Positive electrode active material for lithium secondary battery and lithium secondary battery comprising same

Abstract

A positive electrode active material for a lithium secondary battery according to one embodiment is a nickel-containing layered lithium transition metal oxide and is composed of single particles including at least one of single particles composed of one primary particle and quasi-single particles formed by aggregating a plurality of primary particles, wherein the single particles comprise, on average, 5 to 15 primary particles, have an average particle diameter (D50) of 5 μm to 8 μm, and may have an average sphericity of 0.75 or more.

Description

Cathode active material for lithium secondary batteries and lithium secondary batteries containing the same

[0001] The present invention relates to a positive electrode active material for a lithium secondary battery and a lithium secondary battery including the same.

[0002] As electric vehicles expand to achieve carbon neutrality and demand for energy storage devices such as ESS for renewable energy sources surges, lithium-ion batteries are becoming an irreplaceable, core energy storage device. In particular, the characteristics of lithium-ion batteries are significantly influenced by their cathode materials, making cathode material research a significant part of lithium-ion battery research.

[0003] Among cathode materials, active research is being conducted on NCM cathode materials, which substitute cobalt and manganese for nickel-based cathode active materials with a layered structure. Previously, much research has focused on secondary particle active materials formed by agglomeration of primary particles. However, these secondary particle active materials have high surface areas and low particle strength, leading to problems such as cracking and gas generation, which can lead to reduced battery life. Therefore, development is underway for single-particle cathode materials, primarily produced for bimodal cathode materials with an average particle size of approximately 3 to 4 μm.

[0004] The above-mentioned small-diameter single particles possess excellent mechanical particle strength characteristics, resulting in excellent lifespan and stability. However, their small particle size results in a low tap density, which limits their ability to increase electrode energy density.

[0005] To solve this problem, attempts were made to increase the tap density by increasing the particle size of the single particle, but as the particle size of the single particle increases, the lithium ion movement distance increases, which leads to a problem in that electrochemical characteristics such as capacity and charge / discharge efficiency deteriorate.

[0006] In this embodiment, it is intended to provide a single particle type positive electrode active material for a lithium secondary battery that can not only increase electrode density but also improve the capacity and charge / discharge efficiency of the battery, and a lithium secondary battery including the same.

[0007] According to one embodiment, a cathode active material for a lithium secondary battery is a nickel-containing layered lithium transition metal oxide, and is composed of single particles including at least one of a single particle composed of one primary particle and a quasi-single particle formed by agglomeration of multiple primary particles, wherein the single particle includes an average of 5 to 15 primary particles, has an average particle diameter (D50) of 5 μm to 8 μm, and may have a sphericity of 0.75 or more.

[0008] A positive electrode for a lithium secondary battery according to another embodiment may include a positive electrode active material according to one embodiment.

[0009] A lithium secondary battery according to another embodiment may include a positive electrode according to one embodiment.

[0010] These examples have excellent sphericity and a larger average particle diameter than existing small-diameter single particles, which can improve electrode density.

[0011] In addition, by appropriately controlling the average number of primary particles included in a single particle, the capacity, charge / discharge efficiency, and life characteristics of a lithium secondary battery can be improved.

[0012] Figure 1 is a schematic diagram of a quasi-single particle included in a positive electrode active material for a lithium secondary battery according to one embodiment.

[0013] Figures 2 to 4 show SEM images as examples to explain the sphericity measurement method.

[0014] Figure 5 is an SEM image of a positive electrode active material manufactured according to Example 1.

[0015] Figure 6 is an SEM image of a positive electrode active material manufactured according to Example 2.

[0016] Figure 7 is an SEM image of a positive electrode active material manufactured according to Example 3.

[0017] Figure 8 is an SEM image of a positive electrode active material manufactured according to Example 4.

[0018] Figure 9 is an SEM image of a positive electrode active material manufactured according to Example 5.

[0019] Figure 10 is an SEM image of a positive electrode active material manufactured according to Example 6.

[0020] Figure 11 is an SEM image of a positive electrode active material manufactured according to Comparative Example 1.

[0021] Figure 12 is an SEM image of a positive electrode active material manufactured according to Comparative Example 2.

[0022] Figure 13 is an SEM image of a positive electrode active material manufactured according to Comparative Example 3.

[0023] Figure 14 is an SEM image of a positive electrode active material manufactured according to Comparative Example 4.

[0024] Figure 15 is an SEM image of a positive electrode active material manufactured according to Comparative Example 5.

[0025] Figure 16 is an SEM image of a positive electrode active material manufactured according to Comparative Example 6.

[0026] The terms first, second, and third, etc., are used to describe, but are not limited to, various parts, components, regions, layers, and / or sections. These terms are used solely to distinguish one part, component, region, layer, or section from another part, component, region, layer, or section. Accordingly, a first part, component, region, layer, or section described below may be referred to as a second part, component, region, layer, or section without departing from the scope of the present invention.

[0027] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the present invention. As used herein, the singular forms "singular" and "comprising" include plural forms as well, unless the context clearly dictates otherwise. The word "comprising" as used herein specifies a particular feature, region, integer, step, operation, element, and / or component, but does not exclude the presence or addition of other features, regions, integers, steps, operations, elements, and / or components.

[0028] When a part is referred to as being "on" or "over" another part, it can be directly on or over the other part, or there may be other parts intervening. Conversely, when a part is referred to as being "directly on" another part, there are no other parts intervening.

[0029] Although not defined otherwise, all terms, including technical and scientific terms, used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention pertains. Terms defined in commonly used dictionaries are further interpreted to have meanings consistent with the relevant technical literature and the present disclosure, and are not to be construed as ideal or overly formal unless otherwise defined.

[0030] Also, unless otherwise stated, % means weight%, and 1 ppm is 0.0001 weight%.

[0031] In this specification, the term "combination(s) thereof" described in the expression in the Makushi format means one or more mixtures or combinations selected from the group consisting of the components described in the expression in the Makushi format, and means including any one or more selected from the group consisting of said components.

[0032] 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.

[0033]

[0034] Cathode active material for lithium secondary batteries

[0035] According to one embodiment, a cathode active material for a lithium secondary battery is a nickel-containing layered lithium transition metal oxide, and is composed of single particles including at least one of a single particle composed of one primary particle and a quasi-single particle formed by agglomeration of multiple primary particles, wherein the single particle includes an average of 5 to 15 primary particles, has an average particle diameter (D50) of 5 to 8 μm, and may have a sphericity of 0.75 or more.

[0036] The cathode active material for a lithium secondary battery of the present embodiment may include at least one of a single particle composed of a single primary particle and a quasi-single particle formed by agglomeration of the primary particles. In this case, the primary particle included in the quasi-single particle may be in the form of a rod.

[0037] In this specification, the term “single particle” is used to distinguish it from the secondary particle type positive electrode active material particle formed by the agglomeration of tens to hundreds of primary particles that have been commonly used in the past, and is a concept that includes a single particle composed of one primary particle and an aggregate particle of 30 or fewer primary particles. The “secondary particle” refers to an aggregate, i.e., a secondary structure, formed by the physical or chemical bonding between primary particles without an intentional agglomeration or assembly process for the primary particles.

[0038] Additionally, “single particle” means a single particle composed of only one primary particle, and “quasi-single particle” means a single particle composed of multiple primary particles.

[0039] The above “primary particle” refers to the smallest particle unit that can be distinguished as a single lump when observing the cross-section of the positive electrode active material through a scanning electron microscope (SEM), and may be composed of a single crystal grain or multiple crystal grains.

[0040] Since the positive electrode active material for a lithium secondary battery of this embodiment is composed of single particles, the particle strength is increased, which can suppress particle breakage during rolling, and the occurrence of cracks between primary particles during repeated charging and discharging can be prevented. In addition, the specific surface area is small, which can reduce the amount of gas generated due to side reactions with the electrolyte. In addition, the rolling density can be increased during electrode manufacturing, which can improve the energy density of the electrode.

[0041] The above-mentioned positive electrode active material for a lithium secondary battery may have an average particle diameter (D50) of 5 to 8 μm, and more specifically, 5.1 to 8 μm or 5.5 to 8 μm.

[0042] In this specification, the average particle diameter (D50) can be defined as the particle diameter corresponding to 50% of the volume accumulation amount in the particle diameter distribution curve. The average particle diameter (D50) can be measured using, for example, the laser diffraction method. The laser diffraction method can generally measure particle diameters from the submicron range to several millimeters, and can obtain results with high reproducibility and high resolution.

[0043] When the average particle size of the positive electrode active material is sufficiently large, as in the above range, the tap density can be further improved compared to conventional small-diameter single particles, and as a result, the electrode density can be significantly improved. However, if the average particle size of the positive electrode active material is excessively large, the lithium ion migration path can become longer, which can deteriorate electrochemical characteristics such as capacity and output. Therefore, the upper limit is set as above.

[0044] Figure 1 is a schematic diagram of a quasi-single particle included in a positive electrode active material for a lithium secondary battery according to one embodiment.

[0045] Referring to FIG. 1, in this embodiment, the quasi-single particle may be a spherical particle formed by overlapping multiple primary particles in the form of rods.

[0046] In this specification, the term "spherical" does not necessarily have to be a spherical shape, but rather encompasses pseudo-spherical shapes. Such single particles may have a shape similar to a volleyball.

[0047] Here, the single particle may include an average of 5 to 15 primary particles, more specifically 8 to 14 or 10 to 12 primary particles. In this case, the “single particle” encompasses both single particles and quasi-single particles included in the positive electrode active material according to the present embodiment.

[0048] In this specification, the “average number of primary particles in a single particle” can be obtained by deriving the arithmetic mean of the number of primary particles observed with the naked eye for each of at least five random single particles in a (25 μm) × (20 μm) 2D image observed in a SEM (scanning electron microscope) image at 5,000x magnification. It should be noted that in this specification, the “average number of primary particles in a single particle” refers to the average number of primary particles observed in a SEM image of a 2D image, not the average number of primary particles contained in a single particle in an actual three-dimensional reality.

[0049] If the average number of primary particles contained in a single particle is too small, the movement path of lithium ions may become longer, which may result in deterioration of electrochemical characteristics such as capacity, charge / discharge efficiency, and output. If the average number of primary particles contained in a single particle is too large, the characteristics may be closer to polycrystals rather than single crystals, and the capacity and charge / discharge efficiency may be excellent. However, the lifespan may be deteriorated due to the shrinkage and expansion of numerous primary particles during charge / discharge, which may cause other particle breakage.

[0050] At this time, the average particle diameter (D50) of the primary particles included in the single particles may be 1 μm or less. When the average particle diameter (D50) of the primary particles included in the single particles is sufficiently small within the above range, the effects of improving capacity and charge / discharge efficiency can be more preferably implemented.

[0051] Meanwhile, the average aspect ratio of the primary particles included in the single particle may be in the range of 1.1 to 2.5.

[0052] In this specification, “aspect ratio” may be defined as the ratio of the length of the longest side to the length of the shortest side of a particle, and “average aspect ratio” may be defined as the arithmetic mean of the aspect ratios derived by measuring the lengths of the shortest and longest sides using software during the SEM image measurement process for particle shape analysis for at least 10 particles. The reason why the average aspect ratio of the primary particles is 1.1 or more and the shape of the primary particles is closer to a rod shape than a perfect sphere is because the surface energy is different depending on the crystal plane and the crystal tends to grow in the direction of the thermodynamically stable 003 plane. The larger the aspect ratio, the advantage of increasing particle strength is that, however, if the average aspect ratio of the primary particles is too large, there may be a problem of reduced capacity and efficiency due to an increase in the lithium diffusion distance.

[0053] The average sphericity of the above single particles may be 0.75 or higher, more specifically, in the range of 0.8 to 1.0 or 0.8 to 0.9. When the average sphericity satisfies the above range, a positive electrode active material for a lithium secondary battery having excellent electrode density can be realized.

[0054] In this specification, the average sphericity of a single particle can be calculated as the square of the ratio of the perimeter of a circle having the same area as the particle to the perimeter of the particle. For example, the sphericity of a particle can be calculated using the following mathematical expression 1.

[0055] [Mathematical Formula 1]

[0056]

[0057] Circularity = 4πA / P 2

[0058] In the above mathematical expression 1, A is the area of ​​the particle, and P is the perimeter of the particle.

[0059] The area and perimeter of the particles are observed by observing the cross-section of the active material using a scanning electron microscope (SEM).

[0060] Figures 2 to 4 illustrate SEM images for explaining a sphericity measurement method. Specifically, an image obtained by SEM as in Figure 2 is converted into an image in which the background and particles are separated as in Figure 3 using a traditional image processing algorithm or a computer vision algorithm, and then the area and perimeter of the particles can be measured using a Contour algorithm.

[0061] At this time, the calculated pixel-based area (unit: pixel) 2 ) and perimeter (unit: pixel) need to be calculated in order to convert the actual particle size (unit: ㎛) to the pixel value of the scale bar. 185 pixels corresponding to the scale bar shown in Fig. 4 correspond to 100 microns, so the pixel value was converted to length to measure the area and perimeter.

[0062] The above positive electrode active material for lithium secondary batteries has a tap density of 2.2 g / cm 3 It could be strange.

[0063] In this specification, tap density can be measured using Geopyc 1365 (Micromeritics), which is generally used in the art as a method for measuring the degree of filling of a sample per unit volume. This can solve measurement errors by squeezing with a controlled force in the horizontal direction and reading the value digitally to prevent errors that may occur in the conventional tap density measurement method, which involves a person reading the scale after a free fall in the vertical direction (tapping).

[0064] The method may be a density calculated through the change in volume (weight / volume) using the transverse axial pressure analysis option to measure the compressed bulk density of powders in compliance with ASTM D8097.

[0065] Since the tap density of the positive electrode active material is sufficiently large as described above, the electrode energy density can be improved.

[0066] Meanwhile, the lithium transition metal oxide may contain nickel in an amount of 60 mol% or more, and more specifically, 70, 80, or 90 mol% or more, based on the total moles of transition metals. With such a high nickel content, high-capacity characteristics can be realized.

[0067] The lithium transition metal oxide may further include a grain growth promoting element composed of Zr, Al, B, or a combination thereof. By further including the grain growth promoting element in the lithium transition metal oxide, the sintering temperature for forming the lithium transition metal oxide can be lowered, thereby preventing crystal defects such as an increase in the cation mixing ratio due to high-temperature sintering, and the average particle diameter of single particles can be efficiently increased during the sintering process.

[0068] The content of the above grain growth promoting element may be 0.1 to 1 mol% based on the total mole number of transition metals, and more specifically, 0.3 to 1 mol%. More specifically, the content of Zr may be 0.1 to 0.3 mol% based on the total mole number of transition metals. In addition, the content of Al may be 0.2 to 0.8 mol% based on the total mole number of transition metals. In addition, the content of B may be 0.1 to 0.8 mol% based on the total mole number of transition metals.

[0069] When the content of the growth-promoting element satisfies the above range, the effect of adding the growth-promoting element described above and the effect of preventing deterioration of electrochemical properties due to excessive addition can be equally implemented.

[0070]

[0071] The above-described positive electrode active material may further include a coating layer comprising Co, Al, or a combination thereof on the lithium transition metal oxide. By further including a coating layer having the above-described composition, the positive electrode active material can suppress side reactions with the electrolyte, improve the structural stability of the active material, and further improve battery life characteristics.

[0072]

[0073] The lithium transition metal oxide according to this embodiment can be more specifically represented by the following chemical formula 1.

[0074] [Chemical Formula 1]

[0075] Li a [Ni x Co y Mn z M1 w1 M2 W2 ]O2

[0076] In the above chemical formula 1, 0.8≤a≤1.2, 0.60≤x<1, 0≤y≤0.4, 0≤z≤0.4, 0≤w1≤0.01, 0≤w2≤0.2, x+y+z+w1+w2=1, M1 is Zr, Al, B or a combination thereof, and M2 is Y, Mg, Ti, Nb, W, Sc, Si, V, Fe, Y, Mo, Ce, Hf, Ta, La, Sr or a combination thereof.

[0077] In the lithium transition metal oxide of the above chemical formula 1, lithium may be included in a content corresponding to a, that is, 0.8≤a≤1.2. If a is too small, the capacity may be reduced, and if a is too large, the strength of the sintered positive electrode active material may be increased, making pulverization difficult, and the amount of gas generated may increase due to an increase in lithium byproducts. Considering the effect of improving the capacity characteristics of the positive electrode active material according to the control of the lithium content and the sinterability balance during the production of the active material, the lithium may be included in a content of 0.9≤a≤1.1 more preferably.

[0078] In the lithium transition metal oxide of the above chemical formula 1, nickel may be included in an amount corresponding to x, that is, 0.6≤x<1, 0.6≤x≤0.97, 0.80≤x≤0.97, or 0.90≤x≤0.97. If the nickel amount is too low, it may be difficult to achieve high capacity of the battery, and if the nickel amount is too high, the battery life and safety may be reduced due to a decrease in the structural stability of the active material.

[0079] In the lithium transition metal oxide of the above chemical formula 1, cobalt may be included in an amount corresponding to y, i.e., 0≤y≤0.4, 0≤y≤0.2, or 0≤y≤0.1. If the cobalt amount is too low, it may be difficult to simultaneously achieve sufficient rate characteristics and high powder density of the active material. If the cobalt amount is too high, the overall cost of the raw material may increase and the reversible capacity may decrease.

[0080] In the lithium transition metal oxide of the above chemical formula 1, manganese may be included in a content corresponding to z, i.e., 0≤z≤0.4. If the manganese content is too low, the production cost may increase and the stability of the active material may decrease. If the manganese content is too high, the capacity and output characteristics of the battery may decrease.

[0081] In the lithium transition metal oxide of the above chemical formula 1, M1 may be included in a content corresponding to w1, that is, 0≤w1≤0.01. At this time, M1 is a grain growth promoting element, and is Zr, Al, B, or a combination thereof.

[0082] In the lithium transition metal oxide of the above chemical formula 1, M2 may be included in a content corresponding to w2, that is, 0≤w2≤0.2. At this time, M2 is another doping element, such as Y, Mg, Ti, Nb, W, Sc, Si, V, Fe, Y, Mo, Ce, Hf, Ta, La, Sr, or a combination thereof.

[0083]

[0084] Method for manufacturing a cathode active material for lithium secondary transfer

[0085] According to another embodiment, a method for manufacturing a cathode active material for a lithium secondary battery includes the steps of: preparing a nickel-containing transition metal hydroxide; forming a mixture including the transition metal hydroxide and a lithium raw material and then firing the mixture to form a lithium transition metal oxide having an increased number of primary particles; post-firing the lithium transition metal oxide; and pulverizing the post-firing lithium transition metal oxide to form a lithium transition metal oxide of single particles, wherein the main-firing temperature is higher than the post-firing temperature, and the average number of primary particles in the single particles may be 5 to 15 and the average sphericity may be 0.75 or more.

[0086] Hereinafter, a method for manufacturing a positive electrode active material for a lithium secondary battery according to this embodiment is described step by step.

[0087]

[0088] First, prepare a nickel-containing transition metal hydroxide.

[0089] The above transition metal hydroxide may be prepared by a coprecipitation reaction by adding a complexing agent-containing solution and a pH adjusting agent-containing solution to a transition metal-containing solution including, for example, a nickel raw material and optionally, a cobalt raw material or a manganese raw material, as a precursor of a positive electrode active material.

[0090] At this time, the average particle diameter (D50) of the transition metal hydroxide may be 5 μm or more. When the average particle diameter of the transition metal hydroxide satisfies the above range, a single-particle lithium transition metal oxide having a medium particle diameter as targeted by this embodiment can be easily obtained.

[0091] The above nickel raw material is not particularly limited as long as it is used in the art for manufacturing a positive electrode active material precursor. For example, the nickel raw material may be a nickel-containing sulfate, acetate, nitrate, halide, sulfide, hydroxide, oxide, or oxyhydroxide, and specifically, may be NiSO4, NiSO4·6H2O, Ni(OH)2, NiO, NiOOH, NiCO3·2Ni(OH)2·4H2O, NiC2O2·2H2O, Ni(NO3)2·6H2O, fatty acid nickel salt, nickel halide, or a combination thereof, but is not limited thereto.

[0092] The above cobalt raw material is not particularly limited as long as it is used in the art for manufacturing a positive electrode active material precursor. For example, the cobalt raw material may be a cobalt-containing sulfate, acetate, nitrate, halide, sulfide, hydroxide, oxide, or oxyhydroxide, and specifically, CoSO 4, It may be, but is not limited to, CoSO4ㆍ7H2O, Co(OH)2, CoOOH, Co(OCOCH3)2ㆍ4H2O, Co(NO3)2ㆍ6H2O or a combination thereof.

[0093] The manganese raw material is not particularly limited as long as it is used in the art for manufacturing a precursor of a cathode active material. For example, the manganese raw material may be a manganese-containing sulfate, acetate, nitrate, halide, sulfide, hydroxide, oxide, oxyhydroxide, or a combination thereof, and specifically, may be a manganese salt such as MnSO4, MnCO3, Mn(NO3)2, manganese acetate, manganese dicarboxylic acid salt, manganese citrate, and manganese fatty acid salt, manganese oxide such as Mn2O3, MnO2, and Mn3O4, oxyhydroxide, manganese chloride, or a combination thereof, but is not limited thereto.

[0094] The above transition metal-containing solution may be prepared by adding a nickel raw material and optionally a cobalt raw material or a manganese raw material to a solvent, specifically, water, or a mixture of water and an organic solvent (e.g., alcohol, etc.) that can be uniformly mixed with water.

[0095] The above complexing agent-containing solution performs the function of forming a complex, and may include, but is not limited to, NH3, NH4OH, (NH4)2SO4, NH4NO3, NH4Cl, CH3COONH4, NH4CO3 or a combination thereof as the complexing agent. Meanwhile, the complexing agent-containing solution may be used in the form of an aqueous solution, and at this time, water or a mixture of water and an organic solvent (e.g., alcohol, etc.) that can be uniformly mixed with water may be used as the solvent.

[0096] The above pH adjusting agent-containing solution acts as a precipitant or pH adjusting agent, and may include an alkaline compound such as a hydroxide of an alkali metal or alkaline earth metal, such as NaOH, KOH, or Ca(OH)2, a hydrate thereof, or a combination thereof. Meanwhile, the pH adjusting agent-containing solution may also be used in the form of an aqueous solution, and at this time, water or a mixture of water and an organic solvent (e.g., alcohol, etc.) that can be uniformly mixed with water may be used as the solvent. At this time, the pH adjusting agent-containing solution may be added in an amount such that the pH of the reaction solution becomes 11 to 13.

[0097] The above coprecipitation reaction can be performed under an inert atmosphere such as nitrogen or argon, can be performed at a temperature of 30 to 70°C, and can be performed at a pH of 11 to 13.

[0098] Through the above process, nickel-cobalt-manganese (doped element) hydroxide particles are generated and precipitated within the reaction solution. The precipitated precursor particles can be separated, washed, and dried using conventional methods to obtain the precursor. The precursor may be a secondary particle formed by the agglomeration of primary particles.

[0099] At this time, the molar ratio of nickel, cobalt, and manganese in the precursor can be controlled by controlling the concentration of nickel raw material, cobalt raw material, and manganese raw material.

[0100] Meanwhile, the doping element may also be doped during the preparation stage of the positive electrode active material precursor. In this case, the doping raw material may be additionally added to a transition metal-containing solution and a co-precipitation reaction may be performed to dope the precursor with the doping element.

[0101]

[0102] Next, a mixture containing the above transition metal hydroxide and lithium raw material is formed and then calcined to form a lithium transition metal oxide in which the number of primary particles has grown.

[0103] Afterwards, the grown lithium transition metal oxide is post-calcined.

[0104] The method for manufacturing an active material according to this embodiment is performed by dividing the firing into two stages as described above, and the main firing temperature is higher than the post-firing temperature.

[0105] High-temperature sintering can grow the number of primary particles within a single particle to an appropriate range. Low-temperature post-sintering can induce crystal rearrangement, thereby relieving the increased internal stress during high-temperature sintering and reducing nickel cation mixing.

[0106] That is, as a conventional method for manufacturing single particles, the single-stage firing method of high temperature and long-term firing had problems such as nickel cation mixing and the generation of rock salt impurities. On the other hand, in the present embodiment, the above problems can be prevented through high-temperature main firing and low-temperature post-firing, and the number of primary particles within the single particle can be appropriately grown to the target range of the present embodiment mentioned above.

[0107] Specifically, the main firing temperature and the post-firing temperature may each independently be 770 to 880°C, and more specifically, the main firing temperature may be 850°C or higher, and the post-firing temperature may be 800°C or lower. When the main firing temperature and the post-firing temperature each satisfy the above range, the two-stage firing effect mentioned above can be more preferably implemented.

[0108] In addition, the main firing time may be shorter than the post-firing time. That is, the main firing time, which is a high-temperature firing time, may be shortened, and the post-firing time, which is a low-temperature firing time, may be lengthened, so that the two-stage firing effect mentioned above can be more preferably implemented.

[0109] Specifically, in the step of forming the lithium transition metal oxide, the main firing time and the post-firing time may each independently be 2 to 13 hours. More specifically, the main firing time may be 6 hours or less, and the post-firing time may be 8 hours or more. When the main firing and post-firing times satisfy the above ranges, the aforementioned two-stage firing effect can be more preferably implemented.

[0110]

[0111] In addition, the mixture may further include a grain growth accelerator, which is a Zr raw material, an Al raw material, a B raw material, or a combination thereof. By further including a grain growth accelerator, the sintering temperature can be lowered, and the grain size of single particles can be efficiently increased.

[0112] The content of the grain growth accelerator may be 0.1 to 1 mol% based on the total mole number of transition metals in the transition metal hydroxide, and more specifically, may be 0.3 to 1 mol%. More specifically, the content of the Zr raw material may be 0.1 to 0.3 mol% based on the total mole number of transition metals in the transition metal hydroxide. In addition, the content of the Al raw material may be 0.2 to 0.8 mol% based on the total mole number of transition metals in the transition metal hydroxide. In addition, the content of the B raw material may be 0.1 to 0.8 mol% based on the total mole number of transition metals in the transition metal hydroxide. The technical significance of controlling the content of the grain growth accelerator is as described above, and thus is omitted.

[0113] The lithium raw material may be lithium-containing sulfate, nitrate, acetate, carbonate, oxalate, citrate, halide, hydroxide, or oxyhydroxide, and is not particularly limited as long as it can be dissolved in water. Specifically, the lithium raw material may be, but is not limited to, Li2CO3, LiNO3, LiNO2, LiOH, LiOHㆍH2O, LiH, LiF, LiCl, LiBr, LiI, CH3COOLi, Li2O, Li2SO4, CH3COOLi, Li3C6H5O7, or a combination thereof.

[0114] The above firing can be performed under an oxygen or air atmosphere. When firing under the above atmosphere, the local oxygen partial pressure increases, which can improve the crystallinity of the positive electrode active material.

[0115] Meanwhile, other doping elements can be doped during the lithium transition metal oxide formation stage. In this case, other doping raw materials can be added during the formation of the mixture and then calcined to dope other doping elements into the lithium transition metal oxide.

[0116]

[0117] Next, the post-calcined lithium transition metal oxide is pulverized to form single particles of lithium transition metal oxide.

[0118] Thus, a single-particle positive electrode active material according to the present embodiment can be obtained, wherein the average number of primary particles included in the single particles is 5 to 15, and the average sphericity can be 0.75 or more. A specific description thereof is as described above.

[0119] If necessary, after the step of forming the lithium transition metal oxide of the single particle, a step of forming a coating layer including Co, Al or a combination thereof may be further included.

[0120] More specifically, a coating layer can be formed by mixing the lithium transition metal oxide of the single particle with a Co raw material, an Al raw material, or a combination thereof, and then heat-treating the mixture. The technical significance of forming the coating layer is as described above, and thus is omitted.

[0121]

[0122] anode

[0123] In another embodiment, the present invention includes a current collector, and a positive electrode active material layer positioned on one surface of the current collector and comprising a positive electrode active material manufactured according to the above-described embodiment.

[0124] At this time, the rolling density of the positive electrode may be 3.55 g / cc or more, more specifically, 3.58 g / cc to 3.75 g / cc or 3.6 g / cc to 3.7 g / cc.

[0125] When the rolling density satisfies the above range, the energy density of a lithium secondary battery can be significantly improved. Therefore, when the cathode according to the present embodiment is applied to an electric vehicle, the driving range can be dramatically increased.

[0126] The characteristics of the positive electrode active material constituting the positive electrode active material layer are the same as described above. Therefore, a detailed description of the positive electrode active material will be omitted.

[0127] The above-mentioned collector may be, for example, made of stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, etc.

[0128] Meanwhile, the positive electrode active material layer may include a binder and a conductive material.

[0129] At this time, the binder plays a role of improving the adhesion between the positive electrode active material particles and the adhesive strength between the positive electrode active material and the positive electrode 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, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer rubber (EPDM rubber), sulfonated-EPDM, styrene butadiene rubber (SBR), fluororubber, or various copolymers thereof, and one kind alone or a mixture of two or more kinds thereof may be used, but is not limited thereto. The binder may be included in an amount of 1 to 30 wt% based on the total weight of the positive electrode active material layer.

[0130] And, 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 among these may be used, but the present invention is not limited thereto. The conductive material may typically be included in an amount of 1 to 30 wt% based on the total weight of the positive electrode active material layer.

[0131] The above positive electrode can be manufactured according to a conventional positive electrode manufacturing method, except that the above positive electrode active material is used.

[0132] Specifically, the positive electrode can be manufactured by applying a composition for forming a positive electrode active material layer, including the positive electrode active material described above and optionally a binder, a conductive agent, or 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 agent are as described above.

[0133] The solvent may be a solvent generally used in the relevant technical field, such as dimethylsulfoxide (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.

[0134] Alternatively, the positive electrode may be manufactured by casting the composition for forming the positive electrode active material layer on a separate support, and then laminating the resulting film on a positive electrode current collector by peeling it off from the support.

[0135]

[0136] lithium secondary battery

[0137] In another embodiment, a lithium secondary battery including the positive electrode is provided.

[0138] The lithium secondary battery may specifically include a positive electrode, a negative electrode positioned opposite the positive electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte, wherein the positive electrode is as described above. In addition, the lithium secondary battery may optionally further include a battery container that houses an electrode assembly including the positive electrode, the negative electrode, and the separator, and a sealing member that seals the battery container.

[0139] In the above lithium secondary battery, the negative electrode may include a negative electrode current collector and a negative electrode active material layer positioned on the negative electrode current collector.

[0140] 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.

[0141] The negative electrode active material layer may optionally include a binder and a conductive material together with the negative electrode active material. As an example, the negative electrode active material layer may be manufactured by applying a composition for forming a negative electrode active material layer comprising the negative electrode active material and optionally a binder and a conductive material onto a negative electrode current collector and drying the composition, or by casting the negative electrode forming composition onto a separate support and then laminating the resulting film onto a negative electrode current collector by peeling the film off from the support.

[0142] As the negative electrode active material, a compound capable of reversible intercalation and deintercalation of lithium may be used. Specific examples thereof include carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber, and amorphous carbon; metallic compounds capable of alloying with lithium, such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloy, Sn alloy, and Al alloy; metallic oxides capable of doping and dedoping lithium, such as SiOβ (0 < β < 2), SnO2, vanadium oxide, and lithium vanadium oxide; or composites comprising the 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.

[0143] The above binder and conductive material may be the same as those described above for the positive electrode.

[0144] Next, depending on the type of lithium secondary battery, a separator may be present between the positive and negative electrodes. Such separators may include polyethylene, polypropylene, polyvinylidene fluoride, or multilayer films of two or more layers thereof, and mixed multilayer films such as a polyethylene / polypropylene two-layer separator, a polyethylene / polypropylene / polyethylene three-layer separator, or a polypropylene / polyethylene / polypropylene three-layer separator may also be used.

[0145] In addition, in the lithium secondary battery, examples of the electrolyte include, but are not limited to, organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel-type polymer electrolytes, solid inorganic electrolytes, and molten inorganic electrolytes that can be used in the manufacture of lithium secondary batteries.

[0146] Specifically, the organic liquid electrolyte may include an organic solvent and a lithium salt.

[0147] The organic solvent may be used without any particular limitation as long as it can serve as a medium through which ions involved in the electrochemical reaction of the battery can move. Specifically, the organic solvent may include 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), methylethylcarbonate (MEC), ethylmethylcarbonate (EMC), ethylene carbonate (EC), and propylene carbonate (PC); alcohol solvents such as ethyl alcohol and isopropyl alcohol; nitriles such as R-CN (wherein R is a C2 to C20 linear, branched, or cyclic hydrocarbon group, and may include a double-bonded aromatic ring or an ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; or sulfolanes can be used. Among these, a carbonate solvent is preferable, and a mixture of a cyclic carbonate (e.g., ethylene carbonate or propylene carbonate, etc.) having high ionic conductivity and high dielectric constant that can improve the charge / discharge performance of the battery and a linear carbonate compound having low viscosity (e.g., ethyl methyl carbonate, dimethyl carbonate, or diethyl carbonate, etc.) 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.

[0148] 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. It is preferable that the concentration of the lithium salt be used within the range of 0.1 to 2.0 M. When the concentration of the lithium salt is within the above range, the electrolyte can exhibit excellent electrolyte performance because it has appropriate conductivity and viscosity, and lithium ions can move effectively.

[0149]

[0150] Hereinafter, embodiments of the present invention will be described in detail. However, these are presented as examples and the present invention is not limited thereto, and the present invention is defined solely by the scope of the claims set forth below.

[0151]

[0152] Example 1

[0153] (1) Manufacturing of positive electrode active material

[0154] (Preparation of transition metal hydroxide) According to the general coprecipitation method, (Ni) with an average particle size (D50) of 7 μm 0.96 Co 0.03 Mn 0.01 )(OH)2 composition hydroxide was prepared.

[0155] (Sintering) After mixing 200 g of the above transition metal hydroxide, 90.556 g of LiOH·H2O as a lithium raw material, 0.403 g of ZrO2 and 30.850 g of Al(OH) as a grain growth accelerator, main firing was performed at a temperature of 860°C for 3.8 hours, and post-sintering was performed at a temperature of 790°C for 9.8 hours.

[0156] (After disintegration), the above-mentioned sintered material was disintegrated to form a single particle of lithium transition metal oxide. At this time, the molar numbers of lithium (Li), zirconium (Zr), and aluminum (Al) per 1 mol of transition metal in the lithium transition metal oxide correspond to 1.00, 0.0015, and 0.005 mol, respectively.

[0157] (Coating) After that, 130 g of the above lithium transition metal oxide was mixed with 0.560 g of LiOH·H2O, 22.504 g of Co(OH), and 30.189 g of Al(OH) to prepare a mixture, and then heat-treated at 650 to 700°C for 15 hours to prepare a positive electrode active material having a coating layer containing 2 mol% of Co and 0.2 mol% of Al formed on the surface.

[0158]

[0159] (2) Lithium secondary battery manufacturing

[0160] The slurry for manufacturing the electrode plate was mixed with the above-mentioned positive electrode active material: conductive material (carbon black, Denka black): binder (PVDF, KF1100) = 96.5:1.5:2 wt%, and the viscosity was adjusted so that the solid content was approximately 30% by adding NMP (N-Methyl-2-pyrrolidone). The manufactured slurry was coated on a 15 μm thick Al foil using a doctor blade, and then dried and rolled. The electrode loading was 15.0 mg / cm 2 and the rolling density (25 ℃, 20 kN) was 3.6 g / cm 3 It was.

[0161] The electrolyte was 1M LiPF6in EC:DMC:EMC=3:4:3 (vol%), with 3.0 vol% VC added to the total amount of the electrolyte, and a coin cell was manufactured using a PP separator and a lithium negative electrode (200 μm, Honzo metal).

[0162]

[0163] Examples 2 to 6

[0164] As shown in Table 1, LiOH·H2O as a lithium raw material and ZrO2 as a grain growth accelerator in the calcination step. A cathode active material and a lithium secondary battery were manufactured in the same manner as in Example 1, except that the contents of Al(OH)3 and B(OH)3, the sintering temperature and sintering time conditions of the main sintering and post-sintering were adjusted.

[0165]

[0166] Comparative Example 1

[0167] In the transition metal hydroxide preparation step, (Ni) having an average particle diameter (D50) of 4 μm 0.96 Co 0.03 Mn 0.01 )(OH)2 composition is prepared, and LiOH·H2O as a lithium raw material and ZrO2 as a grain growth accelerator are used in the calcination step as shown in Table 1. A cathode active material and a lithium secondary battery were manufactured in the same manner as in Example 1, except that the content of Al(OH)3, the sintering temperature and sintering time conditions of the main sintering and post-sintering were adjusted.

[0168]

[0169] Comparative Examples 2 to 6

[0170] As shown in Table 1, LiOH·H2O as a lithium raw material and ZrO2 as a grain growth accelerator in the calcination step. A cathode active material and a lithium secondary battery were manufactured in the same manner as in Example 1, except that the content of Al(OH)3, the sintering temperature and sintering time conditions of the main sintering and post-sintering were adjusted.

[0171]

[0172] Table 1 below summarizes the active material manufacturing conditions of the above examples and comparative examples.

[0173] ClassificationLiOH·H2O (based on 1 mol of transition metal)ZrO2 (based on 1 mol of transition metal)Al(OH)3 (based on 1 mol of transition metal)B(OH)3 (based on 1 mol of transition metal)Precursor average particle size (μm)Main firing temperature (℃)Main firing time (h)Post-firing temperature (℃)Post-firing time (h)Example 11.000.00150.005-78603.87909.8Example 21.010.00150.005-78603.87909.8Example 31.000.00150.005-78503.87909.8Example 41.010.00150.0050.00178503.87909.8Example 51.010.00150.005-78505.77909.0 Example 61.030.00150.005-78603.87909.8 Comparative Example 11.020.00150.005-48303.87409.8 Comparative Example 21.010.00150.005-78403.87909.8 Comparative Example 31.020.00150.005-78608.87909.8 Comparative Example 41.000.00150.00578203.88509.8 Comparative Example 51.000.00150.005786097904 Comparative Example 61.000.00150.005785010--

[0174] Experimental Example 1: Observation of SEM images of active materials

[0175] SEM (scanning electron microscope) images of the positive electrode active materials manufactured according to the examples and comparative examples were observed, and these are shown in the order of Examples 1 to 6 and Comparative Examples 1 to 6 in FIGS. 5 to 16, respectively.

[0176] Referring to FIGS. 5 to 16, it was confirmed that the active materials according to the examples and comparative examples were in the form of single particles, rather than in the form formed by agglomeration of tens to hundreds of primary particles classified as conventional secondary particle shapes.

[0177] It was confirmed that the single particles of Examples 1 to 6 had an average particle diameter of an appropriate size, with the number of primary particles contained in the single particles being neither too small nor too large.

[0178] On the other hand, it was confirmed that the single particles of Comparative Example 1 had a somewhat smaller average particle diameter. It was confirmed that the single particles of Comparative Example 2 contained a significantly larger number of primary particles. It was confirmed that the single particles of Comparative Example 3 contained a significantly smaller number of primary particles.

[0179]

[0180] Experimental Example 2: Evaluation of Active Material Properties

[0181] The properties of the positive electrode active materials manufactured according to the examples and comparative examples were evaluated, and the results are shown in Table 2 below. The specific experimental methods are as follows.

[0182] (1) Evaluation of the average number of primary particles in a single particle

[0183] A 2D image of (25 μm) × (20 μm) observed on a SEM (scanning electron microscope) image at 5,000x magnification was taken at 5 points per sample, and the arithmetic mean value of the number of primary particles observed with the naked eye for each of at least 5 random single particles per point was derived.

[0184] (2) Measurement of average sphericity

[0185] The average sphericity of the particles was calculated using the following mathematical formula 1.

[0186] [Mathematical Formula 1]

[0187] Circularity = 4πA / P 2

[0188] In the above mathematical expression 1, A is the area of ​​the particle, and P is the perimeter of the particle.

[0189] The area and perimeter of the particles were measured using images of the cross-section of the active material taken with a scanning electron microscope (SEM).

[0190] (3) Tap density evaluation

[0191] In compliance with ASTM D8097, the compressed bulk density was measured by placing 10 g of active material powder in a piston container and applying transverse pressure using Geopyc 1365 (Micromeritics) equipment.

[0192] (4) Average particle size (D50) evaluation

[0193] For the active material powder, the particle size corresponding to 50% of the cumulative volume was measured using the laser diffraction method.

[0194] (5) Rolling density evaluation (9 tons)

[0195] The density was evaluated after applying 9 tons of pressure. Specifically, 3g of the active material sample was loaded onto a 13mm diameter pellet, and 9 tons of pressure was applied using a hydraulic press from Caver. The change in the height of the pellet before and after applying the pressure was measured, and the specific calculation formula is as follows.

[0196] [Calculation Formula 1]

[0197] Density after applying 9 tons of pressure = Weight of active material sample (3g) / (φ*(1.3cm / 2) 2 *Height change before and after pressure application))

[0198]

[0199] Average number of primary particles in a single particle Average sphericity Tap density (g / cc) Average particle size (D50, μm) Example 1 100.8 12.5 7 45.18 Example 2 110.8 2.5 445.84 Example 3 120.8 32.5 7 8 5.78 Example 4 110.8 32.5 8 35.54 Example 5 100.8 02.5 265.82 Example 6 100.8 02.3 5 5.51 Comparative Example 1-0.5 11.7 3 4.13 Comparative Example 2 200.8 2.5 8 56.01 Comparative Example 3 30.7 02.3 1 35.44 Comparative Example 4 40.6 9 2.3 15.53 Comparative Example 530.652.3125.65Comparison example 640.662.3215.46

[0200] Referring to Table 2 above, it was confirmed that the positive electrode active materials of Examples 1 to 6, in which the process conditions were appropriately controlled to have an average sphericity satisfying the range of the present embodiment, were properly obtained with an average number of primary particles within the target range. On the other hand, in the case of Comparative Example 1, in which the average particle diameter of the transition metal hydroxide precursor was too small and the average sphericity value was around 0.5, it was confirmed that the average particle diameter of the single particle was as small as 4.13 μm, and accordingly, it was confirmed that the tap density was also lowered.

[0201] In addition, in the case of Comparative Example 2, where the sintering temperature was too low, it was confirmed that although the sphericity was excellent, the average number of primary particles per particle was too large.

[0202] In addition, in the case of Comparative Example 3, where the firing time was too long, it was confirmed that the sphericity was outside the range of the present embodiment and the average number of primary particles in a single particle was too small.

[0203] In addition, in Comparative Example 4 where the post-firing temperature was higher than the main firing temperature, in Comparative Example 5 where the post-firing time was shorter than the main firing time, and in Comparative Example 6 where only the main firing was performed for a long time without post-firing, it was confirmed that the average sphericity was far outside the range of this example, and the average number of primary particles in a single particle was obtained too small.

[0204]

[0205] Experimental Example 3: Evaluation of Battery Electrochemical Characteristics

[0206] The electrochemical characteristics of lithium secondary batteries manufactured according to the examples and comparative examples were evaluated, and the results are shown in Table 3 below. The specific experimental methods are as follows.

[0207] (1) Initial charge and discharge capacity, initial efficiency evaluation

[0208] After fabricating half-cells of lithium secondary batteries, they were aged at 25°C for 12 hours and then subjected to charge-discharge tests. To evaluate the initial capacity, 200 mAh / g was used as the reference capacity, and the cells were charged to 4.25 V at a constant current of 0.1 C. After switching to constant voltage, the cells were charged until the end current reached 0.05 C. After a 10-minute rest period, the cells were discharged to 2.5 V at a constant current of 0.1 C, using 200 mAh / g as the reference capacity.

[0209] (2) Evaluation of high temperature lifespan (45℃, 50 cycles)

[0210] The high-temperature life retention rate was determined by charging the battery to 4.25 V at a constant current of 0.5 C at 45°C, then switching to a constant voltage and charging until the end current reached 0.05 C. After a 10-minute rest period after charging, the battery was discharged at a constant current of 1.0 C until the voltage reached 2.5 V. Fifty charge and discharge cycles were performed under these charge and discharge conditions, and the capacity retention rate of the 50th cycle was calculated compared to the first cycle.

[0211] (3) Evaluation of high temperature resistance increase rate (45℃, 50 cycles)

[0212] The high temperature resistance increase rate was measured by charging the battery to 4.25 V at a constant current of 0.5 C at 45 °C, then switching to a constant voltage and charging until the end current reached 0.05 C. After a 10-minute rest time after charging, the battery was discharged at a constant current of 1.0 C until the voltage reached 2.5 V. 50 charge / discharge cycles were performed under these charge / discharge conditions, and the resistance increase rate of the 50th cycle compared to the first cycle was calculated.

[0213]

[0214] Rolling density (g / cc) @ 9 tonCharging capacity (mAh / g, 0.1C)Discharging capacity (mAh / g, 0.1C)Initial efficiency (%)High temperature life maintenance rate (%, 50 cycles)High temperature resistance increase rate (%, 50 cycles)Example 13.63243.2212.187.293.471.5Example 23.63243.8210.986.592.788.1Example 33.66244.3213.587.492.966.2Example 43.62241.7208.886.492.590.5Example 53.61241.8208.786.393.870.1Example 63.62243.5212.287.293.077.0Comparative Example 13.30243.4216.789.091.576.1Comparative Example 23.65241.8212.387.891.1100.3Comparative Example 33.51237.9203.485.593.186.4Comparative Example 43.49237.6203.585.693.087.5Comparative Example 53.50238.0200.184.191.596.2Comparative Example 63.53237.4198.183.491.195.5

[0215] Referring to Table 3, in the case of Examples 1 to 6, in which the average particle diameter of the single particles and the average number of primary particles contained in the single particles were appropriately controlled, the tap density was high, so that the rolling density satisfied the range of the present example, and the electrochemical properties of capacity, efficiency, and high-temperature life characteristics were all excellent overall. On the other hand, in the case of Comparative Example 1, in which the average particle diameter of the single particles was too small as examined above, the electrochemical properties showed a similar level to the present example, but the tap density was too low, so it could be seen that the pressing density was outside the range of the present example.

[0216] In the case of Comparative Example 2, where the average number of primary particles contained in the single particle was too large, the capacity and charge / discharge efficiency were at a similar level to those of the Example, but it was confirmed that the high-temperature life characteristics were significantly reduced.

[0217] In the case of Comparative Examples 3, 4, 5, and 6, where the average number of primary particles contained in the single particles was too small, the high-temperature life characteristics were similar to those of the examples, but it was confirmed that the capacity and charge / discharge efficiency were significantly reduced.

[0218] In short, the technical point of this embodiment is to not only implement an improvement in tap density and electrode density by appropriately controlling the average particle diameter of single particles, but also to excellently implement comprehensive electrochemical characteristics of capacity and life characteristics by appropriately controlling the average number of primary particles included in the single particles.

[0219]

[0220] The present invention is not limited to the above-described embodiments, but can be manufactured in a variety of different forms. Those skilled in the art will appreciate that the present invention can be implemented in other specific forms without altering the technical spirit or essential characteristics of the present invention. Therefore, the embodiments described above should be understood as illustrative in all respects and not restrictive.

Claims

1. A nickel-containing layered lithium transition metal oxide, It is composed of a single particle comprising one primary particle and at least one quasi-single particle formed by agglomeration of multiple primary particles, The above single particles contain on average 5 to 15 primary particles, The average particle size (D50) is 5 μm to 8 μm, Positive electrode active material for lithium secondary batteries, having an average sphericity of 0.75 or more 2. In paragraph 1, A cathode active material for a lithium secondary battery, wherein the average aspect ratio of the primary particles contained in the above single particles is in the range of 1.1 to 2.

5.

3. In paragraph 1, A cathode active material for a lithium secondary battery, wherein the average sphericity is in the range of 0.75 to 0.

8.

4. In paragraph 1, Tap density is 2.2 g / cm 3 A cathode active material for a lithium secondary battery.

5. In paragraph 1, The above lithium transition metal oxide is a cathode active material for a lithium secondary battery containing nickel in an amount of 60 mol% or more based on the total mole number of transition metals.

6. In paragraph 1, The above lithium transition metal oxide is a cathode active material for a lithium secondary battery, further comprising a grain growth promoting element composed of Zr, Al, B or a combination thereof.

7. In paragraph 6, A cathode active material for a lithium secondary battery, wherein the content of the above-mentioned growth promoting element is 0.1 to 1 mol% based on the total mole number of transition metals.

8. In paragraph 1, A cathode active material for a lithium secondary battery, wherein the cathode active material further comprises a coating layer containing Co, Al or a combination thereof on the lithium transition metal oxide.

9. In paragraph 1, The above lithium transition metal oxide is a cathode active material for a lithium secondary battery represented by the following chemical formula 1: [Chemical Formula 1] Li a [Ni x Co y Mr z M1 w1 M2 W2 ]O2 In the chemical formula 1, 0.8≤a≤1.2, 0.60≤x<1, 0≤y≤0.4, 0≤z≤0.4, 0≤w1≤0.01, 0≤w2≤0.2, and x+y+z+w1+w2=1, M1 is Zr, Al, B or a combination thereof, and M2 is Y, Mg, Ti, Nb, W, Sc, Si, V, Fe, Y, Mo, Ce, Hf, Ta, La, Sr or a combination thereof.

10. The entire house; and A cathode active material layer positioned on at least one surface of the above-mentioned collector and including the cathode active material of any one of claims 1 to 10; A cathode for a lithium secondary battery having a rolling density of 3.55 g / cc or more.

11. A lithium secondary battery comprising the positive electrode for a lithium secondary battery of Article 10.

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