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

Abstract

The present invention relates to a positive electrode active material that can improve the performance of a lithium secondary battery, and more particularly to a positive electrode active material comprising a single-particle type first lithium composite transition metal oxide and, selectively, a single-particle type second lithium composite transition metal oxide, wherein the single-particle type first lithium composite transition metal oxide consists of 30 or fewer disk-shaped primary particles. The primary particles of type () are observed from an SEM image of the surface or cross-section of the positive electrode active material, and when two boundary lines of primary particles existing within an angle of 45° or less with respect to the major axis direction are drawn, and a virtual tangent line with the most contacts is drawn for each of these, and when one virtual line is drawn crossing the two tangent lines, the ipsilateral interior angle is 150° or more and 210° or less, and the aspect ratio (major axis / minor axis) is 1.5 or more, and the positive electrode active material contains the first lithium composite transition metal oxide in an amount of 20% to 100% by volume relative to the total volume of the positive electrode active material, a method for manufacturing the same, and a positive electrode and lithium secondary battery containing the same.

Description

Technical Field

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2023-0071872 filed on June 2, 2023, and all the contents disclosed in the literature of the Korean patent application are incorporated herein by reference in their entirety.

[0002] The present invention relates to a positive electrode active material, a method for manufacturing the same, a positive electrode including the same, and a lithium secondary battery.

Background Art

[0003] As the development and demand for technologies related to mobile devices increase, the demand for secondary batteries as an energy source has been rapidly increasing. Among such secondary batteries, lithium secondary batteries having a high energy density, a high voltage, a long cycle life, and a low self-discharge rate have been commercialized and widely used.

[0004] As the positive electrode active material of a lithium secondary battery, a lithium transition metal composite oxide is used. Among them, lithium cobalt composite metal oxides such as LiCoO2, which have a high operating voltage and excellent capacity characteristics, are mainly used. However, LiCoO2 has inferior thermal properties due to the destabilization of the crystal structure caused by de-lithiation. In addition, since the LiCoO2 is expensive, there is a limit to its large-scale use as a power source in fields such as electric vehicles.

[0005] As alternatives to the aforementioned LiCoO2, materials such as lithium manganese composite metal oxides (LiMnO2 or LiMn2O4, etc.), lithium iron phosphate compounds (LiFePO4, etc.), and lithium nickel composite metal oxides (LiNiO2, etc.) have been developed. Among these, research and development on lithium nickel composite metal oxides, which have a high reversible capacity of approximately 200 mAh / g and facilitate the realization of high-capacity batteries, are being pursued more actively. However, LiNiO2 has inferior thermal stability compared to LiCoO2, and if an internal short circuit occurs due to external pressure while charged, the positive electrode active material itself decomposes, causing the battery to rupture and ignite. Therefore, as a method to maintain the excellent reversible capacity of LiNiO2 while improving its low thermal stability, lithium composite transition metal oxides in which some of the Ni is replaced with Co, Mn, and Al have been developed.

[0006] In lithium-ion batteries that use lithium-compound transition metal oxides, particularly those containing high levels of nickel (Ni-rich), as the positive electrode active material, the battery's capacity, the presence or absence of high power output, and the presence or absence of gas generation at high temperatures are influenced not only by chemical properties such as the composition of the positive electrode active material, the content of impurities, and the content of lithium by-products present on the surface, but also by physical properties such as the size, surface area, density, and shape of the positive electrode active material particles. Therefore, when using lithium-compound transition metal oxides containing high levels of nickel (Ni-rich) as the positive electrode active material, efforts are required to appropriately harmonize the battery's capacity characteristics, power output characteristics, high-temperature characteristics, and lifespan characteristics.

[0007] Therefore, there is a need to develop cathode active materials that can exhibit excellent energy volume density and lifetime characteristics. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] KR2021-0117212 A [Overview of the Initiative] [Problems that the invention aims to solve]

[0009] The object of the present invention is to provide a positive electrode active material that can exhibit excellent energy volume density and lifetime characteristics.

[0010] Another object of the present invention is to provide a method for producing the positive electrode active material.

[0011] Another object of the present invention is to provide a positive electrode containing the positive electrode active material and a lithium secondary battery containing the same. [Means for solving the problem]

[0012] To solve the above problems, the present invention provides a positive electrode active material, a method for producing a positive electrode active material, a positive electrode for a lithium secondary battery containing the positive electrode active material, and a lithium secondary battery.

[0013] (1) The present invention provides a positive electrode active material comprising a single-particle type first lithium composite transition metal oxide and, selectively, a single-particle type second lithium composite transition metal oxide, wherein the single-particle type first lithium composite transition metal oxide consists of 30 or fewer disk-shaped primary particles, and the disk-shaped primary particles, as observed from an SEM image of the surface or cross-section of the positive electrode active material, have two boundary lines of primary particles that exist within an angle of 45° or less with respect to the long axis direction, and when a virtual line is drawn that has the most contact points for each of these boundary lines, and one virtual line is drawn that crosses the two tangents, the ipsilateral interior angle is 150° or more and 210° or less, and the aspect ratio (long axis / short axis) is 1.5 or more, and the positive electrode active material provides a positive electrode active material comprising the first lithium composite transition metal oxide in an amount of 20% to 100% of the total volume of the positive electrode active material.

[0014] (2) The present invention provides a positive electrode active material in which the positive electrode active material contains the first lithium composite transition metal oxide in an amount of 20% to 70% by volume relative to the total volume of the positive electrode active material.

[0015] (3) The present invention provides a positive electrode active material in which, in (1) or (2) above, the first lithium composite transition metal oxide has an aspect ratio (long axis / short axis) of 1.5 or more and 10 or less.

[0016] (4) In the present invention, in (1) to (3) above, the first lithium composite transition metal oxide is such that when the volume is calculated from the following formula 1 for each primary particle observed from an SEM image of the surface or cross-section of the positive electrode active material, the single particle degree (V) corresponds to the volume at the point where the cumulative volume distribution of the primary particles reaches 50%. 50 The present invention provides a positive electrode active material having a diameter of 1.2 μm or more.

number

[0017] (5) In any one of (1) to (4) above, the present invention provides that the first lithium composite transition metal oxide has an average radius (R) at the point where the cumulative radius distribution of the particles reaches 50% when the radius of each primary particle observed from an SEM image (measurement magnification 3,000x) of the surface or cross-section of the positive electrode active material is calculated. 50 The present invention provides a positive electrode active material in which the radius is 1 μm or more and 15 μm or less, and the radius is the radius of the surface or cross-section of the primary particle when it is assumed that the surface or cross-section of the primary particle is circular.

[0018] (6) In any one of (1) to (5) above, the present invention provides a positive electrode active material in which the first lithium composite transition metal oxide has a composition represented by the following chemical formula 1. [Chemical formula 1] Li a Ni x Co y M 1 z M2 1-x-y-z O2 In the chemical formula 1, M 1 is one or more selected from the group consisting of Mn and Al, and M 2 is one or more selected from the group consisting of B, Ba, Ce, Cr, F, Mg, V, Ti, Fe, Zr, Zn, Si, Y, Nb, Ga, Sn, Mo, W, P, S, Sr, Ta, La, and Hf, and 0.9 ≦ a ≦ 1.3, 0.6 ≦ x < 1.0, 0 < y < 0.4, 0 < z < 0.4, 0 ≦ 1 - x - y - z < 0.4.

[0019] (7) The present invention provides a positive electrode including the positive electrode active material according to any one of (1) to (6) above.

[0020] (8) The present invention provides a lithium secondary battery including the positive electrode according to (7) above.

[0021] (9) The present invention is a method for manufacturing a positive electrode active material including: (A) mixing a positive electrode active material precursor and a first lithium-containing raw material substance having a lower density inside than outside to produce a mixture; and (B) subjecting the mixture to a primary firing at a temperature of 800°C or higher and 950°C or lower to produce a primary fired product, wherein the inside is a region corresponding to 50% or less of the radius from the center of the positive electrode active material precursor toward the outermost edge, the positive electrode active material is in the form of single particles composed of 30 or fewer primary particles, includes a disk-shaped first lithium composite transition metal oxide, and the first lithium composite transition metal oxide is contained in an amount of 20% by volume or more and 100% by volume or less based on the total volume of the positive electrode active material.

[0022] (10) The present invention provides a method for manufacturing a positive electrode active material further including, in (9) above, a step (B1) of pulverizing the primary fired product immediately after the step (B).

[0023] (11) The present invention provides a method for producing a positive electrode active material, further comprising the step of (C) after step (B) above, mixing a second lithium-containing raw material with the primary calcined product and then performing secondary calcination at a temperature of 680°C to 850°C to produce a secondary calcined product.

[0024] (12) The present invention provides a method for producing a positive electrode active material, further comprising the step of (C1) of grinding the secondary calcined product immediately after the step of (C) in (11).

[0025] (13) In any one of (9) to (12) above, the present invention provides the positive electrode active material precursor by (S1) adding a transition metal-containing solution and an ammonium ion-containing solution at a predetermined flow rate to a reactor including a stirring device, adding a basic aqueous solution, and stirring while maintaining the stirring speed to produce a seed mixture; (S2) adding the transition metal-containing solution, the ammonium ion-containing solution and the basic aqueous solution to the seed mixture, and stirring while gradually decreasing the stirring speed to produce a particle growth mixture; and (S3) the particle The present invention provides a method for producing a positive electrode active material, comprising the steps of adding the transition metal-containing solution to a seed growth mixed solution at a flow rate increased compared to step (S2), adding the ammonium ion-containing solution at a gradually increasing flow rate, adding the basic aqueous solution, and stirring while maintaining the stirring speed to produce a mixed solution for a positive electrode active material precursor, wherein the basic aqueous solution is added in such a way that the pH of the seed mixed solution is kept constant, the pH of the particle growth mixed solution is gradually decreased, and the pH of the positive electrode active material precursor mixed solution is kept constant.

[0026] (14) The present invention provides a method for producing a positive electrode active material, wherein, in (13) above, the basic aqueous solution is added so that the pH of the particle growth mixed solution gradually decreases from pH 12 to 13 to pH 11.2 to 12.6.

[0027] (15) The present invention provides a method for producing a positive electrode active material in step (S2) of (13) or (14) above, wherein the stirring speed is gradually reduced from 700 rpm to 900 rpm to 500 rpm to 650 rpm.

[0028] (16) The present invention provides a method for producing a positive electrode active material, wherein in any one of the above (13) to (15), step (S3) is to introduce the transition metal-containing solution at a flow rate of 1.2 times or more and 1.4 times or less than that of step (S2), and introduce the ammonium ion-containing solution at a flow rate that is gradually increased to 20% or more and 45% or less of that of the transition metal-containing solution. [Effects of the Invention]

[0029] The positive electrode active material according to the present invention comprises a single-particle type first lithium composite transition metal oxide and, selectively, a single-particle type second lithium composite transition metal oxide. The single-particle type first lithium composite transition metal oxide consists of 30 or fewer disk-shaped primary particles, and the disk-shaped primary particles, as observed from an SEM image of the surface or cross-section of the positive electrode active material, have two boundary lines of primary particles that exist within an angle of 45° or less with respect to the major axis direction, and when a virtual line is drawn across the two tangents, the ipsilateral interior angle is 150° or more and 210° or less, and the aspect ratio (major axis / minor axis) is 1.5 or more. The positive electrode active material contains the first lithium composite transition metal oxide in an amount of 20% to 100% of the total volume of the positive electrode active material, thereby enabling the positive electrode and lithium secondary battery containing the positive electrode active material of the present invention to exhibit excellent energy volume density and life characteristics. [Brief explanation of the drawing]

[0030] [Figure 1](A) is an SEM image of a cross-section of the positive electrode active material precursor produced in Production Example 1, (B) is an SEM image of a cross-section of the positive electrode active material precursor produced in Production Example 2, (C) is an SEM image of a cross-section of the positive electrode active material precursor produced in Production Example 3, (D) is an SEM image of a cross-section of the positive electrode active material precursor produced in Production Example 4, (E) is an SEM image of a cross-section of the positive electrode active material precursor produced in Comparative Production Example 1, and (F) is an SEM image of a cross-section of the positive electrode active material precursor produced in Comparative Production Example 2. [Figure 2] This is a segmentation image of the positive electrode active material produced in Example 1. [Figure 3] This is a segmentation image of the positive electrode active material produced in Example 2. [Figure 4] This is a segmentation image of the positive electrode active material produced in Example 3. [Figure 5] This is a segmentation image of the positive electrode active material produced in Example 4. [Figure 6] This is a segmentation image of the positive electrode active material produced in Comparative Example 1. [Figure 7] This is a segmentation image of the positive electrode active material produced in Comparative Example 2. [Modes for carrying out the invention]

[0031] The present invention will be described in more detail below.

[0032] The terms and words used in this specification and in the claims should not be interpreted in a manner limited to their ordinary or dictionary meanings, but rather in a manner consistent with the technical idea of ​​the present invention, in accordance with the principle that inventors may define the concepts of terms as appropriate to best describe their invention.

[0033] In the present invention, the term "primary particle" refers to the smallest particle unit that can be distinguished as a single mass when a cross-section of the positive electrode active material is observed by a scanning electron microscope (SEM), and can consist of one crystal grain or multiple crystal grains. The term "crystal grain" or "grain region" refers to a region in the sample where atoms are arranged continuously and periodically in one direction. The crystal grain can be analyzed using an electron backscatter diffraction (ESBD) analyzer.

[0034] In this invention, the term "secondary particle" refers to a secondary structure formed by the aggregation of multiple primary particles. The average particle size of the secondary particle can be measured using a particle size analyzer.

[0035] In the present invention, the term "single-particle form" can be replaced with the term "single-particle type," and refers to a form that is contrasted with the secondary particle form formed by the aggregation of several hundred primary particles manufactured by conventional methods. Furthermore, in the present invention, the terms "single-particle type positive electrode active material" or "single-particle form lithium composite transition metal oxide" are concepts that are contrasted with the secondary particle form positive electrode active material formed by the aggregation of several hundred primary particles manufactured by conventional methods, and may be a single particle consisting of one primary particle, or two or more, or five or more, or 10 or fewer, 15 or fewer, 20 or fewer, 25 or fewer, or 30 or fewer primary particles that have aggregated into secondary particles.

[0036] In the present invention, the term "volume ratio (volume %)" is calculated by determining the volume of each primary particle observed from an SEM image (measurement magnification 3,000x) of the surface or cross-section of the positive electrode active material using the following formula 1, determining the total volume of the positive electrode active material and the total volume of the first lithium composite transition metal oxide, dividing the total volume of the first lithium composite transition metal oxide by the total volume of the positive electrode active material, and multiplying by 100.

[0037]

number

[0038] In the above formula 1, The radius is the radius of the surface or cross-section of the primary particle, assuming that the surface or cross-section of the primary particle observed from the SEM image (measurement magnification 3,000x) is circular.

[0039] In this invention, the term "average particle size (D 50 )" refers to the particle size at the 50% point of the cumulative volume distribution by particle size. The average particle size is calculated by dispersing the powder to be measured in a dispersion medium, introducing it into a commercially available laser diffraction particle size analyzer (e.g., QUANTA FEG 250, manufactured by FEI), measuring the difference in diffraction patterns due to particle size as the particles pass through the laser beam to calculate the particle size distribution, and then calculating the particle diameter at the point where the cumulative volume distribution by particle size in the measuring device reaches 50%. 50 It can be measured.

[0040] In the present invention, the term "segmentation image" refers to an image segmented at the individual positive electrode active material particle level, and can be obtained by a method comprising: a first step of obtaining an SEM image by analyzing the positive electrode active material powder with a scanning electron microscope; and a second step of using deep learning or computer image processing techniques to remove the boundaries (edges) of the individual positive electrode active material particles from the SEM image, detecting the contours of the individual positive electrode active material particles, and using these to obtain an image segmented at the individual positive electrode active material particle level. Specifically, the segmentation image can be obtained by the method described in KR10-2022-0048191 A and KR10-2022-0048192 A.

[0041] In this invention, the term "major axis" refers to the length of the longest line segment obtained by drawing a line passing through two points at the boundary of a primary particle in a primary particle observed from an SEM image of the surface or cross-section of the positive electrode active material.

[0042] In this invention, the term "aspect ratio" refers to a method in which, first, the shape of a single primary particle to be measured is selected in the SEM image of the particle, and then the ratio of the major axis to the minor axis, i.e., the aspect ratio, is measured using an eigenvector.

[0043] In this invention, the term "long axis" refers to the axis that passes through the center of gravity of the primary particle and where the axial dispersion is maximized, and the term "short axis" refers to the axis that passes through the center of gravity of the primary particle and where the axial dispersion is minimized.

[0044] positive electrode active material The positive electrode active material according to the present invention will be described below.

[0045] The present inventors have provided a positive electrode active material comprising a single-particle type first lithium composite transition metal oxide and, selectively, a single-particle type second lithium composite transition metal oxide, wherein the single-particle type first lithium composite transition metal oxide consists of 30 or fewer disk-shaped primary particles. The present invention was completed when, in primary particles of type () observed from SEM images of the surface or cross-section of the positive electrode active material, a virtual tangent line is drawn to each of the two boundary lines of primary particles that exist within an angle of 45° or less with respect to the major axis direction, and a virtual line is drawn crossing the two tangent lines, the ipsilateral interior angle is 150° or more and 210° or less, the aspect ratio (major axis / minor axis) is 1.5 or more, and the positive electrode active material contains the first lithium composite transition metal oxide in an amount of 20% to 100% of the total volume of the positive electrode active material, the reaction between the positive electrode active material and the electrolyte does not occur well, the energy density of the battery containing the positive electrode active material is maintained, and the life characteristics are improved.

[0046] The first lithium composite transition metal oxide is in a single-particle form consisting of 30 or fewer primary particles. That is, the first lithium composite transition metal oxide is in a single-particle form or a single-particle form in which 2 to 30 primary particles are aggregated. The single-particle form is distinguished from secondary particles in which more than 30 primary particles are aggregated. When the first lithium composite transition metal oxide has a single-particle form, it has excellent stability, and even when the positive electrode active material containing it is rolled, the positive electrode active material does not crack or break, and side reactions between the positive electrode active material and the electrolyte can be reduced. As a result, durability against volume changes during battery charging and discharging can be improved, and the lifespan characteristics can be improved. When the first lithium composite transition metal oxide is in the form of secondary particles, the positive electrode active material containing it cracks or breaks, and there is a problem of poor lifespan characteristics due to side reactions between the positive electrode active material and the electrolyte.

[0047] On the other hand, the single-particle type first lithium composite transition metal oxide consists of 30 or fewer disk-shaped primary particles, and the disk-shaped primary particles, as observed from an SEM image of the surface or cross-section of the positive electrode active material, have two boundary lines of primary particles that exist within an angle of 45° or less with respect to the major axis direction. When a virtual line is drawn that has the most contact points for each of these boundary lines, and a virtual line is drawn that crosses the two tangent lines, the ipsilateral interior angle is 150° or more and 210° or less, and the aspect ratio (major axis / minor axis) is 1.5 or more.

[0048] Furthermore, the disc-shaped primary particles may have a crystal size of 380 nm or more and 480 nm or less in the (003) plane as determined by X-ray diffraction spectral analysis, more specifically 400 nm or more and 450 nm or less, and more specifically 400 nm or more and 440 nm or less.

[0049] Disc-shaped primary particles have the advantage of having poor reactivity with the electrolyte, preventing rapid irreversible damage to the positive electrode active material even after repeated charging and discharging. On the other hand, if the single-particle type lithium-1 composite transition metal oxide is not disc-shaped primary particles, the irreversible damage to the positive electrode active material increases rapidly with repeated charging and discharging, resulting in poor lifetime characteristics.

[0050] The positive electrode active material according to the present invention contains the first lithium composite transition metal oxide in an amount of 20% to 100% by volume relative to the total volume of the positive electrode active material. Specifically, the first lithium composite transition metal oxide can be contained in an amount of 20% or more by volume, or 25% or more by volume, and 70% or less by volume, 75% or less by volume, 80% or less by volume, 85% or less by volume, 90% or less by volume, 95% or less by volume, or 100% or less by volume relative to the total volume of the positive electrode active material. When the content of the first lithium composite transition metal oxide satisfies the above range, it can exhibit excellent performance in terms of initial discharge capacity and excellent lifetime characteristics.

[0051] According to one embodiment of the present invention, the first lithium composite transition metal oxide may have an aspect ratio (long axis / short axis) of 1.5 or more and 10 or less. Specifically, it may be 1.5 or more, 1.51 or more, 1.52 or more, 1.53 or more, 1.54 or more, 1.55 or more, 1.56 or more, 1.57 or more, 1.58 or more, 1.59 or more, 1.6 or more, 1.7 or more, 1.8 or more, 1.9 or more, 2.0 or more, 2.5 or more, 3.0 or more, or 4.0 or more, and may be 5.0 or less, 6.0 or less, 7.0 or less, 8.0 or less, 9.0 or less, or 10.0 or less. When the aspect ratio of the first lithium composite transition metal oxide is within the above range, a positive electrode active material containing disc-shaped particles can be manufactured, which has the effect of improving lifetime characteristics.

[0052] According to one embodiment of the present invention, the first lithium composite transition metal oxide is such that when the volume of each primary particle observed from an SEM image of the surface or cross-section of the positive electrode active material is calculated from the following formula 1, the single-particle degree (V) corresponds to the volume at the point where the cumulative volume distribution of the primary particles reaches 50%. 50) may be 1.2 μm or larger.

[0053]

number

[0054] In the above formula 1, The radius is the radius of the surface or cross-section of the primary particle, assuming that the surface or cross-section of the primary particle observed from the SEM image (measurement magnification 3,000x) is circular.

[0055] Specifically, the degree of single-particle formation (V 50 ) is 1.2 μm 3 or more, 1.3μm 3 or more, 1.4μm 3 Above, 1.5 μm 3 Above, 1.6 μm 3 or more, 1.7μm 3 Above, 1.8 μm 3 Above, 1.9 μm 3 2.0μm or more 3 or greater than 2.1 μm 3 It may be greater than or equal to 3.6 μm 3 Below, 4.0μm 3 The following, or 5.0 μm 3 The following may also apply: The degree of single-particle formation (V 50 When the value is within the aforementioned range, it has the effect of improving energy density and lifetime characteristics.

[0056] According to one embodiment of the present invention, the first lithium composite transition metal oxide has an average radius (R) at the point where the cumulative radius distribution of the particles reaches 50% when the radius of each primary particle observed from an SEM image (measurement magnification 3,000x) of the surface or cross-section of the positive electrode active material is calculated. 50 The radius is 1 μm or more and 15 μm or less, and the radius may be the radius of the surface or cross-section of the primary particle assuming that the surface or cross-section of the primary particle is circular. Specifically, the average radius (R 50) may be 1 μm or more, or 2 μm or more, and may be 10 μm or less, 12 μm or less, or 15 μm or less.

[0057] According to one embodiment of the present invention, the positive electrode active material may optionally further contain a single-particle type second lithium composite transition metal oxide.

[0058] The second lithium composite transition metal oxide is in the form of a single particle consisting of 30 or fewer primary particles. That is, the second lithium composite transition metal oxide is in the form of a single particle or a single particle formed by the aggregation of 2 to 30 primary particles. The single particle form is distinguished from secondary particles formed by the aggregation of more than 30 primary particles. When the second lithium composite transition metal oxide has a single particle form, it has excellent stability, and even when the positive electrode active material containing it is rolled, the positive electrode active material does not crack or break, and side reactions between the positive electrode active material and the electrolyte can be reduced. As a result, durability against volume changes during battery charging and discharging can be improved, and the lifespan characteristics can be improved. When the second lithium composite transition metal oxide is in the form of a secondary particle, the positive electrode active material containing it cracks or breaks, and there is a problem of poor lifespan characteristics due to side reactions between the positive electrode active material and the electrolyte.

[0059] Furthermore, the second lithium composite transition metal oxide does not contain disk-type primary particles. For example, it may be a polyhedron, sphere, ellipsoid, cylinder, particle shape, or similar shape, and does not necessarily satisfy the definition of disk-type.

[0060] The second lithium composite transition metal oxide can have superior reactivity compared to the first lithium composite transition metal oxide, and by including it, the positive electrode active material of the present invention can exhibit superior performance in terms of initial discharge capacity.

[0061] Furthermore, the average particle size (D) of the second lithium composite transition metal oxide is 50 The size of the particle may be 1 μm or more, 2 μm or more, 3 μm or more, or 4 μm or more, and may be 5 μm or less, 10 μm or less, or 15 μm or less.

[0062] According to one embodiment of the present invention, the first lithium composite transition metal oxide may have a composition represented by the following chemical formula 1.

[0063] [Chemical formula 1] Li a Ni x Co y M 1 z M 2 1-x-y-z O2

[0064] In the aforementioned chemical formula 1, M 1 is one or more selected from the group consisting of Mn and Al, M 2 is one or more elements selected from the group consisting of B, Ba, Ce, Cr, F, Mg, V, Ti, Fe, Zr, Zn, Si, Y, Nb, Ga, Sn, Mo, W, P, S, Sr, Ta, La, and Hf. 0.9 ≤ a ≤ 1.3, 0.6 ≤ x < 1.0, 0 <y<0.4、0<z<0.4、0≦1-x-y-z<0.4である。

[0065] Said M 1 is one or more selected from the group consisting of Mn and Al, and the M 2 M is a doping element, specifically, 2 The M may be one or more selected from the group consisting of B, Ba, Ce, Cr, F, Mg, V, Ti, Fe, Zr, Zn, Si, Y, Nb, Ga, Sn, Mo, W, P, S, Sr, Ta, La, and Hf. 2 Although not necessarily present, when present in appropriate amounts, it can improve the particle shape of the positive electrode active material and enhance the stability of its crystal structure.

[0066] On the other hand, a may be 0.9 or more, 0.95 or more, or 1 or more, and may be 1.1 or less, 1.2 or less, or 1.3 or less. When a satisfies the above range, high capacity characteristics and high energy density per unit volume can be achieved.

[0067] The aforementioned x is the mole fraction of nickel (Ni) among the total metals other than lithium in the first lithium composite transition metal oxide, and may be 0.6 or more, 0.65 or more, 0.7 or more, 0.75 or more, or 0.8 or more, or 0.9 or less, or less than 1. When x is within the above range, the capacitance characteristics of the positive electrode active material can be improved.

[0068] The above y is the mole fraction of cobalt (Co) among the total metals other than lithium in the first lithium composite transition metal oxide, and may be greater than 0, 0.01 or more, 0.02 or more, or 0.03 or more, and may be 0.05 or less, 0.06 or less, 0.07 or less, 0.08 or less, 0.09 or less, 0.1 or less, 0.2 or less, 0.3 or less, or less than 0.4. When y satisfies the above range, structural stability can be increased and the decomposition reaction of the electrolyte can be relatively reduced.

[0069] The aforementioned z is M of the total metals other than lithium in the first lithium composite transition metal oxide. 1 This is the mole fraction, and may be greater than 0, 0.01 or more, 0.02 or more, 0.03 or more, 0.05 or more, 0.06 or more, 0.07 or more, or 0.08 or more, and may be 0.09 or less, 0.1 or less, 0.2 or less, 0.3 or less, or less than 0.4. When z satisfies the above range, structural stability increases and the decomposition reaction of the electrolyte can be relatively reduced.

[0070] According to one embodiment of the present invention, the second lithium composite transition metal oxide may have a composition represented by the following chemical formula 2.

[0071] [Chemical formula 2] Li a1 Ni x1 Co y1 M 1 ' z1 M 2 ' 1-x1-y1-z1 O2

[0072] In the aforementioned chemical formula 2, M1 ' is one or more elements selected from the group consisting of Mn and Al, M 2 ' is one or more elements selected from the group consisting of B, Ba, Ce, Cr, F, Mg, V, Ti, Fe, Zr, Zn, Si, Y, Nb, Ga, Sn, Mo, W, P, S, Sr, Ta, La, and Hf. 0.9≦a1≦1.3, 0.6≦x1<1.0, 0 <y1<0.4、0<z1<0.4、0≦1-x1-y1-z1<0.4である。

[0073] Said M 1 ' is one or more selected from the group consisting of Mn and Al, and the M 2 ' is a doping element, specifically, M 2 ' may be one or more selected from the group consisting of B, Ba, Ce, Cr, F, Mg, V, Ti, Fe, Zr, Zn, Si, Y, Nb, Ga, Sn, Mo, W, P, S, Sr, Ta, La, and Hf. The M 2 While it is not necessarily present, when included in an appropriate amount, it can improve the particle shape of the positive electrode active material and enhance the stability of its crystal structure.

[0074] On the other hand, a1 may be 0.9 or more, 0.95 or more, or 1 or more, and may be 1.1 or less, 1.2 or less, or 1.3 or less. When a1 satisfies the above range, high capacity characteristics and high energy density per unit volume can be achieved.

[0075] The aforementioned x1 is the mole fraction of nickel (Ni) among the total metals other than lithium in the second lithium composite transition metal oxide, and may be 0.6 or more, 0.65 or more, 0.7 or more, 0.75 or more, or 0.8 or more, or 0.9 or less, or less than 1. When x1 is within the above range, the capacitance characteristics of the positive electrode active material can be improved.

[0076] The above y1 is the mole fraction of cobalt (Co) among the total metals other than lithium in the second lithium composite transition metal oxide, and may be greater than 0, 0.01 or more, 0.02 or more, or 0.03 or more, and may be 0.05 or less, 0.06 or less, 0.07 or less, 0.08 or less, 0.09 or less, 0.1 or less, 0.2 or less, 0.3 or less, or less than 0.4. When y1 satisfies the above range, structural stability can be increased and the decomposition reaction of the electrolyte can be relatively reduced.

[0077] The aforementioned z1 is M, which is the total metal other than lithium in the second lithium composite transition metal oxide. 1 ' is the mole fraction of ', and may be greater than 0, 0.01 or more, 0.02 or more, 0.03 or more, 0.05 or more, 0.06 or more, 0.07 or more, or 0.08 or more, and may be 0.09 or less, 0.1 or less, 0.2 or less, 0.3 or less, or less than 0.4. When z1 satisfies the above range, structural stability can be increased and the decomposition reaction of the electrolyte can be relatively reduced.

[0078] The first lithium composite transition metal oxide and the second lithium composite transition metal oxide may have the same or different compositions. For example, the first lithium composite transition metal oxide may have a nickel molar ratio of 70 mol% or more of the total metals other than lithium, and the second lithium composite transition metal oxide may have a nickel molar ratio of 80 mol% to 95 mol% of the total metals other than lithium.

[0079] On the other hand, the first lithium composite transition metal oxide and the second lithium composite transition metal oxide may further include a coating portion on their surface, if necessary, which contains one or more elements selected from the group consisting of Co, Al, B, Ba, Ce, Cr, F, Mg, V, Ti, Fe, Zr, Zn, Si, Y, Nb, Ga, Sn, Mo, W, P, S, Sr, Ta, La, and Hf (hereinafter referred to as "coating elements"). When such a coating portion is included, contact between the lithium composite transition metal oxide and the electrolyte is blocked, and the generation of gases due to side reactions with the electrolyte and the elution of transition metals can be effectively suppressed.

[0080] The coated portion can be formed by mixing a first lithium composite transition metal oxide or a second lithium composite transition metal oxide with a raw material containing the coating element, and then heat-treating it at a temperature of 200°C to 800°C.

[0081] Method for manufacturing positive electrode active material The following describes the method for producing a positive electrode active material according to the present invention. The positive electrode active material production method of the present invention is a method for producing the positive electrode active material according to the present invention.

[0082] The present invention provides a method for producing a positive electrode active material, comprising the steps of (A) mixing a positive electrode active material precursor having a lower internal density than the external density with a first lithium-containing raw material to produce a mixture, and (B) primary firing the mixture at a temperature of 800°C to 950°C to produce a primary fired product, wherein the internal region is a region corresponding to 50% or less of the radius from the center of the positive electrode active material precursor toward the outermost edge, the positive electrode active material is in a single-particle form consisting of 30 or fewer primary particles, and contains a disk-shaped (disk-type) first lithium composite transition metal oxide, and the first lithium composite transition metal oxide is present in an amount of 20% to 100% of the total volume of the positive electrode active material.

[0083] The above-mentioned invention can be manufactured by appropriately adjusting the type of raw material, the mixing ratio of the raw material, the firing time, etc.

[0084] The steps of the present invention will be described in detail below.

[0085] (A) Step The process includes step (A), which involves mixing a positive electrode active material precursor having a lower internal density than its external density with a first lithium-containing raw material to produce a mixture.

[0086] The positive electrode active material precursor has a lower internal density compared to its external density. Here, the internal region is the area corresponding to 50% or less of the radius from the center of the positive electrode active material precursor toward the outermost edge. When the internal density of the precursor is lower than the external density, a positive electrode active material containing disc-shaped primary particles in a specific content can be produced when mixed with a lithium-containing raw material and then calcined. If the internal density of the positive electrode active material precursor is the same as the external density, or if the internal density is higher than the external density, there is a problem in that disc-shaped primary particles are not formed to a sufficient extent.

[0087] According to one embodiment of the present invention, the positive electrode active material precursor is prepared by (S1) introducing a transition metal-containing solution and an ammonium ion-containing solution at a predetermined flow rate into a reactor including a stirring device, adding a basic aqueous solution, and stirring while maintaining the stirring speed to produce a seed mixture; (S2) introducing the transition metal-containing solution, the ammonium ion-containing solution and the basic aqueous solution into the seed mixture, and stirring while gradually decreasing the stirring speed to produce a particle growth mixture; and (S3) preparing the particle growth The process includes the steps of adding the transition metal-containing solution to the mixed solution at a flow rate increased compared to step (S2), adding the ammonium ion-containing solution at a gradually increasing flow rate, adding the basic aqueous solution, and stirring while maintaining the stirring speed to produce a mixed solution for the positive electrode active material precursor, wherein the basic aqueous solution can be added in such a way that the pH of the seed mixed solution is kept constant, the pH of the particle growth mixed solution is gradually decreased, and the pH of the positive electrode active material precursor mixed solution is kept constant. In this case, a precursor of the positive electrode active material with an internal density lower than the external density can be effectively produced.

[0088] Step (S1) may be a seed formation step, step (S2) may be an internal particle growth step, and step (S3) may be an external particle growth step. If the stirring speed is not gradually reduced in step (S2), there is a problem in that it is difficult to produce a positive electrode active material in which the internal density is lower than the external density. In step (S3), if the transition metal-containing solution is not added to the particle growth mixed solution at a flow rate increased compared to step (S2), or if the ammonium ion-containing solution is not added at a flow rate that is gradually increased, there is a problem in that it is difficult to increase the external density compared to the internal density.

[0089] First, according to one embodiment of the present invention, the basic aqueous solution can be added so as to gradually decrease the pH of the particle growth mixed solution from pH 12-13 to pH 11.2-12.6. Specifically, the basic aqueous solution may be added so as to gradually decrease the pH of the particle growth mixed solution from pH 12-12.5 to pH 11.2-11.5. The basic aqueous solution may also be added so as to gradually decrease the pH of the particle growth mixed solution by 0.05-0.2 per hour. The basic aqueous solution may also be added so as to maintain a constant pH once the pH of the particle growth mixed solution reaches the target pH.

[0090] According to one embodiment of the present invention, steps (S1) and (S3) can be stirred at a predetermined stirring speed. In this case, there is an effect of growing the particles at a uniform density.

[0091] According to one embodiment of the present invention, step (S2) can be performed by stirring while gradually decreasing the stirring speed from 700 rpm to 900 rpm to 500 rpm to 650 rpm. Specifically, step (S2) can be performed by stirring while gradually decreasing the stirring speed from 700 rpm to 900 rpm to 500 rpm to 650 rpm, or from 750 rpm to 850 rpm to 500 rpm to 600 rpm. The stirring speed may be the stirring speed from the time when the transition metal-containing solution, the ammonium ion-containing solution, and the basic aqueous solution are added to the seed mixture until immediately before step (S3) is performed. When stirring in step (S2) while gradually decreasing the stirring speed within the above range, there is an effect of growing particles at a low density.

[0092] According to one embodiment of the present invention, step (S3) may involve adding the transition metal-containing solution at a flow rate of 1.2 to 1.4 times that of step (S2), and adding the ammonium ion-containing solution at a flow rate that is gradually increased to 20% to 45% of the flow rate of the transition metal-containing solution. Specifically, step (S3) may involve adding the transition metal-containing solution at a flow rate of 1.2 to 1.3 to 1.4 times that of step (S2), and adding the ion-containing solution at a flow rate that is gradually increased to 20% to 25% to 35%, 40%, or 45% of the flow rate of the transition metal-containing solution. When the flow rates of the transition metal-containing solution and the ammonium ion-containing solution are adjusted within the above range, a positive electrode active material precursor with increased external density can be produced.

[0093] (B) Step Next, the process includes step (B) of first firing the mixture at a temperature of 800°C to 950°C to produce a first-fired product.

[0094] Specifically, the mixture is subjected to primary calcination at a temperature of 800°C or higher, or 850°C or higher, 900°C or lower, or 950°C or lower to produce a primary calcined product. When the primary calcination temperature is within the above range, the primary particles of the positive electrode active material precursor aggregate, making it possible to produce a structurally stable single-particle calcined product. If the primary calcination temperature is below 800°C, it may be difficult to produce a single-particle calcined product, and if it is above 950°C, there is a problem in that a structurally unstable calcined product with low crystallinity is produced.

[0095] The aforementioned primary calcination may be carried out under an oxygen atmosphere in order to prevent the lithium composite transition metal oxide from degenerating into a rock salt structure.

[0096] The aforementioned primary firing may be carried out for 3 hours or more and 12 hours or less. Specifically, the primary firing may be carried out for 3 hours or more, 4 hours or more, or 5 hours or more, and 6 hours or less, 9 hours or less, 10 hours or less, 11 hours or less, or 12 hours or less. In this case, the primary particles can be aggregated and the crystallinity of the primary fired product can be increased.

[0097] During the primary firing, the heating rate may be 4°C / min to 7°C / min, and more specifically, 5°C / min to 7°C / min. When the heating rate during the primary firing satisfies the above range, the primary particles of the positive electrode active material precursor can aggregate, forming a structurally more stable single-particle primary firing product, and the amount of fine powder with a particle size of 1 μm or less in the final manufactured positive electrode active material can be minimized.

[0098] According to one embodiment of the present invention, immediately after step (B), a further step (B1) of grinding the primary calcined product may be included. In terms of preventing the initial resistance from becoming high, the primary calcined product is ground to an average particle size (D 50The material may be ground so that the particle size (D) is between 3.50 μm and 10.00 μm. This grinding can be performed using a pin mill, ACM, jet mill, etc. On the other hand, the pin mill can be used at 18,000 rpm, the ACM can be used with Hosokawa equipment at 6,000 rpm for classification and 12,000 rpm for grinding, and the jet mill can be used with ZM solution equipment at a grinding pressure of 6 bar and 3,500 rpm for classification. In this case, the desired average particle size (D) can be obtained. 50 A positive electrode active material having ) can be easily obtained.

[0099] According to one embodiment of the present invention, after step (B), the step of (C) may further be included in which a second lithium-containing raw material is mixed with the primary calcined product, and then the product is calcined again at a temperature of 680°C to 850°C to produce a secondary calcined product. Specifically, after mixing the second lithium-containing raw material with the primary calcined product, the product may be calcined again at a temperature of 680°C to 700°C to 720°C to 740°C to 760°C to 780°C, and 800°C to 820°C to 850°C to produce a secondary calcined product.

[0100] Here, the primary-fired product may be cooled to room temperature before secondary firing. When the secondary firing temperature is within the aforementioned range, lithium is inserted into the rock salt structure that may form on the surface of the primary-fired product due to the high temperature during primary firing, restoring it to a layered structure and reducing the amount of lithium by-products.

[0101] The aforementioned secondary calcination may be carried out under an oxygen atmosphere in order to prevent the lithium composite transition metal oxide from degenerating into a rock salt structure.

[0102] The aforementioned secondary firing may be carried out for 3 hours or more and 12 hours or less. Specifically, the aforementioned primary firing may be carried out for 3 hours or more, 4 hours or more, 5 hours or more, 6 hours or more, 7 hours or more, or 8 hours or more, and 9 hours or less, 10 hours or less, 11 hours or less, or 12 hours or less. In this case, there is an effect of increasing the degree of crystallinity of the internal crystal structure of the positive electrode active material.

[0103] The heating rate during the secondary firing may be 4°C / min to 7°C / min, and more specifically, 5°C / min to 7°C / min. When the heating rate during the secondary firing satisfies the above range, lithium can be more effectively inserted into the rock salt structure that may form on the surface of the primary firing product, restoring it to a layered structure, further reducing lithium by-products, and minimizing the content of fine powder with a particle size of 1 μm or less in the positive electrode active material after rolling.

[0104] According to one embodiment of the present invention, immediately after step (C), a further step (C1) of grinding the secondary calcined product may be included. In terms of preventing high initial resistance, the secondary calcined product is ground to an average particle size (D 50 The material may be ground to a particle size of 3.50 μm or more and 10.00 μm or less. The grinding may be performed using a pin mill, ACM, jet mill, etc. Alternatively, the pin mill may be used at 18,000 rpm, the ACM may be used with equipment manufactured by Hosokawa Corporation at 6,000 rpm for classification and 12,000 rpm for grinding, and the jet mill may be used with equipment manufactured by ZM Solution Corporation at a grinding pressure of 6 bar and 3,500 rpm for classification. In this case, the desired average particle size (D 50 A positive electrode active material having ) can be easily obtained.

[0105] According to one embodiment of the present invention, a positive electrode active material can be manufactured by a process in which lithium-containing raw material is introduced in two stages. That is, the lithium-containing raw material is introduced separately before the primary calcination and before the secondary calcination. In this case, there is an advantage in that lithium is inserted into the rock salt structure that may be formed on the surface, which facilitates the recovery to a layered structure. On the other hand, if the lithium-containing raw material is introduced all at once before the primary calcination, there is a problem of decreased electrochemical performance due to an increase in lithium byproducts, and if the lithium-containing raw material is not introduced in the secondary calcination step, a problem arises in which a slow reaction rate, high temperature and long period of time are required.

[0106] When the lithium-containing raw material is added in two separate steps, in step (A), the first lithium-containing raw material can be mixed such that the ratio (M:Li) of the total number of moles of transition metal (M) contained in the positive electrode active material precursor to the number of moles of lithium (Li) contained in the first lithium-containing raw material is 1:0.98 or higher, 0.99 or higher, or 1.00 or higher, and 1.01 or lower, 1.02 or lower, 1.03 or lower, 1.04 or lower, or 1.05 or lower. In step (C), the second lithium-containing raw material can be mixed such that the ratio (M:Li) of the total number of moles of transition metal (M) contained in the primary calcined product to the total number of moles of lithium (Li) is 1:1.00 or higher, 1.01 or higher, 1.02 or higher, or 1.03 or higher, and 1.05 or lower, 1.06 or lower, 1.07 or lower, 1.08 or lower, 1.09 or lower, or 1.10 or lower.

[0107] According to one embodiment of the present invention, (D) the step of mixing the secondary fired product with a cobalt-containing raw material and then heat-treating it may be further included. In this case, a coating portion containing Co is formed on the secondary fired product.

[0108] According to one embodiment of the present invention, in step (D), when mixing the secondary calcined product with the cobalt-containing raw material, an aluminum-containing raw material, a zirconium-containing raw material, or a combination thereof may be further mixed. In this case, the coating portion may further contain Al, Zr, or a combination thereof in addition to Co.

[0109] According to one embodiment of the present invention, the cobalt-containing coating raw material may be mixed in an amount such that the ratio (B / A) of the number of moles of cobalt contained in the cobalt-containing raw material to the total number of moles of metals other than lithium contained in the secondary calcined product (A) is 0.01 to 0.03. In this case, there is an advantage that lithium by-products can be controlled in the positive electrode active material manufacturing process, which does not include a water washing step.

[0110] According to one embodiment of the present invention, the cobalt-containing raw material may be one or more selected from Co(OH)2, Co3O4, CoO, (CH3CO2)2Co, CoCl2, and CoSO4·xH2O, and specifically may be Co(OH)2.

[0111] According to one embodiment of the present invention, the aluminum-containing raw material may be mixed in an amount of 0.03 to 0.10 parts by weight per 100 parts by weight of the secondary calcined product. In this case, structural stability can be ensured, thereby improving lifespan, resistance, and gas generation.

[0112] According to one embodiment of the present invention, the aluminum-containing raw material may be one or more selected from Al(OH)3, Al2(SO4)3·xH2O, Al2O3, Al(NO3)3·9H2O, AlCl3, and C2H5O4Al, and specifically may be Al(OH)3.

[0113] According to one embodiment of the present invention, the zirconium-containing raw material is Zr(OH)4, ZrO2, Zr(NO3)4, ZrCl4, ZrS2, Zr(SO4)2 and C8H 12 It may be one or more selected from O8Zr.

[0114] According to one embodiment of the present invention, the heat treatment may be carried out under an oxygen atmosphere in order to prevent the lithium composite transition metal oxide from degenerating into a rock salt structure.

[0115] According to the present invention, the heat treatment may be performed at temperatures of 600°C or higher, 610°C or higher, 620°C or higher, 630°C or higher, 640°C or higher, or 650°C or higher, and 720°C or lower, 740°C or lower, 760°C or lower, 780°C or lower, or 800°C or lower, in order to ensure that the coating portion is formed with an appropriate thickness. After that, the temperature may be lowered to approximately 450°C or higher and 550°C or lower, and then heat treatment may be performed at temperatures of 450°C or higher, 460°C or higher, 470°C or higher, 480°C or higher, and 520°C or lower, 530°C or lower, 540°C or lower, or 550°C or lower. In other words, a primary heat treatment may be performed at temperatures of 600°C or higher and 800°C or lower in a single firing profile, followed by a secondary heat treatment at temperatures of 450°C or higher and 550°C or lower.

[0116] According to one embodiment of the present invention, the heat treatment may be performed for a period of time of 1 hour or more, 2 hours or more, 3 hours or more, and 8 hours or less, 9 hours or less, or 10 hours or less in order to increase the degree of crystallinity of the coated portion.

[0117] The transition metal-containing solution may contain one or more elements selected from the group consisting of Ni, Co, and Mn, and specifically may contain Ni, Co, and Mn.

[0118] Furthermore, the transition metal-containing solution may contain additional metal-containing raw materials, which may include, for example, oxides, hydroxides, oxyhydroxides, carbonates, sulfates, halides, sulfides, acetates, nitrates, and carboxylates containing one or more elements selected from the group consisting of Al, Ti, W, B, F, P, Mg, Fe, Cr, V, Cu, Ca, Zn, Zr, Nb, Mo, Sr, Sb, Bi, Si, Cr, Hf, Ta, La, Ba, Ce, Sn, Y, and S. Or combinations thereof, specifically, ZnO, Al2O3, Al(OH)3, AlSO4, AlCl3, Al-isopropoxide, AlNO3, TiO2, WO3, AlF, H2BO3, HBO2, H3BO3, H2B4O7, B2O3, C6H5B(OH)2, (C6H5O)3B, [(CH3(CH2)3O)3B, C3H9B3O6, (C3H7O3)B, Li3WO4, (NH4) 10 W 12 O 41 Examples include 5H2O and NH4H2PO4, but are not limited to these.

[0119] positive electrode Furthermore, the present invention provides a positive electrode for a lithium secondary battery comprising a positive electrode active material layer containing the positive electrode active material. Specifically, the positive electrode comprises a positive electrode current collector and a positive electrode active material layer located on at least one surface of the positive electrode current collector, which contains the positive electrode active material. The positive electrode active material layer may have a porosity of 10% to 30% by volume, specifically 15% to 30% by volume, and more specifically 18% to 27% by volume.

[0120] The positive electrode current collector is not particularly limited as long as it does not cause chemical changes in the battery and is conductive. For example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel with surface treatment using carbon, nickel, titanium, silver, etc., can be used. The positive electrode current collector can usually have a thickness of 3 to 500 μm, and fine irregularities can be formed on the surface of the current collector to enhance the adhesion of the positive electrode active material. For example, it can be used in various forms such as film, sheet, foil, mesh, porous material, foam, and nonwoven fabric.

[0121] The positive electrode active material layer may include a conductive material and a binder, along with the positive electrode active material according to the present invention as described above.

[0122] The positive electrode active material may be present in an amount of 80 to 99% by weight, more specifically 85 to 98% by weight, relative to the total weight of the positive electrode active material layer, and when present within the above content range, it can exhibit excellent capacity characteristics.

[0123] The conductive material is used to impart conductivity to the electrodes and can be used without particular limitations in the battery it is configured in, as long as it does not cause chemical changes and has electronic conductivity. Specific examples include graphite such as natural graphite or artificial graphite; carbon-based materials such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, and carbon fiber; metal powders or metal fibers such as copper, nickel, aluminum, and silver; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives. Of these, one or more can be used. The conductive material can be included in an amount of 1 to 30% by weight relative to the total weight of the positive electrode active material layer.

[0124] The binder plays a role in improving the adhesion between positive electrode active material particles and the adhesion between the positive electrode active material and the current collector. Specific examples include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene-butadiene rubber (SBR), fluororubber, or various copolymers thereof, of which one or more can be used. The binder can be contained in an amount of 1 to 30% by weight relative to the total weight of the positive electrode active material layer.

[0125] The positive electrode can be manufactured by a conventional method for manufacturing a positive electrode, except that the positive electrode active material according to the present invention is used. Specifically, it can be manufactured by coating a positive electrode active material layer-forming composition, which is prepared by dissolving or dispersing the above-mentioned positive electrode active material and, selectively, a binder, a conductive material, and optionally, additives in a solvent, onto a positive electrode current collector, followed by drying and rolling. Here, the types and contents of the positive electrode active material, binder, and conductive material are as described above.

[0126] The solvent may be any solvent commonly used in the art, such as dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, or water, and one or more of these can be used individually or in mixtures of two or more. The amount of solvent used should be sufficient to dissolve or disperse the positive electrode active material, conductive material, and binder, taking into consideration the coating thickness of the slurry and the manufacturing yield, and to have a viscosity that allows for excellent thickness uniformity when applied for the manufacture of the positive electrode.

[0127] Alternatively, the positive electrode may be manufactured by casting the positive electrode active material layer forming composition onto another support, peeling it off the support, and then laminating the resulting film onto the positive electrode current collector.

[0128] Lithium-ion battery Furthermore, the present invention can be used to manufacture an electrochemical element including the positive electrode. Specifically, the electrochemical element may be a battery, a capacitor, or more specifically, a lithium secondary battery.

[0129] 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 and negative electrodes. The positive electrode is as described above, and its specific description is omitted. Below, only the remaining components will be described in detail.

[0130] Furthermore, the lithium secondary battery may selectively further include a battery container for housing the electrode assembly comprising the positive electrode, negative electrode, and separator, and a sealing member for sealing the battery container.

[0131] In the lithium secondary battery, the negative electrode includes a negative electrode current collector and a negative electrode active material layer located on the negative electrode current collector.

[0132] The negative electrode current collector is not particularly limited as long as it does not cause chemical changes in the battery and has high conductivity. For example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel with surface treatment using carbon, nickel, titanium, silver, etc., and aluminum-cadmium alloys can be used. The negative electrode current collector can usually have a thickness of 3 μm to 500 μm, and, similar to the positive electrode current collector, fine irregularities can be formed on the surface of the current collector to strengthen the bonding force of the negative electrode active material. For example, it can be used in various forms such as film, sheet, foil, mesh, porous material, foam, and nonwoven fabric.

[0133] The negative electrode active material layer may selectively include a binder and a conductive material together with the negative electrode active material.

[0134] As the negative electrode active material, compounds capable of reversible intercalation and deintercalation of lithium can be used. Specific examples include carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber, and amorphous carbon; metallic compounds capable of alloying with lithium, such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloys, Sn alloys, or Al alloys; and SiO2. β Examples include metallic oxides that can be doped and dedoped with lithium, such as (0<β<2), SnO2, vanadium oxide, and lithium vanadium oxide; or composites containing the metallic compound and carbonaceous material, such as Si-C composites or Sn-C composites; and any one or more mixtures thereof can be used. A metallic lithium thin film can also be used as the negative electrode active material. Furthermore, both low-crystallinity carbon and high-crystallinity carbon can be used as the carbon material. Examples of low-crystalline carbon include soft carbon and hard carbon, while examples of high-crystalline carbon include amorphous, plate-like, flaky, spherical, or fibrous natural or artificial graphite, Kish graphite, pyrolytic carbon, mesophase pitch-based carbon fiber, meso-carbon microbeads, mesophase pitches, and high-temperature calcined carbon such as petroleum or coal tar pitch-derived cokes.

[0135] The negative electrode active material can be included in an amount of 80 to 99 parts by weight per 100 parts by weight of the total weight of the negative electrode active material layer.

[0136] The binder is a component that helps to bond the conductive material, active material, and current collector, and is usually added in an amount of 0.1 to 10 parts by weight per 100 parts by weight of the total weight of the negative electrode active material layer. Examples of such binders include polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated EPDM, styrene-butadiene rubber, nitrile-butadiene rubber, fluororubber, and various copolymers thereof.

[0137] The conductive material is a component for further improving the conductivity of the negative electrode active material, and can be added in amounts of 10 parts by weight or less, preferably 5 parts by weight or less, per 100 parts by weight of the total weight of the negative electrode active material layer. Such a conductive material is not particularly limited as long as it does not cause a chemical change in the battery and is conductive, and examples of usable materials include graphite such as natural graphite and artificial graphite; carbon black such as acetylene black, Ketjen black, channel black, furnace black, lamp black, and thermal black; conductive fibers such as carbon fibers and metal fibers; carbon fluoride; metal powders such as aluminum and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives.

[0138] For example, the negative electrode active material layer can be manufactured by coating a negative electrode composite material, which is prepared by dissolving or dispersing a negative electrode active material and a binder and conductive material selectively in a solvent, onto a negative electrode current collector and then drying it, or by casting the negative electrode composite material onto another support, peeling it off this support, and then laminating the resulting film onto the negative electrode current collector.

[0139] On the other hand, in the lithium secondary battery, the separator separates the negative electrode and the positive electrode and provides a passage for lithium ions to move. Generally, any separator used in lithium secondary batteries can be used without particular limitations, but those with low resistance to ion movement of the electrolyte and excellent electrolyte impregnation ability are particularly preferred. Specifically, porous polymer films, such as porous polymer films made from polyolefin polymers like ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer, and ethylene / methacrylate copolymer, or laminated structures of two or more layers thereof, can be used. Ordinary porous nonwoven fabrics, such as nonwoven fabrics made from high-melting-point glass fibers or polyethylene terephthalate fibers, can also be used. Furthermore, coated separators containing ceramic components or polymeric substances can be used to ensure heat resistance or mechanical strength, and can be selectively used as single-layer or multi-layer structures.

[0140] Furthermore, the electrolytes used in the present invention include, but are not limited to, organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel-type polymer electrolytes, solid inorganic electrolytes, and molten inorganic electrolytes that can be used in the manufacture of lithium secondary batteries.

[0141] Specifically, the electrolyte may include an organic solvent and a lithium salt.

[0142] The organic solvent can be used without particular limitations, as long as it can act as a medium through which ions involved in the electrochemical reaction of the battery can move. Specifically, the organic solvents include ester solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, and ε-caprolactone; ether solvents such as dibutyl ether or tetrahydrofuran; ketone solvents such as cyclohexanone; aromatic hydrocarbon solvents such as benzene and fluorobenzene; dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), ethylene carbonate (EC), and propylene carbonate (propylene Carbonate solvents such as carbonate (PC); alcohol solvents such as ethyl alcohol and isopropyl alcohol; nitriles such as R-CN (where R is a linear, branched, or cyclic hydrocarbon group having 2 to 20 carbon atoms, and can include a double-bonded aromatic ring or ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; or sulfolanes can be used. Among these, carbonate solvents are preferred, and a mixture of a cyclic carbonate (e.g., ethylene carbonate or propylene carbonate) having high ionic conductivity and high dielectric constant that can improve the charge and discharge performance of the battery, and a low-viscosity linear carbonate compound (e.g., ethyl methyl carbonate, dimethyl carbonate, or diethyl carbonate) is more preferred. In this case, the cyclic carbonate and linear carbonate can be mixed in a volume ratio of about 1:1 to about 1:9 to produce an electrolyte with excellent performance.

[0143] The lithium salt can be used without particular limitations as long as it is a compound that can provide lithium ions for use in lithium secondary batteries. Specifically, the lithium salt can be LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAlO4, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2, LiCl, LiI, or LiB(C2O4)2, etc. The concentration of the lithium salt is preferably used within the range of 0.1 to 2.0 M. When the concentration of the lithium salt falls within this range, the electrolyte has appropriate conductivity and viscosity, so it can exhibit excellent electrolyte performance and lithium ions can move effectively.

[0144] In addition to the components of the electrolyte, the electrolyte may further contain one or more additives for purposes such as improving battery life characteristics, suppressing battery capacity reduction, and improving battery discharge capacity, such as haloalkylene carbonate compounds like difluoroethylene carbonate, pyridine, triethyl phosphite, triethanolamine, cyclic ethers, ethylenediamine, n-glyme, hexaphosphate triamide, nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinone, N,N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salts, pyrrole, 2-methoxyethanol, or aluminum trichloride. Here, the additive may be present in amounts of 0.1 to 5 parts by weight per 100 parts by weight of the total weight of the electrolyte.

[0145] As described above, lithium secondary batteries containing the positive electrode active material according to the present invention exhibit excellent discharge capacity, output characteristics, and life characteristics in a stable manner, making them useful in portable devices such as mobile phones, notebook computers, and digital cameras, as well as in the field of electric vehicles such as hybrid electric vehicles (HEVs).

[0146] Accordingly, according to another embodiment of the present invention, a battery module including the lithium secondary battery as a unit cell and a battery pack including the same are provided.

[0147] The aforementioned battery module or battery pack can be used as a power source for one or more medium-to-large devices, including power tools; electric vehicles (EVs), hybrid electric vehicles, and plug-in hybrid electric vehicles (PHEVs); or power storage systems.

[0148] The external shape of the lithium secondary battery of the present invention is not particularly limited, but may be cylindrical, rectangular, pouch-type, or coin-type using a can.

[0149] In addition to being usable as a battery cell for powering small devices, the lithium secondary battery according to the present invention can also be preferably used as a unit battery in medium- and large-sized battery modules containing a large number of battery cells.

[0150] The present invention will be described in detail below with reference to examples. However, the examples of the present invention can be modified into various other forms, and the scope of the present invention should not be construed as being limited to the examples detailed below. The examples of the present invention are provided to give a more complete explanation of the present invention to a person of average skill in the art.

[0151] Manufacturing example Manufacturing Example 1 NiSO4, CoSO4, and MnSO4 were mixed in water in amounts such that the molar ratio of nickel:cobalt:manganese was 88.5:3.5:8 to prepare a 2.4 M transition metal-containing solution, and a 25 wt% NaOH aqueous solution and a 9 wt% NH4OH aqueous solution were prepared.

[0152] After adding 5 L of deionized water to a 30 L reactor including a stirrer, nitrogen gas was purged into the reactor at a rate of 10 L / min to remove dissolved oxygen from the water and create a non-oxidizing atmosphere inside the reactor. Next, aqueous NaOH and aqueous NH4OH solutions were added to adjust the pH of the solution in the reactor to 12.0, and then the initial conditions were set so that the reactor temperature was 54°C and the stirring speed was 750 rpm.

[0153] A transition metal-containing solution was added to the reactor at a flow rate of 25 mL / min, an NH4OH aqueous solution at a flow rate of 8 mL / min, while an NaOH aqueous solution was added. The mixture was stirred for 1 hour at a stirring speed of 750 rpm to produce a seed mixture. The NaOH aqueous solution was added in such a way that the pH of the seed mixture was kept constant at pH 12.

[0154] Subsequently, a transition metal-containing solution was added to the seed mixture at a flow rate of 25 mL / min, an NH4OH aqueous solution at a flow rate of 8 mL / min, while simultaneously adding an NaOH aqueous solution. The mixture was stirred for 3 hours, gradually decreasing the stirring speed by 50 rpm per hour from 750 rpm to 600 rpm, and then maintained at a stirring speed of 600 rpm for 17 hours to produce a particle growth mixture with a particle size of 2.5 μm. Here, the NaOH aqueous solution was added so that the pH of the particle growth mixture was gradually decreased by 0.2 per hour from pH 12 to pH 11.4, and then added to maintain the pH of the particle growth mixture at a constant pH of 11.4.

[0155] Then, the transition metal-containing solution is added to the particle growth mixed solution at a flow rate of 32.5 mL / min, and while gradually increasing the flow rate of NH4OH aqueous solution from 8 mL / min to 11.375 mL / min, NaOH aqueous solution is added, and the mixture is stirred for 72 hours while maintaining a stirring speed of 600 rpm, and the average particle size (D) of the positive electrode active material precursor in the solution is determined. 50A mixed solution for the positive electrode active material precursor was prepared, having a particle size of 4.0 μm. Here, the transition metal-containing solution was added at a flow rate 1.3 times that of the flow rate used when preparing the particle growth mixed solution, the NH4OH aqueous solution was added at a gradually increasing flow rate so that it was 35% of the flow rate of the transition metal-containing solution, and the NaOH aqueous solution was added so that the pH of the mixed solution for the positive electrode active material precursor was kept constant at pH 11.4.

[0156] The mixed solution for the positive electrode active material precursor was filtered and dried to produce a positive electrode active material precursor with a lower internal density compared to the external density.

[0157] Manufacturing Example 2 NiSO4, CoSO4, and MnSO4 were mixed in water in amounts such that the molar ratio of nickel:cobalt:manganese was 88.5:3.5:8 to prepare a 2.4 M transition metal-containing solution, and a 25 wt% NaOH aqueous solution and a 9 wt% NH4OH aqueous solution were prepared.

[0158] After adding 5 L of deionized water to a 30 L reactor including a stirrer, nitrogen gas was purged into the reactor at a rate of 10 L / min to remove dissolved oxygen from the water and create a non-oxidizing atmosphere inside the reactor. Next, aqueous NaOH solution and aqueous NH4OH solution were added to adjust the pH of the solution in the reactor to 12.0, and then the initial conditions were set so that the reactor temperature was 54°C and the stirring speed was 800 rpm.

[0159] A transition metal-containing solution was added to the reactor at a flow rate of 25 mL / min, an NH4OH aqueous solution at a flow rate of 8 mL / min, while an NaOH aqueous solution was added. The mixture was stirred for 1 hour at a stirring speed of 800 rpm to produce a seed mixture. The NaOH aqueous solution was added in such a way that the pH of the seed mixture was kept constant at pH 12.

[0160] Subsequently, a transition metal-containing solution was added to the seed mixture at a flow rate of 25 mL / min, an NH4OH aqueous solution at a flow rate of 8 mL / min, while an NaOH aqueous solution was added. The stirring speed was gradually reduced by 40 rpm per hour from 800 rpm to 600 rpm for 5 hours, and then stirred for 25 hours while maintaining the stirring speed at 600 rpm to produce a particle growth mixture solution in which the particle size of the particles in the solution was 2.0 μm. Here, the NaOH aqueous solution was added so that the pH of the particle growth mixture solution was gradually reduced by 0.12 per hour from pH 12 to pH 11.4, and then added so that the pH of the particle growth mixture solution was maintained at a constant pH of 11.4.

[0161] Then, the transition metal-containing solution is added to the particle growth mixed solution at a flow rate of 32.5 mL / min, and while gradually increasing the flow rate of NH4OH aqueous solution from 8 mL / min to 10 mL / min, NaOH aqueous solution is added, and the mixture is stirred for 60 hours while maintaining a stirring speed of 600 rpm, and the average particle size (D) of the positive electrode active material precursor in the solution is determined. 50 A mixed solution for the positive electrode active material precursor was prepared, having a particle size of 4.0 μm. Here, the transition metal-containing solution was added at a flow rate 1.3 times that of the flow rate used when preparing the particle growth mixed solution, the NH4OH aqueous solution was added at a gradually increasing flow rate so that it was 30% of the flow rate of the transition metal-containing solution, and the NaOH aqueous solution was added so that the pH of the mixed solution for the positive electrode active material precursor was kept constant at pH 11.4.

[0162] The mixed solution for the positive electrode active material precursor was filtered and dried to produce a positive electrode active material precursor with a lower internal density compared to the external density.

[0163] Manufacturing Example 3 NiSO4, CoSO4, and MnSO4 were mixed in water in amounts such that the molar ratio of nickel:cobalt:manganese was 88.5:3.5:8 to prepare a 2.4 M transition metal-containing solution, and a 25 wt% NaOH aqueous solution and a 9 wt% NH4OH aqueous solution were prepared.

[0164] After adding 5 L of deionized water to a 30 L reactor including a stirrer, nitrogen gas was purged into the reactor at a rate of 10 L / min to remove dissolved oxygen from the water and create a non-oxidizing atmosphere inside the reactor. Next, aqueous NaOH solution and aqueous NH4OH solution were added to adjust the pH of the solution in the reactor to 12.0, and then the initial conditions were set so that the reactor temperature was 54°C and the stirring speed was 850 rpm.

[0165] A transition metal-containing solution was added to the reactor at a flow rate of 25 mL / min, an NH4OH aqueous solution at a flow rate of 8 mL / min, while an NaOH aqueous solution was added. The mixture was stirred for 1 hour at a stirring speed of 850 rpm to produce a seed mixture. The NaOH aqueous solution was added in such a way that the pH of the seed mixture was kept constant at pH 12.

[0166] Subsequently, a transition metal-containing solution was added to the seed mixture at a flow rate of 25 mL / min, an NH4OH aqueous solution at a flow rate of 8 mL / min, while simultaneously adding an NaOH aqueous solution. The mixture was stirred for approximately 6.25 hours, gradually decreasing the stirring speed from 850 rpm to 600 rpm by 40 rpm per hour, and then stirred for 23.75 hours while maintaining the stirring speed at 600 rpm, to produce a particle growth mixture with a particle size of 1.5 μm. Here, the NaOH aqueous solution was added so that the pH of the particle growth mixture was gradually decreased by 0.1 per hour from pH 12 to pH 11.4, and then added to maintain the pH of the particle growth mixture at a constant pH of 11.4.

[0167] Then, the transition metal-containing solution is added to the particle growth mixed solution at a flow rate of 32.5 mL / min, and while gradually increasing the flow rate of NH4OH aqueous solution from 8 mL / min to 8.125 mL / min, NaOH aqueous solution is added, and the mixture is stirred for 50 hours while maintaining a stirring speed of 600 rpm, and the average particle size (D) of the positive electrode active material precursor in the solution is determined. 50A mixed solution for the positive electrode active material precursor was prepared, having a particle size of 4.0 μm. Here, the transition metal-containing solution was added at a flow rate 1.3 times that of the flow rate used when preparing the particle growth mixed solution, the NH4OH aqueous solution was added at a gradually increasing flow rate so that it was 25% of the flow rate of the transition metal-containing solution, and the NaOH aqueous solution was added so that the pH of the mixed solution for the positive electrode active material precursor was kept constant at pH 11.4.

[0168] The mixed solution for the positive electrode active material precursor was filtered and dried to produce a positive electrode active material precursor with a lower internal density compared to the external density.

[0169] Manufacturing Example 4 NiSO4, CoSO4, and MnSO4 were mixed in water in amounts such that the molar ratio of nickel:cobalt:manganese was 88.5:3.5:8 to prepare a 2.4 M transition metal-containing solution, and a 25 wt% NaOH aqueous solution and a 9 wt% NH4OH aqueous solution were prepared.

[0170] After adding 5 L of deionized water to a 30 L reactor including a stirrer, nitrogen gas was purged into the reactor at a rate of 10 L / min to remove dissolved oxygen from the water and create a non-oxidizing atmosphere inside the reactor. Next, NaOH aqueous solution and NH4OH aqueous solution were added to adjust the pH of the solution in the reactor to 12.0, and then the initial conditions were set so that the reactor temperature was 54°C and the stirring speed was 700 rpm.

[0171] The transition metal-containing solution was initially added to the reactor at a flow rate of 35 mL / min for the first 10 seconds, then at a constant flow rate of 25 mL / min. While adding an aqueous NH4OH solution at a flow rate of 8 mL / min, an aqueous NaOH solution was added, and the mixture was stirred for 1 hour at a stirring speed of 700 rpm to produce a seed mixture. The aqueous NaOH solution was added in such a way that the pH of the seed mixture was kept constant at pH 12.

[0172] Subsequently, a transition metal-containing solution was added to the seed mixture at a flow rate of 25 mL / min, an NH4OH aqueous solution at a flow rate of 8 mL / min, while simultaneously adding an NaOH aqueous solution. The mixture was stirred for 3.3 hours, gradually decreasing the stirring speed from 700 rpm to 600 rpm by 30 rpm per hour, and then stirred for 16.7 hours while maintaining the stirring speed at 600 rpm, to produce a particle growth mixture with a particle size of 3.0 μm. Here, the NaOH aqueous solution was added so that the pH of the particle growth mixture was gradually decreased by 0.2 per hour from pH 12 to pH 11.4, and then added so that the pH of the particle growth mixture was maintained at a constant pH of 11.4.

[0173] Then, the transition metal-containing solution is added to the particle growth mixed solution at a flow rate of 32.5 mL / min, and while gradually increasing the flow rate of NH4OH aqueous solution from 8 mL / min to 13 mL / min, NaOH aqueous solution is added, and the mixture is stirred for 72 hours while maintaining a stirring speed of 600 rpm, and the average particle size of the positive electrode active material precursor in the solution is ( D50 A mixed solution for the positive electrode active material precursor was prepared, having a particle size of 4.0 μm. Here, the transition metal-containing solution was added at a flow rate 1.3 times that of the flow rate used when preparing the particle growth mixed solution, the NH4OH aqueous solution was added at a gradually increasing flow rate so that it was 40% of the flow rate of the transition metal-containing solution, and the NaOH aqueous solution was added so that the pH of the mixed solution for the positive electrode active material precursor was kept constant at pH 11.4.

[0174] The mixed solution for the positive electrode active material precursor was filtered and dried to produce a positive electrode active material precursor with a lower internal density compared to the external density.

[0175] Comparative Manufacturing Example 1 NiSO4, CoSO4, and MnSO4 were mixed in water in amounts such that the molar ratio of nickel:cobalt:manganese was 88.5:3.5:8 to prepare a 2.4 M transition metal-containing solution, and a 25 wt% NaOH aqueous solution and a 9 wt% NH4OH aqueous solution were prepared.

[0176] After adding 5 L of deionized water to a 30 L reactor including a stirrer, nitrogen gas was purged into the reactor at a rate of 10 L / min to remove dissolved oxygen from the water and create a non-oxidizing atmosphere inside the reactor. Next, aqueous NaOH solution and aqueous NH4OH solution were added to adjust the pH of the solution in the reactor to 12.0, and then the initial conditions were set so that the reactor temperature was 54°C and the stirring speed was 750 rpm.

[0177] The transition metal-containing solution was added to the reactor at a flow rate of 25 mL / min, followed by an NH4OH aqueous solution at a flow rate of 8 mL / min, while simultaneously adding an NaOH aqueous solution. The mixture was stirred for 100 hours at a stirring speed of 750 rpm, and the average particle size (D) of the positive electrode active material precursor in the solution was determined. 50 A mixed solution for the positive electrode active material precursor was prepared, having a particle size of 4.0 μm. Here, the NaOH aqueous solution was added so that the pH of the mixed solution for the positive electrode active material precursor was kept constant at pH 12.

[0178] The mixed solution for the positive electrode active material precursor was filtered and dried to produce a positive electrode active material precursor having the same internal and external density.

[0179] Comparative Manufacturing Example 2 NiSO4, CoSO4, and MnSO4 were mixed in water in amounts such that the molar ratio of nickel:cobalt:manganese was 88.5:3.5:8 to prepare a 2.4 M transition metal-containing solution, and a 25 wt% NaOH aqueous solution and a 9 wt% NH4OH aqueous solution were prepared.

[0180] After adding 5 L of deionized water to a 30 L reactor including a stirrer, nitrogen gas was purged into the reactor at a rate of 10 L / min to remove dissolved oxygen from the water and create a non-oxidizing atmosphere inside the reactor. Next, aqueous NaOH solution and aqueous NH4OH solution were added to adjust the pH of the solution in the reactor to 12.0, and then the initial conditions were set so that the reactor temperature was 54°C and the stirring speed was 950 rpm.

[0181] A transition metal-containing solution was added to the reactor at a flow rate of 25 mL / min, an NH4OH aqueous solution at a flow rate of 8 mL / min, while an NaOH aqueous solution was added. The mixture was stirred for 1 hour at a stirring speed of 950 rpm to produce a seed mixture. The NaOH aqueous solution was added in such a way that the pH of the seed mixture was kept constant at pH 12.2.

[0182] Subsequently, a transition metal-containing solution was added to the seed mixture at a flow rate of 25 mL / min, an NH4OH aqueous solution at a flow rate of 8 mL / min, while simultaneously adding an NaOH aqueous solution. The stirring was carried out for 7.9 hours, gradually decreasing the stirring speed from 950 rpm to 400 rpm by 70 rpm per hour, and then stirring was carried out for 42.1 hours while maintaining the stirring speed at 400 rpm, to determine the average particle size (D) of the seeds in the solution. 50 A mixed solution for particle growth was prepared, with a particle size of 1.0 μm. The NaOH aqueous solution was added to the mixed solution for particle growth at a rate of 0.1 per hour until the pH of the mixed solution for particle growth decreased from pH 12.2 to pH 11.4, and then added to maintain the pH of the mixed solution for particle growth at a constant pH of 11.4.

[0183] Then, the transition metal-containing solution is added to the particle growth mixed solution at a flow rate of 37.5 mL / min, and while gradually reducing the flow rate of NH4OH aqueous solution from 8 mL / min to 7.5 mL / min, NaOH aqueous solution is added, and the mixture is stirred for 35 hours while maintaining a stirring speed of 400 rpm, and the average particle size (D) of the positive electrode active material precursor in the solution is determined. 50 A mixed solution for the positive electrode active material precursor was prepared, having a particle size of 4.0 μm. Here, the transition metal-containing solution was added at a flow rate 1.5 times that of the flow rate used when preparing the particle growth mixed solution, the NH4OH aqueous solution was added at a flow rate that was gradually reduced to 20% of the flow rate of the transition metal-containing solution, and the NaOH aqueous solution was added in such a way that the pH of the mixed solution for the positive electrode active material precursor was kept constant at pH 11.4.

[0184] The mixed solution for the positive electrode active material precursor was filtered and dried to produce a positive electrode active material precursor with a higher internal density compared to the external density.

[0185] Example 1 A mixture was prepared by mixing the cathode active material precursor produced in Production Example 1 with LiOH in an alumina crucible so that the molar ratio of Li:(Ni+Co+Mn) was 1:1. The mixture was then subjected to primary calcination in an oxygen atmosphere at a temperature of 870°C for 5.5 hours to produce a primary calcined product.

[0186] The average particle size (D 50 ) is 4.0 μm, and the maximum particle size (D max The material was ground using a jet mill or pin mill to a particle size of 13.0 μm, and the ground primary calcined product was mixed with LiOH so that the total Li:(Ni+Co+Mn) molar ratio was 1.03:1. The mixture was then subjected to secondary calcination at a temperature of 790°C for 8 hours to produce a secondary calcined product. The average particle size (D) of the secondary calcined product was then measured. 50 ) is 4.0 μm, and the maximum particle size (D max The cathode active material was produced by grinding the material using a jet mill or pin mill until the particle size was 13.0 μm.

[0187] Example 2 The secondary calcined product (positive electrode active material) was manufactured in the same manner as in Example 1, except that the positive electrode active material precursor manufactured in Manufacturing Example 2 was used instead of the positive electrode active material precursor manufactured in Manufacturing Example 1.

[0188] Example 3 The secondary calcined product (positive electrode active material) was manufactured in the same manner as in Example 1, except that the positive electrode active material precursor manufactured in Manufacturing Example 3 was used instead of the positive electrode active material precursor manufactured in Manufacturing Example 1.

[0189] Example 4 The secondary calcined product (cathode active material) was manufactured in the same manner as in Example 1, except that the cathode active material precursor manufactured in Manufacturing Example 4 was used instead of the cathode active material precursor manufactured in Manufacturing Example 1.

[0190] Comparative Example 1 The secondary calcined product (positive electrode active material) was manufactured in the same manner as in Example 1, except that the positive electrode active material precursor manufactured in Comparative Manufacturing Example 1 was used instead of the positive electrode active material precursor manufactured in Manufacturing Example 1.

[0191] Comparative Example 2 The secondary calcined product (positive electrode active material) was manufactured in the same manner as in Example 1, except that the positive electrode active material precursor manufactured in Comparative Manufacturing Example 2 was used instead of the positive electrode active material precursor manufactured in Manufacturing Example 1.

[0192] Experimental Example 1: Analysis of Cathode Active Material Precursor The cathode active material precursors prepared in the above-mentioned production example and comparative production example, carbon black (DENKA, FX35), and a binder [a mixture of PVdF (Kureha, KF9709) and BM730H (Zeon) in a weight ratio of 6:1] were added to a solvent (N-methylpyrrolidone (NMP)) in a weight ratio of 83:10:7. The mixture was then stirred at 1,500 rpm for 95 minutes using a homogenizer (homogenizing disper model 2.5, Primix) to produce a cathode precursor slurry.

[0193] The positive electrode precursor slurry was coated onto one surface of an aluminum foil current collector, dried at 130°C for 3 hours, then cut using a cross-section cutting machine. A scanning electron microscope (QUANTA FEG 250, manufactured by FEI) was used to capture a SEM image of the cross-section of the positive electrode active material precursor, and the SEM image is shown in Figure 1.

[0194] Figure 1 shows SEM images of cross-sections of the cathode active material precursors produced in the production example and comparative production example. Specifically, (A) in Figure 1 is an SEM image of the cross-section of the cathode active material precursor produced in Production Example 1, (B) is an SEM image of the cross-section of the cathode active material precursor produced in Production Example 2, (C) is an SEM image of the cross-section of the cathode active material precursor produced in Production Example 3, (D) is an SEM image of the cross-section of the cathode active material precursor produced in Production Example 4, (E) is an SEM image of the cross-section of the cathode active material precursor produced in Comparative Production Example 1, and (F) is an SEM image of the cross-section of the cathode active material precursor produced in Comparative Production Example 2.

[0195] Referring to Figure 1, it was confirmed that the cathode active material precursors produced in production examples 1-4 had a higher density on the outside of the particles compared to the inside.

[0196] On the other hand, it was confirmed that the cathode active material precursor produced in comparative production example 1 had a similarly high density both inside and outside, while it was confirmed that the cathode active material precursor produced in comparative production example 2 had a lower density outside compared to inside.

[0197] Experimental Example 2: Analysis of Cathode Active Material Morphological analysis The positive electrode active materials prepared in the examples and comparative examples were each photographed using a scanning electron microscope (JEOL JSM-7900F, manufactured by JEOL), and SEM images were obtained.

[0198] Image analysis was performed on the aforementioned SEM images based on an artificial intelligence model to segment multiple primary particles and obtain segmentation images. The segmentation images of the cathode active materials produced in the examples and comparative examples are shown in Figures 2 to 7.

[0199] Figure 2 shows a segmentation image of the positive electrode active material produced in Example 1.

[0200] Figure 3 shows a segmentation image of the positive electrode active material produced in Example 2.

[0201] Figure 4 shows a segmentation image of the positive electrode active material produced in Example 3.

[0202] Figure 5 shows a segmentation image of the positive electrode active material produced in Example 4.

[0203] Figure 6 shows a segmentation image of the positive electrode active material produced in Comparative Example 1.

[0204] Figure 7 shows the segmentation image of the positive electrode active material produced in Comparative Example 2.

[0205] Referring to Figures 2 to 7, it was confirmed that the positive electrode active materials produced in the examples and comparative examples were in the form of single particles consisting of 30 or fewer primary particles. Furthermore, it was confirmed that the positive electrode active materials produced in Example 1 and Example 4 contained disk-type primary lithium composite transition metal oxides in an amount of 20% to 100% by volume relative to the total volume of the positive electrode active material.

[0206] Here, "disk-shaped" refers to primary particles observed from SEM images of the surface of the positive electrode active material, where, for two boundary lines of primary particles existing within an angle of 45° or less relative to the major axis, a virtual tangent line with the most points of contact is drawn for each boundary line, and when a virtual line is drawn crossing the two tangent lines, the ipsilateral interior angle is between 150° and 210°, and the aspect ratio (major axis / minor axis) is 1.5 or greater.

[0207] For reference, in Figures 2 to 5, when a hypothetical yellow tangent line with the most points of contact is drawn to two boundary lines of primary particles existing within an angle of 45° or less, using the red major axis direction as a reference, the one hypothetical line (not shown) that crosses the two yellow tangent lines satisfies the condition that the interior angle on the same side is between 150° and 210°. Primary particles that fall into this category are defined as disk-shaped primary particles.

[0208] Aspect ratio analysis From the SEM images of the positive electrode active material obtained by the morphological analysis described above, the long axis and short axis of the positive electrode active material produced in each example were analyzed and are shown in Figures 2 to 5 below. For reference, in Figures 2 to 5, the red arrows represent the short axis, the blue arrows represent the long axis, and the point of contact between the blue and red arrows represents the center of gravity of the primary particle. For reference, A shown in Figures 2 to 5 is the long axis (blue arrow), and B (red arrow) is the short axis.

[0209] Referring to Figures 2 to 5, it was confirmed that the first lithium composite transition metal oxide contained in the cathode active materials produced in Examples 1 to 4 consisted of disc-shaped primary particles with an aspect ratio of 1.5 or greater.

[0210] Analysis of volume ratio, degree of single particle formation, and average radius From the SEM images of the positive electrode active material obtained from the morphological analysis described above, the volume ratio and degree of single-particle formation (V) of each example and comparative example were determined. 50 ) and average radius (R 50 The following measurements were taken and are shown in Table 1 below.

[0211] Specifically, the area of ​​each primary particle is measured by the number of pixels corresponding to each of the n primary particles observed from the SEM image (measurement magnification 3,000x) taken on the surface of the positive electrode active material of the examples and comparative examples and projected onto a two-dimensional plane. Then, assuming that the surface of the primary particle is circular, the radius of the surface of the primary particle is derived using the radius of a circle having the same area as the surface area of ​​each primary particle.

[0212] Using the radius mentioned above, the volume is calculated using the following formula 1 to determine the total volume of the positive electrode active material and the total volume of the first lithium composite transition metal oxide. Then, the total volume of the first lithium composite transition metal oxide is divided by the total volume of the positive electrode active material and multiplied by 100 to calculate the volume ratio of the first lithium composite transition metal oxide (volume %), which is shown in Table 1 below. The single-particle degree (V) corresponding to the volume at the point where the cumulative volume distribution of primary particles reaches 50% is calculated. 50The radius (R) was measured and shown in Table 1 below, and the average radius (R) at the point where the cumulative radius distribution of the particles reaches 50% was measured. 50 The following measurements were taken and are shown in Table 1 below.

[0213]

number

[0214] Analysis of average particle size Using PSA (QUANTA FEG 250, manufactured by FEI), the average particle size (D) of each positive electrode active material produced in the examples and comparative examples was measured. 50 The following measurements were taken and are shown in Table 1 below.

[0215] [Table 1]

[0216] Referring to Table 1, in the case of positive electrode active materials manufactured in Examples 1 to 4, i.e., positive electrode active materials manufactured using positive electrode active material precursors with lower internal density compared to external density, it was confirmed that the first lithium composite transition metal oxide was contained in an amount of 20% to 100% by volume relative to the total volume of the positive electrode active material, and the degree of single particle formation (V 50 The point that the diameter is 1.2 μm or more and the average radius (R 50 We confirmed that the size of the particles was between 1 μm and 15 μm.

[0217] On the other hand, in the case of positive electrode active materials produced in Comparative Examples 1 and 2, i.e., positive electrode active materials produced using positive electrode active material precursors whose internal density is the same as or higher than the external density, it was confirmed that the first lithium composite transition metal oxide was contained in less than 20% by volume relative to the total volume of the positive electrode active material, and the degree of single particle formation (V 50 The point that the diameter is 1.2 μm or more and the average radius (R 50 We confirmed that the size of the particles was between 1 μm and 15 μm.

[0218] Experimental Example 3: Evaluation of Battery Characteristics Manufacturing of coin-type half-cells The cathode active materials, conductive material (FX35), and binder (a mixture of KF9700 and BM73OH in a weight ratio of 2.8:0.2) prepared in the examples and comparative examples were mixed in N-methyl-2-pyrrolidone (NMP) solvent in a weight ratio of 95:2:3 to prepare a cathode slurry.

[0219] The positive electrode slurry was applied to one surface of an aluminum current collector, dried at 130°C, and then rolled to a porosity of 20% to produce the positive electrode.

[0220] A lithium metal electrode (Li metal disk) was used as the negative electrode. An electrode assembly was manufactured by interposing a separator between the positive and negative electrodes. This assembly was then placed inside a battery case, and an electrolyte was injected into the case to manufacture a coin-type half-cell. The electrolyte used was an organic solvent mixture of ethylene carbonate, ethyl methyl carbonate, and diethyl carbonate in a volume ratio of 3:3:4, in which 1M LiPF6 was dissolved.

[0221] After manufacturing the coin-type half-cells, the batteries were evaluated using the following method.

[0222] Evaluation of capacity and output characteristics Each of the aforementioned coin-type half-cells was charged in CC / CV mode at 25°C with a constant current of 0.1C up to 4.25V (Cut-off current 0.05C), and then discharged in CC mode at a constant current of 0.1C until it reached 2.5V. The charging capacity (mAh / g) and discharging capacity (mAh / g) were measured during this process. The measured charging capacity (mAh / g) and discharging capacity (mAh / g) are shown in Table 2 below.

[0223] Evaluation of lifespan characteristics For each of the aforementioned coin-type half-cells, CC / CV mode charging was performed at 45°C with a constant current of 0.2C until the voltage reached 4.25V (Cut-off current 0.05C). This cycle was then repeated 30 times, with each cycle consisting of CC mode discharge at a constant current of 0.2C until the voltage reached 2.5V. The discharge capacity was measured for the first and 30th cycles. The percentage of the discharge capacity in the 30th cycle relative to the discharge capacity in the first cycle (capacity retention rate (%)) was calculated, and the results are shown in Table 2 below.

[0224] [Table 2]

[0225] Referring to Table 2, it was confirmed that in the case of batteries manufactured using a positive electrode active material containing 20% ​​to 100% by volume of single-particle type first lithium composite transition metal oxide consisting of 30 or fewer disk-shaped primary particles relative to the total volume of the positive electrode active material, as in Examples 1 to 4, the capacity retention rate at high temperatures was superior to that of batteries manufactured using a positive electrode active material containing less than 20% by volume of single-particle type first lithium composite transition metal oxide consisting of 30 or fewer disk-shaped primary particles relative to the total volume of the positive electrode active material, as in Comparative Examples 1 and 2.

[0226] On the other hand, in the case of batteries manufactured using Examples 1 to 3, i.e., batteries manufactured with a positive electrode active material containing 20% ​​to 70% by volume of single-particle type first lithium composite transition metal oxide relative to the total volume of the positive electrode active material, it was confirmed that the discharge capacity was larger compared to Example 4, i.e., batteries manufactured using a positive electrode active material containing more than 70% by volume of single-particle type first lithium composite transition metal oxide relative to the total volume of the positive electrode active material.

[0227] As a result, it was confirmed that a cathode active material containing a single-particle type first lithium composite transition metal oxide with 30 or fewer disk-shaped primary particles within a specific volume range has the effect of simultaneously improving both power characteristics and lifetime characteristics.

Claims

1. A positive electrode active material comprising a single-particle type first lithium composite transition metal oxide and, selectively, a single-particle type second lithium composite transition metal oxide, The aforementioned single-particle type first lithium composite transition metal oxide consists of 30 or fewer disk-type primary particles. The aforementioned disc-shaped primary particles are observed from SEM images of the surface or cross-section of the positive electrode active material. When two boundary lines of primary particles existing within an angle of 45° or less relative to the major axis are drawn, and a virtual tangent line with the most contact points is drawn for each boundary line, and a virtual line is drawn crossing the two tangent lines, the ipsilateral interior angle is 150° or more and 210° or less, and the aspect ratio (major axis / minor axis) is 1.5 or more. The positive electrode active material comprises the first lithium composite transition metal oxide in an amount of 20% to 100% by volume relative to the total volume of the positive electrode active material.

2. The positive electrode active material according to claim 1, wherein the positive electrode active material contains the first lithium composite transition metal oxide in an amount of 20% to 70% by volume relative to the total volume of the positive electrode active material.

3. The positive electrode active material according to claim 1, wherein the first lithium composite transition metal oxide has an aspect ratio (long axis / short axis) of 1.5 or more and 10 or less.

4. The first lithium composite transition metal oxide is such that, when the volume (V) value is calculated from the following formula 1 for each primary particle observed from an SEM image of the surface or cross-section of the positive electrode active material, the single-particle degree (V) corresponds to the volume at the point where the cumulative volume distribution of the primary particles reaches 50%. ５０ The positive electrode active material according to claim 1, wherein the diameter of the ) is 1.2 μm or more. [Math 1] In equation 1, radius is the radius of the surface or cross-section of the primary particle, assuming that the surface or cross-section of the primary particle observed from the SEM image (measurement magnification 3,000 times) is circular.

5. The first lithium composite transition metal oxide is such that when the radius is calculated for each primary particle observed from an SEM image (measurement magnification 3,000x) of the surface or cross-section of the positive electrode active material, the average radius (R) at the point where the cumulative radius distribution of the particles reaches 50% is obtained. ５０ ) is 1 μm or more and 15 μm or less, The positive electrode active material according to claim 1, wherein the radius is the radius of the surface or cross-section of the primary particle, assuming that the surface or cross-section of the primary particle is circular.

6. The positive electrode active material according to claim 1, wherein the first lithium composite transition metal oxide has a composition represented by the following chemical formula 1. [Chemical formula 1] Li ａ Ni ｘ Co ｙ M １ ｚ M ２ １－ｘ－ｙ－ｚ O ２ In the aforementioned chemical formula 1, M １ is one or more selected from the group consisting of Mn and Al, M ２ is one or more selected from the group consisting of B, Ba, Ce, Cr, F, Mg, V, Ti, Fe, Zr, Zn, Si, Y, Nb, Ga, Sn, Mo, W, P, S, Sr, Ta, La, and Hf. 0.9 ≤ a ≤ 1.3, 0.6 ≤ x < 1.0, 0 < y < 0.4, 0 < z < 0.4, and 0 ≤ 1 - x - y - z < 0.

4.

7. A positive electrode comprising the positive electrode active material according to any one of claims 1 to 6.

8. A lithium secondary battery comprising the positive electrode described in claim 7.

9. (A) A step of mixing a positive electrode active material precursor and a first lithium-containing raw material, the internal density of which is lower than the external density, to produce a mixture, A method for producing a positive electrode active material, comprising the steps of (B) primary calcining the mixture at a temperature of 800°C to 950°C to produce a primary calcined product, The interior is a region that corresponds to less than 50% of the radius from the center of the positive electrode active material precursor toward the outermost edge. A method for producing a positive electrode active material, wherein the positive electrode active material is in a single-particle form consisting of 30 or fewer primary particles and contains a disk-type first lithium composite transition metal oxide, and the first lithium composite transition metal oxide is contained in an amount of 20% to 100% by volume relative to the total volume of the positive electrode active material.

10. The method for producing a positive electrode active material according to claim 9, further comprising the step of grinding the primary calcined product immediately after the step of (B).

11. The method for producing a positive electrode active material according to claim 9, further comprising the step of (C) after step (B) above, mixing a second lithium-containing raw material with the primary calcined product, and then performing secondary calcination at a temperature of 680°C to 850°C to produce a secondary calcined product.

12. The method for producing a positive electrode active material according to claim 11, further comprising the step of grinding the secondary calcined product immediately after the step of (C).

13. The positive electrode active material precursor is (S1) A step of preparing a seed mixture by adding a transition metal-containing solution and an ammonium ion-containing solution at a predetermined flow rate to a reactor including a stirring device, adding a basic aqueous solution, and stirring while maintaining the stirring speed, (S2) A step of preparing a particle growth mixed solution by adding the transition metal-containing solution, the ammonium ion-containing solution, and the basic aqueous solution to the seed mixed solution, and stirring while gradually decreasing the stirring speed, (S3) Add the transition metal-containing solution to the particle growth mixed solution at a flow rate increased compared to step (S2), add the ammonium ion-containing solution at a gradually increasing flow rate, add the basic aqueous solution, and stir while maintaining the stirring speed to produce a mixed solution for the positive electrode active material precursor, the steps include: The method for producing a positive electrode active material according to claim 9, wherein the basic aqueous solution is added in such a way that the pH of the seed mixture is kept constant, the pH of the particle growth mixture is gradually decreased, and the pH of the positive electrode active material precursor mixture is kept constant.

14. The method for producing a positive electrode active material according to claim 13, wherein the basic aqueous solution is added so that the pH of the particle growth mixed solution gradually decreases from pH 12 to 13 to pH 11.2 to 12.

6.

15. The method for producing a positive electrode active material according to claim 13, wherein the (S2) step involves stirring while gradually decreasing the stirring speed from 700 rpm to 900 rpm to 500 rpm to 650 rpm.

16. The method for producing a positive electrode active material according to claim 13, wherein step (S3) involves adding the transition metal-containing solution at a flow rate of 1.2 to 1.4 times that of step (S2), and then adding the ammonium ion-containing solution at a flow rate that is gradually increased to 20% to 45% of the flow rate relative to the transition metal-containing solution.

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