Cathode material powder, cathode and lithium secondary battery containing the same

Abstract

The present invention provides a positive electrode material powder that contains a lithium nickel-based oxide represented by chemical formula 1 and has a degree of monoparticulation represented by formula (1) of 0.3 to 0.8. [Chemical formula 1] Li a Ni b Co c M 1 d M 2 e O2 In the above [Chemical Formula 1], M 1 is Mn, Al or a combination thereof, M 2 is at least one selected from the group consisting of Ba, Ca, Zr, Ti, Mg, Ta, Nb and Mo, and 0.80≦a≦1.20, 0.55≦b<1, 0

Description

[Technical Field]

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2022-0002994, filed on January 7, 2022, and all contents disclosed in the documents of this Korean patent application are incorporated herein by reference.

[0002] The present invention relates to a cathode material powder for a lithium secondary battery, a cathode and a lithium secondary battery including the same, and more particularly to a cathode material powder for a lithium secondary battery that can improve high-temperature performance while minimizing an increase in resistance, and a cathode and a lithium secondary battery including the same. [Background technology]

[0003] A lithium secondary battery typically comprises a positive electrode, a negative electrode, a separator, and an electrolyte, and the positive electrode and the negative electrode contain active materials capable of intercalating and deintercalating lithium ions.

[0004] Lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), lithium manganese oxide (LiMnO2 or LiMnO4, etc.), and lithium iron phosphate (LiFePO4) have been used as positive electrode active materials for lithium secondary batteries. Among these, lithium cobalt oxide has the advantages of high operating voltage and excellent capacity characteristics, but the high cost and unstable supply of cobalt, the raw material, make it difficult to commercially apply to large-capacity batteries. Lithium nickel oxide has poor structural stability and is difficult to achieve sufficient life characteristics. On the other hand, lithium manganese oxide has excellent stability but suffers from poor capacity characteristics. To address the issues of lithium transition metal oxides containing only Ni, Co, or Mn, lithium composite transition metal oxides containing two or more transition metals have been developed. Among these, lithium nickel cobalt manganese oxide containing Ni, Co, and Mn is widely used in the field of electric vehicle batteries.

[0005] Conventional lithium nickel cobalt manganese oxides are generally in the form of spherical secondary particles formed by agglomerations of tens to hundreds of primary particles. However, when lithium nickel cobalt manganese oxides in this secondary particle form, which are agglomerations of many primary particles, are used, problems arise: primary particles tend to fall off during the rolling process during positive electrode manufacturing, resulting in particle cracks, and cracks form within the particles during charge and discharge. Particle cracks and cracks in the positive electrode active material increase the contact area with the electrolyte, increasing gas generation and active material degradation due to side reactions with the electrolyte, resulting in reduced lifespan.

[0006] On the other hand, due to the recent increasing demand for high-power, high-capacity batteries, such as those for electric vehicles, the nickel content in the positive electrode active material is gradually increasing. As the nickel content in the positive electrode active material increases, the initial capacity characteristics improve, but the highly reactive Ni 4+ A large amount of ions are generated, causing the structure of the positive electrode active material to collapse, which increases the rate of degradation of the positive electrode active material, reducing life characteristics and battery safety. In particular, performance degradation occurs rapidly when exposed to high temperatures.

[0007] To address these issues, a new technology has been proposed: increasing the calcination temperature during the production of lithium nickel cobalt manganese oxide to produce a single particle-type positive electrode active material rather than a secondary particle-type material. Single particle-type positive electrode active materials have a smaller contact area with the electrolyte than conventional secondary particle-type positive electrode active materials, resulting in fewer side reactions with the electrolyte and superior particle strength, which reduces particle cracking during electrode fabrication. Therefore, the use of single particle-type positive electrode active materials offers the advantage of excellent gas generation and lifespan characteristics. However, the use of conventional single particle-type positive electrode active materials has the problem of insufficient output performance due to their high resistance. Summary of the Invention [Problem to be solved by the invention]

[0008] In order to solve the above problems, an object of the present invention is to provide a positive electrode material powder for lithium secondary batteries which generates little gas at high temperatures, has excellent life characteristics, and also exhibits low resistance characteristics.

[0009] Another object of the present invention is to provide a positive electrode and a lithium secondary battery containing the positive electrode material powder and having excellent resistance characteristics and high-temperature characteristics. [Means for solving the problem]

[0010] In one aspect, the present invention provides a cathode material powder comprising cathode active material particles containing a lithium nickel-based oxide represented by the following chemical formula 1, and having a degree of monoparticulation represented by the following formula (1) of 0.3 to 0.8:

[0011] [Chemical formula 1] Li a Ni b Co c M 1 d M 2 e O2 In the above [Chemical Formula 1], M 1 is Mn, Al or a combination thereof, and M 2 is one or more elements selected from the group consisting of Ba, Ca, Zr, Ti, Mg, Ta, Nb, and Mo, and 0.80≦a≦1.20, 0.55≦b<1, 0 <c<0.45、0<d<0.45、0≦e≦0.20である。

[0012] Formula (1):

number

[0013] The positive electrode active material particles may be single particles consisting of one nodule or quasi-single particles which are a composite of 30 or less nodules, or may include these. Preferably, the positive electrode material powder may be a combination of single particles and quasi-single particle positive electrode active material particles.

[0014] The average particle size of the nodules of the positive electrode material powder may be 0.8 μm to 4.0 μm, and D 50 The average grain diameter may be 2.0 μm to 10.0 μm, and the average grain diameter may be 0.5 μm to 4.0 μm.

[0015] The positive electrode active material may further include a coating layer formed on the surface of the lithium nickel-based oxide and containing one or more coating elements selected from the group consisting of Al, Ti, W, B, F, P, Mg, Ni, Co, Fe, Cr, V, Cu, Ca, Zn, Zr, Nb, Mo, Sr, Sb, Bi, Si, and S.

[0016] In another aspect, the present invention provides a positive electrode including the above-described positive electrode material powder and a lithium secondary battery including the positive electrode. [Effects of the Invention]

[0017] The cathode material powder according to the present invention is characterized in that the degree of mono-particle size, as expressed by formula (1), falls within the range of 0.3 to 0.8. Secondary batteries employing cathode material powder having a degree of mono-particle size of less than 0.3 as expressed by formula (1) exhibit high gas generation during high-temperature storage and reduced high-temperature life characteristics. Secondary batteries employing cathode material powder having a degree of mono-particle size exceeding 0.8 exhibit excellent high-temperature storage and life characteristics, but high resistance reduces output and capacity characteristics. In contrast, secondary batteries employing cathode material powder having a degree of mono-particle size within the range of the present invention exhibit excellent high-temperature life characteristics, high-temperature storage, and resistance characteristics. [Brief explanation of the drawings]

[0018] [Figure 1] 1 shows scanning electron microscope images of the cathode material powders produced in Example 1 of the present invention and Comparative Examples 1 and 2. [Figure 2] FIG. 2 is a diagram showing an EBSD analysis image of a cross section of an electrode manufactured using the cathode material powder manufactured in Example 1. [Figure 3] FIG. 2 is a diagram showing an EBSD analysis image of a cross section of an electrode manufactured using the cathode material powder manufactured according to Comparative Example 1. [Figure 4] FIG. 10 is a diagram showing an EBSD analysis image of a cross section of an electrode manufactured using the cathode material powder manufactured according to Comparative Example 2. [Figure 5] 1 is a graph showing the amount of gas generated when batteries manufactured using the positive electrode materials of Examples 1 to 4 and Comparative Examples 1 and 2 are stored at high temperatures. [Figure 6] 1 is a graph showing the high-temperature life characteristics of lithium secondary batteries manufactured using the positive electrode materials of Examples 1 to 4 and Comparative Examples 1 and 2. [Figure 7] 1 is a graph showing the resistance characteristics of lithium secondary batteries manufactured using the positive electrode materials of Examples 1 to 4 and Comparative Examples 1 and 2 according to SOC (state of charge). DETAILED DESCRIPTION OF THE INVENTION

[0019] The present invention will be described in more detail below.

[0020] The terms and words used in this specification and claims should not be interpreted in a way that is limited to their ordinary and dictionary meanings, but should be interpreted in a way that is consistent with the technical idea of ​​the present invention, in accordance with the principle that the inventor himself / herself can appropriately define the concept of terms in order to best explain the invention.

[0021] In the present invention, a "grain" is a particle unit having the same crystal orientation and is the smallest particle unit that can be recognized as a single mass in an Electron Backscatter Diffraction (EBSD) map image. Grain size can be measured by image analysis of the EBSD map.

[0022] In the present invention, "single particle" means a particle consisting of one nodule, and "quasi-single particle" means a composite particle consisting of 30 or fewer nodules.

[0023] The "nodule" is a lower particle unit constituting a single particle or a quasi-single particle, and may be a single crystal having no crystalline grain boundary, or a polycrystal having no apparent grain boundary when observed at a magnification of 5,000 to 20,000 times using a scanning electron microscope.

[0024] In the present invention, "secondary particles" refer to particles formed by agglomeration of a plurality of, for example, tens to hundreds of, primary particles. Specifically, secondary particles may be agglomerates of 50 or more primary particles.

[0025] In the present invention, the term "particle" is a concept that includes any one or all of a single particle, a quasi-single particle, a primary particle, a nodule, and a secondary particle.

[0026] In the present invention, the average particle size (D mean) refers to the arithmetic mean value calculated after measuring the particle size of nodules or primary particles observed from scanning electron microscope images.

[0027] In the present invention, the "average particle size D 50 " refers to the particle size at 50% of the volume cumulative particle size distribution of the cathode material powder, and can be measured using a laser diffraction method. For example, the cathode material powder is dispersed in a dispersion medium, and then introduced into a commercially available laser diffraction particle size analyzer (e.g., Microtrac MT3000). Ultrasound of about 28 kHz is irradiated at an output of 60 W, and a volume cumulative particle size distribution graph is obtained. The particle size corresponding to 50% of the volume cumulative amount can then be determined and measured.

[0028] The inventors have conducted extensive research to develop a cathode material for lithium secondary batteries that is excellent in both high temperature and resistance characteristics, and have found that the average particle size D of the cathode material powder is 50 The present inventors have found that when the grain size satisfies a specific relationship, it is possible to minimize the increase in resistance and realize excellent high-temperature characteristics, and have completed the present invention.

[0029] Specifically, the positive electrode material powder according to the present invention has a degree of monoparticulation represented by the following formula (1) of 0.3 to 0.8.

[0030] Formula (1):

number

[0031] The n is the total number of grains measured through the electron backscatter diffraction (EBSD) analysis and may be 350 to 450, preferably 380 to 430, and more preferably 390 to 410. If the total number of measured grains is too small, it may not represent the grain size trend in the entire cathode material powder, and if it is too large, the measurement accuracy may decrease.

[0032] Electron backscattered diffraction (EBSD) analysis is a method for measuring the crystallographic phase and crystallographic orientation of a sample using its diffraction pattern and then analyzing the sample's crystallographic information based on the results. When a sample is tilted at a large angle relative to the direction of the electron beam in a scanning electron microscope, the incident electron beam scatters within the sample, producing a diffraction pattern along the sample's surface. This is called an electron backscattered diffraction pattern (EBSP). Because the electron backscattered diffraction pattern responds to the crystal orientation of the area irradiated by the electron beam, it can be used to accurately measure the sample's crystal orientation and generate an EBSD inverse pole figure (IPF) map, which separates grains with the same crystal orientation. Furthermore, image analysis of the IPF map using EBSD software can reveal information such as grain size, pattern, and orientation.

[0033] In the present invention, to perform EBSD analysis of a cathode material powder, an electrode for EBSD analysis is manufactured using the cathode material powder to be analyzed, and the manufactured electrode is then cut by ion milling. The cut electrode cross section is then irradiated with an electron beam to perform EBSD analysis. Specifically, the electrode for EBSD measurement can be manufactured by mixing the cathode material powder to be analyzed, a conductive material, and a binder in N-methylpyrrolidone to prepare an electrode slurry, coating the electrode slurry on an aluminum current collector, and drying it. Meanwhile, a rolling process is not performed during the manufacture of the electrode for EBSD analysis because rolling can cause deformation and cracking of the cathode active material particles.

[0034] 2 to 4 show IPF map images obtained by EBSD analysis of cross sections of electrodes manufactured using the cathode material powders of Example 1 and Comparative Examples 1 and 2, which will be described later, after cutting them by ion milling. As shown in Figs. 2 to 4, images divided into grain units can be obtained through EBSD analysis.

[0035] On the other hand, the above D 50 is the average particle size of the cathode material powder measured using a laser diffraction particle size analyzer, and specifically, refers to the particle size at a point where the volume cumulative amount is 50% in a volume cumulative particle size graph measured using the laser diffraction particle size analyzer.

[0036] The formula (1) is calculated by dividing the sum of the volumes of spheres whose diameter is the diameter of each grain measured through EBSD analysis by the number of grains, and then dividing this by the average particle size D of the cathode material powder. 50 The degree of monoparticle size expressed by the formula (1) is calculated by dividing the degree of monoparticle size by the number of grains in the powder of the positive electrode active material. The closer the degree of monoparticle size expressed by the formula (1) is to 1, the fewer the number of grains in the powder of the positive electrode active material, i.e., the more particles in the form of monoparticles there are. The closer the degree of monoparticle size is to 0, the more the powder of the positive electrode active material contains a large number of grains, i.e., the more particles in the form of secondary particles there are.

[0037] On the other hand, D substituted into the above formula (1) 50The grain diameter and grain radius are measured on a micrometer (μm) scale, but are dimensionless numbers without units.

[0038] According to the research of the present inventors, it has been shown that when the degree of monoparticle size represented by the formula (1) satisfies a specific range, it is possible to obtain the effects of simultaneously improving high-temperature storage characteristics, high-temperature life characteristics, and resistance characteristics.

[0039] Specifically, it was found that when a secondary battery is manufactured using a cathode material powder having a monopartition degree, as expressed by Equation (1), of 0.3 to 0.8, preferably 0.3 to 0.6, the amount of gas generated after high-temperature storage is significantly reduced and high-temperature life characteristics are significantly improved compared to when conventional cathode materials in the form of secondary particles are used, while the resistance characteristics are maintained at the same level, resulting in excellent high-temperature storage characteristics, high-temperature life characteristics, and resistance characteristics. It was also found that when a cathode material powder with a monopartition degree of less than 0.3 is used, there is no effect of improving gas generation during high-temperature storage and life characteristics, while when the monopartition degree exceeds 0.8, there is an effect of improving high-temperature life characteristics and high-temperature storage characteristics, but the resistance increases and output and capacity characteristics decrease.

[0040] On the other hand, the positive electrode material powder according to the present invention contains positive electrode active material particles containing a lithium nickel-based oxide represented by the following [chemical formula 1].

[0041] [Chemical formula 1] Li a Ni b Co c M 1 d M 2 e O2 In the above [Chemical Formula 1], the M 1 may be Mn, Al or a combination thereof, preferably Mn or a combination of Mn and Al.

[0042] Said M 2is one or more selected from the group consisting of Ba, Ca, Zr, Y, Ti, Mg, Ta, Nb, and Mo, preferably one or more selected from the group consisting of Zr, Y, Mg, and Ti, and more preferably Zr, Y, or a combination thereof. Element M2 is not necessarily included, but when included in an appropriate amount, it can play a role in promoting particle growth during firing or improving the stability of the crystal structure.

[0043] Said “a” represents the molar ratio of lithium in the lithium nickel-based oxide, and may be 0.80 ≤ a ≤ 1.20, 0.90 ≤ a ≤ 1.10, or 0.95 ≤ a ≤ 1.15. When the molar ratio of lithium satisfies the above range, a stable layered crystal structure can be formed.

[0044] Said “b” represents the molar ratio of nickel in all metals excluding lithium in the lithium nickel-based oxide, and may be 0.55 ≤ b < 1, 0.60 ≤ b < 1, 0.80 ≤ b < 1, or 0.82 ≤ b < 1. When the molar ratio of nickel satisfies the above range, excellent capacity characteristics appear. In particular, when the molar ratio of nickel is 0.80 or more, more excellent capacity characteristics can be realized.

[0045] Said “c” represents the molar ratio of cobalt in all metals excluding lithium in the lithium nickel-based oxide, and may be 0 < c < 0.45, 0 < c < 0.40, 0 < c < 0.20, or 0 < c < 0.18.

[0046] Said “d” represents the molar ratio of element M in all metals excluding lithium in the lithium nickel-based oxide 1 and may be 0 < d < 0.45, 0 < d < 0.40, 0 < d < 0.20, or 0 < d < 0.18.

[0047] Said “e” represents the molar ratio of element M in all metals excluding lithium in the lithium nickel-based oxide 2 and may be 0 ≤ e ≤ 0.20, 0 ≤ e ≤ 0.15, or 0 ≤ e ≤ 0.10.

[0048] More preferably, the lithium nickel-based oxide may be represented by the following [Chemical Formula 1-1].

[0049] [Chemical Formula 1-1] Li a1 Ni b1 Co c1 Mn d1 Al d2 M 2 e1 O2 In the above [Chemical Formula 1-1], M 2 is one or more selected from the group consisting of Ba, Ca, Zr, Ti, Mg, Ta, Nb, and Mo, and 0.80 ≦ a1 ≦ 1.20, 0.82 ≦ b1 < 1, 0 < c1 < 0.18, 0 < d1 < 0.18, 0 ≦ d2 < 0.18, 0 ≦ e1 ≦ 0.20 may hold, and preferably 0.80 ≦ a1 ≦ 1.20, 0.82 ≦ b1 < 1, 0 < c1 < 0.15, 0 < d1 < 0.15, 0 < d2 < 0.15, 0 ≦ e1 ≦ 0.10 may hold. When the lithium nickel-based oxide has the composition of the above [Chemical Formula 1-1], excellent structural stability and capacity characteristics of the positive electrode active material appear.

[0050] On the other hand, the positive electrode active material may further include a coating layer formed on the surface of the lithium nickel-based oxide and containing one or more coating elements selected from the group consisting of Al, Ti, W, B, F, P, Mg, Ni, Co, Fe, Cr, V, Cu, Ca, Zn, Zr, Nb, Mo, Sr, Sb, Bi, Si, and S.

[0051] When a coating layer exists on the surface of the lithium nickel-based oxide, the contact between the electrolyte and the lithium nickel-based oxide is suppressed by the coating layer, so that the effects of reducing the elution of transition metals and gas generation due to side reactions with the electrolyte can be obtained.

[0052] Preferably, the coating element may include Co. When a coating layer containing Co is formed on the surface of the lithium nickel-based oxide particles, the effects of suppressing side reactions with the electrolytic solution, improving output, and reducing resistance can be obtained.

[0053] Meanwhile, the positive electrode active material particles of the present invention may be single particles consisting of one nodule and / or quasi-single particles, which are composites of 30 or less nodules, preferably 2 to 20 nodules, more preferably 2 to 10 nodules, or may have a form containing these. Preferably, the positive electrode material powder of the present invention may be a combination of single particle and quasi-single particle positive electrode active material particles. This is because if the number of nodules constituting the positive electrode active material particles exceeds 30, particle cracking during electrode manufacturing increases, and internal cracks due to volumetric expansion / contraction of the nodules during charge / discharge may increase, potentially reducing the effects of improving high-temperature life characteristics and high-temperature storage characteristics.

[0054] Meanwhile, the cathode powder according to the present invention may have an average grain diameter measured by EBSD of about 0.5 μm to 4 μm, preferably 0.8 μm to 2 μm, and more preferably 0.8 μm to 1.8 μm. When the average grain diameter of the cathode powder satisfies this range, there is less rock salt phase in the lithium nickel-based oxide, resulting in more excellent resistance characteristics.

[0055] On the other hand, the D of the positive electrode material powder 50 The diameter of the positive electrode material powder may be 2.0 μm to 10.0 μm, preferably 2.0 μm to 8.0 μm. More preferably, the diameter is about 3.0 μm to 7.0 μm. 50 If the D is very small, the processability during electrode manufacturing may be reduced, the electrolyte impregnation may be reduced, and the electrochemical properties may increase. 50 If the resistance is too large, the output characteristics will be deteriorated due to the increase in resistance.

[0056] The average particle size of the nodules in the positive electrode material powder may be 0.8 μm to 4.0 μm, preferably 0.8 μm to 3 μm, and more preferably 1.0 μm to 3.0 μm. When the average particle size of the nodules is within this range, particle cracking during electrode fabrication can be minimized, and an increase in resistance can be more effectively suppressed. Here, the average particle size of the nodules refers to a value obtained by measuring the particle size of each nodule observed in an SEM image obtained by analyzing the positive electrode material powder with a scanning electron microscope, and then calculating the arithmetic mean of the measured values.

[0057] The cathode material powder of the present invention can be prepared by mixing a cathode active material precursor and a lithium source material, followed by firing the mixture.

[0058] In this case, the positive electrode active material precursor may be a commercially available positive electrode active material precursor, or may be prepared by a precursor preparation method known in the art.

[0059] For example, the precursor may be prepared by introducing an aqueous solution of a transition metal, an ammonium cation complex forming compound, and a basic compound into a reactor and stirring the mixture to carry out a coprecipitation reaction.

[0060] The transition metal aqueous solution may be prepared by dissolving a transition metal-containing source material in a solvent such as water, for example, by dissolving a nickel-containing source material, a cobalt-containing source material, or a manganese-containing source material in water. If necessary, the transition metal aqueous solution may further contain an aluminum-containing source material.

[0061] Meanwhile, the transition metal-containing raw material may be acetate, carbonate, nitrate, sulfate, halite, sulfide, or oxide of the transition metal.

[0062] Specifically, the nickel-containing source material may be, for example, NiO, NiCO3·2Ni(OH)2·4H2O, NiC2O2·2H2O, Ni(NO3)2·6H2O, NiSO4, NiSO4·6H2O, nickel halides, or combinations thereof.

[0063] The cobalt-containing source material may be, for example, CoSO4, Co(OCOCH3)2·4H2O, Co(NO3)2·6H2O, CoSO4·7H2O, or a combination thereof.

[0064] The manganese-containing source material may be, for example, Mn2O3, MnO2, Mn3O4MnCO3, Mn(NO3)2, MnSO4·H2O, manganese acetate, manganese halide, or a combination thereof.

[0065] The aluminum-containing source material may be, for example, Al2O3, Al(OH)3, Al(NO3)3, Al2(SO4)3, (HO)2AlCH3CO2, HOAl(CH3CO2)2, Al(CH3CO2)3, aluminum halide, or a combination thereof. However, in the case of Al, it does not matter if it is added together with the lithium source material in the firing step described below, rather than being added to the transition metal aqueous solution.

[0066] In this case, the amount of each transition metal-containing raw material added may be determined in consideration of the molar ratio of the transition metal in the cathode material to be finally produced. For example, in the present invention, the transition metal-containing raw materials may be added in an amount such that the molar ratio of cobalt to manganese among all transition metals contained in the aqueous transition metal solution is 0.5 or more and less than 1.

[0067] Meanwhile, the ammonium cation complexing agent may include at least one compound selected from the group consisting of NHOH, (NH)SO, NHNO, NHCl, CHCOONH, and (NH)CO, and may be added to the reactor in the form of a solution in which the compound is dissolved in a solvent, which may be water or a mixture of water and an organic solvent (e.g., alcohol) that is uniformly miscible with water.

[0068] The basic compound may be at least one compound selected from the group consisting of NaOH, KOH, and Ca(OH)2, and may be added to the reactor in the form of a solution in which the compound is dissolved in a solvent, which may be water or a mixture of water and an organic solvent (e.g., alcohol) that is uniformly miscible with water.

[0069] As described above, when the aqueous transition metal solution, the ammonium cation complexing agent, and the basic compound are charged into a reactor and stirred, the transition metal in the aqueous transition metal solution is coprecipitated to produce precursor particles in the form of transition metal hydroxide.

[0070] In this case, the aqueous transition metal solution, the ammonium cation complexing agent, and the basic compound are added in amounts such that the pH of the reaction solution falls within a desired range.

[0071] After the precursor particles are formed by the above method, the cathode active material precursor is separated from the reaction solution to obtain the cathode active material precursor. For example, the reaction solution is filtered to separate the cathode active material precursor from the reaction solution, and the separated cathode active material precursor is then washed with water and dried to obtain the cathode active material precursor. In this case, steps such as pulverization and / or classification may be performed as necessary.

[0072] Next, the positive electrode active material precursor and a lithium raw material are mixed and then calcined to prepare a lithium nickel-based oxide. 1 The metal-containing raw materials may be mixed together and fired.

[0073] The lithium source material may be a lithium-containing sulfate, nitrate, acetate, carbonate, oxalate, citrate, halide, hydroxide, or oxyhydroxide, such as Li2CO3, LiNO3, LiNO2, LiOH, LiOH·H2O, LiH, LiF, LiCl, LiBr, LiI, CH3COOLi, Li2O, Li2SO4, CH3COOLi, Li3C6H5O7, or a mixture thereof.

[0074] Meanwhile, the lithium source material and the cathode active material precursor may be mixed so that the molar ratio of Li:total metals in the precursor is 1:1 to 1.2:1, preferably 1:1 to 1.1:1. When the mixing ratio of the lithium source material and the metals in the cathode active material precursor satisfies this range, the layered crystal structure of the cathode active material is developed, and a cathode material with excellent capacity characteristics and structural stability can be produced.

[0075] Meanwhile, the calcination is carried out under conditions that allow the grains of the positive electrode active material to grow so as to satisfy the range of the degree of single particle size according to the present invention. The production of a positive electrode active material powder having a single particle and / or quasi-single particle morphology with a desired degree of single particle size is affected by the calcination conditions, which in turn are affected by the properties of the positive electrode active material precursor, such as the composition and molar ratio of components in the precursor, and the presence of any additives. For example, if the calcination temperature is not appropriate for the precursor composition, the resulting positive electrode active material powder may not have a single particle and / or quasi-single particle morphology and may not satisfy the desired degree of single particle size.

[0076] Specifically, the appropriate firing temperature for producing a positive electrode active material powder having a desired degree of mono-particle size may vary depending on the metal composition in the precursor. For example, when the nickel (Ni) content is 80 mol% or more, the firing temperature may be about 790°C to 950°C, preferably about 800°C to 900°C.

[0077] The firing may be carried out for 5 to 35 hours in an oxygen atmosphere. In this specification, the term "oxygen atmosphere" refers to an atmosphere containing sufficient oxygen for firing, including air. In particular, firing is preferably carried out in an atmosphere having a higher oxygen partial pressure than air.

[0078] Meanwhile, when preparing a cathode active material having a coating layer, the calcination step may be followed by a step of mixing the lithium composite transition metal oxide prepared by calcination with a coating raw material, followed by a heat treatment. In this case, the mixing may be solid-phase mixing or liquid-phase mixing, and the heat treatment may be performed at an appropriate temperature depending on the coating raw material. For example, the heat treatment in the coating process may be performed at a temperature of 200°C to 700°C, or 300°C to 600°C, but is not limited thereto.

[0079] Meanwhile, when preparing the cathode powder of the present invention, it is preferable not to perform a water washing process after the calcination. Conventionally, when preparing high-nickel (Ni) NCM-based lithium nickel-based oxides with a nickel (Ni) content of 80 mol% or more, a water washing process has been performed after calcination to reduce the content of lithium by-products. However, the inventors' research has shown that performing a water washing process when preparing lithium nickel-based oxides in the form of single particles or pseudo-single particles can degrade the surface properties of the lithium nickel-based oxide and increase resistance. Therefore, when preparing the cathode material of the present invention, it is preferable to not perform water washing and instead consume the remaining lithium on the surface of the lithium nickel-based oxide through the process of forming a coating layer. In this way, preparing a cathode material without washing the lithium nickel-based oxide can suppress an increase in resistance due to surface defects.

[0080] positive electrode Next, the positive electrode according to the present invention will be described.

[0081] The positive electrode according to the present invention includes a positive electrode active material layer containing the positive electrode material powder according to the present invention. Specifically, the positive electrode includes a positive electrode current collector and a positive electrode active material layer formed on the positive electrode current collector and containing the positive electrode material powder. Since the positive electrode material powder has been described above, a description of the positive electrode material powder will be omitted, and the following description will focus on components other than the positive electrode material powder.

[0082] The positive electrode current collector in the positive electrode is not particularly limited as long as it is conductive and does not induce chemical changes in the battery. 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. The positive electrode current collector may typically have a thickness of 3 to 500 μm, and fine irregularities may be formed on the surface of the positive electrode current collector to enhance adhesion of the positive electrode active material. The positive electrode current collector may be used in various forms, such as a film, sheet, foil, net, porous material, foam, or nonwoven fabric.

[0083] The positive electrode active material layer may contain a conductive material and a binder in addition to the positive electrode material powder.

[0084] The conductive material is used to impart conductivity to the electrode. Any material that exhibits electronic conductivity without causing chemical changes in the resulting battery can be used without any particular limitations. Specific examples include graphite, such as natural graphite or artificial graphite; carbon-based materials such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black, carbon fiber, and carbon nanotubes; metal powders or fibers, such as copper, nickel, aluminum, and silver; conductive whiskers, such as zinc oxide and potassium titanate; conductive metal oxides, such as titanium oxide; and conductive polymers, such as polyphenylene derivatives. These materials may be used alone or in combination. The conductive material is typically present in an amount of 1 to 30 wt %, preferably 1 to 20 wt %, and more preferably 1 to 10 wt %, based on the total weight of the positive electrode active material layer.

[0085] The binder functions to improve adhesion between positive electrode active material particles and 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, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer rubber (EPDM rubber), sulfonated EPDM, styrene-butadiene rubber (SBR), fluororubber, and various copolymers thereof. One or more of these may be used alone or in combination. The binder may be included in an amount of 1 to 30 wt %, preferably 1 to 20 wt %, and more preferably 1 to 10 wt %, based on the total weight of the positive electrode active material layer.

[0086] The positive electrode may be manufactured by a conventional method for manufacturing a positive electrode, for example, by mixing a positive electrode material, a binder, and / or a conductive material in a solvent to prepare a positive electrode slurry, applying the positive electrode slurry onto a positive electrode current collector, and then drying and rolling the slurry.

[0087] The solvent may be a solvent commonly used in the art, such as dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, or water, and may be used alone or in combination. The amount of the solvent used is sufficient to dissolve or disperse the positive electrode active material, conductive material, and binder, and to provide a viscosity that allows excellent thickness uniformity when the slurry is subsequently applied to produce a positive electrode, taking into consideration the coating thickness and manufacturing yield of the slurry.

[0088] Alternatively, the positive electrode may be manufactured by casting the positive electrode slurry on a separate support, peeling the film from the support, and laminating the film on a positive electrode current collector.

[0089] Lithium secondary battery Next, the lithium secondary battery according to the present invention will be described.

[0090] The lithium secondary battery of the present invention includes the positive electrode according to the present invention. Specifically, the lithium secondary battery includes a positive electrode, a negative electrode facing the positive electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte, the positive electrode being as described above. The lithium secondary battery may also 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.

[0091] In the lithium secondary battery, the negative electrode includes a negative electrode current collector and a negative electrode active material layer located on the negative electrode current collector.

[0092] The negative electrode current collector may be any material having high conductivity without inducing chemical changes in the battery, and may be, for example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, or aluminum-cadmium alloy. The negative electrode current collector may typically have a thickness of 3 to 500 μm. As with the positive electrode current collector, the surface of the current collector may be formed with fine irregularities to enhance the binding strength of the negative electrode active material. The negative electrode current collector may be used in various forms, such as a film, sheet, foil, net, porous material, foam, or nonwoven fabric.

[0093] The negative electrode active material layer includes a negative electrode active material, and optionally a binder and a conductive material.

[0094] The negative electrode active material may be a compound capable of reversible intercalation and deintercalation of lithium. Specific examples thereof include carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber, and amorphous carbon; metallic compounds capable of alloying with lithium such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloys, Sn alloys, and Al alloys; and SiO. β (0<β<2), metal oxides that can be doped and dedoped with lithium, such as SnO2, vanadium oxide, and lithium vanadium oxide; 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.

[0095] The negative electrode active material may be a metallic lithium thin film. The carbon material may be either low-crystalline or high-crystalline carbon. Typical low-crystalline carbons include soft carbon and hard carbon, while typical high-crystalline carbons include amorphous, plate-like, scaly, spherical, or fibrous natural or artificial graphite, kish graphite, pyrolytic carbon, mesophase pitch-based carbon fiber, mesocarbon microbeads, mesophase pitches, and high-temperature-calcined carbons such as petroleum or coal tar pitch-derived cokes.

[0096] The conductive material is used to impart conductivity to the electrode. Any material that exhibits electronic conductivity without causing chemical changes in the resulting battery can be used without any particular limitations. Specific examples include graphite, such as natural graphite or artificial graphite; carbon-based materials such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black, carbon fiber, and carbon nanotubes; metal powders or fibers, such as copper, nickel, aluminum, and silver; conductive whiskers, such as zinc oxide and potassium titanate; conductive metal oxides, such as titanium oxide; and conductive polymers, such as polyphenylene derivatives. These materials may be used alone or in combination. The conductive material is typically present in an amount of 1 to 30 wt %, preferably 1 to 20 wt %, and more preferably 1 to 10 wt %, based on the total weight of the negative electrode active material layer.

[0097] The binder functions to improve adhesion between negative electrode active material particles and between the negative electrode active material and the negative 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, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer rubber (EPDM rubber), sulfonated EPDM, styrene-butadiene rubber (SBR), fluororubber, and various copolymers thereof. These may be used alone or in combination. The binder may be included in an amount of 1 to 30 wt %, preferably 1 to 20 wt %, and more preferably 1 to 10 wt %, based on the total weight of the negative electrode active material layer.

[0098] For example, the negative electrode active material layer may be manufactured by coating a negative electrode slurry containing a negative electrode active material and, optionally, a binder and a conductive material on a negative electrode current collector and drying the coating, or by casting the negative electrode slurry on a separate support, peeling the resulting film from the support, and laminating the resulting film on the negative electrode current collector.

[0099] Meanwhile, in the lithium secondary battery, the separator separates the negative electrode and the positive electrode and provides a path for lithium ions to move. Any separator commonly used in lithium secondary batteries can be used without limitation. In particular, a separator that exhibits low resistance to electrolyte ion movement and excellent electrolyte humidification capability is preferred. Specifically, a porous polymer film, such as 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, or an ethylene / methacrylate copolymer, or a laminate structure of two or more layers thereof, may be used. Conventional porous nonwoven fabrics, such as nonwoven fabrics made of high-melting-point glass fibers or polyethylene terephthalate fibers, may also be used. To ensure heat resistance or mechanical strength, a separator coated with a ceramic component or a polymer material may be used, and may be used in a single-layer or multi-layer structure.

[0100] Furthermore, examples of the electrolyte used in the present invention include 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 production of lithium secondary batteries, but are not limited to these.

[0101] Specifically, the electrolyte may include an organic solvent and a lithium salt.

[0102] The organic solvent may be any organic solvent that can act as a medium through which ions involved in the electrochemical reaction of the battery can move. Specifically, the organic solvent may be an ester solvent such as methyl acetate, ethyl acetate, γ-butyrolactone, or ε-caprolactone; dibutyl ether; ether-based solvents such as ether or tetrahydrofuran; ketone-based solvents such as cyclohexanone; aromatic hydrocarbon-based solvents such as benzene and fluorobenzene; carbonate-based solvents such as dimethylcarbonate (DMC), diethylcarbonate (DEC), methylethylcarbonate (MEC), ethylmethylcarbonate (EMC), ethylenecarbonate (EC), and propylenecarbonate (PC); alcohol-based solvents such as ethyl alcohol and isopropyl alcohol; nitriles such as R-CN (R is a C2-C20 linear, branched, or cyclic hydrocarbon group that may contain a double bond-directed ring or an ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; or sulfolanes. Among these, carbonate-based solvents are preferred, and mixtures of cyclic carbonates (e.g., ethylene carbonate or propylene carbonate) having high ionic conductivity and high dielectric constant, which can improve the charge / discharge performance of batteries, and low-viscosity linear carbonate-based compounds (e.g., ethyl methyl carbonate, dimethyl carbonate, or diethyl carbonate) are more preferred.

[0103] The lithium salt may be any compound capable of providing lithium ions used in lithium secondary batteries. Specifically, the lithium salt may be LiPF, LiClO, LiAsF, LiBF, LiSbF, LiAlO, LiAlCl, LiCF, SO, LiCF, SO, LiN(C, F, SO), LiN(C, F, SO), LiN(CF, SO), LiCl, LiI, or LiB(C, O) . The lithium salt may be used at a concentration of 0.1 to 5.0 M, preferably 0.1 to 3.0 M. When the lithium salt concentration is within this range, the electrolyte has appropriate conductivity and viscosity, resulting in excellent electrolyte performance and efficient lithium ion migration.

[0104] In addition to the electrolyte components, the electrolyte may further contain additives for purposes such as improving battery life characteristics, suppressing battery capacity loss, and improving battery discharge capacity. Examples of additives include, but are not limited to, haloalkylene carbonate compounds such as difluoroethylene carbonate, pyridine, triethyl phosphite, triethanolamine, cyclic ethers, ethylenediamine, n-glyme, hexamethylphosphoric triamide, nitrobenzene derivatives, sulfur, quinoneimine dyes, N-substituted oxazolidinones, N,N-substituted imidazolidines, ethylene glycol dialkyl ethers, ammonium salts, pyrrole, 2-methoxyethanol, and aluminum trichloride, which may be used alone or in combination. The additives may be present in an amount of 0.1 wt % to 10 wt %, preferably 0.1 wt % to 5 wt %, based on the total weight of the electrolyte.

[0105] As described above, the lithium secondary battery including the cathode active material according to the present invention stably exhibits excellent discharge capacity, output characteristics, and capacity retention rate, and is therefore useful in the fields of portable devices such as mobile phones, notebook computers, and digital cameras, and electric vehicles such as hybrid electric vehicles (HEVs).

[0106] Therefore, according to another embodiment of the present invention, there is provided a battery module including the lithium secondary battery as a unit cell, and a battery pack including the same.

[0107] The battery module or battery pack may be used as a power source for one or more medium- to large-sized devices, such as a power tool; an electric vehicle (EV), a hybrid electric vehicle, and an electric plug-in hybrid electric vehicle (PHEV); or a power storage system.

[0108] Although the present invention may be embodied in many different forms, it is to be understood that the invention is not limited to the embodiments set forth herein, and that the invention may be embodied in various different forms, rather than in a limited manner, as described below.

[0109] Example 1 Nickel-cobalt-manganese hydroxide powder with a Ni:Co:Mn molar ratio of 83:11:6 and lithium hydroxide were mixed so that the transition metal (Ni + Co + Mn):Li molar ratio was 1:1.05, and then calcined at 870°C for 10 hours to produce a cathode material powder.

[0110] Example 2 A positive electrode material powder was produced in the same manner as in Example 1, except that the firing was carried out at 890°C.

[0111] Example 3 A positive electrode material powder was produced in the same manner as in Example 1, except that the firing was carried out at 910°C.

[0112] Example 4 A positive electrode material powder was produced in the same manner as in Example 1, except that the firing was carried out at 930°C.

[0113] Comparative Example 1 A positive electrode material powder was produced in the same manner as in Example 1, except that the firing was carried out at 770°C.

[0114] Comparative Example 2 A positive electrode material powder was produced in the same manner as in Example 1, except that the firing was carried out at 950°C.

[0115] Experimental Example 1:D 50 and measurement of nodule / primary particle size 0.1 g of each of the cathode material powders produced in Examples 1 to 4 and Comparative Examples 1 and 2 was dispersed in a dispersion medium, and then introduced into a laser diffraction particle size measuring device (Microtrac MT3000). Ultrasonic waves of about 28 kHz were irradiated at an output of 60 W to measure the D of each of the cathode material powders. 50 The measurement results are shown in Table 1 below.

[0116] In addition, SEM images of the positive electrode material powders produced in Examples 1 to 4 and Comparative Examples 1 and 2 were obtained using a scanning electron microscope.

[0117] Then, the particle size of the nodules / primary particles identified from the measured SEM images was measured, and the arithmetic mean value of these was calculated to obtain the average particle size (D mean The measurement results are shown in Table 1 below.

[0118] FIG. 1 shows SEM images of the positive electrode material powders of Example 1 and Comparative Examples 1 and 2.

[0119] Experimental Example 2: Measurement of grain size and mono-particle size The cathode material powders prepared in Examples 1 to 4 and Comparative Examples 1 and 2 were mixed with carbon black and a PVDF binder in a weight ratio of 95:2:3 in N-methylpyrrolidone to prepare an electrode slurry. The electrode slurry was applied to one side of an aluminum current collector and then dried at 130°C to prepare an electrode for EBSD analysis. No rolling was performed during the preparation of the cathode.

[0120] The cathode was cross-sectioned using an ion milling machine (Hitachi IM-500, accelerating voltage 6 kV), and electron backscatter diffraction (EBSD) analysis of the cathode cross-section was performed using a field emission scanning electron microscope (FE-SEM) (JEOL JSM7900F) equipped with an EBSD analyzer. The EBSD analysis was performed at an accelerating voltage of 15 kV, a working distance of 15 mm, and a scale with a total grain count of approximately 400 + / - 10.

[0121] The grain diameter of each particle observed from the cross section of each positive electrode was measured through EBSD analysis, and the grain radius was calculated as half of the maximum diameter of the measured grain, and the arithmetic mean value of the measured grain diameters was calculated as the average grain diameter. 50 The degree of monoparticle size was calculated by substituting the above into formula (1). The measurement results are shown in Table 1 below.

[0122] 2 to 4 show EBSD maps of the cross sections of electrodes manufactured using the positive electrode material powders of Example 1 and Comparative Examples 1 and 2. FIG.

[0123] [Table 1]

[0124] <Manufacturing lithium secondary batteries> The cathode material powders prepared in Examples 1 to 4 and Comparative Examples 1 and 2, carbon black conductive material, and PVDF binder were mixed in N-methylpyrrolidone at a weight ratio of 95:2:3 to prepare cathode slurry. The cathode slurry was applied to one side of an aluminum current collector, dried at 130°C, and rolled to prepare cathodes.

[0125] Graphite as the negative electrode active material, super C as the conductive material, and SBR / CMC as the binder were mixed in a weight ratio of 95.6:1.0:3.4 to prepare a negative electrode slurry, which was then applied to one side of a copper current collector, dried at 130°C, and rolled to prepare a negative electrode.

[0126] A separator was interposed between the positive and negative electrodes to fabricate an electrode assembly, which was then placed inside a battery case. An electrolyte solution was then injected into the case to fabricate a lithium secondary battery. The electrolyte solution was prepared by dissolving LiPF6 at a concentration of 1M in a mixed organic solvent of ethylene carbonate / dimethyl carbonate / diethyl carbonate in a volume ratio of 1:2:1, and adding 2 wt% vinylene carbonate (VC).

[0127] Experimental Example 3: Evaluation of high-temperature storage characteristics Each of the lithium secondary batteries fabricated above was charged to 4.2 V at 1C in CC-CV mode, and then the secondary battery was disassembled to separate the positive electrode. Then, 400 mg of the positive electrode and 400 μL of electrolyte were placed in a pouch-type battery case and sealed to fabricate a cell. The cell was then stored at 60°C for 10 weeks, and the change in cell volume (ΔCell volume, unit: ΔmL) before and after high-temperature storage was measured. The change in cell volume was measured by placing the cell in water and measuring the volume change of the water. The measurement results are shown in Figure 5 and Table 2.

[0128] Experimental example 4: Evaluation of high-temperature life characteristics Each of the lithium secondary batteries prepared above was charged at 45°C in CC-CV mode at 1 C to 4.25 V and then discharged at a constant current of 0.05 C to 2.5 V, and after 300 charge-discharge cycles, the capacity retention was measured to evaluate the lifespan characteristics. The measurement results are shown in Figure 6 and Table 2.

[0129] [Table 2]

[0130] Experimental Example 5: Evaluation of resistance characteristics The cathode material powders prepared in Examples 1 to 4 and Comparative Examples 1 and 2, carbon black conductive material, and PVDF binder were mixed in N-methylpyrrolidone at a weight ratio of 95:2:3 to prepare cathode slurry. The cathode slurry was applied to one side of an aluminum current collector, dried at 130°C, and rolled to prepare cathodes.

[0131] A lithium metal electrode was used as the negative electrode.

[0132] An electrode assembly was fabricated by interposing a separator between the positive and negative electrodes, and then placed inside a battery case. An electrolyte solution was then injected into the case to fabricate a coin-half cell. The electrolyte solution was prepared by dissolving 1M LiPF6 in a mixed organic solvent of ethylene carbonate / dimethyl carbonate / diethyl carbonate in a volume ratio of 1:2:1, and adding 2 wt% vinylene carbonate (VC).

[0133] The coin half-cell was charged and discharged once from 2.5 to 4.25 V under a 0.1 C / 0.1 C condition, and then charged again to 4.25 V. The resistance (unit: Ω) was measured at each SOC while discharging 10% of the cell discharge capacity. The resistance was measured from the voltage change when a current density of 1.0 C was applied for 10 seconds at each SOC. The measurement results are shown in Figure 7.

[0134] 5 to 7, it can be seen that the batteries employing the cathode material powders of Examples 1 to 4, whose monoparticle degree of Equation (1) satisfies the range of the present invention, have significantly better high-temperature life characteristics and high-temperature storage characteristics than the battery employing the cathode material powder of Comparative Example 1, and have resistance characteristics equivalent to those of the battery of Comparative Example 1, with almost no increase in resistance.

[0135] In contrast, in the case of the battery using the cathode material powder of Comparative Example 2, the high-temperature life characteristics and high-temperature storage characteristics were at the same level as those of the battery using the cathode material powder of Example 1, but it can be confirmed that the resistance increased significantly.

Claims

1. The positive electrode active material particles include a lithium nickel-based oxide represented by the following chemical formula 1: A cathode material powder having a degree of monoparticle size represented by the following formula (1) of 0.3 to 0.8: [Chemical formula 1] Li ａ Ni ｂ Co ｃ M １ ｄ M ２ ｅ O ２ In the above [Chemical Formula 1], M １ is Mn, Al or a combination thereof, M ２ is one or more elements selected from the group consisting of Ba, Ca, Zr, Y, Ti, Mg, Ta, Nb, and Mo, and 0.80≦a≦1.20, 0.55≦b<1, 0<c<0.45, 0<d<0.45, and 0≦e≦0.

20. Formula (1): [Equation 1] In the formula (1), Ri is the radius of the i-th grain measured when an electrode manufactured using the cathode material powder is subjected to ion milling and then the electrode is analyzed by electron backscatter diffraction (EBSD), n is the total number of grains measured through electron backscatter diffraction (EBSD) analysis, and is 350 to 450; The above D ５０ is the particle size at a point where the volume cumulative amount is 50% in a volume cumulative particle size graph of the cathode material powder measured using a laser diffraction particle size analyzer, The average grain diameter of the positive electrode material powder is 0.5 μm to 4 μm, The positive electrode material powder has a D 50 of 2.0 μm to 10.0 μm, the average particle size of the nodules of the positive electrode material powder is 0.8 μm to 4.0 μm; The Ri and D 50 in the formula (1) are values ​​measured on a micrometer (μm) scale, but are dimensionless numbers without units.

2. The cathode material powder according to claim 1, wherein the cathode active material particles include at least one of a single particle consisting of one nodule and a quasi-single particle which is a composite of 30 or less nodules.

3. The cathode material powder according to claim 1 , wherein the cathode material powder is a combination of single particle and pseudo-single particle shaped cathode active material particles.

4. 2. The cathode material powder according to claim 1, wherein the cathode material powder has a degree of monoparticulation represented by formula (1) of 0.3 to 0.

6.

5. 2. The positive electrode material powder according to claim 1, wherein in the [Chemical Formula 1], 0.80≦b<1, 0<c<0.20, 0<d<0.20, and 0≦e≦0.

10.

6. The lithium nickel-based oxide is represented by the following [Chemical Formula 1-1]: [Chemical formula 1-1] Li ａ１ Ni ｂ１ Co ｃ１ Mn ｄ１ Al ｄ２ M ２ ｅ１ O ２ In the above [Chemical Formula 1-1], M ２ is one or more elements selected from the group consisting of Ba, Ca, Zr, Ti, Mg, Ta, Nb, and Mo, and 0.80≦a1≦1.20, 0.82≦b1<1, 0<c1<0.18, 0<d1<0.18, 0≦d2<0.18, 0≦e1≦0.

20.

7. 2. The cathode material powder according to claim 1, wherein the cathode active material further comprises a coating layer formed on the surface of the lithium nickel-based oxide and containing one or more coating elements selected from the group consisting of Al, Ti, W, B, F, P, Mg, Ni, Co, Fe, Cr, V, Cu, Ca, Zn, Zr, Nb, Mo, Sr, Sb, Bi, Si, and S.

8. A positive electrode comprising the positive electrode material powder according to any one of claims 1 to 7; and a current collector.

9. A lithium secondary battery comprising the positive electrode according to claim 8; and a negative electrode.

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