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

Abstract

The present invention relates to a positive electrode active material, and a positive electrode and a lithium secondary battery comprising same, wherein the positive electrode active material comprises a lithium composite transition metal oxide in the form of single particles containing nickel, manganese, cobalt, and aluminum, and satisfies at least one of conditions 1 and 2 described in the present specification.

Description

Cathode active material, cathode and lithium secondary battery containing same

[0001] Cross-citation with related applications

[0002] This application claims the benefit of priority from Korean Patent Application No. 10-2024-0081019, filed June 21, 2024, 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 positive electrode including the same, and a lithium secondary battery.

[0005]

[0006] As technological development and demand for mobile devices increase, 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-composite transition metal oxides are used as cathode active materials in lithium secondary batteries. Among these, lithium-cobalt-composite metal oxides such as LiCoO2, which exhibit high operating voltage and excellent capacity characteristics, are primarily used. However, LiCoO2 suffers from poor thermal properties due to crystal structure instability following delithiation. Furthermore, its high cost limits its mass use as a power source in fields such as electric vehicles.

[0008] As a material to replace the above LiCoO2, lithium manganese composite metal oxides (such as LiMnO2 or LiMn2O4), lithium iron phosphate compounds (such as LiFePO4), or lithium nickel composite metal oxides (such as LiNiO2) have been developed. Among these, research and development on lithium nickel composite metal oxides, which have a high reversible capacity of about 200 mAh / g and make it easy to implement large-capacity batteries, is being actively studied. However, LiNiO2 has inferior thermal stability compared to LiCoO2, and there was a problem that the positive electrode active material itself decomposed when an internal short circuit occurred due to external pressure in a charged state, causing the battery to rupture and catch fire. Accordingly, as a method to improve the low thermal stability of LiNiO2 while maintaining the excellent reversible capacity, lithium transition metal oxides in which some of the Ni was replaced with Co, Mn, or Al were developed.

[0009] In the case of lithium ion batteries using such lithium composite transition metal oxides, particularly lithium composite transition metal oxides containing a high nickel (Ni-rich) content, as cathode active materials, the capacity of the battery, whether it has high output, and whether gas is generated at high temperatures are affected not only by chemical properties such as the composition of the cathode active material, the content of impurities, and the content of lithium byproducts present on the surface, but also by physical properties such as the size, surface area, density, and shape of the cathode active material particles.

[0010] In general, a method has been used to improve the volumetric energy density of a battery by filling the gaps between particles to maximize the volumetric energy density of the battery, and a method of rolling the positive active material layer using a roll press has been used to manufacture a positive active material layer with a denser structure. At this time, due to the difference in particle strength between positive active materials, excessive cracks occur in particles with relatively weak particle strength during rolling, which not only causes the particles to lose their original shape, but also causes the contact area with the electrolyte to become excessively wide, which causes a problem of reduced life characteristics when applied to a battery.

[0011] Therefore, there is a need to develop a cathode active material that can improve the energy volume density while also improving the life characteristics by suppressing particle breakage during rolling for cathode manufacturing.

[0012]

[0013] The present invention is intended to solve the above problems and to provide a positive electrode active material with improved energy density and particle strength.

[0014] In addition, the present invention seeks to provide a cathode and secondary battery having excellent capacity characteristics and lifespan characteristics, including the cathode active material as described above.

[0015]

[0016] (1) The present invention provides a cathode active material comprising a lithium composite transition metal oxide in the form of a single particle containing nickel, manganese, cobalt, and aluminum, and satisfying at least one of the following conditions 1 and 2.

[0017] [Condition 1] The average particle size reduction rate (χ) calculated by the following equation (1) is 35.00% or less;

[0018] Equation (1) Average particle size reduction rate (χ) [%] =

[0019] In the above equation (1), D50 is the particle size [㎛] corresponding to 50% of the volume cumulative distribution according to the particle size of the positive electrode active material, and D A 2g of the positive electrode active material is divided into small pieces and filled into a cylindrical holder with a diameter of 13mm, and then a force of 9000kgf is applied for 20 seconds. The particle size [㎛] corresponding to 50% of the volume cumulative distribution according to the particle size of the positive electrode active material is measured.

[0020] [Condition 2] Differential occurrence rate (φ) calculated by the following equation (2) is 6.0000% or less;

[0021] Equation (2) Differential occurrence rate (φ)[%] =

[0022] In the above equation (2), S A 2g of positive electrode active material was divided into small pieces and filled into a cylindrical holder with a diameter of 13mm, and then a force of 9000kgf was applied for 20 seconds. The total area under the line in the graph showing the cumulative volume distribution according to the particle size of the positive electrode active material measured is S B is the area under the line in the graph above where the particle size of the positive electrode active material is 1㎛ or less.

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

[0024] [Chemical Formula 1] Li 1+x Ni a Mn b Co c Al d M 1 e O2

[0025] In the above chemical formula 1, M 1is at least one selected from the group consisting of Y, Zr, B, C, F, Mg, Si, P, Ca, Sc, Ti, V, Sr, Nb, Mo, Ba, La, Hf, Ta, W, Bi, Ce, Sm and Gd, and -0.1≤x≤0.3, 0.5≤a<1, 0 <b<0.5, 0<c<0.5, 0<d<0.5, 0≤e≤0.1 이다.

[0026] (3) The present invention provides a positive electrode active material in (1) or (2), wherein the lithium composite transition metal oxide contains aluminum in an amount of 3,000 ppm or more and 8,000 ppm or less based on the total weight of the positive electrode active material.

[0027] (4) The present invention provides a cathode active material, which further includes a coating formed on the lithium composite transition metal oxide in any one of the above (1) to (3), and wherein the coating includes at least one coating element selected from the group consisting of Y, Zr, B, C, F, Mg, Si, P, Ca, Sc, Ti, V, Sr, Nb, Mo, Ba, La, Hf, Ta, W, Bi, Ce, Sm and Gd.

[0028] (5) The present invention provides a positive electrode active material in the above (4), wherein the coating portion is of an island type.

[0029] (6) The present invention provides a positive electrode active material having an average particle size reduction rate (χ) of 10% or more and 25% or less in any one of (1) to (5) above.

[0030] (7) The present invention provides a positive electrode active material having a differential particle generation rate (φ) of 3% or less in any one of the above (1) to (6).

[0031] (8) The present invention relates to any one of the above (1) to (7), wherein the average particle diameter (D 50 ) provides a positive electrode active material having a size of 1㎛ or more and 15㎛ or less.

[0032] (9) The present invention provides a positive electrode including a positive electrode active material including a lithium composite transition metal oxide in the form of single particles containing nickel, manganese, cobalt, and aluminum, and satisfying at least one of the following conditions 3 and 4.

[0033] [Condition 3] The average particle size reduction rate (χ') calculated by the following equation (3) is 16.00% or less;

[0034] Equation (3) Average particle size reduction rate (χ') [%] =

[0035] In the above equation (3), D' 50 is the particle size [㎛] corresponding to 50% of the volume cumulative distribution according to the particle size of the positive electrode active material, and D' A is the particle size [㎛] corresponding to 50% of the cumulative volume distribution according to the particle size of the positive electrode active material measured by separating the positive electrode active material contained in the positive electrode after applying force to the positive electrode until the porosity becomes 20%.

[0036] [Condition 4] The differential incidence rate (φ') calculated by the following equation (4) is 0.0550% or less;

[0037] Equation (4) Differential occurrence rate (φ')[%] =

[0038] In the above equation (4), S' A S' is the total area under the line in the graph showing the cumulative volume distribution according to the particle size of the positive electrode active material measured by separating the positive electrode active material contained in the positive electrode after applying force to the positive electrode until the porosity becomes 20%, and B is the area under the line in the graph above where the particle size of the positive electrode active material is 1㎛ or less.

[0039] (10) The present invention provides a positive electrode in the above (9), wherein the positive electrode active material satisfies at least one of the following conditions 1 and 2.

[0040] [Condition 1] The average particle size reduction rate (χ) calculated by the following equation (1) is 35.00% or less;

[0041] Equation (1) Average particle size reduction rate (χ) [%] =

[0042] In the above equation (1), D 50 is the particle size [㎛] corresponding to 50% of the volume cumulative distribution according to the particle size of the positive electrode active material, and D A 2g of the positive electrode active material is divided into small pieces and filled into a cylindrical holder with a diameter of 13mm, and then a force of 9000kgf is applied for 20 seconds. The particle size [㎛] corresponding to 50% of the volume cumulative distribution according to the particle size of the positive electrode active material is measured.

[0043] [Condition 2] The differential incidence rate (φ) calculated by the following equation (2) is 6.0000% or less;

[0044] Equation (2) Differential occurrence rate (φ)[%] =

[0045] In the above equation (2), S A 2g of positive electrode active material was divided into small pieces and filled into a cylindrical holder with a diameter of 13mm, and then a force of 9000kgf was applied for 20 seconds. The total area under the line in the graph showing the cumulative volume distribution according to the particle size of the positive electrode active material measured is S B is the area under the line in the graph above where the particle size of the positive electrode active material is 1㎛ or less.

[0046] (11) The present invention provides a lithium secondary battery including a positive electrode according to (9) or (10).

[0047]

[0048] The cathode active material according to the present invention comprises a lithium composite transition metal oxide in the form of single particles containing nickel, manganese, cobalt, and aluminum, and by satisfying at least one of conditions 1 and 2 described herein, the energy density and particle strength of the cathode active material are improved.

[0049] Accordingly, there is an effect of improving the capacity characteristics and life characteristics of the positive electrode and secondary battery including the positive electrode active material.

[0050] The positive electrode according to the present invention includes a positive electrode active material including a lithium composite transition metal oxide in the form of single particles containing nickel, manganese, cobalt, and aluminum, and realizes effects of improved energy density and life characteristics, etc., by satisfying at least one of conditions 3 and 4 described herein.

[0051] Accordingly, there is an effect of improving the capacity characteristics and life characteristics of the secondary battery including the above positive electrode.

[0052]

[0053] Figure 1 is a SEM image of the positive electrode active material manufactured in Example 1.

[0054] Figure 2 is an SEM image of the positive electrode active material manufactured in Example 2.

[0055] Figure 3 is an SEM image of the positive electrode active material manufactured in Example 3.

[0056] Figure 4 is an SEM image of the positive electrode active material manufactured in Example 4.

[0057] Figure 5 is an SEM image of the positive electrode active material manufactured in Comparative Example 1.

[0058] Figure 6 is an SEM image of the positive electrode active material manufactured in Comparative Example 3.

[0059] Figure 7 is an SEM image of the positive electrode active material manufactured in Comparative Example 5.

[0060] Figure 8 is a graph showing the cumulative volume distribution according to the particle size of the positive electrode active material manufactured in Example 1.

[0061] Figure 9 is a graph showing the cumulative volume distribution according to the particle size of the positive electrode active material manufactured in Example 2.

[0062] Figure 10 is a graph showing the cumulative volume distribution according to the particle size of the positive electrode active material manufactured in Example 3.

[0063] Figure 11 is a graph showing the cumulative volume distribution according to the particle size of the positive electrode active material manufactured in Example 4.

[0064] Figure 12 is a graph showing the cumulative volume distribution according to the particle size of the positive electrode active material manufactured in Comparative Example 1.

[0065] Figure 13 is a graph showing the cumulative volume distribution according to the particle size of the positive electrode active material manufactured in Comparative Example 3.

[0066] Figure 14 is a graph showing the cumulative volume distribution according to the particle size of the positive electrode active material manufactured in Comparative Example 5.

[0067] Figure 15 is a graph showing the cumulative volume distribution according to the particle size of the positive electrode including the positive electrode active material manufactured in Example 5.

[0068] Figure 16 is a graph showing the cumulative volume distribution according to the particle size of the positive electrode including the positive electrode active material manufactured in Example 6.

[0069] Figure 17 is a graph showing the cumulative volume distribution according to the particle size of the positive electrode including the positive electrode active material manufactured in Example 7.

[0070] Figure 18 is a graph showing the cumulative volume distribution according to the particle size of the positive electrode including the positive electrode active material manufactured in Example 8.

[0071] Figure 19 is a graph showing the cumulative volume distribution according to the particle size of the positive electrode including the positive electrode active material manufactured in Comparative Example 2.

[0072] Figure 20 is a graph showing the cumulative volume distribution according to the particle size of the positive electrode including the positive electrode active material manufactured in Comparative Example 4.

[0073] Figure 21 is a graph showing the cumulative volume distribution according to the particle size of the positive electrode including the positive electrode active material manufactured in Comparative Example 6.

[0074]

[0075] Hereinafter, the present invention will be described in more detail to help understand the present invention.

[0076] 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.

[0077] In this specification, it should be understood that terms such as “include,” “have,” or “have” 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.

[0078] In this specification, 'primary particle' means the smallest particle unit recognized when observing a positive electrode active material using a scanning electron microscope (SEM), and 'secondary particle' means a secondary structure formed by the aggregation of multiple primary particles.

[0079] In this specification, the term 'single particle form' is a concept that is contrasted with the secondary particle form formed by agglomeration of tens to hundreds of primary particles manufactured by a conventional method, and means a form in which 50 or fewer primary particles are aggregated. 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 2 to 50 primary particles are aggregated. Specifically, it may be a form in which 2 or more, 40 or fewer, 30 or fewer, or 20 or fewer primary particles are aggregated, and preferably, it may be a form in which 2 or more and 20 or fewer primary particles are aggregated. The single particle form is distinguished from a secondary particle in which more than 50 primary particles are aggregated.

[0080] In this specification, the content of each element in the lithium composite transition metal oxide may be measured through ICP (Inductive Coupled Plasma) analysis using an inductively coupled plasma optical emission spectrometer (ICP-OES; Optima 7300DV, PerkinElmer).

[0081] In this specification, 'average particle diameter (D 50 )' means the particle size corresponding to 50% of the volume cumulative distribution in the particle size distribution curve (graph curve of particle size distribution), and 'fine powder' means a particle with a particle size of 1㎛ or less. Specifically, after dispersing the powder to be measured in a dispersion medium, it is introduced into a commercially available laser diffraction particle size measuring device (e.g., S3500 of Microtrac) and measuring the difference in diffraction pattern according to particle size when the particles pass through the laser beam to calculate the particle size distribution, and by calculating the particle diameter at the point where it becomes 50% of the volume cumulative distribution according to particle size, the average particle diameter (D 50 ) can be measured.

[0082]

[0083] positive electrode active material

[0084] Hereinafter, the positive electrode active material according to the present invention will be described.

[0085]

[0086] The cathode active material according to the present invention comprises a lithium composite transition metal oxide in the form of a single particle containing nickel, manganese, cobalt and aluminum, and satisfies at least one of the following conditions 1 and 2.

[0087] [Condition 1] The average particle size reduction rate (χ) calculated by the following equation (1) is 35.00% or less;

[0088] Equation (1) Average particle size reduction rate (χ) [%] =

[0089] In the above equation (1), D 50 is the particle size [㎛] corresponding to 50% of the volume cumulative distribution according to the particle size of the positive electrode active material, and D A 2g of the positive electrode active material is divided into small pieces and filled into a cylindrical holder with a diameter of 13mm, and then a force of 9000kgf is applied for 20 seconds. The particle size [㎛] corresponding to 50% of the volume cumulative distribution according to the particle size of the positive electrode active material is measured.

[0090] [Condition 2] The differential incidence rate (φ) calculated by the following equation (2) is 6.0000% or less;

[0091] Equation (2) Differential occurrence rate (φ)[%] =

[0092] In the above equation (2), S A 2g of positive electrode active material was divided into small pieces and filled into a cylindrical holder with a diameter of 13mm, and then a force of 9000kgf was applied for 20 seconds. The total area under the line in the graph showing the cumulative volume distribution according to the particle size of the positive electrode active material measured is S B is the area under the line in the graph above where the particle size of the positive electrode active material is 1㎛ or less.

[0093]

[0094] The lithium composite transition metal oxide is in the form of a single particle formed by agglomeration of 50 or fewer primary particles. When the lithium composite transition metal oxide is in the form of a single particle, it has excellent stability, and when a positive electrode active material containing the lithium composite transition metal oxide is rolled, the positive electrode active material is less likely to break or crack, thereby reducing side reactions between the positive electrode active material and the electrolyte. This improves the durability against volume changes during charge and discharge of the battery, thereby improving the life characteristics.

[0095] Meanwhile, lithium composite transition metal oxides, which are secondary particles, are prone to particle breakage during the electrode rolling process, which increases the surface area of ​​the positive electrode active material, thereby worsening the deterioration of storage and life performance at high temperatures. In particular, lithium composite transition metal oxides containing a high nickel content are more prone to particle breakage during rolling for positive electrode manufacturing, which may increase side reactions between the lithium composite transition metal oxide and the electrolyte, and deteriorate the physical properties of the battery.

[0096] However, when the positive electrode active material includes a lithium composite transition metal oxide in the form of a single particle containing nickel, manganese, cobalt, and aluminum, as in the present invention, the structural stability of the positive electrode active material is improved. In particular, since aluminum improves the stability of the particle structure and the internal crystal lattice, when aluminum is included, the phenomenon of breakage of the positive electrode active material particles during rolling is reduced, and the side reaction between the positive electrode active material and the electrolyte is reduced. In addition, when the positive electrode active material satisfies at least one of the above conditions 1 and 2, the phenomenon of breakage of the positive electrode active material particles during rolling is reduced, and the side reaction between the positive electrode active material and the electrolyte is reduced, so that the capacity characteristics and life characteristics of a battery including the positive electrode active material can be improved. On the other hand, if the positive electrode active material does not contain aluminum, unlike the present invention, or does not satisfy both conditions 1 and 2, there is a problem that the positive electrode active material particles are excessively broken during rolling for battery manufacturing, and a side reaction occurs between the positive electrode active material and the electrolyte, resulting in poor capacity characteristics and life characteristics of the battery.

[0097]

[0098] According to one embodiment of the present invention, the lithium composite transition metal oxide may have a composition represented by the following chemical formula 1.

[0099] [Chemical Formula 1]

[0100] Li 1+x Ni a Mn b Co c Al d M 1 e O2

[0101]

[0102] In the above chemical formula 1, M 1is at least one selected from the group consisting of Y, Zr, B, C, F, Mg, Si, P, Ca, Sc, Ti, V, Sr, Nb, Mo, Ba, La, Hf, Ta, W, Bi, Ce, Sm and Gd, and -0.1≤x≤0.3, 0.5≤a<1, 0 <b<0.5, 0<c<0.5, 0<d<0.5, 0≤e≤0.1이다.

[0103] Above M 1 is a doping element, specifically the above M 1 It may be at least one selected from the group consisting of Y, Zr, B, C, F, Mg, Si, P, Ca, Sc, Ti, V, Sr, Nb, Mo, Ba, La, Hf, Ta, W, Bi, Ce, Sm and Gd. The above M 1 Although it is not essential to include, if included in an appropriate amount, the particle shape of the positive electrode active material can be improved and the stability of the crystal structure can be enhanced. In particular, the above M 1 If this is Y or Zr, the cycle characteristics and life characteristics of the battery can be improved, and the energy density can be increased.

[0104] Meanwhile, the above x may be -0.1 or more, 0 or more, 0.01 or more, 0.02 or more, 0.03 or more, or 0.04 or more, and may be 0.05 or less, 0.06 or less, 0.07 or less, 0.08 or less, 0.09 or less, 0.1 or less, 0.2 or less, or 0.3 or less. When x satisfies the above range, high-capacity characteristics and high energy density per unit volume can be realized.

[0105] The above a is the molar fraction of nickel (Ni) among the total metals excluding lithium in the lithium composite transition metal oxide, and may be 0.5 or more, 0.6 or more, 0.7 or more, 0.8 or more, or 0.85 or more, and may be 0.9 or less, 0.95 or less, or less than 1. When a is within the above range, the energy density increases, thereby improving the output characteristics and capacity characteristics of the battery.

[0106] The above b is the mole fraction of manganese (Mn) among the total metals excluding lithium in the lithium composite transition metal oxide, and may be greater than 0, 0.01 or more, 0.02 or more, 0.03 or more, 0.04 or more, 0.05 or more, 0.06 or more, 0.07 or more, or 0.08 or more, and may be 0.1 or less, 0.2 or less, 0.3 or less, 0.4 or less, or less than 0.5. When b satisfies the above range, structural stability increases, and the decomposition reaction of the electrolyte may be relatively reduced.

[0107] The above c is the mole fraction of cobalt (Co) among the total metals excluding lithium in the lithium composite transition metal oxide, and may be greater than 0, 0.01 or more, 0.02 or more, or 0.03 or more, and may be 0.05 or less, 0.06 or less, 0.07 or less, 0.08 or less, 0.09 or less, 0.1 or less, 0.2 or less, 0.3 or less, 0.4 or less, or less than 0.5. When c satisfies the above range, there is an effect of increasing structural stability and improving the capacity characteristics of the battery without deteriorating the life characteristics and resistance characteristics.

[0108] The above d is the molar fraction of aluminum (Al) among the total metals excluding lithium in the lithium composite transition metal oxide, and may be greater than 0, 0.001 or more, 0.002 or more, 0.003 or more, 0.004 or more, or 0.005 or more, and may be 0.006 or less, 0.007 or less, 0.008 or less, 0.009 or less, 0.01 or less, 0.1 or less, 0.2 or less, 0.3 or less, 0.4 or less, or less than 0.5. When d satisfies the above range, the structural stability of the particle and the stability of the internal crystal lattice increase, the decomposition reaction of the electrolyte can be relatively reduced, and there is an effect of improving the output characteristics of the battery.

[0109] The above e is M of all metals except lithium in the lithium complex transition metal oxide. 1The mole fraction of e may be 0 or more, 0.0001 or more, 0.00015 or more, 0.0002 or more, or 0.00025 or more, and may be 0.0003 or less, 0.0004 or less, 0.0005 or less, 0.0006 or less, 0.0007 or less, 0.0008 or less, 0.0009 or less, 0.001 or less, 0.01 or less, 0.02 or less, 0.03 or less, 0.04 or less, 0.05 or less, 0.06 or less, 0.07 or less, 0.08 or less, 0.09 or less, or 0.1 or less. When e satisfies the above range, the stability of the crystal structure of the positive electrode active material may be improved and the particle shape may be improved.

[0110] The above a, b, c, d, and e can be a+b+c+d+e=1.

[0111]

[0112] According to one embodiment of the present invention, the lithium composite transition metal oxide may contain aluminum in an amount of 3,000 ppm or more and 8,000 ppm or more based on the total weight of the positive electrode active material. Specifically, the aluminum may be contained in an amount of 3,000 ppm or more, 3,500 ppm or more, 4,000 ppm or more, 4,500 ppm or more, or 5,000 ppm or more, and 5,500 ppm or less, 6,000 ppm or less, 6,500 ppm or less, 7,000 ppm or less, 7,500 ppm or less, or 8,000 ppm or less based on the total weight of the positive electrode active material. When the content of the aluminum is within the above range, the structural stability of the particle and the stability of the internal crystal lattice may increase, the decomposition reaction of the electrolyte may be relatively reduced, and the output characteristics of the battery may be improved.

[0113]

[0114] According to one embodiment of the present invention, the lithium composite transition metal oxide further includes a coating portion formed on the lithium composite transition metal oxide, and the coating portion may include one or more coating elements selected from the group consisting of Y, Zr, B, C, F, Mg, Si, P, Ca, Sc, Ti, V, Sr, Nb, Mo, Ba, La, Hf, Ta, W, Bi, Ce, Sm, and Gd. In this case, the coating portion blocks contact with the electrolyte, so that side reactions between the positive electrode active material and the electrolyte can be reduced.

[0115]

[0116] According to one embodiment of the present invention, the coating portion may be island-shaped. Specifically, the coating layer may be discontinuously distributed (island-shaped) on the surface of the lithium composite transition metal oxide. In this case, the coating portion may block contact with the electrolyte without acting as a resistor, thereby reducing side reactions between the positive electrode active material and the electrolyte.

[0117] For reference, the island type refers to a case where the formation area of ​​the coating portion is less than 100% based on the total surface area of ​​the lithium composite transition metal oxide. The formation area of ​​the coating portion may be greater than 0%, 1% or more, 5% or more, 10% or more, and may be 20% or less, 30% or less, 40% or less, 50% or less, 60% or less, 70% or less, 80% or less, 90% or less, or less than 100% based on the total surface area of ​​the lithium composite transition metal oxide.

[0118]

[0119] Below, each condition, Condition 1 and Condition 2, is explained in detail.

[0120]

[0121] [Condition 1]

[0122] According to the present invention, the average particle size reduction rate (χ) calculated by the following equation (1) is 35.00% or less.

[0123] Equation (1) Average particle size reduction rate (χ) [%] =

[0124] In the above equation (1), D 50 is the particle size [㎛] corresponding to 50% of the volume cumulative distribution according to the particle size of the positive electrode active material, and D A The particle size [㎛] corresponding to 50% of the volume cumulative distribution according to the particle size of the positive electrode active material measured after dividing 2g of the positive electrode active material into small pieces and filling a cylindrical holder with a diameter of 13mm and applying a force of 9000kgf for 20 seconds.

[0125] In the present invention, the concept of average particle size reduction rate (χ) was used to evaluate and quantitatively represent the degree of particle breakage before and after applying force to the positive electrode active material. The average particle size reduction rate (χ) is an index indicating the degree to which the average particle size of the positive electrode active material changed after applying force at 9000 kgf for 20 seconds compared to before filling 2 g of the positive electrode active material into a cylindrical holder with a diameter of 13 mm.

[0126] Applying a force of 9000 kgf corresponds to a level similar to or slightly higher than the rolling pressure during positive electrode manufacturing, so it can be understood as a more clear standard for evaluating the particle breakage phenomenon during battery manufacturing, and in particular, the tendency when the rolling pressure is increased can be specifically confirmed.

[0127] The low average particle size reduction rate (χ) above means that when a certain force is applied to the positive electrode active material, the phenomenon of breaking of the positive electrode active material particles occurs less, and thus the particle size reduction is low.

[0128] Specifically, the average particle size reduction rate (χ) may be 0.00% or more, 10.00% or more, 25.00% or less, 30.00% or less, or 35.00% or less. When the average particle size reduction rate (χ) is within the above range, the particle strength of the positive electrode active material is improved, so that the particle breakage phenomenon occurs less when force is applied. Accordingly, since the side reaction between the positive electrode active material and the electrolyte occurs relatively less, there is an effect of excellent life characteristics of a battery including the positive electrode active material while maintaining the energy density. In particular, when the average particle size reduction rate (χ) is 10.00% or more and 25.00% or less, there is an effect of excellent life characteristics of the battery at high temperatures. On the other hand, when the average particle size reduction rate (χ) exceeds 35.00%, there is a problem of inferior life characteristics of the battery at high temperatures.

[0129]

[0130] [Condition 2]

[0131] According to the present invention, the differential incidence rate (φ) calculated by the following equation (2) is 6.0000% or less.

[0132] Equation (2) Differential occurrence rate (φ)[%] =

[0133] In the above equation (2), S A 2g of positive electrode active material was divided into small pieces and filled into a cylindrical holder with a diameter of 13mm, and then a force of 9000kgf was applied for 20 seconds. The total area under the line in the graph showing the cumulative volume distribution according to the particle size of the positive electrode active material measured is S B is the area under the line in the graph above where the particle size of the positive electrode active material is 1㎛ or less.

[0134] In the present invention, the concept of fine particle generation rate (φ) was used to evaluate and quantitatively represent the degree of particle breakage following application of force to the positive electrode active material. The fine particle generation rate (φ) is an indicator of the extent to which the volume of fine particles having a diameter of 1 μm or less changes relative to the total volume of the positive electrode active material after dividing 2 g of the positive electrode active material into small pieces and filling a cylindrical holder with a diameter of 13 mm and applying a force of 9000 kgf for 20 seconds.

[0135] Applying a force of 9000 kgf corresponds to a level similar to or slightly higher than the rolling pressure during positive electrode manufacturing, so it can be understood as a more clear standard for evaluating the particle breakage phenomenon during battery manufacturing, and in particular, the tendency when the rolling pressure is increased can be specifically confirmed.

[0136] The low occurrence rate of the above-mentioned differential powder (φ) means that when a certain force is applied to the positive electrode active material, the phenomenon of breaking of the positive electrode active material particles occurs less, resulting in less occurrence of differential powder.

[0137] Specifically, the particle generation rate (φ) may be 0.0000% or more, or 0.0003% or more, and 3.0000% or less, or 5.0000% or less. When the particle generation rate (φ) is within the above range, the particle strength of the positive electrode active material is improved, so that the particle breakage phenomenon occurs less when force is applied. Accordingly, since the side reaction between the positive electrode active material and the electrolyte occurs relatively less, the life characteristics of the battery including the positive electrode active material are excellent while maintaining the energy density. In particular, when the particle generation rate (φ) is 3% or less, the life characteristics of the battery are more excellent at high temperatures. On the other hand, when the particle generation rate (φ) exceeds 5%, there is a problem that the life characteristics of the battery are inferior at high temperatures.

[0138]

[0139] According to one embodiment of the present invention, the positive electrode active material has an average particle diameter (D50 ) may be 1.00㎛ or more and 15.00㎛ or less. Specifically, the average particle diameter (D 50 ) may be 1.00 ㎛ or more, 1.50 ㎛ or more, 2.00 ㎛ or more, or 2.50 ㎛ or more, and may be 3.00 ㎛ or less, 4.00 ㎛ or less, 5.00 ㎛ or less, 6.00 ㎛ or less, 7.00 ㎛ or less, 8.00 ㎛ or less, 9.00 ㎛ or less, 10.00 ㎛ or less, 11.00 ㎛ or less, 12.00 ㎛ or less, 13.00 ㎛ or less, 14.00 ㎛ or less, or 15.00 ㎛ or less. The average particle diameter (D 50 ) is within the above range, there is an effect of improving the capacity characteristics of the manufactured secondary battery.

[0140]

[0141] Method for manufacturing positive electrode active material

[0142] Next, a method for manufacturing the positive electrode active material of the present invention will be described. The method for manufacturing the positive electrode active material of the present invention is a method for manufacturing the positive electrode active material according to the present invention.

[0143]

[0144] A method for manufacturing a cathode active material according to the present invention comprises the steps of (A) dry mixing a lithium (Li)-containing raw material, a nickel (Ni)-containing raw material, a manganese (Mn)-containing raw material, a cobalt (Co)-containing raw material, and an aluminum (Al)-containing raw material to prepare a mixture; (B) first firing the mixture to prepare a fired product; and (C) second firing the mixture by mixing the lithium (Li)-containing raw material with the fired product and preparing a lithium composite transition metal oxide. The first firing is performed under an oxygen atmosphere at a temperature of 860°C or higher and 1,000°C or lower, and the second firing is performed under an oxygen atmosphere at a temperature of 700°C or higher and 990°C or lower, and the first firing is performed at a higher temperature than the second firing.

[0145]

[0146] The positive electrode active material according to the present invention described above can be manufactured by appropriately controlling the type of raw material, the mixing ratio of raw materials, the heating rate, etc.

[0147]

[0148] Hereinafter, each step of the present invention will be described in detail.

[0149]

[0150] (A) Step

[0151] The present invention includes the step (A) of preparing a mixture by dry mixing a lithium (Li)-containing raw material, a nickel (Ni)-containing raw material, a manganese (Mn)-containing raw material, a cobalt (Co)-containing raw material, and an aluminum (Al)-containing raw material.

[0152] The lithium composite transition metal oxide of the present invention is mixed by a dry mixing method using a solid raw material mixture. The dry mixing method has the advantage of being able to be mass-produced through a relatively simple synthesis process.

[0153] On the other hand, when using a wet mixing method to manufacture a precursor, particle growth may not be smooth, so single particle formation may not proceed sufficiently, and since an over-sintering process is required, it may cause a decrease in capacity when using the battery due to reasons such as the formation of a rock-salt phase.

[0154] In selecting raw materials for lithium (Li), nickel (Ni), manganese (Mn), cobalt (Co), and aluminum (Al)-containing raw materials, any raw material applicable to a solid-state synthesis method may be used without limitation, and specifically, oxide, carbonate, and hydroxide series compounds may be used.

[0155] For example, the lithium (Li)-containing raw material may be at least one selected from the group consisting of LiOH, Li2CO3, LiNO3, LiNO2, LiOH H2O, LiH, LiF, LiCl, LiBr, LiI, CH3COOLi, Li2O, Li acetate, Li dicarboxylic acid, Li citrate, Li fatty acid, alkyl lithium, and lithium halides, and a mixture of one or two or more of these may be used. Considering the ease of procurement of raw materials, specifically, LiOH H2O may be used.

[0156] The nickel (Ni)-containing raw material may be at least one selected from the group consisting of NiO, Ni(OH)2, NiOㆍOH, NiCO3ㆍ2Ni(OH)2ㆍ4H2O, NiC2O4ㆍ2H2O, Ni(NO3)2ㆍ6H2O, fatty acid nickel, and nickel halides, and a mixture of one or two or more thereof may be used. Considering the ease of removing impurities, specifically, Ni(OH)2 may be used. According to one embodiment of the present invention, when the nickel (Ni)-containing raw material includes fine powder, a battery with reduced increase in resistance at high temperatures can be manufactured.

[0157] The above manganese (Mn)-containing raw material may be at least one selected from the group consisting of MnCO3, Mn2O3, MnO2, Mn3O4, Mn(NO3)2, manganese acetate, manganese dicarboxylate, manganese citrate, manganese salts of fatty acid manganese, oxyhydroxides, and halides of manganese chloride, and a mixture of one or two or more of these may be used. Considering the ease of procurement of raw materials, specifically, MnO2 may be used.

[0158] The cobalt (Co)-containing raw material may be at least one selected from the group consisting of Co(OH)2, Co3O4, CoOㆍOH, Co(OCOCH3)2ㆍ4H2O, Co(NO3)2ㆍ6H2O or Co(SO4)2ㆍ7H2O, fatty acid cobalt, and cobalt halides, and a mixture of one or two or more thereof may be used. According to one embodiment of the present invention, the cobalt (Co)-containing raw material may be at least one selected from the group consisting of cobalt hydroxide and cobalt oxide. In this case, it is easy to supply the raw material. In particular, when Co(OH)2 is used, a secondary battery with improved capacity characteristics and lifespan characteristics can be manufactured.

[0159] The above aluminum (Al)-containing raw material may be at least one selected from the group consisting of oxides, carbonates, nitrates, hydroxides, oxyhydroxides, and halides containing aluminum (Al), and a mixture of one or more of these may be used. Considering the ease of raw material supply, specifically, Al(OH)3 may be used. By mixing the aluminum (Al)-containing raw material, aluminum has the effect of improving the particle structure stability and internal crystal lattice stability of the positive electrode active material.

[0160] According to the present invention, in the step (A), a lithium (Li)-containing raw material, a nickel (Ni)-containing raw material, a manganese (Mn)-containing raw material, a cobalt (Co)-containing raw material, and an aluminum (Al)-containing raw material can be mixed in an amount such that the raw material has a composition represented by the chemical formula 1.

[0161] According to one embodiment of the present invention, in the step (A), a doping element-containing raw material including one or more doping elements selected from the group consisting of Y, Zr, B, C, F, Mg, Si, P, Ca, Sc, Ti, V, Sr, Nb, Mo, Ba, La, Hf, Ta, W, Bi, Ce, Sm and Gd may be further mixed. When the doping element-containing raw material is further mixed, the stability of the crystal structure of the positive electrode active material may be improved and the grain shape may be improved. In particular, when the doping element is Y or Zr, the cycle characteristics, life characteristics, etc. of the battery may be improved, and the energy density may be improved. Considering the ease of raw material supply, specifically, ZrO2 and Y2O3 may be further mixed.

[0162] According to one embodiment of the present invention, the doping element-containing raw material may be mixed so that the content of the doping element is 3,000 ppm or more and 8,000 ppm or less based on the total weight of the positive electrode active material. Specifically, the doping element-containing raw material may be mixed so that the content of the doping element is 3,000 ppm or more, 3,500 ppm or more, 4,000 ppm or more, 4,500 ppm or more, or 5,000 ppm or more, and 5,500 ppm or less, 6,000 ppm or less, 6,500 ppm or less, 7,000 ppm or less, 7,500 ppm or less, or 8,000 ppm or less based on the total weight of the positive electrode active material. When the mixing amount of the doping element-containing raw material is within the above range, the cycle characteristics, life characteristics, etc. of the battery can be improved, and there is an effect of improving the energy density.

[0163]

[0164] (B) Step

[0165] Thereafter, the step (B) of manufacturing a sintered product by first firing the mixture is included.

[0166] According to the present invention, the first firing is performed under an oxygen atmosphere at a temperature of 860°C or higher and 1,000°C or lower. Specifically, the first firing is performed at a temperature of 860°C or higher, or 870°C or higher, and 885°C or lower, 890°C or lower, 895°C or lower, 900°C or lower, 905°C or lower, 910°C or lower, 915°C or lower, 920°C or lower, 925°C or lower, 930°C or lower, 935°C or lower, 940°C or lower, 945°C or lower, 950°C or lower, 955°C or lower, 960°C or lower, 965°C or lower, 970°C or lower, 975°C or lower, 980°C or lower, 985°C or lower, 990°C or lower, 995°C or lower, or 1,000°C or lower. By performing the first firing under an oxygen atmosphere, the oxygen required for the reaction can be sufficiently supplied, and by performing it within the above temperature range, a fired product having excellent structural stability in the form of a single particle can be formed. On the other hand, if the first firing is not performed under an oxygen atmosphere, there is a problem that the oxygen required for the reaction is not sufficiently supplied, and if the first firing is performed at a temperature lower than 860°C, there is a problem that the heat energy required for forming the single particle form is not sufficiently supplied, and if the first firing is performed at a temperature higher than 1,000°C, there is a problem that over-firing occurs and the positive electrode active material deteriorates.

[0167]

[0168] (C) Step

[0169] Thereafter, a step (C) is included in which a lithium (Li)-containing raw material is mixed into the above-mentioned sintered product and a second sintering is performed to produce a lithium composite transition metal oxide.

[0170] The above lithium (Li)-containing raw material may be the same as or different from the lithium (Li)-containing raw material of step (A), and is not particularly limited.

[0171] According to the present invention, the secondary firing is performed under an oxygen atmosphere at a temperature of 700°C or higher and 990°C or lower. Specifically, the secondary firing is performed at a temperature of 700°C or higher, 710°C or higher, 720°C or higher, 730°C or higher, 740°C or higher, 750°C or higher, 760°C or higher, 770°C or higher, 780°C or higher, 790°C or higher, 800°C or higher, 810°C or higher, or 820°C or higher, and 830°C or lower, 840°C or lower, or 850°C or lower, 860°C or lower, 870°C or lower, 880°C or lower, 890°C or lower, 900°C or lower, 910°C or lower, 920°C or lower, 930°C or lower, 940°C or lower, 950°C or lower, 960°C or lower, 970°C or lower, 980°C or lower, or 990°C or lower. By performing the secondary firing under an oxygen atmosphere, the oxygen required for the reaction can be sufficiently supplied. In addition, by performing the secondary firing within the above temperature range, there is an effect of reducing the rock salt phase on the surface of the fired product by inserting lithium into the fired product. On the other hand, if the secondary firing is not performed under an oxygen atmosphere, there is a problem that the oxygen required for the reaction is not sufficiently supplied, and if the secondary firing is performed at a temperature below 700°C, there is a problem that the thermal energy required for inserting lithium into the fired product is not sufficiently supplied, and if the secondary firing is performed at a temperature exceeding 990°C, there is a problem that over-firing occurs and the positive electrode active material deteriorates.

[0172] According to the present invention, the first firing is performed at a higher temperature than the second firing. In this case, a single particle form is produced in the first firing, and lithium is inserted in the second firing, so that a lithium composite transition metal oxide in the single particle form and with a small rock salt phase can be produced. If the second firing is performed at a higher temperature than the first firing, there is a problem of over-firing occurring, resulting in deterioration of the positive electrode active material.

[0173] According to one embodiment of the present invention, after the step (C), the method may further include: (D) mixing the lithium composite transition metal oxide with a coating element-containing raw material including at least one coating element selected from the group consisting of Y, Zr, B, C, F, Mg, Si, P, Ca, Sc, Ti, V, Sr, Nb, Mo, Ba, La, Hf, Ta, W, Bi, Ce, Sm, and Gd to prepare a mixture; and (E) heat-treating the mixture at a temperature of 200°C or higher and 900°C or lower. In this case, the coating portion formed on the lithium composite transition metal oxide blocks contact with the electrolyte, so that side reactions between the positive electrode active material and the electrolyte can be reduced.

[0174] The above-mentioned coating element-containing raw material may be at least one selected from the group consisting of oxides, carbonates, nitrates, hydroxides, oxyhydroxides, and halides containing the coating element, and a mixture of one or more of these may be used. Considering the ease of raw material supply, specifically, Co(OH)2 and Al(OH)3 may be used.

[0175] In addition, the raw material containing the coating element may be mixed so that the coating element content is 10,000 ppm or more and 15,000 ppm or less with respect to the total weight of the positive electrode active material. Specifically, the coating element-containing raw material contains the coating element in an amount of 10,000 ppm or more, 10,100 ppm or more, 10,200 ppm or more, 10,300 ppm or more, 10,400 ppm or more, 10,500 ppm or more, 10,600 ppm or more, 10,700 ppm or more, 10,800 ppm or more, 10,900 ppm or more, 11,000 ppm or more, 11,100 ppm or more, 11,200 ppm or more, 11,300 ppm or more, 11,400 ppm or more, 11,500 ppm or more, 11,600 ppm or more, 11,700 ppm or more, 11,800 ppm or more, 11,900 ppm or more, based on the total weight of the positive electrode active material. 12,000 ppm or more, 12,100 ppm or more, 12,300 ppm or more, 12,400 ppm or more, 12,500 ppm or more, 12,600 ppm or more, 12,700 ppm or more, 12,800 ppm or more, 12,900 ppm or more, 13,000 ppm or more, 13,100 ppm or more, 13,200 ppm or more, 13,300 ppm or more, or 13,400 ppm or more, and 13,500 ppm or less, 13,600 ppm or less, 13,700 ppm or less, 13,800 ppm or less, 13,900 ppm or less, 14,000 ppm or less, 14,100 ppm or less, 14,200 ppm or less, It may be 14,300 ppm or less, 14,400 ppm or less, 14,500 ppm or less, 14,600 ppm or less, 14,700 ppm or less, 14,800 ppm or less, 14,900 ppm or less, or 15,000 ppm or less. When the raw material containing the coating element is within the above range, there is an effect of improving the output characteristics without lowering the resistance characteristics of the battery.

[0176] Meanwhile, it may include a step of heat-treating the mixture at a temperature of 200°C or higher and 900°C or lower. Specifically, it may include a step of heat-treating the mixture at a temperature of 200°C or higher, 300°C or higher, 400°C or higher, 500°C or higher, 600°C or higher, or 700°C or higher, and 800°C or lower, or 900°C or lower. When the heat-treating temperature is within the above range, the raw material containing the coating element can be effectively melted, thereby forming a coating portion containing the coating element on the lithium composite transition metal oxide.

[0177]

[0178] anode

[0179] Next, the anode according to the present invention will be described.

[0180] The positive electrode according to the present invention comprises a positive electrode active material comprising a lithium composite transition metal oxide in the form of single particles containing nickel, manganese, cobalt and aluminum, and satisfies at least one of the following conditions 3 and 4.

[0181] [Condition 3] The average particle size reduction rate (χ') calculated by the following equation (3) is 16.00% or less;

[0182] Equation (3) Average particle size reduction rate (χ') [%] =

[0183] In the above equation (3), D' 50 is the particle size [㎛] corresponding to 50% of the volume cumulative distribution according to the particle size of the positive electrode active material, and D' A is the particle size [㎛] corresponding to 50% of the cumulative volume distribution according to the particle size of the positive electrode active material measured by separating the positive electrode active material contained in the positive electrode after applying force to the positive electrode until the porosity becomes 20%.

[0184] [Condition 4] The differential incidence rate (φ') calculated by the following equation (4) is 0.0550% or less;

[0185] Equation (4) Differential occurrence rate (φ')[%] =

[0186] In the above equation (4), S' A S' is the total area under the line in the graph showing the cumulative volume distribution according to the particle size of the positive electrode active material measured by separating the positive electrode active material contained in the positive electrode after applying force to the positive electrode until the porosity becomes 20%, and B is the area under the line in the graph above where the particle size of the positive electrode active material is 1㎛ or less.

[0187]

[0188] The positive electrode according to the present invention has the effect of improving the structural stability of the positive electrode by including a positive electrode active material comprising a lithium composite transition metal oxide in the form of a single particle containing nickel, manganese, cobalt, and aluminum. In particular, since aluminum improves the particle structural stability and the stability of the internal crystal lattice of the positive electrode active material, when aluminum is included, the particle strength of the positive electrode active material within the positive electrode is improved, so that the phenomenon of particle breakage is reduced when force is applied. Accordingly, since side reactions between the positive electrode active material and the electrolyte occur relatively little, the life characteristics of a battery including the positive electrode are excellent while maintaining energy density.

[0189] Meanwhile, when the positive electrode includes a lithium composite transition metal oxide, which is a secondary particle, unlike the present invention, there is a problem that the particles are easily broken during the electrode rolling process, and the particle strength of the positive electrode active material is poor. In particular, in the case of a lithium composite transition metal oxide containing a high nickel content, there is a problem that the structural stability of the positive electrode is poor due to the particle breaking phenomenon, and in this case, side reactions between the lithium composite transition metal oxide and the electrolyte may increase, and the physical properties of the battery may be poor. In addition, when the positive electrode does not include a positive electrode active material containing a lithium composite transition metal oxide containing nickel, manganese, cobalt, and aluminum unlike the present invention, specifically, when the lithium composite transition metal oxide does not include aluminum, the positive electrode active material particles are excessively broken during rolling for battery manufacturing, so the structural stability of the positive electrode is poor, and there is a problem that the capacity characteristics and life characteristics of the battery are poor.

[0190]

[0191] Below, each condition, Condition 3 and Condition 4, is explained in detail.

[0192]

[0193] [Condition 3]

[0194] According to the present invention, the average particle size reduction rate (χ') calculated by the following equation (3) is 16.00% or less.

[0195] Equation (3) Average particle size reduction rate (χ') [%] =

[0196] In the above equation (3), D' 50 is the particle size [㎛] corresponding to 50% of the volume cumulative distribution according to the particle size of the positive electrode active material, and D' A It is the particle size [㎛] corresponding to 50% of the cumulative volume distribution according to the particle size of the positive electrode active material measured by separating the positive electrode active material contained in the positive electrode after applying force to the positive electrode until the porosity becomes 20%.

[0197] In the present invention, the concept of average particle size reduction rate (χ') was used to evaluate and quantitatively represent the degree of cathode active material particle breakage before and after applying force to the cathode including the cathode active material. The average particle size reduction rate (χ') is an indicator of how much the average particle size of the cathode active material contained in the cathode changes after applying force compared to the cathode active material contained in the cathode before applying force to the cathode until the porosity becomes 20%.

[0198] Specifically, the above D' 50 The particle size corresponding to 50% of the volume cumulative distribution according to the particle size of the positive electrode active material contained in the positive electrode without applying force may be the same as the particle size corresponding to 50% of the volume cumulative distribution according to the particle size of the positive electrode active material before manufacturing the positive electrode. The above D' A is the particle size corresponding to 50% of the volume cumulative distribution according to the particle size of the positive electrode active material measured by separating the positive electrode active material contained in the positive electrode after applying force to the positive electrode until the porosity becomes 20%, and the above D' A A positive electrode including a positive electrode active material is manufactured, a force is applied to the positive electrode until the porosity becomes 20%, the positive electrode is sintered to remove materials other than the positive electrode active material, and only the positive electrode active material is separated. The positive electrode active material is then introduced into a laser diffraction particle size measuring device and measured.

[0199] The force applied to achieve a porosity of 20% is similar to the rolling pressure level during positive electrode manufacturing, and thus can be understood as a more clear standard for evaluating particle breakage during battery manufacturing.

[0200] The low average particle size reduction rate (χ') above means that when a certain force is applied to the positive electrode containing the positive electrode active material, the phenomenon of breaking of the positive electrode active material particles within the positive electrode occurs less, and thus the particle size reduction is low.

[0201] Specifically, the average particle size reduction rate (χ') may be 0.00% or more, 1.00% or more, 2.00% or more, 3.00% or more, 4.00% or more, or 5.00% or more, and may be 16.00% or less. When the average particle size reduction rate (χ') is within the above range, the particle strength of the positive electrode active material in the positive electrode is improved, so that the particle breakage phenomenon occurs less when force is applied. Accordingly, since the side reaction between the positive electrode active material and the electrolyte occurs relatively less, there is an effect of excellent life characteristics of a battery including the positive electrode while maintaining the energy density. On the other hand, when the average particle size reduction rate (χ') exceeds 16.00%, there is a problem of poor life characteristics of the battery at high temperatures.

[0202]

[0203] [Condition 4]

[0204] According to the present invention, the differential incidence rate (φ') calculated by the following equation (4) is 0.0550% or less.

[0205] Equation (4) Differential occurrence rate (φ')[%] =

[0206] In the above equation (4), S' A S' is the total area under the line in the graph showing the cumulative volume distribution according to the particle size of the positive electrode active material measured by separating the positive electrode active material contained in the positive electrode after applying force to the positive electrode until the porosity becomes 20%, and B is the area under the line in the graph above where the particle size of the positive electrode active material is 1㎛ or less.

[0207] In the present invention, the concept of fine particle generation rate (φ') was used to evaluate and quantitatively represent the degree of cathode active material particle breakage before and after applying force to the cathode containing the cathode active material. The fine particle generation rate (φ') is an indicator of the extent to which the volume of fine particles having a particle diameter of 1 μm or less in a cathode active material contained in the cathode changes relative to the total volume of the cathode active material after applying force to the cathode until the porosity reaches 20%.

[0208] The force applied to achieve a porosity of 20% is similar to the rolling pressure level during positive electrode manufacturing, and thus can be understood as a more clear standard for evaluating particle breakage during battery manufacturing.

[0209] The low occurrence rate of the above-mentioned differential powder (φ') means that when a certain force is applied to the positive electrode containing the positive electrode active material, the phenomenon of breaking of the positive electrode active material particles within the positive electrode occurs less, resulting in less occurrence of differential powder.

[0210] Specifically, the particle generation rate (φ') may be 0.0000% or more, or 0.0500% or more, and may be 0.0510% or less, 0.0520% or less, 0.0530% or less, 0.0540% or less, or 0.0550% or less. When the particle generation rate (φ') is within the above range, the particle strength of the positive electrode active material is improved, so that the particle breakage phenomenon occurs less when force is applied. Accordingly, since the side reaction between the positive electrode active material and the electrolyte occurs relatively less, there is an effect of excellent life characteristics of a battery including the positive electrode active material while maintaining the energy density. On the other hand, when the particle generation rate (φ') exceeds 0.0550%, there is a problem of poor life characteristics of the battery at high temperatures.

[0211]

[0212] The positive electrode according to the present invention comprises a positive electrode active material layer comprising the positive electrode active material according to the present invention. Specifically, the positive electrode comprises a positive electrode current collector and a positive electrode active material layer formed on the positive electrode current collector, and comprising the positive electrode active material. Since the positive electrode active material has been described above, a detailed description thereof will be omitted, and only the remaining components will be described in detail below.

[0213] The positive electrode current collector is not particularly limited as long as it is conductive and does not cause a chemical change in the battery, and for example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, etc. may be used. In addition, the positive electrode current collector may typically have a thickness of 3 µm to 500 µm, and fine unevenness may be formed on the surface of the positive electrode current collector to increase the adhesive strength of the positive electrode active material. For example, the positive electrode current collector may be used in various forms such as a film, sheet, foil, net, porous body, foam, or non-woven fabric.

[0214] The above-mentioned positive electrode active material layer may include a conductive material and a binder together with the positive electrode active material. At this time, the positive electrode active material may be included in an amount of 80 wt% to 99 wt%, more specifically 85 wt% to 98.5 wt%, based on the total weight of the positive electrode active material layer, and excellent capacity characteristics may be exhibited within this range.

[0215] The conductive material is used to provide conductivity to the electrode, and in the battery to be formed, as long as it does not cause a chemical change and has electronic conductivity, it can be used without any special restrictions. Specific examples include graphite such as natural graphite or artificial graphite; carbon-based materials such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, summer black, and carbon fiber; metal powder or metal fiber such as copper, nickel, aluminum, and silver; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives, and the like. One type alone or a mixture of two or more types of these may be used. The conductive material may be included in an amount of 0.1 wt% to 15 wt% based on the total weight of the positive electrode active material layer.

[0216] The above binder serves to improve the adhesion between positive electrode active material particles and the adhesive strength between the positive electrode active material and the current collector. Specific examples include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene butadiene rubber (SBR), fluoroelastomer, or various copolymers thereof, and one of these may be used alone or a mixture of two or more thereof. The binder may be included in an amount of 0.1 wt% to 15 wt% based on the total weight of the positive electrode active material layer.

[0217] The positive electrode can be manufactured according to a conventional positive electrode manufacturing method, except that the positive electrode active material described above is used. Specifically, the positive electrode can be manufactured by coating a composition for forming a positive electrode active material layer, which is manufactured by dissolving or dispersing the positive electrode active material and optionally a binder and a conductive material in a solvent, on a positive electrode current collector, followed by drying and rolling. At this time, the types and contents of the positive electrode active material, binder, and conductive material are as described above. Alternatively, the positive electrode can be manufactured by casting the composition for forming a positive electrode active material layer on a separate support, and then laminating the film obtained by peeling it from the support on a positive electrode current collector.

[0218] The solvent may be a solvent generally used in the relevant technical field, such as dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, or water. One of these may be used alone or a mixture of two or more thereof may be used. The amount of the solvent used is sufficient to dissolve or disperse the positive electrode active material, conductive material, and binder, taking into account the coating thickness and manufacturing yield of the slurry, and to have a viscosity that can exhibit excellent thickness uniformity when applied thereafter for manufacturing the positive electrode.

[0219]

[0220] lithium secondary battery

[0221] Next, a lithium secondary battery according to the present invention will be described.

[0222]

[0223] The present invention can manufacture an electrochemical device including the above-described positive electrode. The electrochemical device may be, specifically, a battery, a capacitor, or the like, and more specifically, a lithium secondary battery.

[0224] The lithium secondary battery specifically includes a positive electrode, a negative electrode positioned opposite the positive electrode, and a separator and electrolyte interposed between the positive electrode and the negative electrode. Since the positive electrode is the same as described above, a detailed description thereof will be omitted, and only the remaining components will be described in detail below.

[0225] In addition, the lithium secondary battery may optionally further include a battery container that houses the electrode assembly of the positive electrode, the negative electrode, and the separator, and a sealing member that seals the battery container.

[0226] In the above lithium secondary battery, the negative electrode includes a negative electrode current collector and a negative electrode active material layer positioned on the negative electrode current collector.

[0227] The negative electrode current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery, and for example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., aluminum-cadmium alloy, etc. can be used. In addition, the negative electrode current collector can typically have a thickness of 3 ㎛ to 500 ㎛, and like the positive electrode current collector, fine unevenness can be formed on the surface of the current collector to strengthen the bonding strength of the negative electrode active material. For example, it can be used in various forms such as a film, a sheet, a foil, a net, a porous body, a foam, a non-woven fabric, etc.

[0228] The above negative electrode active material layer optionally includes a binder and a conductive material together with the negative electrode active material.

[0229] As the negative electrode active material, a compound capable of reversible intercalation and deintercalation of lithium may be used. Specific examples include carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber, and amorphous carbon; metallic compounds capable of alloying with lithium such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloy, Sn alloy, or Al alloy; SiO β(0<β<2), SnO2, vanadium oxide, lithium vanadium oxide, and other metal oxides capable of doping and dedoping lithium; or composites containing the above metallic compounds and carbonaceous materials, such as Si-C composites or Sn-C composites, and any one or a mixture of two or more of these may be used. In addition, a metallic lithium thin film may be used as the negative electrode active material. In addition, both low-crystalline carbon and high-crystalline carbon may be used as the carbonaceous material. Representative examples of low-crystalline carbon include soft carbon and hard carbon, and representative examples of high-crystalline carbon include natural graphite or artificial graphite in the form of amorphous, plate-like, flaky, spherical, or fiber-like forms, Kish graphite, pyrolytic carbon, mesophase pitch-based carbon fiber, meso-carbon microbeads, mesophase pitches, and high-temperature calcined carbon such as petroleum or coal tar pitch derived cokes.

[0230] The above negative electrode active material may be included in an amount of 80% to 99% by weight based on the total weight of the negative electrode active material layer.

[0231] The above binder is a component that assists in bonding between the conductive material, the active material, and the current collector, and can typically be added in an amount of 0.1 wt% to 10 wt% based on the total weight of the negative electrode active material layer. Examples of such binders include polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene-butadiene rubber, nitrile-butadiene rubber, fluororubber, and various copolymers thereof.

[0232] The conductive agent is a component for further improving the conductivity of the negative electrode active material, and may be added in an amount of 10 wt% or less, specifically, 5 wt% or less, based on the total weight of the negative electrode active material layer. The conductive agent is not particularly limited as long as it has conductivity and does not cause a chemical change in the battery, and examples thereof include graphite such as natural graphite or artificial graphite; carbon black such as acetylene black, Ketjen black, channel black, furnace black, lamp black, and thermal black; conductive fibers such as carbon fiber or metal fiber; metal powders such as fluorocarbon, aluminum, and nickel powder; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives.

[0233] The negative electrode active material layer may be manufactured by applying and drying a composition for forming a negative electrode active material layer prepared by dissolving or dispersing a negative electrode active material, and optionally a binder and a conductive material in a solvent, on a negative electrode current collector, or by casting the composition for forming a negative electrode active material layer on a separate support, and then laminating the film obtained by peeling it off from the support on a negative electrode current collector.

[0234] Meanwhile, in the lithium secondary battery, the separator separates the negative electrode and the positive electrode and provides a passage for lithium ions to move. Any separator commonly used in lithium secondary batteries can be used without special restrictions, and in particular, one having low resistance to ion movement of the electrolyte and excellent electrolyte moisture absorption capacity is preferable. Specifically, a porous polymer film, for example, a porous polymer film made of a polyolefin polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, and an ethylene / methacrylate copolymer, or a laminated structure of two or more layers thereof, 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 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.

[0235] In addition, examples of the electrolyte used in the present invention include, but are not limited to, organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel-type polymer electrolytes, solid inorganic electrolytes, and molten inorganic electrolytes that can be used in the manufacture of lithium secondary batteries.

[0236] Specifically, the electrolyte may include an organic solvent and a lithium salt.

[0237] As the organic solvent, any solvent that can serve as a medium through which ions involved in the electrochemical reaction of the battery can move may be used without particular limitation. Specifically, the organic solvent includes ester solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, and ε-caprolactone; ether solvents such as dibutyl ether or tetrahydrofuran; ketone solvents such as cyclohexanone; aromatic hydrocarbon solvents such as benzene and fluorobenzene; carbonate solvents such as dimethylcarbonate (DMC), diethylcarbonate (DEC), ethylmethylcarbonate (EMC), ethylene carbonate (EC), and propylene carbonate (PC); Alcohol solvents such as ethyl alcohol, isopropyl alcohol, etc.; nitriles such as R-CN (R is a linear, branched, or cyclic hydrocarbon group having 2 to 20 carbon atoms and may include a double-bonded aromatic ring or an ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; or sulfolanes, etc. can be used. Among these, carbonate solvents are preferable, and a mixture of a cyclic carbonate (e.g., ethylene carbonate or propylene carbonate) having high ionic conductivity and high dielectric constant that can improve the charge / discharge performance of a battery and a low-viscosity linear carbonate compound (e.g., ethyl methyl carbonate, dimethyl carbonate, or diethyl carbonate) is more preferable.In this case, the performance of the electrolyte may be improved when the cyclic carbonate and the chain carbonate are mixed and used in a volume ratio of about 1:1 to about 1:9.

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

[0239] In addition to the electrolyte components, the electrolyte may further include one or more additives, such as haloalkylene carbonate compounds such as difluoroethylene carbonate, pyridine, triethylphosphite, triethanolamine, cyclic ethers, ethylene diamine, n-glyme, hexaphosphoric acid triamide, nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinones, N,N-substituted imidazolidines, ethylene glycol dialkyl ethers, ammonium salts, pyrrole, 2-methoxyethanol, or aluminum trichloride, for the purpose of improving the life characteristics of the battery, suppressing battery capacity decrease, and improving the discharge capacity of the battery. At this time, the additive may be included in an amount of 0.1 to 10 wt%, specifically, 0.1 to 5 wt%, based on the total weight of the electrolyte.

[0240] As described above, a lithium secondary battery including a cathode active material according to the present invention exhibits excellent life characteristics and capacity characteristics, and is therefore useful in portable devices such as mobile phones, laptop computers, and digital cameras, and electric vehicles such as hybrid electric vehicles (HEVs).

[0241] Accordingly, according to another embodiment of the present invention, a battery module including the lithium secondary battery as a unit cell and a battery pack including the same are provided.

[0242] 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.

[0243] 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.

[0244] 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.

[0245]

[0246] 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.

[0247]

[0248] Examples and Comparative Examples

[0249] Example 1

[0250] Ni(OH)2(average particle diameter (D 50 ) : 3㎛), Co(OH)2 (average particle diameter (D 50 ) : 0.2㎛), MnO2 (average particle diameter (D 50 ) : 0.3㎛) and Al(OH)3 (average particle diameter (D 50 ) : 1㎛) were mixed so that the molar ratio of Ni:Mn:Co:Al was 88.475:8:3:0.525, then LiOH·H2O was dry mixed so that the molar ratio of Li:(Ni+Co+Mn+Al) was 1.03:1, ZrO2 was mixed so that Zr was 1,500 ppm with respect to the total weight of the positive electrode active material, and Y2O3 was mixed so that Y was 1,000 ppm with respect to the total weight of the positive electrode active material, thereby preparing a mixture. The mixture was first fired under an oxygen atmosphere at a temperature of 885°C to prepare a fired product.

[0251] LiOH·H2O is mixed in the above-mentioned sintered product so that the molar ratio of total Li:(Ni+Co+Mn+Al) is 1.04:1, and the second sintering is performed under an oxygen atmosphere and a temperature of 820℃ to obtain a single particle form, and Li 1.04 Ni 0.88475 Mn 0.08 Co 0.03 Al 0.005 Zr 0.00015 Y 0.0001 A lithium composite transition metal oxide having a composition represented by O2 was prepared. At this time, the lithium composite transition metal oxide contains Al in an amount of 5,000 ppm based on the total weight of the positive electrode active material.

[0252] The lithium composite transition metal oxide was mixed with Co(OH)2 and Al(OH)3, and heat-treated at a temperature of 700°C to manufacture a positive electrode active material including the lithium composite transition metal oxide and a coating portion including Co and Al. At this time, the Co(OH)2 was mixed so that cobalt (Co) was 13,000 ppm based on the total weight of the positive electrode active material, and the Al(OH)3 was mixed so that aluminum (Al) was 500 ppm based on the total weight of the positive electrode active material.

[0253]

[0254] Example 2

[0255] Ni(OH)2(average particle diameter (D 50 ): Ni(OH)2 (average particle size (D)) exists in fine particles (<1㎛) rather than in particles (3㎛) 50 ): 4㎛) and the point that the first firing was performed under an oxygen atmosphere and a temperature of 870°C instead of 885°C to manufacture the sintered product, and a positive electrode active material including a lithium composite transition metal oxide and a coating portion including Co and Al was manufactured in the same manner as in Example 1.

[0256]

[0257] Example 3

[0258] A positive electrode active material including a lithium composite transition metal oxide and a coating portion including Co and Al was manufactured in the same manner as in Example 1, except that the mixture was first fired in an oxygen atmosphere at a temperature of 870°C instead of 885°C to manufacture a sintered product.

[0259]

[0260] Example 4

[0261] Co(OH)2(average particle size (D 50 ) :A positive electrode active material including a lithium composite transition metal oxide and a coating portion including Co and Al was manufactured in the same manner as in Example 1, except that Co3O4 was used instead of Co3O4 (0.2 μm) and the mixture was first fired under an oxygen atmosphere at a temperature of 870°C instead of 885°C to manufacture a sintered product.

[0262]

[0263] Example 5

[0264] The positive electrode active material, conductive agent (carbon black), and binder (PVDF) manufactured in Example 1 were added in a weight ratio of 95:2:3 to manufacture a positive electrode slurry (solid content: 95 wt%). The positive electrode slurry was applied to a 15.00 ㎛ thick aluminum (Al) thin film as a positive electrode current collector, and dried at 130°C for 20 minutes to manufacture a positive electrode.

[0265]

[0266] Example 6

[0267] The positive electrode active material, conductive agent (carbon black), and binder (PVDF) manufactured in Example 2 were added in a weight ratio of 95:2:3 to manufacture a positive electrode slurry (solid content: 95 wt%). The positive electrode slurry was applied to a 15.00 ㎛ thick aluminum (Al) thin film as a positive electrode current collector, and dried at 130°C for 20 minutes to manufacture a positive electrode.

[0268]

[0269] Example 7

[0270] The positive electrode active material, conductive agent (carbon black), and binder (PVDF) manufactured in Example 3 were added in a weight ratio of 95:2:3 to manufacture a positive electrode slurry (solid content: 95 wt%). The positive electrode slurry was applied to a 15.00 ㎛ thick aluminum (Al) thin film as a positive electrode current collector, and dried at 130°C for 20 minutes to manufacture a positive electrode.

[0271]

[0272] Example 8

[0273] The positive electrode active material, conductive agent (carbon black), and binder (PVDF) manufactured in Example 4 were added in a weight ratio of 95:2:3 to manufacture a positive electrode slurry (solid content: 95 wt%). The positive electrode slurry was applied to a 15.00 ㎛ thick aluminum (Al) thin film as a positive electrode current collector, and dried at 130°C for 20 minutes to manufacture a positive electrode.

[0274]

[0275] Comparative Example 1

[0276] Ni rather than dry mixing of raw materials 0.89 Co 0.03 Mn 0.08 (OH)2 and Al(OH)3 (average particle size (D 50 ) : A positive electrode active material including a lithium composite transition metal oxide and a coating portion including Co and Al was manufactured in the same manner as in Example 1, except that the mixture was prepared by mixing (Ni+Co+Mn):Al in a molar ratio of 99:1 and then dry-mixing LiOH·H2O in a molar ratio of Li:(Ni+Co+Mn+Al) of 1.03:1.

[0277]

[0278] Comparative Example 2

[0279] A positive electrode slurry (solid content: 95 wt%) was prepared by adding the positive electrode active material, conductive agent (carbon black), and binder (PVDF) manufactured in Comparative Example 1 at a weight ratio of 95:2:3. The positive electrode slurry was applied to a 15.00 ㎛ thick aluminum (Al) thin film as a positive electrode current collector, and dried at 130°C for 20 minutes to manufacture a positive electrode.

[0280]

[0281] Comparative Example 3

[0282] Ni(OH)2(average particle diameter (D 50 ) : 3㎛), Co(OH)2 (average particle diameter (D50 ): 0.2㎛), MnO2 (average particle diameter (D 50 ) : 0.3㎛) were mixed so that the molar ratio of Ni:Mn:Co was 88.975:8:3, then LiOH·H2O was dry mixed so that the molar ratio of Li:(Ni+Co+Mn) was 1.03:1, ZrO2 was mixed so that Zr was 1,500 ppm with respect to the total weight of the positive electrode active material, and Y2O3 was mixed so that Y was 1,000 ppm with respect to the total weight of the positive electrode active material, thereby preparing a mixture. The mixture was first fired under an oxygen atmosphere at a temperature of 850°C to prepare a fired product.

[0283] LiOH·H2O is mixed in the above-mentioned sintered product so that the molar ratio of total Li:(Ni+Co+Mn) is 1.04:1, and the second sintering is performed under an oxygen atmosphere and a temperature of 820℃ to obtain a single particle form, and Li 1.04 Ni 0.88975 Mn 0.08 Co 0.03 Zr 0.00015 Y 0.0001 A lithium composite transition metal oxide having a composition represented by O2 was prepared.

[0284] The lithium composite transition metal oxide was mixed with Co(OH)2 and Al(OH)3, and heat-treated at a temperature of 700°C to manufacture a positive electrode active material including the lithium composite transition metal oxide and a coating portion including Co and Al. At this time, the Co(OH)2 was mixed so that cobalt (Co) was 13,000 ppm based on the total weight of the positive electrode active material, and the Al(OH)3 was mixed so that aluminum (Al) was 500 ppm based on the total weight of the positive electrode active material.

[0285]

[0286] Comparative Example 4

[0287] A positive electrode slurry (solid content: 95 wt%) was prepared by adding the positive electrode active material, conductive agent (carbon black), and binder (PVDF) manufactured in Comparative Example 3 at a weight ratio of 95:2:3. The positive electrode slurry was applied to a 15.00 ㎛ thick aluminum (Al) thin film as a positive electrode current collector, and dried at 130°C for 20 minutes to manufacture a positive electrode.

[0288]

[0289] Comparative Example 5

[0290] Ni(OH)2(average particle diameter (D 50 ) : 3㎛), Co(OH)2 (average particle diameter (D 50 ): 0.2㎛), MnO2 (average particle diameter (D 50 ) : 0.3㎛) and Al(OH)3 (average particle diameter (D 50 ) : 1㎛) were mixed so that the molar ratio of Ni:Mn:Co:Al was 88.475:8:3:0.5, then LiOH·H2O was dry mixed so that the molar ratio of Li:(Ni+Co+Mn) was 1.03:1, ZrO2 was mixed so that Zr was 1,500 ppm with respect to the total weight of the positive electrode active material, and Y2O3 was mixed so that Y was 1,000 ppm with respect to the total weight of the positive electrode active material, thereby preparing a mixture. The mixture was first fired under an oxygen atmosphere at a temperature of 850°C to prepare a fired product.

[0291] LiOH·H2O is mixed in the above-mentioned sintered product so that the molar ratio of total Li:(Ni+Co+Mn) is 1.04:1, and the second sintering is performed under an oxygen atmosphere and a temperature of 820℃ to obtain a single particle form, and Li 1.04 Ni 0.88475 Mn 0.08 Co 0.03 Al 0.005 Zr 0.00015 Y 0.0001 A lithium composite transition metal oxide having a composition represented by O2 was prepared.

[0292] The lithium composite transition metal oxide was mixed with Co(OH)2 and Al(OH)3, and heat-treated at a temperature of 700°C to manufacture a positive electrode active material including the lithium composite transition metal oxide and a coating portion including Co and Al. At this time, the Co(OH)2 was mixed so that cobalt (Co) was 13,000 ppm based on the total weight of the positive electrode active material, and the Al(OH)3 was mixed so that aluminum (Al) was 500 ppm based on the total weight of the positive electrode active material.

[0293]

[0294] Comparative Example 6

[0295] A positive electrode slurry (solid content: 95 wt%) was prepared by adding the positive electrode active material, conductive agent (carbon black), and binder (PVDF) manufactured in Comparative Example 5 at a weight ratio of 95:2:3. The positive electrode slurry was applied to a 15.00 ㎛ thick aluminum (Al) thin film as a positive electrode current collector, and dried at 130°C for 20 minutes to manufacture a positive electrode.

[0296]

[0297] Experimental example

[0298] Experimental Example 1: Evaluation of Positive Electrode Active Material 1

[0299] For each of the positive electrode active materials manufactured in the above examples and comparative examples, SEM images were obtained using a scanning electron microscope (SEM) (FEI, Quanta), and these are shown in FIGS. 1 to 7.

[0300]

[0301] Figure 1 is a SEM image of the positive electrode active material manufactured in Example 1.

[0302] Figure 2 is an SEM image of the positive electrode active material manufactured in Example 2.

[0303] Figure 3 is an SEM image of the positive electrode active material manufactured in Example 3.

[0304] Figure 4 is an SEM image of the positive electrode active material manufactured in Example 4.

[0305] Figure 5 is an SEM image of the positive electrode active material manufactured in Comparative Example 1.

[0306] Figure 6 is an SEM image of the positive electrode active material manufactured in Comparative Example 3.

[0307] Figure 7 is an SEM image of the positive electrode active material manufactured in Comparative Example 5.

[0308]

[0309] Through Figures 1 to 4, it was confirmed that the positive electrode active materials manufactured in Examples 1 to 4 were in the form of single particles. Specifically, it was confirmed that the positive electrode active materials were in the form of aggregates of 1 to 20 primary particles.

[0310] Since the positive electrode active materials manufactured in Examples 1 to 4 include a lithium composite transition metal oxide and a coating formed on the lithium composite oxide, it can be expected that the lithium composite transition metal oxide is also in the form of a positive electrode active material. Specifically, it can be expected that the lithium composite transition metal oxide is in the form of an agglomeration of 1 to 20 primary particles.

[0311] And, through Figures 1 to 4, it was confirmed that the positive electrode active materials manufactured in Examples 1 to 4 had an island-type coating. Specifically, it was confirmed in the SEM image that the surface of the positive electrode active material particles was not smooth but had unevenness, and from this, it was confirmed that the coating was not a thin film but an island-type.

[0312]

[0313] Experimental Example 2: Evaluation of Positive Electrode Active Material 2

[0314] For each of the positive electrode active materials manufactured in the above examples and comparative examples, a graph showing the cumulative volume distribution according to the particle size of the positive electrode active material before and after applying force was obtained using PSA (MICROTRAC, MICROTRAC S3500), and this is shown in Figs. 8 to 14. In addition, the average particle size (D 50 ) were measured, and the average particle size reduction rate (χ) and differential particle generation rate (φ) were calculated, and shown in Table 1 below.

[0315]

[0316] Specifically, for each of the positive electrode active materials manufactured in the examples and comparative examples, 2 g of the positive electrode active material was divided into small portions and filled tightly into a cylindrical holder having an outer diameter of 50.5 mm and an inner diameter of 13 mm, and then a force of 9000 kgf was applied for 20 seconds, and then, using an acoustic mixer (Horiba, LabRAM II), it was crushed at a speed of 100 G for 2 minutes, and then using a PSA (MICROTRAC, MICROTRAC S3500), D A Measure [㎛], S A and S B was calculated. And, the particle size (D) corresponding to 50% of the volume cumulative distribution according to the particle size of the positive electrode active material 50 ) for D 50 and D A Calculate the percentage of difference (average particle size reduction rate (χ) [%]) of S A S for B The percentage (differential occurrence rate (φ) [%]) was calculated and shown in Table 1 below.

[0317]

[0318] Figure 8 is a graph showing the cumulative volume distribution according to the particle size of the positive electrode active material manufactured in Example 1.

[0319] Figure 9 is a graph showing the cumulative volume distribution according to the particle size of the positive electrode active material manufactured in Example 2.

[0320] Figure 10 is a graph showing the cumulative volume distribution according to the particle size of the positive electrode active material manufactured in Example 3.

[0321] Figure 11 is a graph showing the cumulative volume distribution according to the particle size of the positive electrode active material manufactured in Example 4.

[0322] Figure 12 is a graph showing the cumulative volume distribution according to the particle size of the positive electrode active material manufactured in Comparative Example 1.

[0323] Figure 13 is a graph showing the cumulative volume distribution according to the particle size of the positive electrode active material manufactured in Comparative Example 3.

[0324] Figure 14 is a graph showing the cumulative volume distribution according to the particle size of the positive electrode active material manufactured in Comparative Example 5.

[0325]

[0326] Average particle diameter (D 50 )[㎛]Average particle size reduction rate(χ)[%]Differential particle generation rate(φ)[%]Example 12.9712.710.0003Example 22.6815.260.0630Example 32.7222.642.7770Example 42.7024.892.8860Comparative example 12.9939.097.1290Comparative example 33.6971.6522.8220Comparative example 53.7057.309.0940

[0327] Through FIGS. 8 to 14 and Table 1, it was confirmed that the positive electrode active materials manufactured in Examples 1 to 4 had an average particle size reduction rate (χ) calculated by Equation (1) described herein of 35.00% or less, and a differential particle generation rate (φ) calculated by Equation (2) described herein of 6.0000% or less, i.e., they satisfied Conditions 1 and 2 described herein. On the other hand, it was confirmed that the positive electrode active materials manufactured in Comparative Example 1 using a wet mixing method for manufacturing a precursor, Comparative Example 3 in which the aluminum (Al)-containing raw material was not mixed and the first firing was performed at less than 860°C, and Comparative Example 5 in which the first firing was performed at less than 860°C had an average particle size reduction rate (χ) calculated by (1) described herein of more than 35.00%, and a fine particle generation rate (φ) calculated by Equation (2) described herein of more than 6.0000%, that is, they did not satisfy both Condition 1 and Condition 2 described herein. In this regard, it was confirmed that when a wet mixing method for manufacturing a precursor was used, or when the aluminum (Al)-containing raw material was not mixed, or when the first firing was performed at less than 860°C, the particle structure stability and the stability of the internal crystal lattice were inferior, and single particle formation did not sufficiently progress.

[0328]

[0329] And, the positive electrode active materials manufactured in Examples 1 to 4 had an average particle diameter (D 50 ) was confirmed to be 1.00㎛ or more and 15.00㎛ or less.

[0330]

[0331] Experimental Example 3: Bipolar Evaluation

[0332] For each positive electrode manufactured in the above examples and comparative examples, a graph showing the cumulative volume distribution according to the particle size of the positive electrode active material in the positive electrode before and after applying force was obtained using PSA (MICROTRAC, MICROTRAC S3500), and this is shown in Figs. 15 to 21. In addition, the average particle size reduction rate (χ') and the differential particle generation rate (φ') were calculated and shown in Table 2 below.

[0333]

[0334] Specifically, for each positive electrode manufactured in the examples and comparative examples, force was applied to the positive electrode until the porosity became 20%, and then the positive electrode was placed in a sintering furnace and sintered at 500°C for 1 hour in an air atmosphere. Materials other than the positive electrode active material were removed, and only the positive electrode active material was separated, and then, using an acoustic mixer (Horiba, LabRAM II), it was crushed at a speed of 100 G for 2 minutes, and then using a PSA (MICROTRAC, MICROTRAC S3500), D' A Measure [㎛] and S' A and S' B was calculated. And, the particle size (D') corresponding to 50% of the volume cumulative distribution according to the particle size of the positive electrode active material 50 ) for D' 50 and D' A Calculate the percentage of difference (average particle size reduction rate (χ') [%]) and S' A S' for B The percentage (differential occurrence rate (φ') [%]) was calculated and shown in Table 2 below. For reference, the above D' 50 Silver D 50 It is the same as .

[0335]

[0336] Figure 15 is a graph showing the cumulative volume distribution according to the particle size of the positive electrode including the positive electrode active material manufactured in Example 5.

[0337] Figure 16 is a graph showing the cumulative volume distribution according to the particle size of the positive electrode including the positive electrode active material manufactured in Example 6.

[0338] Figure 17 is a graph showing the cumulative volume distribution according to the particle size of the positive electrode including the positive electrode active material manufactured in Example 7.

[0339] Figure 18 is a graph showing the cumulative volume distribution according to the particle size of the positive electrode including the positive electrode active material manufactured in Example 8.

[0340] Figure 19 is a graph showing the cumulative volume distribution according to the particle size of the positive electrode including the positive electrode active material manufactured in Comparative Example 2.

[0341] Figure 20 is a graph showing the cumulative volume distribution according to the particle size of the positive electrode including the positive electrode active material manufactured in Comparative Example 4.

[0342] Figure 21 is a graph showing the cumulative volume distribution according to the particle size of the positive electrode including the positive electrode active material manufactured in Comparative Example 6.

[0343]

[0344] Average particle size reduction rate (χ') [%] Differential particle generation rate (φ') [%] Example 56.79 0.0000 Example 65.56 0.0000 Example 78.39 0.0000 Example 815.59 0.0510 Comparative example 226.60 0.0620 Comparative example 451.76 5.6520 Comparative example 648.76 4.4070

[0345] Through Figs. 15 to 21 and Table 2, it was confirmed that the positive electrodes manufactured in Examples 5 to 8 had an average particle size reduction rate (χ') calculated by Equation (3) described herein of 16.00% or less, and a fine powder generation rate (φ') calculated by Equation (4) described herein of 0.0550% or less, i.e., conditions 3 and 4 described herein were satisfied. On the other hand, the positive electrodes manufactured in Comparative Example 2 including Comparative Example 1 using a wet mixing method for manufacturing a precursor, Comparative Example 4 including Comparative Example 3 in which the first firing was performed at less than 860°C without mixing aluminum (Al)-containing raw materials, and Comparative Example 6 including Comparative Example 5 in which the first firing was performed at less than 860°C had an average particle size reduction rate (χ') calculated by Equation (3) described herein of more than 16.00%, and a fine powder generation rate (φ') calculated by Equation (4) described herein of 0.0550% or less. It was confirmed that the incidence rate (φ') exceeded 0.0550%, i.e., neither condition 3 nor condition 4 described in this specification was satisfied.

[0346] In relation to this, in the case of a positive electrode including a positive electrode active material manufactured by using a wet mixing method for manufacturing a precursor, not mixing aluminum (Al)-containing raw materials, or performing primary calcination at less than 860°C, it was confirmed that the structural stability of the positive electrode particles and the stability of the internal crystal lattice were inferior, and the structural stability of the positive electrode was also inferior because single particle formation did not progress sufficiently.

[0347]

[0348] Experimental Example 4: Battery Characteristics Evaluation

[0349] Coin-type half-cell manufacturing

[0350] Each of the positive electrodes manufactured in the above examples and comparative examples was rolled to have a porosity of 20% to manufacture a positive electrode.

[0351] A lithium metal electrode (Li metal disk) was used as the negative electrode, and an electrode assembly was manufactured by interposing a separator between the positive and negative electrodes, which was then placed inside a battery case, and an electrolyte was injected into the case to manufacture a coin-type half-cell. At this time, the electrolyte used was an electrolyte in which 1 M LiPF6 was dissolved in an organic solvent containing ethylene carbonate: ethyl methyl carbonate: diethyl carbonate in a volume ratio of 3:3:4.

[0352] After manufacturing the coin-type half-cell, the battery characteristics were evaluated using the following method.

[0353]

[0354] Using the above half-cell, the battery was charged (0.1C, cut-off current: 0.05C) to 4.25 V at 25°C using the CC-CV method, and then discharged (0.1C) to 3.0 V using the CC method, and the charge / discharge capacity (mAh / g) at this time was measured. The measured charge / discharge capacity (mAh / g) is shown in Table 3 below.

[0355]

[0356] Using the above half-cell, a cycle of charging (0.5C, cut-off current: 0.05C) to 4.25 V at 45°C using the CC-CV method and discharging (1.0C) to 3.0 V using the CC method was counted as one cycle, and a total of 50 cycles of charging and discharging were repeated. After measuring the discharge capacity in the first and 50th cycles, the percentage of the discharge capacity in the 50th cycle to the discharge capacity in the first cycle (capacity retention rate (%)) is shown in Table 3 below.

[0357] And, the resistance was measured through the voltage change for 60 seconds in the first and 50th cycles. The percentage (resistance increase rate (%)) of the resistance (Ω) of the 50th cycle relative to the resistance (Ω) of the measured first cycle is shown in Table 3 below.

[0358]

[0359] Type of positive electrode active material Charge capacity (mAh / g) Discharge capacity (mAh / g) Capacity retention rate (%) Resistance increase rate (%) Example 5 Example 1 231.8 206.8 9 6.7 138.9 Example 6 Example 2 231.6 208.3 9 7.0 14 1.5 Example 7 Example 3 231.7 207.5 9 6.8 14 0.2 Example 8 Example 4 231.4 206.3 9 6.6 14 1.3 Comparative example 2 Comparative example 1 231.4 206.8 9 5.8 15 8.6

[0360] Through Table 3, it was confirmed that the battery including the positive electrode manufactured in Examples 5 to 8, i.e., the battery including the positive electrode active material manufactured in Examples 1 to 4, had a similar resistance increase rate as the battery including the positive electrode manufactured in Comparative Example 2, i.e., the battery including the positive electrode active material manufactured in Comparative Example 1, while improving the charge / discharge capacity and capacity retention rate.

[0361] In conclusion, it can be seen that the cathode active material according to the present invention not only improves energy density, but also causes less side reactions with the electrolyte and less irreversible damage during charge and discharge cycles.

Claims

1. Contains a lithium composite transition metal oxide in the form of a single particle containing nickel, manganese, cobalt and aluminum, A cathode active material satisfying at least one of the following conditions 1 and 2: [Condition 1] The average particle size reduction rate (χ) calculated by the following equation (1) is 35.00% or less; Equation (1) Average particle size reduction rate (χ)[%] = In the above equation (1), D 50 is the particle size [㎛] corresponding to 50% of the volume cumulative distribution according to the particle size of the positive electrode active material, D A 2g of the positive electrode active material is divided into small pieces and filled into a cylindrical holder with a diameter of 13mm, and then a force of 9000kgf is applied for 20 seconds. The particle size [㎛] corresponding to 50% of the volume cumulative distribution according to the particle size of the positive electrode active material is measured. [Condition 2] The differential incidence rate (φ) calculated by the following equation (2) is 6.0000% or less; Equation (2) Differential occurrence rate (φ)[%] = In the above equation (2), S A The total area under the line in the graph showing the cumulative volume distribution according to the particle size of the positive electrode active material measured after dividing 2g of the positive electrode active material into small pieces and filling them into a cylindrical holder with a diameter of 13mm, and applying a force of 9000kgf for 20 seconds, S B is the area under the line in the graph above where the particle size of the positive electrode active material is 1㎛ or less.

2. In claim 1, The above lithium composite transition metal oxide is a positive electrode active material having a composition represented by the following chemical formula 1: [Chemical Formula 1] Li 1+x Ni a Mr b Co c Al d M 1 e O2 In the above chemical formula 1, M 1 is at least one selected from the group consisting of Y, Zr, B, C, F, Mg, Si, P, Ca, Sc, Ti, V, Sr, Nb, Mo, Ba, La, Hf, Ta, W, Bi, Ce, Sm and Gd, -0.1≤x≤0.3, 0.5≤a<1, 0 <b<0.5, 0<c<0.5, 0<d<0.5, 0≤e≤0.1 이다.

3. In claim 1, The above lithium composite transition metal oxide is a cathode active material containing aluminum in an amount of 3,000 ppm or more and 8,000 ppm or less based on the total weight of the cathode active material.

4. In claim 1, Further comprising a coating formed on the lithium composite transition metal oxide, A cathode active material, wherein the coating portion comprises at least one coating element selected from the group consisting of Y, Zr, B, C, F, Mg, Si, P, Ca, Sc, Ti, V, Sr, Nb, Mo, Ba, La, Hf, Ta, W, Bi, Ce, Sm and Gd.

5. In claim 4, The above coating portion is an island type positive electrode active material.

6. In claim 1, A positive electrode active material having an average particle size reduction rate (χ) of 10.00% or more and 25.00% or less.

7. In claim 1, A positive electrode active material having a differential generation rate (φ) of 3.0000% or less.

8. In claim 1, Average particle diameter (D 50 ) is a positive electrode active material having a size of 1.00㎛ or more and 15.00㎛ or less.

9. A cathode active material comprising a lithium composite transition metal oxide in the form of single particles containing nickel, manganese, cobalt and aluminum, An anode satisfying at least one of the following conditions 3 and 4: [Condition 3] The average particle size reduction rate (χ') calculated by the following equation (3) is 16.00% or less; Equation (3) Average particle size reduction rate (χ')[%] = In the above equation (3), D' 50 is the particle size [㎛] corresponding to 50% of the volume cumulative distribution according to the particle size of the positive electrode active material, D' A is the particle size [㎛] corresponding to 50% of the cumulative volume distribution according to the particle size of the positive electrode active material measured by separating the positive electrode active material contained in the positive electrode after applying force to the positive electrode until the porosity becomes 20%. [Condition 4] The differential incidence rate (φ') calculated by the following equation (4) is 0.0550% or less; Equation (4) Differential occurrence rate (φ')[%] = In the above equation (4), S' A is the total area under the line in the graph showing the cumulative volume distribution according to the particle size of the positive electrode active material measured by separating the positive electrode active material contained in the positive electrode after applying force to the positive electrode until the porosity becomes 20%. S' B is the area under the line in the graph above where the particle size of the positive electrode active material is 1㎛ or less.

10. In claim 9, The positive electrode active material satisfies at least one of the following conditions 1 and 2: [Condition 1] The average particle size reduction rate (χ) calculated by the following equation (1) is 35.00% or less; Equation (1) Average particle size reduction rate (χ)[%] = In the above equation (1), D 50 is the particle size [㎛] corresponding to 50% of the volume cumulative distribution according to the particle size of the positive electrode active material, D A 2g of the positive electrode active material is divided into small pieces and filled into a cylindrical holder with a diameter of 13mm, and then a force of 9000kgf is applied for 20 seconds. The particle size [㎛] corresponding to 50% of the volume cumulative distribution according to the particle size of the positive electrode active material is measured. [Condition 2] The differential incidence rate (φ) calculated by the following equation (2) is 6.0000% or less; Equation (2) Differential occurrence rate (φ)[%] = In the above equation (2), S A The total area under the line in the graph showing the cumulative volume distribution according to the particle size of the positive electrode active material measured after dividing 2g of the positive electrode active material into small pieces and filling them into a cylindrical holder with a diameter of 13mm, and applying a force of 9000kgf for 20 seconds, S B is the area under the line in the graph above where the particle size of the positive electrode active material is 1㎛ or less.

11. A lithium secondary battery comprising a positive electrode according to claim 9 or 10.

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