Cathode material, secondary battery comprising same, and method for measuring particle strength of cathode material

Abstract

The present invention relates to a cathode material, a secondary battery comprising same, and a method for measuring the particle strength of the cathode material, and, more specifically, to a cathode material and a secondary battery comprising the cathode material, the cathode material being at least one selected from the group consisting of: lithium cobalt oxide; lithium manganese oxide; lithium iron phosphate compound; lithium nickel cobalt aluminum oxide (NCA); lithium nickel oxide (LNO); nickel-manganese-based lithium composite metal oxide obtained by substituting a portion of the nickel (Ni) in the LNO with manganese (Mn); a lithium composite transition metal oxide (NCM) obtained by substituting a portion of the Ni in the LNO with Mn and cobalt (Co); and a lithium composite transition metal oxide (NCMA) in which aluminum (Al) is added to the NCM, and, if at least one from among detailed mathematical formulas 1 to 4 is satisfied, the cathode material causing no particle breakage during an electrode manufacturing process so as to prevent battery performance deterioration due to fine powder, exhibiting excellent lifespan characteristics in a high-voltage environment, having high thermal stability and reducing the amount of gas generated as a result of charging and discharging.

Description

Cathode material, secondary battery containing same, and method for measuring particle strength of cathode material

[0001] 〔Cross-citation with the applicant(s)〕

[0002] This application claims the benefit of priority to Korean Patent Application No. 10-2023-0116895, dated September 4, 2023, and Korean Patent Application No. 10-2023-0116896, dated September 4, 2023, and to Korean Patent Application No. 10-2024-0116537, filed August 29, 2024, and to Korean Patent Application No. 10-2024-0116538, filed August 29, 2024, which are each independently and herein incorporated by reference. The entire disclosure of the relevant Korean patent applications is hereby incorporated by reference herein.

[0003] The present invention relates to a cathode material, a secondary battery including the same, and a method for measuring the particle strength of the cathode material. More specifically, the present invention provides a cathode material and a secondary battery including the same, which do not cause particle breakage during an electrode manufacturing process, thereby preventing degradation of battery performance due to fine particles, have excellent life characteristics in a high-voltage environment, have high thermal stability, and generate little gas during charge and discharge, and also relates to a method for easily measuring the particle strength of a cathode material having high crystallinity.

[0004] A lithium secondary battery is largely composed of a cathode in which a positive active material layer is coated on a metal foil such as aluminum, a negative electrode in which a negative active material layer is coated on a metal foil such as copper, a separator that prevents the positive and negative electrodes from mixing, and an electrolyte that allows lithium ions to move between the positive and negative electrodes.

[0005] The cathode active materials (hereinafter also referred to as "cathode materials") used in the above cathode active material layer include lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), lithium manganese oxide (LiMnO2, etc.), lithium iron phosphate compound (LiFePO4), etc., and among these, lithium cobalt oxide (LiCoO2) is widely used as a high-voltage cathode active material due to its high operating voltage and excellent capacity characteristics, but there are limitations in applying it to large-capacity lithium secondary batteries used in electric vehicles, etc. due to the rising price of cobalt (Co) and unstable supply.

[0006] Accordingly, a lithium composite transition metal oxide (hereinafter referred to as 'NCM cathode active material') in which some of the cobalt (Co) in the lithium cobalt oxide is replaced with nickel (Ni) and manganese (Mn) has been developed, but since it is in the form of secondary particles in which primary particles are aggregated, fine powder is easily generated due to particle breakage during the electrode manufacturing process, the specific surface area is large, and the content of lithium byproducts is high, gas is generated when the secondary battery is operated, thermal stability is low, and the performance of the battery, such as life characteristics, is deteriorated in a high-voltage environment.

[0007] In addition, a particle strength meter is generally used to easily measure the particle strength of the positive electrode active material, but there is a problem in that although it is possible to measure the particle strength of secondary particles of positive electrode active material with low crystallinity, it is impossible to measure the strength of primary particles of positive electrode active material with high crystallinity.

[0008] In order to solve the problems of the prior art as described above, the present invention aims to provide a cathode material and a secondary battery including the same, which does not cause particle breakage during the electrode manufacturing process, thereby preventing degradation of battery performance due to fine powder, has excellent life characteristics in a high-voltage environment, has high thermal stability, and generates little gas during charge and discharge.

[0009] In addition, the present invention aims to provide a method for easily measuring the particle strength of a cathode material having high crystallinity.

[0010] The above and other objects of the present invention can all be achieved by the present invention described below.

[0011] In order to achieve the above object, I) the present invention provides a cathode material, which is characterized by at least one selected from the group consisting of lithium cobalt oxide; lithium manganese oxide; lithium iron phosphate compound; lithium nickel cobalt aluminum oxide (NCA); lithium nickel oxide (LNO); nickel manganese-based lithium composite metal oxide in which a part of nickel (Ni) in the lithium nickel oxide is substituted with manganese (Mn); lithium composite transition metal oxide (NCM) in which a part of nickel (Ni) in the lithium nickel oxide is substituted with manganese (Mn) and cobalt (Co); and lithium composite transition metal oxide (NCMA) in which aluminum (Al) is added to the lithium composite transition metal oxide (NCM), and which has a monomodal particle size distribution, a crystal size measured by XRD of 216.2 nm or more, and containing cobalt (Co) and manganese (Mn), and a molar ratio of the cobalt and manganese of 1:0.5 to 2.5.

[0012] II) The present invention relates to a lithium cobalt oxide; a lithium manganese oxide; a lithium iron phosphate compound; a lithium nickel cobalt aluminum oxide (NCA); a lithium nickel oxide (LNO); a nickel manganese-based lithium composite metal oxide in which a part of nickel (Ni) in the lithium nickel oxide is replaced with manganese (Mn); a lithium composite transition metal oxide (NCM) in which a part of nickel (Ni) in the lithium nickel oxide is replaced with manganese (Mn) and cobalt (Co); and a lithium composite transition metal oxide (NCMA) in which aluminum (Al) is added to the lithium composite transition metal oxide (NCM), and is at least one selected from the group consisting of the following mathematical formulas 1 to 4.

[0013] [Mathematical Formula 1]

[0014] 1.58 ≥ del_PD_absolute ≥ 1

[0015] (Here, del_PD_absolute is the difference between the absolute value of the ideal and measured rolling density when the load is 9,000 kgf.)

[0016] [Equation 2]

[0017] 0.3 ≥ del_PD ≥ 0.2

[0018] (Here, del_PD is the difference between the ideal and measured values ​​of rolling density (normalized value) when the load is 9,000 kgf.)

[0019] [Equation 3]

[0020] 0.21 ≥ del_inclination ≥ 0.15

[0021] (Here, del_inclination is the difference in inclination between the ideal and measured values ​​of rolling density between 0 and 9,000 kgf load.)

[0022] [Equation 4]

[0023] (1 - del_PD) / EMD ≥ 10.1

[0024] (Here, del_PD is the difference between the ideal value of the rolling density and the measured value (normalized value) when the load is 9,000 kgf, and EMD (Earth Mover's Distance) is a value obtained using SciPy's Wasserstein_distance function (u_values ​​= particle distribution before rolling, v_values ​​= particle distribution after rolling, u_weights = none, v_weights = none).) provides a cathode material that satisfies at least one of the following.

[0025] III) In the above I) or II), the cathode material may have a monomodal particle size distribution.

[0026] IV) In the above I) to III), the molar ratio of the entire transition metal to lithium in the positive electrode material may be 1:1 to 1.05.

[0027] V) In the above I) to IV), the cathode material may have a crystal size of 216.2 nm or more as measured by XRD.

[0028] VI) In the above I) to V), the positive electrode material may contain nickel (Ni) and may contain nickel (Ni) in an amount of 65 mol% or more based on 100 mol% of the total remaining metals excluding lithium (Li).

[0029] VII) In the above I) to VI), the cathode material contains cobalt (Co) and manganese (Mn), and the molar ratio of cobalt and manganese may be 1:0.5 to 2.5.

[0030] VIII) In the above I) to VII), the positive electrode material is represented by the following chemical formula 1

[0031] [Chemical Formula 1]

[0032] Li a Ni x Mn y Co z M w O 2+δ

[0033] (In the above chemical formula 1, M includes at least one selected from the group consisting of B, W, Al, Ti and Mg, and 1 <a≤1.1, 0<x<0.95, 0<y<0.8, 0<z<1.0, 0≤w≤0.1, -0.02≤δ≤0.02, x+y+z+w=1이다.)로 표시되는 화합물일 수 있다.

[0034] IX) In the above I) to VIII), the positive electrode material may have an EDM (Earth Mover's Distance) value of 0.071 or less obtained using the Wasserstein_distance function of SciPy (u_values=particle distribution before rolling, v_values=particle distribution after rolling, u_weights=none, v_weights=none).

[0035] X) In the above I) to IX), the positive electrode material may be a single particle.

[0036] XI) In the above I) to X), the surface of the positive electrode material may be coated with a coating agent containing metal or carbon.

[0037]

[0038] In addition, XII) the present invention provides a secondary battery including a positive electrode material according to I) to XI).

[0039]

[0040] In addition, XIII) The present invention comprises the steps of: A) measuring the rolling density of a cathode material using a powder resistance meter between 0 kgf and 2,000 kgf load or less; B) measuring the rolling density of a cathode material using a hydraulic press at over 2,000 kgf load or more; And C) a method for measuring particle strength of a cathode material is provided, including a step of obtaining EMD by using the absolute difference (del_PD_absolute) between the ideal value of the rolled density and the measured value, the relative difference (del_PD) between the ideal value of the rolled density and the measured value, the inclination difference (del_inclination) between the ideal value of the rolled density and the measured value, or the particle distribution before and after rolling, and using the Wasserstein_distance function of SciPy (u_values=particle distribution before rolling, v_values=particle distribution after rolling, u_weights=none, v_weights=none).

[0041] XIV) In the above XIII), the positive electrode material is represented by the following chemical formula 1

[0042] [Chemical Formula 1]

[0043] Li a Ni x Mn y Co z M w O 2+δ

[0044] (In the above chemical formula 1, M includes at least one selected from the group consisting of B, W, Al, Ti and Mg, and 1 <a≤1.1, 0<x<0.95, 0<y<0.8, 0<z<1.0, 0≤w≤0.1, -0.02≤δ≤0.02, x+y+z+w=1이다.)로 표시되는 화합물일 수 있다.

[0045] XV) In the above XIII) or XIV), the particle may be a single particle.

[0046] XVI) In the above XIII) to XV), the step B) may be a step of measuring the rolling density of the positive electrode material using a hydraulic press at a load exceeding 2,000 kgf or between 2,000 kgf and 9,000 kgf.

[0047]

[0048] In addition, XVII) The present invention comprises the following chemical formula 1

[0049] [Chemical Formula 1]

[0050] Li a Ni x Mn y Co z M w O 2+δ

[0051] (In the above chemical formula 1, M includes at least one selected from the group consisting of B, W, Al, Ti and Mg, and 1 <a≤1.1, 0<x<0.95, 0<y<0.8, 0<z<1.0, 0≤w≤0.1, -0.02≤δ≤0.02, x+y+z+w=1이다.)로 표시되는 화합물이고, 모노모달(monomodal)의 입도 분포를 가지며, 전이금속 전체와 리튬의 몰비가 1: 1 내지 1.05이고, XRD로 측정한 결정 크기가 216.2 nm 이상이며, 리튬(Li)을 제외한 나머지 금속 총 100 몰%를 기준으로 니켈(Ni)을 65 몰% 이상 포함하고, 코발트와 망간의 몰비가 1: 0.5 내지 2.5인 양극재를 제공한다.

[0052] XVIII) In the above XVII), the positive electrode material may be I) to XI), and may also be a positive electrode material of the above XII) secondary battery.

[0053] According to the present invention, there is provided a cathode material and a secondary battery including the same, which do not cause particle breakage during the electrode manufacturing process, thereby preventing degradation of battery performance due to fine particles, have excellent life characteristics in a high-voltage environment, have high thermal stability, and generate little gas during charge and discharge, and also provide a method for easily measuring the particle strength of a cathode material having high crystallinity.

[0054] Figure 1 is a graph showing the rolling density of the cathode material manufactured in Example 1 as an ideal value and a measured value, respectively, depending on the load.

[0055] Figure 2 is a graph showing the rolling density of the cathode material manufactured in Comparative Example 2 as an ideal value and a measured value according to the load.

[0056] Figure 3 is a graph showing the rolling density of the cathode material manufactured in Comparative Example 3 as an ideal value and a measured value according to the load.

[0057] Figure 4 is a graph showing the particle size distribution before and after rolling of the cathode material manufactured in Example 1.

[0058] Figure 5 is a graph showing the particle size distribution before and after rolling of the cathode material manufactured in Comparative Example 2.

[0059] 6 shows Xiangbang Kong, Yige Zhang, Shiyun Peng, Jing Zeng, and Jinbao Zhao, “Superiority of Single-Crystal to Polycrystalline LiNi x Co y Mn 1-x-y This is an SEM image of the cathode material published in "O2Cathode Materials in Storage Behaviors for Lithium-Ion Batteries", ACS Sustainable Chem. Eng. 2020, 8, 14938-14948.

[0060]

[0061] The present inventors have confirmed that when a cathode material is designed so that the absolute difference between the ideal value and the measured value of the rolling density of the cathode material in a predetermined section (del_PD_absolute), the relative difference between the ideal value and the measured value of the rolling density of the cathode material (del_PD), the inclination difference between the ideal value and the measured value of the rolling density of the cathode material (del_inclination), and / or the distance between the particle size distributions before and after rolling of the cathode material fall within a predetermined range, such a cathode material does not break particles during the electrode manufacturing process, so that the performance of the battery does not deteriorate due to fine particles, and has excellent life characteristics in a high-voltage environment, high thermal stability, and a small amount of gas generated during charge and discharge, and based on this, they have further devoted themselves to research and completed the present invention.

[0062]

[0063] Below, the cathode material of this invention, the secondary battery including the cathode material, and the method for measuring the particle strength of the cathode material are described in detail.

[0064] However, the terms or words used in this specification and claims cannot be interpreted as limited to their usual or dictionary meanings, and 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 application in the best way. Therefore, the embodiments described in this specification and the configurations illustrated in the drawings are only one embodiment of the present invention and do not represent all of the technical idea of ​​the present invention, and it should be understood that there may be various equivalents and modified examples that can replace them, and that they can be arranged, replaced, combined, separated, or designed in various other configurations.

[0065] All technical and scientific terms used in this document, unless otherwise defined, have the same meaning as commonly understood by a person of ordinary skill in the art to which the present invention pertains.

[0066]

[0067] The cathode material of the present invention is at least one selected from the group consisting of lithium cobalt oxide; lithium manganese oxide; lithium iron phosphate compound; lithium nickel cobalt aluminum oxide (NCA); lithium nickel oxide (LNO); nickel manganese-based lithium composite metal oxide in which a portion of nickel (Ni) in the lithium nickel oxide is substituted with manganese (Mn); lithium composite transition metal oxide (NCM) in which a portion of nickel (Ni) in the lithium nickel oxide is substituted with manganese (Mn) and cobalt (Co); and lithium composite transition metal oxide (NCMA) in which aluminum (Al) is added to the lithium composite transition metal oxide (NCM), and is characterized in that it has a monomodal particle size distribution, has a crystal size of 216.2 nm or more as measured by XRD, contains cobalt (Co) and manganese (Mn), and has a molar ratio of cobalt and manganese of 1:0.5 to 2.5. In this case, there is no particle breakage during the electrode manufacturing process, so there is no degradation of battery performance due to fine particles, and there is an effect of providing a cathode material with excellent life characteristics in a high-voltage environment, high thermal stability, and low gas generation during charge and discharge.

[0068]

[0069] In addition, the cathode material of the present invention is at least one selected from the group consisting of lithium cobalt oxide; lithium manganese oxide; lithium iron phosphate compound; lithium nickel cobalt aluminum oxide (NCA); lithium nickel oxide (LNO); nickel manganese-based lithium composite metal oxide in which a part of nickel (Ni) in the lithium nickel oxide is substituted with manganese (Mn); lithium composite transition metal oxide (NCM) in which a part of nickel (Ni) in the lithium nickel oxide is substituted with manganese (Mn) and cobalt (Co); and lithium composite transition metal oxide (NCMA) in which aluminum (Al) is added to the lithium composite transition metal oxide (NCM), and has the following mathematical formulas 1 to 4:

[0070] [Mathematical Formula 1]

[0071] 1.58 ≥ del_PD_absolute ≥ 1

[0072] (Here, del_PD_absolute is the difference between the absolute value of the ideal and measured rolling density when the load is 9,000 kgf.)

[0073] [Equation 2]

[0074] 0.3 ≥ del_PD ≥ 0.2

[0075] (Here, del_PD is the difference between the ideal and measured values ​​of rolling density (normalized value) when the load is 9,000 kgf.)

[0076] [Equation 3]

[0077] 0.21 ≥ del_inclination ≥ 0.15

[0078] (Here, del_inclination is the difference in inclination between the ideal and measured values ​​of rolling density between 0 and 9,000 kgf load.)

[0079] [Equation 4]

[0080] (1 - del_PD) / EMD ≥10.1

[0081] (Here, del_PD is the difference between the ideal value of the rolling density and the relative value (normalized value) of the measured value when the load is 9,000 kgf, and EMD (Earth Mover's Distance) is a value obtained using the Wasserstein_distance function of SciPy (u_values ​​= particle distribution before rolling, v_values ​​= particle distribution after rolling, u_weights = none, v_weights = none).) is characterized by satisfying at least one of the following. In this case, there is no particle breakage during the electrode manufacturing process, so there is no deterioration of battery performance due to fine powder, and there is an effect of providing a cathode material with excellent life characteristics in a high-voltage environment, high thermal stability, and low gas generation due to charge and discharge.

[0082]

[0083] The above mathematical formula 1 is preferably the following mathematical formula 1-1

[0084] [Mathematical Formula 1-1]

[0085] 1.4 ≥ del_PD_absolute ≥ 1

[0086] (Here, del_PD_absolute is the difference between the ideal value of the rolling density and the measured value when the load is 9,000 kgf.) and more preferably, the following mathematical expression 1-2

[0087] [Equation 1-2]

[0088] 1.35 ≥ del_PD_absolute ≥ 1.1

[0089] (Here, del_PD_absolute is the absolute value difference between the ideal value of the rolling density and the measured value when the load is 9,000 kgf.) Within this range, there is no particle breakage during the electrode manufacturing process, so there is no degradation of battery performance due to fine powder, and there is an advantage of providing a cathode material with excellent life characteristics in a high-voltage environment, high thermal stability, and low gas generation during charge and discharge.

[0090]

[0091] The above mathematical formula 2 is preferably the following mathematical formula 2-1

[0092] [Equation 2-1]

[0093] 0.29 ≥ del_PD ≥ 0.2

[0094] (Here, del_PD is the difference between the ideal value of the rolling density and the measured value (normalized value) when the load is 9,000 kgf.) and more preferably, the following mathematical expression 2-2

[0095] [Equation 2-2]

[0096] 0.29 ≥ del_PD ≥ 0.21

[0097] (Here, del_PD is the difference between the ideal value of the rolling density and the measured value (normalized value) when the load is 9,000 kgf.) can be satisfied, and more preferably, the following mathematical expression 2-3

[0098] [Equation 2-3]

[0099] 0.28 ≥ del_PD ≥ 0.22

[0100] (Here, del_PD is the difference between the ideal value of the rolling density and the measured value (normalized value) when the load is 9,000 kgf.) can be satisfied, and more preferably, mathematical expression 2-4

[0101] [Equation 2-4]

[0102] 0.28 ≥ del_PD ≥ 0.23

[0103] (Here, del_PD is the difference between the ideal value of the rolling density and the measured value (normalized value) when the load is 9,000 kgf.) can be satisfied, and within this range, there is no particle breakage during the electrode manufacturing process, so there is no deterioration of battery performance due to fine powder, and there is an advantage of providing a cathode material with excellent life characteristics in a high-voltage environment, high thermal stability, and low gas generation due to charge and discharge.

[0104]

[0105] The above mathematical formula 3 is preferably the following mathematical formula 3-1

[0106] [Equation 3-1]

[0107] 0.20 ≥ del_inclination ≥ 0.15

[0108] (where del_inclination is the difference in inclination between the ideal and measured values ​​of rolling density between 0 and 9,000 kgf load) may be, and more preferably, mathematical expression 3-2

[0109] [Equation 3-2]

[0110] 0.19 ≥ del_inclination ≥ 0.15

[0111] (Here, del_inclination is the difference in slope between the ideal and measured values ​​of the rolling density between 0 and 9,000 kgf load.) Within this range, there is no particle breakage during the electrode manufacturing process, so there is no degradation of battery performance due to fine powder, and there is an advantage in providing a cathode material with excellent life characteristics in a high-voltage environment, high thermal stability, and low gas generation during charge and discharge.

[0112]

[0113] The above mathematical expression 4 is preferably the following mathematical expression 4-1

[0114] [Equation 4-1]

[0115] (1 - del_PD) / EMD ≥ 11

[0116] (Here, del_PD is the difference between the ideal value of the rolling density and the measured value (normalized value) when the load is 9,000 kgf, and EMD (Earth Mover's Distance) is a value obtained using the Wasserstein_distance function of SciPy (u_values ​​= particle distribution before rolling, v_values ​​= particle distribution after rolling, u_weights = none, v_weights = none).) and more preferably, the following mathematical expression 2-2

[0117] [Equation 4-2]

[0118] (1 - del_PD) / EMD ≥ 15

[0119] (Here, del_PD is the difference between the ideal value of the rolling density and the measured value (normalized value) when the load is 9,000 kgf, and EMD (Earth Mover's Distance) is a value obtained using the Wasserstein_distance function of SciPy (u_values ​​= particle distribution before rolling, v_values ​​= particle distribution after rolling, u_weights = none, v_weights = none).) and more preferably, the following mathematical expression 2-3

[0120] [Equation 4-3]

[0121] (1 - del_PD) / EMD ≥ 20

[0122] (Here, del_PD is the difference between the ideal value of the rolling density and the measured value (normalized value) when the load is 9,000 kgf, and EMD (Earth Mover's Distance) is a value obtained using the Wasserstein_distance function of SciPy (u_values ​​= particle distribution before rolling, v_values ​​= particle distribution after rolling, u_weights = none, v_weights = none).) and more preferably, the following mathematical expression 2-4

[0123] [Equation 4-4]

[0124] (1 - del_PD) / EMD ≥ 25

[0125] (Here, del_PD is the difference between the ideal value of the rolling density and the measured value (normalized value) when the load is 9,000 kgf, and EMD (Earth Mover's Distance) is a value obtained using the Wasserstein_distance function of SciPy (u_values ​​= particle distribution before rolling, v_values ​​= particle distribution after rolling, u_weights = none, v_weights = none).) and, particularly preferably, the following mathematical formula 2-5

[0126] [Equation 4-5]

[0127] (1 - del_PD) / EMD ≥ 30

[0128] (Here, del_PD is the difference between the ideal value of the rolling density and the measured value (normalized value) when the load is 9,000 kgf, and EMD (Earth Mover's Distance) is a value obtained using the Wasserstein_distance function of SciPy (u_values ​​= particle distribution before rolling, v_values ​​= particle distribution after rolling, u_weights = none, v_weights = none).) and, more preferably, the following mathematical expression 2-6

[0129] [Equation 4-6]

[0130] (1 - del_PD) / EMD ≥ 35

[0131] (Here, del_PD is the difference between the ideal value of the rolling density and the measured value (normalized value) when the load is 9,000 kgf, and EMD (Earth Mover's Distance) is a value obtained using the Wasserstein_distance function of SciPy (u_values=particle distribution before rolling, v_values=particle distribution after rolling, u_weights=none, v_weights=none).) can be, and within this range, there is no particle breakage during the electrode manufacturing process, so there is no degradation of battery performance due to fines, and there is an advantage of providing a cathode material with excellent life characteristics in a high-voltage environment, high thermal stability, and low gas generation due to charge and discharge.

[0132]

[0133] The above cathode material may preferably have a monomodal particle size distribution, more preferably a monomodal particle size distribution in which a peak falls between particle sizes of 1 and 8 ㎛, and even more preferably a monomodal particle size distribution in which a peak falls between particle sizes of 2 and 7 ㎛, and within this range, there is no particle breakage during the electrode manufacturing process, so that a performance degradation of the battery due to fine powder does not occur, and there is an effect of providing a cathode material having excellent life characteristics in a high-voltage environment, high thermal stability, and low gas generation due to charge and discharge.

[0134] The above cathode material may preferably have a monomodal particle size distribution even after rolling under a 9-ton load condition, more preferably, it has a monomodal particle size distribution in which the difference in particle size between peaks before and after rolling is 2 ㎛ or less, and even more preferably, it has a monomodal particle size distribution in which the difference in particle size between peaks before and after rolling is 1.5 ㎛ or less, and even more preferably, it has a monomodal particle size distribution in which the difference in particle size between peaks before and after rolling is 1 ㎛ or less, and within this range, there is no particle breakage during the electrode manufacturing process, so that the performance of the battery does not deteriorate due to fine powder, and there is an effect of providing a cathode material having excellent life characteristics in a high-voltage environment, high thermal stability, and low gas generation due to charge and discharge. Here, the rolling can be performed using a hydraulic press.

[0135] In this paper, the particle size distribution is a PSD (Particle Size Distribution) graph, which can be measured using a laser diffraction particle size analyzer. For example, the positive electrode active material powder can be dispersed in a dispersion medium and then introduced into a commercially available laser diffraction particle size measuring device (e.g., Microtrac MT 3000, etc.) for measurement. As a specific example, the mixture of the positive electrode active material powder and the dispersion medium can be dispersed using an ultrasonic disperser with an ultrasonic wave of about 40 kHz and 40 W output, and then measured by irradiating it with a laser of about 3 to 4 mW output.

[0136]

[0137] The above cathode material may preferably have a molar ratio of the entire transition metal to lithium of 1:1 to 1.05, more preferably 1:1.01 to 1.05, even more preferably 1:1.02 to 1.05, and even more preferably 1:1.03 to 1.05, and has the advantage of excellent life characteristics within this range.

[0138]

[0139] The above cathode material preferably has a crystal size measured by XRD of 216.2 nm or more, more preferably 217 nm or more, even more preferably 260 nm or less, and even more preferably 257 nm or less, and within this range, there is an advantage of excellent battery life characteristics in a high voltage environment.

[0140] In this paper, the crystal size can be measured by XRD crystal analysis, and there is no deviation depending on the measuring device or method. Specifically, the crystal size can be obtained by placing about 5 to 10 g of the cathode material in a holder, irradiating the particle with X-rays, and analyzing the resulting diffraction grating.

[0141]

[0142] The above cathode material preferably contains nickel (Ni), and may contain nickel (Ni) in an amount of 65 mol% or more, more preferably 70 mol% or more, even more preferably 75 mol% or more, even more preferably 80 mol% or more, and even more preferably 85 mol% or more, and as a specific example, 95 mol% or less, and as a preferred example, 90 mol% or less, and within this range, there is an advantage of excellent life characteristics.

[0143]

[0144] The above cathode material preferably contains cobalt (Co) and manganese (Mn), and the molar ratio of cobalt and manganese may be 1:0.5 to 2.5, more preferably 1:0.7 to 2.3, even more preferably 1:0.7 to 2.0, still more preferably 1:1.6 to 2.0, and particularly preferably 1:1.6 to 1.9, and within this range, there is an advantage of excellent life characteristics.

[0145]

[0146] In the present invention, the content of metal components such as nickel (Ni), cobalt (Co), and manganese (Mn) is not particularly limited when measured using a measurement method such as IC (Ion Chromatography) commonly used in the technical field to which the present invention belongs, and specific examples thereof include an IC-ICP (Inductively Coupled Plasma) analyzer, an IC-ICP-MS analyzer, or an IC-ICP-AEC analyzer.

[0147]

[0148] The above cathode material is preferably represented by the following chemical formula 1

[0149] [Chemical Formula 1]

[0150] Li a Ni x Mn y Coz M w O 2+δ

[0151] (In the above chemical formula 1, M includes at least one selected from the group consisting of B, W, Al, Ti and Mg, and 1 <a≤1.1, 0<x<0.95, 0<y<0.8, 0<z<1.0, 0≤w≤0.1, -0.02≤δ≤0.02, x+y+z+w=1이다.)로 표시되는 화합물일 수 있고, 이 범위 내에서 전극 제조 공정 중에 입자 깨짐이 없어 미분으로 인한 전지의 성능 저하가 발생하지 않고, 고전압 환경에서 수명 특성이 뛰어나며, 열안정성이 높고 충방전에 따른 가스 발생량이 적은 양극재를 제공하는 효과가 있다.

[0152]

[0153] The above cathode material may preferably have an EDM (Earth Mover's Distance) value of 0.071 or less, preferably 0.069 or less, and even more preferably 0.65 or less, obtained using the Wasserstein_distance function of SciPy (u_values=particle distribution before rolling, v_values=particle distribution after rolling, u_weights=none, v_weights=none). Within this range, there is no particle breakage during the electrode manufacturing process, so there is no degradation of battery performance due to fine particles. There is an advantage of providing a cathode material having excellent life characteristics in a high-voltage environment, high thermal stability, and low gas generation during charge and discharge. Here, "u_values" and "v_values" are vol% for the particle size, and the vol% values ​​before and after rolling at the same particle size (㎛) can be input into u_values ​​and v_values, respectively. Also, "u_weights" and "v_weights" are weights, and "none" means that no values ​​are entered, so the weights are equal.

[0154] The above pre-rolling particle distribution and post-rolling particle distribution preferably each include the entire particle size distribution graph value (vector value), and as a specific example, 100 to 150 values ​​can be entered, and in the embodiment of the present invention, 131 values ​​are entered.

[0155] The above rolling can be performed under, for example, a 9,000 kgf load.

[0156]

[0157] In this paper, EMD (Earth Mover's Distance) is one of the measures for evaluating the similarity between two distributions, and is also referred to as the 1st Wasserstein metric. EMD is a distance measure that represents the minimum amount of work required to move a u distribution to a v distribution, and the work can be calculated as the sum of the product of the weight to be moved for each section of the histogram (discrete distribution) and the moving distance. The weight to be moved for each section corresponds to vol% of the particle size in the present invention.

[0158]

[0159] The above cathode material may preferably be a single particle, more preferably does not include secondary particles, and in this case, there is no particle breakage during the electrode manufacturing process, so that there is no deterioration in battery performance due to fine particles, and there is an effect of providing a cathode material having excellent life characteristics in a high-voltage environment, high thermal stability, and low gas generation during charge and discharge.

[0160] The single particle may be, for example, a particle composed of 30 or fewer nodules, preferably a particle composed of 1 to 20 nodules, more preferably a particle composed of 1 to 10 nodules, even more preferably a particle composed of 1 to 5 nodules, and most preferably a particle composed of 1 nodule. In this case, there is an effect of providing a cathode material in which there is no particle breakage during the electrode manufacturing process, so that the performance of the battery does not deteriorate due to fine powder, and has excellent life characteristics in a high-voltage environment, high thermal stability, and low gas generation due to charge and discharge.

[0161] In this description, a nodule refers to a particle unit body that constitutes a single particle, and may refer to a single crystal lacking a crystalline grain boundary, or a polycrystal in which no grain boundary exists in appearance when observed at a field of view of 5,000 to 20,000 times using a scanning electron microscope (SEM) or an electron backscatter diffraction pattern analyzer (EBSD).

[0162] In this description, the number of nodules means the average number of nodules of positive electrode material particles, and a positive electrode including positive electrode active material is cut by an ion milling method, and a cross-sectional image in the thickness direction of the cut positive electrode is obtained using a scanning electron microscope (SEM), and then at least 30 particles are selected from the cross-sectional image for each of large-diameter positive electrode active material particles and small-diameter positive electrode active material particles, and then the number of nodules in the cross-section of each positive electrode active material particle is measured through SEM image analysis, and the arithmetic mean is obtained.

[0163] In this description, a secondary particle means a particle that is an aggregate formed by the agglomeration of multiple single particles and contains more than 30 nodules.

[0164] Figure 6 below shows Xiangbang Kong, Yige Zhang, Shiyun Peng, Jing Zeng, and Jinbao Zhao, "Superiority of Single-Crystal to Polycrystalline LiNi x Co y Mn 1-x-y This is an SEM image of the cathode material published in "O2Cathode Materials in Storage Behaviors for Lithium-Ion Batteries", ACS Sustainable Chem. Eng. 2020, 8, 14938-14948.

[0165] Referring to FIG. 6, image a shows a single particle of NCM622 positive electrode active material as a smooth particle without nodules on the surface, images b and b1 show secondary particles of NCM622 positive electrode active material as particles with multiple nodules formed on the surface, and image c shows a single particle of NCM811 positive electrode active material as a smooth particle without nodules on the surface, and images d and d1 show secondary particles of NCM811 positive electrode active material with multiple nodules formed on the surface. In this way, single particles and secondary particles can be easily distinguished through SEM image analysis.

[0166]

[0167] The method for manufacturing a cathode material according to the present invention may be any of the cathode material manufacturing methods commonly used in the technical field to which the present invention pertains, as long as it satisfies the definition of the cathode material of the present invention, and is not particularly limited.

[0168] The method for manufacturing the above cathode material may preferably include a step of calcining a transition metal hydroxide and lithium hydroxide in an air or oxygen atmosphere at 750 to 950°C, preferably 800 to 900°C, for 5 to 15 hours, preferably 10 to 15 hours.

[0169] The above transition metal hydroxide may be referred to as a transition metal precursor as a transition metal source of the positive electrode active material, and the above lithium hydroxide may be referred to as a lithium precursor as a lithium source of the positive electrode active material.

[0170]

[0171] The above cathode material may preferably have a surface coated with a coating agent containing metal or carbon, in which case the structural stability of the cathode active material is improved without chemical and physical changes in the cathode active material itself, thereby improving electrochemical properties such as output performance, life characteristics, and capacity, and the physicochemical properties are also improved due to the effect of controlling the amount of residual lithium and reducing pH by substituting a different element on the surface of the cathode active material.

[0172]

[0173] The metal is preferably at least one selected from the group consisting of B, W, Al, Ti, Mg, Ni, Co, Mn, Si, Zr, Ge, Sn, Cr, Fe, V and Y, more preferably at least one selected from the group consisting of B, W, Al, Ti and Mg, even more preferably boron (B), tungsten (W) or a mixture thereof, even more preferably tungsten (W) and boron (B), and a specific example is tungsten boride (WB), in which case there is an effect of improving resistance characteristics and life characteristics.

[0174] The coating agent containing the metal may be, for example, an oxide or acid containing the metal as an element within the molecule.

[0175] The coating agent containing the above-mentioned organic metal is not particularly limited as long as it is a coating agent containing an organic metal compound commonly used in the technical field to which the present invention belongs and containing the above-mentioned metal, and a specific example thereof may be a metal alkoxide, etc.

[0176] The coating agent containing the above carbon component is not particularly limited as long as it is a coating agent containing a carbon component commonly used in the technical field to which the present invention belongs, and a specific example thereof may be a sugar such as sucrose.

[0177] The coating agent may be included, for example, in an amount of 0.001 to 0.3 mol% relative to 1 mol% of metal in the positive electrode active material before coating treatment, preferably 0.01 to 0.3 mol%, more preferably 0.01 to 0.15 mol%, even more preferably 0.01 to 0.1 mol%, and even more preferably 0.01 to 0.05 mol%, and within this range, it has the effect of improving structural stability and electrochemical performance while maintaining the properties of the positive electrode active material itself.

[0178]

[0179] The surface coating is preferably performed by coating a coating agent containing at least one of a metal, an organic metal, and a carbon component on the surface in a solid or liquid manner and then heat-treating at 100 to 1200°C, more preferably 200 to 1000°C, and even more preferably 250 to 800°C. In this case, the properties of the positive electrode active material itself are maintained while improving structural stability and electrochemical performance.

[0180] The heat treatment time is preferably 1 to 16 hours, more preferably 3 to 7 hours, and within this range, the properties of the positive electrode active material itself are maintained while improving structural stability and electrochemical performance.

[0181] The above coating method is not particularly limited as long as it is a coating method commonly used in the technical field to which the present invention belongs, and may be, for example, a liquid method in which a liquid coating agent is prepared and mixed with a positive electrode active material, a mechanochemical method using the high mechanical energy of ball milling, a fluidized bed coating method, a spray drying method, a precipitation method in which a coating agent is precipitated onto the surface of a positive electrode active material in an aqueous solution state, a method utilizing a reaction between a gaseous coating agent and a positive electrode active material, or a sputtering method.

[0182]

[0183] The above metal, organic metal, and carbon component may be, for example, spherical, plate-shaped, square, or needle-shaped, and such shapes can be controlled by changing process conditions, etc. during the manufacturing process, and the definition of each shape is not particularly limited as long as it follows the definition commonly recognized in the technical field to which the present invention belongs.

[0184]

[0185] The above coating agent preferably has an average diameter of 1 to 1000 nm and a specific surface area of ​​10 to 100 m 2 / g, and more preferably, the average diameter is 10 to 100 nm, and the specific surface area is 20 to 100 m 2 / g, and within this range, it can be uniformly attached to the surface of the positive electrode active material, thereby imparting structural stability to the positive electrode active material, thereby improving the problems of deterioration of life characteristics and electrochemical performance due to lattice deformation or collapse of crystal structure of the positive electrode active material.

[0186] In the present invention, the average diameter can be measured by a measuring method commonly used in the technical field to which the present invention belongs, and for example, can be measured using a laser diffraction method. Specifically, after dispersing the particles of the positive electrode active material in a dispersion medium, the particles are introduced into a commercially available laser diffraction particle size measuring device such as Microtrac MT 3000, and ultrasonic waves of about 28 kHz are irradiated at an output of 60 W, and the average particle diameter (D50) based on 50% of the particle diameter distribution in the measuring device can be calculated.

[0187] In this description, the specific surface area can be measured by a measurement method commonly used in the technical field to which the present invention belongs, for example, by the BET (Brunauer-Emmett-Teller) method, and specifically, can be calculated from the nitrogen gas adsorption amount under liquid nitrogen temperature (77K) using BELSORP-mino II of BEL Japan.

[0188]

[0189] In addition, the secondary battery of the present invention includes the positive electrode material, and in this case, there is no breakage of the positive electrode material during the electrode manufacturing process, so there is no deterioration in battery performance due to fine particles, and there are advantages of excellent life characteristics in a high-voltage environment, high thermal stability, and low gas generation due to charge and discharge.

[0190] The secondary battery of the present invention may include all of the contents of the positive electrode material described above. Therefore, redundant description thereof is omitted herein.

[0191] The method for manufacturing a secondary battery according to the present invention is not particularly limited if it is a method for manufacturing a lithium secondary battery commonly used in the technical field to which the present invention belongs.

[0192]

[0193] In addition, the method for measuring the particle strength of the cathode material of the present invention comprises the steps of: A) measuring the rolling density of the cathode material using a powder resistance meter between 0 kgf and 2,000 kgf or less; B) measuring the rolling density of the cathode material using a hydraulic press at more than or equal to 2,000 kgf; And C) a step of obtaining EMD by using the absolute difference between the abnormal value of the rolled density and the measured value (del_PD_absolute), the relative difference between the abnormal value of the rolled density and the measured value (del_PD), the inclination difference between the abnormal value of the rolled density and the measured value (del_inclination), or the particle distribution before and after rolling using the Wasserstein_distance function of SciPy (u_values=particle distribution before rolling, v_values=particle distribution after rolling, u_weights=none, v_weights=none). In this case, there is an advantage in that the particle strength of the positive electrode material with high crystallinity can be easily measured.

[0194]

[0195] The above cathode material is preferably represented by the following chemical formula 1

[0196] [Chemical Formula 1]

[0197] Li a Ni x Mn y Co z M w O 2+δ

[0198] (In the above chemical formula 1, M includes at least one selected from the group consisting of B, W, Al, Ti and Mg, and 1 <a≤1.1, 0<x<0.95, 0<y<0.8, 0<z<1.0, 0≤w≤0.1, -0.02≤δ≤0.02, x+y+z+w=1이다.)로 표시되는 화합물일 수 있다.

[0199] The above particles may preferably be single particles.

[0200]

[0201] The above step A) preferably measures the rolling density using a powder resistance meter between 0 and 2,000 kgf load or less, and extends two or more measured rolling densities to determine the rolling density value at the point of 9,000 kgf load as the ideal value (PD) of the rolling density under 9,000 kgf load. i ) may include a step of obtaining the result.

[0202] Specifically, the rolling density according to the load has an ideal linear causal relationship, and the rolling density at more than or equal to 2,000 kgf load, preferably 9,000 kgf load, can be obtained by extending two or more rolling densities measured between or below 2,000 kgf load, which is called the ideal value of rolling density (PD). i ) is referred to as.

[0203]

[0204] The above step B) may be a step of measuring the rolling density of the cathode material using a hydraulic press, preferably between 2,000 kgf and 9,000 kgf, and in this case, there is an advantage in that the particle strength of the cathode material with high crystallinity can be easily measured.

[0205] Specifically, the rolling density of the anode material does not actually have a linear causal relationship, but increases linearly between 2,000 kgf load and below, and then gradually stabilizes between 2,000 kgf load and 9,000 kgf load, showing a logarithmic function. This is the measurement value of rolling density (PD r ) is referred to as.

[0206]

[0207] The relative difference (del_PD) between the above rolling density's abnormal value and the measured value and the particle distribution before and after rolling are measured, and the EMD calculated from SciPy's Wasserstein_distance function is generally proportional or corresponding to the particle strength of the cathode material within the range of particle strength (absolute value) required for the cathode material, so there is an advantage in that the particle strength of the cathode material can be indirectly confirmed (relative value).

[0208]

[0209] The absolute difference between the ideal value of the rolling density and the measured value (del_PD_absolute), the relative difference between the ideal value of the rolling density and the measured value (del_PD), and the inclination difference between the ideal value of the rolling density and the measured value (del_inclination) are generally proportional or corresponding to the particle strength of the positive electrode material within the range of particle strength (absolute value) required for the positive electrode material, so there is an advantage in that the particle strength of the positive electrode material can be indirectly (relative value) confirmed.

[0210] The particle strength (absolute value) range required for the above cathode material may be, for example, 10 to 1000 MPa, preferably 50 to 500 MPa, more preferably 100 to 400 MPa, and even more preferably 100 to 350 MPa, and excellent accuracy is achieved within this range. Here, the particle strength (absolute value) is a value converted to a pressure unit (MPa) by measuring the point at which cracks occur in the particles while gradually increasing the pressure on the cathode material particles.

[0211]

[0212] In the above step C), EMD can be obtained by measuring the particle distribution before and after rolling, for example, and using this, using the Wasserstein_distance function of SciPy from the distance between particle distributions.

[0213]

[0214] The method for measuring particle strength of the cathode material of the present invention can encompass all of the contents of the cathode material and the secondary battery containing the same described above. Therefore, redundant description thereof is omitted herein.

[0215] In addition, in order to easily convey the method for measuring the particle strength of the cathode material of the present invention to a person skilled in the art, only the conditions and devices absolutely necessary are described, and other self-evident auxiliary conditions and devices are omitted.

[0216]

[0217] Hereinafter, preferred examples are presented to help understand the present invention, but the following examples are only illustrative of the present invention, and it is obvious to those skilled in the art that various changes and modifications are possible within the scope and technical idea of ​​the present invention, and it is also natural that such changes and modifications fall within the scope of the appended patent claims.

[0218]

[0219] [Example]

[0220] Example 1

[0221] Ni x Mn y Co z (OH)2 and LiOH were mixed so that the molar ratio of transition metal (Ni+Mn+Co): Li was 1:1.05, the molar ratio of transition metal (Ni+Mn+Co): Ni was 0.700, and the molar ratio of Mn / Co was 1.9, and calcined at 850°C for 12 hours to obtain a cathode active material LiNi having a particle size of 227.6 nm. 0.700 Mn y Co z O2 was manufactured, and it was confirmed using a scanning electron microscope (SEM) that the manufactured positive electrode active material was a single particle.

[0222]

[0223] Examples 2 to 18

[0224] Ni of the above Example 1 x Mn y Co zA positive electrode active material having a particle size shown in Table 1 was manufactured in the same manner as in Example 1, except that the molar ratio of transition metal (Ni+Mn+Co): Li, the molar ratio of transition metal (Ni+Mn+Co): Ni, and the molar ratio of Mn / Co in (OH)2 and LiOH were changed as described in Table 1 below. In addition, the particle types of the manufactured positive electrode active material were confirmed using a scanning electron microscope (SEM) and are shown in Table 1.

[0225]

[0226] Comparative Example 1

[0227] Ni x Mn y Co z (OH)2 and LiOH were mixed so that the molar ratio of transition metal (Ni+Co+Mn): Li was 1:1.06, the molar ratio of transition metal (Ni+Mn+Co): Ni was 0.87, and the molar ratio of Mn / Co was 1.4, and calcined at 850°C for 12 hours to obtain a cathode active material LiNi having a particle size of 109.5 nm. 0.87 Mn y Co z O2 was manufactured, and it was confirmed using a scanning electron microscope (SEM) that the manufactured positive electrode active material was a secondary particle.

[0228]

[0229] Comparative Examples 2 to 18

[0230] Ni of the above comparative example 1 x Mn y Co z A positive electrode active material having a particle size shown in Table 2 was manufactured in the same manner as in Comparative Example 1, except that the molar ratio of transition metal (Ni+Mn+Co): Li, the molar ratio of transition metal (Ni+Mn+Co): Ni, and the molar ratio of Mn / Co in (OH)2 and LiOH were changed as described in Table 2 below. In addition, the particle types of the manufactured positive electrode active material were confirmed using a scanning electron microscope (SEM) and are shown in Table 2.

[0231]

[0232] [Example Exam I]

[0233] The characteristics of the positive electrode active materials manufactured in Examples 1 to 18 and Comparative Examples 1 to 18 were measured by the following methods, and the results are shown in Tables 1 and 2 below.

[0234] * ICP Analysis: Using an ICP analyzer, the ratio of lithium (Li) to transition metal (Me), the ratio of nickel to transition metal, the ratio of Mn / Co, and the content of specific elements (mg / kg) in the positive electrode active material were measured. At this time, measurements can be made using a general ICP analyzer widely used in laboratories, and there is no deviation depending on the measuring device or method.

[0235] * Particle size (crystal size): Measured by XRD crystal analysis. Specifically, approximately 5 to 10 g of positive electrode active material particles were placed in a holder, X-rays were irradiated on the particles, and the resulting diffraction grating was analyzed. This can be measured using a general X-ray diffraction analyzer, and there is no deviation depending on the measuring device or method.

[0236]

[0237] Distinctive particle shapeLi molar ratio (Ni+Mn+Co=1 mol)Ni molar ratio (Ni+Mn+Co=1 mol)Mn / Co molar ratioParticle size (nm)Example 1 Single particle 1.050.701.9227.6Example 2 Single particle 1.030.850.7217.9Example 3 Single particle 1.050.861.6256.9Example 4 Single particle 1.050.71227.6Example 5 Single particle 1.030.851217.9Example 6 Single particle 1.050.861256.9Example 7 Single particle 1.050.71.3227.6Example 8 Single particle 1.030.851.3217.9Example 9 Single particle 1.050.861.3256.9 Example 10 Single particle 1.050.71.7227.6 Example 11 Single particle 1.030.851.7217.9 Example 12 Single particle 1.050.861.7256.9 Example 13 Single particle 1.050.72227.6 Example 14 Single particle 1.030.852217.9 Example 15 Single particle 1.050.862256.9 Example 16 Single particle 1.050.72.3227.6 Example 17 Single particle 1.030.852.3217.9 Example 18 Single particle 1.050.862.3256.9

[0238] Distinctive particle shapeLi molar ratio(Ni+Mn+Co=1 mol)Ni molar ratio(Ni+Mn+Co=1 mol)Mn / Co molar ratioParticle size(nm)Comparative example 1Secondary particle1.060.871.4109.5Comparative example 2Secondary particle1.050.881.4108.8Comparative example 3Single particle1.060.871.5214.3Comparative example 4Secondary particle1.060.871109.5Comparative example 5Secondary particle1.060.871.3109.5Comparative example 6Secondary particle1.060.871.7109.5Comparative example 7Secondary particle1.060.872109.5Comparative example 8 Secondary particle 1.06 0.87 2.3 10 9.5 Comparative example 9 Secondary particle 1.05 0.88 1 10 8.8 Comparative example 10 Secondary particle 1.05 0.88 1.3 10 8.8 Comparative example 11 Secondary particle 1.05 0.88 1.7 10 8.8 Comparative example 12 Secondary particle 1.05 0.88 2 10 8.8 Comparative example 13 Secondary particle 1.05 0.88 2.3 10 8.8 Comparative example 14 Single particle 1.06 0.87 1 2 14.3 Comparative example 15 Single particle 1.06 0.87 1.3 2 14.3 Comparative example 16 Single particle 1.06 0.87 1.7 2 14.3 Comparative example 17 Single particle 1.06 0.87 2 2 14.3 Comparative example 18-particle 1.060.872.3214.3

[0239] As shown in Tables 1 and 2 above, it was confirmed that the positive electrode active materials (Examples 1 to 18) according to the present invention, compared to the positive electrode active materials of Comparative Examples 1 to 18, satisfied the following conditions: a monomodal particle size distribution, a molar ratio of the total transition metal to lithium of 1:1 to 1.05, a crystal size of 216.2 nm or more measured by XRD, nickel (Ni) of 65 mol% or more based on 100 mol% of the total metals excluding Li, and a molar ratio of cobalt to manganese of 1:0.5 to 2.5.

[0240]

[0241] [Exam Example II]

[0242] The characteristics of the positive electrode active materials manufactured in Examples 1 to 18 and Comparative Examples 1 to 18 were measured by the following methods, and the results are shown in Tables 3 and 4 below.

[0243] * del_PD_absolute, del_PD and del_inclination: 5g of the manufactured positive electrode active material powder was placed in a Φ1cm mold of a powder resistance measuring device and the rolling density was measured under loads of 400kgf, 800kgf, 1200kgf, 1600kgf and 2000kgf. Then, 3g of the manufactured positive electrode active material powder prepared separately was placed in a Φ12.9mm mold of a hydraulic press and the rolling density was measured under a load of 9000 kgf.

[0244] As shown in Figures 1 to 3 below, the rolling density values ​​(measured values; blue points or dark points) under loads of 400 kgf, 800 kgf, 1200 kgf, 1600 kgf, 2000 kgf, and 9000 kgf were plotted on the diagram, and a straight line was drawn between them to obtain a graph of measured values ​​(blue straight line or dark straight line). Next, a straight line (linear function, brown line, or light line) passing through the measured rolling density values ​​under loads of 400 kgf and 2000 kgf was drawn, and the rolling density value at the point of load of 9000 kgf on the straight line was obtained as an ideal value (brown point or light point) of rolling density under load of 9000 kgf.

[0245] The values ​​described in the completed graph above were substituted into the following mathematical equations 5 to 9 to obtain the del_PD_absolute, del_PD, and del_inclination values.

[0246] [Equation 5]

[0247] del_PD_absolute = PD i - PD r

[0248] (PD here i is the ideal value of rolling density under x kgf load, and PD r is a measure of rolling density under x kgf load, where x is 9000.)

[0249]

[0250] [Equation 6]

[0251] del_PD = (PD i - PD r ) / PD i

[0252] (PD here i is the ideal value of rolling density under x kgf load, and PD r is a measure of rolling density under x kgf load, where x is 9000.)

[0253]

[0254] [Equation 7]

[0255] del_inclination = inclination(i) - inclination(r)

[0256] (In this equation, inclination(i) is the slope of the outliers, and inclination(r) is the slope of the measurements.)

[0257]

[0258] [Equation 8]

[0259] Inclination(i) = (PD i (x)- PD i (y) / (xy)

[0260] (PD here i (x) is the ideal value of rolling density under x kgf load, and PD i (y) is the ideal value of rolling density under y kgf load, satisfying x>y, x is 9000, and y is 400 or 2000.)

[0261]

[0262] [Equation 9]

[0263] Inclination(r) = (PD r (x) - PD r (y) / (xy)

[0264] (PD here r (x) is the measurement of rolling density under x kgf load, and PD r(y) is the measurement of rolling density under y kgf load, satisfying x>y, x is 9000, and y is 2000.)

[0265]

[0266] * EMD: The manufactured positive electrode active material powder was measured with a particle size analyzer before and after rolling under a load of 9000 kgf, and PSD (Particle Size Distribution) graphs for each were obtained as shown in Figures 4 and 5 below. Then, the values ​​shown in the graphs were substituted into the Wasserstein_distance function of SciPy (u_values ​​= particle distribution before rolling, v_values ​​= particle distribution after rolling, u_weights = none, v_weights = none).

[0267]

[0268] Classification del_ PD_absolutedel_PDEMDdel_inclin.(1 - del_PD) / EMD Example 11.1150.2440.0370.15920.315 Example 21.3210.2760.0640.18911.368 Example 31.3490.2780.0190.19338.489 Example 41.1150.2440.0370.15920.315 Example 51.3210.2760.0640.18911.368 Example 61.3490.2780.0190.19338.489 Example 71.1150.2440.0370.15920.315 Example 81.3210.2760.0640.18911.368 Example 91.3490.2780.0190.19338.489 Example 101.1150.2440.0370.15920.315 Example 111.3210.2760.0640.18911.368 Example 121.3490.2780.0190.19338.489 Example 131.1150.2440.0370.15920.315 Example 141.3210.2760.0640.18911.368 Example 151.3490.2780.0190.19338.489 Example 161.1150.2440.0370.15920.315 Example 171.3210.2760.0640.18911.368 Example 181.3490.2780.0190.19338.489

[0269] Classification del_ PD_absolutedel_PDEMDdel_inclin.(1 - del_PD) / EMDComparative Example 10.3430.0920.5430.0491.673Comparative Example 20.3520.0940.4720.0501.921Comparative Example 31.5960.3120.0780.2288.782Comparative Example 40.3430.0920.5430.0491.673Comparative Example 50.3430.0920.5430.0491.673Comparative Example 60.3430.0920.5430.0491.673Comparative Example 70.3430.0920.5430.0491.673Comparative Example 80.3430.0920.5430.0491.673Comparative example 90.3520.0940.4720.0501.921Comparative example 100.3520.0940.4720.0501.921Comparative example 110.3520.0940.4720.0501.921Comparative example 120.3520.0940.4720.0501.921Comparative example 130.3520.0940.4720.0501.921Comparative example 141.5960.3120.0780.2288.782Comparative example 151.5960.3120.0780.2288.782Comparative example 161.5960.3120.0780.2288.782Comparative example 171.5960.3120.0780.2288.782Comparative example 181.5960.3120.0780.2288.782

[0270] As shown in Tables 3 and 4 above, it was confirmed that the positive electrode active materials (Examples 1 to 18) according to the present invention, unlike the positive electrode active materials of Comparative Examples 1 to 18, satisfy both the mathematical formulas 1 to 4 and the EDM range according to the present invention.

[0271] In particular, the positive electrode active materials of Comparative Examples 3 and 14 to 18, despite being single particles, did not satisfy mathematical equations 1 to 4 according to the present invention, and it was confirmed that even if they are single particles, if they do not satisfy mathematical equations 1 to 4 according to the present invention, the life characteristics become poor.

[0272]

[0273] In addition, the following Figures 1 to 3 are graphs showing the rolling density of the positive electrode active materials manufactured in Example 1 and Comparative Examples 1 to 2 as ideal values ​​and measured values, respectively, depending on the load. The measured values ​​are indicated by brown dots and lines or light dots and lines, and the ideal values ​​are indicated by blue dots and lines or dark dots and lines. From these values, it was confirmed that the positive electrode active material of Example 1 satisfies the mathematical formulas 1 to 4 according to the present invention, whereas the positive electrode active materials of Comparative Examples 1 to 2 do not satisfy all of the mathematical formulas 1 to 4 according to the present invention.

[0274] In addition, as shown in FIGS. 4 and 5 below, FIGS. 4 and 5 are graphs showing the particle size distribution before and after rolling of the positive electrode active materials manufactured in Example 1 and Comparative Example 2, respectively. In the positive electrode active material of Example 1, the particle size distribution shape before and after rolling did not change and the peak shifted little, but in the positive electrode active material of Comparative Example 2, the particle size distribution before and after rolling changed from a monomodal to a bimodal shape and the peak shifted significantly.

[0275]

[0276] [Experimental Example III: Coin Half-Cell (CHC) Evaluation]

[0277] The electrochemical performance of the positive electrode active materials manufactured in Examples 1 to 18 and Comparative Examples 1 to 18 was measured through the CHC cell evaluation as follows, and the results are shown in Tables 5 and 6 below.

[0278]

[0279] * Manufacturing of Coin Half Cells (CHC): 96.5 wt% of positive electrode active material, 1.5 wt% of carbon black, and 2 wt% of PVdF were weighed and mixed with NMP to make a slurry. This was applied to a 20 ㎛ thick aluminum foil, dried at 130°C for 1 hour, and then stamped to manufacture a positive electrode, thereby manufacturing a coin half cell (CHC).

[0280]

[0281] * High temperature (45 ℃) lifetime capacity retention rate: After forming each manufactured coin half-cell at a 0.1C rate, the voltage was set to 2.5 to 4.25 V at high temperature (45 ℃), and 50 charge / discharge cycles were performed at 0.33C / 0.33C. The discharge capacity after one cycle and the discharge capacity after 50 cycles were measured (using a PNE-0506 charger / discharger (manufacturer: PNE Solution Co., Ltd., 5V, 6A), and the discharge capacity after one cycle was set as the initial capacity.

[0282] Afterwards, the 50th discharge capacity and the initial discharge capacity were compared to calculate the high-temperature capacity retention rate as a high-temperature life characteristic using the following mathematical expression 10, and the results are shown in Tables 5 and 6 below.

[0283] [Equation 10]

[0284] High temperature capacity retention rate (%) = (discharge capacity after high temperature cycle / initial discharge capacity)*100

[0285]

[0286] Classification High temperature life capacity retention rate (%) Example 195.214 Example 294.999 Example 396.078 Example 494.767 Example 595.579 Example 695.663 Example 795.145 Example 895.941 Example 995.974 Example 1095.282 Example 1196.131 Example 1296.072 Example 1395.150 Example 1496.093 Example 1595.948 Example 1694.850 Example 1795.934 Example 1895.688

[0287] Classification High temperature life capacity retention rate (%) Comparison example 192.296 Comparison example 292.649 Comparison example 393.869 Comparison example 492.447 Comparison example 592.307 Comparison example 692.386 Comparison example 792.686 Comparison example 893.224 Comparison example 992.834 Comparison example 1092.672 Comparison example 1192.687 Comparison example 1292.910 Comparison example 1393.350 Comparison example 1493.682 Comparison example 1593.874 Comparison example 1693.792 Comparison example 1793.517 Comparison example 1893.093

[0288] As shown in Tables 5 and 6 above, the secondary batteries including the cathode materials according to the present invention (Examples 1 to 18) have excellent high-temperature life characteristics with a high-temperature capacity retention rate of 94.8% or more, more precisely, in the range of 94.8 to 97% for CHC, but it was confirmed that the CHC including the cathode materials of Comparative Examples 1 to 18 has a poor high-temperature life capacity retention rate of 93.9% or less.

Claims

1. At least one selected from the group consisting of lithium cobalt oxide; lithium manganese oxide; lithium iron phosphate compound; lithium nickel cobalt aluminum oxide (NCA); lithium nickel oxide (LNO); nickel manganese-based lithium composite metal oxide in which a portion of nickel (Ni) in the lithium nickel oxide is replaced with manganese (Mn); lithium composite transition metal oxide (NCM) in which a portion of nickel (Ni) in the lithium nickel oxide is replaced with manganese (Mn) and cobalt (Co); and lithium composite transition metal oxide (NCMA) in which aluminum (Al) is added to the lithium composite transition metal oxide (NCM). Mathematical formulas 1 to 4 below [Mathematical Formula 1] 1.58 ≥ del_PD_absolute ≥ 1 (Here, del_PD_absolute is the difference between the absolute value of the ideal and measured rolling density when the load is 9,000 kgf.) [Equation 2] 0.3 ≥ del_PD ≥ 0.2 (Here, del_PD is the difference between the ideal and measured values ​​of rolling density (normalized value) when the load is 9,000 kgf.) [Equation 3] 0.21 ≥ del_inclination ≥ 0.15 (Here, del_inclination is the difference in inclination between the ideal and measured values ​​of rolling density between 0 and 9,000 kgf load.) [Equation 4] (1 - del_PD) / EMD ≥ 10.1 (Here, del_PD is the difference between the ideal value of the rolling density and the measured value (normalized value) when the load is 9,000 kgf, and EMD (Earth Mover's Distance) is a value obtained using SciPy's Wasserstein_distance function (u_values ​​= particle distribution before rolling, v_values ​​= particle distribution after rolling, u_weights = none, v_weights = none).) characterized by satisfying at least one of the following: Bipolar material.

2. In paragraph 1, The above cathode material is characterized by having a monomodal particle size distribution. Bipolar material.

3. In paragraph 1, The above cathode material is characterized in that the molar ratio of the entire transition metal and lithium is 1:1 to 1.

05. Bipolar material.

4. In paragraph 1, The above cathode material is characterized in that the crystal size measured by XRD is 216.2 nm or more. Bipolar material.

5. In paragraph 1, The above cathode material contains nickel (Ni) and is characterized in that it contains nickel (Ni) in an amount of 65 mol% or more based on 100 mol% of the total metals excluding lithium (Li). Bipolar material.

6. In paragraph 1, The above cathode material contains cobalt (Co) and manganese (Mn), and is characterized in that the molar ratio of cobalt and manganese is 1:0.5 to 2.

5. Bipolar material.

7. In paragraph 1, The above cathode material has the following chemical formula 1 [Chemical Formula 1] Li a Ni x Mr y Co z M w O 2+δ (In the above chemical formula 1, M includes at least one selected from the group consisting of B, W, Al, Ti and Mg, and 1 <a≤1.1, 0<x<0.95, 0<y<0.8, 0<z<1.0, 0≤w≤0.1, -0.02≤δ≤0.02, x+y+z+w=1이다.)로 표시되는 화합물인 것을 특징으로 하는 Bipolar material.

8. In paragraph 1, The above cathode material is characterized in that the EDM (Earth Mover's Distance) value obtained using SciPy's Wasserstein_distance function (u_values ​​= particle distribution before rolling, v_values ​​= particle distribution after rolling, u_weights = none, v_weights = none) is 0.071 or less. Bipolar material.

9. In paragraph 1, The above cathode material is characterized by being a single particle. Bipolar material.

10. In paragraph 1, The above cathode material is characterized in that the surface is coated with a coating agent containing metal or carbon. Bipolar material.

11. Characterized in that it comprises the cathode material of any one of claims 1 to 10. Secondary battery. 12.A) A step of measuring the rolling density of the cathode material using a powder resistance meter between 0 kgf load and 2,000 kgf load or less; B) A step of measuring the rolling density of the cathode material using a hydraulic press at over 2,000 kgf load or more; and C) A step of obtaining EMD by using the rolling density of the cathode material measured in steps A) and B) to obtain the absolute difference between the ideal value of the rolling density and the measured value (del_PD_absolute), the relative difference between the ideal value of the rolling density and the measured value (del_PD), the inclination difference between the ideal value of the rolling density and the measured value (del_inclination), or the particle distribution before and after rolling, and using the Wasserstein_distance function of SciPy (u_values=particle distribution before rolling, v_values=particle distribution after rolling, u_weights=none, v_weights=none). Method for measuring particle strength of cathode material.

13. In paragraph 12, The above cathode material has the following chemical formula 1 [Chemical Formula 1] Li a Ni x Mr y Co z M w O 2+δ (In the above chemical formula 1, M includes at least one selected from the group consisting of B, W, Al, Ti and Mg, and 1 <a≤1.1, 0<x<0.95, 0<y<0.8, 0<z<1.0, 0≤w≤0.1, -0.02≤δ≤0.02, x+y+z+w=1이다.)로 표시되는 화합물인 것을 특징으로 하는 Method for measuring particle strength of cathode material.

14. In paragraph 12, The above particle is characterized in that it is a single particle. Method for measuring particle strength of cathode material.

15. In paragraph 12, The above step B) is characterized in that it is a step of measuring the rolling density of the positive electrode material using a hydraulic press between 2,000 kgf load or more and 9,000 kgf load. Method for measuring particle strength of cathode material.

Images