Cathode active material, manufacturing method therefor, and cathode and lithium secondary battery comprising same

Abstract

The present invention relates to a cathode active material in which primary particles have a uniform particle diameter, resulting in a small amount of fine powder, and there is little particle breakage during a fine grinding process and a rolling process for manufacturing a lithium secondary battery. The present invention relates to: a cathode active material; a manufacturing method therefor; and a cathode and a lithium secondary battery, comprising same, in which the cathode active material comprises a lithium nickel cobalt manganese-based oxide containing, among the total transition metals, nickel at a content of 50 mol% or more, and in the form of a single-particle consisting of 10 or less of primary particles, and has a polydispersity index (PDI) value of 1.0 to 1.8 according to equation 1 described in the present specification.

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. 10-2023-0151125, 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 comprising the same, and more particularly, to a positive electrode active material having a uniform particle size, a method for producing the same, and a positive electrode and a lithium secondary battery comprising the same.

[0005]

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

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

[0008] Meanwhile, the lithium composite transition metal oxide has a problem of poor life characteristics at high temperatures, and when manufacturing a lithium secondary battery using the lithium composite transition metal oxide as a cathode active material, cracks and collapse of the cathode active material particles are likely to occur during the process of applying it to a cathode current collector and then rolling it. Accordingly, during the charge / discharge process of the lithium secondary battery, gas is generated due to a side reaction between the cathode active material and the electrolyte, and a swelling phenomenon occurs, which causes a problem of deterioration in the life characteristics.

[0009] Therefore, there is a need to develop positive electrode active materials that can improve the stability and lifespan characteristics of batteries.

[0010]

[0011] The present invention is an invention for solving the above problems, and aims to provide a cathode active material including a lithium composite transition metal oxide that can improve the stability and life characteristics of a battery.

[0012] In addition, the present invention aims to provide a manufacturing method for manufacturing the positive electrode active material.

[0013] In addition, the present invention aims to provide a lithium secondary battery with improved performance, including the positive electrode active material.

[0014]

[0015] To solve the above problem, the present invention provides a cathode active material, a method for manufacturing a cathode active material, a cathode, and a lithium secondary battery.

[0016]

[0017] (1) The present invention provides a cathode active material comprising a lithium nickel cobalt manganese oxide in the form of a single particle, having a nickel content of 50 mol% or more among the total transition metals and consisting of 10 or fewer primary particles, and having a polydispersity index (PDI) value of 1 to 1.8 according to the following formula 1.

[0018] [Formula 1]

[0019] PDI = .

[0020] (2) The present invention provides a positive electrode active material in the above (1), wherein the lithium nickel cobalt manganese oxide has a composition represented by the following chemical formula 1.

[0021] [Chemical Formula 1]

[0022] Li 1+x Ni a1 Co b1 Mn c1 M 1 d1 O2

[0023] In the above chemical formula 1,

[0024] 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,

[0025] -0.1≤x≤0.1, 0.5≤a1<1, 0 <b1<0.5, 0<c1<0.5, 0≤d1≤0.2, a1+b1+c1+d1=1이다.

[0026] (3) The present invention provides a positive electrode active material in (1) or (2) above, wherein the volume average particle diameter of the primary particles is 0.5 µm to 3.5 µm.

[0027] (4) The present invention provides a positive electrode active material in any one of the above (1) to (3), wherein the number average particle diameter of the primary particles is 0.5 µm to 2.0 µm.

[0028] (5) In any one of the above (1) to (4), the positive electrode active material has a D measured by PSA (particle size analyzer). 50 This provides a positive electrode active material having a diameter of 3㎛ to 5㎛.

[0029] (6) The present invention provides a positive electrode active material in which, in any one of (1) to (5) above, 3 g of the positive electrode active material is placed in a mold having an inner diameter of 13 mm and pressurized at 9 tons for 1 minute, and the ratio of the number of particles having a particle size of less than 1 ㎛ as measured by a PSA (particle size analyzer) with respect to the total number of particles is 2.5% or less.

[0030] (7) The present invention provides a method for producing a positive electrode active material according to any one of (1) to (6), comprising the steps of: (A) mixing a nickel-cobalt-manganese hydroxide having a nickel content of 50 mol% or more among the total transition metals and a lithium-containing raw material to produce a mixture; and (B) first firing the mixture at 600°C to 900°C in an air atmosphere, then continuously raising the temperature to 920°C to 1000°C, and second firing at 920°C to 1000°C to produce a fired product.

[0031] (8) The present invention provides a method for producing a positive electrode active material in the above (7), wherein the nickel-cobalt-manganese hydroxide has a composition represented by the following chemical formula 2.

[0032] [Chemical Formula 2]

[0033] Ni a2 Co b2 Mn c2 M 2 2(OH)2

[0034] In the above chemical formula 2,

[0035] 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,

[0036] 0.5≤a2<1, 0 <b2<0.5, 0<c2<0.5, 0≤d2≤0.2, a2+b2+c2+d2=1이다.

[0037] (9) The present invention provides a method for manufacturing a positive electrode active material, wherein, in the above (7) or (8), the first calcination is performed for 2 to 12 hours.

[0038] (10) The present invention provides a method for manufacturing a positive electrode active material, wherein the secondary firing is performed for 4 to 14 hours in any one of the above (7) to (9).

[0039] (11) The present invention provides a method for manufacturing a positive electrode active material, further comprising the step of (C) pulverizing the sintered product in any one of the above (7) to (10).

[0040] (12) The present invention provides a method for producing a positive electrode active material, wherein the fine grinding is performed by airflow grinding in the above (11).

[0041] (13) The present invention provides a method for producing a positive electrode active material, wherein the airflow grinding in (12) is performed under a pressure of 1 bar to 5 bar.

[0042] (14) The present invention provides a positive electrode comprising a positive electrode active material according to any one of (1) to (6).

[0043] (15) The present invention provides a lithium secondary battery comprising a positive electrode according to (14); a negative electrode; a separator interposed between the positive electrode and the negative electrode; and an electrolyte.

[0044]

[0045] The positive electrode active material of the present invention includes a lithium composite transition metal oxide, and has a polydispersity index value according to Equation 1 described herein that satisfies a specific range, so that the particle size is uniform, thereby improving particle breakage and improving the life performance of a lithium secondary battery.

[0046] In addition, according to the method for manufacturing a positive electrode active material of the present invention, the positive electrode active material described above can be effectively manufactured. Specifically, the method for manufacturing a positive electrode active material according to the present invention comprises first firing a mixture containing a positive electrode active material precursor and a lithium-containing raw material at 600°C to 900°C, then continuously raising the temperature to 920°C to 1000°C, and then second firing at 920°C to 1000°C, thereby improving the particle size uniformity of the primary particles.

[0047] The cathode and lithium secondary battery according to the present invention can have excellent high-temperature stability and life performance.

[0048]

[0049] FIG. 1 is a drawing showing a plastic profile according to one embodiment of the present invention.

[0050] Figure 2 is an SEM image of the positive electrode active material of Example 1.

[0051] Figure 3 is an SEM image of the positive electrode active material of Example 2.

[0052] Figure 4 is an SEM image of the positive electrode active material of Comparative Example 1.

[0053] Figure 5 is an SEM image of the positive electrode active material of Comparative Example 2.

[0054]

[0055] Hereinafter, the present invention will be described in more detail to help understand the present invention.

[0056] Terms or words used in this specification and claims should not be interpreted as limited to their usual or dictionary meanings, but should be interpreted as meanings and concepts that conform to the technical spirit of the present invention, based on the principle that the inventor can appropriately define the concept of the term to explain his or her own invention in the best possible manner.

[0057]

[0058] 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.

[0059] In this specification, the term 'on' means not only when a configuration is formed directly on the top surface of another configuration, but also when a third configuration is interposed between these configurations.

[0060] In this specification, the term "single particle form" refers to a form composed of 10 or fewer primary particles, in contrast to the spherical secondary particle form formed by the agglomeration of tens to hundreds of primary particles manufactured by conventional methods. Specifically, the single particle form in the present invention may be a single particle composed of one primary particle, or may be a secondary particle form in which several primary particles are agglomerated.

[0061] 'Primary particle' refers to the smallest particle unit recognized when observing a positive electrode active material through a scanning electron microscope, and 'secondary particle' refers to a secondary structure formed by the aggregation of multiple primary particles.

[0062] In this specification, the 'volume average particle diameter of primary particles' is a value according to the following Equation 2, and the area of ​​each primary particle is calculated through the number of pixels corresponding to each of n primary particles existing in the SEM image, and the radius (r) of a circle having the same area as the area of ​​each primary particle i ) to determine the particle diameter (D) of each primary particle present in the SEM image. i =2r i ) and volume (V i =4 / 3×πr i 3) is calculated, and the product of the calculated volume and particle diameter for each primary particle is calculated (V i D i ) is the total volume (V) calculated i ) is the value derived by dividing by the total sum of all values.

[0063] [Formula 2]

[0064]

[0065] In the above equation 2,

[0066] n is the number of primary particles present in the SEM image,

[0067] V i is the volume of one primary particle among n primary particles,

[0068] V i D i is the volume of one primary particle among n primary particles (V i ) and entrance diameter (D i ) is the product of

[0069] In this specification, the 'number average particle diameter of primary particles' is calculated by calculating the area of ​​the primary particles through the number of pixels corresponding to each of n primary particles existing in the SEM image, and the radius (r) of a circle having the same area as the area of ​​each of the primary particles i ) to determine the particle diameter (D) of each primary particle present in the SEM image. i =2r i ) is calculated and the total sum of the calculated particle sizes is divided by the number of primary particles.

[0070] [Formula 3]

[0071]

[0072] In the above equation 3,

[0073] n is the number of primary particles present in the SEM image,

[0074] D i is the particle diameter (D) of one primary particle among n primary particles. i )am.

[0075] In this specification, the term 'D measured by PSA (particle size analyzer) 50 ' means the particle size at the 50% point of the cumulative volume distribution according to particle size. The above D 50 The powder to be measured is dispersed in a dispersion medium, and then introduced into a commercially available laser diffraction particle size measuring device (e.g., Microtrac's S3500), and the particle size distribution is calculated by measuring the difference in diffraction patterns according to particle size when the particles pass through the laser beam, and the particle diameter at the point where it becomes 50% of the volume cumulative distribution according to particle size in the measuring device is calculated, thereby allowing measurement.

[0076]

[0077] positive electrode active material

[0078] The present invention provides a cathode active material comprising a lithium nickel cobalt manganese oxide (lithium composite transition metal oxide) in the form of a single particle, having a nickel content of 50 mol% or more among the total transition metal and consisting of 10 or fewer primary particles, and having a polydispersity index (PDI) value of 1.0 to 1.8 according to the following formula 1. The lithium nickel cobalt manganese oxide may have a layered structure.

[0079] [Formula 1]

[0080] PDI = .

[0081]

[0082] The present inventors have found that when a cathode active material includes a lithium nickel cobalt manganese oxide in the form of a single particle and the polydispersity index (PDI) value according to the above formula 1 satisfies a specific range, the particle size of the primary particles is uniform, resulting in less fine dust, and less breakage of the particles during the fine pulverization process and the rolling process for manufacturing a lithium secondary battery, thereby improving the life performance of the lithium secondary battery, and have completed the present invention.

[0083]

[0084] According to the present invention, the positive electrode active material has a polydispersity index (PDI) value of 1.0 to 1.8 according to Equation 1. Theoretically, when all primary particles forming the lithium nickel cobalt manganese oxide have the same particle size, the polydispersity index (PDI) value is 1.0, and the more uniform the particle size, the closer the PDI value is to 1.0. Specifically, the polydispersity index value may be 1.0 or more, 1.1 or more, 1.2 or more, 1.3 or more, 1.4 or more, 1.5 or more, or 1.6 or more, and may be 1.7 or less, or 1.8 or less. When the polydispersity index value satisfies the above range, the uniformity of the primary particles may be improved and particle breakage may be reduced. The polydispersity index value is determined by a complex interaction of the manufacturing method of the positive electrode active material, the composition, the size of the primary particles, the particle size distribution, etc., and is not determined by a single factor alone.

[0085] Meanwhile, when the polydispersity index of the positive electrode active material exceeds 1.8, the primary particle size becomes non-uniform, fine particles increase, and particle breakage increases during the fine grinding process and the rolling process for manufacturing lithium secondary batteries, which causes a problem of reduced life performance of the lithium secondary battery.

[0086]

[0087] According to the present invention, the volume average particle diameter of the primary particles may be 0.5 µm to 3.5 µm. Specifically, the volume average particle diameter of the primary particles may be 0.5 µm or more, 0.6 µm or more, 0.7 µm or more, 0.8 µm or more, 0.9 µm or more, 1.0 µm or more, 1.1 µm or more, 1.2 µm or more, 1.3 µm or more, 1.4 µm or more, 1.5 µm or more, 1.6 µm or more, 1.7 µm or more, 1.8 µm or more, 1.9 µm or more, 2.0 µm or more, 2.1 µm or more, 2.2 µm or more, or 2.3 µm or less, 2.6 µm or less, 2.7 µm or less, 2.8 µm or less, 2.9 µm or less, or 3.0 µm or less. When the volume average particle size of the primary particles is within the above range, the positive electrode active material can have a single particle form, and the movement of lithium is advantageous, so that both the lifespan and capacity characteristics of the battery are improved, and the electrochemical performance can be optimized.

[0088] According to the present invention, the number average particle diameter of the primary particles may be 0.5 μm to 2.0 μm. Specifically, the number average particle diameter of the primary particles may be 0.5 μm or more, 0.6 μm or more, 0.7 μm or more, 0.8 μm or more, 0.9 μm or more, 1.0 μm or more, 1.1 μm or more, 1.2 μm or more, or 1.3 μm or more, and 1.6 μm or less, 1.7 μm or less, 1.8 μm or less, 1.9 μm or less, or 2.0 μm or less. When the number average particle diameter of the primary particles is within the above range, the positive electrode active material may have a single particle form, and both the lifespan and capacity characteristics of the battery may be improved, so that the electrochemical performance may be optimized.

[0089]

[0090] According to the present invention, the lithium nickel cobalt manganese oxide may have a nickel content of 50 mol% or more, 51 mol% or more, 52 mol% or more, 53 mol% or more, 54 mol% or more, 55 mol% or more, 56 mol% or more, 57 mol% or more, 58 mol% or more, 59 mol% or more, or 60 mol% or more among the total transition metals. That is, the lithium nickel cobalt manganese oxide may be a lithium composite transition metal oxide having a high nickel content. In this case, the energy density of the lithium secondary battery may be improved.

[0091]

[0092] According to the present invention, the lithium nickel cobalt manganese oxide may have a composition represented by the following chemical formula 1.

[0093] [Chemical Formula 1]

[0094] Li 1+x Ni a1 Co b1 Mn c1 M 1 d1 O2

[0095] In the above chemical formula 1,

[0096] 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,

[0097] -0.1≤x≤0.1, 0.5≤a1<1, 0 <b1<0.5, 0<c1<0.5, 0≤d1≤0.2, a1+b1+c1+d1=1이다.

[0098] The above x may be -0.1 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 0.07 or less, 0.08 or less, 0.09 or less, or 0.1 or less. When x satisfies the above range, high capacity characteristics and high energy density per unit volume can be realized.

[0099] According to the present invention, in the chemical formula 1, a1 refers to the molar ratio of nickel among the metal elements in the lithium nickel cobalt manganese 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, or 0.60 or more, and may be 0.70 or less, 0.75 or less, 0.80 or less, 0.85 or less, 0.90 or less, 0.95 or less, or less than 1.0. When a1 satisfies the above range, high energy characteristics can be implemented, and particularly, when a1 is 0.6 to 0.7, high energy density and high stability can be implemented during high voltage driving.

[0100] According to the present invention, in the chemical formula 1, b1 refers to the atomic molar ratio of cobalt among the metal elements in the lithium nickel cobalt manganese oxide, and may be greater than 0.0, or 0.01 or more, and may be 0.15 or less, 0.20 or less, 0.30 or less, 0.40 or less, or less than 0.50. When b1 satisfies the above range, stability can be improved during the charge / discharge process, and rate characteristics can be enhanced.

[0101] According to the present invention, in the chemical formula 1, c1 refers to the molar ratio of manganese among the metal elements in the lithium nickel cobalt manganese oxide, and may be greater than 0.0, or 0.01 or more, 0.05 or more, 0.10 or more, 0.15 or more, 0.20 or more, 0.25 or more, or 0.30 or more, and may be 0.35 or less, 0.40 or less, 0.45 or less, or less than 0.50. When c1 satisfies the above range, high-temperature stability may increase, and side reactions with the electrolyte may be relatively reduced.

[0102] According to the present invention, in the chemical formula 1, d1 is M among the metal elements in the lithium nickel cobalt manganese oxide. 1 This refers to the molar ratio of elements, and may be 0.0 or more, 0.05 or less, 0.1 or less, or 0.2 or less. When d1 satisfies the above range, the stability of the crystal structure of the positive electrode active material is improved, and the particle shape can be improved.

[0103]

[0104] According to the present invention, the M 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. 1 It is a doping element that can improve the crystallinity and single particle degree of the positive electrode active material, and is not necessarily included, but is included in the above M 1 If this is included, the capacity characteristics and life characteristics of the battery can be improved.

[0105]

[0106] According to the present invention, the positive electrode active material has a D measured by PSA (particle size analyzer) 50 This may be 3㎛ to 5㎛. D of the positive electrode active material 50Specifically, the particle size of the positive electrode active material may be 3.00 ㎛ or more, 3.10 ㎛ or more, 3.20 ㎛ or more, 3.30 ㎛ or more, 3.40 ㎛ or more, or 3.50 ㎛ or more, and 4.50 ㎛ or less, 4.60 ㎛ or less, 4.70 ㎛ or less, 4.80 ㎛ or less, 4.90 ㎛ or less, or 5.00 ㎛ or less. D measured by PSA (particle size analyzer) of the positive electrode active material 50 Within this range, both the life and capacity characteristics of the battery including it are improved, and the electrochemical performance can be optimized. For reference, D 50 If it is less than 3㎛, the life of the battery may be reduced, and if it is more than 5㎛, the capacity of the battery may be reduced.

[0107]

[0108] According to the present invention, when 3 g of the positive electrode active material is placed in a mold having an inner diameter of 13 mm and pressurized at 9 tons for 1 minute, the ratio of particles having a particle size of less than 1 μm as measured by a PSA (particle size analyzer) to the total number of particles may be 2.5% or less, specifically 2.0% or less, 1.5% or less, 1.4% or less, 1.3% or less, or 1.2% or less. In this case, when rolling for manufacturing a lithium secondary battery, particle breakage of the positive electrode active material is reduced, so that the lifespan of the lithium secondary battery may be improved.

[0109]

[0110] Method for manufacturing positive electrode active material

[0111] The present invention provides a method for producing the above-described positive electrode active material. That is, the positive electrode active material according to the present invention is produced by the following method for producing a positive electrode active material.

[0112] A method for manufacturing a cathode active material according to the present invention comprises the steps of (A) mixing a nickel-cobalt-manganese hydroxide having a nickel content of 50 mol% or more among the total transition metals and a lithium-containing raw material to manufacture a mixture; and (B) first firing the mixture at 600°C to 900°C in an air atmosphere, then continuously raising the temperature to 920°C to 1000°C, and second firing at 920°C to 1000°C to manufacture a fired product.

[0113]

[0114] The present inventors have discovered that when the mixture is first fired at 600°C to 900°C, then continuously heated to 920°C to 1000°C, and then fired a second time at 920°C to 1000°C, a lithium nickel cobalt manganese oxide having a uniform primary particle size is produced in the form of single particles, thereby reducing breakage of the positive electrode active material particles during rolling for the manufacture of a lithium secondary battery, thereby completing the present invention.

[0115] For example, the positive electrode active material according to the present invention can be manufactured by heating the mixture from room temperature to 850°C as shown in Fig. 1, performing a first firing at 850°C for a predetermined period of time, then continuously raising the temperature to 950°C and performing a second firing at 950°C for a predetermined period of time. Fig. 1 is a drawing showing a firing profile according to one embodiment of the present invention.

[0116]

[0117] (A) Step

[0118] The above step (A) is a step of preparing a mixture by mixing a nickel-cobalt-manganese hydroxide (hereinafter, composite transition metal hydroxide or positive electrode active material precursor) having a nickel content of 50 mol% or more among the total transition metals and a lithium-containing raw material.

[0119]

[0120] According to the present invention, the nickel-cobalt-manganese hydroxide may have a composition represented by the following chemical formula 2.

[0121] [Chemical Formula 2]

[0122] Ni a2 Co b2 Mn c2 M 2 d2 (OH)2

[0123] In the above chemical formula 2,

[0124] 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,

[0125] 0.5≤a2<1, 0 <b2<0.5, 0<c2<0.5, 0≤d2≤0.2, a2+b2+c2+d2=1이다.

[0126] According to the present invention, in the chemical formula 2, a2 ​​refers to the molar ratio of nickel among the metal elements in the nickel-cobalt-manganese hydroxide, 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, or 0.60 or more, and may be 0.70 or less, 0.75 or less, 0.80 or less, 0.85 or less, 0.90 or less, 0.95 or less, or less than 1.0. When a2 satisfies the above range, a high-capacity characteristic of a battery including a positive electrode active material thus produced can be implemented, and in particular, when a1 is 0.6 to 0.7, a battery including a positive electrode active material thus produced can exhibit a high energy density when driven at a high voltage, so that a high-capacity characteristic can be implemented.

[0127] According to the present invention, in the chemical formula 2, b2 refers to the atomic molar ratio of cobalt among the metal elements in the nickel-cobalt-manganese hydroxide, and may be greater than 0.0, or 0.01 or more, and may be 0.15 or less, 0.20 or less, 0.30 or less, 0.40 or less, or less than 0.50. When b2 satisfies the above range, the stability of a battery including the resulting positive electrode active material may be improved and the rate characteristics may be enhanced during the charge / discharge process.

[0128] According to the present invention, in the chemical formula 2, c2 refers to the molar ratio of manganese among the metal elements in the nickel-cobalt-manganese hydroxide, and may be greater than 0.0, or 0.01 or more, 0.05 or more, 0.10 or more, 0.15 or more, 0.20 or more, 0.25 or more, or 0.30 or more, and may be 0.35 or less, 0.40 or less, 0.45 or less, or less than 0.50. When c2 satisfies the above range, a high-capacity characteristic of a battery including a positive electrode active material produced as a result can be implemented. In addition, the high-temperature stability of the battery can be increased, and side reactions with the electrolyte can be relatively reduced.

[0129] According to the present invention, in the chemical formula 2, d2 is M among the metal elements in the nickel-cobalt-manganese hydroxide. 1 This refers to the molar ratio of elements, and may be 0.0 or more, 0.05 or less, 0.1 or less, or 0.2 or less. When d2 satisfies the above range, the crystal structure stability of the resulting positive electrode active material may be improved and the particle shape may be improved.

[0130]

[0131] According to the present invention, the lithium-containing raw material may be lithium-containing sulfate, nitrate, acetate, carbonate, oxalate, citrate, halide, hydroxide or oxyhydroxide, and is not particularly limited as long as it can be dissolved in water. Specifically, the lithium-containing raw material may be Li2CO3, LiNO3, LiNO2, LiOH, LiOHㆍH2O, LiH, LiF, LiCl, LiBr, LiI, CH3COOLi, Li2O, lithium acetate, lithium dicarboxylate, lithium citrate, lithium fatty acid, alkyl lithium, lithium halide, and the like, and any one of these or a mixture of two or more thereof may be used.

[0132] According to the present invention, the composite transition metal hydroxide and the lithium-containing raw material can be mixed so that the ratio (M:Li) of the total mole number (M) of transition metals included in the composite transition metal hydroxide and the mole number (Li) of lithium included in the lithium-containing raw material is 1:1.0 to 1.1, 1:1.01 to 1.09, 1:1.02 to 1.08, 1:1.03 to 1.07, 1:1.04 to 1.07, or 1:1.05 to 1.07.

[0133] Meanwhile, during the mixing in step (A), a raw material containing a doping element may be further mixed. The raw material containing the doping element acts as a plus (flux) during firing, thereby further improving the lifespan and resistance characteristics of a battery including a positive electrode active material.

[0134]

[0135] (B) Step

[0136] The above step (B) is a step of manufacturing a sintered product by first firing the mixture at 600°C to 900°C in an air atmosphere, then continuously raising the temperature to 920°C to 1000°C, and then firing it a second time at 920°C to 1000°C.

[0137]

[0138] According to the present invention, when the mixture is first fired at 600°C to 900°C, the lithium-containing raw material is melted and sufficiently uniformly distributed on the surface of the positive electrode active material precursor, thereby effectively reacting the lithium and the positive electrode active material precursor, and ultimately, after the second firing, an active material having a uniform primary particle shape can be manufactured. Specifically, the primary firing temperature may be 600°C or higher, 610°C or higher, 620°C or higher, 630°C or higher, 640°C or higher, 650°C or higher, 660°C or higher, 670°C or higher, 680°C or higher, 690°C or higher, 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, or 830°C or higher, and may be 870°C or lower, 880°C or lower, 890°C or lower, or 900°C or lower. When the primary firing temperature is within the above range, the uniformity of the primary particles may increase. Meanwhile, when the first firing temperature is less than 600℃, the reaction between lithium and the positive electrode active material precursor does not proceed sufficiently, so that more than 10 primary particles are aggregated to form a positive electrode active material in the form of secondary particles during the second firing, which causes a problem of reduced life characteristics. When it exceeds 900℃, the growth of the primary particles progresses rapidly, inducing non-uniform particle growth during the second firing, which causes a problem of reduced capacity.

[0139] According to the present invention, the primary firing can be performed under an oxygen atmosphere or an air atmosphere.

[0140] According to the present invention, the primary calcination may be performed for 2 to 12 hours. In this case, the reaction between the nickel-cobalt-manganese hydroxide and lithium proceeds appropriately, so that lithium can be evenly distributed throughout the positive electrode active material, and uniform particle growth can be achieved overall.

[0141]

[0142] Immediately after the above first firing is completed, the temperature is continuously increased to 920°C to 1000°C, and when a second firing is performed at 920°C to 1000°C, lithium is intercalated into the positive electrode active material precursor to form a layered structure, and the primary particle interfaces are combined to cause the primary particles to grow, and a fired product is manufactured. At this time, the fired product is a lithium nickel cobalt manganese oxide in the form of a single particle having a nickel content of 50 mol% or more among the total transition metal and composed of 10 or fewer primary particles. When the second firing temperature is within the above range, the size of the primary particles can sufficiently grow, the structural stability can increase, and the thermal stability and life characteristics can be improved. Meanwhile, if the secondary firing temperature is less than 920℃, the size of the primary particles is small, so that an uneven cathode active material in the form of secondary particles that cannot be formed into a single particle is produced, which reduces the lifespan. If it exceeds 1000℃, the size of the primary particles may become too large, which may reduce the capacity and performance of the battery.

[0143] The above secondary calcination can be performed under a lithium transition metal oxygen atmosphere or an air atmosphere.

[0144] According to the present invention, the secondary firing may be performed for 4 to 14 hours. In this case, primary particles having high crystallinity and an appropriate size can be obtained, and production efficiency can be improved.

[0145]

[0146] The present invention divides the sintering process into primary sintering and secondary sintering, and the primary sintering temperature is lower than the secondary sintering temperature, so that the particle uniformity of the positive electrode active material can be increased, and ultimately, the lifespan of a battery including the positive electrode active material can be improved.

[0147]

[0148] The method for manufacturing a cathode active material according to the present invention may further include (C) a step of pulverizing the sintered product in order to break up large particles that have been agglomerated with weak force during the sintering process to form single particles.

[0149] According to the present invention, the above-described fine grinding may be performed by airflow grinding. In this case, the particles within the positive electrode active material can be disintegrated through collisions between particles during the sintering process, thereby improving the uniformity of the positive electrode active material loading during electrode manufacturing.

[0150] According to the present invention, the air-pulverization may be performed under a pressure of 1 bar to 5 bar. In this case, the amount of fine particles that may be generated through collisions between particles during the fine pulverization process can be reduced.

[0151]

[0152] anode

[0153] The present invention provides a positive electrode comprising the positive electrode active material.

[0154] The positive electrode may include a positive electrode current collector and a positive electrode active material layer formed on the positive electrode current collector, and the positive electrode active material layer may include the positive electrode active material.

[0155] The positive electrode current collector may include a highly conductive metal, and is not particularly limited as long as it is easily adhered to by the positive electrode active material layer and does not react within the voltage range of the battery. The positive electrode current collector may be made of, for example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, etc. In addition, the positive electrode current collector may typically have a thickness of 3 ㎛ to 500 ㎛, and fine unevenness may be formed on the surface of the current collector to increase the adhesion of the positive electrode active material. For example, the positive electrode current collector may be used in various forms such as a film, a sheet, a foil, a net, a porous body, a foam, a non-woven fabric, etc.

[0156] The above-described positive electrode active material layer may optionally include a conductive material and a binder, together with the positive electrode active material, as needed. In this case, the positive electrode active material may be included in an amount of 80 wt% to 99 wt%, more specifically 85 wt% to 98.5 wt%, based on the total weight of the positive electrode active material layer, and excellent capacity performance may be exhibited within this range.

[0157] The conductive material is used to provide conductivity to the electrode, and in the battery to be formed, as long as it does not cause a chemical change and has electronic conductivity, it can be used without any special restrictions. Specific examples include graphite such as natural graphite or artificial graphite; carbon-based materials such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, and carbon fiber; metal powders or metal fibers such as copper, nickel, aluminum, and silver; conductive tubes such as carbon nanotubes; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives, and the like. One of these may be used alone or a mixture of two or more may be used. The conductive material may be included in an amount of 0.1 wt% to 15 wt% based on the total weight of the positive electrode active material layer.

[0158] The above binder serves to improve the adhesion between positive electrode active material particles and the adhesion between the positive electrode active material and the current collector. Specific examples include polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylalcohol, polyacrylonitrile, polymethyl methacrylate, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene butadiene rubber (SBR), fluoroelastomer, polyacrylic acid, and polymers in which hydrogens of these are substituted with Li, Na, or Ca, or various copolymers thereof, and one of these may be used alone or a mixture of two or more thereof. The above binder may be included in an amount of 0.1 wt% to 15 wt% based on the total weight of the positive electrode active material layer.

[0159] The positive electrode can be manufactured according to a conventional positive electrode manufacturing method, except that the positive electrode active material described above is used. Specifically, the positive electrode can be manufactured by applying a composition for forming a positive electrode active material layer, which is manufactured by dissolving or dispersing the positive electrode active material and optionally a binder, a conductive agent, and a dispersant in a solvent as needed, onto a positive electrode current collector, followed by drying and rolling, or by casting the composition for forming a positive electrode active material layer onto a separate support, peeling the film from the support, and laminating the resulting film onto a positive electrode current collector.

[0160] The solvent may be a solvent generally used in the relevant technical field, such as dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), dimethylformamide (DMF), acetone, or water. One of these may be used alone or a mixture of two or more thereof may be used. The amount of the solvent used is sufficient to dissolve or disperse the positive electrode active material, conductive material, binder, and dispersant in consideration of the coating thickness and manufacturing yield of the slurry, and to have a viscosity that can exhibit excellent thickness uniformity when applied thereafter for manufacturing the positive electrode.

[0161]

[0162] lithium secondary battery

[0163] The present invention provides a lithium secondary battery comprising: the positive electrode; the negative electrode; a separator interposed between the positive electrode and the negative electrode; and an electrolyte.

[0164]

[0165] The above lithium secondary battery may optionally further include a battery container that houses the electrode assembly of the positive electrode, negative electrode, and separator, and a sealing member that seals the battery container.

[0166]

[0167] The above negative electrode may include a negative electrode current collector and a negative electrode active material layer positioned on the negative electrode current collector.

[0168] The negative electrode current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery. 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.

[0169] The above negative electrode active material layer may optionally include a binder and a conductive material together with the negative electrode active material.

[0170] As the negative electrode active material, a compound capable of reversible intercalation and deintercalation of lithium may be used. Specific examples include carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber, and amorphous carbon; metallic compounds capable of alloying with lithium such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloy, Sn alloy, or Al alloy; SiO β(0<β<2), SnO2, vanadium oxide, lithium vanadium oxide, and other metal oxides capable of doping and dedoping lithium; or composites containing the above metallic compounds and carbonaceous materials, such as Si-C composites or Sn-C composites, and any one or a mixture of two or more of these may be used. In addition, a metallic lithium thin film may be used as the negative electrode active material. In addition, both low-crystalline carbon and high-crystalline carbon may be used as the carbonaceous material. Representative examples of low-crystalline carbon include soft carbon and hard carbon, and representative examples of high-crystalline carbon include natural graphite or artificial graphite in the form of amorphous, plate-like, flaky, spherical or fibrous shapes, Kish graphite, pyrolytic carbon, mesophase pitch-based carbon fiber, meso-carbon microbeads, mesophase pitches, and high-temperature calcined carbon such as petroleum or coal tar pitch derived cokes. The negative electrode active material may be included in an amount of 80 wt% to 99 wt% based on the total weight of the negative electrode active material layer.

[0171] The binder of the above-described negative electrode active material layer is a component that assists in bonding between the conductive material, the active material, and the current collector, and is typically added in an amount of 0.1 wt% to 10 wt% based on the total weight of the negative electrode active material layer. Examples of such binders include polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene-butadiene rubber, nitrile-butadiene rubber, fluororubber, and various copolymers thereof.

[0172] The conductive material of the above-described negative electrode active material layer is a component for further improving the conductivity of the negative electrode active material, and may be added in an amount of 10 wt% or less, preferably 5 wt% or less, based on the total weight of the negative electrode active material layer. The conductive material is not particularly limited as long as it has conductivity without causing a chemical change in the battery, and examples thereof include graphite such as natural graphite or artificial graphite; carbon black such as acetylene black, Ketjen black, channel black, furnace black, lamp black, and thermal black; conductive fibers such as carbon fiber or metal fiber; fluorinated carbon; metal powder such as aluminum or nickel powder; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives.

[0173] The above negative electrode can be manufactured by applying and drying a composition for forming a negative electrode active material layer prepared by dissolving or dispersing a negative electrode active material, and optionally a binder and a conductive material in a solvent, on a negative electrode current collector, or by casting the composition for forming a negative electrode active material layer on a separate support, and then laminating the film obtained by peeling it off from the support on a negative electrode current collector.

[0174] The above separator separates the negative electrode and the positive electrode and provides a passage for lithium ions to move. Any separator commonly used in lithium secondary batteries can be used without any particular restrictions, and in particular, one having low resistance to ion movement of the electrolyte and excellent electrolyte moisture 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, may be used. In addition, a conventional porous nonwoven fabric, for example, a nonwoven fabric made of high-melting-point glass fiber, polyethylene terephthalate fiber, etc. may also be used. In addition, a coated separator containing a ceramic component or a polymer material to secure heat resistance or mechanical strength may be used, and may optionally be used in a single-layer or multi-layer structure.

[0175] Examples of the electrolyte include, but are not limited to, organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel-type polymer electrolytes, solid inorganic electrolytes, and molten inorganic electrolytes that can be used in the manufacture of lithium secondary batteries. As a specific example, the electrolyte may include an organic solvent and a lithium salt.

[0176] As the organic solvent, any solvent that can serve as a medium through which ions involved in the electrochemical reaction of the battery can move may be used without particular limitation. Specifically, the organic solvent includes ester solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, and ε-caprolactone; ether solvents such as dibutyl ether or tetrahydrofuran; ketone solvents such as cyclohexanone; aromatic hydrocarbon solvents such as benzene and fluorobenzene; carbonate solvents such as dimethylcarbonate (DMC), diethylcarbonate (DEC), ethylmethylcarbonate (EMC), ethylenecarbonate (EC), and propylene carbonate (PC); Alcohol solvents such as ethyl alcohol, isopropyl alcohol, etc.; nitriles such as R-CN (R is a linear, branched, or cyclic hydrocarbon group having 2 to 20 carbon atoms and may include a double-bonded aromatic ring or an ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; or sulfolanes, etc. can be used. Among these, carbonate solvents are preferable, and a mixture of a cyclic carbonate (e.g., ethylene carbonate or propylene carbonate) having high ionic conductivity and high dielectric constant that can improve the charge / discharge performance of a battery and a low-viscosity linear carbonate compound (e.g., ethyl methyl carbonate, dimethyl carbonate, or diethyl carbonate) is more preferable.

[0177] The above lithium salt can be used without any special limitation as long as it is a compound that can provide lithium ions used in a lithium secondary battery. Specifically, the anion of the above lithium salt is F - , Cl - , Br - , I - , NO3 - , N(CN)2 - , BF4 - , CF3CF2SO3 - , (CF3SO2)2N - , (FSO2)2N - , CF3CF2(CF3)2CO - , (CF3SO2)2CH - , (SF5)3C - , (CF3SO2)3C - , CF3(CF2)7SO3 - , CF3CO2 - , CH3CO2 - , SCN - and (CF3CF2SO2)2N - At least one selected from the group consisting of may be used, and the lithium salt may be LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAl04, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2, LiCl, LiI, or LiB(C2O4)2. It is preferable to use the concentration of the lithium salt within the range of 0.1 M to 2.0 M. When the concentration of the lithium salt is within the above range, the electrolyte can exhibit excellent electrolyte performance because it has appropriate conductivity and viscosity, and lithium ions can move effectively.

[0178] 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 lifespan of the battery, suppressing battery capacity decrease, and improving the discharge capacity of the battery. At this time, the additives may be included in an amount of 0.1 wt% to 5 wt% based on the total weight of the electrolyte.

[0179]

[0180] Since the lithium secondary battery including the positive electrode active material according to the present invention has excellent performance, it is useful in the fields of portable devices such as mobile phones, laptop computers, and digital cameras, and electric vehicles such as hybrid electric vehicles (HEVs) and electric vehicles (EVs).

[0181] 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.

[0182] 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.

[0183] Accordingly, a battery module including the lithium secondary battery as a unit cell and a battery pack including the same are provided.

[0184] 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.

[0185]

[0186] 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.

[0187]

[0188] Examples and Comparative Examples

[0189] Example 1

[0190] A composite transition metal hydroxide (composition: Ni) in the form of secondary particles formed by the agglomeration of tens to hundreds of primary particles in an acoustic mixer 0.60 Co 0.05 Mn 0.35 (OH)2, D 50 : 3.5㎛) and Li2CO3 were added so that the ratio of the total mole number of transition metals (Ni+Co+Mn) included in the complex transition metal hydroxide and the mole number of lithium (Li) included in Li2CO3 ((Ni+Co+Mn):Li) was 1:1.05, and the mixture was prepared by sequentially mixing at 40 g (g: gravitational acceleration) for 2 minutes, at 80 g for 1 minute, and at 50 g for 2 minutes.

[0191] After the above mixture was placed in a circular alumina crucible (75 mm × 75 mm), the first firing was performed at 850°C for 4 hours in an air atmosphere, and then the temperature was continuously increased to 950°C (heating rate: 10°C / min), and the second firing was performed at 950°C for 14 hours to manufacture a sintered product.

[0192] The above-mentioned product was pulverized using a jet mill (Isaac ENC Co., Ltd., Air Jet Mill) at a speed of 12 g / min under 3.5 bar to manufacture a cathode active material.

[0193]

[0194] Example 2

[0195] The mixture manufactured in Example 1 was placed in a circular alumina crucible (75 mm × 75 mm), and then fired for the first time at 850°C for 4 hours in an air atmosphere. Then, the temperature was continuously increased to 940°C (heating rate: 10°C / min), and fired for the second time at 940°C for 14 hours to manufacture a fired product.

[0196] The above-mentioned product was pulverized using a jet mill (Isaac ENC Co., Ltd., Air Jet Mill) at a speed of 12 g / min under 3.5 bar to manufacture a cathode active material.

[0197]

[0198] Comparative Example 1

[0199] The mixture prepared in Example 1 was placed in a circular alumina crucible (75 mm × 75 mm) and then fired at 950°C for 14 hours in an air atmosphere to produce a fired product.

[0200] The above-mentioned product was pulverized using a jet mill (Isaac ENC Co., Ltd., Air Jet Mill) at a speed of 12 g / min under 3.5 bar to manufacture a cathode active material.

[0201]

[0202] Comparative Example 2

[0203] The mixture manufactured in Example 1 was placed in a circular alumina crucible (75 mm × 75 mm), and then fired for the first time at 950°C for 14 hours in an air atmosphere. Then, the temperature was continuously lowered to 850°C (lowering speed: 10°C / min), and fired for the second time at 850°C for 4 hours to manufacture a fired product.

[0204] The above-mentioned product was pulverized using a jet mill (Isaac ENC Co., Ltd., Air Jet Mill) at a speed of 12 g / min under 3.5 bar to manufacture a cathode active material.

[0205]

[0206] Experimental example

[0207] Experimental Example 1: Analysis of positive electrode active material (1)

[0208] Using SEM (FEI, Inspect F), SEM images of each positive electrode active material manufactured in the examples and comparative examples were obtained, and using an image processing program (LG Chemical, DX program), the boundaries of the primary particles existing in the SEM images were divided to obtain images represented in random colors.

[0209] Meanwhile, SEM images of the positive electrode active materials of Examples 1 and 2 and Comparative Examples 1 and 2 are shown in FIG. 2 (Example 1), FIG. 3 (Example 2), FIG. 4 (Comparative Example 1), and FIG. 5 (Comparative Example 2), respectively. Referring to FIG. 2 and FIG. 3, it can be confirmed that the positive electrode active materials of Examples 1 and 2 are in the form of single particles.

[0210] Using an image in which the boundaries of the above primary particles are divided and displayed in random colors, the area of ​​each primary particle is calculated through the number of pixels corresponding to each of n primary particles (an average of 50,000 or more primary particles), and the radius (r) of a circle having the same area as the area of ​​each of the above primary particles i ) to determine the particle diameter (D) of each primary particle present in the SEM image. i =2r i ) and volume (V i =4 / 3×πr i 3 ) is calculated, and the product of the calculated volume and particle diameter for each primary particle is calculated (V i D i ) is the total volume (V) calculated i) is divided by the total sum of the primary particles to derive the volume average particle diameter of the primary particles, and the total sum of the derived particle diameters is divided by the number of primary particles to derive the number average particle diameter of the primary particles. Then, the PDI value is obtained according to Equation 1 described in this specification, and this is shown in Table 1 below.

[0211]

[0212] Experimental Example 2: Analysis of Positive Electrode Active Material (2)

[0213] After taking 0.01 g of each positive electrode active material (powder) manufactured in the examples and comparative examples, put it in a vial containing 30 ml of ultrapure water and 500 μl of dispersant, disperse the positive electrode active material with a sonicator for 1 minute, and then put it in a PSA (Microtrac, S3500) and analyze it, D 50 , and this is shown in Table 1 below.

[0214] At this time, D 50 refers to the particle size at the 50% point of the cumulative volume distribution according to particle size.

[0215]

[0216] Experimental Example 3: Evaluation of Differentiation Amount

[0217] Each of the positive electrode active materials (powder) manufactured in the examples and comparative examples was taken in an amount of 3 g, placed in a mold with an inner diameter of 13 mm, and pressurized at 9 tons for 1 minute. The number of particles with a particle diameter of less than 1 μm was confirmed using PSA (Microtrac, S3500). Then, the ratio of the number of particles with a particle diameter of less than 1 μm to the total number of particles (hereinafter referred to as the amount of fine particles generated) was calculated and shown in Table 1 below.

[0218]

[0219] Average volume diameter of primary particles (㎛) Average number diameter of primary particles (㎛) D measured by PDIPSA 50(㎛) Fine powder generation amount (%) Example 12.3471.3931.6854.201.11 Example 22.5781.5771.6354.390.42 Comparative example 12.0241.0821.8713.862.76 Comparative example 22.0621.0262.0114.214.39

[0220] Referring to Table 1 above, it can be confirmed that the positive electrode active materials of Examples 1 and 2 have a PDI value close to 1, indicating that the primary particle size is more uniform than that of the positive electrode active materials of Comparative Examples 1 and 2. In addition, it can be confirmed that the positive electrode active materials of Examples 1 and 2 also have a low amount of fine particles generated.

[0221] In the cathode active materials of Comparative Examples 1 and 2, the primary particles grow before the lithium melts and spreads evenly, so some particles grow excessively due to excessive lithium intake, and some particles grow small due to insufficient lithium intake, so it is expected that uneven growth occurred.

[0222]

[0223] Experimental Example 4: Battery Performance Evaluation

[0224] (1) Evaluation of volume change rate

[0225] Each of the positive electrode active materials, carbon black conductive agent, and polyvinylidene fluoride (PVDF) binder manufactured in Examples and Comparative Examples was mixed in a weight ratio of 95:2:3 in an N-methylpyrrolidone (NMP) solvent to manufacture a positive electrode slurry. The positive electrode slurry was applied to one surface of an aluminum current collector, dried at 130°C, and rolled to manufacture a positive electrode.

[0226] A negative electrode slurry was prepared by mixing a negative electrode active material consisting of natural graphite and artificial graphite in a weight ratio of 5:5, a Super C conductive agent, a binder (ZEON, BML302), and an additive (Daicel, DAICEL2200) in water in a weight ratio of 95.6:1.0:2.3:1.1. The negative electrode slurry was applied to one surface of a copper current collector, dried at 130°C, and rolled to prepare a negative electrode.

[0227] An electrode assembly was manufactured by interposing a porous polyethylene separator between the positive and negative electrodes manufactured above, laminating at 80°C to properly bond the electrodes, welding the aluminum and nickel tabs, placing the assembly in an aluminum pouch, and injecting an electrolyte into the pouch to manufacture a monocell. At this time, the electrolyte used was an electrolyte in which 0.7 M LiPF6 was dissolved in an organic solvent containing ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a volume ratio of 3:7.

[0228] For each monocell manufactured as described above, a charge formation was performed for 3 hours at a constant current of 0.1 C at 25℃, then one side of the pouch was opened, vacuum degassing was performed, and resealing was performed. Thereafter, charge and discharge were repeated 3 times at a constant current of 0.33 C, and then charging was performed at a constant current of 0.33 C. The charged monocell was opened, the negative electrode was separated, and the positive electrode and separator were alternately stacked two by two, placed in an aluminum pouch, and an electrolyte was injected into the pouch to manufacture a cell for volume measurement. At this time, the electrolyte used was an electrolyte in which 0.7 M LiPF6 was dissolved in an organic solvent of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a volume ratio of 3:7.

[0229] After measuring the initial volume of the above volume measuring cell, the above volume measuring cell was stored in an oven at 60°C for 8 weeks, and the cell volume after 8 weeks was measured. The volume change rate ([(initial volume) - (cell volume after 8 weeks)] / (initial volume) × 100) was calculated, and the results are shown in Table 2 below.

[0230]

[0231] (2) Capacity maintenance rate evaluation

[0232] Each of the positive electrode active materials, carbon black conductive agent, and polyvinylidene fluoride (PVDF) binder manufactured in Examples and Comparative Examples was mixed in a ratio of 95:2:3 in an N-methylpyrrolidone (NMP) solvent to manufacture a positive electrode slurry. The positive electrode slurry was applied to one surface of an aluminum current collector, dried at 130°C, and rolled to manufacture a positive electrode.

[0233] A lithium metal electrode was used as the negative electrode, and a porous polyethylene separator was interposed between the positive and negative electrodes to manufacture an electrode assembly. The electrode assembly was placed inside a battery case, and an electrolyte was injected into the case to manufacture a half-cell. At this time, the electrolyte was prepared by dissolving 1.0 M LiPF6 in an organic solvent containing ethylene carbonate (EC): ethyl methyl carbonate (EMC): dimethyl carbonate (DMC) in a volume ratio of 3:3:4.

[0234] For each half cell manufactured as described above, a cycle of charging (0.5C) to 4.45 V at 45°C using the CC-CV method, and then discharging (1C) to 2.5 V using the CC method was counted as one cycle, and a total of 50 cycles were repeated to measure the capacity of the lithium secondary battery. The percentage of the 50th cycle discharge capacity to the 1st cycle discharge capacity was defined as the capacity retention rate, and this is shown in Table 2 below.

[0235]

[0236] Volume change rate (%) (@ 8 weeks high temperature storage) Capacity retention rate (%) (@ 50 cycles) Example 122.4693.1 Example 222.8092.9 Comparative example 124.5491.2 Comparative example 226.3089.4

[0237] Referring to Tables 1 and 2 above, it can be confirmed that the positive electrode active materials of Examples 1 and 2 have a PDI value close to 1.0 and a small amount of fine particles generated, and thus, in the case of a battery including them, the volume change rate due to gas generation is reduced and the capacity retention rate is increased compared to the battery including the positive electrode active materials of Comparative Examples 1 and 2.

[0238] As a result, according to the method for manufacturing a positive electrode active material of the present invention, when a mixture including a positive electrode active material precursor and a lithium-containing raw material is first fired at 600°C to 900°C, and then continuously heated to 920°C to 1000°C and then secondarily fired at 920°C to 1000°C, it can be seen that a positive electrode active material in the form of single particles with uniform primary particle diameters is produced and that there is little fine dust. In addition, it can be seen that the positive electrode active material according to the present invention includes a lithium nickel cobalt manganese oxide in the form of single particles having a nickel content of 50 mol% or more among the total transition metals, and satisfies a PDI value of 1 to 1.8, so that both the high-temperature stability and life performance of a lithium secondary battery can be improved.

Claims

1. Contains lithium nickel cobalt manganese oxide in the form of a single particle consisting of 10 or fewer primary particles, with a nickel content of 50 mol% or more among all transition metals; A cathode active material having a polydispersity index (PDI) value of 1 to 1.8 according to the following equation 1: [Formula 1] PDI = .

2. In claim 1, The above lithium nickel cobalt manganese oxide is a positive electrode active material having a composition represented by the following chemical formula 1: [Chemical Formula 1] Li 1+x Ni a1 Co b1 Mr c1 M 1 d1 O2 In the above chemical formula 1, 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, -0.1≤x≤0.1, 0.5≤a1<1, 0 <b1<0.5, 0<c1<0.5, 0≤d1≤0.2, a1+b1+c1+d1=1이다.

3. In claim 1, A positive electrode active material having an average volume particle size of the primary particles of 0.5 ㎛ to 3.5 ㎛.

4. In claim 1, A positive electrode active material having an average particle size of the primary particles of 0.5 ㎛ to 2.0 ㎛.

5. In claim 1, The above positive electrode active material has a D measured by PSA (particle size analyzer) 50 This positive electrode active material is 3㎛ to 5㎛.

6. In claim 1, A cathode active material in which 3 g of the above cathode active material is placed in a mold with an inner diameter of 13 mm and pressurized at 9 tons for 1 minute, and the ratio of particles having a particle size of less than 1 ㎛ as measured by a PSA (particle size analyzer) to the total number of particles is 2.5% or less. 7.(A) A step of preparing a mixture by mixing a nickel-cobalt-manganese hydroxide having a nickel content of 50 mol% or more among all transition metals and a lithium-containing raw material; and (B) A method for producing a cathode active material according to claim 1, comprising the steps of first firing the mixture at 600°C to 900°C in an air atmosphere, then continuously raising the temperature to 920°C to 1000°C, and second firing at 920°C to 1000°C to produce a fired product.

8. In claim 7, A method for manufacturing a positive electrode active material, wherein the above nickel-cobalt-manganese hydroxide has a composition represented by the following chemical formula 2: [Chemical Formula 2] Ni a2 What b2 Mn c2 M 2 d2 (OH)2 In the above chemical formula 2, 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, 0.5≤a2<1, 0 <b2<0.5, 0<c2<0.5, 0≤d2≤0.2, a2+b2+c2+d2=1이다.

9. In claim 7, A method for manufacturing a positive electrode active material, wherein the above first firing is performed for 2 to 12 hours.

10. In claim 7, A method for manufacturing a positive electrode active material, wherein the above secondary firing is performed for 4 to 14 hours.

11. In claim 7, (C) A method for producing a positive electrode active material, further comprising a step of pulverizing the above-mentioned product.

12. In claim 11, A method for producing a positive electrode active material, wherein the above-mentioned fine grinding is performed by air-flow grinding.

13. In claim 12, A method for producing a positive electrode active material, wherein the above-mentioned airflow grinding is performed under a pressure of 1 bar to 5 bar.

14. A positive electrode comprising a positive electrode active material according to any one of claims 1 to 6.

15. The anode according to claim 14; cathode; a separator interposed between the anode and the cathode; and A lithium secondary battery comprising an electrolyte.

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