Method for analyzing cathode active material precursor or cathode active material, and cathode active material precursor

Abstract

The present invention relates to a method for analyzing a cathode active material precursor or a cathode active material, comprising a step of calculating the movement distance (mobility) of lithium ions by using crystal structure information of particles and, specifically, to a method for analyzing a cathode active material precursor or a cathode active material, comprising a step of using Monte Carlo simulation to assign weights according to the degree of orientation from the crystal structure information of a cathode active material precursor or a cathode active material, and calculating the movement distance of lithium ions. In addition, the present invention relates to a cathode active material precursor derived using the analysis method and, specifically, to a cathode active material precursor which is in the form of a secondary particle formed by the aggregation of a plurality of primary particles, and which has a tortuosity, according to relation 2 described in the present specification, of greater than 1.0 and less than or equal to 8.0.

Description

Method for analyzing a cathode active material precursor or cathode active material, and cathode active material precursor

[0001] Cross-citation with related applications

[0002] This application claims the benefit of priority from Korean Patent Application No. 10-2024-0037381, filed March 18, 2024, the entire contents of which are incorporated herein by reference.

[0003] Technology field

[0004] The present invention relates to a method for analyzing a positive electrode active material precursor or a positive electrode active material using a Monte Carlo simulation method. Furthermore, the present invention relates to a positive electrode active material precursor derived using the above-described analysis method.

[0005]

[0006] With the recent technological development and increasing demand for mobile devices and electric vehicles, the demand for secondary batteries as an energy source is rapidly increasing. Among these secondary batteries, lithium secondary batteries, which boast high energy density and voltage, long cycle life, and low self-discharge rates, are commercialized and widely used.

[0007] Lithium transition metal oxides such as lithium cobalt oxide such as LiCoO2, lithium nickel oxide such as LiNiO2, lithium manganese oxide such as LiMnO2 or LiMn2O4, and lithium iron phosphate oxide such as LiFePO4 have been developed as positive electrode active materials for lithium secondary batteries, and recently, Li[Ni a Co b Mn c ]O2, Li[Ni a Co b Al c ]O2, Li[Ni a Co b Mn c Al d ] Lithium composite transition metal oxides containing two or more transition metals, such as O2, have been developed and are widely used.

[0008] Lithium composite transition metal oxides containing two or more transition metals developed to date are typically manufactured in the form of spherical secondary particles formed by agglomeration of tens to hundreds of primary particles. Depending on the orientation and shape (aspect ratio) of the primary particles, their physical properties, such as lithium ion mobility and electrolyte impregnation, vary. Accordingly, research is being conducted to control the particle structure of positive electrode active materials to improve their performance.

[0009] In this regard, it is known that it is advantageous to shorten the movement distance of lithium ions by forming the primary particle shape of the positive electrode active material precursor into a rod or columnar shape, or by forming the primary particles in a form in which they are arranged radially from the center of the secondary particle toward the surface. However, these morphological factors have the disadvantage of lacking crystal structure information and thus not accurately representing actual battery performance.

[0010] To complement these problems, XRD, which can confirm crystal structure information, is being utilized for analysis, but due to limitations in beam size, there are limitations in analyzing the crystal structure of micro-areas, and although quantitative analysis is known to be possible through the integral value of the diffraction peak, there is a disadvantage in that a comparable reference sample is required or additional measurement information (e.g., FT-IR data) is required.

[0011] Therefore, research is required on a method for analyzing the crystal structure of a cathode active material precursor that practically represents the performance of a battery.

[0012] In addition, it is necessary to identify a positive electrode active material precursor that can realize a positive electrode active material with excellent performance using a crystal structure analysis method.

[0013]

[0014] The present invention is intended to solve the above problems, and provides a method for analyzing a positive electrode active material precursor or a positive electrode active material, including a process for calculating the movement distance (mobility) of lithium ions by utilizing crystal structure information of particles.

[0015] In addition, the present invention aims to provide a positive electrode active material precursor having excellent performance derived by utilizing the above analysis method, specifically, a positive electrode active material having excellent life and life resistance characteristics, and a positive electrode active material precursor having optimal lithium mobility.

[0016]

[0017] The present invention provides a positive electrode active material precursor or a method for analyzing a positive electrode active material, and a positive electrode active material precursor.

[0018]

[0019] (1) The present invention provides a method for analyzing a positive electrode active material precursor or a positive electrode active material, including a step of calculating a movement distance of lithium ions by assigning a weight according to the degree of orientation from crystal structure information of the positive electrode active material precursor or a positive electrode active material using a Monte Carlo simulation method.

[0020] (2) The present invention provides a method for analyzing a positive electrode active material precursor or positive electrode active material in the above (1), wherein the positive electrode active material precursor or positive electrode active material is in the form of secondary particles formed by agglomeration of a plurality of primary particles.

[0021] (3) The present invention provides a method for analyzing a positive electrode active material precursor or positive electrode active material in (1) or (2), wherein the crystal structure information is obtained by analyzing a cross-sectional SEM image or cross-sectional TEM image of the positive electrode active material precursor or positive electrode active material, thereby quantifying the degree to which crystal grains are oriented from the center of the positive electrode active material precursor or positive electrode active material particles toward the surface.

[0022] (4) The present invention provides a method for analyzing a positive electrode active material precursor or positive electrode active material, wherein, in the above (3), the analysis of the cross-sectional SEM image or cross-sectional TEM image is performed using at least one selected from the group consisting of EBSD, TEM-ASTAR, and 4D-STEM.

[0023] (5) The present invention provides a method for analyzing a positive electrode active material precursor or positive electrode active material, wherein the degree of orientation is the degree to which crystal grains are oriented from the center of the positive electrode active material precursor or positive electrode active material particles toward the surface.

[0024] (6) The present invention provides a method for analyzing a positive electrode active material precursor or a positive electrode active material, wherein in any one of the above (1) to (5), the Monte Carlo simulation method comprises a process of generating and setting a random direction for a noise portion having no crystal direction inside a positive electrode active material precursor or a positive electrode active material particle, selecting an arbitrary point on the surface of the positive electrode active material precursor or a positive electrode active material particle and setting it as an initial position of lithium, and then calculating an energy change occurring when lithium ions move according to the following equation 1.

[0025] [Formula 1]

[0026] △E = s(∥r new ∥ - ∥r old ∥) - logf(d·c)

[0027] In the above equation 1, r old is the current position of lithium, r new is the test location where lithium will move, d is the direction of movement (i.e. r new - r old ), c is the c-axis direction of the crystal, and s(∥r new ∥ - ∥r old∥) term is the energy term that makes the particle move toward the center, and - logf(d·c) term is the energy term that makes it move more easily in the direction perpendicular to the c-axis, and s = 0.3, f = 0.01.

[0028] (7) The present invention is a secondary particle form formed by agglomeration of a plurality of primary particles,

[0029] A positive electrode active material precursor having a tortuosity value of greater than 1.0 and less than or equal to 8.0 according to the following equation 2 is provided.

[0030] [Formula 2]

[0031] Tortuosity = (distance traveled by lithium ions) / (straight-line distance from the outer shell to the center)

[0032] In the above equation 2, the movement distance of lithium ions is the distance that lithium ions actually move from any point on the surface of the positive electrode active material precursor particle to the center of the particle, and is obtained according to the analysis method according to claim 1, and the straight-line distance from the outer shell to the center is the straight-line distance from any point on the surface of the positive electrode active material precursor particle to the center of the particle.

[0033] (8) The present invention provides a positive electrode active material precursor having a tortuosity value of 5.0 to 8.0 according to the above formula 2 in (7).

[0034] (9) The present invention provides a positive electrode active material precursor according to (7) or (8), wherein the movement distance of the lithium ions is calculated through a method including a process of analyzing a cross-sectional SEM image or a cross-sectional TEM image of the positive electrode active material precursor by EBSD, TEM-ASTAR or 4D-STEM using a Monte Carlo simulation method, and assigning weights according to the degree to which the crystal grains are oriented from the center of the positive electrode active material precursor particle toward the surface, and the Monte Carlo simulation method includes a process of generating and setting a noise portion having no crystal direction inside the positive electrode active material precursor particle in a random direction, selecting an arbitrary point on the surface of the positive electrode active material precursor particle and setting it as the initial position of lithium, and then calculating the energy change that occurs when the lithium ions move according to the following Equation 1.

[0035] [Formula 1]

[0036] △E = s(∥r new ∥ - ∥r old ∥) - logf(d·c)

[0037] In the above equation 1, r old is the current position of lithium, r new is the test location where lithium will move, d is the direction of movement (i.e. r new - r old ), c is the c-axis direction of the crystal, and s(∥r new ∥ - ∥r old ∥) term is the energy term that makes the particle move toward the center, and - logf(d·c) term is the energy term that makes it move more easily in the direction perpendicular to the c-axis, and s = 0.3, f = 0.01.

[0038] (10) The present invention provides a positive electrode active material precursor having an average L value of 0.4 to 2.5 according to the following formula 3, in any one of the above (7) to (9).

[0039] [Formula 3]

[0040] L = (a-axis length of the grain) / (c-axis length of the grain)

[0041] In the above equation 3, the a-axis length of the crystal grain is the length of the longest axis among the a-axis direction vectors passing through the crystal grain, and the c-axis length of the crystal grain is the length of the longest axis among the c-axis direction vectors passing through the crystal grain.

[0042] (11) The present invention provides a positive electrode active material precursor comprising a composite transition metal hydroxide represented by the following chemical formula 1 in any one of the above (7) to (10).

[0043] [Chemical Formula 1]

[0044] Ni a Co b Mn c M d (OH)2

[0045] In the above chemical formula 1, M is at least one element selected from the group consisting of Al, W, Cu, Fe, V, Cr, Ti, Zr, Zn, Ta, Y, In, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Mg, B and Mo, and 0.6≤a<1.0, 0 <b<0.4, 0<c<0.4, 0≤d≤0.2이다.

[0046] (12) The present invention has a BET surface area of ​​3 m in any one of the above (7) to (11). 2 / g to 10m 2 / g provides a positive electrode active material precursor.

[0047] (13) The present invention relates to any one of the above (7) to (12), wherein the average particle diameter (D 50 ) provides a positive electrode active material precursor having a diameter of 4 μm to 15 μm.

[0048]

[0049] The analytical method according to the present invention utilizes crystal structure information of a positive electrode active material precursor or positive electrode active material particles to more realistically calculate the movement distance (mobility) of lithium ions, thereby easily identifying a precursor or positive electrode active material with optimal lithium mobility. Using the analytical method according to the present invention, battery performance can be predicted even before applying the precursor or positive electrode active material to the battery.

[0050] In addition, the positive electrode active material precursor according to the present invention is in the form of a secondary particle formed by agglomeration of a plurality of primary particles, and satisfies a tortuosity value of more than 1.0 and less than 8.0 according to Equation 2 described herein, thereby enabling the implementation of a positive electrode active material having optimal lithium mobility and excellent life and life resistance characteristics.

[0051]

[0052] Figure 1 is a diagram showing the definition of Euler angles.

[0053] Figure 2 is an image in which primary particles with the same crystal orientation are reconstructed in the same color using Euler angle information per pixel obtained by analyzing a cross-sectional SEM image of a positive electrode active material precursor in the form of a secondary particle using EBSD.

[0054] Figure 3 is an image visualized by calculating the angle between the straight line direction extending from the center to the surface of the positive electrode active material precursor particle in the form of a secondary particle and the c-axis direction vector.

[0055] Figure 4 is a graph showing the movement path and movement time of lithium ions derived using the Monte Carlo simulation method and the images of Sample 1 and Sample 2 visualized by calculating the angle between the straight line direction extending from the center of the positive electrode active material precursor particle in the form of secondary particles and the c-axis direction vector.

[0056]

[0057] Terms or words used in this specification and claims should not be interpreted as limited to their usual or dictionary meanings, but should be interpreted as meanings and concepts that conform to the technical idea of ​​the present invention, based on the principle that the inventor can appropriately define the concept of the term to explain his or her own invention in the best way.

[0058]

[0059] In the present invention, 'crystal grain' means a single crystal particle unit having a regular atomic arrangement.

[0060] In the present invention, the term "primary particle" refers to the smallest particle unit that can be distinguished as a single lump when observing a cross-section of a positive electrode active material through a scanning electron microscope (SEM), and may be composed of a single crystal grain or multiple crystal grains. In the present invention, the average particle diameter of the primary particle can be measured by a method of measuring the size of each particle distinguished in a cross-sectional SEM image of the positive electrode active material.

[0061] In the present invention, "secondary particle" refers to a secondary structure formed by the aggregation of multiple primary particles. The average particle diameter of the secondary particles can be measured using a particle size analyzer, and in the present invention, the particle size analyzer used was Microtrac's s3500.

[0062] In the present invention, the term 'positive electrode active material precursor particle' or 'positive electrode active material particle' refers to the secondary particle rather than the primary particle.

[0063]

[0064] Hereinafter, the present invention will be described in detail.

[0065] The present inventors have discovered that by utilizing the crystal structure information of a positive electrode active material precursor or positive electrode active material particles to more realistically calculate the movement distance (mobility) of lithium ions, a precursor or positive electrode active material having optimal lithium mobility can be easily identified, and thus the present invention has been completed.

[0066] In addition, the inventors of the present invention have conducted repeated research to develop a positive electrode active material precursor capable of implementing a positive electrode active material having an optimal lithium movement path within the particle and having improved lifespan and lifespan resistance characteristics, and as a result, they have found that when a plurality of primary particles are formed in the form of secondary particles and the tortuosity value according to Equation 2 described herein is greater than 1.0 and less than or equal to 8.0, the lifespan and lifespan resistance characteristics of a secondary battery can be improved, thereby completing the present invention.

[0067]

[0068] Method for analyzing a cathode active material precursor or cathode active material

[0069]

[0070] The analysis method according to the present invention includes a step of calculating the movement distance of lithium ions by assigning a weight according to the degree of orientation from the crystal structure information of a positive electrode active material precursor or positive electrode active material using a Monte Carlo simulation method.

[0071]

[0072] Hereinafter, the analysis method of the present invention will be described in detail.

[0073]

[0074] According to the present invention, the positive electrode active material precursor or positive electrode active material may be in the form of secondary particles formed by agglomeration of a plurality of primary particles. That is, the analysis method according to the present invention may be a method suitable for analyzing a positive electrode active material precursor or positive electrode active material in the form of secondary particles formed by agglomeration of a plurality of primary particles.

[0075]

[0076] According to the present invention, the crystal structure information may be obtained by analyzing a cross-sectional SEM image or a cross-sectional TEM image of a positive active material precursor or a positive active material, and quantifying the degree to which crystal grains are oriented from the center of the positive active material precursor or positive active material particles toward the surface. At this time, the cross-sectional SEM image or the cross-sectional TEM image may be obtained by analyzing a cross-section of the positive active material precursor or positive active material cut by an ion milling method or the like, using SEM or TEM. According to the present invention, the analysis of the cross-sectional SEM image or the cross-sectional TEM image may be performed using at least one selected from the group consisting of EBSD, TEM-ASTAR, and 4D-STEM. That is, the crystal structure information may be obtained by analyzing the cross-sectional SEM image or the cross-sectional TEM image by EBSD, TEM-ASTAR, and / or 4D-STEM, and quantifying the degree to which crystal grains are oriented from the center of the positive active material precursor or positive active material particles toward the surface.

[0077] According to the present invention, the degree of orientation may be the degree to which crystal grains are oriented from the center of the positive active material precursor or positive active material particles toward the surface.

[0078]

[0079] For example, the crystal structure information can be obtained by analyzing the cross-sectional SEM image or cross-sectional TEM image with EBSD, TEM-ASTAR, and / or 4D-STEM to obtain Euler angle information per pixel, reconstructing the image using the Euler angle information, clustering crystals, setting the center of the positive active material precursor or positive active material particles, and quantifying the degree to which the crystal grains are oriented in the surface direction from the center of the positive active material precursor or positive active material particles.

[0080] When crystal orientation analysis is performed on the cross-sectional SEM image or cross-sectional TEM image using EBSD, TEM-ASTAR, and / or 4D-STEM, the crystal orientation at each pixel in the two-dimensional image of the sample can be obtained as an Euler angle. The definition of each Euler angle follows the Bunge convention. Fig. 1 is a diagram showing the definition of the Euler angle. The equation for converting the Euler angle into a rotation matrix is ​​as follows, and the rotation matrix below is a matrix that converts the crystal coordinate system into the sample coordinate system.

[0081]

[0082] Since the c-axis vector of the crystal in the crystal coordinate system is [0, 0, 0]^T, the direction of the c-axis in the sample coordinate system is the same as the third column vector of the rotation matrix R. Therefore, the direction of the c-axis in the sample coordinate system is [sinφsinψ 1, -sinφcosψ1, cosφ]^T is calculated.

[0083] Since the transformed c-axis vector is a pixel-by-pixel value, a process of clustering pixels into grain-by-grain units is necessary to calculate grain-by-grain properties. Clustering is performed through the following process.

[0084] Using the DBSCAN algorithm, which is a type of clustering algorithm, the first clustering is performed on the c-axis vector under the conditions of parameters eps = 2 sin(0.5°) ~ 2 sin(1°) and minPts = 100 ~ 200, and the number of representative c-axis direction types n is obtained under the above conditions. Using the n obtained here, the second clustering is performed using the KMeans algorithm, which is a type of clustering algorithm (the number of clusters is fixed to n). As a result of the first and second clustering (angle clustering), clustering for the entire c-axis direction is completed. Since clustering was performed only in the c-axis direction, crystals existing in independent locations on the image are also clustered as the same crystal, and therefore additional clustering for location is required. DBSCAN is performed under the conditions of DBSCAN parameters eps = 3 and minPts = 1~3 for the pixel locations within each c-axis direction cluster of the first and second clustering to obtain clusters by location again (location clustering). The clusters that have gone through the above process are assumed to be primary particles, and the c-axis direction within the primary particles is reset to the average direction of the c-axis directions of the pixels contained in the primary particles. This allows for the segmentation of the primary particles and their c-axis directions to be obtained. Note that clusters with a pixel area of ​​8 or less are removed for noise removal.

[0085] In the above process, the cluster number (crystal grain number) of each pixel in the data and the direction vector c per crystal grain are obtained.

[0086] Figure 2 is an image in which primary particles with the same crystal orientation are reconstructed in the same color using Euler angle information per pixel obtained by analyzing a cross-sectional SEM image of a positive electrode active material precursor in the form of a secondary particle using EBSD.

[0087] And, Fig. 3 is an image visualized by calculating the angle between the straight line direction (hereinafter, r direction) extending from the center (center of gravity) of the positive electrode active material precursor particle in the form of a secondary particle to the surface and the c-axis direction vector. That is, Fig. 3 is the result of obtaining crystal structure information by setting the center of the positive electrode active material precursor particle in the form of a secondary particle and quantifying the degree to which the crystal grains are oriented from the center of the particle toward the surface. In Fig. 3, when the angle between the r direction and the c-axis direction vector increases from 0° to 90° (purple->yellow), a lithium ion path is formed between the plates, so that the mobility of lithium ions is good, and when the angle decreases, the mobility of lithium ions is low. For reference, as shown in Fig. 3, even in one crystal with the same crystal direction, the angles between the r direction and the c-axis direction vector are all different, so that there may be a color difference even within the same crystal.

[0088]

[0089] The Monte Carlo simulation method is a method of obtaining a desired value through repeated random sampling.

[0090] According to the present invention, a method of assigning a weight according to the degree of orientation from crystal structure information of a positive electrode active material precursor or a positive electrode active material using the Monte Carlo simulation method may include a process of generating and setting a random direction for a noise portion having no crystal direction inside a positive electrode active material precursor or a positive electrode active material particle, selecting an arbitrary point on the surface of the positive electrode active material precursor or a positive electrode active material particle and setting it as the initial position of lithium, and then calculating the energy change occurring when lithium ions move according to the following equation 1.

[0091] [Formula 1]

[0092] △E = s(∥r new ∥ - ∥r old ∥) - logf(d·c)

[0093] In the above equation 1, rold is the current position of lithium, r new is the test location where lithium will move, d is the direction of movement (i.e. r new - r old ), c is the c-axis direction of the crystal, and s(∥r new ∥ - ∥r old ∥) term is the energy term that makes the particle move toward the center, and - logf(d·c) term is the energy term that makes it move more easily in the direction perpendicular to the c-axis, and s = 0.3, f = 0.01.

[0094]

[0095] Specifically, the Monte Carlo simulation method may be as follows.

[0096] The noise portion without a crystal direction within the particle was set by generating a random direction, and a random point on the particle surface was selected and set as the initial position of lithium. The energy change that occurs when lithium ions move is calculated according to Equation 1 above. At this time, the origin of the coordinate axis is the center of the particle.

[0097] In the present invention, the values ​​of s = 0.3 and f = 0.01 were used, but any arbitrary value can be set. For reference, the setting standard of f = 0.01 assumes that lithium can move 100 times faster in the vertical direction of the c-axis.

[0098] Lithium's movement is randomly selected from eight directions from its current position, and if exp(-△E) < U[0,1] in the new direction, the movement is accepted. By storing the index and movement path of each trial, the speed and time can be calculated. The time is the maximum value of the trial index, and the speed is (center position - starting position) / time.

[0099] The above process is calculated from various starting points to calculate statistical properties as shown in the graph in Fig. 4.

[0100] Figure 4 is a graph showing the movement path and movement time of lithium ions derived using the Monte Carlo simulation method, along with images of Sample 1 and Sample 2, which are visualized by calculating the angle between the straight line direction extending from the center to the surface of the positive electrode active material precursor particles in the form of secondary particles and the c-axis direction vector. Since one Monte Carlo step can move one pixel (including the diagonal direction), the movement time of the lithium ions is the number of Monte Carlo steps until they reach the center.

[0101] In the images of Sample 1 and Sample 2 in Fig. 4, the red dot in the middle is the center of the positive electrode precursor particle, and the red dots on the surface of the positive electrode precursor particle are random points on the boundary of the positive electrode precursor particle image.

[0102] Referring to Fig. 4, it can be confirmed through the simulation results that sample 2 has excellent lithium mobility.

[0103]

[0104] In conclusion, the analytical method of the present invention utilizes crystal structure information of a positive electrode active material precursor or positive electrode active material particles to more realistically estimate the migration distance (mobility) of lithium ions, thereby easily identifying a precursor or positive electrode active material with optimal lithium mobility. Furthermore, utilizing the analytical method of the present invention allows for predicting battery performance even before applying the precursor or positive electrode active material to the battery.

[0105]

[0106] Cathode active material precursor

[0107]

[0108] The positive electrode active material precursor according to the present invention is in the form of a secondary particle formed by agglomeration of a plurality of primary particles, and is characterized by having a tortuosity value of more than 1.0 and less than or equal to 8.0 according to the following equation 2.

[0109] [Formula 2]

[0110] Tortuosity = (distance traveled by lithium ions) / (straight-line distance from the outer shell to the center)

[0111] In the above equation 2, the distance traveled by lithium ions is the distance actually traveled by lithium ions from any point on the surface of the positive electrode active material precursor particle to the center of the particle, and is obtained by the analysis method according to the present invention, and the straight-line distance from the outer shell to the center is the straight-line distance from any point on the surface of the positive electrode active material precursor particle to the center of the particle.

[0112] The tortuosity value according to the above equation 2 is a value obtained by dividing the distance that lithium ions actually move from any point on the surface of a positive electrode precursor particle to the center of the particle (the distance that lithium ions move) by the straight-line distance from any point on the surface of the positive electrode precursor particle to the center of the particle (the straight-line distance from the outer shell to the center). The lower limit of the tortuosity value is 1.0. When the tortuosity value is greater than 1.0 and less than or equal to 8.0, it means that the optimal movement path for lithium ions on the surface of the precursor particle to move to the center of the particle is secured. When the tortuosity value is greater than 1.0 and less than or equal to 8.0, the optimal lithium movement path within the particle is secured, thereby improving structural stability during charge and discharge, and thus implementing a positive electrode active material having excellent life and life resistance characteristics.

[0113] According to the present invention, the tortuosity value according to the above formula 2 may be greater than 1.0, greater than 2.0, greater than 3.0, greater than 4.0, or greater than 5.0, and may be less than or equal to 8.0. Specifically, the tortuosity value according to the above formula 2 may be from 5.0 to 8.0.

[0114] Meanwhile, a case where the twist value is 1.0 is an ideal case and cannot exist in reality, and a case where the twist value exceeds 8.0 does not secure a path for lithium movement, so there is a problem that the life and life resistance characteristics of the positive electrode active material manufactured from it are poor.

[0115]

[0116] According to the present invention, the movement distance of the lithium ions is calculated through a method including a process of analyzing a cross-sectional SEM image or a cross-sectional TEM image of a positive electrode active material precursor using EBSD, TEM-ASTAR or 4D-STEM using a Monte Carlo simulation method, and assigning weights according to the degree to which crystal grains are oriented from the center of the positive electrode active material precursor particles toward the surface (assigning weights according to the degree of orientation from crystal structure information). At this time, the cross-sectional SEM image or cross-sectional TEM image can be obtained by analyzing a cross-section of the positive electrode precursor cut by an ion milling method or the like using SEM or TEM.

[0117] In addition, the Monte Carlo simulation method includes a process of generating and setting a random direction for a noise portion having no crystal direction inside a positive electrode precursor particle, selecting an arbitrary point on the surface of the positive electrode precursor particle and setting it as the initial position of lithium, and then calculating the energy change that occurs when lithium ions move according to the following equation 1.

[0118] [Formula 1]

[0119] △E = s(∥r new ∥ - ∥r old ∥) - logf(d·c)

[0120] In the above equation 1, r old is the current position of lithium, r new is the test location where lithium will move, d is the direction of movement (i.e. r new - r old ), c is the c-axis direction of the crystal, and s(∥r new∥ - ∥r old ∥) term is the energy term that makes the particle move toward the center, and - logf(d·c) term is the energy term that makes it move more easily in the direction perpendicular to the c-axis, and s = 0.3, f = 0.01.

[0121]

[0122] The above-described positive electrode active material precursor may have an average L value of 0.4 to 2.5 according to the following equation 3. In this case, a positive electrode active material having an optimal lithium migration path and improved orientation characteristics with structural stability during charge and discharge can be realized.

[0123] [Formula 3]

[0124] L = (a-axis length of the grain) / (c-axis length of the grain)

[0125] In the above equation 3, the a-axis length of the crystal grain is the length of the longest axis among the a-axis direction vectors passing through the crystal grain, and the c-axis length of the crystal grain is the length of the longest axis among the c-axis direction vectors passing through the crystal grain.

[0126] The above (a-axis length of crystal grain) / (c-axis length of crystal grain) is different from the (major axis / minor axis) defined from the shape of the particle, and even if the particle has a long shape, the (a-axis length of crystal grain) / (c-axis length of crystal grain) value may be low.

[0127]

[0128] According to the present invention, the positive electrode active material precursor may include a composite transition metal hydroxide containing two or more transition metals, and may include, for example, a composite transition metal hydroxide represented by the following chemical formula 1.

[0129] [Chemical Formula 1]

[0130] Ni a Co b Mn c M d (OH)2

[0131] In the above chemical formula 1, M is at least one element selected from the group consisting of Al, W, Cu, Fe, V, Cr, Ti, Zr, Zn, Ta, Y, In, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Mg, B and Mo, and 0.6≤a<1.0, 0 <b<0.4, 0<c<0.4, 0≤d≤0.2이다.

[0132] The above a represents the ratio of the number of moles of Ni to the total number of moles of transition metal, and may be 0.6≤a<1, preferably 0.8≤a<1.

[0133] The above b represents the ratio of the moles of Co to the total moles of transition metals, 0 <b<0.4, 바람직하게는 0<b<0.2일 수 있다.

[0134] The above c represents the mole ratio of Mn to the total mole number of transition metals, 0 <c<0.4, 바람직하게는 0<c<0.2일 수 있다.

[0135] The above d represents the ratio of the number of moles of M to the total number of moles of transition metal, and may be 0≤d≤0.2, preferably 0≤d≤0.15, and more preferably 0≤d≤0.10.

[0136]

[0137] According to the present invention, the positive electrode active material precursor has a BET specific surface area of ​​3 m 2 / g to 10m 2 / g. When the BET specific surface area of ​​the positive electrode active material precursor is within the above range, the reactivity with lithium during firing is good, so that the efficiency (reduction in firing temperature / time) in the firing process is increased, and a positive electrode active material with improved orientation and structural stability during charge / discharge can be realized with an optimal lithium movement path.

[0138]

[0139] According to the present invention, the positive electrode active material precursor has an average particle diameter (D 50 ) may be 4㎛ to 15㎛. The average particle diameter (D) of the positive electrode active material precursor50 ) is the average particle diameter of the secondary particles, and specifically, it may be 4.0㎛ or more and 15.0㎛ or less. The average particle diameter (D) of the positive electrode active material precursor 50 ) is within the above range, the size ratio of the external surface area of ​​the positive electrode active material where a side reaction occurs within the electrode and the internal size of the positive electrode active material where lithium ion movement is relatively slow compared to the electrolyte is appropriate, so that a battery having advantageous life and life resistance characteristics can be implemented.

[0140]

[0141] positive electrode active material

[0142] The present invention provides a cathode active material that is a sintered product of a mixture of the cathode active material precursor and a lithium raw material. That is, the cathode active material can be manufactured by mixing the cathode active material precursor according to the present invention with a lithium raw material and then sintering it. In addition, the cathode active material can be manufactured from the cathode active material precursor according to the present invention, thereby realizing a cathode active material with improved orientation that has an optimal lithium migration path and structural stability during charge and discharge.

[0143]

[0144] Examples of the lithium raw material include lithium-containing carbonates (e.g., lithium carbonate, etc.), hydrates (e.g., lithium hydroxide hydrate (LiOH·H2O)), hydroxides (e.g., lithium hydroxide, etc.), nitrates (e.g., lithium nitrate (LiNO3)), chlorides (e.g., lithium chloride (LiCl)), etc., and one of these may be used alone or a mixture of two or more may be used.

[0145] Meanwhile, the mixing of the positive electrode active material precursor and the lithium raw material may be performed by solid-state mixing, and the mixing ratio of the positive electrode active material precursor and the lithium raw material may be determined in a range that satisfies the atomic fraction of each component in the positive electrode active material to be finally manufactured. For example, the positive electrode active material precursor and the lithium raw material may be mixed in an amount such that the molar ratio of the transition metal:Li contained in the positive electrode active material precursor is 1:0.9 to 1:1.2, preferably 1:0.98 to 1:1.1. When the positive electrode active material precursor and the lithium raw material are mixed in the above range, a positive electrode active material exhibiting excellent capacity characteristics can be manufactured.

[0146] The above firing can be performed at 600°C to 1000°C, preferably 700°C to 900°C, and the firing time can be 5 hours to 30 hours, preferably 10 hours to 20 hours, but is not limited thereto.

[0147]

[0148] The above positive electrode active material has an average particle diameter (D 50 ) may be 2.0㎛ to 20.0㎛.

[0149] The above positive electrode active material may have a composition represented by the following chemical formula 2.

[0150] [Chemical Formula 2]

[0151] Li x [Ni a2 Co b2 Mn c2 M d2 ]O2

[0152] In the above chemical formula 2,

[0153] M is one or more elements selected from the group consisting of Al, W, Cu, Fe, V, Cr, Ti, Zr, Zn, Ta, Y, In, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Mg, B, and Mo,

[0154] 0.9≤x≤1.2, 0.6≤a2<1.0, 0 <b2<0.4, 0<c2<0.4, 0≤d2≤0.2이다.

[0155]

[0156] anode

[0157] The present invention provides a positive electrode comprising the positive electrode active material.

[0158] The positive electrode may include a positive electrode current collector and a positive electrode active material layer formed on the positive electrode current collector, and the positive electrode active material layer may include the positive electrode active material.

[0159] The positive electrode current collector may include a highly conductive metal, and is not particularly limited as long as it is easily adhered to by the positive electrode active material layer and does not react within the voltage range of the battery. The positive electrode current collector may be made of, for example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, etc. In addition, the positive electrode current collector may typically have a thickness of 3 ㎛ to 500 ㎛, and fine unevenness may be formed on the surface of the current collector to increase the adhesion of the positive electrode active material. For example, the positive electrode current collector may be used in various forms such as a film, a sheet, a foil, a net, a porous body, a foam, a non-woven fabric, etc.

[0160] The above-mentioned positive electrode active material layer may optionally include a conductive material and a binder, together with the positive electrode active material, as needed. In this case, the positive electrode active material may be included in an amount of 80 wt% to 99 wt%, more specifically 85 wt% to 98.5 wt%, based on the total weight of the positive electrode active material layer, and excellent capacity characteristics may be exhibited within this range.

[0161] The conductive material is used to provide conductivity to the electrode, and in the battery to be formed, as long as it does not cause a chemical change and has electronic conductivity, it can be used without any special restrictions. Specific examples include graphite such as natural graphite or artificial graphite; carbon-based materials such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, and carbon fiber; metal powders or metal fibers such as copper, nickel, aluminum, and silver; conductive tubes such as carbon nanotubes; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives, and the like. One of these may be used alone or a mixture of two or more may be used. The conductive material may be included in an amount of 0.1 wt% to 15 wt% based on the total weight of the positive electrode active material layer.

[0162] The above binder serves to improve the adhesion between positive electrode active material particles and the adhesion between the positive electrode active material and the current collector. Specific examples include polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylalcohol, polyacrylonitrile, polymethyl methacrylate, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene butadiene rubber (SBR), fluoroelastomer, polyacrylic acid, and polymers in which hydrogens of these are substituted with Li, Na, or Ca, or various copolymers thereof, and one of these may be used alone or a mixture of two or more thereof. The above binder may be included in an amount of 0.1 wt% to 15 wt% based on the total weight of the positive electrode active material layer.

[0163] The positive electrode can be manufactured according to a conventional positive electrode manufacturing method, except that the positive electrode active material described above is used. Specifically, the positive electrode can be manufactured by applying a composition for forming a positive electrode active material layer, which is manufactured by dissolving or dispersing the positive electrode active material and optionally a binder, a conductive agent, and a dispersant in a solvent as needed, onto a positive electrode current collector, followed by drying and rolling, or by casting the composition for forming a positive electrode active material layer onto a separate support, peeling the film from the support, and laminating the resulting film onto a positive electrode current collector.

[0164] The solvent may be a solvent generally used in the relevant technical field, such as dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), dimethylformamide (DMF), acetone, or water. One of these may be used alone or a mixture of two or more thereof may be used. The amount of the solvent used is sufficient to dissolve or disperse the positive electrode active material, conductive material, binder, and dispersant in consideration of the coating thickness and manufacturing yield of the slurry, and to have a viscosity that can exhibit excellent thickness uniformity when applied thereafter for manufacturing the positive electrode.

[0165]

[0166] lithium secondary battery

[0167] The present invention provides a lithium secondary battery comprising: the positive electrode; the negative electrode; a separator interposed between the positive electrode and the negative electrode; and an electrolyte.

[0168]

[0169] The above lithium secondary battery may optionally further include a battery container that houses the electrode assembly of the positive electrode, negative electrode, and separator, and a sealing member that seals the battery container.

[0170]

[0171] The above negative electrode may include a negative electrode current collector and a negative electrode active material layer positioned on the negative electrode current collector.

[0172] The negative electrode current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery, and for example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., aluminum-cadmium alloy, etc. can be used. In addition, the negative electrode current collector can typically have a thickness of 3 ㎛ to 500 ㎛, and like the positive electrode current collector, fine unevenness can be formed on the surface of the current collector to strengthen the bonding strength of the negative electrode active material. For example, it can be used in various forms such as a film, a sheet, a foil, a net, a porous body, a foam, a non-woven fabric, etc.

[0173] The above negative electrode active material layer may optionally include a binder and a conductive material together with the negative electrode active material.

[0174] As the negative electrode active material, a compound capable of reversible intercalation and deintercalation of lithium may be used. Specific examples include carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber, and amorphous carbon; metallic compounds capable of alloying with lithium such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloy, Sn alloy, or Al alloy; SiO β(0<β<2), SnO2, vanadium oxide, lithium vanadium oxide, and other metal oxides capable of doping and dedoping lithium; or composites containing the above metallic compounds and carbonaceous materials, such as Si-C composites or Sn-C composites, and any one or a mixture of two or more of these may be used. In addition, a metallic lithium thin film may be used as the negative electrode active material. In addition, both low-crystalline carbon and high-crystalline carbon may be used as the carbonaceous material. Representative examples of low-crystalline carbon include soft carbon and hard carbon, and representative examples of high-crystalline carbon include natural graphite or artificial graphite in the form of amorphous, plate-like, flaky, spherical or fibrous shapes, 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. The negative electrode active material may be included in an amount of 80 wt% to 99 wt% based on the total weight of the negative electrode active material layer.

[0175] The binder of the above-described negative electrode active material layer is a component that assists in bonding between the conductive material, the active material, and the current collector, and is typically added in an amount of 0.1 wt% to 10 wt% based on the total weight of the negative electrode active material layer. Examples of such binders include polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene-butadiene rubber, nitrile-butadiene rubber, fluororubber, and various copolymers thereof.

[0176] The conductive material of the above-described negative electrode active material layer is a component for further improving the conductivity of the negative electrode active material, and may be added in an amount of 10 wt% or less, preferably 5 wt% or less, based on the total weight of the negative electrode active material layer. The conductive material is not particularly limited as long as it has conductivity without causing a chemical change in the battery, and examples thereof include graphite such as natural graphite or artificial graphite; carbon black such as acetylene black, Ketjen black, channel black, furnace black, lamp black, and thermal black; conductive fibers such as carbon fiber or metal fiber; fluorinated carbon; metal powder such as aluminum or nickel powder; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives.

[0177] The above negative electrode can be manufactured by applying and drying a composition for forming a negative electrode active material layer prepared by dissolving or dispersing a negative electrode active material, and optionally a binder and a conductive material in a solvent, on a negative electrode current collector, or by casting the composition for forming a negative electrode active material layer on a separate support, and then laminating the film obtained by peeling it off from the support on a negative electrode current collector.

[0178] The above separator separates the negative electrode and the positive electrode and provides a passage for lithium ions to move. Any separator commonly used in lithium secondary batteries can be used without any particular restrictions, and in particular, one having low resistance to ion movement of the electrolyte and excellent electrolyte moisture retention capacity is preferable. Specifically, a porous polymer film, for example, a porous polymer film made of a polyolefin polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, and an ethylene / methacrylate copolymer, or a laminated structure of two or more layers thereof, may be used. In addition, a conventional porous nonwoven fabric, for example, a nonwoven fabric made of high-melting-point glass fiber, polyethylene terephthalate fiber, etc. may also be used. In addition, a coated separator containing a ceramic component or a polymer material to secure heat resistance or mechanical strength may be used, and may optionally be used in a single-layer or multi-layer structure.

[0179] Examples of the electrolyte 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. As a specific example, the electrolyte may include an organic solvent and a lithium salt.

[0180] As the organic solvent, any solvent that can serve as a medium through which ions involved in the electrochemical reaction of the battery can move may be used without particular limitation. Specifically, the organic solvent includes ester solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, and ε-caprolactone; ether solvents such as dibutyl ether or tetrahydrofuran; ketone solvents such as cyclohexanone; aromatic hydrocarbon solvents such as benzene and fluorobenzene; carbonate solvents such as dimethylcarbonate (DMC), diethylcarbonate (DEC), ethylmethylcarbonate (EMC), ethylenecarbonate (EC), and propylene carbonate (PC); Alcohol solvents such as ethyl alcohol, isopropyl alcohol, etc.; nitriles such as R-CN (R is a linear, branched, or cyclic hydrocarbon group having 2 to 20 carbon atoms and may include a double-bonded aromatic ring or an ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; or sulfolanes, etc. can be used. Among these, carbonate solvents are preferable, 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 / discharge performance of a battery and a low-viscosity linear carbonate compound (e.g., ethyl methyl carbonate, dimethyl carbonate, or diethyl carbonate) is more preferable.

[0181] The above lithium salt can be used without any special limitation as long as it is a compound that can provide lithium ions used in a lithium secondary battery. Specifically, the anion of the above lithium salt is F - , Cl - , Br - , I - , NO3 - , N(CN)2 - , BF4 - , CF3CF2SO3 - , (CF3SO2)2N - , (FSO2)2N - , CF3CF2(CF3)2CO - , (CF3SO2)2CH - , (SF5)3C - , (CF3SO2)3C - , CF3(CF2)7SO3 - , CF3CO2 - , CH3CO2 - , SCN - and (CF3CF2SO2)2N - At least one selected from the group consisting of may be used, and the lithium salt may be LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAl04, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2, LiCl, LiI, or LiB(C2O4)2. It is preferable to use the concentration of the lithium salt within the range of 0.1 M to 2.0 M. When the concentration of the lithium salt is within the above range, the electrolyte can exhibit excellent electrolyte performance because it has appropriate conductivity and viscosity, and lithium ions can move effectively.

[0182] In addition to the electrolyte components, the electrolyte may further include one or more additives, such as haloalkylene carbonate compounds such as difluoroethylene carbonate, pyridine, triethylphosphite, triethanolamine, cyclic ethers, ethylene diamine, n-glyme, hexaphosphoric acid triamide, nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinones, N,N-substituted imidazolidines, ethylene glycol dialkyl ethers, ammonium salts, pyrrole, 2-methoxyethanol, or aluminum trichloride, for the purpose of improving the life characteristics of the battery, suppressing battery capacity decrease, and improving the discharge capacity of the battery. At this time, the additives may be included in an amount of 0.1 wt% to 5 wt% based on the total weight of the electrolyte.

[0183]

[0184] A lithium secondary battery including a cathode active material according to the present invention has excellent capacity characteristics, initial efficiency, resistance characteristics, and life characteristics, and is therefore useful in portable devices such as mobile phones, laptop computers, and digital cameras, and electric vehicles such as hybrid electric vehicles (HEVs) and electric vehicles (EVs).

[0185] There is no particular limitation on the external shape of the lithium secondary battery of the present invention, but it may be a cylindrical shape using a can, a square shape, a pouch shape, or a coin shape.

[0186] The lithium secondary battery according to the present invention can be used not only as a battery cell used as a power source for a small device, but can also be preferably used as a unit battery in a medium- to large-sized battery module including a plurality of battery cells.

[0187] Accordingly, a battery module including the lithium secondary battery as a unit cell and a battery pack including the same are provided.

[0188] The above battery module or battery pack can be used as a power source for one or more medium- to large-sized devices, such as a power tool; an electric vehicle (EV), a hybrid electric vehicle, and a plug-in hybrid electric vehicle (PHEV); or a power storage system.

[0189]

[0190] Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art can easily implement them. However, the present invention may be implemented in various different forms and is not limited to the embodiments described herein.

[0191]

[0192] Example

[0193] Example 1

[0194] A 2.4 M concentration transition metal aqueous solution was prepared by mixing NiSO4, CoSO4, and MnSO4 in distilled water in an amount such that the molar ratio of nickel:cobalt:manganese was 65:15:20.

[0195] Next, deionized water was placed in a 20 L reactor, and nitrogen gas was introduced into the reactor at a rate of 30 L / hr to remove dissolved oxygen in the water and create a non-oxidizing atmosphere within the reactor. Afterwards, a 25 wt% NaOH aqueous solution was introduced to maintain the pH within the reactor at 11.40–12.50.

[0196] Afterwards, the above transition metal aqueous solution was injected into the reactor at a rate of 1.5 L / hr, 25 wt% NaOH aqueous solution was injected to maintain pH 11.40 to 12.50, and 9 wt% NH4OH aqueous solution was injected at a rate of 0.3 L / hr, respectively, while the average particle diameter (D) was maintained under the conditions of reaction temperature 60°C, pH 11.40 to 12.50, and stirring speed 250 to 1000 rpm. 50) was allowed to react until it became 9.0 μm. Afterwards, it was washed with water, filtered, and dried to obtain Ni. 0.65 Co 0.15 Mn 0.20 A positive electrode active material precursor having a composition represented by (OH)2 was prepared.

[0197] Thereafter, the above-mentioned positive electrode active material precursor and Li2CO3 were mixed so that the molar ratio of (Ni+Co+Mn):Li was 1:1.05, and calcined at 850°C for 10 hours in an air atmosphere to manufacture a positive electrode active material.

[0198]

[0199] Example 2

[0200] A 2.4 M concentration transition metal aqueous solution was prepared by mixing NiSO4, CoSO4, and MnSO4 in distilled water in an amount such that the molar ratio of nickel:cobalt:manganese was 70:10:20.

[0201] Next, deionized water was placed in a 20 L reactor, and nitrogen gas was introduced into the reactor at a rate of 30 L / hr to remove dissolved oxygen in the water and create a non-oxidizing atmosphere within the reactor. Afterwards, a 25 wt% NaOH aqueous solution was introduced to maintain the pH within the reactor at 11.10 to 12.45.

[0202] Afterwards, the above transition metal aqueous solution was injected into the reactor at a rate of 1.5 L / hr, 25 wt% NaOH aqueous solution was injected to maintain pH 11.10 to 12.45, and 9 wt% NH4OH aqueous solution was injected at a rate of 0.1 L / hr, respectively, while the average particle diameter (D) was maintained under the conditions of reaction temperature 50°C, pH 11.10 to 12.45, and stirring speed 250 to 1000 rpm. 50 ) was allowed to react until it became 9.0 μm. Afterwards, it was washed with water, filtered, and dried to obtain Ni. 0.7 Co 0.1 Mn 0.2 A positive electrode active material precursor having a composition represented by (OH)2 was prepared.

[0203] Thereafter, the above-mentioned positive electrode active material precursor and LiOH were mixed so that the molar ratio of (Ni+Co+Mn):Li was 1:1.05, and calcined at 820°C for 10 hours in an oxygen atmosphere to manufacture a positive electrode active material.

[0204]

[0205] Example 3

[0206] A 2.4 M concentration transition metal aqueous solution was prepared by mixing NiSO4, CoSO4, and MnSO4 in distilled water in an amount such that the molar ratio of nickel:cobalt:manganese was 88:5:7.

[0207] Next, deionized water was placed in a 20 L reactor, and nitrogen gas was introduced into the reactor at a rate of 30 L / hr to remove dissolved oxygen in the water and create a non-oxidizing atmosphere within the reactor. Afterwards, a 25 wt% NaOH aqueous solution was introduced to maintain the pH within the reactor at 10.55–12.10.

[0208] Afterwards, the above transition metal aqueous solution was injected into the reactor at a rate of 1.5 L / hr, 25 wt% NaOH aqueous solution was injected to maintain pH 10.55 to 12.10, and 9 wt% NH4OH aqueous solution was injected at a rate of 0.1 L / hr, respectively, while the average particle diameter (D) was maintained under the conditions of reaction temperature 50°C, pH 10.55 to 12.10, and stirring speed 250 to 1000 rpm. 50 ) was allowed to react until it became 10.0 μm. Afterwards, it was washed with water, filtered, and dried to obtain Ni. 0.88 Co 0.05 Mn 0.07 A positive electrode active material precursor having a composition represented by (OH)2 was prepared.

[0209] Afterwards, the above-mentioned positive electrode active material precursor and LiOH were mixed so that the molar ratio of (Ni+Co+Mn):Li was 1:1.07, and calcined at 770°C for 10 hours in an oxygen atmosphere to manufacture a positive electrode active material.

[0210]

[0211] Example 4

[0212] A 2.4 M concentration transition metal aqueous solution was prepared by mixing NiSO4, CoSO4, and MnSO4 in distilled water in an amount such that the molar ratio of nickel:cobalt:manganese was 88.5:3.5:8.

[0213] Next, deionized water was placed in a 20 L reactor, and nitrogen gas was introduced into the reactor at a rate of 30 L / hr to remove dissolved oxygen in the water and create a non-oxidizing atmosphere within the reactor. Afterwards, a 25 wt% NaOH aqueous solution was introduced to maintain the pH within the reactor at 12.50–12.90.

[0214] Afterwards, the above transition metal aqueous solution was injected into the reactor at a rate of 1.5 L / hr, 25 wt% NaOH aqueous solution was injected to maintain pH 12.50 to 12.90, and 9 wt% NH4OH aqueous solution was injected at a rate of 0.3 L / hr, respectively, while the average particle diameter (D) was maintained under the conditions of reaction temperature 50°C, pH 12.50 to 12.90, and stirring speed 250 to 1000 rpm. 50 ) was allowed to react until it became 4.2 μm. Afterwards, it was washed with water, filtered, and dried to obtain Ni. 0.885 Co 0.035 Mn 0.08 A positive electrode active material precursor having a composition represented by (OH)2 was prepared.

[0215] Afterwards, the above-mentioned positive electrode active material precursor and LiOH were mixed so that the molar ratio of (Ni+Co+Mn):Li was 1:1.07, and calcined at 770°C for 10 hours in an oxygen atmosphere to manufacture a positive electrode active material.

[0216]

[0217] Experimental example

[0218] Experimental Example 1

[0219] According to the method described in this specification, the twist value according to Equation 1 was obtained, and the results are shown in Table 1 below.

[0220]

[0221] Experimental Example 2

[0222] Through XRD analysis, the (a-axis length of crystal grains) / (c-axis length of crystal grains) of each of the positive electrode active material precursors manufactured in Examples 1 to 4 were obtained. Specifically, using XRD (Panalyticla, Empyrean), data in the 2θ 10° to 90° region were obtained under the conditions of Cu target, voltage 45 kV, and current 40 mA, and the FWHM (Full Width Half Maximum) of the (001) peak existing in the 18° to 20° region and the (100) peak existing in the 32° to 34° region were obtained, and the FWHM (001) / FWHM (100) value was calculated to obtain (a-axis length of crystal grains) / (c-axis length of crystal grains), and the average value thereof was obtained.

[0223] And, using BELSORP mini-II of BEL Japan, the BET specific surface area of ​​each of the positive electrode active material precursors manufactured in Examples 1 to 4 was obtained from the nitrogen gas adsorption amount at liquid nitrogen temperature (77 K) according to the BET method.

[0224] Finally, the average particle diameter (D) of each of the positive electrode active material precursors manufactured in Examples 1 to 4 was measured using PSA (Microtrac, S3500). 50 ) was obtained.

[0225] The results are shown in Table 1 below.

[0226] Average BET surface area [m] of the torsion value (a-axis length of crystal grains / c-axis length of crystal grains) 2 / g]Average particle size (D 50 )[㎛] Example 16.370.453.138.95 Example 26.900.895.939.00 Example 35.912.169.1710.0 Example 47.261.457.284.20

[0227] Experimental Example 3

[0228] Each of the positive electrode active materials, carbon black conductive agent, and PVdF binder manufactured in Examples 1 to 4 above was mixed in a weight ratio of 96:2:2 in an N-methylpyrrolidone solvent to manufacture a positive electrode slurry, and the positive electrode slurry was applied to one surface of an aluminum current collector, dried at 100°C, and then rolled to manufacture a positive electrode.

[0229] An electrode assembly was manufactured by interposing a porous polyethylene separator between the positive and negative electrodes (lithium metal) manufactured as described above, and the electrode assembly was placed inside a case, and an electrolyte was injected into the case to manufacture a lithium secondary battery. At this time, the electrolyte was manufactured by dissolving 1.0 M lithium hexafluorophosphate (LiPF6) in an organic solvent composed of ethylene carbonate, ethyl methyl carbonate, and diethyl carbonate (volume ratio = 3:4:3).

[0230] For each lithium secondary battery manufactured in this way, it was charged to 4.25 V with a 3C cut-off at a constant current of 1 C at 45°C, and then discharged to 3.0 V with a constant current of 0.33 C. The charge and discharge behavior was considered as one cycle, and this cycle was repeated 50 times. The capacity retention rate and resistance increase rate according to the cycle were calculated and shown in Table 2 below. The capacity retention rate is the discharge capacity (50) in the 50th cycle divided by the discharge capacity (initial capacity) in the 1st cycle. th Percentage of capacity ({(50) th capacity) / (initial capacity)}×100 [%]), and the resistance increase rate is the resistance in the 50th cycle (50) with respect to the resistance in the 1st cycle (initial resistance). th Percentage of resistance ({(50) th Resistance) / (Initial resistance) × 100 [%].

[0231] Capacity retention rate [%] Resistance increase rate [%] Example 197.16.7 Example 296.39.4 Example 395.812.5 Example 495.318.3

[0232] Referring to Table 1 above, in the case of the positive electrode active material precursors of Examples 1 to 4, it can be confirmed that the secondary particle form is formed by agglomeration of multiple primary particles, and the torsion value according to Equation 2 described herein is greater than 1.0 and less than or equal to 8.0. In addition, in the case of the positive electrode active material precursors of Examples 1 to 4, the average L value according to Equation 3 described herein is 0.3 or more, and the BET specific surface area is 2 m 2 / g to 15m 2 You can see that it is within the / g range.

[0233] Referring to Table 2 above, it can be confirmed that the battery including the positive electrode active material manufactured from the positive electrode active material precursors of Examples 1 to 4 has a high capacity retention rate of 95.0% or more under high temperature conditions and a low resistance increase rate of 18.5% or less.

[0234] In conclusion, it can be seen that the positive electrode active material precursor of the present invention can realize a positive electrode active material having optimal lithium mobility and improved structural stability during charge and discharge.

Claims

1. A method for analyzing a positive electrode active material precursor or a positive electrode active material, comprising the step of calculating a movement distance of lithium ions by assigning weights according to the degree of orientation from crystal structure information of the positive electrode active material precursor or a positive electrode active material using a Monte Carlo simulation method.

2. In claim 1, A method for analyzing a positive electrode active material precursor or positive electrode active material, wherein the positive electrode active material precursor or positive electrode active material is in the form of secondary particles formed by agglomeration of a plurality of primary particles.

3. In claim 1, A method for analyzing a positive electrode active material precursor or positive electrode active material, wherein the above crystal structure information is obtained by analyzing a cross-sectional SEM image or cross-sectional TEM image of the positive electrode active material precursor or positive electrode active material, thereby quantifying the degree to which crystal grains are oriented from the center of the positive electrode active material precursor or positive electrode active material particles toward the surface.

4. In claim 3, A method for analyzing a positive electrode active material precursor or positive electrode active material, wherein the analysis of the cross-sectional SEM image or cross-sectional TEM image is performed using at least one selected from the group consisting of EBSD, TEM-ASTAR, and 4D-STEM.

5. In claim 1, A method for analyzing a positive electrode active material precursor or positive electrode active material, wherein the degree of orientation is the degree to which crystal grains are oriented from the center of the positive electrode active material precursor or positive electrode active material particles toward the surface.

6. In claim 1, The above Monte Carlo simulation method is a method for analyzing a positive electrode active material precursor or a positive electrode active material, which includes a process of generating and setting a random direction for a noise portion having no crystal direction inside a positive electrode active material precursor or a positive electrode active material particle, selecting an arbitrary point on the surface of the positive electrode active material precursor or a positive electrode active material particle and setting it as the initial position of lithium, and then calculating the energy change that occurs when lithium ions move according to the following equation 1: [Formula 1] △E = s(∥r new ∥ - ∥r old ∥) - logf(d·c) In the above equation 1, r old is the current position of lithium, r new is the test location where lithium will move, d is the direction of movement (i.e. r new - r old ), c is the c-axis direction of the crystal, s(∥r new ∥ - ∥r old ∥) is the energy term that causes the particle to move to the center, - The logf(d·c) term is an energy term that makes it easier to move in the direction perpendicular to the c-axis, s = 0.3, f = 0.

01.

7. It is a secondary particle form formed by the aggregation of multiple primary particles. A cathode active material precursor having a tortuosity value of greater than 1.0 and less than or equal to 8.0 according to the following formula 2: [Formula 2] Tortuosity = (distance traveled by lithium ions) / (straight-line distance from the outer shell to the center) In the above equation 2, The migration distance of lithium ions is the distance that lithium ions actually move from any point on the surface of the positive electrode active material precursor particle to the center of the particle, and is obtained by the analysis method according to claim 1. The straight-line distance from the outer edge to the center is the straight-line distance from any point on the surface of the positive electrode active material precursor particle to the center of the particle.

8. In claim 7, A positive electrode active material precursor having a tortuosity value of 5.0 to 8.0 according to the above formula 2.

9. In claim 7, The above-mentioned lithium ion movement distance is calculated by a method including a process of analyzing a cross-sectional SEM image or cross-sectional TEM image of a positive electrode active material precursor using EBSD, TEM-ASTAR or 4D-STEM using a Monte Carlo simulation method, and assigning weights according to the degree to which the crystal grains are oriented from the center of the positive electrode active material precursor particles toward the surface. The above Monte Carlo simulation method includes a process of generating and setting a random direction for a noise portion having no crystal direction inside a positive electrode precursor particle, selecting an arbitrary point on the surface of a positive electrode precursor particle and setting it as the initial position of lithium, and then calculating the energy change that occurs when lithium ions move according to the following equation 1: [Formula 1] △E = s(∥r new ∥ - ∥r old ∥) - logf(d·c) In the above equation 1, r old is the current position of lithium, r new is the test location where lithium will move, d is the direction of movement (i.e. r new - r old ), c is the c-axis direction of the crystal, s(∥r new ∥ - ∥r old ∥) is the energy term that causes the particle to move to the center, - The logf(d·c) term is an energy term that makes it easier to move in the direction perpendicular to the c-axis, s = 0.3, f = 0.

01.

10. In claim 7, A cathode active material precursor having an average L value of 0.4 to 2.5 according to the following formula 3: [Formula 3] L = (a-axis length of the grain) / (c-axis length of the grain) In the above equation 3, The a-axis length of a crystal grain is the length of the longest axis among the a-axis direction vectors passing through the crystal grain. The c-axis length of a crystal grain is the length of the longest axis among the c-axis direction vectors passing through the crystal grain.

11. In claim 7, A cathode active material precursor comprising a complex transition metal hydroxide represented by the following chemical formula 1: [Chemical Formula 1] Ni a What b Mn c M d (OH)2 In the above chemical formula 1, M is one or more elements selected from the group consisting of Al, W, Cu, Fe, V, Cr, Ti, Zr, Zn, Ta, Y, In, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Mg, B, and Mo, 0.6≤a<1.0, 0 <b<0.4, 0<c<0.4, 0≤d≤0.2이다.

12. In claim 7, BET surface area is 3m 2 / g to 10m 2 / g positive electrode active material precursor.

13. In claim 7, Average particle diameter (D 50 ) A positive electrode active material precursor having a diameter of 4㎛ to 15㎛.

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