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

Abstract

The present invention relates to a positive electrode active material, a method for manufacturing same, and a positive electrode and a lithium secondary battery comprising same, wherein the positive electrode active material comprises a lithium composite transition metal oxide which is in the form of a single particle consisting of 10 or less primary particles and contains 50 mol % or more of nickel among all metals except lithium. The positive electrode active material has a single crystallinity (χ) of 0.500 or more and 0.850 or less according to formula 1 described in the present specification, and a crystal grain size (D) of 2.00 ㎛ or more and 5.00 ㎛ or less.

Description

Positive electrode active material, method for producing the same, and positive electrode and lithium secondary battery including the same

[0001] Cross-citation with related applications

[0002] This application claims the benefit of priority from Korean Patent Application No. 10-2023-0151122, filed November 3, 2023, the entire contents of which are incorporated herein by reference.

[0003] Technology field

[0004] The present invention relates to a positive electrode active material, a method for producing the same, and a positive electrode and a lithium secondary battery including the same.

[0005]

[0006] A lithium secondary battery is generally composed of a positive electrode, a negative electrode, a separator, and an electrolyte, and the positive electrode and negative electrode include an active material capable of intercalating and deintercalating lithium ions.

[0007] Lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), lithium manganese oxide (LiMnO2 or LiMnO4, etc.), and lithium iron phosphate compound (LiFePO4) have been used as cathode active materials for lithium secondary batteries. Among these, lithium cobalt oxide has the advantages of high operating voltage and excellent capacity characteristics, but the high price of cobalt, which is the raw material, and its supply are unstable, making it difficult to commercially apply it to large-capacity batteries. Lithium nickel oxide has poor structural stability, making it difficult to achieve sufficient cycle life characteristics. Meanwhile, lithium manganese oxide has excellent stability but has the problem of poor capacity characteristics. Therefore, lithium composite transition metal oxides containing two or more transition metals have been developed to complement the problems of lithium transition metal oxides containing only Ni, Co, or Mn. Among these, lithium composite transition metal oxides containing Ni, Co, and Mn are widely used in the field of electric vehicle batteries.

[0008] Recently, the demand for high-power, high-capacity batteries, such as those for electric vehicles, has been increasing, and accordingly, the nickel content in lithium composite transition metal oxides is gradually increasing. When the nickel content in lithium composite transition metal oxides increases, the initial capacity characteristics are improved, but when charge and discharge are repeated, the highly reactive Ni +4 There is a problem that a large amount of ions are generated, causing structural collapse of the positive electrode active material, which increases the rate of deterioration of the positive electrode active material, resulting in a decrease in life characteristics and battery safety.

[0009] In addition, conventional lithium composite transition metal oxides were generally in the form of spherical secondary particles in which tens to hundreds of primary particles were aggregated. However, in the case of lithium composite transition metal oxides in the form of secondary particles in which many primary particles are aggregated, there is a problem in that the primary particles are likely to fall off during the rolling process during the manufacture of the positive electrode, i.e., particle breakage occurs easily, and cracks occur inside the particles during the charge and discharge process. When particle breakage or cracks occur in the positive electrode active material, the contact area with the electrolyte increases, causing a side reaction with the electrolyte, and there is a problem in that gas generation and active material degradation increase, resulting in a decrease in life characteristics.

[0010] To address the above issues, a technique has been proposed for producing single-particle cathode active materials rather than secondary particles by increasing the sintering temperature during the production of lithium composite transition metal oxides. Single-particle cathode active materials have a smaller contact area with the electrolyte than conventional secondary-particle cathode active materials, resulting in less side reactions with the electrolyte and superior particle strength, which reduces particle breakage during electrode production. Therefore, the application of single-particle cathode active materials offers the advantages of superior gas generation and cycle life characteristics.

[0011] However, lithium composite transition metal oxide particles in the form of single particles have relatively large primary particles compared to conventional secondary particle-type lithium composite transition metal oxide particles, and the interfaces between the primary particles, which serve as diffusion paths for lithium ions, are small, so that lithium mobility is low. In addition, since they are manufactured at a relatively high sintering temperature, a rock salt phase is formed on the particle surface, resulting in high surface resistance. In addition, lithium composite transition metal oxide particles in the form of single particles have high lithium diffusion resistance, and lithium ion movement occurs unevenly during charge and discharge, which easily causes crystal structure deformation and particle cracks, which lowers battery performance.

[0012]

[0013] [Prior Art Literature]

[0014] [Patent Document]

[0015] (Patent Document 1) Korean Patent Publication No. 10-2019-0131842

[0016]

[0017] The present invention is intended to solve the above problems, and to provide a positive electrode active material and a method for manufacturing the same, which can improve the rolling density of the positive electrode active material while improving the output characteristics, rate characteristics, resistance characteristics, etc. of the battery.

[0018] In addition, the present invention seeks to provide a positive electrode and a lithium secondary battery having excellent energy density, output characteristics, rate characteristics, resistance characteristics, etc., including the positive electrode active material as described above.

[0019]

[0020] (1) The present invention provides a cathode active material having a single particle form composed of 10 or fewer primary particles, including a lithium composite transition metal oxide containing nickel in an amount of 50 mol% or more among all metals excluding lithium, and having a single crystallinity (χ) according to the following formula 1 of 0.500 or more and 0.850 or less, and a crystal grain size (D) of 2.00 ㎛ or more and 5.00 ㎛ or less.

[0021] [Formula 1]

[0022]

[0023] (2) The present invention provides a positive electrode active material in the above (1), wherein the lithium composite transition metal oxide has a composition represented by the following chemical formula 1.

[0024] [Chemical Formula 1]

[0025] Li 1+x Ni a Co b Mn c M 1 d O2

[0026] In the above chemical formula 1,

[0027] Above M 1 is at least one selected from Al, W, Co, B, Zr, Y, Ce, Hf, La, Ba, F, P, S, Nb, Ta, Sc, Cr, V, Cu, Sr, Ti, Mg, Mo, Sn, Fe, Zn and Si,

[0028] -0.10≤x≤0.10, 0.500≤a<1.000, 0 <b<0.500, 0<c<0.500, 0≤d≤0.100, a+b+c+d=1이다.

[0029] (3) The present invention provides a cathode active material in (1) or (2), wherein the lithium composite transition metal oxide includes at least one doping element selected from Al, W, Co, B, Zr, Y, Ce, Hf, La, Ba, F, P, S, Nb, Ta, Sc, Cr, V, Cu, Sr, Ti, Mg, Mo, Sn, Fe, Zn and Si.

[0030] (4) The present invention is characterized in that the average particle diameter (D) of the primary particles is in any one of the above (1) to (3). 50 ) provides a positive electrode active material having a diameter of 2.35㎛ or more and 6.00㎛ or less.

[0031] (5) The present invention provides a positive electrode comprising a positive electrode active material according to any one of (1) to (4).

[0032] (6) The present invention provides a lithium secondary battery including a positive electrode according to (5) above.

[0033]

[0034] The cathode active material according to the present invention is in the form of a single particle, includes a lithium composite transition metal oxide containing nickel in an amount of 50 mol% or more among all metals excluding lithium, has a single crystallinity within a specific range, and has a crystal grain size within a specific range, thereby having the effect of improving the energy density, output characteristics, rate characteristics, and resistance characteristics of a battery including the same.

[0035] Accordingly, the performance of the positive electrode and secondary battery including the positive electrode active material, particularly the energy density, output characteristics, and resistance characteristics, can be improved.

[0036]

[0037] Figure 1 is a SEM image of the positive electrode active material manufactured in Example 1.

[0038] Figure 2 is a SEM image of the positive electrode active material manufactured in Example 2.

[0039] Figure 3 is an SEM image of the positive electrode active material manufactured in Comparative Example 1.

[0040] Figure 4 is an SEM image of the positive electrode active material manufactured in Comparative Example 2.

[0041] Figure 5 is an SEM image of the positive electrode active material manufactured in Comparative Example 3.

[0042] Figure 6 is an SEM image of the positive electrode active material manufactured in Comparative Example 4.

[0043] Figure 7 is an IPF map obtained by EBSD analysis of a positive electrode for EBSD analysis manufactured using the positive electrode active material manufactured in Example 1.

[0044] Figure 8 is an IPF map obtained by EBSD analysis of a positive electrode for EBSD analysis manufactured using the positive electrode active material manufactured in Example 2.

[0045] Figure 9 is an IPF map obtained by EBSD analysis of a positive electrode for EBSD analysis manufactured using the positive electrode active material manufactured in Comparative Example 1.

[0046] Figure 10 is an IPF map obtained by EBSD analysis of a positive electrode for EBSD analysis manufactured using the positive electrode active material manufactured in Comparative Example 2.

[0047] Figure 11 is an IPF map obtained by EBSD analysis of a positive electrode for EBSD analysis manufactured using the positive electrode active material manufactured in Comparative Example 3.

[0048] Figure 12 is an IPF map obtained by EBSD analysis of a positive electrode for EBSD analysis manufactured using the positive electrode active material manufactured in Comparative Example 4.

[0049]

[0050] Hereinafter, the present invention will be described in more detail to help understand the present invention.

[0051] 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.

[0052] It should be understood that the terms “include,” “have,” or “have” used in this specification are intended to specify the presence of a feature, number, step, component, or combination thereof, but do not preclude the possibility of the presence or addition of one or more other features, numbers, steps, components, or combinations thereof.

[0053] In the present specification, the single particle form includes both a single particle form of the positive electrode active material and / or a lithium composite transition metal oxide and a form in which two or more but less than ten primary particles are aggregated. That is, the single particle form of the positive electrode active material and / or the single particle form of the lithium composite transition metal oxide of the present invention may include at least one selected from the group consisting of a single particle form of the positive electrode active material and / or a particle form of an aggregated particle form of two or more but less than ten primary particles.

[0054] In this specification, 'primary particle' means the smallest particle unit recognized when observing a positive electrode active material using a scanning electron microscope (SEM), and 'secondary particle' means a secondary structure formed by the aggregation of multiple primary particles.

[0055] In this specification, "crystal grain" refers to a particle unit having substantially the same crystal orientation, which may be measured by Electron Backscatter Diffraction (EBSD). Specifically, it refers to the smallest particle unit displayed in the same color in an IPF map obtained by EBSD analysis of a cross-section of a positive electrode active material cut through ion milling.

[0056] In this specification, the particle size of the primary particles may be calculated by calculating the area of ​​each primary particle through the number of pixels corresponding to each of n primary particles present in the SEM image, and calculating the particle size of each primary particle present in the SEM image using the radius of a circle having the same area as the area of ​​each primary particle. In addition, in this specification, the average particle size of the primary particles (D 50 ) can be defined as the particle size corresponding to 50% of the volume cumulative distribution in the particle size distribution curve (graph curve of particle size distribution) of each particle. The average particle size (D) of the primary particles 50 ) can be measured by taking the volume of a sphere whose radius is half of the particle diameter of the primary particle as the volume of the primary particle, and then calculating the particle diameter at the point where 50% of the cumulative volume distribution according to the particle diameter in the result of calculating the volume of the primary particle is obtained.

[0057] In this specification, the grain size (D) may be the arithmetic mean of the grain diameters. The grain diameter can be measured through image analysis. Specifically, an IPF map of the particle is obtained using EBSD, the grain diameter is calculated based on the grain area identified in the obtained map image, and then the arithmetic mean of these is taken to calculate the grain size.

[0058] In this specification, the content of each element in the lithium composite transition metal oxide may be measured through ICP (Inductive Coupled Plasma) analysis using an inductively coupled plasma optical emission spectrometer (ICP-OES; Agilent 5100, Agilent Technologies).

[0059]

[0060] positive electrode active material

[0061] Hereinafter, the positive electrode active material according to the present invention will be described.

[0062]

[0063] The cathode active material according to the present invention is in the form of a single particle composed of 10 or fewer primary particles, and includes a lithium composite transition metal oxide containing nickel in an amount of 50 mol% or more among all metals excluding lithium, and has a single crystallinity (χ) according to the following formula 1 of 0.500 or more and 0.850 or less, and a crystal grain size (D) of 2.00 ㎛ or more and 5.00 ㎛ or less.

[0064] [Formula 1]

[0065]

[0066]

[0067] Meanwhile, in the case of a cathode active material in which the lithium composite transition metal oxide is not in the form of a single particle composed of 10 or fewer primary particles, contains less than 50 mol% of nickel among the total metals excluding lithium, has a single crystallinity of less than 0.500 or greater than 0.850 according to the above formula 1, and has a grain size (D) of less than 2.00 ㎛ or greater than 5.00 ㎛, there were problems in that the energy density was inferior, and the output characteristics, rate characteristics, and resistance characteristics were inferior.

[0068] The present inventors have conducted repeated research to develop a positive electrode active material having excellent output characteristics, rate characteristics, and resistance characteristics, and as a result, they have found that in the case of a positive electrode active material having a single particle form of 10 or fewer primary particles, including a lithium composite transition metal oxide containing nickel in an amount of 50 mol% or more among all metals excluding lithium, having a single crystallinity (χ) according to Equation 1 described herein of 0.500 or more and 0.850 or less, and having a grain size (D) according to Equation 1 described herein of 2.00 ㎛ or more and 5.00 ㎛ or less, the lithium mobility can be improved by controlling the interface between the grains, which serve as the migration path of lithium ions within the positive electrode active material particles, while increasing the rolling density, and thus completed the present invention. As described above, a battery applying the positive electrode active material according to the present invention can have excellent energy density, output characteristics, rate characteristics, and resistance characteristics.

[0069] The lithium composite transition metal oxide is in the form of a single particle composed of 10 or fewer primary particles. That is, the lithium composite transition metal oxide is in the form of a single particle or a single particle in which 2 to 10 particles are aggregated. The single particle form is distinguished from a secondary particle in which more than 10 primary particles are aggregated. When the lithium composite transition metal oxide has a single particle form, it has excellent stability, so that even when a positive electrode active material including the lithium composite transition metal oxide is rolled, the positive electrode active material does not break or crack. This can reduce side reactions between the positive electrode active material and the electrolyte, and can improve the life characteristics of a battery using the lithium composite transition metal oxide. On the other hand, when the lithium composite transition metal oxide is in the form of a secondary particle, the particle strength is low, so that when the electrode is manufactured and rolled, there is a problem that the particle breakage is severe, and when the cell is operated, a large amount of gas is generated, resulting in poor stability and life characteristics.

[0070]

[0071] The above lithium composite transition metal oxide contains nickel in an amount of 50 mol% or more among all metals excluding lithium. Specifically, it contains nickel in an amount of 50 mol% or more, 55 mol% or more, 60 mol% or more, or 61 mol% or more among all metals excluding lithium. When nickel in the total metals excluding lithium is within the above range, high capacity characteristics can be realized. When nickel in the total metals excluding lithium is less than 50 mol%, there is a problem of poor capacity characteristics.

[0072]

[0073] The inventors of the present invention evaluated the degree of single crystallinity and expressed it as a parameter represented by the above formula 1. The degree of single crystallinity in the present invention is the size (D) of the crystal grains forming the single particle and the average particle diameter (D) of the primary particles forming the lithium composite transition metal oxide which is the single particle. 50 ) is a value that is adjusted according to the crystal grain size (D). The crystal grain size (D) was measured using an EBSD device, and the average particle diameter of the primary particles (D 50 ) was measured using a scanning electron microscope (SEM). Considering that the size of the crystal grains is large, specifically, when the size of the crystal grains is 150 to 200 nm or more, it is difficult to trust the XRD data using FWHM, so the size of the crystal grains was measured using an EBSD device, and considering that the lithium composite transition metal oxide is a single particle, specifically, in order to distinguish adjacent single particles, the average particle diameter of the primary particles was measured using a scanning electron microscope (SEM), and the above equation 1 was derived.

[0074] First, in the above equation 1, the grain size (D) refers to the average of the grain sizes measured by backscatter electron diffraction (EBSD) analysis of the electrode cross-section obtained by ion milling an electrode manufactured by applying the positive electrode active material. Specifically, the area of ​​each grain is calculated through the number of pixels corresponding to each of n grains present in the image of the IPF map obtained by EBSD analysis, and the diameter of a circle having the same area as the area of ​​each grain is used as the grain size. The grain size (D) refers to the arithmetic average value of the grain sizes, and the value can be obtained through the software of the EBSD device.

[0075] In the above equation 1, the average particle diameter of the primary particles (D 50 ) refers to the diameter of the primary particle at the point where 50% of the volume cumulative distribution according to the primary particle diameter obtained by analyzing the SEM image of the positive electrode active material is obtained. Specifically, the volume of a sphere having a radius equal to half of the primary particle diameter is the volume of the primary particle, and then the particle diameter at the point where 50% of the volume cumulative distribution according to the particle diameter in the result of calculating the volume of the primary particle is calculated, thereby measuring.

[0076] The above equation 1 is the average particle diameter (D) of the primary particles measured through SEM image analysis with the size of the crystal grains (D) measured through EBSD analysis. 50 ), the size of the crystal grains (D) is divided into the average particle diameter of the primary particles (D 50 ) is closer to the single crystallinity. That is, the maximum value of the single crystallinity is 1, which means that one primary particle is composed of one crystal grain.

[0077] The above positive electrode active material has a single crystallinity (χ) of 0.500 or more and 0.850 or less according to Equation 1 described herein. The single crystallinity (χ) is 0.500 or more, 0.510 or more, 0.520 or more, 0.530 or more, 0.540 or more, 0.550 or more, 0.560 or more, 0.570 or more, 0.580 or more, 0.590 or more, 0.60 or more, 0.610 or more, 0.620 or more, 0.630 or more, 0.640 or more, 0.650 or more, 0.660 or more, 0.670 or more, 0.680 or more, 0.690 or more, 0.700 or more, 0.710 or more, 0.720 or more, 0.730 or more, 0.740 or more, 0.750 or more, 0.760 or more, 0.770 or more, 0.780 or more, It may be 0.790 or more, 0.800 or more, 0.810 or more, or 0.820 or more, and 0.830 or less, 0.840 or less, or 0.850 or less. In particular, when the single crystallinity (χ) is 0.800 or more and 0.850 or less, it means that the lithium composite transition metal oxide has two or more crystal grains, and the interfaces between the crystal grains, which serve as the migration paths of lithium ions inside the positive electrode active material particles, are controlled, thereby improving lithium mobility and improving the output characteristics, rate characteristics, and resistance characteristics of the secondary battery. On the other hand, when the single crystallinity is less than 0.500, there is a problem that the efficiency and resistance characteristics are inferior because the interfaces between the crystal grains, which serve as the migration paths of lithium ions inside the lithium composite transition metal oxide particles, are excessive. Specifically, in the case of secondary particles that are not single particles, the single crystallinity is less than 0.500. When the degree of single crystallinity exceeds 0.850, the interface between crystal grains, which serves as a migration path for lithium ions within the lithium composite transition metal oxide particles, is small, so lithium mobility is reduced, and there is a problem that the output characteristics, rate characteristics, and resistance characteristics of the secondary battery are inferior.

[0078] According to the present invention, the size (D) of the crystal grains is 2.00 ㎛ or more and 5.00 ㎛ or less. Specifically, the size (D) of the crystal grains may be 2.00 ㎛ or more, 2.10 ㎛ or more, 2.20 ㎛ or more, 2.30 ㎛ or more, 2.40 ㎛ or more, or 2.50 ㎛ or more, and 2.60 ㎛ or less, 2.70 ㎛ or less, 2.80 ㎛ or less, 2.90 ㎛ or less, 3.00 ㎛ or less, 3.10 ㎛ or less, 3.20 ㎛ or less, 3.30 ㎛ or less, 3.40 ㎛ or less, 3.50 ㎛ or less, 3.60 ㎛ or less, 3.70 ㎛ or less, 3.80 ㎛ or less, 3.90 ㎛ or less, 4.00 ㎛ or less, 4.10 ㎛ or less, 4.20 ㎛ or less, 4.30 ㎛ or less, 4.40 ㎛ or less, 4.50 ㎛ or less, 4.60 ㎛ or less, 4.70 ㎛ or less, It may be 4.80㎛ or less, 4.90㎛ or less, or 5.00㎛ or less. When the size (D) of the crystal grains is within the above range, since the interfaces between the crystal grains, which serve as the migration paths of lithium ions within the positive electrode active material particles, exist to an appropriate degree, the lithium mobility is improved, and the output characteristics, rate characteristics, and resistance characteristics of the secondary battery can be improved. When the size (D) of the crystal grains is less than 2.00㎛ or more than 5.00㎛, there is a problem that the lithium mobility is reduced because the interfaces between the crystal grains, which serve as the migration paths of lithium ions within the positive electrode active material particles, are too many or too few, and thus the output characteristics, rate characteristics, and resistance characteristics of the secondary battery are deteriorated. In addition, in order to manufacture a positive electrode active material having a crystal grain size (D) of more than 5.00㎛, it is necessary to sinter at a high temperature exceeding 1000℃, so it is practically difficult to manufacture a positive electrode active material having a crystal grain size (D) of more than 5.00㎛.

[0079]

[0080] According to one embodiment of the present invention, the lithium composite transition metal oxide may have a composition represented by the following chemical formula 1.

[0081] [Chemical Formula 1]

[0082] Li 1+x Ni a Co b Mn c M 1 d O2

[0083] In the above chemical formula 1,

[0084] Above M 1 Silver is at least one selected from Al, W, Co, B, Zr, Y, Ce, Hf, La, Ba, F, P, S, Nb, Ta, Sc, Cr, V, Cu, Sr, Ti, Mg, Mo, Sn, Fe, Zn and Si, -0.10≤x≤0.10, 0.500≤a<1.000, 0 <b<0.500, 0<c<0.500, 0≤d≤0.100, a+b+c+d=1이다.

[0085] Above M 1 is a doping element, specifically the above M 1 is at least one selected from Al, W, Co, B, Zr, Y, Ce, Hf, La, Ba, F, P, S, Nb, Ta, Sc, Cr, V, Cu, Sr, Ti, Mg, Mo, Sn, Fe, Zn and Si. The above M 1 Although not essential, it can improve capacity characteristics and life characteristics. In particular, M 1 In the case of Zr and Y, it acts as a flux during firing and can improve resistance characteristics and life characteristics.

[0086] The above x may be -0.10 or more, -0.09 or more, -0.08 or more, -0.07 or more, -0.06 or more, -0.05 or more, -0.04 or more, -0.03 or more, -0.02 or more, -0.01 or more, 0 or more, 0.01 or more, 0.02 or more, 0.03 or more, 0.04 or more, or 0.05 or more, and may be 0.06 or less, 0.07 or less, 0.08 or less, 0.09 or less, or 0.10 or less. When x satisfies the above range, high safety and high energy density per unit volume can be realized.

[0087] The above a is the molar ratio of nickel (Ni) among the total metals excluding lithium in the lithium composite transition metal oxide, and may be 0.500 or more, 0.510 or more, 0.520 or more, 0.530 or more, 0.540 or more, 0.550 or more, 0.560 or more, 0.570 or more, 0.580 or more, 0.590 or more, 0.600 or more, or 0.610 or more, and 0.620 or less, 0.630 or less, 0.640 or less, 0.650 or less, 0.660 or less, 0.670 or less, 0.680 or less, 0.690 or less, 0.700 or less, 0.710 or less, 0.720 or less, 0.730 or less, 0.740 or less, 0.750 or less, 0.760 or less, 0.770 or less, 0.780 or less, 0.790 or less, 0.800 or less, 0.810 or less, 0.820 or less, 0.830 or less, 0.840 or less, 0.850 or less, 0.860 or less, 0.870 or less, 0.880 or less, 0.890 or less, 0.900 or less, 0.910 or less, 0.920 or less, 0.930 or less, 0.940 or less, 0.950 or less, 0.960 or less, 0.970 or less, 0.980 or less, 0.990 or less, or less than 1.000. When a satisfies the above range, high energy characteristics can be realized, and in particular, when a is 0.600 or more and 0.700 or less, high energy density can be exhibited when driven at high voltage, so that high capacity characteristics can be realized and high safety can be realized.

[0088] The above b is the molar ratio of cobalt (Co) among all metals excluding lithium in the lithium composite transition metal oxide, and may be greater than 0, 0.010 or more, 0.020 or more, 0.030 or more, 0.040 or more, 0.050 or more, or 0.060 or more, and may be 0.070 or less, 0.080 or less, 0.090 or less, 0.100 or less, 0.110 or less, 0.120 or less, 0.130 or less, 0.140 or less, 0.150 or less, 0.160 or less, 0.170 or less, 0.180 or less, 0.190 or less, 0.200 or less, 0.210 or less, 0.220 or less, 0.230 or less, 0.240 or less, 0.250 or less, 0.260 or less. It may be 0.270 or less, 0.280 or less, 0.290 or less, 0.300 or less, 0.310 or less, 0.320 or less, 0.330 or less, 0.340 or less, 0.350 or less, 0.360 or less, 0.370 or less, 0.380 or less, 0.390 or less, 0.400 or less, 0.410 or less, 0.420 or less, 0.430 or less, 0.440 or less, 0.450 or less, 0.460 or less, 0.470 or less, 0.480 or less, 0.490 or less, or less than 0.500. When b satisfies the above range, stability can be improved during the charge and discharge process, and rate characteristics can be enhanced.

[0089] The above c is the molar ratio of manganese (Mn) among all metals excluding lithium in the lithium composite transition metal oxide, and is greater than 0, 0.010 or more, 0.020 or more, 0.030 or more, 0.040 or more, 0.050 or more, 0.060 or more, 0.070 or more, 0.080 or more, 0.090 or more, 0.100 or more, 0.110 or more, 0.120 or more, 0.130 or more, 0.140 or more, 0.150 or more, 0.160 or more, 0.170 or more, 0.180 or more, 0.190 or more, 0.200 or more, 0.210 or more, 0.220 or more, 0.230 or more, 0.240 or more, 0.250 or more, 0.260 or more, It may be 0.270 or more, 0.280 or more, 0.290 or more, 0.300 or more, or 0.310 or more, and may be 0.320 or less, 0.330 or less, 0.340 or less, 0.350 or less, 0.360 or less, 0.370 or less, 0.380 or less, 0.390 or less, 0.400 or less, 0.410 or less, 0.420 or less, 0.430 or less, 0.440 or less, 0.450 or less, 0.460 or less, 0.470 or less, 0.480 or less, 0.490 or less, or less than 0.500. When c satisfies the above range, high temperature stability may be increased, and side reactions with the electrolyte may be relatively reduced.

[0090] The above d is M among all metals except lithium in the lithium complex transition metal oxide. 1 The molar ratio of d may be 0 or more, or 0.010 or more, and may be 0.020 or less, 0.030 or less, 0.040 or less, 0.050 or less, 0.060 or less, 0.070 or less, 0.080 or less, 0.090 or less, or 0.100 or less. When d satisfies the above range, the stability of the crystal structure of the positive electrode active material may be improved and the particle shape may be improved.

[0091]

[0092] According to one embodiment of the present invention, the lithium composite transition metal oxide may include at least one doping element selected from Al, W, Co, B, Zr, Y, Ce, Hf, La, Ba, F, P, S, Nb, Ta, Sc, Cr, V, Cu, Sr, Ti, Mg, Mo, Sn, Fe, Zn and Si, i.e., may be doped with a doping element. In this case, the stability of the crystal structure of the positive electrode active material may be improved and the grain shape may be improved.

[0093]

[0094] According to one embodiment of the present invention, the average particle diameter (D) of the primary particles 50 ) may be 2.35㎛ or more and 6㎛ or less. Specifically, the average particle diameter (D) of the primary particles 50 ) may be 2.35㎛ or more, or 2.40㎛ or more, and 3.10㎛ or less, 3.20㎛ or less, 3.30㎛ or less, 3.40㎛ or less, 3.50㎛ or less, 3.60㎛ or less, 3.70㎛ or less, 3.80㎛ or less, 3.90㎛ or less, 4.00㎛ or less, 4.10㎛ or less, 4.20㎛ or less, 4.30㎛ or less, 4.40㎛ or less, 4.50㎛ or less, 4.60㎛ or less, 4.70㎛ or less, 4.80㎛ or less, 4.90㎛ or less, 5.00㎛ or less, 5.10㎛ or less, 5.20㎛ or less, 5.30㎛ or less, 5.40㎛ or less, 5.50㎛ or less, 5.60㎛ or less, 5.70㎛ or less, It may be 5.80㎛ or less, 5.90㎛ or less, or 6.00㎛ or less. The average particle diameter (D 50 ) is within the above range, excellent electrode density can be achieved and structural stability can be improved.

[0095]

[0096] Method for manufacturing positive electrode active material

[0097] Next, a method for manufacturing the positive electrode active material of the present invention will be described. The method for manufacturing the positive electrode active material of the present invention is a method for manufacturing the positive electrode active material according to the present invention.

[0098] The positive electrode active material according to the present invention can be manufactured through the following manufacturing method 1 or manufacturing method 2. Hereinafter, each of manufacturing method 1 and manufacturing method 2 will be described in detail.

[0099]

[0100] <Manufacturing Method 1>

[0101] Method 1 for producing a cathode active material according to the present invention comprises the steps of (A1) mixing a composite transition metal hydroxide and a lithium-containing raw material to produce a mixture; and (B1) calcining the mixture to produce a lithium composite transition metal oxide; and is performed under conditions satisfying the following formula 2.

[0102] [Formula 2]

[0103] 30.30≤(0.055×T1)-(20×P1)≤31.00

[0104] In the above equation 2, P1 is the molar ratio (Li / M) of lithium (Li) present in the lithium-containing raw material to the transition metal (M) present in the complex transition metal hydroxide of the (A1) stage, and T1 is the sintering temperature of the (B1) stage.

[0105] The positive electrode active material according to the present invention described above can be manufactured by appropriately controlling the type of raw material, sintering temperature, sintering atmosphere, etc.

[0106]

[0107] Hereinafter, each step of the present invention will be described in detail.

[0108]

[0109] (A1) Step

[0110] The method for manufacturing a positive electrode active material according to the present invention includes a step (A1) of manufacturing a mixture by mixing a composite transition metal hydroxide and a lithium-containing raw material.

[0111] The above complex transition metal hydroxide can be produced through a co-precipitation reaction by introducing a complex transition metal-containing solution, an ammonium cation complex forming agent, and a basic compound into a reactor.

[0112] The above complex transition metal-containing solution may contain nickel (Ni), cobalt (Co), and manganese (Mn).

[0113] The above-mentioned composite transition metal-containing solution can be prepared by dissolving a transition metal-containing raw material in a solvent such as water, and for example, can be prepared by dissolving a nickel (Ni)-containing raw material, a cobalt (Co)-containing raw material, and a manganese (Mn)-containing raw material in water. That is, the above-mentioned composite transition metal-containing solution can include a nickel (Ni)-containing raw material, a cobalt (Co)-containing raw material, and a manganese (Mn)-containing raw material. In addition, if necessary, the above-mentioned composite transition metal-containing solution can further include a metal-containing raw material containing a transition metal other than nickel (Ni), cobalt (Co), and manganese (Mn) (for example, at least one selected from Al, W, Co, B, Zr, Y, Ce, Hf, La, Ba, F, P, S, Nb, Ta, Sc, Cr, V, Cu, Sr, Ti, Mg, Mo, Sn, Fe, Zn, and Si).

[0114] The above nickel (Ni)-containing raw materials include nickel-containing acetate, nitrate, sulfate, halide, sulfide, hydroxide, oxide, oxyhydroxide, NiSO4, NiSO4ㆍ6H2O. It may be at least one selected from the group consisting of NiCO3ㆍ2Ni(OH)2ㆍ4H2O, NiC2O4ㆍ2H2O, Ni(NO3)2ㆍ6H2O, fatty acid nickel, and nickel halides, and a mixture of one or two or more of these may be used. Specifically, as a nickel (Ni)-containing raw material, NiSO4ㆍ6H2O may be used when considering the ease and economy of the manufacturing process, such as pH control and solubility.

[0115] The above cobalt (Co)-containing raw material may be at least one selected from the group consisting of cobalt-containing acetate, nitrate, sulfate, halide, sulfide, hydroxide, oxide, oxyhydroxide, Co(OCOCH3)2·4H2O, Co(NO3)2·6H2O, Co(SO4)2·7H2O, fatty acid cobalt, and cobalt halides, and a mixture of one or two or more of these may be used. Specifically, as the cobalt (Co)-containing raw material, Co(SO4)2·7H2O may be used when considering the ease and economy of the manufacturing process such as pH control and solubility.

[0116] The manganese (Mn)-containing raw material may be at least one selected from the group consisting of manganese-containing acetates, nitrates, sulfates, halides, sulfides, hydroxides, oxides, oxyhydroxides, MnSO4·H2O, MnCO3, manganese dicarboxylates, manganese citrates, manganese salts of fatty acid manganese, and halides of manganese chloride, and a mixture of one or two or more of these may be used. As the manganese (Mn)-containing raw material, MnSO4·H2O may be used when considering the ease and economy of the manufacturing process, such as pH control and solubility.

[0117] Nickel (Ni)-containing raw materials, cobalt (Co)-containing raw materials, and manganese (Mn)-containing raw materials can be used in appropriate amounts considering the content of each metal element in the composite transition metal hydroxide being manufactured.

[0118]

[0119] Meanwhile, the ammonium cation complex forming agent may include at least one compound selected from the group consisting of NH4OH, (NH4)2SO4, NH4NO3, NH4Cl, CH3COONH4, and NH4CO3, and may be introduced into the reactor in the form of a solution in which the compound is dissolved in a solvent. At this time, as the solvent, water or a mixture of water and an organic solvent (specifically, alcohol, etc.) that can be uniformly mixed with water may be used.

[0120]

[0121] The basic compound may be at least one compound selected from the group consisting of NaOH, KOH, and Ca(OH)2, and may be introduced into the reactor in the form of a solution in which the compound is dissolved in a solvent. At this time, the solvent may be water, or a mixture of water and an organic solvent (specifically, alcohol, etc.) that can be uniformly mixed with water.

[0122]

[0123] When a complex transition metal-containing solution, an ammonium cation complex forming agent, and a basic compound are introduced into a reactor as described above, precursor particles in the form of a complex transition metal hydroxide are generated due to a coprecipitation reaction between the transition metal ions in the complex transition metal-containing solution and the hydroxide ions of the basic compound.

[0124] The above coprecipitation reaction can be carried out for 12 hours or more and 100 hours or less. When the coprecipitation reaction is carried out for a time within the above range, particles having a uniform particle size and shape can be produced.

[0125] At this time, the basic compound can be added in an amount such that the pH of the reaction solution becomes within the desired range.

[0126] Once precursor particles are formed as described above, the particles are separated from the reaction solution to obtain a complex transition metal precursor. Specifically, the reaction solution is filtered to separate the complex transition metal precursor, and then the separated complex transition metal precursor is washed and dried to obtain the complex transition metal precursor. At this time, processes such as grinding and / or classification may also be performed, as needed.

[0127]

[0128] According to one embodiment of the present invention, the composite transition metal hydroxide may have a composition represented by the following chemical formula 2.

[0129] [Chemical Formula 2]

[0130] Ni a1 Co b1 Mn c1 M 2 d1 (OH)2

[0131] In the above chemical formula 2,

[0132] Above M 2 is at least one selected from Al, W, Co, B, Zr, Y, Ce, Hf, La, Ba, F, P, S, Nb, Ta, Sc, Cr, V, Cu, Sr, Ti, Mg, Mo, Sn, Fe, Zn and Si,

[0133] 0.50≤a1<1.00, 0 <b1<0.50, 0<c1<0.50, 0≤d1≤0.10, a1+b1+c1+d1=1이다.

[0134] Above M 2 is a doping element, specifically the above M 2 It may be at least one selected from Al, W, Co, B, Zr, Y, Ce, Hf, La, Ba, F, P, S, Nb, Ta, Sc, Cr, V, Cu, Sr, Ti, Mg, Mo, Sn, Fe, Zn and Si. The above M 2Although not necessarily included, if included in an appropriate amount, the particle shape of the positive electrode active material can be improved and the stability of the crystal structure can be enhanced.

[0135] The above a1 is the molar ratio of nickel (Ni) among the total metals excluding lithium in the lithium composite transition metal oxide, and may be 0.50 or more, 0.51 or more, 0.52 or more, 0.53 or more, 0.54 or more, 0.55 or more, 0.56 or more, 0.57 or more, 0.58 or more, 0.59 or more, 0.60 or more, or 0.61 or more, and may be 0.62 or less, 0.63 or less, 0.64 or less, 0.65 or less, 0.66 or less, 0.67 or less, 0.68 or less, 0.69 or less, 0.70 or less, 0.71 or less, 0.72 or less, 0.73 or less, 0.74 or less, 0.75 or less, 0.76 or less, 0.77 or less, 0.78 or less, 0.79 or less. It may be 0.80 or less, 0.81 or less, 0.82 or less, 0.83 or less, 0.84 or less, 0.85 or less, 0.86 or less, 0.87 or less, 0.88 or less, 0.89 or less, 0.9 or less, 0.91 or less, 0.92 or less, 0.93 or less, 0.94 or less, 0.95 or less, 0.96 or less, 0.97 or less, 0.98 or less, 0.99 or less, or less than 1.00. When a1 satisfies the above range, high energy characteristics can be implemented, and in particular, when a1 is 0.60 or more and 0.70 or less, high energy density is exhibited during high voltage operation, so high capacity characteristics can be implemented, and high safety can be implemented.

[0136] The above b1 is the molar ratio of cobalt (Co) among all metals excluding lithium in the lithium composite transition metal oxide, and may be greater than 0, 0.01 or more, 0.02 or more, 0.03 or more, 0.04 or more, 0.05 or more, or 0.06 or more, and may be 0.07 or less, 0.08 or less, 0.09 or less, 0.10 or less, 0.11 or less, 0.12 or less, 0.13 or less, 0.14 or less, 0.15 or less, 0.16 or less, 0.17 or less, 0.18 or less, 0.19 or less, 0.20 or less, 0.21 or less, 0.22 or less, 0.23 or less, 0.24 or less, 0.25 or less, 0.26 or less, 0.27 or less, 0.28 or less, 0.29 or less, It may be 0.30 or less, 0.31 or less, 0.32 or less, 0.33 or less, 0.34 or less, 0.35 or less, 0.36 or less, 0.37 or less, 0.38 or less, 0.39 or less, 0.40 or less, 0.41 or less, 0.42 or less, 0.43 or less, 0.44 or less, 0.45 or less, 0.46 or less, 0.47 or less, 0.48 or less, 0.49 or less, or less than 0.50. When b1 satisfies the above range, stability can be improved during the charge and discharge process, and rate characteristics can be enhanced.

[0137] The above c1 is the molar ratio of manganese (Mn) among all metals excluding lithium in the lithium composite transition metal oxide, greater than 0, 0.01 or more, 0.02 or more, 0.03 or more, 0.04 or more, 0.05 or more, 0.06 or more, 0.07 or more, 0.08 or more, 0.09 or more, 0.10 or more, 0.11 or more, 0.12 or more, 0.13 or more, 0.14 or more, 0.15 or more, 0.16 or more, 0.17 or more, 0.18 or more, 0.19 or more, 0.20 or more, 0.21 or more, 0.22 or more, 0.23 or more, 0.24 or more, 0.25 or more, 0.26 or more, 0.27 or more, 0.28 or more, 0.29 or more, 0.30 or more, or It can be 0.31 or more, 0.32 or less, 0.33 or less, 0.34 or less, 0.35 or less, 0.36 or less, 0.37 or less, 0.38 or less, 0.39 or less, 0.40 or less, 0.41 or less, 0.42 or less, 0.43 or less, 0.44 or less, 0.45 or less, 0.46 or less, 0.47 or less, 0.48 or less, 0.49 or less, or less than 0.50. When c1 satisfies the above range, high temperature stability can be increased, and side reactions with the electrolyte can be relatively reduced.

[0138] The above d1 is M among all metals except lithium in the lithium composite transition metal oxide. 1 The molar ratio of d1 may be 0 or more, or 0.01 or more, and may be 0.02 or less, 0.03 or less, 0.04 or less, 0.05 or less, 0.06 or less, 0.07 or less, 0.08 or less, 0.09 or less, or 0.10 or less. When d1 satisfies the above range, the stability of the crystal structure of the positive electrode active material may be improved and the particle shape may be improved.

[0139]

[0140] The above lithium (Li)-containing raw material may be at least one selected from the group consisting of LiOH, Li2CO3, LiNO3, LiNO2, LiOHㆍH2O, LiH, LiF, LiCl, LiBr, LiI, CH3COOLi, Li2O, Li acetate, Li dicarboxylic acid, Li citrate, Li fatty acid, alkyl lithium, and lithium halides, and a mixture of one or two or more thereof may be used. Specifically, when considering economic feasibility, Li2CO3 may be used as the lithium (Li)-containing raw material.

[0141]

[0142] The above mixing can be done by dry mixing or wet mixing. When mixing each component through dry mixing, the firing process can be performed without a separate drying process. When mixing each component through wet mixing, the mixture can be prepared by adding it to a solvent, specifically water, or a mixture of water and an organic solvent (specifically, alcohol, etc.) that can be uniformly mixed with water, or a solution containing each raw material, specifically an aqueous solution, is prepared, and then the mixed components are mixed and spray-dried before the firing process is performed. Each raw material and composite transition metal hydroxide can be used in an appropriate amount considering the content of each metal element in the lithium composite transition metal oxide to be finally manufactured.

[0143] According to one embodiment of the present invention, in the step (A1), the composite transition metal hydroxide and the lithium (Li)-containing raw material can be mixed in an amount such that the raw material has a composition represented by the chemical formula 1.

[0144]

[0145] According to one embodiment of the present invention, the composite transition metal hydroxide and the lithium-containing raw material may be mixed so that the molar ratio (Li / M) of lithium (Li) present in the lithium-containing raw material to the transition metal (M) present in the composite transition metal hydroxide is 1.00 or more and 1.10 or less. Specifically, the molar ratio (Li / M) of lithium (Li) present in the lithium-containing raw material to the transition metal (M) present in the composite transition metal hydroxide may be 1.00 or more, 1.01 or more, 1.02 or more, 1.03 or more, 1.04 or more, 1.05 or more, or 1.06 or more, and 1.07 or less, 1.08 or less, 1.09 or less, or 1.10 or less. When the molar ratio (Li / M) of lithium (Li) present in the lithium-containing raw material to the transition metal (M) present in the above-mentioned complex transition metal hydroxide is mixed so as to be within the above range, the shape of the single particles can be controlled to improve the capacity characteristics, resistance characteristics, and rate characteristics. In particular, when the molar ratio (Li / M) is 1.02 or more and 1.07 or less, the lithium required for the reaction is sufficient while the amount of residual lithium after the reaction is small, so that the capacity characteristics, resistance characteristics, and rate characteristics of the secondary battery manufactured therefrom are improved.

[0146]

[0147] (B1) Step

[0148]

[0149] The method for manufacturing a positive electrode active material according to the present invention includes, after the step (A1), the step (B1) of calcining the mixture to manufacture a lithium composite transition metal oxide.

[0150] According to one embodiment of the present invention, the firing may be performed at a temperature of 700°C or higher and 1,000°C or lower. Specifically, the firing may be performed at a temperature of 700°C or higher, 710°C or higher, 720°C or higher, 730°C or higher, 740°C or higher, 750°C or higher, 760°C or higher, 770°C or higher, 780°C or higher, 790°C or higher, 800°C or higher, 810°C or higher, 820°C or higher, 830°C or higher, 840°C or higher, 850°C or higher, 860°C or higher, 870°C or higher, 880°C or higher, 890°C or higher, 900°C or higher, 910°C or higher, 920°C or higher, or 930°C or higher, and 940°C or lower, 950°C or lower, 960°C or lower, 970°C or lower, 980°C or lower, 990°C or lower, or 1,000°C or lower. When the above-mentioned firing temperature is within the above range, it is easy to control the particle size and specific surface area of ​​the positive electrode active material, and the capacity characteristics and resistance characteristics of the secondary battery to which it is applied can be improved.

[0151]

[0152] According to one embodiment of the present invention, the firing may be performed for 5 hours or more and 20 hours or less. Specifically, the firing may be performed for 5 hours or more, 6 hours or more, 7 hours or more, or 8 hours or more, and 9 hours or less, 10 hours or less, 11 hours or less, 12 hours or less, 13 hours or less, 14 hours or less, 15 hours or less, 16 hours or less, 17 hours or less, 18 hours or less, 19 hours or less, or 20 hours or less. When the firing time is within the above range, a positive electrode active material having a layered structure and excellent structural stability can be manufactured, and the particle size of the positive electrode active material can be grown to an appropriate degree. The firing may be performed while maintaining the firing temperature during the firing time.

[0153]

[0154] Method 1 for manufacturing a positive electrode active material according to the present invention is performed under conditions satisfying the following formula 2.

[0155] [Formula 2]

[0156] 30.3≤(0.055×T1)-(20×P1)≤31.0

[0157] In the above equation 2,

[0158] P1 is the molar ratio (Li / M) of lithium (Li) present in the lithium-containing raw material to the transition metal (M) present in the complex transition metal hydroxide of the (A1) stage, and T1 is the sintering temperature of the (B1) stage.

[0159] The present inventors have determined the average particle diameter (D) of the primary particles 50 ) and the sintering temperature, the average particle diameter of the primary particles (D 50 ) and the relationship between the molar ratio (Li / M) of lithium (Li) present in a lithium-containing raw material to the transition metal (M) present in a complex transition metal hydroxide and the relationship between the grain size (D) and the sintering temperature, thereby finding out a method for manufacturing a cathode active material with improved output characteristics, rate characteristics, and resistance characteristics. Specifically, the inventors found that when the sintering temperature increases by about 10°C, the average particle diameter (D) of the primary particles increases. 50 ) increases by 0.55 μm, and the average particle diameter (D) of the primary particles increases by about 0.01 for every increase in the molar ratio (Li / M) of lithium (Li) present in the lithium-containing raw material to the transition metal (M) present in the complex transition metal hydroxide. 50 ) increased by 0.2 μm and that the grain size (D) increased as the sintering temperature increased, and by using this, a method for manufacturing a positive electrode active material with improved output characteristics, rate characteristics, and resistance characteristics was completed.

[0160] The above equation 2, i.e., (0.055×T1)-(20×P1) (wherein P1 is the molar ratio (Li / M) of lithium (Li) present in the lithium-containing raw material to the transition metal (M) present in the complex transition metal hydroxide of the (A1) stage, T1 is the sintering temperature of the (B1) stage, and P and T are dimensionless numbers not including units.) may be 30.3 or less, or 31.0 or less. Specifically, it may be greater than 28.5, greater than 29, greater than 29.1, greater than 29.2, greater than 29.3, greater than 29.4, greater than 29.5, greater than 29.6, greater than 29.7, greater than 29.8, greater than 29.9, greater than 30.0, greater than 30.1, or greater than 30.2, and may be less than or equal to 30.3, less than or equal to 30.4, less than or equal to 30.5, less than or equal to 30.6, less than or equal to 30.7, less than or equal to 30.8, less than or equal to 30.9, or less than or equal to 31.0. When the above formula 2 satisfies the above range, it is a single particle form composed of 10 or less primary particles, and a positive electrode active material with improved lithium mobility can be manufactured by controlling the average particle diameter and crystal grain size of the primary particles. Meanwhile, when the value of the above formula 2 is less than 30.3, there is a problem that the lifespan characteristics are poor because the interface between the crystal grains that serve as the migration path of lithium ions inside the lithium composite transition metal oxide particles is excessive, and when the value of the formula 2 is more than 31.0, there is a problem that the lithium mobility is poor because the interface between the crystal grains that serve as the migration path of lithium ions inside the lithium composite transition metal oxide particles is small, and the output characteristics, rate characteristics, and resistance characteristics of the secondary battery are poor.

[0161]

[0162] <Manufacturing Method 2>

[0163] Method 2 for producing a cathode active material according to the present invention comprises the steps of (A2) mixing a composite transition metal hydroxide and a lithium (Li)-containing raw material to produce a mixture; (B2) firing the mixture to produce a fired product; and (C2) heat-treating the fired product at a temperature of 400°C or higher and 900°C or lower to produce a lithium composite transition metal oxide; and is performed under conditions satisfying the following formula 3.

[0164] [Formula 3]

[0165] 26.0≤(0.055×T2)-(20×P2)≤31.5

[0166] In the above equation 3, P2 is the molar ratio (Li / M) of lithium (Li) present in the lithium-containing raw material to the transition metal (M) present in the complex transition metal hydroxide of the (A2) stage, and T2 is the sintering temperature of the (B2) stage.

[0167] The positive electrode active material according to the present invention described above can be manufactured by appropriately controlling the type of raw material, sintering temperature, sintering atmosphere, etc.

[0168]

[0169] (A2) Step

[0170] The method for manufacturing a positive electrode active material according to the present invention includes a step (A2) of manufacturing a mixture by mixing a composite transition metal hydroxide and a lithium-containing raw material.

[0171] Step (A2) can be performed in the same manner as step (A1) of the positive electrode active material manufacturing method 1, and since step (A1) of the positive electrode active material manufacturing method 1 has been described above, a detailed description thereof will be omitted.

[0172]

[0173] (B2) Step

[0174] The method for manufacturing a positive electrode active material according to the present invention includes, after the step (A2), the step (B2) of manufacturing a sintered product by firing the mixture.

[0175]

[0176] According to one embodiment of the present invention, the firing may be performed at a temperature of 700°C or higher and 1,000°C or lower. Specifically, the firing may be performed at a temperature of 700°C or higher, 710°C or higher, 720°C or higher, 730°C or higher, 740°C or higher, 750°C or higher, 760°C or higher, 770°C or higher, 780°C or higher, 790°C or higher, 800°C or higher, 810°C or higher, 820°C or higher, 830°C or higher, 840°C or higher, 850°C or higher, 860°C or higher, 870°C or higher, 880°C or higher, 890°C or higher, 900°C or higher, 910°C or higher, 920°C or higher, or 930°C or higher, and 940°C or lower, 950°C or lower, 960°C or lower, 970°C or lower, 980°C or lower, 990°C or lower, or 1,000°C or lower. When the above-mentioned firing temperature is within the above range, it is easy to control the particle size and specific surface area of ​​the positive electrode active material, and the capacity characteristics and resistance characteristics of the secondary battery to which it is applied can be improved.

[0177]

[0178] According to one embodiment of the present invention, the firing may be performed for 5 hours or more and 20 hours or less. Specifically, the firing may be performed for 5 hours or more, 6 hours or more, 7 hours or more, or 8 hours or more, 9 hours or more, 10 hours or more, 11 hours or more, 12 hours or more, 13 hours or more, or 14 hours or more, and 15 hours or less, 16 hours or less, 17 hours or less, 18 hours or less, 19 hours or less, or 20 hours or less. When the firing time is within the above range, a positive electrode active material having a layered structure and excellent structural stability can be manufactured. In particular, when the firing time is 14 hours or more and 20 hours or less, the particle size of the positive electrode active material can be grown to an appropriate degree.

[0179]

[0180] (C2) Step

[0181] The method for manufacturing a positive electrode active material according to the present invention includes, after the step (B2), the step (C2) of heat-treating the sintered product at a temperature of 400°C or higher and 900°C or lower.

[0182] By including the above step (C2), the crystal grain size can be reduced. Accordingly, the lithium mobility of the positive electrode active material is improved, and the output characteristics, rate characteristics, and resistance characteristics of the secondary battery to which it is applied can be improved. The heat treatment is a step distinct from the step (B2), and the temperature of the heat treatment can be 50°C or more lower than the sintering temperature. Specifically, the heat treatment can be performed at a temperature of 400°C or higher, 500°C or higher, 600°C or higher, or 700°C or higher, and 800°C or lower, or 900°C or lower. When the heat treatment is performed within the above temperature range, the surface crystals are stabilized, and the interface between the crystal grains increases due to the reduction in the crystal grain size, thereby improving the lithium mobility, and the output characteristics, rate characteristics, and resistance characteristics of the secondary battery to which it is applied can be improved. If the above heat treatment is at 400°C or lower, the heat energy required for stabilizing the surface crystals is insufficient, so the surface crystals are not sufficiently stabilized. If the above heat treatment is at 900°C or higher, there is a problem in that the crystal grain size does not decrease.

[0183]

[0184] According to one embodiment of the present invention, the heat treatment may be performed for 2 hours or more and 10 hours or less. Specifically, the heat treatment may be performed for 2 hours or more, 3 hours or more, or 4 hours or more, and 5 hours or less, 6 hours or less, 7 hours or less, 8 hours or less, 9 hours or less, or 10 hours or less. When the time is within the above range, the surface crystals are stabilized, the interface between crystal grains increases due to a decrease in the crystal grain size, thereby improving lithium mobility, and the output characteristics, rate characteristics, and resistance characteristics of a secondary battery to which this is applied may be improved.

[0185]

[0186] Method 2 for manufacturing a positive electrode active material according to the present invention is performed under conditions satisfying the following formula 3.

[0187] [Formula 3]

[0188] 26.0≤(0.055×T2)-(20×P2)≤31.5

[0189] In the above equation 3,

[0190] P2 is the molar ratio (Li / M) of lithium (Li) present in the lithium-containing raw material to the transition metal (M) present in the complex transition metal hydroxide of the (A2) stage, and T2 is the sintering temperature of the (B2) stage.

[0191] The above equation 3, i.e., (0.055×T2)-(20×P2) (wherein P2 is the molar ratio (Li / M) of lithium (Li) present in the lithium-containing raw material to the transition metal (M) present in the complex transition metal hydroxide of the (A2) stage, T2 is the sintering temperature of the (B2) stage, and P and T are dimensionless numbers not including units.) may be 26.0 or more and 31.5 or less. Specifically, it may be 26.0 or greater, 26.5 or greater, 27.0 or greater, 27.5 or greater, 28.0 or greater, 28.5 or greater, 29.0 or greater, 29.1 or greater, 29.2 or greater, 29.3 or greater, 29.4 or greater, 29.5 or greater, 29.6 or greater, 29.7 or greater, 29.8 or greater, 29.9 or greater, 30.0 or greater, 30.1 or greater, 30.2 or greater, 30.3 or greater, 30.4 or greater, 30.5 or greater, 30.6 or greater, 30.7 or greater, 30.8 or greater, 30.9 or greater, or 31.0 or greater, 31.1 or less, 31.2 or less, 31.3 or less, 31.4 or less, or 31.5 or less. When the above formula 3 satisfies the above range, it is a single particle form composed of 10 or fewer primary particles, and a cathode active material with improved lithium mobility can be manufactured by controlling the average particle diameter of the primary particles and the size of the crystal grains. On the other hand, when the above (C2) step is not included and the formula 3 is less than 26.0, there is a problem that the lifespan characteristics are inferior because the interfaces between the crystal grains that serve as the migration paths of lithium ions inside the lithium composite transition metal oxide particles are excessive, and when the formula 3 exceeds 31.5, there is a problem that the lithium mobility is inferior because the interfaces between the crystal grains that serve as the migration paths of lithium ions inside the lithium composite transition metal oxide particles are small, and the output characteristics, rate characteristics, and resistance characteristics of the secondary battery are inferior.

[0192]

[0193] anode

[0194] Next, the anode according to the present invention will be described.

[0195] The positive electrode according to the present invention comprises a positive electrode active material layer comprising the positive electrode active material according to the present invention. Specifically, the positive electrode comprises a positive electrode current collector and a positive electrode active material layer formed on the positive electrode current collector, and comprising the positive electrode active material. Since the positive electrode active material has been described above, a detailed description thereof will be omitted, and only the remaining components will be described in detail below.

[0196]

[0197] The positive electrode current collector is not particularly limited as long as it is conductive and does not cause a chemical change in the battery, and for example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, etc. may be used. In addition, the positive electrode current collector may typically have a thickness of 3 µm to 500 µm, and fine unevenness may be formed on the surface of the positive electrode current collector to increase the adhesive strength of the positive electrode active material. For example, the positive electrode current collector may be used in various forms such as a film, sheet, foil, net, porous body, foam, or non-woven fabric.

[0198]

[0199] The above-mentioned positive electrode active material layer may include a conductive material and a binder together with the positive electrode active material. At this time, 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.

[0200]

[0201] 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, summer black, and carbon fiber; metal powder or metal fiber such as copper, nickel, aluminum, and silver; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives, and the like. One type alone or a mixture of two or more types of these 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.

[0202]

[0203] The above binder serves to improve the adhesion between positive electrode active material particles and the adhesive strength between the positive electrode active material and the current collector. Specific examples include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene butadiene rubber (SBR), fluoroelastomer, or various copolymers thereof, and one of these may be used alone or a mixture of two or more thereof. The 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.

[0204]

[0205] 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 coating 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 and a conductive material in a solvent, on a positive electrode current collector, followed by drying and rolling. At this time, the types and contents of the positive electrode active material, binder, and conductive material are as described above. Alternatively, the positive electrode can be manufactured by casting the composition for forming a positive electrode active material layer on a separate support, and then laminating the film obtained by peeling it from the support on a positive electrode current collector.

[0206]

[0207] The solvent may be a solvent generally used in the relevant technical field, such as dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, or water. One of these may be used alone or a mixture of two or more thereof may be used. The amount of the solvent used is sufficient to dissolve or disperse the positive electrode active material, conductive material, and binder, taking into account the coating thickness and manufacturing yield of the slurry, and to have a viscosity that can exhibit excellent thickness uniformity when applied thereafter for manufacturing the positive electrode.

[0208]

[0209] lithium secondary battery

[0210] Next, a lithium secondary battery according to the present invention will be described.

[0211]

[0212] The present invention can manufacture an electrochemical device including the above-described positive electrode. The electrochemical device may be, specifically, a battery, a capacitor, or the like, and more specifically, a lithium secondary battery.

[0213]

[0214] The lithium secondary battery specifically includes a positive electrode, a negative electrode positioned opposite the positive electrode, and a separator and electrolyte interposed between the positive electrode and the negative electrode. Since the positive electrode is the same as described above, a detailed description thereof will be omitted, and only the remaining components will be described in detail below.

[0215]

[0216] In addition, the lithium secondary battery may optionally further include a battery container that houses the electrode assembly of the positive electrode, the negative electrode, and the separator, and a sealing member that seals the battery container.

[0217]

[0218] In the above lithium secondary battery, the negative electrode includes a negative electrode current collector and a negative electrode active material layer positioned on the negative electrode current collector.

[0219] 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.

[0220]

[0221] The above negative electrode active material layer optionally includes a binder and a conductive material together with the negative electrode active material.

[0222]

[0223] 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 fiber-like forms, Kish graphite, pyrolytic carbon, mesophase pitch-based carbon fiber, meso-carbon microbeads, mesophase pitches, and high-temperature calcined carbon such as petroleum or coal tar pitch derived cokes.

[0224] The above negative electrode active material may be included in an amount of 80% to 99% by weight based on the total weight of the negative electrode active material layer.

[0225]

[0226] The above binder is a component that assists in bonding between the conductive material, the active material, and the current collector, and can typically be added in an amount of 0.1 wt% to 10 wt% based on the total weight of the negative electrode active material layer. Examples of such binders include polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene-butadiene rubber, nitrile-butadiene rubber, fluororubber, and various copolymers thereof.

[0227]

[0228] The conductive agent is a component for further improving the conductivity of the negative electrode active material, and may be added in an amount of 10 wt% or less, specifically, 5 wt% or less, based on the total weight of the negative electrode active material layer. The conductive agent is not particularly limited as long as it has conductivity and does not cause a chemical change in the battery, and examples thereof include graphite such as natural graphite or artificial graphite; carbon black such as acetylene black, Ketjen black, channel black, furnace black, lamp black, and thermal black; conductive fibers such as carbon fiber or metal fiber; metal powders such as fluorocarbon, aluminum, and 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.

[0229]

[0230] The negative electrode active material layer may be manufactured by applying and drying a composition for forming a negative electrode active material layer prepared by dissolving or dispersing a negative electrode active material, and optionally a binder and a conductive material in a solvent, on a negative electrode current collector, or by casting the composition for forming a negative electrode active material layer on a separate support, and then laminating the film obtained by peeling it off from the support on a negative electrode current collector.

[0231]

[0232] Meanwhile, in the lithium secondary battery, the separator separates the negative electrode and the positive electrode and provides a passage for lithium ions to move. Any separator commonly used in lithium secondary batteries can be used without special restrictions, and in particular, one having low resistance to ion movement of the electrolyte and excellent electrolyte moisture absorption capacity is preferable. Specifically, a porous polymer film, for example, a porous polymer film made of a polyolefin polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, and an ethylene / methacrylate copolymer, or a laminated structure of two or more layers thereof, can 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. can also be used. In addition, a coated separator containing a ceramic component or a polymer material to secure heat resistance or mechanical strength can be used, and can optionally be used in a single-layer or multi-layer structure.

[0233]

[0234] In addition, examples of the electrolyte used in the present invention include, but are not limited to, organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel-type polymer electrolytes, solid inorganic electrolytes, and molten inorganic electrolytes that can be used in the manufacture of lithium secondary batteries.

[0235] Specifically, the electrolyte may include an organic solvent and a lithium salt.

[0236] 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), ethylene carbonate (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.In this case, the performance of the electrolyte may be improved when the cyclic carbonate and the chain carbonate are mixed and used in a volume ratio of about 1:1 to about 1:9.

[0237]

[0238] The lithium salt may be used without any particular limitation as long as it is a compound capable of providing lithium ions used in a lithium secondary battery. Specifically, the lithium salt may be LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAl04, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2. LiCl, LiI, or LiB(C2O4)2. The concentration of the lithium salt is preferably used within the range of 0.1 to 5.0 M, specifically, 0.1 to 3.0 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.

[0239]

[0240] 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 additive may be included in an amount of 0.1 to 10 wt%, specifically, 0.1 to 5 wt%, based on the total weight of the electrolyte.

[0241]

[0242] As described above, a lithium secondary battery including a cathode active material according to the present invention exhibits excellent energy density, efficiency characteristics, resistance characteristics, and rate 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).

[0243] Accordingly, according to another embodiment of the present invention, a battery module including the lithium secondary battery as a unit cell and a battery pack including the same are provided.

[0244] 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.

[0245] 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.

[0246] 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.

[0247]

[0248] 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.

[0249]

[0250] Examples and Comparative Examples

[0251] Example 1

[0252] Ni 0.62 Co 0.06 Mn 0.32 A mixture was prepared by mixing a complex transition metal hydroxide (product name: Nickel cobalt manganese hydroxide, average particle size: 3-4 μm, secondary particles) having a composition represented by (OH)2, Li2CO3, (Ni+Co+Mn):Li in a molar ratio of 1:1.07, and mixing ZrO2 and Y2O3. At this time, ZrO2 is the Ni 0.62 Co 0.06 Mn 0.32 (OH)2 is mixed so that Zr has a content of 1,500 ppm with respect to the total weight, and Y2O3 is Ni 0.62 Co 0.06 Mn 0.32 (OH)2 was mixed so that Y content was 3,000 ppm based on the total weight.

[0253] The above mixture was calcined at a temperature of 940°C in an air atmosphere for 9 hours to produce a lithium composite transition metal oxide (positive electrode active material).

[0254]

[0255] Example 2

[0256] Ni 0.62 Co 0.06 Mn 0.32 A mixture was prepared by mixing a complex transition metal hydroxide (product name: Nickel cobalt manganese hydroxide, average particle size: 3-4 μm, secondary particles) with a composition represented by (OH)2, Li2CO3, (Ni+Co+Mn):Li in a molar ratio of 1:1.06, and mixing ZrO2 and Y2O3. At this time, ZrO2 is the Ni 0.62 Co 0.06 Mn 0.32 (OH)2 is mixed so that Zr has a content of 1,500 ppm with respect to the total weight, and Y2O3 is Ni 0.62 Co0.06 Mn 0.32 (OH)2 was mixed so that Y content was 3,000 ppm based on the total weight.

[0257] The above mixture was fired in an air atmosphere at a temperature of 950°C for 14 hours to produce a fired product, and then the fired product was heat-treated in an air atmosphere at a temperature of 800°C for 4 hours to produce a lithium composite transition metal oxide (positive electrode active material).

[0258]

[0259] Comparative Example 1

[0260] Ni 0.62 Co 0.06 Mn 0.32 A mixture was prepared by mixing a complex transition metal hydroxide (product name: Nickel cobalt manganese hydroxide, average particle size: 3-4 μm, secondary particles) with a composition represented by (OH)2, Li2CO3, (Ni+Co+Mn):Li in a molar ratio of 1:1.06, and mixing ZrO2 and Y2O3. At this time, ZrO2 is the Ni 0.62 Co 0.06 Mn 0.32 (OH)2 is mixed so that Zr has a content of 1,500 ppm with respect to the total weight, and Y2O3 is Ni 0.62 Co 0.06 Mn 0.32 (OH)2 was mixed so that Y content was 3,000 ppm based on the total weight.

[0261] The above mixture was calcined at a temperature of 950°C in an air atmosphere for 9 hours to produce a lithium composite transition metal oxide (positive electrode active material).

[0262]

[0263] Comparative Example 2

[0264] Ni 0.62 Co 0.06 Mn 0.32A mixture was prepared by mixing a complex transition metal hydroxide (product name: Nickel cobalt manganese hydroxide, average particle size: 3-4 μm, secondary particles) having a composition represented by (OH)2, Li2CO3, (Ni+Co+Mn):Li in a molar ratio of 1:1.04, and mixing ZrO2 and Y2O3. At this time, ZrO2 is the Ni 0.62 Co 0.06 Mn 0.32 (OH)2 is mixed so that Zr has a content of 1,500 ppm with respect to the total weight, and Y2O3 is Ni 0.62 Co 0.06 Mn 0.32 (OH)2 was mixed so that Y content was 3,000 ppm based on the total weight.

[0265] The above mixture was calcined at a temperature of 960°C in an air atmosphere for 9 hours to produce a lithium composite transition metal oxide (positive electrode active material).

[0266]

[0267] Comparative Example 3

[0268] The sintered product of Example 2 was used as the positive electrode active material of Comparative Example 3.

[0269]

[0270] Comparative Example 4

[0271] Ni 0.62 Co 0.06 Mn 0.32 A mixture was prepared by mixing a complex transition metal hydroxide (product name: Nickel cobalt manganese hydroxide, average particle size: 3-4 μm, secondary particles) with a composition represented by (OH)2, Li2CO3, (Ni+Co+Mn):Li in a molar ratio of 1:1.06, and mixing ZrO2 and Y2O3. At this time, ZrO2 is the Ni 0.62 Co 0.06 Mn 0.32 (OH)2 is mixed so that Zr has a content of 1,500 ppm with respect to the total weight, and Y2O3 is Ni 0.62 Co0.06 Mn 0.32 (OH)2 was mixed so that Y content was 3,000 ppm based on the total weight.

[0272] The above mixture was calcined in an air atmosphere at a temperature of 909°C for 9 hours to produce a lithium composite transition metal oxide (positive electrode active material).

[0273]

[0274] Temperature (℃) Li / M (C2) Whether step is performed (0.055 × temperature) - (20 × Li / M) Example 19401.07 X 30.30 Example 29501.06 ○ 31.05 Comparative Example 19501.06 X 31.05 Comparative Example 29601.04 X 32.00 Comparative Example 39501.06 X 31.05 Comparative Example 49091.06 X 28.80

[0275] Experimental example

[0276] Experimental Example 1: ICP Analysis

[0277] Each of the positive electrode active materials manufactured in Examples 1 to 2 and Comparative Examples 1 to 4 was taken in an amount of 0.1 g, 1 ml of hydrochloric acid was added, and heated to dissolve the positive electrode active material. After that, a small amount of hydrogen peroxide was added to promote the reaction, and the positive electrode active material was completely dissolved to prepare a solution. Then, the solution was diluted with deionized water so that the total volume of the solution became 10 ml, and an analysis sample was prepared. Using an ICP device (ICP-OES; Agilent 5100, Agilent Technologies Co., Ltd.), the weight ratio of the constituent elements present in the analysis sample was measured, and the composition of the positive electrode active material, M 1 The content (ppm) is shown in Table 2 below.

[0278] Composition Zr content (ppm) Y content (ppm) Example 1 Li 1.07 Ni 0.619 Co 0.060 Mn 0.317 Zr 0.001 Y 0.003 O21,3702,710 Example 2Li 1.06 Ni 0.619 Co0.060 Mn 0.317 Zr 0.001 Y 0.003 O21,3502,690Comparative example 1Li 1.06 Ni 0.620 Co 0.060 Mn 0.316 Zr 0.001 Y 0.003 O21,3502,730 Comparative Example 2Li 1.04 Ni 0.625 Co 0.050 Mn 0.321 Zr 0.001 Y 0.003 O21,3402,740Comparative example 3Li 1.07 Ni 0.619 Co 0.060 Mn 0.317 Zr 0.001 Y 0.003 O21,3602,680 Comparative Example 4Li 1.07 Ni 0.619 Co 0.060 Mn 0.317 Zr 0.001 Y 0.003 O21,3502,700

[0279] Through the above Table 2, it was confirmed that the lithium composite transition metal oxides manufactured in Examples 1 and 2 had a composition represented by the above chemical formula 1 and included doping elements Zr and Y.

[0280] Experimental Example 2: Single Crystallinity Analysis

[0281] - Measurement of average particle diameter of primary particles

[0282] Using SEM (FEI, Inspect F), SEM images (5K magnification) of the positive electrode active materials manufactured in Examples 1 to 2 and Comparative Examples 1 to 4 were obtained, and using an image processing program (LG Chemical, DX program), the boundaries of the primary particles present in the SEM images were divided and images were displayed in random colors, and the images are shown in Figures 1 to 6 below. Using the images in which the boundaries of the primary particles were divided and displayed in random colors, the area of ​​each primary particle was calculated through the number of pixels corresponding to each of n primary particles (an average of 50,000 or more primary particles), and the average particle diameter (D) of the primary particles present in the positive electrode active materials manufactured in Examples 1 and 2 and Comparative Examples 1 to 4 was calculated using the radius of a circle having the same area as the area of ​​each primary particle. 50 ) were measured and shown in Table 3 below.

[0283] Figure 1 is a SEM image of the positive electrode active material manufactured in Example 1.

[0284] Figure 2 is a SEM image of the positive electrode active material manufactured in Example 2.

[0285] Figure 3 is an SEM image of the positive electrode active material manufactured in Comparative Example 1.

[0286] Figure 4 is an SEM image of the positive electrode active material manufactured in Comparative Example 2.

[0287] Figure 5 is an SEM image of the positive electrode active material manufactured in Comparative Example 3.

[0288] Figure 6 is an SEM image of the positive electrode active material manufactured in Comparative Example 4.

[0289]

[0290] - Measurement of grain size (D)

[0291] For each of the positive electrode active materials manufactured in Examples 1 and 2 and Comparative Examples 1 to 4, 95 wt% of the positive electrode active material, 2.0 wt% of carbon black as a conductive material, and 3.0 wt% of polyvinylidene fluoride (PVDF) as a binder were mixed in an N-methylpyrrolidone (NMP) solvent to prepare a positive electrode slurry. The prepared positive electrode slurry was applied to one surface of an aluminum current collector and then dried at 130°C to prepare a positive electrode for EBSD analysis. Rolling was not performed during the manufacture of the positive electrode.

[0292] Using an ion milling device (HITACHI IM-400, accelerating voltage 6 kV), the anode was cut into cross-sections, and using an FE-SEM (FEI, QuantaFEG 250) equipped with a backscatter electron diffraction pattern analyzer (EBSD), the anode cross-section was subjected to EBSD analysis to obtain an IPF map, and the IPF maps are shown in FIGS. 7 to 12 below.

[0293] EBSD analysis was performed at an acceleration voltage of 20 kV and a WD of 16 mm on a scale with a grain size exceeding approximately 0.5 μm.

[0294] After calculating the grain size by the area of ​​the grains confirmed in the IPF map image, the arithmetic mean of these values ​​was obtained, and the measured grain size (D) is shown in Table 3 below.

[0295] And, the average particle diameter of the primary particles (D 50 ) and the crystal grain size (D) are substituted into Equation 1 described in this specification, and the single crystallinity (χ) is calculated as shown in Table 3 below.

[0296] Figure 7 is an IPF map obtained by EBSD analysis of a positive electrode for EBSD analysis manufactured using the positive electrode active material manufactured in Example 1.

[0297] Figure 8 is an IPF map obtained by EBSD analysis of a positive electrode for EBSD analysis manufactured using the positive electrode active material manufactured in Example 2.

[0298] Figure 9 is an IPF map obtained by EBSD analysis of a positive electrode for EBSD analysis manufactured using the positive electrode active material manufactured in Comparative Example 1.

[0299] Figure 10 is an IPF map obtained by EBSD analysis of a positive electrode for EBSD analysis manufactured using the positive electrode active material manufactured in Comparative Example 2.

[0300] Figure 11 is an IPF map obtained by EBSD analysis of a positive electrode for EBSD analysis manufactured using the positive electrode active material manufactured in Comparative Example 3.

[0301] Figure 12 is an IPF map obtained by EBSD analysis of a positive electrode for EBSD analysis manufactured using the positive electrode active material manufactured in Comparative Example 4.

[0302]

[0303] Particle size (㎛) Single crystallinity (D / D) 50 )1st particle (D 50 ) Grain size (D) Example 13.07 2.56 0.834 Example 22.45 2.02 0.824 Comparative example 13.08 2.85 0.925 Comparative example 23.04 2.95 0.970 Comparative example 32.47 2.30 0.931 Comparative example 41.50 1.04 0.693

[0304] Through Table 3, the positive electrode active materials manufactured in Examples 1 and 2 had an average particle diameter (D) of primary particles 50 ) was 2.35㎛ or more and 6.00㎛ or less, the grain size (D) was 2.00㎛ or more and 5.00㎛ or less, and the single crystallinity (χ) calculated by Equation 1 described in the present specification was 0.500 or more and 0.850 or less. On the other hand, it was confirmed that the positive electrode active materials manufactured in Comparative Examples 1 to 3 had a single crystallinity (χ) exceeding 0.850, and it was confirmed that the positive electrode active material manufactured in Comparative Example 4 had a single crystallinity (χ) of 0.500 or more and 0.850 or less, and the grain size (D) was less than 2.00㎛.

[0305]

[0306] Experimental Example 3: Rolling Density Measurement

[0307] Each 5g of the positive electrode active material of the examples and comparative examples was placed in a 2.2cm diameter, circular 4-Point Probe (Gold Pin) mold of a resistance measuring device (Hantech), and a force was applied until a force equivalent to 2,000kgf was reached. The height of the formed pellet (the difference between the height of the mold before the positive electrode active material was placed and the height of the mold after the force of 2,000kgf was applied) was measured. The rolling density (g / cm) was calculated from the height of the pellet. 3 ) was calculated and shown in Table 4 below.

[0308] [Formula 4]

[0309] Pellet volume (cm) 3 ) = π(radius of the circular pellet holder) 2 × Height of pellet

[0310] [Formula 5]

[0311] Rolling density (g / cm) 3 ) = Positive active material weight (g) / Pellet volume (cm 3 )

[0312] Rolled density (g / cm) 3 ) Example 12.93 Example 22.90 Comparative Example 12.91 Comparative Example 22.87 Comparative Example 32.88 Comparative Example 42.70

[0313] Through Table 4, it was confirmed that the positive electrode active materials manufactured in Examples 1 and 2 had a higher rolling density than the positive electrode active materials manufactured in Comparative Examples 2 to 4.

[0314] In particular, in the case of the positive electrode active material manufactured in Comparative Example 4, i.e., when the crystal grain size (D) is less than 2.00 ㎛, it was confirmed that the interface between the crystal grains, which serve as a path for lithium ions inside the positive electrode active material particles, was excessive, resulting in the lowest rolling density.

[0315]

[0316] Experimental Example 4: Battery Characteristics Evaluation

[0317] - Manufacturing of coin-type half-cells

[0318] A positive electrode slurry was prepared by mixing 95 wt% of the positive electrode active materials manufactured in Examples 1 and 2 and Comparative Examples 1 to 4, 2.0 wt% of carbon black as a conductive material, and 3.0 wt% of polyvinylidene fluoride (PVDF) as a binder in an N-methylpyrrolidone (NMP) solvent. The prepared positive electrode slurry was applied to one surface of an aluminum current collector, dried at 130°C, and then rolled to prepare a positive electrode.

[0319] An electrode assembly was manufactured using a lithium metal electrode as the negative electrode and a porous polyethylene separator interposed between the positive and negative electrodes. This was placed inside a battery case, and a coin-type half-cell was manufactured by injecting an electrolyte solution containing 1.0 M LiPF6 dissolved in an organic solvent containing ethylene carbonate (EC): ethyl methyl carbonate (EMC): diethyl carbonate (DEC) in a volume ratio of 3:3:4.

[0320]

[0321] - Battery characteristic evaluation

[0322] Using the coin-type half-cell manufactured as described above, the battery was charged (0.1C) in the CC-CV manner to 4.45 V at 25°C, then discharged (0.1C) in the CC manner to 2.5 V, and the charge / discharge capacity at this time was measured. The percentage (efficiency (%)) of the discharge capacity to the measured charge capacity is shown in Table 5 below.

[0323] Afterwards, the battery was charged (0.1C) in the CC-CV manner to 4.25 V at 25℃, then discharged (2.0C) in the CC manner to 2.5 V, and the charge / discharge capacity at this time was measured.

[0324] The percentage of the discharge capacity at 2.0C to the measured discharge capacity at 0.1C (2C / 0.1C) is shown in Table 5 below.

[0325] In addition, the DC internal resistance (DCIR) was calculated and shown in Table 5 below. The DCIR value is calculated by dividing the difference between the voltage at 60 seconds and the initial voltage while discharging at a constant current of 0.1 C during the initial charge and discharge by the applied current.

[0326] 0.1C(@25℃)2C(@25℃)2C / 0.1C(%)Efficiency (%)DCIR (Ω)Efficiency (%)Example 189.733.794.385.2Example 290.231.994.185.0Comparative Example 189.236.793.884.1Comparative Example 288.240.593.582.9Comparative Example 389.933.393.684.3

[0327] Through Table 5, it was confirmed that the battery including the positive electrode active material manufactured in Examples 1 and 2 had an efficiency (%) at 0.1C of 89.7% or more, a DCIR at 0.1C of 33.7 Ω or less, an efficiency at 2C of 94.0% or more, and a 2C / 0.1C of 85.0% or more.

[0328] On the other hand, it was confirmed that the batteries including the positive electrode active materials manufactured in Comparative Examples 1 and 2 had inferior output, resistance, and rate characteristics compared to the batteries including the positive electrode active materials manufactured in Examples 1 and 2, such that the efficiency (%) at 0.1C was less than 89.7%, the DCIR at 0.1C was more than 33.7 Ω, the efficiency at 2C was less than 94.0%, and the 2C / 0.1C was less than 85.0%. In addition, it was confirmed that the batteries including the positive electrode active materials manufactured in Comparative Example 3 had inferior output and rate characteristics compared to the batteries including the positive electrode active materials manufactured in Examples 1 and 2, such that the efficiency at 2C was less than 94.0%, and the 2C / 0.1C was less than 85.0%.

[0329] For reference, since the battery including the positive electrode active material manufactured in Comparative Example 4 had a poor rolling density, a separate battery characteristic evaluation was not performed.

[0330]

[0331] In conclusion, through Tables 4 and 5, it was confirmed that the positive electrode active material according to the present invention is in the form of a single particle, includes a lithium composite transition metal oxide containing nickel in an amount of 50 mol% or more among all metals excluding lithium, has a single crystallinity within a specific range, and has a grain size within a specific range, thereby improving the rolling density of the positive electrode active material and improving the electrochemical characteristics of a battery including the same.

Claims

It is a single particle form composed of 1.10 or less primary particles, and includes a lithium composite transition metal oxide containing nickel in an amount of 50 mol% or more among all metals excluding lithium. The single crystallinity (χ) according to the following formula 1 is 0.500 or more and 0.850 or less, A cathode active material having a crystal grain size (D) of 2.00㎛ or more and 5.00㎛ or less: [Formula 1] .

2. In claim 1, The above lithium composite transition metal oxide is a positive electrode active material having a composition represented by the following chemical formula 1: [Chemical Formula 1] Li 1+x Ni a Co b Mr c M 1 d O2 In the above chemical formula 1, Above M 1 is at least one selected from Al, W, Co, B, Zr, Y, Ce, Hf, La, Ba, F, P, S, Nb, Ta, Sc, Cr, V, Cu, Sr, Ti, Mg, Mo, Sn, Fe, Zn and Si, -0.10≤x≤0.10, 0.500≤a<1.000, 0 <b<0.500, 0<c<0.500, 0≤d≤0.100, a+b+c+d=1이다.

3. In claim 1, The above lithium composite transition metal oxide is a cathode active material comprising at least one doping element selected from Al, W, Co, B, Zr, Y, Ce, Hf, La, Ba, F, P, S, Nb, Ta, Sc, Cr, V, Cu, Sr, Ti, Mg, Mo, Sn, Fe, Zn and Si.

4. In claim 1, The average particle diameter of the above primary particles (D 50 ) is a positive electrode active material having a size of 2.35㎛ or more and 6.00㎛ or less.

5. A positive electrode comprising a positive electrode active material according to any one of claims 1 to 4.

6. A lithium secondary battery comprising a positive electrode according to claim 5.

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