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

Abstract

The present invention relates to a positive electrode active material, which comprises a lithium transition metal composite oxide in the form of a single particle containing nickel, cobalt, and manganese, and the lithium transition metal composite oxide contains nickel in an amount of 60 mol % or more of the total transition metals, and D 50 The present invention relates to a positive electrode active material having a particle size of 5 μm or more, a positive electrode containing the same, and a lithium secondary battery.

Description

[Technical Field]

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2022-0113918, filed September 8, 2022, and all contents disclosed in the documents of this Korean patent application are incorporated herein by reference.

[0002] The present invention relates to a positive electrode active material, a positive electrode containing the same, and a lithium secondary battery. [Background technology]

[0003] Recently, with the development of technologies such as electric vehicles, the demand for high-capacity secondary batteries is increasing, and accordingly, research into high-nickel (High Ni) positive electrode active materials with excellent capacity characteristics is being actively conducted.

[0004] High-nickel cathode active materials, which are formed as secondary particles formed by the aggregation of primary particles, undergo structural degradation during charging and discharging of lithium secondary batteries, but also undergo a relative change in lattice structural constant, i.e., a large volume change within the unit lattice. Such volume change can cause cracks in the cathode active material. Furthermore, pressure applied during electrode rolling can also cause cracks in the cathode active material.

[0005] The cracks that occur in the high-nickel positive electrode active material become worse during the charging and discharging process of the lithium secondary battery, which acts as a void that prevents the electrolyte from reaching or reduces conductivity, thereby reducing the life characteristics of the lithium secondary battery or causing an increase in resistance.

[0006] To minimize cracking in the secondary particle structure, attempts have been made to prepare a single-particle cathode active material. Conventionally, single-particle cathode active materials have been prepared by first mixing a transition metal hydroxide prepared by coprecipitation with a lithium compound, followed by calcination to produce expanded secondary particles, which are then pulverized into single particles. However, preparing a single-particle cathode active material in this manner can result in non-uniform particle sizes of the primary particles constituting the secondary particles, resulting in a wide particle size distribution for the single-particle cathode active material obtained after pulverization. However, controlling the particle size distribution and average particle size of the cathode active material is crucial because the particle size distribution of the cathode active material significantly affects the performance and electrode design of lithium secondary batteries. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] KR10-1785262 B1 [Patent Document 2] KR10-2017-0119573 A Summary of the Invention [Problem to be solved by the invention]

[0008] The present invention has been devised to solve the above-mentioned problems of the prior art, and aims to provide a positive electrode active material in a single particle form, which has a negative skewness and a controlled average particle size.

[0009] Another object of the present invention is to provide a positive electrode and a lithium secondary battery that contain the positive electrode active material in the form of single particles, thereby improving the rolling density during the production of the positive electrode. [Means for solving the problem]

[0010] In order to solve the above problems, the present invention provides a method for producing a positive electrode active material, a positive electrode active material produced thereby, and a positive electrode and a lithium secondary battery including the same.

[0011] (1) The present invention provides a lithium transition metal composite oxide in the form of a single particle containing nickel, cobalt, and manganese, the lithium transition metal composite oxide containing nickel in an amount of 60 mol % or more of the total transition metals, and D 50 When the powder is formed into pellets by applying a force equivalent to 9,000 kgf using an automatic pellet press, the rolling density calculated by the following mathematical formula 3 is 3.56 g / cm 3 The positive electrode active material described above is provided. [Mathematical formula 3] Rolling density (g / cm 3 ) = Weight of positive electrode active material (g) / Volume of pellet (cm 3 )

[0012] (2) The present invention provides a positive electrode active material according to (1) above, wherein the lithium transition metal composite oxide in the form of a single particle is a secondary particle formed by agglomerating a single particle or 10 or less primary particles.

[0013] (3) The present invention provides a positive electrode active material according to the above (1) or (2), wherein the lithium transition metal composite oxide has an average composition represented by the following chemical formula 1: [Chemical formula 1] Li x Ni a Co b Mn c M 1 d O2 In the above Chemical Formula 1, M 1 is one or more selected from the group consisting of Al, Zr, B, W, Mo, Cr, Nb, Mg, Hf, Ta, La, Ti, Sr, Ba, Ce, F, P, S and Y, and 0.9≦x≦1.3, 0.6≦a<1.0, 0 <b<0.4、0<c<0.4、0≦d≦0.2、a+b+c+d=1である。

[0014] (4) The present invention provides the positive electrode active material according to (3) above, wherein X is 0.9 or more and 1.1 or less.

[0015] (5) The present invention provides the method according to any one of (1) to (4), 50 The present invention provides a positive electrode active material having a particle size of 5 μm or more and 9 μm or less.

[0016] (6) The present invention is directed to any one of the above (1) to (5), wherein the rolling density is 3.56 g / cm 3 More than 3.80g / cm 3 The following positive electrode active material is provided:

[0017] (7) In any one of the above (1) to (6), the present invention is characterized in that the mode in the volume cumulative distribution of particle diameter is D 50 To provide a larger positive electrode active material.

[0018] (8) The present invention provides a positive electrode active material according to (7), in which a negative skewness value calculated by the following mathematical formula 1 is greater than 0: [Mathematical formula 1] Negative skewness = (Mode-D 10 ) / D 50

[0019] (9) The present invention provides the positive electrode active material according to (8) above, wherein the negative skewness value is 0.40 or more and 0.75 or less.

[0020] (10) The present invention provides a positive electrode containing the positive electrode active material according to any one of (1) to (9) above.

[0021] (11) The present invention provides a lithium secondary battery comprising the positive electrode according to (10) above; a negative electrode; a separator interposed between the positive electrode and the negative electrode; and an electrolyte. [Effects of the Invention]

[0022] The cathode active material of the present invention is in the form of a single particle, has a negative skewness, and has a controlled average particle size. When a cathode is manufactured using the cathode active material, the rolling density is improved, and the energy density of the lithium secondary battery can be increased, thereby improving the capacity characteristics. [Brief explanation of the drawings]

[0023] [Figure 1] 1 is a graph showing cumulative volume distributions according to particle diameters of positive electrode active materials prepared in Examples and Comparative Examples of the present invention; [Figure 2] 1 is an image of the positive electrode active material prepared in Example 1 of the present invention, taken with a scanning electron microscope. [Figure 3] 1 is an image of the positive electrode active material prepared in Example 2 of the present invention, taken by a scanning electron microscope. [Figure 4] 1 is an image of a positive electrode active material prepared in Example 3 of the present invention, taken with a scanning electron microscope. [Figure 5] 1 is an image of the positive electrode active material prepared in Example 4 of the present invention, taken with a scanning electron microscope. [Figure 6] 1 is an image of a positive electrode active material prepared in Example 5 of the present invention, taken by a scanning electron microscope. [Figure 7] 1 is an image of a positive electrode active material prepared in Example 6 of the present invention, taken by a scanning electron microscope. [Figure 8] 1 is an image of a cathode active material prepared in Example 7 of the present invention, taken by a scanning electron microscope. [Figure 9] 1 is an image of a positive electrode active material prepared in Comparative Example 1 of the present invention, taken with a scanning electron microscope. [Figure 10] 1 is an image of a positive electrode active material prepared in Comparative Example 2 of the present invention, taken with a scanning electron microscope. [Figure 11] 1 is an image of a positive electrode active material prepared in Comparative Example 3 of the present invention, taken with a scanning electron microscope. [Figure 12] 1 is an image of a positive electrode active material prepared in Comparative Example 4 of the present invention, taken with a scanning electron microscope. DETAILED DESCRIPTION OF THE INVENTION

[0024] The present invention will now be described in more detail to facilitate understanding of the present invention.

[0025] The terms and words used in the description and claims of the present invention should not be interpreted in a limited way to their ordinary or dictionary meanings, but should be interpreted in a way that is consistent with the technical idea of ​​the present invention, based on the principle that inventors can appropriately define the concepts of terms in order to best describe their inventions.

[0026] In the present invention, the term "primary particle" means the smallest particle unit that can be distinguished as a single mass when a cross section of a positive electrode active material is observed through a scanning electron microscope (SEM), and may consist of multiple crystal grains.

[0027] In the present invention, the term "secondary particles" refers to secondary structures formed by aggregation of more than 10 primary particles. The average particle size of the secondary particles can be measured using a particle size analyzer.

[0028] In the present invention, the term "D 10 "," "D 50 " and "D 90 " and " are the 10% points of the volume cumulative distribution by particle size (D 10 ), 50% point (D 50 ) and 90% point (D 90 ) means the particle size at 10 , D 50 and D 90 The D is calculated by dispersing the powder to be measured in a dispersion medium, introducing it into a commercially available laser diffraction particle size measuring device (e.g., Malvern's Mastersizer 3000), measuring the difference in diffraction pattern depending on the particle size when the particles pass through the laser beam, and calculating the volume cumulative distribution by particle size. The particle diameters at the points of 10%, 50%, and 90% of the volume cumulative distribution by particle size in the measuring device are then calculated. 10 , D 50 and D 90 In the present invention, the D 50 can be expressed in terms of average particle size.

[0029] In the present invention, the term "single particle form" refers to both positive electrode active material and / or lithium transition metal composite oxide particles in the form of a single particle and particles in the form of an aggregation of 2 to 10 particles. That is, the positive electrode active material and / or lithium transition metal composite oxide in the form of a single particle of the present invention may include one or more types of positive electrode active material and / or lithium transition metal composite oxide particles selected from the group consisting of single particles and particles in the form of an aggregation of 2 to 10 particles.

[0030] positive electrode active material The present invention provides a positive electrode active material.

[0031] According to one embodiment of the present invention, the positive electrode active material includes a lithium transition metal composite oxide in the form of a single particle containing nickel, cobalt, and manganese, and the lithium transition metal composite oxide contains nickel in an amount of 60 mol % or more of the total transition metals, and D 50 When the powder is formed into pellets by applying a force equivalent to 9,000 kgf using an automatic pellet press, the rolling density calculated by the following mathematical formula 3 is 3.56 g / cm 3 It can be more than that.

[0032] [Mathematical formula 3] Rolling density (g / cm 3 ) = Weight of positive electrode active material (g) / Volume of pellet (cm 3 )

[0033] According to one embodiment of the present invention, the positive electrode active material may include a lithium transition metal composite oxide in a single particle form. Specifically, the single particle lithium transition metal composite oxide may be a single particle or a secondary particle formed by agglomeration of 10 or fewer primary particles. Conventional positive electrode active materials in the form of secondary particles formed by agglomeration of more than 10 primary particles require increased porosity to minimize cracks caused by pressure during rolling to fabricate an electrode, which ultimately reduces the energy density of the lithium secondary battery. However, the positive electrode active material of the present invention, which has the form of a single particle or a secondary particle formed by agglomeration of 10 or fewer primary particles, can minimize cracks caused by volume changes within the unit cell during charge and discharge of a lithium secondary battery, and in particular, can minimize cracks caused by pressure during rolling to fabricate an electrode. Therefore, when using the positive electrode active material of the present invention, rolling to fabricate an electrode can be performed with a lower porosity, thereby improving the energy density of the lithium secondary battery.

[0034] According to one embodiment of the present invention, the lithium transition metal composite oxide may be a high-nickel lithium transition metal composite oxide containing nickel, with the nickel (Ni) content being 60 mol% or more relative to the total transition metals. In this case, the high nickel content can ensure high energy density.

[0035] According to one embodiment of the present invention, the lithium transition metal composite oxide may have an average composition represented by the following Chemical Formula 1:

[0036] [Chemical formula 1] Li x Ni a Co b Mn c M 1 d O2

[0037] In the above Chemical Formula 1, M 1is one or more selected from the group consisting of Al, Zr, B, W, Mo, Cr, Nb, Mg, Hf, Ta, La, Ti, Sr, Ba, Ce, F, P, S and Y, and 0.9≦x≦1.3, 0.6≦a<1.0, 0 <b<0.4、0<c<0.4、0≦d≦0.2、a+b+c+d=1である。

[0038] According to one embodiment of the present invention, in Formula 1, M 1 is a doping element that can be contained in the lithium transition metal composite oxide, and can be appropriately selected as needed.

[0039] According to one embodiment of the present invention, in Formula 1, x represents a molar ratio of lithium to transition metal in the lithium transition metal composite oxide, and may be 0.9 or more, 0.95 or more, or 1.0 or more, and may be 1.1 or less, 1.07 or less, 1.05 or less, or 1.03 or less.

[0040] According to one embodiment of the present invention, in Formula 1, a, b, c, and d represent nickel (Ni), cobalt (Co), manganese (Mn), and a doping element (Mn), respectively, among transition metals. 1)). As a specific example, a is the molar fraction of nickel (Ni) among the transition metals, and may be 0.6 or more, 0.7 or more, 0.8 or more, 0.85 or more, 0.88 or more, 0.90 or more, 0.91 or more, 0.92 or more, 0.93 or more, 0.94 or more, 0.95 or more, or 0.96 or more, and may be less than 1.0, 0.99 or less, 0.98 or less, 0.97 or less, or 0.96 or less. Furthermore, b is the molar fraction of cobalt (Co) among the transition metals, and may be greater than 0, 0.01 or more, 0.02 or more, or 0.03 or more, and may be less than 0.4, 0.3 or less, 0.2 or less, 0.1 or less, 0.09 or less, 0.08 or less, 0.07 or less, 0.06 or less, or 0.05 or less. The c is a molar fraction of manganese (Mn) among the transition metals, and may be greater than 0, 0.01 or greater, or 0.05 or greater, and may be less than 0.4, 0.3 or less, 0.2 or less, 0.1 or less, 0.09 or less, 0.08 or less, 0.07 or less, 0.06 or less, or 0.05 or less. The d is a molar fraction of manganese (Mn) among the transition metals. 1 ), and can be 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, or 0.19 or more. and can be less than 0.20, 0.19 or less, 0.18 or less, 0.17 or less, 0.16 or less, 0.15 or less, 0.14 or less, 0.13 or less, 0.12 or less, 0.11 or less, 0.10 or less, 0.09 or less, 0.08 or less, 0.07 or less, 0.06 or less, 0.05 or less, 0.04 or less, 0.03 or less, 0.02 or less, or 0.01 or less.

[0041] According to one embodiment of the present invention, the positive electrode active material is D 50In the past, when manufacturing a single particle type positive electrode active material, a hydroxide type precursor was mixed with a lithium compound, and the mixture was over-fired to produce expanded secondary particles, which were then pulverized to manufacture a single particle type positive electrode active material. 50 is manufactured into a single particle type positive electrode active material with small particles of 1 μm to 4 μm level, and the D of the single particle type positive electrode active material 50 However, the positive electrode active material according to the present invention is produced by the method for producing a positive electrode active material described below, has a single particle form, and has a D 50 The positive electrode active material of the present invention is in a single particle form and has a diameter of 5 μm or more. 50 Since the diameter is 5 μm or more, the occurrence of cracks in the positive electrode active material can be further minimized, and the rolling density can be improved. 50 This is more advantageous than a positive electrode active material in a single particle form, in which the particle size is small, at a level of 1 μm to 4 μm. 50 As a specific example, the positive electrode active material is characterized in that D 50 may be 5 μm or more, 5.1 μm or more, 5.2 μm or more, 5.3 μm or more, 5.4 μm or more, 5.5 μm or more, 5.6 μm or more, 5.7 μm or more, 5.8 μm or more, 5.9 μm or more, 6.0 μm or more, 6.1 μm or more, 6.2 μm or more, 6.3 μm or more, 6.4 μm or more, 6.5 μm or more, 6.6 μm or more, 6.7 μm or more, 6.8 μm or more, 6.9 μm or more, or 7.0 μm or more. 50 D 50 can be 9 μm or less, 8.9 μm or less, 8.8 μm or less, 8.7 μm or less, 8.6 μm or less, 8.5 μm or less, 8.4 μm or less, 8.3 μm or less, 8.2 μm or less, 8.1 μm or less, 8.0 μm or less, 7.9 μm or less, 7.8 μm or less, 7.7 μm or less, 7.6 μm or less, 7.5 μm or less, 7.4 μm or less, 7.3 μm or less, 7.2 μm or less, 7.1 μm or less, 7.0 μm or less, or 6.5 μm or less, and the present invention relates to the above-mentioned D 50In order to distinguish the positive electrode active material having the above structure from the positive electrode active material having small particles and the positive electrode active material having large particles, the positive electrode active material having the above structure can be referred to as a positive electrode active material having medium-sized single particles.

[0042] According to one embodiment of the present invention, the positive electrode active material has a rolling density of 3.56 g / cm when formed into pellets by applying a force corresponding to 9,000 kgf using an automatic pellet press, as calculated by Equation 3. 3 In this case, when the positive electrode active material is used alone or mixed with a small particle or large particle positive electrode active material to form a positive electrode, the occurrence of cracks due to rolling can be minimized and the porosity of the positive electrode can be further reduced, thereby allowing a larger amount of positive electrode active material to be contained in the same volume of positive electrode active material layer, thereby further improving the energy density of the lithium secondary battery.

[0043] According to one embodiment of the present invention, the positive electrode active material has a rolling density of 3.56 g / cm 3 This is the minimum standard for achieving the effects of the present invention, and the rolling density must be 3.56 g / cm or more. 3 As a specific example, the positive electrode active material has a rolling density of 3.57 g / cm. 3 More than 3.58g / cm 3 Above, 3.59g / cm 3 More than 3.60g / cm 3 More than 3.61g / cm 3 More than 3.62g / cm 3 More than 3.63g / cm 3 More than 3.64g / cm 3 More than 3.65g / cm 3 More than 3.66g / cm 3 or more, or 3.67 g / cm 3 Within this range, the rolling density during the preparation of the positive electrode is significantly improved, the energy density of the lithium secondary battery is increased, and the capacity characteristics are further improved. 3 Below, 3.75g / cm3 Below, 3.74g / cm 3 Below, 3.73g / cm 3 or less than 3.72 g / cm 3 It can be:

[0044] According to one embodiment of the present invention, the positive electrode active material has the nickel content, D 50 In addition to the rolling density, the volume cumulative distribution of the particle diameter of the positive electrode active material particles may be adjusted. For example, the positive electrode active material may have a volume cumulative distribution of the particle diameter of the positive electrode active material particles having a mode of D 50 It can be bigger.

[0045] In a positive electrode active material that is an aggregate of a plurality of particles forming a volume cumulative distribution according to particle size, as in the positive electrode active material of the present invention, the mode (Mode) in the volume cumulative distribution according to particle size is D 50 If the D is larger, the content of fine powder with a relatively small particle size is high, so when a positive electrode active material layer is formed using the positive electrode active material, the gaps between the positive electrode active material particles can be minimized, and thus a larger content of positive electrode active material particles can be contained within the same volume, ensuring a higher energy density. 50 Even if the positive electrode active material has a particle size, the mode and D 50 Since the energy density varies depending on the particle size, it is important to adjust this. The positive electrode active material of the present invention has a mode of D in the volume cumulative distribution of particle size. 50 By adjusting the nickel content, D 50 In addition to the rolling density, the energy density of the lithium secondary battery can be further improved.

[0046] According to an embodiment of the present invention, the positive electrode active material may have a negative skewness value greater than 0, as calculated by the following Equation 1:

[0047] [Mathematical formula 1] Negative skewness = (Mode-D10 ) / D 50

[0048] Generally, skewness is a measure that statistically indicates the asymmetry of a specific distribution. A positive skewness value is called positive skewness, and a negative skewness value is called negative skewness. However, since the positive skewness and negative skewness shown by the conventional method are expressed as the cube of the deviation from the mean, the skewness value becomes larger depending on the bias of the skewness, and therefore, in the present invention, this is not suitable for determining the fine powder content of the positive electrode active material. Therefore, in the present invention, negative skewness is newly defined and expressed by the above-mentioned Equation 1. According to Equation 1, the negative skewness in the present invention is expressed by D 50 Mode and D for 10 This is expressed as a ratio to the difference between D 50 Based on the standard, the mode and the fine powder region are 10 By comparing the difference between the values, it is possible to indirectly confirm the fine powder content of the positive electrode active material, which is an aggregate of a plurality of particles forming a volume cumulative distribution according to particle size.

[0049] According to an embodiment of the present invention, the positive electrode active material may have a negative skewness value calculated by Equation 1 above of greater than 0, 0.10 or more, 0.20 or more, 0.30 or more, 0.40 or more, or 0.45 or more, or may be 0.75 or less, 0.70 or less, 0.65 or less, 0.60 or less, 0.59 or less, 0.58 or less, 0.57 or less, 0.56 or less, or 0.55 or less. By appropriately adjusting the content of fine powder having a relatively small particle size within this range, cracks caused by pressure during rolling for electrode manufacture can be minimized, and the energy density of the lithium secondary battery can be maximized and capacity characteristics can be ensured.

[0050] According to one embodiment of the present invention, the positive electrode active material has a mode in a volume cumulative particle size distribution of 5.5 μm or more, 5.6 μm or more, 5.7 μm or more, 5.8 μm or more, 5.9 μm or more, 6.0 μm or more, 6.1 μm or more, 6.2 μm or more, 6.3 μm or more, 6.4 μm or more, 6.5 μm or more, 6.6 μm or more, 6.7 μm or more, 6.8 μm or more, 6.9 μm or more, 7.0 μm or more, 7.1 μm or more, 7.2 μm or more, 7.3 μm or more, 7.4 μm or more, or 7.5 μm or more. and can be 9.5 μm or less, 9.4 μm or less, 9.3 μm or less, 9.2 μm or less, 9.1 μm or less, 9.0 μm or less, 8.9 μm or less, 8.8 μm or less, 8.7 μm or less, 8.6 μm or less, 8.5 μm or less, 8.4 μm or less, 8.3 μm or less, 8.2 μm or less, 8.1 μm or less, 8.0 μm or less, 7.9 μm or less, 7.8 μm or less, 7.7 μm or less, 7.6 μm or less, 7.5 μm or less, or 7.0 μm or less, and within this range, the nickel content, D 50 In addition to the rolling density, the energy density of the lithium secondary battery can be further improved.

[0051] According to one embodiment of the present invention, the positive electrode active material has a volume cumulative distribution of particle size of D 10 The particle size may be 3.0 μm or more, 3.1 μm or more, 3.2 μm or more, 3.3 μm or more, 3.4 μm or more, or 3.5 μm or more, and may be 6.0 μm or less, 5.5 μm or less, or 5.0 μm or less. By adjusting the size of the fine powder within this range, the energy density of the lithium secondary battery can be further improved.

[0052] According to one embodiment of the present invention, the positive electrode active material has a mode and D 50 The difference between the nickel content and the average particle diameter may be 1.0 μm or less, 0.9 μm or less, 0.8 μm or less, 0.7 μm or less, 0.6 μm or less, or 0.5 μm or less, and may be 0.1 μm or more, 0.2 μm or more, 0.3 μm or more, or 0.4 μm or more, and within this range, the nickel content, D 50 In addition to the rolling density, the energy density of the lithium secondary battery can be further improved.

[0053] Method for producing positive electrode active material The present invention provides a method for producing the above-mentioned positive electrode active material.

[0054] According to one embodiment of the present invention, the method for preparing the cathode active material includes the steps of: (S10) mixing a cathode active material precursor containing nickel, cobalt, and manganese, with a lithium source material, and performing a primary firing to prepare a pre-fired product; and (S20) performing a secondary firing on the pre-fired product prepared in the step (S10) to prepare a lithium transition metal composite oxide in the form of a single particle. The secondary firing may be performed at a temperature lower than that of the primary firing. By performing the secondary firing at a temperature lower than that of the primary firing, D 50 is ≥ μm, and when a force equivalent to 9,000 kgf is applied to form pellets using an automatic pellet press, the rolling density calculated by Equation 3 is 3.56 g / cm 3 The positive electrode active material can be produced as described above.

[0055] According to one embodiment of the present invention, the temperature difference between the primary firing in step (S10) and the secondary firing in step (S20) may be 10°C or more, 20°C or more, 30°C or more, 40°C or more, or 50°C or more, and may be 300°C or less, 250°C or less, 200°C or less, 150°C or less, or 100°C or less. As a specific example, the primary firing in step (S10) may be performed at a temperature of 800°C to 1,000°C, and more specifically, the primary firing in step (S10) may be performed within a temperature range of 800°C to 1,000°C, 830°C to 950°C, or 850°C to 900°C. Furthermore, the secondary firing in step (S20) may be performed at a temperature of 600°C to 900°C, and more specifically, the secondary firing in step (S20) may be performed within a temperature range of 600°C to 900°C, 650°C to 850°C, or 700°C to 800°C.

[0056] According to one embodiment of the present invention, the calcined product manufactured by the primary firing in the step (S10) may have particles aggregated with each other, and the secondary firing in the step (S20) can be performed on the calcined product manufactured in the step (S10) after pulverization.

[0057] According to one embodiment of the present invention, the cathode active material precursor containing nickel, cobalt and manganese and containing 60 mol% or more of nickel among transition metals can be a transition metal hydroxide or a transition metal oxide. As a specific example, the transition metal hydroxide can have an average composition represented by the following Chemical Formula 2, and the transition metal oxide can have an average composition represented by the following Chemical Formula 3.

[0058] [Chemical Formula 2] Ni a’ Co b’ Mn c’ (OH)2

[0059] [Chemical Formula 3] Ni a’’ Co b’’ Mn c’’ O

[0060] In Chemical Formula 2, 0.6 ≦ a' < 1.0, 0 < b' < 0.4, 0 < c' < 0.4, and a' + b' + c' = 1. In Chemical Formula 3, 0.6 ≦ a'' < 1.0, 0 < b'' < 0.4, 0 < c'' < 0.4, and a'' + b'' + c'' = 1.

[0061] According to one embodiment of the present invention, in Chemical Formulas 2 and 3, a', a'', b', b'', c', and c'' may be the molar fractions of nickel (Ni), cobalt (Co), and manganese (Mn) among the transition metals, respectively. Specific examples of a' or a'' are the molar fractions of nickel (Ni) among the transition metals, and may be 0.6 or more, 0.7 or more, 0.8 or more, 0.85 or more, 0.88 or more, 0.90 or more, 0.91 or more, 0.92 or more, 0.93 or more, 0.94 or more, 0.95 or more, or 0.96 or more, or may be less than 1.0, 0.99 or less, 0.98 or less, 0.97 or less, or 0.96 or less. Furthermore, b' or b'' is the molar fraction relative to cobalt (Co) among the transition metals, and may be greater than 0, 0.01 or greater, 0.02 or greater, or 0.03 or greater, and may be less than 0.4, 0.3 or less, 0.2 or less, 0.1 or less, 0.09 or less, 0.08 or less, 0.07 or less, 0.06 or less, or 0.05 or less. c' or c'' is the molar fraction relative to manganese (Mn) among the transition metals, and may be greater than 0, 0.01 or greater, or 0.05 or greater, and may be less than 0.4, 0.3 or less, 0.2 or less, 0.1 or less, 0.09 or less, 0.08 or less, 0.07 or less, 0.06 or less, or 0.05 or less.

[0062] According to one embodiment of the present invention, the transition metal oxide may be prepared by calcining the transition metal hydroxide. Specifically, the transition metal oxide may be prepared by calcining a transition metal hydroxide containing nickel, cobalt, and manganese, with nickel at 60 mol % or more of the transition metals, in air or an oxygen atmosphere (S1). The calcination in step (S1) may be performed at a temperature of 800°C or higher, specifically, 800°C or higher, 850°C or higher, 900°C or higher, 950°C or higher, or 1,000°C or higher, or at a temperature of 1,200°C or lower, 1,150°C or lower, 1,100°C or lower, or 1,050°C or lower.

[0063] According to one embodiment of the present invention, the positive electrode active material precursor containing nickel, cobalt, and manganese, and containing nickel at 60 mol % or more among the transition metals, is more preferably a transition metal oxide, from the viewpoint of ensuring a higher rolling density than the medium-sized single particle positive electrode active material according to the present invention.

[0064] According to an embodiment of the present invention, step (S1) may include step (S1-1) of mixing a transition metal hydroxide with a doping source material, and step (S1-2) of firing the mixture obtained in step (S1-1) under air or an oxygen atmosphere to prepare a transition metal oxide, wherein the doping source material may include one or more doping elements selected from the group consisting of Li, Al, Zr, B, W, Mo, Cr, Nb, Mg, Hf, Ta, La, Ti, Sr, Ba, Ce, F, P, S, and Y.

[0065] According to one embodiment of the present invention, when mixing the positive electrode active material precursor and the lithium source material in step (S10), the molar ratio (Li / M) of the lithium (Li) in the lithium source material to the transition metal (M) in the positive electrode active material precursor may be 0.9 or more and 1.3 or less. Specific examples of the Li / M ratio include 0.9 or more, 0.95 or more, or 1.0 or more, and 1.1 or less, 1.07 or less, 1.05 or less, or 1.03 or less, and the Li / M ratio may be adjusted depending on the nickel content in the transition metal.

[0066] positive electrode The present invention provides a positive electrode containing the positive electrode active material.

[0067] According to an embodiment of the present invention, 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.

[0068] According to one embodiment of the present invention, the positive electrode current collector may include a highly conductive metal, and is not particularly limited as long as it is easily adhered to the positive electrode active material layer and is non-reactive within the voltage range of the battery. Examples of the positive electrode current collector include stainless steel, aluminum, nickel, titanium, calcined carbon, and aluminum or stainless steel whose surfaces are surface-treated with carbon, nickel, titanium, silver, etc. The positive electrode current collector typically has a thickness of 3 μm to 500 μm, and the surface of the current collector may be micro-irregularized to enhance adhesion of the positive electrode active material. The positive electrode current collector may be used in various forms, such as a film, sheet, foil, mesh, porous material, foam, or nonwoven fabric.

[0069] According to one embodiment of the present invention, the positive electrode active material layer may optionally contain a conductive material and a binder in addition to the positive electrode active material. Here, the positive electrode active material may be contained 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. Within this range, excellent capacity characteristics can be exhibited.

[0070] According to one embodiment of the present invention, the conductive material is used to impart conductivity to the electrode. Any conductive material can be used without particular limitations as long as it does not cause chemical changes in the resulting battery and has electronic conductivity. Specific examples include graphite, such as natural graphite or artificial graphite; carbon-based materials, such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black, and carbon fiber; metal powder or metal fiber, such as copper, nickel, aluminum, and silver; conductive tubes, such as carbon nanotubes; conductive whiskers, such as zinc oxide and potassium titanate; conductive metal oxides, such as titanium oxide; and conductive polymers, such as polyphenylene derivatives. These materials may be used alone or in combination. 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.

[0071] According to an embodiment of the present invention, the binder improves adhesion between positive electrode active material particles and between the positive electrode active material and the current collector. Specific examples of the binder include polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, 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), fluororubber, polyacrylic acid, polymers in which hydrogen is substituted with Li, Na, or Ca, or various copolymers thereof. These may be used alone or in combination. The binder may be contained in an amount of 0.1% by weight to 15% by weight based on the total weight of the positive electrode active material layer.

[0072] According to one embodiment of the present invention, the positive electrode can be manufactured by a conventional method for manufacturing a positive electrode, except for using the positive electrode active material. Specifically, the positive electrode can be manufactured by coating a positive electrode active material layer-forming composition, which is prepared by dissolving or dispersing the positive electrode active material and, optionally, a binder, a conductive material, and a dispersant in a solvent, on a positive electrode current collector, followed by drying and rolling, or by casting the positive electrode active material layer-forming composition on a separate support, peeling it from the support, and laminating the resulting film on a positive electrode current collector.

[0073] According to one embodiment of the present invention, the solvent may be a solvent commonly used in the art, such as dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), dimethylformamide (DMF), acetone, or water, and may be used alone or in combination. The amount of the solvent used may be sufficient to dissolve or disperse the cathode active material, conductive material, binder, and dispersant, taking into consideration the coating thickness of the slurry and the manufacturing yield, and to provide a viscosity that allows excellent thickness uniformity during subsequent coating for manufacturing a cathode.

[0074] Lithium secondary battery The present invention provides a lithium secondary battery including the positive electrode.

[0075] According to an embodiment of the present invention, the lithium secondary battery may include the positive electrode, the negative electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte. The lithium secondary battery may further include a battery container that houses the electrode assembly including the positive electrode, the negative electrode, and the separator, and a sealing member that seals the battery container.

[0076] According to an embodiment of the present invention, the negative electrode may include a negative electrode current collector and a negative electrode active material layer disposed on the negative electrode current collector.

[0077] According to one embodiment of the present invention, the negative electrode current collector may be made of any material that does not cause chemical changes in the battery and has high conductivity. Examples of such materials include copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surfaces that have been surface-treated with carbon, nickel, titanium, silver, or the like, and aluminum-cadmium alloys. The negative electrode current collector may typically have a thickness of 3 μm to 500 μm. Similar to the positive electrode current collector, the current collector may have a surface with fine irregularities to enhance the binding strength of the negative electrode active material. The negative electrode current collector may be made in various forms, such as a film, sheet, foil, mesh, porous material, foam, or nonwoven fabric.

[0078] According to an embodiment of the present invention, the negative electrode active material layer may optionally include a binder and a conductive material in addition to the negative electrode active material.

[0079] According to an embodiment of the present invention, the negative electrode active material may be a compound capable of reversible intercalation and deintercalation of lithium. Specific examples thereof include carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber, and amorphous carbon; metallic compounds capable of alloying with lithium such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloys, Sn alloys, and Al alloys; and SiO βExamples of the negative electrode active material include metal oxides capable of doping and dedoping lithium, such as SnO2, vanadium oxide, and lithium vanadium oxide (0<β<2); and composites containing the metallic compounds and carbonaceous materials, such as Si-C composites and Sn-C composites. These may be used alone or in combination. A thin film of metallic lithium may also be used as the negative electrode active material. The carbon material may be either low-crystalline carbon or high-crystalline carbon. Representative examples of low-crystalline carbon include soft carbon and hard carbon, while representative examples of high-crystalline carbon include amorphous, plate-like, flake-like, spherical, or fibrous natural or artificial graphite, Kish graphite, pyrolytic carbon, mesophase pitch-based carbon fiber, mesocarbon microbeads, mesophase pitches, and high-temperature-sintered 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% of the total weight of the negative electrode active material layer.

[0080] According to one embodiment of the present invention, the binder in the negative electrode active material layer is a component that helps bind the conductive material, active material, and current collector, and is typically added in an amount of 0.1 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.

[0081] According to one embodiment of the present invention, the conductive material in the 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 may be any conductive material that does not cause chemical changes in the battery and has conductivity. Examples of such conductive materials include graphite such as natural graphite and artificial graphite; carbon black such as acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal black; conductive fibers such as carbon fiber and metal fiber; carbon fluoride; metal powders such as aluminum and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives.

[0082] According to one embodiment of the present invention, the negative electrode may be manufactured by coating a negative electrode active material layer-forming composition, which is 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 and drying the coating. Alternatively, the negative electrode active material layer-forming composition may be cast on a separate support, peeled from the support, and the resulting film may be laminated on the negative electrode current collector.

[0083] According to one embodiment of the present invention, the separator separates the negative electrode and the positive electrode and provides a path for lithium ions to move. Any separator commonly used in lithium secondary batteries can be used without particular limitation. In particular, a separator with low resistance to electrolyte ion movement and excellent electrolyte humidification ability is preferred. Specifically, a porous polymer film, such as a porous polymer film made of a polyolefin-based polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, or an ethylene / methacrylate copolymer, or a laminate structure of two or more layers thereof can be used. Conventional porous nonwoven fabrics, such as nonwoven fabrics made of high-melting-point glass fibers or polyethylene terephthalate fibers, can also be used. To ensure heat resistance or mechanical strength, a separator coated with a ceramic component or a polymer material can also be used, and can be selectively used in a single-layer or multi-layer structure.

[0084] According to an embodiment of the present invention, the electrolyte may be, but is not limited to, an organic liquid electrolyte, an inorganic liquid electrolyte, a solid polymer electrolyte, a gel-type polymer electrolyte, a solid inorganic electrolyte, a molten inorganic electrolyte, etc., which can be used in manufacturing a lithium secondary battery. For example, the electrolyte may include an organic solvent and a lithium salt.

[0085] According to an embodiment of the present invention, the organic solvent may be any solvent capable of acting as a medium through which ions involved in the electrochemical reaction of the battery can migrate. Specifically, examples of the organic solvent include ester solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, and ε-caprolactone; ether solvents such as dibutyl ether and tetrahydrofuran; ketone solvents such as cyclohexanone; aromatic hydrocarbon solvents such as benzene and fluorobenzene; dimethylcarbonate (DMC), diethylcarbonate (DEC), methylethylcarbonate (MEC), ethylmethylcarbonate (EMC), ethylene carbonate (EC), and propylene carbonate. Examples of solvents that can be used include carbonate-based solvents such as ethylene carbonate (PC), alcohol-based solvents such as ethyl alcohol and isopropyl alcohol, nitriles such as R-CN (where R is a hydrocarbon group having 2 to 20 carbon atoms and having a linear, branched, or cyclic structure, and may contain a double-bonded aromatic ring or an ether bond), amides such as dimethylformamide, dioxolanes such as 1,3-dioxolane, and sulfolanes. Among these, carbonate-based solvents are preferred, and mixtures of cyclic carbonates (e.g., ethylene carbonate or propylene carbonate) with high ionic conductivity and a high dielectric constant, which can improve the charge / discharge performance of batteries, and low-viscosity linear carbonate compounds (e.g., ethyl methyl carbonate, dimethyl carbonate, or diethyl carbonate) are more preferred.

[0086] According to one embodiment of the present invention, the lithium salt may be any compound capable of providing lithium ions used in a lithium secondary battery. Specifically, the anion of the lithium salt may be 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 - The lithium salt may be at least one selected from the group consisting of: LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAlO4, 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 within the range of 0.1 to 2.0 M. When the lithium salt concentration is within this range, the electrolyte has appropriate conductivity and viscosity, thereby exhibiting excellent electrolyte performance and allowing lithium ions to migrate effectively.

[0087] According to one embodiment of the present invention, in addition to the electrolyte components, the electrolyte may further include one or more additives, such as haloalkylene carbonate compounds (e.g., difluoroethylene carbonate), pyridine, triethyl phosphite, triethyl alcohol amine, cyclic ethers, ethylenediamine, n-glyme, hexaphosphoric acid triamide, nitrobenzene derivatives, sulfur, quinoneimine dyes, N-substituted oxazolidinones, N,N-substituted imidazolidines, ethylene glycol dialkyl ethers, ammonium salts, pyrrole, 2-methoxyethyl alcohol, or aluminum trichloride, for the purpose of improving battery life characteristics, suppressing battery capacity reduction, and improving battery discharge capacity. Here, the additives may be included in an amount of 0.1 wt % to 5 wt % based on the total weight of the electrolyte.

[0088] A lithium secondary battery including the positive electrode active material according to the present invention stably exhibits excellent capacity characteristics, output characteristics, and life characteristics, and is therefore useful in portable devices such as mobile phones, notebook computers, and digital cameras, and in the field of electric vehicles such as hybrid electric vehicles (HEVs) and electric vehicles (EVs).

[0089] The external shape of the lithium secondary battery of the present invention is not particularly limited, and may be a cylindrical shape using a can, a square shape, a pouch shape, a coin shape, or the like.

[0090] 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 also as a unit battery for a medium- to large-sized battery module including a large number of battery cells.

[0091] Therefore, according to one embodiment of the present invention, there is provided a battery module including the lithium secondary battery as a unit cell, and a battery pack including the same.

[0092] According to one embodiment of the present invention, the battery module or battery pack may 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 an electric vehicle (PHEV), including a plug-in hybrid electric vehicle; or a power storage system.

[0093] While the present invention may be embodied in various different forms, it is to be understood that the invention is not limited to the specific embodiments set forth herein, and that the invention may be embodied in various different forms without departing from the spirit or scope of the present invention. [Example]

[0094] Examples and Comparative Examples Example 1 Ni 0.96 Co 0.03 Mn 0.01 Transition metal complex hydroxide (D 50 : 7μm) was baked at 1,020℃ for 9 hours in an air atmosphere to form Ni 0.96 Co 0.03 Mn 0.01 A transition metal composite oxide having a composition represented by the formula O was produced.

[0095] The prepared transition metal composite oxide and LiOH were mixed so that the molar ratio of lithium (Li) to transition metal (Me) (Li / Me) was 1, and the mixture was subjected to primary firing at 800°C for 12 hours in an oxygen atmosphere, followed by pulverization using a jet mill and secondary firing at 700°C for 12 hours in an oxygen atmosphere to obtain LiNi 0.96 Co 0.03 Mn 0.01 A positive electrode active material was prepared, which was a lithium transition metal composite oxide in the form of a single particle having a composition represented by O2.

[0096] Example 2 The same procedure as in Example 1 was carried out, except that the primary firing was carried out at 850°C instead of 800°C, to obtain LiNi 0.96 Co 0.03 Mn 0.01 A positive electrode active material was prepared, which was a lithium transition metal composite oxide in the form of a single particle having a composition represented by O2.

[0097] Example 3 The same procedure as in Example 1 was carried out, except that the secondary firing was carried out at 750°C instead of 700°C, to obtain LiNi 0.96 Co 0.03 Mn 0.01 A positive electrode active material was prepared, which was a lithium transition metal composite oxide in the form of a single particle having a composition represented by O2.

[0098] Example 4 Ni 0.89 Co 0.03 Mn 0.08 Transition metal complex hydroxide (D 50 : 9μm) was baked at 1,020℃ for 9 hours in an air atmosphere to form Ni 0.89 Co 0.03 Mn 0.08 A transition metal composite oxide having a composition represented by the formula O was produced.

[0099] The prepared transition metal composite oxide and LiOH were mixed so that the molar ratio of lithium (Li) to transition metal (Me) (Li / Me) was 1, and the mixture was subjected to primary firing at 900°C for 12 hours in an oxygen atmosphere, followed by pulverization using a jet mill and secondary firing at 800°C for 12 hours in an oxygen atmosphere to obtain LiNi 0.89 Co 0.03 Mn 0.08 A positive electrode active material was prepared, which was a lithium transition metal composite oxide in the form of a single particle having a composition represented by O2.

[0100] Example 5 Ni 0.96 Co 0.03 Mn 0.01 Transition metal complex hydroxide (D 50: 7μm) was baked at 1,020℃ for 9 hours in an air atmosphere to form Ni 0.96 Co 0.03 Mn 0.01 A transition metal composite oxide having a composition represented by the formula O was produced.

[0101] The prepared transition metal composite oxide and LiOH were mixed so that the molar ratio of lithium (Li) to transition metal (Me) (Li / Me) was 1.05, and the mixture was subjected to primary firing at 800°C for 12 hours in an oxygen atmosphere, and then pulverized using a jet mill. The mixture was then subjected to secondary firing at 700°C for 12 hours in an oxygen atmosphere to obtain Li. 1.05 Ni 0.96 Co 0.03 Mn 0.01 A positive electrode active material was prepared, which was a lithium transition metal composite oxide in the form of a single particle having a composition represented by O2.

[0102] Example 6 Ni 0.96 Co 0.03 Mn 0.01 Transition metal complex hydroxide (D 50 The mixture was mixed with LiOH so that the molar ratio of lithium (Li) to transition metal (Me) (Li / Me) was 1, and the mixture was subjected to primary firing at 830°C for 12 hours in an oxygen atmosphere. The mixture was then pulverized using a jet mill and subjected to secondary firing at 770°C for 12 hours in an oxygen atmosphere to produce LiNi 0.96 Co 0.03 Mn 0.01 A positive electrode active material was prepared, which was a lithium transition metal composite oxide in the form of a single particle having a composition represented by O2.

[0103] Example 7 Ni 0.885 Co 0.035 Mn 0.08 Transition metal complex hydroxide (D 50The mixture was mixed with LiOH so that the molar ratio of lithium (Li) to transition metal (Me) (Li / Me) was 1, and the mixture was subjected to primary firing at 900°C for 12 hours in an oxygen atmosphere. The mixture was then pulverized using a jet mill and subjected to secondary firing at 800°C for 12 hours in an oxygen atmosphere to produce LiNi 0.885 Co 0.035 Mn 0.08 A positive electrode active material was prepared, which was a lithium transition metal composite oxide in the form of a single particle having a composition represented by O2.

[0104] Comparative Example 1 The same procedure as in Example 1 was carried out, except that the primary firing was carried out at 700°C instead of 800°C, and the secondary firing was carried out at 800°C instead of 700°C, to produce LiNi 0.96 Co 0.03 Mn 0.01 A positive electrode active material was prepared, which was a lithium transition metal composite oxide in the form of a single particle having a composition represented by O2.

[0105] Comparative Example 2 The same procedure as in Example 1 was carried out, except that the primary firing was carried out at 1,020°C instead of 800°C, to obtain LiNi 0.96 Co 0.03 Mn 0.01 A positive electrode active material was prepared, which was a lithium transition metal composite oxide in the form of a single particle having a composition represented by O2.

[0106] Comparative Example 3 The same procedure as in Example 6 was carried out, except that the primary firing was carried out at 770°C instead of 830°C, to obtain LiNi 0.96 Co 0.03 Mn 0.01 A positive electrode active material was prepared, which was a lithium transition metal composite oxide in the form of a single particle having a composition represented by O2.

[0107] Comparative Example 4 In Example 7, the same procedure as in Example 1 was carried out, except that the primary firing was carried out at 850°C instead of 900°C, to obtain LiNi 0.885 Co 0.035 Mn0.08 A positive electrode active material was prepared, which was a lithium transition metal composite oxide in the form of a single particle having a composition represented by O2.

[0108] Experimental example Experimental Example 1: SEM photography and analysis of volume cumulative distribution by particle size During the production of the positive electrode active materials of Examples 1 to 7 and Comparative Examples 1 to 4, the positive electrode active material precursors, which are transition metal composite oxides and transition metal composite hydroxides before being mixed with the lithium compound, and the positive electrode active materials produced in Examples 1 to 7 and Comparative Examples 1 to 4 were photographed using a scanning electron microscope (SEM, Inspect F, manufactured by FEI), and the photographs are shown in Figures 2 to 12, respectively.

[0109] Furthermore, the positive electrode active materials produced in Examples 1 to 7 and Comparative Examples 1 to 4 were subjected to a particle size analyzer (PSD, manufactured by Malvern, Martersizer 3000) to measure the D 10 , D 50 and D 90 The mode of the volume cumulative distribution of particle size was measured and shown in FIG. 1 and Table 1. The negative skewness was calculated using the following mathematical formula 1 and shown in Table 1.

[0110] [Mathematical formula 1] Negative skewness = (Mode-D 10 ) / D 50

[0111] [Table 1]

[0112] As shown in FIGS. 2 to 12, it was confirmed that the positive electrode active materials prepared in Examples 1 to 7 and Comparative Examples 1 to 4 were all prepared as positive electrode active materials in the form of single particles as defined in the present invention.

[0113] In addition, as shown in Table 1, the positive electrode active materials prepared in Examples 1 to 7 were D 50It can be seen that the negative skewness calculated by Equation 1 is 0.4 or more, and the positive electrode active materials prepared in Comparative Examples 3 and 4 have a D 50 It was confirmed that the particle size was less than 5 μm.

[0114] Experimental Example 2: Measurement of rolling density Using an automatic pellet press (Carver, 3887.4), a cylindrical mold was placed on a circular pellet holder with a diameter of 13 mm to adjust the zero point for thickness. Then, 3 g of each of the positive electrode active materials prepared in Examples 1 to 7 and Comparative Examples 1 to 4 was placed on the circular pellet holder, and a force equivalent to 9,000 kgf was applied to measure the thickness of the formed pellets. The pellet volume was then calculated using Equation 2 below, and the rolling density was calculated using Equation 3 below. The results are shown in Table 2 below.

[0115] [Mathematical formula 2] Pellet volume (cm 3 ) = π (radius of circular pellet holder) 2 × Pellet thickness

[0116] [Mathematical formula 3] Rolling density (g / cm 3 ) = Weight of positive electrode active material (g) / Volume of pellet (cm 3 )

[0117] [Table 2]

[0118] As shown in Table 2, the positive electrode active materials prepared in Examples 1 to 7 were in the form of single particles by adjusting the primary and secondary firing temperatures. 50 is 5 μm or more, the fine powder content due to the negative skewness value is adjusted to an appropriate level, and the rolling density calculated by mathematical formula 3 is 3.56 g / cm 3From these results, it is expected that when the positive electrode active material according to the present invention is used, the rolling density during the preparation of the positive electrode is improved, thereby increasing the energy density of the lithium secondary battery, and thus improving the capacity characteristics.

[0119] On the other hand, the cathode active material prepared in Comparative Example 1 has a secondary firing temperature higher than the primary firing temperature, and the cathode active material prepared in Comparative Example 2 has a secondary firing temperature lower than the primary firing temperature. However, because the temperature difference is too large, the cathode active material is in a single particle form and D 50 Although the fine powder content was adjusted to an appropriate level by the negative skewness value, the rolling density was 3.53 g / cm 3 This does not meet the minimum standard for achieving the effects of the present invention, and is less than 0.06 g / cm as compared to Examples 1 and 2, which used the same positive electrode active material precursor and lithium source material. 3 , max. 0.19g / cm 3 It was possible to confirm that there was a difference.

[0120] In addition, the positive electrode active material prepared in Comparative Example 3 was subjected to the primary and secondary firings at the same temperature. 50 It can be seen that the rolling density is also low, and in particular, the rolling density is 0.05 g / cm compared to Example 6, which used a cathode active material precursor and a lithium source material of the same composition. 3 It was possible to confirm that there was a difference.

[0121] In addition, the cathode active material prepared in Comparative Example 4 had a secondary baking temperature lower than the primary baking temperature, but the baking temperature suitable for the transition metal hydroxide, which is the cathode active material precursor, could not be sufficiently secured. As shown in Table 1, 50 It can be seen that the rolling density is also low, and in particular, the rolling density is 0.11 g / cm compared to Example 7, which used a cathode active material precursor and a lithium source material of the same composition. 3It was possible to confirm that there was a difference.

Claims

1. a lithium transition metal composite oxide in the form of a single particle, the lithium transition metal composite oxide including nickel, cobalt, and manganese; The lithium transition metal composite oxide contains nickel in an amount of 60 mol % or more of all transition metals, D ５０ is 5 μm or more, When pellets were formed using an automatic pellet press with a force of 9,000 kgf, the rolling density calculated by the following mathematical formula 3 was 3.56 g / cm ３ This is the positive electrode active material. [Mathematical formula 3] Rolling density (g / cm ３ ) = Weight of positive electrode active material (g) / Volume of pellet (cm ３ )

2. The positive electrode active material according to claim 1 , wherein the lithium transition metal composite oxide in the form of a single particle is a single particle or a secondary particle formed by agglomeration of 10 or less primary particles.

3. The positive electrode active material according to claim 1 , wherein the lithium transition metal composite oxide has an average composition represented by the following Chemical Formula 1: [Chemical formula 1] Li ｘ Ni ａ Co ｂ Mn ｃ M １ ｄ O ２ In the above formula 1, M １ represents one or more elements selected from the group consisting of Al, Zr, B, W, Mo, Cr, Nb, Mg, Hf, Ta, La, Ti, Sr, Ba, Ce, F, P, S, and Y, and 0.9≦x≦1.3, 0.6≦a<1.0, 0<b<0.4, 0<c<0.4, 0≦d≦0.2, and a+b+c+d=1.

4. The positive electrode active material according to claim 3 , wherein X is 0.9 or more and 1.1 or less.

5. D ５０ The positive electrode active material according to claim 1 , wherein the average particle diameter is 5 μm or more and 9 μm or less.

6. Rolled density is 3.56 g / cm ３ 3.80g / cm or more ３ The positive electrode active material according to claim 1 , wherein:

7. The mode (Mode) in the volume cumulative distribution by particle size is D ５０ The positive electrode active material of claim 1 , wherein

8. The positive electrode active material of claim 7 , wherein the positive electrode active material has a negative skewness value calculated by the following Equation 1 greater than 0: [Mathematical formula 1] Negative skewness = (Mode-D １０ ) / D ５０

9. The positive electrode active material according to claim 8 , wherein the negative skewness value is 0.40 or more and 0.75 or less.

10. A positive electrode comprising the positive electrode active material according to claim 1 .

11. A lithium secondary battery comprising: the positive electrode according to claim 10; a negative electrode; a separator interposed between the positive electrode and the negative electrode; and an electrolyte.

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