more, 87 mol% or more, 90 mol% or more, 92 mol% or more, 93 mol% or more, 94 mol% or more, 95 mol% or more, 96 mol% or more, 99 mol% or less, 98 mol% or less, or 97 mol% or less of the total metal. For example, the positive electrode active material precursor of the present invention may contain nickel in an amount of 80 mol% or more, 90 mol% or more, 90 mol% or more, 93 mol% or more, or 95 mol% or more and 99 mol% or less of the total metal. When the above range is satisfied, a positive electrode active material having a high energy density can be manufactured.

[0067]

[0068] The positive electrode active material precursor of the present invention may contain cobalt in an amount of 1 mol% or more, 2 mol% or more, 3 mol% or more, 10 mol% or less, 7 mol% or less, 6 mol% or less, 5 mol% or less, 4 mol% or less, or 3 mol% or less of the total metal. For example, the positive electrode active material precursor of the present invention may contain cobalt in an amount of 10 mol% or less, 1 mol% or more and 10 mol% or less, 1 mol% or more and 7 mol% or less, 1 mol% or more and 5 mol% or less, or 2 mol% or more and 4 mol% or less of the total metal. When the above range is satisfied, a cost advantage can be achieved by containing a relatively small amount of cobalt, while a certain level or higher of output characteristics can be secured.

[0069]

[0070] The positive electrode active material precursor of the present invention may contain manganese in an amount of 0.1 mol% or more, 0.5 mol% or more, 0.8 mol% or more, 1 mol% or more, 10 mol% or less, 7 mol% or less, 5 mol% or less, 4 mol% or less, 3 mol% or less, 2 mol% or less, or 1 mol% or less of the total metal. For example, the positive electrode active material precursor of the present invention may contain manganese in an amount of 10 mol% or less, 0.1 mol% or more and 7 mol% or less, 0.5 mol% or more and 5 mol% or less, 0.8 mol% or more and 3 mol% or less, or 0.8 mol% or more and 2 mol% or less of the total metal. When the above range is satisfied, the energy density of the manufactured positive electrode active material can be secured while having excellent structural stability.

[0071]

[0072] The positive electrode active material precursor of the present invention may include a nickel-based hydroxide containing nickel, cobalt, and manganese.

[0073]

[0074] The positive electrode active material precursor of the present invention may have a composition represented by the following chemical formula 1 or chemical formula 2.

[0075] [Chemical Formula 1] [Ni a Co b Mn c ](OH)2

[0076] [Chemical Formula 2] [Ni a Co b Mn c ]O·OH

[0077] In the above chemical formulas 1 and 2, a represents the molar ratio of nickel among the total metal in the positive electrode active material precursor, and may be 0.8≤a<1, 0.8≤a≤0.99, 0.85≤a≤0.99, 0.88≤a≤0.99, 0.9≤a≤0.99, 0.93≤a≤0.99, 0.95≤a≤0.98, or 0.97≤a≤0.99.

[0078] In the above chemical formulas 1 and 2, b represents the molar ratio of cobalt among the total metals in the positive electrode active material precursor, and is 0. <b<0.2, 0.01≤b≤0.1, 0.02≤b≤0.07, 0.02≤b≤0.05, 또는 0.02≤b≤0.04일 수 있다.

[0079] In the above chemical formulas 1 and 2, b represents the molar ratio of manganese among the total metals in the positive electrode active material precursor, and is 0. <c<0.2, 0.001≤c≤0.1, 0.005≤c≤0.05, 0.008≤c≤0.03또는 0.008≤c≤0.02일 수 있다.

[0080]

[0081] The sphericity of the positive electrode active material precursor of the present invention may be 0.83 or more, 0.85 or more, 0.88 or more, 0.9 or more, 0.92 or more, 0.99 or less, 0.95 or less, 0.93 or less, or 0.92 or less. For example, the sphericity of the positive electrode active material precursor may be 0.83 or more, 0.83 or more and 0.99 or less, or 0.85 or more and 0.92 or less. When the sphericity of the positive electrode active material precursor of the present invention is 0.83 or more, the particle sizes of the precursor particles in each three-dimensional direction become similar, so that the dopant can have a uniform distribution in the positive electrode active material manufactured from the positive electrode active material precursor.

[0082]

[0083] Average particle diameter D of the positive electrode active material precursor of the present invention 50 The average particle diameter D of the positive electrode active material precursor of the present invention may be 7 ㎛ or more, 7 ㎛ or more and 15 ㎛ or less, 10 ㎛ or more and 14 ㎛ or less, 11 ㎛ or more and 13.5 ㎛ or less, or 12 ㎛ or more and 13 ㎛ or less. 50When this is excessively small, when the pore area ratio and sphericity of the positive electrode active material precursor satisfy the range according to the present invention, the specific surface area may increase, and the dopant may have an uneven distribution in the positive electrode active material manufactured from the positive electrode active material precursor. In addition, as the particle strength of the positive electrode active material decreases, the high-temperature life characteristics and resistance characteristics may deteriorate. Therefore, the average particle diameter D of the positive electrode active material precursor of the present invention 50 When this above range is satisfied, the dopant can have a uniform distribution and particle strength can be secured in the positive electrode active material manufactured from the positive electrode active material precursor by combining the pore area ratio (PAR) and sphericity range of the positive electrode active material precursor of the present invention.

[0084]

[0085] The pore area ratio (PAR) of the positive electrode active material precursor of the present invention may be 0.04 or more and 0.10 or less. Specifically, the pore area ratio (PAR) of the positive electrode active material precursor of the present invention may be 0.04 or more, 0.05 or more, 0.06 or more, 0.07 or more, 0.075 or more, 0.10 or less, 0.095 or less, 0.09 or less, 0.085 or less, 0.08 or less, or 0.075 or less. For example, the pore area ratio (PAR) of the positive electrode active material precursor of the present invention may be 0.04 or more and 0.10 or less, 0.05 or more and 0.09 or less, 0.05 or more and 0.08 or less, 0.06 or more and 0.08 or less, or 0.07 or more and 0.08 or less. When the pore area ratio (PAR) of the positive electrode active material precursor satisfies the above range, the doping element can easily move within the positive electrode active material precursor, so that the doping element can have a uniform distribution in the positive electrode active material manufactured from the positive electrode active material precursor. In addition, sufficient particle strength can be secured in the positive electrode active material manufactured from the positive electrode active material precursor.

[0086]

[0087] The crystallite size of the (001) plane of the positive electrode active material precursor of the present invention may be 15 nm or more, 18 nm or more, 30 nm or less, 25 nm or less, 23 nm or less, 20 nm or less, or 19 nm or less as measured by X-ray diffraction analysis (XRD). For example, the crystallite size of the (001) plane of the positive electrode active material precursor of the present invention may be 15 nm or more, 15 nm to 30 nm, 15 nm to 25 nm, 17 nm to 25 nm, or 18 nm to 20 nm as measured by X-ray diffraction analysis (XRD). In the present invention, the “crystallite size of the (001) plane” means an average value of the size of the (001) plane of the positive electrode active material precursor as measured by X-ray diffraction analysis (XRD), and more specifically, it can be obtained through the Rietveld method using XRD data. Specifically, the crystallite size of the (001) plane can be obtained by placing a sample into the central groove of a general powder holder, smoothing the surface of the sample using a slide glass while making the height the same as the edge of the holder, and then using an X-ray diffractometer (Bruker, D8 Endeavor) to measure XRD data (2θ=15°~90°, Step size=0.02°, total scan time: 20 min) using the Fundamental Parameter Approach built into Bruker's TOPAS program based on the Rietveld method. Since the (001) plane in the positive electrode active material precursor is related to the movement path of lithium ions in the positive electrode active material being manufactured, when the (001) plane crystallite size satisfies the above range, a layered structure can be stably formed, and doping uniformity can be improved.

[0088]

[0089] The positive electrode active material precursor of the present invention may include positive electrode active material precursor particles containing nickel in an amount of 80 mol% or more of the total metal, having a sphericity of 0.83 or more, and having a pore area ratio (PAR) of 0.04 or more and 0.10 or less.

[0090] The positive electrode active material precursor of the present invention may contain 50% by volume or more, 60% by volume or more, 70% by volume or more, or 80% by volume or more of the positive electrode active material precursor particles. In this case, the positive electrode active material manufactured from the manufactured positive electrode active material precursor may contain a majority of particles having a uniform distribution of dopants and may have excellent particle strength, thereby improving resistance and life characteristics.

[0091]

[0092] The positive electrode active material precursor according to the present invention can be manufactured by the following manufacturing method, but is not limited thereto.

[0093] The positive electrode active material precursor of the present invention can be manufactured by performing (1) a first step of forming a positive electrode active material precursor nucleus (seed) by supplying a transition metal-containing solution, an ammonium cation complex forming agent, and a basic solution to a reactor while performing a coprecipitation reaction; and (2) a second step of growing positive electrode active material precursor particles by supplying a transition metal-containing solution, an ammonium cation complex forming agent, and a basic solution to the reaction solution in which the positive electrode active material precursor nucleus is formed while performing a coprecipitation reaction.

[0094]

[0095] First, a coprecipitation reaction can be carried out by supplying a transition metal-containing solution, an ammonium cation complex forming agent, and a basic solution to the reactor, thereby forming a positive electrode active material precursor nucleus (seed). (Step 1)

[0096] The above reactor may contain a reaction mother liquid. Specifically, before supplying the reaction raw materials, i.e., a transition metal-containing solution, an ammonium cation complex forming agent, and a basic solution, the ammonium cation complex forming agent, the basic solution, and water may be first introduced into the reactor to form a reaction mother liquid.

[0097] At this time, the ammonium cation complex forming agent may include an ammonium cation complex forming agent compound including at least one selected from the group consisting of NH4OH, (NH4)2SO4, NH4NO3, NH4Cl, CH3COONH4, and NH4CO3, and may be introduced into the reactor in the form of a solution in which the compound is dissolved in a solvent. At this time, as the solvent, water or a mixture of water and an organic solvent (specifically, alcohol, etc.) that can be uniformly mixed with water may be used. Most preferably, NH4OH, i.e., ammonia water, may be used.

[0098] The ammonium cation complex forming agent may have a concentration including the ammonium cation complex forming agent compound of 20 wt% or less, 1 wt% to 15 wt%, 3 wt% to 12 wt%, or 6 wt% to 8 wt%. When the above range is satisfied, it can contribute to controlling the sphericity and pore area ratio of the manufactured positive electrode active material precursor to satisfy the range according to the present invention.

[0099] Next, the basic solution may include at least one basic compound selected from the group consisting of NaOH, KOH, and Ca(OH)2, and may be introduced into the reactor in the form of a solution in which the compound is dissolved in a solvent. At this time, the solvent may be water, or a mixture of water and an organic solvent (specifically, alcohol, etc.) that can be uniformly mixed with water.

[0100]

[0101] The basic solution may have a concentration comprising the basic compound of 10 wt% to 40 wt%, 15 wt% to 35 wt%, 20 wt% to 30 wt%, or 23 wt% to 27 wt%.

[0102]

[0103] The above reaction mother liquid can be formed so that the pH is 9 to 12.5, or 10 to 12. When the pH of the reaction mother liquid satisfies the above range, the formation of a positive electrode active material precursor nucleus can occur smoothly.

[0104] Meanwhile, it is preferable to form a reaction mother liquid by adding an ammonium cation complex forming agent, a basic solution, and water to the reactor, and then remove oxygen in the reaction mother liquid by purging with nitrogen gas.

[0105]

[0106] Next, when a transition metal-containing solution, an ammonium cation complex forming agent, and a basic solution are supplied to a reactor containing a reaction mother liquid and stirred, a coprecipitation reaction may proceed, thereby forming a positive electrode active material precursor nucleus.

[0107] Specifically, when a transition metal-containing solution, an ammonium cation complex forming agent, and a basic aqueous solution are supplied to a reactor containing a reaction mother liquid and stirred, a coprecipitation reaction proceeds, precursor nuclei in the form of primary particles are generated (nucleation), and when the nuclei in the form of primary particles aggregate, nuclei in the form of secondary particles (seeds) can be formed.

[0108]

[0109] The ammonium cation complex forming agent and basic aqueous solution may be the same as those described above.

[0110] In the first step, the ammonium cation complex forming agent may be supplied at a flow rate of 1 L / hr or more and 10 mL / hr or less, 1.5 mL / hr or more and 5 mL / hr or 2 mL / hr or more and 4 mL / hr. When the above range is satisfied, the growth rate of the positive electrode active material precursor nucleus can be smoothly maintained.

[0111] In the first step, the ammonium cation complex forming agent can be supplied to the reactor at an increasing flow rate.

[0112] At this time, the transition metal-containing solution may include nickel, cobalt, and manganese elements, and may be formed by mixing nickel raw material, cobalt raw material, and manganese raw material in water.

[0113] The above nickel raw material may be Ni(OH)2, NiO, NiOOH, NiCO3·2Ni(OH)2·4H2O, NiC2O2·2H2O, Ni(NO3)2·6H2O, NiSO4, NiSO4·6H2O, fatty acid nickel salt or nickel halide, and any one or a mixture of two or more of these may be used, but is not limited thereto.

[0114] The above cobalt raw material may be Co(OH)2, CoOOH, Co(OCOCH3)2ㆍ4H2O, Co(NO3)2ㆍ6H2O or Co(SO4)2ㆍ7H2O, and any one or a mixture of two or more of these may be used, but is not limited thereto.

[0115] The above manganese raw material may be manganese oxides such as Mn2O3, MnO2, and Mn3O4; manganese salts such as MnCO3, Mn(NO3)2, MnSO4, manganese acetate, manganese dicarboxylic acid salt, manganese citrate, and manganese fatty acid salt; oxyhydroxide, or manganese chloride, and any one or a mixture of two or more thereof may be used, but is not limited thereto.

[0116] The above transition metal-containing solution may include a nickel raw material such that the nickel content is 80 mol% or more, 90 mol% or more, 90 mol% or more, 97 mol% or more, or 97 mol% or more and 99 mol% with respect to the total metal. When the nickel content in the transition metal-containing solution is 80 mol% or more, the capacity characteristics can be further improved.

[0117] The above transition metal-containing solution can be supplied to the reactor at a flow rate of 0.1 L / h to 40 L / h, 10 L / h to 35 L / h, 20 L / h to 30 L / h, or 22 L / h to 28 L / h.

[0118] The above first step may be performed for 80 hours or less, or 70 hours or less. When the above first step is performed for the above time, the positive electrode active material precursor nuclei are sufficiently formed, the particle size distribution can be uniform, and the particle strength and productivity can be excellent.

[0119] Additionally, the pH of the reaction solution in the first step may be 10 to 12.5, 11 to 12, or 11.5 to 11.9.

[0120] In the first step above, the pH of the reaction solution may decrease during the reaction.

[0121] In the first step, the pH of the reaction solution may be reduced from 11 to 12, 11.5 to 12, or 11.7 to 11.9. In the first step, the pH of the reaction solution may be reduced from 11 to 12, 11.3 to 11.9, or 11.5 to 11.7. In this case, it may contribute to controlling the sphericity and pore area ratio of the manufactured positive electrode active material precursor to satisfy the range according to the present invention.

[0122] In the first step, the temperature of the reaction solution may be 30°C to 80°C, 40°C to 70°C, or 45°C to 60°C. When the pH and temperature of the reaction solution satisfy the above ranges, nuclei of positive electrode active material precursors are formed within the reaction solution, and the process of the nuclei agglomerating to form nuclei can smoothly occur. The pH of the reaction solution can be controlled by adjusting the amount of alkaline solution added using a pH sensor or the like.

[0123] The above first step can be performed in an oxidizing atmosphere. The oxidizing atmosphere can be formed by introducing an oxygen-containing gas at a flow rate such that the oxygen content is 0.1 L / h to 10 L / h, 0.5 L / h to 5 L / h, or 1 L / h to 3 L / h. When the above range is satisfied, the particle size of the positive electrode active material precursor can be made uniform, and the positive electrode active material precursor can be formed so that the sphericity and pore area ratio satisfy the desired range.

[0124] The above oxygen-containing gas may be a gas having an oxygen content of 21% or more, such as the atmosphere, and preferably a gas having an oxygen content of 25% or more.

[0125]

[0126] Meanwhile, when the reactor is full in the first stage, the supply of raw materials is stopped, stirring is stopped, the precursor particles in the reaction solution are allowed to settle, the supernatant is removed, and the supply of raw materials is then resumed to proceed with the reaction. By performing the process of removing the supernatant in the reactor as described above, sufficient reaction time required for precursor particle growth can be secured, thereby controlling the degree of sphericity and the pore area ratio. In addition, the precursor production amount can be increased. The above process can be repeated two or more times. The above process can be performed before the second stage described below.

[0127]

[0128] Next, when the positive electrode active material precursor nuclei are sufficiently formed through the above process, a transition metal-containing solution, an ammonium cation complex forming agent, and a basic solution are supplied to the reaction solution in which the positive electrode active material precursor nuclei are formed, thereby causing a co-precipitation reaction to grow positive electrode active material precursor particles. (Step 2)

[0129] Specifically, a transition metal-containing solution, an ammonium cation complex forming agent, and a basic solution are supplied to the reaction solution in which the positive electrode active material precursor nuclei are formed, and while stirring, a coprecipitation reaction is performed to grow positive electrode active material precursor particles.

[0130] The transition metal-containing solution, ammonium cation complex forming agent, and basic solution used in the second step are the same as those used in the first step.

[0131] In the second step, the transition metal-containing solution may be supplied at an increased flow rate. In the second step, the flow rate of the transition metal-containing solution may be reduced 6 to 20 hours, or 7 to 12 hours after introduction. In this case, it may contribute to controlling the sphericity and pore area ratio of the manufactured positive electrode active material precursor to satisfy the ranges according to the present invention.

[0132] In the second step, the pH of the reaction solution may be 9 to 12, 10 to 11.5, 10.5 to 11.3, or 10.9 to 11.1. The temperature of the reaction solution in the second step may be 50°C to 80°C, 60°C to 77°C, 65°C to 75°C, or 67°C to 72°C. When the pH and temperature of the reaction solution satisfy the above ranges, particle growth may occur smoothly. In addition, it may contribute to controlling the sphericity and pore area ratio of the manufactured positive electrode active material precursor to satisfy the ranges according to the present invention. The pH of the reaction solution may be controlled by a method of adjusting the amount of alkaline solution added using a pH sensor or the like.

[0133]

[0134] The above second step may be conducted in a nitrogen atmosphere. In this case, it may contribute to controlling the sphericity and pore area ratio of the manufactured positive electrode active material precursor to satisfy the ranges according to the present invention.

[0135]

[0136] When the precursor particles are sufficiently grown through the above process, the precursor particles can be separated from the reaction solution, washed, and dried to obtain positive electrode active material precursor particles.

[0137]

[0138] positive electrode active material

[0139] The cathode active material precursor according to the present invention manufactured as described above can be mixed with a lithium raw material and then calcined to manufacture a cathode active material.

[0140] The above lithium raw material can be used without particular limitation as long as it is a compound containing a lithium source, and preferably, at least one selected from the group consisting of lithium carbonate (Li2CO3), lithium hydroxide (LiOHH2O), LiNO3, CH3COOLi, and Li2(COO)2 can be used.

[0141] The above-described positive electrode active material precursor and lithium raw material may be mixed so that the molar ratio of lithium (Li):transition metal (Me) contained in the positive electrode active material precursor is 1:1 to 1.2:1, 1:1 to 1.1:1, or 1:1 to 1.05:1. When the molar ratio of the positive electrode active material precursor and the lithium raw material satisfies the above range, the capacity of the positive electrode active material produced may be excellent, and the sintering may proceed smoothly so that the crystal structure of the positive electrode active material may be stably formed.

[0142]

[0143] Additionally, a doping element-containing material may be additionally mixed during the above firing. The doping element may be at least one selected from the group consisting of Al, Zr, Sr, and Sb, and most preferably, all four of Al, Zr, Sr, and Sb are included.

[0144] The above doping element-containing raw material may be at least one selected from the group consisting of acetate, sulfate, sulfide, hydroxide, oxide or oxyhydroxide containing the above doping element.

[0145] The above-mentioned sintering can be performed at 600°C to 1,000°C, 700°C to 950°C, 800°C to 930°C, 850°C to 920°C, or 870°C to 910°C. The above-mentioned sintering can be performed for 5 to 20 hours, 7 to 17 hours, or 10 to 15 hours, but is not limited thereto. When the above-mentioned sintering is performed for the above-mentioned time and temperature, doping can be sufficiently achieved within the manufactured positive electrode active material.

[0146]

[0147] The positive electrode active material of the present invention may contain nickel in an amount of 80 mol% or more, 82 mol% or more, 85 mol% or more, 87 mol% or more, 90 mol% or more, 92 mol% or more, 93 mol% or more, 94 mol% or more, 95 mol% or more, 96 mol% or more, 99 mol% or less, 98 mol% or less, or 97 mol% or less of all metals excluding lithium. For example, the positive electrode active material of the present invention may contain nickel in an amount of 80 mol% or more, 90 mol% or more, 90 mol% or more, 93 mol% or more, or 95 mol% or more and 99 mol% or less of all metals excluding lithium. When the above range is satisfied, the energy density of the positive electrode active material may be high.

[0148]

[0149] The cathode active material of the present invention may contain cobalt in an amount of 1 mol% or more, 2 mol% or more, 3 mol% or more, 10 mol% or less, 7 mol% or less, 6 mol% or less, 5 mol% or less, 4 mol% or less, or 3 mol% or less of all metals excluding lithium. For example, the cathode active material of the present invention may contain cobalt in an amount of 10 mol% or less, 1 mol% or more and 10 mol% or less, 1 mol% or more and 7 mol% or less, 1 mol% or more and 5 mol% or less, or 2 mol% or more and 4 mol% or less of all metals excluding lithium. When the above range is satisfied, a cost advantage can be achieved by containing a relatively small amount of cobalt, while a certain level or higher of output characteristics can be secured.

[0150]

[0151] The positive electrode active material of the present invention may contain manganese in an amount of 0.1 mol% or more, 0.5 mol% or more, 0.8 mol% or more, 1 mol% or more, 2 mol% or more, 10 mol% or less, 7 mol% or less, 5 mol% or less, 4 mol% or less, 3 mol% or less, 2 mol% or less, or 1 mol% or less of all metals excluding lithium. For example, the positive electrode active material of the present invention may contain manganese in an amount of 10 mol% or less, 0.1 mol% or more and 7 mol% or less, 0.5 mol% or more and 5 mol% or less, or 0.8 mol% or more and 3 mol% or less of all metals excluding lithium. When the above range is satisfied, the energy density of the positive electrode active material can be secured while having excellent structural stability.

[0152]

[0153] The positive electrode active material of the present invention may include one or more doping elements. The doping element may refer to a metal element other than lithium, nickel, cobalt, and manganese contained in the positive electrode active material. The doping element may be one or more selected from the group consisting of Al, Zr, Sr, and Sb, or may include all four of Al, Zr, Sr, and Sb.

[0154] The above doping element may be included in an amount of 5,000 ppm to 15,000 ppm, 7,000 ppm to 13,000 ppm, 9,000 ppm to 12,000 ppm, or 10,000 ppm to 11,000 ppm based on the total weight of the positive electrode active material. When doped in the above amount, doping may be sufficiently uniform, and thermal stability, resistance characteristics, and life characteristics may be excellent.

[0155] The above Al may be included in an amount of 3000 to 9000 ppm, 4000 to 8500 ppm, 5000 to 8000 ppm, or 6000 to 7000 pppm based on the total weight of the positive electrode active material. When the above Al is evenly doped throughout the particle crystal structure, the layered structure is stabilized by even bonding of Al-O, oxygen release is suppressed, and the thermal stability of the positive electrode active material is improved.

[0156] The above Zr may be included in an amount of 1000 to 2000 ppm, 1100 to 1900 ppm, and more preferably 1200 to 1800 ppm, based on the total weight of the positive electrode active material. Since the Zr has a large ionic radius compared to transition metals, when it is evenly doped throughout the particle crystal structure, it forms a large passage through which lithium ions are transferred, thereby improving lithium ion conductivity, thereby having the effect of improving the resistance characteristics of the positive electrode active material.

[0157] The Sr may be included in an amount of 500 to 1500 ppm, 700 to 1300 ppm, or 800 to 1200 ppm based on the total weight of the positive electrode active material. The Sr is doped at a lithium site and a transition metal site, and when the Sr is doped evenly throughout the particle crystal structure, the crystal structure is supported because the ionic radius is large, thereby improving the lifespan and resistance characteristics of a lithium secondary battery including the same. In addition, when the Sr is doped evenly throughout the particle crystal structure, the chemical energy inside the crystal is improved, and the grain boundary energy and surface energy are improved, thereby improving the surface activity. Therefore, the stability and surface activity of the positive electrode active material particles are improved, thereby improving the lifespan and resistance characteristics of a lithium secondary battery including the same.

[0158] The Sb may be included in an amount of 1000 to 2000 ppm, 1200 to 1800 ppm, or 1400 to 1600 ppm based on the total weight of the positive electrode active material. Since the Sb is a polyvalent heavy metal, it is doped at a transition metal site to form a stronger covalent bond with oxygen. When the Sb is evenly doped throughout the particle crystal structure, it can suppress the desorption of oxygen from the lattice structure and improve the phase stability, thereby improving the life characteristics of the positive electrode active material including it. In addition, since the Sb causes the primary particles to be formed small, when the Sb is evenly doped throughout the particle crystal structure, the orientation of the positive electrode active material is improved and the lithium ion migration path is shortened, thereby improving the initial resistance of the positive electrode active material including it.

[0159]

[0160] The positive electrode active material of the present invention may include a lithium nickel-based oxide containing nickel, cobalt, manganese, and the above doping elements.

[0161]

[0162] The positive electrode active material of the present invention may have a composition represented by the following chemical formula 3.

[0163] [Chemical Formula 3] Li a Ni b Co c Mn d M 1 e O2

[0164] In the above chemical formula 3, M 1 The silver is a doping element doped into the positive electrode active material, and may include at least one selected from the group consisting of Al, Zr, Sr, and Sb.

[0165] In the above chemical formula 3, a represents the molar ratio of lithium in the positive electrode active material, and may be 0.8≤a≤1.5, 0.85≤a≤1.2, or 0.9≤a≤1.2, 0.95≤a≤1.1, or 1.0≤a≤1.05.

[0166] In the above chemical formula 3, b represents the molar ratio of nickel to the total molar number of all metals excluding lithium in the positive electrode active material, and may be 0.8≤b≤0.99, 0.85≤b≤0.98, 0.90≤b≤0.98, or 0.95≤b≤0.98.

[0167] In the above chemical formula 3, c represents the molar ratio of cobalt to the total molar number of all metals excluding lithium in the positive electrode active material, and is 0. <c<0.2, 0.01≤c<0.1, 0.02≤c≤0.08 또는 0.02≤c≤0.05일 수 있다.

[0168] In the above chemical formula 3, d represents the molar ratio of manganese to the total molar number of metals excluding lithium in the positive electrode active material, and is 0. <d<0.2, 0.001≤d<0.2, 0.005≤d≤0.1 또는 0.008≤d≤ 0.05일 수 있다.

[0169] In the above chemical formula 3, e is M for the total number of moles of all metals excluding lithium in the positive electrode active material. 10 as it represents the molar ratio <e<0.1, 0.001≤e<0.1, 0.003≤e≤ 0.08 또는 0.005≤e≤ 0.05일 수 있다.

[0170] Preferably, the positive electrode active material of the present invention may have a composition represented by the following chemical formula 3-1.

[0171] [Chemical Formula 3-1] Li a1 Ni b1 Co c1 Mn d1 Al e1 Zr e2 Sr e3 Sb e4 O2

[0172] In the above chemical formula 3-1, a1 represents the molar ratio of lithium in the positive electrode active material, and may be 0.8≤a1≤1.2, 0.85≤a1≤1.15, or 0.9≤a1≤1.1.

[0173] In the above chemical formula 3-1, b1 represents the molar ratio of nickel to the total molar number of all metals excluding lithium in the positive electrode active material, and may be 0.8≤b1≤0.99, 0.85≤b1≤0.98, 0.90≤b1≤0.98, or 0.90≤b1≤0.95.

[0174] In the above chemical formula 3-1, c1 represents the molar ratio of cobalt to the total molar number of all metals excluding lithium in the positive electrode active material, and is 0. <c1<0.2, 0.01≤c1<0.1, 0.02≤c1≤0.08 또는 0.02≤c1≤0.05일 수 있다.

[0175] In the above chemical formula 3-1, d1 represents the molar ratio of manganese to the total number of moles of all metals excluding lithium in the positive electrode active material, and is 0. <d1<0.2, 0.001≤d1<0.2, 0.005≤d1≤ 0.1 또는 0.008≤d1≤ 0.05일 수 있다.

[0176] In the above chemical formula 3-1, e1 represents the doping amount of Al with respect to the total mole number of metals excluding lithium in the positive electrode active material, and may be 0≤e1≤0.05, 0.001≤e1≤0.04, or 0.005≤e1≤0.03.

[0177] In the above chemical formula 3-1, e2 represents the doping amount of Zr with respect to the total mole number of metals excluding lithium in the positive electrode active material, and may be 0≤e2≤0.003, 0.0005≤e2≤0.0025, or 0.001≤e2≤0.002.

[0178] In the above chemical formula 3-1, e3 represents the doping amount of Sr with respect to the total mole number of metals excluding lithium in the positive electrode active material, and may be 0≤e3≤0.003, 0.0005≤e3≤0.0025, or 0.001≤e3≤0.002.

[0179] In the above chemical formula 3-1, e4 represents the doping amount of Sb with respect to the total mole number of metals excluding lithium in the positive electrode active material, and may be 0≤e4≤0.003, 0.0005≤e4≤0.0025, or 0.001≤e4≤0.002.

[0180]

[0181] The above one or more doping elements may have an average value of a first doping uniformity index defined by the following Equation 1 measured for each individual doping element of 16% or less. The above first doping uniformity index is defined as the standard deviation of the doping element content in the entire positive electrode active material compared to the doping element content present in the positive electrode active material, and may function as a parameter indicating the degree to which the doping element is uniformly distributed within the crystal structure. At this time, manganese is suitable as a standard indicating the distribution of the doping element because it serves as a framework that increases structural stability within the crystal structure of the positive electrode active material.

[0182] [Formula 1]

[0183] First doping uniformity index = [N SD ] / [N avg ]

[0184] In the above equation 1, [N SD ] is the standard deviation value of the molar ratio of the individual doping elements to Mn in the entire positive electrode active material, and [N avg ] is the average value of the molar ratio of the individual doping elements to Mn in the entire positive electrode active material.

[0185] Above [N SD ] and [N avg ] The molar ratio of the individual doping elements relative to Mn can be measured by analysis using etching inductively coupled plasma spectroscopy (etching ICP).

[0186] The above one or more doping elements may have an average value of the first doping uniformity index defined by the above formula 1 measured for each individual doping element of 16% or less, 15% or less, 14% or less, 13% or less, 12% or less, 11% or less, 10% or less, or 9.5% or less. When the above range is satisfied, the resistance characteristics and high-temperature life characteristics of the positive electrode active material may be excellent.

[0187] The above one or more doping elements may have an average value of a second doping uniformity index defined by the following equation 2 measured for each individual doping element of 95% to 105%. In the second doping uniformity index, [N SD ] represents the content of the doping element present on the surface of the positive electrode active material. If the doping element remains on the surface of the positive electrode active material or excessively penetrates into the positive electrode active material, the doping element becomes unevenly distributed within the positive electrode active material. Therefore, the average value of the second doping uniformity index can function as a parameter indicating the extent to which the doping element is uniformly distributed within the crystal structure of the positive electrode active material.

[0188] [Formula 2]

[0189] Second doping uniformity index = [N1 / 2 ] / [N avg ]

[0190] In the above equation 2, [N 1 / 2 ] is D from the center of the positive electrode active material. 50 / 2 is the molar ratio of the individual doping elements relative to Mn measured at the position, [N avg ] is the average value of the molar ratio of the individual doping elements to Mn in the entire positive electrode active material.

[0191] Above [N 1 / 2 ] and [N avg ] The molar ratio of the individual doping elements relative to Mn can be measured by analysis using etching inductively coupled plasma spectroscopy (etching ICP).

[0192] At this time, the center of the positive electrode active material may mean the center of a circle having an area matching the area of ​​the positive electrode active material in a cross-sectional image of the positive electrode active material obtained by a scanning electron microscope.

[0193]

[0194] The above one or more doping elements may have an average value of the second doping uniformity index defined by the above formula 2 measured for each individual doping element of 95% or more, 96% or more, 97% or more, 98% or more, 98.5% or more, 99% or more, 99.5% or more, 105% or less, 104% or less, 103% or less, 102% or less, 101% or less, or 100% or less. For example, the above one or more doping elements may have an average value of the second doping uniformity index defined by the above formula 2 measured for each individual doping element of 95% to 105%, 98.5% to 102%, or 99% to 100%. When the above ranges are satisfied, the resistance characteristics and high-temperature life characteristics of the positive electrode active material may be excellent.

[0195]

[0196] The positive electrode active material of the present invention is manufactured from the positive electrode active material precursor of the present invention and has excellent doping uniformity, so it can satisfy the above conditions.

[0197]

[0198] The positive electrode active material of the present invention may have a particle strength of 121 MPa or more, 122 MPa or more, 123 MPa or more, 124 MPa or more, 125 MPa or more, 126 MPa or more, 127 MPa or more, 128 MPa or more, 129 MPa or more, 130 MPa or more, 131 MPa or more, 132 MPa or more, 133 MPa or more, 134 MPa or more, 135 MPa or more, 300 MPa or less, 250 MPa or less, 230 MPa or less, 200 MPa or less, 180 MPa or less, 150 MPa or less, 140 MPa or less, 136 MPa or less, 135 MPa or less, 133 MPa or less, or 131 MPa or less. For example, the positive electrode active material of the present invention may have a particle strength of 121 MPa or more, 121 MPa or more and 300 MPa or less, 122 MPa or more and 200 MPa or less, 123 MPa or more and 150 MPa or less, 125 MPa or more and 135 MPa or less, or 128 MPa or more and 132 MPa or more. Even if the average value of the first doping uniformity index satisfies a specific range or less and doping is uniform, if the particle strength of the positive electrode active material is low, particle breakage and cracking may occur, which may adversely affect the resistance characteristics and high-temperature life characteristics. Accordingly, the positive electrode active material of the present invention can suppress particle breakage during the rolling process by having a particle strength that satisfies the above range, thereby optimally expressing the effect due to the doping uniformity. Accordingly, a battery having excellent resistance characteristics and high-temperature life characteristics can be manufactured.

[0199] In the present invention, particle strength can be defined as compressive fracture strength. Specifically, in the present specification, “particle strength” can be measured by applying pressure in a direction perpendicular to the positive electrode active material using a Surface testing Platform_step 300 device from Anton Paar, measuring the point at which cracks occur in the particles, calculating the particle strength according to the following [Formula B], and then repeating this 10 times to obtain the arithmetic mean value of the particle strength.

[0200] [Formula B]

[0201] Particle strength (unit: MPa) =

[0202] In the above [Formula B], P refers to the pressure applied in the vertical direction to the particle at the point where a crack occurs in the target particle.

[0203] In the above [Formula B], D refers to the diameter of the particle assuming that the target particle is a perfect sphere, and can be calculated as the arithmetic mean value of the horizontal diameter and the vertical diameter of the particle. In this case, the diameter of the particle can be measured from an SEM image of the particle taken using a scanning electron microscope (SEM).

[0204] In the above [Formula B], μ represents Poisson's ratio, and the vertical strain (R) of the particle diameter v ) and horizontal strain (R p ) can be defined as the ratio of

[0205] The vertical strain of the diameter of the above particle (R v ) can be calculated according to the following [Formula B-1].

[0206] [Formula B-1]

[0207] The vertical strain of the particle diameter (R v )=

[0208] In the above [Formula B-1], the D0 means the diameter of the particle in the vertical direction before applying pressure to the particle, and the D v refers to the vertical diameter of the positive electrode active material particle at the point where a crack occurs in the particle.

[0209] The vertical strain of the diameter of the above particle (R p ) can be calculated according to the following [Formula B-2]. However, when calculating the Poisson's ratio, the horizontal deformation of the particle may not be considered, so the horizontal strain (R p ) can be calculated as 1.

[0210] [Formula B-2]

[0211] Horizontal strain of particle diameter (R v )=

[0212] In the above [Formula B-2], D1 means the horizontal diameter of the particle before applying pressure to the particle, and D p refers to the horizontal diameter of the particle at the point where a crack occurs in the particle.

[0213]

[0214] The cathode active material of the present invention may have a crystallite size of (003) plane measured by X-ray diffraction analysis of 200 nm or less, 150 nm or less, 130 nm or less, 120 nm or less, 113 nm or less, 110 nm or less, 108 nm or less, 50 nm or more, 60 nm or more, 70 nm or more, 80 nm or more, 85 nm or more, 88 nm or more, 90 nm or more, 95 nm or more, 98 nm or more, 100 nm or more, 103 nm or more, 105 nm or more, 107 nm or more, or 108 nm or more. The above ranges can be combined without limitation. When the above ranges are satisfied, the thermodynamically stable and electrochemically unstable (003) plane grows to an appropriate degree, thereby optimizing the effect of improving lithium ion mobility and reducing side reactions with the electrolyte. Accordingly, the resistance and life characteristics of the positive electrode active material can be excellent.

[0215] In the present invention, the “crystallite size of the (003) plane” means the average value of the size of the (003) plane measured by X-ray diffraction analysis (XRD), and more specifically, it can be obtained through the Rietveld method using XRD data. Specifically, the crystallite size of the (003) plane is obtained by placing a sample into the central groove of a general powder holder, smoothing the surface of the sample using a slide glass while making the height the same as the edge of the holder, and then using an X-ray diffractometer (Bruker, D8 Endeavor) to measure the XRD data (2θ=6°~125°, Step size=0.02°, total scan time: 33 min) and analyzing the XRD data through the Fundamental Parameter Approach built into Bruker’s TOPAS program based on the Rietveld method.

[0216]

[0217] The positive electrode active material of the present invention may have a pore area ratio of 0.02 to 0.1, 0.02 to 0.08, 0.025 to 0.07, 0.03 to 0.06, or 0.04 to 0.05. When the above range is satisfied, the electrolyte may be sufficiently impregnated into the positive electrode active material, thereby exhibiting excellent resistance characteristics and lifespan characteristics.

[0218] The positive electrode active material of the present invention may have a sphericity of 0.85 or more, 0.90 or more, 0.91 or more, 0.92 or more, 0.93 or more, 0.94 or more, or 0.95 or more. When the above range is satisfied, the energy density increases, the movement path of lithium ions within the positive electrode is smoothly secured, and the structural stability may be excellent.

[0219]

[0220] Average particle diameter D of the positive electrode active material of the present invention 50 The average particle size of the positive electrode active material of the present invention may be 7 ㎛ or more, 8 ㎛ or more, 10 ㎛ or more, 11 ㎛ or more, 12 ㎛ or more, 13 ㎛ or more, 15 ㎛ or less, or 14 ㎛ or less. For example, the average particle size D of the positive electrode active material of the present invention 50 It may be 7㎛ or more and 15㎛ or less, 10㎛ or more and 14㎛ or less, or 12㎛ or more and 14㎛ or less.

[0221]

[0222] anode

[0223] The positive electrode according to the present invention comprises the positive electrode active material of the present invention described above. Specifically, the positive electrode comprises a positive electrode current collector, and a positive electrode active material layer formed on the positive electrode current collector. The positive electrode active material layer may include a conductive material and a binder along with the positive electrode active material of the present invention. Since the positive electrode active material has been described above, a detailed description thereof will be omitted, and only the remaining components will be described in detail below.

[0224]

[0225] The positive electrode current collector of the present invention may include a highly conductive metal, and is not particularly limited as long as it is a metal to which the positive electrode active material layer can be easily adhered, but is not reactive in the voltage range of the battery. The positive electrode current collector may be made of, for example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, etc. 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 current collector to increase the adhesion of the positive electrode active material. For example, the positive electrode current collector may 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.

[0226]

[0227] The positive electrode active material included in the positive electrode active material layer of the present invention may be included in an amount of 95 wt% to 100 wt%, preferably 98 wt% to 100 wt%, and more preferably 99 wt% to 100 wt%, based on the weight of the total positive electrode active material included in the positive electrode active material layer. Most preferably, 100% of the positive electrode active material in the form of a single particle or pseudo-single particle may be included alone. When the content of the positive electrode active material of the present invention satisfies the above range, sufficient life characteristics can be obtained. When the positive electrode active material in the form of a secondary particle is included in an amount exceeding 5 wt% of the total positive electrode active material, the side reaction with the electrolyte increases due to fine particles generated from the secondary particles during electrode manufacture and charge / discharge, thereby reducing the effect of suppressing gas generation.

[0228]

[0229] The positive electrode active material layer of the present invention may optionally include a conductive material and a binder, together with the positive electrode active material, as needed.

[0230] At this time, the positive electrode active material may be included in an amount of 80 to 99 wt%, more specifically 85 to 98.5 wt%, based on the total weight of the positive electrode active material layer, and when included in the above content range, it may exhibit excellent capacity characteristics.

[0231]

[0232] The conductive material is used to provide conductivity to the electrode, and in the battery to be formed, as long as it does not cause a chemical change and has electronic conductivity, it can be used without any special restrictions. Specific examples include graphite such as natural graphite or artificial graphite; carbon-based materials such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, and carbon fiber; metal powders or metal fibers such as copper, nickel, aluminum, and silver; conductive tubes such as carbon nanotubes; 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 of these may be used alone or a mixture of two or more may be used. The conductive material may be included in an amount of 0.1 to 15 wt% based on the total weight of the positive electrode active material layer.

[0233]

[0234] The above binder serves to improve the adhesion between positive electrode active material particles and the adhesion between the positive electrode active material and the current collector. Specific examples include polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylalcohol, polyacrylonitrile, polymethyl methacrylate, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene butadiene rubber (SBR), fluoroelastomer, polyacrylic acid, and polymers in which hydrogens of these are substituted with Li, Na, or Ca, or various copolymers thereof, and one of these may be used alone or a mixture of two or more thereof. The above binder may be included in an amount of 0.1 to 15 wt% based on the total weight of the positive electrode active material layer.

[0235]

[0236] The above positive electrode can be manufactured according to a conventional positive electrode manufacturing method. Specifically, a positive electrode active material can be prepared, and optionally, a binder, a conductive agent, and a dispersant can be dissolved or dispersed in a solvent to prepare a composition for forming a positive electrode active material layer. The composition for forming a positive electrode active material layer can be applied, dried, and rolled to manufacture the positive electrode.

[0237] The solvent may be a solvent generally used in the relevant technical field, such as dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), dimethyl formamide (DMF), 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, binder, and dispersant in consideration of 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.

[0238]

[0239] Additionally, in another method, 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.

[0240]

[0241] electrochemical devices

[0242] Next, an electrochemical device according to the present invention will be described. The electrochemical device according to the present invention includes the anode of the present invention described above. Specifically, the electrochemical device may be a battery, a capacitor, or the like, and more specifically, a lithium secondary battery.

[0243] The lithium secondary battery specifically includes a positive electrode, a negative electrode positioned opposite the positive electrode, and a separator and electrolyte interposed between the positive electrode and the negative electrode. Since the positive electrode is the same as described above, a detailed description thereof will be omitted, and only the remaining components will be specifically described below.

[0244] In addition, the lithium secondary battery may optionally further include a battery container that houses the electrode assembly of the positive electrode, the negative electrode, and the separator, and a sealing member that seals the battery container.

[0245]

[0246] In the above lithium secondary battery, the negative electrode includes a negative electrode current collector and a negative electrode active material layer positioned on the negative electrode current collector.

[0247] 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.

[0248]

[0249] The above negative electrode active material layer optionally includes a binder and a conductive material together with the negative electrode active material.

[0250] As the negative electrode active material, a compound capable of reversible intercalation and deintercalation of lithium may 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 alloy, Sn alloy, or Al alloy; SiO β(0 < β < 2), metal oxides capable of doping and dedoping lithium, such as SnO2, vanadium oxide, and lithium vanadium oxide; or composites containing the above 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 fibers, 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.

[0251] The above negative electrode active material may be included in an amount of 80 wt% to 99 wt% based on the total weight of the negative electrode active material layer.

[0252]

[0253] The above binder is a component that assists in bonding between the conductive material, the active material, and the current collector, and is typically added in an amount of 0.1 wt% to 10 wt% based on the total weight of the negative electrode active material layer. Examples of such binders include polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene-butadiene rubber, nitrile-butadiene rubber, fluororubber, and various copolymers thereof.

[0254] The conductive agent is a component for further improving the conductivity of the negative electrode active material, and may be added in an amount of 10 wt% or less, preferably 5 wt% or less, based on the total weight of the negative electrode active material layer. The conductive agent is not particularly limited as long as it has conductivity and does not cause a chemical change in the battery, and examples thereof include graphite such as natural graphite or artificial graphite; carbon black such as acetylene black, Ketjen black, channel black, furnace black, lamp black, and thermal black; conductive fibers such as carbon fiber or metal fiber; fluorinated carbon; metal powder such as aluminum or nickel powder; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives.

[0255]

[0256] The negative electrode active material layer may be manufactured by applying and drying a composition for forming a negative electrode active material layer prepared by dissolving or dispersing a negative electrode active material, and optionally a binder and a conductive material in a solvent, on a negative electrode current collector, or by casting the composition for forming a negative electrode active material layer on a separate support, and then laminating the film obtained by peeling it off from the support on a negative electrode current collector.

[0257]

[0258] Meanwhile, in the lithium secondary battery, the separator separates the negative electrode and the positive electrode and provides a passage for lithium ions to move. Any separator commonly used in lithium secondary batteries can be used without any particular restrictions, and in particular, one having low resistance to ion movement of the electrolyte and excellent electrolyte moisture retention 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 may be used to secure heat resistance or mechanical strength, and may optionally be used in a single-layer or multi-layer structure.

[0259]

[0260] In addition, the electrolyte used in the present invention may include, but is not limited to, an organic liquid electrolyte, an inorganic liquid electrolyte, a solid polymer electrolyte, a gel-type polymer electrolyte, a solid inorganic electrolyte, a molten inorganic electrolyte, etc. that can be used in the manufacture of a lithium secondary battery.

[0261] Specifically, the electrolyte may include an organic solvent and a lithium salt.

[0262] 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 (where R represents a linear, branched, or cyclic hydrocarbon group having 2 to 20 carbon atoms 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.

[0263]

[0264] The above lithium salt can be used without any special limitation as long as it is a compound that can provide lithium ions used in a lithium secondary battery. Specifically, the anion of the above lithium salt is F - , Cl - , Br - , I - , NO3 - , N(CN)2 - , BF4 - , CF3CF2SO3 - , (CF3SO2)2N - , (FSO2)2N - , CF3CF2(CF3)2CO - , (CF3SO2)2CH - , (SF5)3C - , (CF3SO2)3C - , CF3(CF2)7SO3 - , CF3CO2 - , CH3CO2 - , SCN - and (CF3CF2SO2)2N - At least one selected from the group consisting of, and the lithium salt is LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAl04, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2) 2. LiCl, LiI, or LiB(C2O4)2 can be used. It is recommended that the concentration of the lithium salt be 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.

[0265]

[0266] 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, hexaphosphoric 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.

[0267]

[0268] As described above, the electrochemical device including the positive electrode according to the present invention stably exhibits excellent discharge capacity, output characteristics, and life characteristics, 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).

[0269] Accordingly, according to another embodiment of the present invention, a battery module including the electrochemical device as a unit cell and a battery pack including the same are provided.

[0270] 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.

[0271] There is no particular limitation on the external shape of the electrochemical device of the present invention, but it may be a cylindrical shape using a can, a square shape, a pouch shape, or a coin shape.

[0272] The electrochemical device according to the present invention can be used not only in a battery cell used as a power source for a small device, but can also be preferably used as a unit battery in a medium- to large-sized battery module including a plurality of battery cells.

[0273] Examples of the above medium and large devices include, but are not limited to, electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, and power storage systems.

[0274]

[0275] 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.

[0276]

[0277] Examples and Comparative Examples

[0278] Example 1

[0279] (Step 1) NiSO4, CoSO4, and MnSO4 were dissolved in ion-exchanged water so that the molar ratio of nickel: cobalt: manganese was 96:3:1 to prepare a transition metal-containing solution having a concentration of 2 mol / L. A 1 L batch reactor was filled with distilled water, 7 wt% ammonia water, and 25 wt% sodium hydroxide aqueous solution, and the reactor was stirred at 50°C for 20 minutes.

[0280] After that, the above transition metal-containing solution was quantitatively injected at a supply rate of 25 L / h and ammonia water at a supply rate of 2.5 L / h for 50 hours, and the pH was lowered from 11.9 to 11.7 over 30 minutes using a pH peristaltic pump. An oxidation process was performed by injecting 2 L / h of oxygen. After 50 hours, the supply rate of the ammonia water was increased to 3 L / h.

[0281] When the volume of the reaction solution reached 80%, the supply of the reactants was stopped, stirring was stopped to allow the precursor intermediate product to settle, the supernatant was removed, and the reaction was restarted. This process was repeated about 5 times to obtain the average particle diameter D of the positive electrode active material precursor nucleus (seed) particles. 50 When this reached 3.8㎛, the nucleation reaction of the positive electrode active material precursor was terminated. The total reaction time was 70 hours.

[0282] (Step 2) After the seed reaction of the positive electrode active material precursor was completed, the main reaction was conducted. During the main reaction, the synthesis temperature was 70°C, the transition metal-containing solution was supplied at 70 L / h for 1 hour, increased to 75 L / h for 9 hours, and then fixed at 75 L / h. Ammonia water was injected at a supply rate of 4 L / h, and the pH was maintained at 11.00 to 11.05. The main reaction was conducted in a nitrogen atmosphere with oxygen removed.

[0283] After separating the precursor particles from the reaction solution, impurities were removed through washing, dried in a 150°C drying oven for 15 hours, and then sieved to prepare a positive electrode active material precursor.

[0284]

[0285] Example 2

[0286] (Step 1) A positive electrode active material precursor was manufactured in the same manner as Example 1, except that a transition metal-containing solution prepared at a concentration of 2 mol / L by dissolving NiSO4, CoSO4, and MnSO4 in ion-exchanged water so that the molar ratio of nickel: cobalt: manganese was 97:0.5:2.5 was used.

[0287] Comparative Example 1

[0288] (Step 1) NiSO4, CoSO4, and MnSO4 were dissolved in ion-exchanged water so that the molar ratio of nickel: cobalt: manganese was 96:3:1 to prepare a transition metal-containing solution having a concentration of 2 mol / L. A 1 L batch reactor was filled with distilled water, 9 wt% ammonia water, and 25 wt% sodium hydroxide aqueous solution, and the reactor was stirred at 50°C for 20 minutes.

[0289] After that, the above transition metal-containing solution was quantitatively injected at a supply rate of 25 L / h and ammonia water at a supply rate of 2.5 L / h for 50 hours, and the pH was lowered from 12 to 11.8 over 30 minutes using a pH peristaltic pump. An oxidation process was performed by injecting 2 L / h of oxygen. After 50 hours, the supply rate of the ammonia water was increased to 3 L / h.

[0290] When the volume of the reaction solution reached 80%, the supply of the reactants was stopped, stirring was stopped to allow the precursor intermediate product to settle, the supernatant was removed, and the reaction was restarted. This process was repeated about 5 times to obtain the average particle diameter D of the positive electrode active material precursor nucleus (seed) particles. 50 When this reached 3.8㎛, the nucleation reaction of the positive electrode active material precursor was terminated. The total reaction time was 70 hours.

[0291] (Step 2) After the nucleation reaction was completed, the main reaction was conducted. During the main reaction, the synthesis temperature was 60°C, and the transition metal-containing solution was supplied at 70 L / h for 2 hours, then at 75 L / h for 20 hours, and then maintained at 75 L / h. Ammonia water was injected at a supply rate of 4 L / h, and the pH was maintained at 11.00 to 11.05. The main reaction was conducted in an oxidizing atmosphere by supplying 4 L / h of oxygen.

[0292] After separating the precursor particles from the reaction solution, impurities were removed through washing, dried in a 150°C drying oven for 15 hours, and then sieved to prepare a positive electrode active material precursor.

[0293]

[0294] Comparative Example 2

[0295] (Step 1) was carried out in the same manner as (Step 1) described in Example 1, and (Step 2) was carried out in the same manner as in Comparative Example 1 to manufacture a positive electrode active material precursor.

[0296]

[0297] Comparative Example 3

[0298] (Step 2) The transition metal-containing solution was supplied at 70 L / h for 1 hour, increased to 75 L / h for 9 hours, and then fixed at 75 L / h. When the target particle size was reached, stirring was stopped to allow the precursor intermediate product to settle, and the supernatant was removed and the reaction was restarted. This process was repeated about 5 times to obtain the target D of the precursor particles. 50 A positive electrode active material precursor was manufactured in the same manner as in Comparative Example 1, except that the reaction was terminated when reaching .

[0299]

[0300] Comparative Example 4

[0301] (Step 2) A cathode active material precursor was manufactured in the same manner as in Comparative Example 1, except that the transition metal-containing solution was supplied at 70 L / h for 1 hour, increased to 75 L / h for 5 hours, and then fixed at 75 L / h.

[0302]

[0303] Experimental Example 1: Evaluation of Positive Electrode Active Material Precursor

[0304] The sphericity, pore area ratio, average particle diameter D50, and (001) plane crystallite size of the positive electrode active material precursors of Examples 1 to 2 and Comparative Examples 1 to 4 were evaluated and shown in Table 1 below. The specific measurement method is as follows.

[0305] (1) Spherical shape

[0306] The positive electrode active material precursors of Examples 1 to 2 and Comparative Examples 1 to 4 were mixed with carbon black, PVDF binder, and N-methylpyrrolidone at a weight ratio of 95:2:3 to prepare a slurry, and the slurry was applied to one side of a 20 μm thick aluminum current collector. The applied slurry was dried to prepare an electrode, and the electrode was dried under Ar + Using ion beams The cross-section is cut using an ion milling device (manufacturer: Hitachi, product name: IM5000, acceleration voltage: 6 kV, ion beam current: 400 μA). The cross-section image of the electrode is obtained by scanning electron microscopy of the cut electrode cross-section. Afterwards, the minimum particle diameter (D) of the particle is determined using an image analysis program for the cross-section image of the electrode. min , short diameter), maximum diameter (D max , the diameter) and area (Area) were derived, and the sphericity of the positive electrode active material precursor was derived from the arithmetic mean value calculated using the above formula A.

[0307] [Formula A] Roundness = (4 x Area) / (π x (Dmax ) 2 )

[0308] (2) Pore area ratio (PAR)

[0309] Each of the positive electrode active material precursors of Examples 1 to 3 and Comparative Examples 1 to 5 was mixed with carbon black, PVDF binder, and N-methylpyrrolidone at a weight ratio of 95:2:3 to prepare a positive electrode slurry, and the positive electrode slurry was applied to one surface of an aluminum current collector having a thickness of 20 μm. The applied positive electrode mixture layer was dried at 130°C to prepare an electrode, and the electrode was prepared under Ar + Using ion beams The cross-section is cut using an ion milling device (manufacturer: Hitachi, product name: IM5000, acceleration voltage: 6 kV, ion beam current: 400 μA). The cross-section of the cut electrode is photographed using a scanning electron microscope (SEM) to obtain a cross-sectional image of the electrode active material layer. Thereafter, for the cross-sectional image of the electrode active material layer, the voids among the positive electrode active material precursor particles are indicated as shaded parts and the dense parts among the positive electrode active material precursor particles are indicated as white parts using image analysis software WinRoof 6.1.1. The ratio of [shaded part / (shaded part + white part)] is calculated for each of 100 or more precursor particles among the measured positive electrode active material precursors, and the pore area ratio (PAR) is obtained by calculating the arithmetic average value thereof.

[0310] (3) Average particle diameter D 50

[0311] Each of the positive electrode active material precursors manufactured in Examples 1 to 2 and Comparative Examples 1 to 4 was dispersed in a dispersion medium, and then introduced into a laser diffraction particle size measuring device (Microtrac MT 3000) and irradiated with ultrasonic waves of about 28 kHz at an output of 60 W. Then, a volume-cumulative particle size distribution graph was obtained, and the particle size corresponding to 50% of the volume-cumulative amount was obtained.

[0312] (4) (001) surface decision size

[0313] Each of the positive electrode active material precursors manufactured in Examples 1 to 2 and Comparative Examples 1 to 4 was placed into the central groove of a general powder holder, and the surface of the sample was smoothed using a slide glass, and the height was made equal to the edge of the holder. After that, XRD data were measured (2θ=15°~90°, Step size=0.02°, total scan time: 20 min) using an X-ray diffractometer (Bruker, D8 Endeavor), and the average crystallite size of the (001) plane was obtained by analyzing the XRD data through the Fundamental Parameter Approach built into Bruker's TOPAS program based on the Rietveld method.

[0314] Spherical pore area ratio D 50 [㎛](001) Surface Crystal Size [nm] Example 10.920.07512.518.9 Example 20.930.08112.117.7 Comparative Example 10.780.02112.112.9 Comparative Example 20.880.03513.013.4 Comparative Example 30.820.07312.014.3 Comparative Example 40.910.10612.417.9

[0315] <Manufacturing of positive electrode active materials>

[0316] Each of the positive electrode active material precursors of Examples 1 to 2 and Comparative Examples 1 to 4 and LiOH were added so that the molar ratio of (Ni+Co+Mn) : Li was 1:1.075, and additionally, Al2(SO4)3·18H2O, ZrO2, Sb2O3, and Sr(OH)2·8H2O were added in amounts such that Zr was 1500 ppm, Al 6500 ppm, Sr 1000 ppm, and Sb 1500 ppm based on the total weight of the lithium composite transition metal oxide finally obtained. After mixing these, they were mixed at 400 rpm for 20 minutes and then calcined at 890°C for 12 hours in an oxygen atmosphere to manufacture positive electrode active materials manufactured using the positive electrode active material precursors of Examples 1 to 2 and Comparative Examples 1 to 4, respectively.

[0317]

[0318] Experimental Example 2 - Analysis of the uniformity of positive electrode active material doping

[0319] The content of individual doping elements for each manufactured positive electrode active material was analyzed by etching inductively coupled plasma spectroscopy (etching ICP). Specifically, the positive electrode active material was immersed in deionized water at 25°C and then sonicated with an ultrasonicator for 30 minutes to pretreat it, and then analyzed by inductively coupled plasma optical emission spectroscopy (ICP-OES) to measure the content of each doping element according to the distance from the center of the positive electrode active material. Specifically, while applying plasma to each positive electrode active material to etch it, the content of each doping element at each position was measured after 3, 5, 10, 20, 30, 40, 50, 60, 120, 180, 240, 300, and 360 minutes, and the molar ratio of the doping element to Mn was calculated. This is shown in Figures 1 to 4 below.

[0320] Based on the molar ratio values ​​of each doping element to Mn at each point obtained from the above ICP data, (1) the first doping uniformity index defined by the following Equation 1 was measured for each doping element, and the arithmetic mean value of the measured first doping uniformity indices was calculated to determine whether the value was 16% or less, and (2) the second doping uniformity index defined by the following Equation 2 was measured for each doping element, and the arithmetic mean value of the measured second doping uniformity indices was calculated to determine whether the value was 95% to 105%, and the doping uniformity was evaluated based on this.

[0321] [Formula 1] First doping uniformity index = [N SD ] / [N avg ]

[0322] In the above equation 1, [N SD ] is the standard deviation value of the molar ratio of the individual doping elements to Mn in the entire positive electrode active material, and [N avg ] is the average value of the molar ratio of the individual doping elements to Mn in the entire positive electrode active material.

[0323] [Formula 2] Second doping uniformity index = [N 1 / 2 ] / [N avg ]

[0324] In the above equation 2, [N 1 / 2 ] is D from the center of the positive electrode active material. 50 / 2 is the molar ratio of the individual doping elements relative to Mn measured at the position, [N avg ] is the average value of the molar ratio of the individual doping elements to Mn in the entire positive electrode active material.

[0325] Cases satisfying both conditions (1) and (2) above were evaluated as excellent, cases satisfying only one of conditions (1) and (2) above were evaluated as medium, and cases not satisfying both conditions (1) and (2) above were evaluated as poor. The results are shown in Table 2 below.

[0326] (1) Average value of the first doping uniformity index (2) Average value of the second doping uniformity index Doping uniformity Example 199.95% 9.05% Lower Example 299.77% 9.51% Upper Comparative Example 194.275% 19.275% Lower Comparative Example 2102.45% 16.225% Middle Comparative Example 3100.275% 18.85% Middle Comparative Example 4100.88% 6.42% Upper

[0327] As can be seen in Table 2, it was confirmed that the doping uniformity of the positive electrode active materials manufactured from the positive electrode active material precursors of Examples 1 to 2 was superior to that of the positive electrode active materials manufactured from the positive electrode active material precursors of Comparative Examples 1 to 4.

[0328] Experimental Example 3 - Evaluation of the properties of positive electrode active materials

[0329] For each manufactured positive electrode active material, sphericity, pore area ratio, and average particle diameter D 50 , (003) surface crystal size and particle strength were analyzed and shown in Table 3.

[0330] (1) Spherical shape

[0331] The positive electrode active materials of Examples 1 to 2 and Comparative Examples 1 to 4 were mixed with carbon black, PVDF binder, and N-methylpyrrolidone at a weight ratio of 95:2:3 to prepare a slurry, and the slurry was applied to one side of an aluminum current collector having a thickness of 20 μm. The applied slurry was dried to prepare an electrode, and the electrode was dried under Ar + Using ion beams The cross-section is cut using an ion milling device (manufacturer: Hitachi, product name: IM5000, acceleration voltage: 6 kV, ion beam current: 400 μA). The cross-section image of the electrode is obtained by scanning electron microscopy of the cut electrode cross-section. Afterwards, the minimum particle diameter (D) of the particle is determined using an image analysis program for the cross-section image of the electrode. min , short diameter), maximum diameter (D max, the diameter) and area (Area) were derived, and the sphericity of the positive electrode active material was derived from the arithmetic mean value calculated using the above formula A.

[0332] [Formula A] Roundness = (4 x Area) / (π x (D max ) 2 )

[0333]

[0334] (2) Pore area ratio

[0335] Each manufactured positive electrode active material is mixed with carbon black, PVDF binder, and N-methylpyrrolidone at a weight ratio of 95:2:3 to manufacture a positive electrode slurry, and the positive electrode slurry is applied to one side of a 20 μm thick aluminum current collector. The applied positive electrode mixture layer is dried at 130°C to manufacture an electrode, and the electrode is dried under Ar + Using ion beams The cross-section is cut using an ion milling device (manufacturer: Hitachi, product name: IM5000, acceleration voltage: 6 kV, ion beam current: 400 μA). The cross-section of the cut electrode is photographed using a scanning electron microscope (SEM) to obtain a cross-sectional image of the electrode active material layer. Thereafter, for the cross-sectional image of the electrode active material layer, the voids among the positive electrode active material particles are indicated as shaded areas and the dense areas among the positive electrode active material particles are indicated as white areas using image analysis software WinRoof 6.1.1. The ratio of [shaded area / (shaded area + white area)] is calculated for each of 100 or more positive electrode active material particles among the measured positive electrode active materials, and the pore area ratio (PAR) is obtained by calculating the arithmetic average value thereof.

[0336] (3) Average particle diameter D 50

[0337] After the manufactured positive electrode active material was dispersed in a dispersion medium, it was introduced into a laser diffraction particle size measuring device (Microtrac MT 3000) and irradiated with ultrasonic waves of approximately 28 kHz at an output of 60 W. Then, a volume-cumulative particle size distribution graph was obtained, and the particle size corresponding to 50% of the volume-cumulative amount was obtained.

[0338] (4) (003) Cotton decision size

[0339] Each manufactured positive electrode active material was placed in the central groove of a general powder holder, and the surface of the sample was smoothed using a slide glass, and the height was made the same as the edge of the holder. Then, XRD data was measured (2θ=6°~125°, Step size=0.02°, total scan time: 33 min) using an X-ray diffractometer (Bruker, D8 Endeavor). The average crystal grain size of the (003) plane was obtained by analyzing the XRD data using the Fundamental Parameter Approach built into Bruker's TOPAS program based on the Rietveld method.

[0340] (5) Particle strength

[0341] Using the Surface testing Platform_step 300 equipment of Anton Paar, the point at which cracks occur in the particles is measured by applying pressure in a direction perpendicular to the target positive electrode active material, and the particle strength is calculated according to the following [Formula B]. This is repeated 10 times, and the arithmetic mean value of the obtained particle strength is measured.

[0342] [Formula B]

[0343] Particle strength (unit: MPa) =

[0344] In the above [Formula B], P is the pressure applied in the vertical direction to the particle at the point where a crack occurs in the positive electrode active material particle.

[0345] In the above [Formula B], D represents the diameter of the particle assuming that the target particle is a perfect sphere, and is calculated as the arithmetic mean value of the horizontal diameter and the vertical diameter of the particle. In this case, the diameter of the particle was measured from an SEM image of the particle taken using a scanning electron microscope (SEM).

[0346] μ stands for Poisson's ratio, and the vertical strain (R) of the particle diameter v ) and horizontal strain (R p ) is defined as the ratio of the vertical strain of the diameter of the particle (R v ) was calculated according to the following [Formula B-1].

[0347] [Formula B-1]

[0348] The vertical strain of the particle diameter (R v )=

[0349] In the above [Formula B-1], the D0 means the diameter of the particle in the vertical direction before applying pressure to the particle, and the D v refers to the vertical diameter of the positive electrode active material particle at the point where a crack occurs in the particle.

[0350] The vertical strain of the diameter of the above particle (R p ) can be calculated according to the following [Formula B-2]. However, when calculating the Poisson's ratio, the horizontal deformation of the particle may not be considered, so the horizontal strain (R p ) can be calculated as 1.

[0351] [Formula B-2]

[0352] Horizontal strain of particle diameter (R v )=

[0353] In the above [Formula B-2], D1 means the horizontal diameter of the particle before applying pressure to the particle, and Dp refers to the horizontal diameter of the particle at the point where a crack occurs in the particle.

[0354] Spherical pore area ratio D 50 [㎛]Crystallite size [nm]Particle strength [MPa]Example 10.940.04313.4108130.4Example 20.950.04511.3113135.2Comparative example 10.810.01213.288118.4Comparative example 20.900.01913.395125.1Comparative example 30.850.03913.298120.5Comparative example 40.890.06911.5106120.9

[0355] <Lithium secondary battery manufacturing>

[0356] As described above, a cathode slurry was prepared by mixing the cathode active material prepared from the cathode active material precursors prepared in Examples 1 to 2 and Comparative Examples 1 to 4, carbon black as a conductive material, and polyvinylidene fluoride (PVDF) as a binder in a weight ratio of 95:2.5:2.5 in N-methyl-2-pyrrolidone (NMP). The cathode slurry was applied to one surface of an aluminum current collector, dried at 130°C, and then rolled to prepare a cathode.

[0357] A negative electrode slurry was prepared by mixing artificial graphite as a negative active material, carbon black as a conductive material, and SBR-CMC as a binder in a weight ratio of 95:3.5:1.5, and the slurry was applied to one side of a copper current collector, dried at 100°C, and then rolled to produce a negative electrode.

[0358] An electrode assembly was manufactured by interposing a separator between the positive and negative electrodes, and then positioning it inside a battery case, and then injecting an electrolyte into the case to manufacture a lithium secondary battery. The electrolyte was an electrolyte in which 1 M LiPF6 was dissolved in a mixed organic solvent of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a volume ratio of 1:2.

[0359]

[0360] Experimental Example 4 - Resistance Characteristics

[0361] Each lithium secondary battery manufactured above was charged at room temperature in CC-CV mode at 0.2C to 4.25V and discharged to 2.5V at the same C-rate. The battery was then charged again at 0.2C to 4.25V, discharged to 50% of the discharged capacity, and pulsed at 1C for 10 seconds at SOC 90 to measure the resistance. The measurement results are shown in Table 2.

[0362]

[0363] Experimental Example 5 - High Temperature Life Characteristics

[0364] For each lithium secondary battery manufactured above, 100 charge-discharge cycles were performed, in which one cycle was charged at 0.1C in CC-CV mode at 45°C to 4.2V and discharged to 2.5V at a constant current of 2C, and then the capacity retention rate was measured to evaluate the high-temperature life characteristics. The measurement results are shown in Table 4.

[0365] SOC 50% Resistance (Ω) Capacity Retention Rate (%) Example 19.193 Example 29.591 Comparative Example 110.587 Comparative Example 29.889 Comparative Example 39.889 Comparative Example 410.189

[0366] As can be seen in Table 4, it was confirmed that the resistance characteristics and life characteristics of the lithium secondary batteries including the positive electrode active materials manufactured from the positive electrode active material precursors of Examples 1 to 2 were superior to those of the lithium secondary batteries including the positive electrode active materials manufactured from the positive electrode active material precursors of Comparative Examples 1 to 4.

Claims

Contains nickel in an amount of 80 mol% or more of all metals excluding lithium, Contains one or more doping elements, wherein the one or more doping elements have an average value of a first doping uniformity index defined by the following formula 1 measured for each individual doping element of 16% or less, A cathode active material having a particle strength of 121 MPa or more. [Formula 1] First doping uniformity index = [N SD ] / [N avg ] In the above equation 1, [N SD ] is the standard deviation value of the molar ratio of the individual doping elements to Mn in the entire positive electrode active material, [N avg ] is the average value of the molar ratio of the individual doping elements to Mn in the entire positive electrode active material. In the first paragraph, A cathode active material, wherein the above one or more doping elements have an average value of the first doping uniformity index defined by the above formula 1 measured for each individual doping element of 9.5% or less. In the first paragraph, A cathode active material, wherein the above one or more doping elements have an average value of a second doping uniformity index defined by the following equation 2 measured for each individual doping element of 95% to 105%. [Formula 2] Second doping uniformity index = [N 1 / 2 ] / [N avg ] In the above equation 2, [N 1 / 2 ] is D from the center of the positive electrode active material. 50 / 2 is the molar ratio of the individual doping elements relative to Mn measured at the position, [N avg ] is the average value of the molar ratio of the individual doping elements to Mn in the entire positive electrode active material. In the first paragraph, The above positive electrode active material is a positive electrode active material having a particle strength of 125 MPa or more and 135 MPa or less. In the first paragraph, A cathode active material having a crystallite size of the (003) plane of 107 nm or more as measured by X-ray diffraction analysis (XRD). In the first paragraph, The above positive electrode active material has an average particle diameter D 50 A positive electrode active material having a size of 7㎛ or more and 15㎛ or less. In the first paragraph, The above positive electrode active material is a positive electrode active material having a sphericity of 0.91 or more. In the first paragraph, The above positive electrode active material is a positive electrode active material having a pore area ratio of 0.02 or more and 0.10 or less. In the first paragraph, A cathode active material, wherein the above doping element is contained in an amount of 5,000 ppm to 15,000 ppm based on the total weight of the cathode active material. A positive electrode comprising the positive electrode active material of claim 1. An electrochemical device comprising the anode of claim 10. Contains nickel in an amount of 80 mol% or more among the total metal, The sphericity is 0.83 or higher, The pore area ratio (PAR) is 0.04 or more and 0.10 or less, Positive electrode active material precursor. In Article 12, A positive electrode active material precursor having a pore area ratio of 0.05 or more and 0.08 or less. In Article 12, A positive electrode active material precursor having a sphericity of 0.85 or more and 0.92 or less. In Article 12, Average particle diameter D of the positive electrode active material precursor 50 A positive electrode active material precursor having a size of 7㎛ or more and 15㎛ or less. In Article 12, A cathode active material precursor having a crystallite size of 15 nm or more on the (001) plane as measured by X-ray diffraction analysis (XRD). In Article 12, A cathode active material precursor containing cobalt in an amount of 1 mol% or more and 10 mol% or less among all metals.

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