Positive electrode material powder and manufacturing method for positive electrode material powder

Abstract

The present invention relates to a positive electrode material powder and a manufacturing method therefor, the positive electrode material powder comprising a single-particle-type lithium nickel-based oxide, in which the content of nickel among the metals other than lithium is 80 mol% or more, and has a D50 of 5.0㎛ or more and a crystal strain of 280×10-6 or less.

Description

Cathode material powder and method for producing the cathode material powder This application claims the benefit of priority to Korean Patent Application No. 10-2024-0014418, filed January 30, 2024, the entire contents of which are incorporated herein by reference. The present invention is D 50 And it relates to a cathode material powder with controlled crystal deformation and a method for producing the same, a cathode material including the cathode material powder, and a lithium secondary battery. With the rapid growth of industries that use lithium secondary batteries, such as mobile phones, laptops, and electric vehicles, active research and development efforts are underway to improve the performance of lithium secondary batteries. Lithium secondary batteries produce electrical energy through oxidation and reduction reactions that occur when lithium ions are inserted and removed from the positive and negative electrodes. Lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, and lithium iron phosphate compounds have been primarily used as cathode active materials for lithium secondary batteries. Furthermore, to improve the low thermal stability of lithium nickel oxide while maintaining its excellent reversible capacity, lithium composite metal oxides (hereinafter simply referred to as "NCM oxides") have been developed, in which some of the nickel is replaced with cobalt and manganese. Recently, with the increasing demand for high-power, high-capacity batteries, such as those for electric vehicles, efforts are actively being made to increase the nickel content in NCM oxides. However, high-Ni NCM oxides exhibit significant lattice structural instability due to cation mixing and oxygen desorption, and contain significant amounts of lithium impurities remaining on the surface. This limits their application as cathode materials, as large amounts of gas are generated during high-temperature storage or charge / discharge processes. The present invention aims to provide a cathode material powder capable of simultaneously achieving high capacity characteristics, particle durability, and resistance characteristics, and a method for producing the same. [1] The present invention comprises a single particle lithium nickel oxide having a nickel content of 80 mol% or more among metals other than lithium, and D 50 This is 5.0㎛ or more, and the crystal strain is 280×10 -6 Below, we provide cathode material powder. [2] The present invention provides a cathode material powder having a cation mixing ratio of 1.0 at% or less in the above [1]. [3] The present invention provides a cathode material powder having a particle size reduction rate (K) of 20% to 30% according to the following formula 1 of the cathode material powder in the above [1] or [2]. [Formula 1] In the above equation 1, D 50 D of the above cathode material powder 50 And, D 50 ' The above cathode material powder was placed in a circular mold with a diameter of 13 mm and pressed with a force of 9 tons, and then measured. 50 am. [4] The present invention, in at least one of the above [1] to [3], D of the positive electrode powder min A cathode material powder having a size of 0.5㎛ or more is provided. [5] The present invention, in at least one of the above [1] to [4], D of the positive electrode powder max A cathode material powder having a diameter of 10㎛ to 20㎛ is provided. [6] The present invention provides a cathode material powder, wherein in at least one of the above [1] to [5], the pellet density of the cathode material powder is 3.50 g / cc or more, and the pellet density is a value obtained by dividing the weight of the cathode material powder by the volume of the pellet after putting the cathode material powder into a circular mold having a diameter of 13 mm and pressing it with a force of 9 tons to manufacture a pellet. [7] The present invention provides a cathode material powder, wherein, in at least one of the above [1] to [6], the tap density of the cathode material powder is 2.00 g / cc to 2.50 g / cc. [8] The present invention provides a cathode material powder, wherein in at least one of the above [1] to [7], the lithium nickel-based oxide has a composition represented by the following chemical formula 1. [9] The present invention provides a cathode material powder, wherein in at least one of the above [1] to [8], the lithium nickel-based oxide has a nickel content of 85 mol% or more among metals other than lithium.

[0010] The present invention provides a cathode material powder comprising a coating layer containing a Co element on the surface of the lithium nickel-based oxide particle in at least one of the above [1] to [9].

[0011] The present invention provides a method for producing a cathode material powder according to at least one of [1] to

[0010] , comprising the steps of: preparing a mixture by mixing a precursor having a nickel content of 80 mol% or more with a lithium raw material; first firing the mixture at 750°C to 890°C; and second firing the first-fired sintered body at 660°C to 750°C for 9 to 14 hours.

[0012] The present invention provides a method for manufacturing a cathode material powder, further comprising a step of milling the secondarily fired sintered body at a speed of 1,000 rpm to 2,500 rpm in the above

[0011] .

[0013] The present invention provides a method for producing a cathode material powder, which does not include a washing step after the secondary firing in the above

[0011] or

[0012] .

[0014] The present invention provides a positive electrode comprising a positive electrode powder according to at least one of the above [1] to

[0010] .

[0015] The present invention provides a lithium secondary battery comprising: a positive electrode according to the above

[0014] ; a negative electrode including a negative electrode active material; a separator interposed between the positive electrode and the negative electrode; and an electrolyte. The present invention is a D that can optimize the particle size reduction rate before / after rolling in a cathode powder containing a high-nickel lithium nickel oxide. 50 and provides a numerical range of decision strains. D 50 And the cathode material powder having a crystal deformation degree satisfying the scope of the present invention has the advantage of excellent lithium mobility as the particle size reduction rate is optimized and less fine powder is generated during the rolling process. Therefore, the above cathode material powder can contribute to improving the cycle performance of a lithium secondary battery and reducing the amount of gas generated during high-temperature storage. Figure 1 is an SEM photograph of the cathode material powder manufactured in Example 1. Figure 2 is an SEM photograph of the cathode material powder manufactured in Example 2. Figure 3 is an SEM photograph of the cathode material powder manufactured in Comparative Example 1. Figure 4 is an SEM photograph of the cathode material powder manufactured in Comparative Example 2. Figure 5 is an SEM photograph of the cathode material powder manufactured in Comparative Example 3. Figure 6 is a diagram showing the volume change according to high-temperature storage of a cell to which the cathode material powder of the examples and comparative examples is applied. Figure 7 is an SEM photograph of the cathode material powder manufactured in Comparative Example 4. Hereinafter, the present invention will be described in more detail to help understand the present invention. In the present invention, “single particle type” means a particle composed of 30 or fewer nodules, and is a concept that includes a single particle composed of one nodule and a pseudo-single particle which is a composite of 2 to 30 nodules. The above "nodule" is a sub-particle unit that constitutes a single particle and a pseudo-single particle, and may be a single crystal without a crystalline grain boundary, or a polycrystal with no apparent grain boundary when observed under a magnification of 5,000 to 20,000 times using a scanning electron microscope. In the present invention, “particle” is a concept including one or all of a single particle, a pseudo-single particle, a primary particle, and a nodule. In the present invention, "D 50 ", "D min " and "D max " refers to the particle size, minimum particle size, and maximum particle size corresponding to 50% of the volume accumulation amount in the volume accumulation particle size distribution of the corresponding particle powder, and can be measured using a laser diffraction method. For example, after dispersing the positive electrode active material powder in a dispersion medium, it can be measured by introducing it into a commercially available laser diffraction particle size measuring device (e.g., Malvern, Mastersizer 3000) and irradiating it with ultrasonic waves of about 28 kHz at an output of 60 W, obtaining a volume accumulation particle size distribution graph, and finding the particle size at the point where the volume accumulation amount is 50% in the obtained volume accumulation particle size distribution graph. In the present invention, the “cation mixing ratio” refers to the nickel ion (Ni) based on the total amount of lithium sites (Li sites) in the lithium layer of the lithium nickel oxide having a layered structure. 2+ ) refers to the ratio (at%) of the mixture, and can be measured through X-ray diffraction analysis (XRD). In the present invention, “at%” means atomic percentage. In the present invention, “crystal strain” is a dimensionless number representing the degree of lattice distortion caused by a defect, i.e., the degree of crystal lattice deformation, and can be measured through Rietveld refinement analysis of XRD data. The above X-ray diffraction analysis can be performed using a Bruker D8 Endeavor (light source: Cu-Kα, λ=1.54Å) equipped with a LynxEye XE-T-position sensitive detector. The sample is placed in the groove of a general powder holder, the sample surface is leveled using a slide glass, and the sample is filled so that the height matches the edge of the holder. Then, it can be performed under the conditions of FDS 0.5°, 2θ=15° to 90°, step size=0.02°, and total scan time=approximately 20 minutes. Rietveld refinement is performed on the measured data by considering the charge at each site (metals at transition metal sites are +3, Ni at Li sites is +2) and cation mixing. Instrumental broadening during analysis is performed using the Fundamental Parameter Approach (FPA) implemented in the Bruker TOPAS program, and the entire peaks of the measurement range are used for fitting. Peak shape is fitted using only the Lorenzian contribution as the FP (First Principle) among the peak types available in TOPAS. In the present invention, the "pellet density" can be obtained by placing a certain amount of sample in a cylindrical load cell or a circular mold, applying force to compress it into a pellet shape, and then calculating the density from the volume and weight of the pellet. For example, it can be measured using an automatic pellet press (Auto Pellet Press, 3887.4) from Carver or a pellet press (Pellet Press, 4350.L) from Carver. In the present invention, "tap density" can be measured using a method commonly used in the art for measuring the degree of filling of a sample per unit volume. For example, it can be the density (sample weight / volume) calculated from the change in volume by applying a constant force to a measuring container containing a sample in accordance with the measuring device and method specified in ASTM B527. Specifically, it can be measured using a GEOPYC 1365 tap density meter from Micromeritics by vibrating it horizontally until a force of 108 N is applied. Below, each component of the present invention is described in more detail. cathode powder According to one embodiment of the present invention, a cathode powder comprises a single particle lithium nickel oxide having a nickel content of 80 mol% or more among metals other than lithium, and D 50 This is 5㎛ or more, and the crystal strain is 280×10 -6 It is as follows. In order to overcome the limitations of the high-Ni cathode material described above, the present invention controls the cathode material to be in the form of a single particle, rather than in the form of secondary particles formed by agglomeration of tens to hundreds of particles as in the past. The single-particle cathode material has a smaller contact area with the electrolyte than the secondary particle cathode material, and thus exhibits less side reactions with the electrolyte. Furthermore, the superior particle strength reduces particle breakage during the electrode manufacturing process, thereby contributing to reducing gas emissions from lithium secondary batteries. However, cathode materials in the form of single particles have relatively unfavorable characteristics in terms of resistance due to the fact that lithium mobility is low because the interface between primary particles that serve as a passage for lithium ions within the particles is small, the surface structure is easily changed to a rock salt phase, which is electrochemically inactive, because it is manufactured at a relatively high firing temperature, and the lithium byproducts remain in excess on the surface due to the high firing temperature, and the washing process introduced to remove them causes damage to the surface structure. In other words, it is a difficult task to obtain a cathode material that has excellent balance in capacity characteristics, particle durability, and resistance characteristics, rather than being biased toward any one characteristic. Accordingly, the present inventors have developed a D of cathode powder 50 And the crystal strain was introduced as an indicator to select these cathode materials, and for cathode materials with a nickel content of 80 mol% or more and in the form of single particles, D 50 This is 5.0㎛ or more, and the crystal strain is 280×10 -6 In the following cases, it was confirmed that capacity characteristics, particle durability, and resistance characteristics can all be secured to a certain level or higher. Specifically, the crystal deformation of the cathode powder is 280×10 -6 If it exceeds , there is a problem that the structural stability is lowered and the initial charging capacity is reduced. However, D of the cathode powder 50If it is less than 5㎛, the density between particles is low, making it difficult to secure electrical conductivity, and the amount of fine particles generated during rolling increases, making it difficult to maintain high-temperature durability, so even if the crystal deformation range is satisfied, the same effect cannot be achieved. In addition, D 50 In the case of single particles less than 5㎛, the strong crushing strength increases the amount of fine particles, which may lead to a decrease in the phase stability of the slurry, a decrease in the solid content during electrode coating, slurry gelation, and an increase in viscosity, which may affect the coating speed, etc., and thus may have a disadvantage in terms of process productivity. Specifically, the D of the cathode material powder 50 The silver may be 5.0㎛ to 8.5㎛, specifically 5.0㎛ to 7.0㎛, and more specifically 5.0㎛ to 6.0㎛. The cation mixing ratio of the above cathode powder may be 1.0 at% or less, 0.8 at% or less, 0.5 at% or less, 0.3 at% or less, or 0.1 at% or less. The cathode powder according to the present invention has a low crystal deformation and an optimized D50, so that the crystal structure is excellent in stability and the particle size is maintained uniformly, so that the cation mixing ratio can be implemented at this low level. Cation mixing is performed by Li having similar ionic radii. + Wow Ni 2+ Since it means the phenomenon of forming a crystal by exchanging positions with each other, if the cation mixing ratio is high, Li + Li when inserted and removed + Ni present in the spatial layer 2+ It is preferable that it be less than 1.0 at%, as it can act as a resistance component and reduce the charge / discharge efficiency. The particle size reduction rate (K) of the above cathode material powder according to the following formula 1 may be 20% to 30%. [Formula 1] In the above equation 1, D 50D of the above cathode material powder 50 And, D 50 ’ The above cathode material powder was placed in a circular mold with a diameter of 13 mm and pressed with a force of 9 tons, and then measured. 50 am. D 50 This is 5.0㎛ or more, and the crystal strain is 280×10 -6 In the following cases, the stability of the crystal structure and the uniformity of the particle size are secured simultaneously, so that particle crushing is minimized, and thus the particle size reduction rate can be controlled in this way. When the particle size reduction rate (K) is less than 20%, the interface between the primary particles, which serve as the diffusion path of lithium ions within the particles, is small, so the diffusion path of lithium ions becomes longer, which reduces lithium mobility, and thus the resistance increase as the cycle progresses may become more severe. In addition, when the particle size reduction rate (K) exceeds 30%, the rolled fines increase due to the small-sized single particles remaining after filling the gaps between the large-sized single particles, which may increase the amount of gas generated during high-temperature storage and reduce the life characteristics. Preferably, the particle size reduction rate (K) may be 21% to 29%, and more preferably 23% to 28%. In the above equation 1, D 50 and D 50 ' represent the particle sizes of the cathode material powder before and after rolling during electrode manufacturing, respectively. D of the above cathode powder min The size of the positive electrode powder may be 0.5㎛ or more, specifically 0.6㎛ or more, and may be 2.0㎛ or less, 1.5㎛ or less. In addition, the D of the positive electrode powder max It may be 10㎛ to 20㎛, specifically 11㎛ to 15㎛. Meanwhile, the pellet density of the cathode material powder may be 3.50 g / cc or more, preferably 3.55 g / cc or more, and more preferably 3.60 g / cc or more, in which case the rollability is excellent, making it easy to achieve high density. However, D 50 Considering the practical rolling conditions that can be applied to single particles of 5.0㎛ or more, it may be less than 3.75g / cc. Additionally, the tap density of the cathode material powder may be 2.00 g / cc to 2.50 g / cc, preferably 2.10 g / cc to 2.50 g / cc, and more preferably 2.20 g / cc to 2.40 g / cc. When the pellet density and tap density are within the above ranges, the rolling density can be adjusted to a desirable level to improve the energy density. Meanwhile, according to one embodiment of the present invention, the content of nickel among the metals other than lithium in the lithium nickel-based oxide may be 85 mol% or more, preferably 90 mol% or more, more preferably 93 mol% or more, but may be 99 mol% or less. In this case, there is an advantage of being able to implement high capacity. In addition, the lithium nickel-based oxide may have a composition represented by the following chemical formula 1. [Chemical Formula 1] Li 1+x (Ni a Co b M 1 c M 2 d )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, Mo, W, Cu, Fe, V, Cr, Zn, In, Y, La, Sr, Ga, Sc, Gd, Sm, Ce and B, x, a, b, c and d are 0≤x≤0.50, 0.80≤a<1, 0 respectively <b≤0.20, 0≤c≤0.20, 0≤d≤0.10, a+b+c+d=1을 만족한다. The above 1+x represents the molar ratio of lithium in the lithium nickel-based oxide, and may be 0≤x≤0.20, or 0≤x≤0.10. When the molar ratio of lithium satisfies the above range, a crystal structure can be stably formed. The above a represents the molar ratio of nickel among the total metal excluding lithium in the lithium nickel-based oxide, and may be 0.85≤a<1, 0.90≤a<1, or 0.93≤a<1. When the molar ratio of nickel satisfies the above range, a high energy density is exhibited, enabling high capacity implementation. The above b represents the molar ratio of cobalt among all metals excluding lithium in the lithium nickel-based oxide, and is 0. <b≤0.12, 0<b≤0.09, 또는 0<b≤0.07일 수 있다. 코발트의 몰비가 상기 범위를 만족할 때, 양호한 저항 특성 및 출력 특성을 구현할 수 있다. The above c is M of all metals excluding lithium in the lithium nickel oxide. 1 It represents the molar ratio of elements, 0 <c≤0.12, 0<c≤0.07, 또는 0<c≤0.05일 수 있다. 한편 상기 M 1 may be Mn; or a combination of Mn and Al, preferably Mn. The above d is M of all metals excluding lithium in the lithium nickel oxide. 2 Indicates the molar ratio of elements, and d may be 0≤d≤0.08, 0≤d≤0.05, or 0≤d≤0.03. Meanwhile, the cathode material powder may include a coating layer containing a Co element on the surface of the lithium nickel-based oxide particles. More specifically, the coating layer may include Li, which is a reaction product of Co and a lithium byproduct. eCoO2(0 <e<1)을 포함할 수 있다. 이 경우 상기 코팅층에 의해 리튬 니켈계 산화물과 전해액의 접촉이 억제되어 전해액과의 부반응이 감소하고 이로 인해 수명 특성이 개선되는 효과를 얻을 수 있다. Meanwhile, the cathode material powder may be a single particle composed of one nodule and / or a quasi-single particle which is a composite of 30 or fewer, preferably 2 to 20, and more preferably 2 to 10 nodules, or may be in a form including these. Preferably, the cathode material powder according to the present invention may be composed of a combination of single particles and quasi-single particle-type cathode active material particles. When the number of nodules constituting the cathode active material particles exceeds 30, particle breakage increases during electrode manufacturing, and internal cracks occur more due to volume expansion / contraction of the nodules during charge / discharge, which may reduce the effect of improving high-temperature storage characteristics. Method for manufacturing cathode material powder Hereinafter, a method for manufacturing a cathode material powder according to the present invention will be described. A method for manufacturing a cathode material powder according to one embodiment of the present invention comprises the steps of: preparing a mixture by mixing a precursor having a nickel content of 80 mol% or more with a lithium raw material; and first firing the mixture at 750°C to 890°C; and second firing the first-fired sintered body at 660°C to 750°C for 9 to 14 hours. Next, each step is explained. In the step of preparing a mixture by mixing a precursor having a nickel content of 80 mol% or more with a lithium raw material, first, a precursor having a nickel content of 80 mol% or more is mixed with a lithium raw material in a reactor. Meanwhile, the precursor may be in the form of a hydroxide, oxide or carbonate, and specifically may be in the form of a hydroxide, and more specifically may have a composition represented by the following chemical formula 2. [Chemical Formula 2] Ni a1 Co b1 M 1 c1 M 2 d1 (OH)2 In the above chemical formula 2, 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, Mo, W, Cu, Fe, V, Cr, Zn, In, Y, La, Sr, Ga, Sc, Gd, Sm, Ce and B, a1, b1, c1 and d1 are 0.80≤a1<1, 0 respectively <b1≤0.20, 0≤c1≤0.20, 0≤d1≤0.10, a1+b1+c1+d1=1을 만족한다. The above a1 represents the molar ratio of nickel among all metals excluding lithium in the precursor, and may be 0.85≤a1<1, 0.90≤a1<1, or 0.93≤a1<1. The above b1 represents the molar ratio of cobalt among all metals excluding lithium in the precursor, and is 0. <b1≤0.12, 0<b1≤0.09, 또는 0<b1≤0.07일 수 있다. The above c1 is M among all metals except lithium in the precursor. 1 It represents the molar ratio of elements, 0 <c≤0.12, 0<c≤0.07, 또는 0<c≤0.05일 수 있다. 한편 상기 M 1 may be Mn; or a combination of Mn and Al. The above d1 is M among all metals except lithium in the precursor. 2 Indicating the molar ratio of elements, d1 may be 0≤d1≤0.08, 0≤d1≤0.05, or 0≤d1≤0.03. The above precursor may be purchased and used as a commercially available precursor, or may be manufactured and used according to a precursor manufacturing method known in the art. Meanwhile, as the lithium raw material, lithium-containing sulfate, nitrate, acetate, carbonate, oxalate, citrate, halide, hydroxide or oxyhydroxide may be used, and for example, Li2CO3, LiNO3, LiNO2, LiOH, LiOHㆍH2O, LiH, LiF, LiCl, LiBr, LiI, CH3COOLi, Li2O, Li2SO4, CH3COOLi, Li3C6H5O7 or a mixture thereof may be used. The above lithium raw material and precursor may be mixed so that the molar ratio of Li:total metal in the precursor is 1:1 to 1.2:1, preferably 1:1 to 1.1:1. When the mixing ratio of the lithium raw material and the metal in the precursor satisfies the above range, the layered crystal structure of the lithium nickel-based oxide is well developed, so that a cathode material with excellent capacity characteristics and structural stability can be manufactured. Next, a step of calcining the mixture to produce a single-particle sintered body is performed. Specifically, the calcination includes a first calcination and a second calcination, and the first calcination can be performed by calcining the mixture in an oxygen atmosphere at 750°C to 890°C, preferably 800°C to 890°C, and more preferably 800°C to 850°C for 8 to 16 hours. The first calcination is a step for increasing the structural completeness of the lithium nickel-based oxide and for making it single-particle, and considering that the higher the calcination temperature, the better the particle growth reaction occurs, which can increase the single-particle degree, it is preferably 750°C or higher. However, considering that the reactivity between the precursor and the lithium raw material decreases if under-calcination occurs in the first calcination, and that the Li2O content increases due to high-temperature calcination, which is easily converted to LiOH, and LiOH is easily converted again to Li2CO3, which may cause side reactions with the electrolyte and gas generation, it is preferable that it be 890℃ or lower. Here, the oxygen atmosphere means an atmosphere containing oxygen sufficient for calcination, including the atmosphere. In particular, it is preferable to perform the calcination in an atmosphere with a higher oxygen partial pressure than the atmosphere. Meanwhile, the secondary firing may be performed at 660°C to 750°C, preferably 660°C to 720°C, and more preferably 680°C to 700°C, in an oxygen atmosphere on the primary fired body. In addition, the secondary firing may be performed for 9 to 14 hours, preferably 10 to 14 hours, and more preferably 10 to 12 hours. Since the secondary firing is performed to increase the degree of single crystallinity, it is preferable that the temperature of the secondary firing be 660°C or higher. However, considering that strain and cation mixing ratio may increase if the firing temperature is excessively high, it is preferable that it does not exceed 750°C. Meanwhile, a coating raw material containing Co element can be added during the secondary firing, and in this case, the lithium byproduct remaining on the surface of the fired body reacts with the coating raw material to form an LCO-like phase, specifically, Li, on the surface of the lithium nickel-based oxide particles. e CoO2(0 <e<1)를 포함하는 코팅층이 형성된다. Co 원소를 포함하는 코팅층에 의해 수명 개선 효과가 있을 뿐만 아니라, 코팅층이 형성되는 과정에서 표면에 잔류하는 리튬 부산물이 소모되므로 리튬 부산물에 의해 야기되는 부반응이 감소하는 효과도 있다. At this time, the coating raw material may be at least one selected from the group consisting of Co(OH)2, CoO, Co2O3, Co3O4, CoO(OH) and Co(OCOCH3)2, and the coating raw material may be present in an amount of 1 mol% to 10 mol%, preferably 2 mol% to 5 mol%, based on the total mole number of the primary sintered body. Meanwhile, the method for manufacturing the cathode material powder may not include the post-sintering washing step. When manufacturing high-nickel NCM oxides with a nickel content of 80 mol% or more, a post-sintering washing process is typically performed to remove lithium byproducts present on the particle surface. However, since the surface properties of the lithium nickel-based oxide deteriorate during the washing process, increasing resistance, it is preferable not to include the washing step. In the present invention, since side reactions due to lithium byproducts can be prevented through cobalt coating, the washing step can be omitted, thereby solving the problem of increased resistance due to washing. In addition, a step of milling the sintered body may be performed after the secondary firing. Specifically, the method for manufacturing a cathode material powder according to one embodiment of the present invention may further include a step of milling the sintered body subjected to the secondary firing at a speed of 1,000 rpm to 2,500 rpm, preferably 1,200 rpm to 2,300 rpm. The above milling process is to remove large particles and obtain a particle size of the cathode powder within a desired numerical range. During the high-temperature firing process, coagulation and / or agglomeration between adjacent particles may occur, resulting in the generation of large particles, which may lead to a deterioration in rolling characteristics. Therefore, in the present invention, by performing a milling process, large particles are removed and the above-described D is finally obtained. 50 A cathode powder having the above properties can be formed. The above milling can be performed using a general milling method known in the art, for example, a jet-mill method, and the speed refers to a classifier speed. Meanwhile, it is preferable that the above milling be performed in an atmosphere with little moisture, such as a dry air atmosphere. This is because exposure of lithium nickel-based oxide to moisture increases the generation of lithium byproducts and may deteriorate the surface properties of the active material. anode Next, the anode according to the present invention will be described. The positive electrode according to the present invention comprises the aforementioned positive electrode material powder. Specifically, the positive electrode comprises: a positive electrode current collector; and a positive electrode active material layer formed on the positive electrode current collector and comprising the positive electrode material powder. Since the positive electrode material powder has been described above, a description thereof will be omitted, and components other than the positive electrode material powder will be described below. In the above positive electrode, the positive electrode current collector is not particularly limited as long as it is conductive and does not cause a chemical change in the battery, and for example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, etc. may be used. In addition, the positive electrode current collector may typically have a thickness of 3 to 500 ㎛, and fine unevenness may be formed on the surface of the positive electrode current collector to increase the adhesive strength of the positive electrode material powder. For example, it may be used in various forms such as a film, sheet, foil, net, porous body, foam, or non-woven fabric. Additionally, the positive electrode active material layer may include a conductive material and a binder together with the positive electrode material powder described above. The above cathode material powder may typically be included in an amount of 80 wt% to 99 wt%, preferably 90 wt% to 98 wt%, and more preferably 95 wt% to 97 wt%, based on the total weight of the cathode active material layer. 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 particular limitation. Specific examples include graphite such as natural graphite or artificial graphite; carbon black such as acetylene black, Ketjen black, channel black, furnace black, lamp black, and summer black; carbon-based materials such as carbon fibers and carbon nanotubes; metal powders or metal fibers such as copper, nickel, aluminum, and silver; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives, and the like. One of these may be used alone or a mixture of two or more may be used. The conductive material may typically be included in an amount of 0.5 wt% to 20 wt%, preferably 1 wt% to 10 wt%, and more preferably 1 wt% to 5 wt%, based on the total weight of the positive electrode active material layer. The above binder serves to improve adhesion between positive electrode active material particles and adhesion between the positive electrode active material and the positive electrode current collector. Specific examples thereof 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 of these may be used alone or a mixture of two or more thereof. The above binder may be included in an amount of 0.5 wt% to 20 wt%, preferably 1 wt% to 10 wt%, and more preferably 1 wt% to 5 wt%, based on the total weight of the positive electrode active material layer. The above positive electrode can be manufactured according to a conventional positive electrode manufacturing method. For example, the positive electrode can be manufactured by mixing positive electrode material powder, a binder, and / or a conductive material in a solvent to manufacture a positive electrode slurry, applying the positive electrode slurry onto a positive electrode current collector, and then drying and rolling. The solvent may be a solvent generally used in the relevant technical field, such as dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, or water. One of these may be used alone or a mixture of two or more thereof may be used. The amount of the solvent used is sufficient to dissolve or disperse the cathode powder, 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 cathode. Alternatively, the positive electrode may be manufactured by casting the positive electrode slurry onto a separate support, then peeling the resulting film from the support and laminating it onto a positive electrode current collector. lithium secondary battery Next, a lithium secondary battery according to the present invention will be described. The lithium secondary battery specifically includes a positive electrode, a negative electrode including a negative electrode active material, and a separator and electrolyte interposed between the positive electrode and the negative electrode. Since the positive electrode is the same as described above, a detailed description will be omitted, and only the remaining components will be described in detail below. In addition, the lithium secondary battery may optionally further include a battery container that houses the electrode assembly of the positive electrode, the negative electrode, and the separator, and a sealing member that seals the battery container. In the above lithium secondary battery, the negative electrode includes a negative electrode current collector and a negative electrode active material layer positioned on the negative electrode current collector. 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. The above negative electrode active material layer optionally includes a binder and a conductive material together with the negative electrode active material. As the negative electrode active material, a compound capable of reversible intercalation and deintercalation of lithium may be used. Specific examples include carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber, and amorphous carbon; metallic compounds capable of alloying with lithium such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloy, Sn alloy, or Al alloy; SiO β (0 <β< 2), metal oxides capable of doping and dedoping lithium, such as SnO2, vanadium oxide, and lithium vanadium oxide; or composites containing the above metal 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 one embodiment of the present invention, the negative electrode active material may be graphite, the Si-containing material, or a mixture thereof, and specifically, may be graphite, and more specifically, a mixture of artificial graphite and natural graphite. In addition, a metallic lithium thin film may be used as the negative electrode active material. The negative electrode active material may be included in an amount of 80 wt% to 99 wt% based on the total weight of the negative electrode active material layer. The above binder is a component that assists in bonding between the conductive material, the active material, and the current collector, and is typically added in an amount of 0.1 wt% to 10 wt% based on the total weight of the negative electrode active material layer. Examples of such binders include polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene-butadiene rubber, nitrile-butadiene rubber, fluororubber, and various copolymers thereof. The conductive agent is a component for further improving the conductivity of the negative electrode active material, and may be added in an amount of 10 wt% or less, preferably 5 wt% or less, based on the total weight of the negative electrode active material layer. The conductive agent is not particularly limited as long as it has conductivity and does not cause a chemical change in the battery, and examples thereof include graphite such as natural graphite or artificial graphite; carbon black such as acetylene black, Ketjen black, channel black, furnace black, lamp black, and thermal black; conductive fibers such as carbon fiber or metal fiber; fluorinated carbon; metal powder such as aluminum or nickel powder; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives. The above negative electrode active material layer can be manufactured by applying and drying a negative electrode composite prepared by dissolving or dispersing a negative electrode active material, and optionally a binder and a conductive material in a solvent, on a negative electrode current collector, or by casting the negative electrode composite on a separate support and then laminating the obtained film by peeling it off from the support on a negative electrode current collector. Meanwhile, in the lithium secondary battery, the separator separates the negative electrode and the positive electrode and provides a passage for lithium ions to move. Any separator commonly used in lithium secondary batteries can be used without special restrictions, and in particular, one having low resistance to ion movement of the electrolyte and excellent electrolyte moisture retention capacity is preferable. Specifically, a porous polymer film, for example, a porous polymer film made of a polyolefin polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, and an ethylene / methacrylate copolymer, or a laminated structure of two or more layers thereof, can be used. In addition, a conventional porous nonwoven fabric, for example, a nonwoven fabric made of high-melting-point glass fiber, polyethylene terephthalate fiber, etc. can also be used. In addition, a coated separator containing a ceramic component or a polymer material to secure heat resistance or mechanical strength can be used, and can optionally be used in a single-layer or multi-layer structure. In addition, examples of the electrolyte used in the present invention include, but are not limited to, organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel-type polymer electrolytes, solid inorganic electrolytes, and molten inorganic electrolytes that can be used in the manufacture of lithium secondary batteries. Specifically, the electrolyte may include an organic solvent and a lithium salt. 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 (where R represents a linear, branched, or cyclic hydrocarbon group having 2 to 20 carbon atoms and may include a double-bonded aromatic ring or an ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; or sulfolanes 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. The above lithium salt can be used without any special limitation as long as it is a compound that can provide lithium ions used in a lithium secondary battery. Specifically, the anion of the lithium salt is F - , Cl - , Br - , I - , NO3 - , N(CN)2 - , BF4 - , CF3CF2SO3 - , (CF3SO2)2N - , (FSO2)2N - , CF3CF2(CF3)2CO - , (CF3SO2)2CH - , (SF5)3C - , (CF3SO2)3C - , CF3(CF2)7SO3 - , CF3CO2 - , CH3CO2 - , SCN - and (CF3CF2SO2)2N - It may be at least one selected from the group consisting of. Specifically, the lithium salt may be at least one selected from the group consisting of LiPF6, LiN(SO2F)2(LiFSI), LiClO4, LiAsF6, LiBF4, LiSbF6, LiAlO2, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2, LiCl, LiI and LiB(C2O4)2, and more specifically, it may be a mixture of LiPF6 and LiN(SO2F)2(LiFSI). The concentration of the lithium salt may be 0.1M to 4.0M, preferably 0.5M to 3.0M, and more preferably 1.0M to 2.0M. When the concentration of the lithium salt is within the above range, the electrolyte has appropriate conductivity and viscosity, so that it can exhibit excellent electrolyte performance and lithium ions can move effectively. When the lithium salt is a mixture of LiPF6 and LiN(SO2F)2(LiFSI), the molar ratio of LiPF6:LiFSI may be 5:5 to 9:1, preferably 6:4 to 8:2. In addition to the electrolyte components, the electrolyte may further include one or more additives, such as haloalkylene carbonate compounds such as difluoroethylene carbonate, pyridine, triethyl phosphite, triethanolamine, cyclic ethers, ethylene diamine, n-glyme, hexaphosphate triamide, nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinones, N,N-substituted imidazolidines, ethylene glycol dialkyl ethers, ammonium salts, pyrrole, 2-methoxyethanol, or aluminum trichloride, for the purpose of improving the life characteristics of the battery, suppressing battery capacity decrease, and improving the discharge capacity of the battery. At this time, the additives may be included in an amount of 0.1 to 5 wt% based on the total weight of the electrolyte. There is no particular limitation on the external shape of the lithium secondary battery of the present invention, but it may be a cylindrical shape using a can, a square shape, a pouch shape, or a coin shape. As described above, since a lithium secondary battery including a cathode material powder according to the present invention exhibits stable high-temperature performance, it can be used not only as a battery cell used as a power source for small devices such as mobile phones, laptop computers, and digital cameras, but can also be preferably used as a unit battery of a battery module for medium- to large-sized devices including a plurality of battery cells. Examples of the above medium and large devices include, but are not limited to, power tools, electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, and power storage systems. According to another embodiment of the present invention, a battery module including the lithium secondary battery as a unit cell and a battery pack including the same are provided. Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art can easily implement the present invention. [Example: Preparation of cathode material powder] Example 1. D 50 This is 5.0㎛ and Ni 0.93 Co 0.05 Mn 0.02 A precursor having a composition represented by (OH)2 and LiOH were placed in a Henschel mixer (700 L) and mixed at a central speed of 400 rpm for 20 minutes. At this time, LiOH was added in an amount such that the molar ratio of Li:(Ni+Co+Mn) was 1.05:1. The mixed powder was placed in an alumina crucible measuring 330 mm × 330 mm and first fired at a temperature of 800°C for 10 hours in an oxygen (O2) atmosphere. Afterwards, 2 mol% of Co(OH)2 relative to the total moles of the first fired body was added and second fired at a temperature of 700°C for 10 hours to form a Co coating layer. The fired powder was milled at a classification speed of 2,000 rpm in a dry air atmosphere using a jet-mill device, thereby forming Li[Ni 0.93 Co 0.05 Mn 0.02 ]O2 was prepared. The prepared cathode powder was observed using a scanning electron microscope at magnifications of 10.0k and 5.00k, and photographs are attached to Fig. 1. Example 2. D 50 This is 5.0㎛ and Ni 0.80 Co 0.10 Mn 0.10A precursor having a composition represented by (OH)2 and LiOH were placed in a Henschel mixer (700 L) and mixed at a central speed of 400 rpm for 20 minutes. At this time, LiOH was added in an amount such that the molar ratio of Li:(Ni+Co+Mn) was 1.05:1. The mixed powder was placed in an alumina crucible measuring 330 mm × 330 mm and first fired at a temperature of 800°C for 10 hours in an oxygen (O2) atmosphere. Afterwards, 2 mol% of Co(OH)2 was added relative to the total moles of the first fired body, and second firing was performed at a temperature of 700°C for 10 hours. The fired powder was milled at a classification speed of 2,000 rpm in a dry air atmosphere using a jet-mill device, thereby obtaining Li[Ni 0.80 Co 0.10 Mn 0.10 ]O2 was prepared. The prepared cathode powder was observed using a scanning electron microscope at magnifications of 10.0k and 5.00k, and photographs are attached to Fig. 2. Comparative Example 1. D as a precursor 50 A cathode material powder was prepared in the same manner as in Example 1, except that the 3.5 μm size was used. The photographs of the prepared cathode material powder observed at magnifications of 10.0 k and 5.00 k using a scanning electron microscope are attached to Fig. 3. Comparative Example 2. A cathode material powder was prepared in the same manner as in Example 1, except that the secondary firing was performed at 700°C for 8 hours. The photographs of the prepared cathode material powder observed using a scanning electron microscope at magnifications of 10.0k and 5.00k are attached in Fig. 4. Comparative Example 3. A cathode material powder was prepared in the same manner as in Example 1, except that the secondary firing was performed at 700°C for 15 hours. The photographs of the prepared cathode material powder observed using a scanning electron microscope at magnifications of 10.0k and 5.00k are attached in Fig. 5. Comparative Example 4. D 50 A cathode material powder was prepared in the same manner as in Example 1, except that a precursor of 4.3 μm was used. The photographs of the prepared cathode material powder observed at magnifications of 10.0 k and 5.00 k using a scanning electron microscope are attached to Fig. 7. [Experimental Example] Experimental Example 1. Powder Characteristics Evaluation (1) Measurement of particle size reduction rate particle size analysis After dispersing 0.1 g of each cathode material powder manufactured in the above examples and comparative examples in a dispersion medium, it was introduced into a laser diffraction particle size measuring device (Malvern, Mastersizer 3000) and irradiated with ultrasonic waves of about 28 kHz at an output of 60 W to measure the D of each cathode material powder. 50 , D min and D max was measured. The measurement results are shown in Table 1 below. Crystal strain and cation mixing ratio The XRD data obtained by performing X-ray diffraction analysis on each of the cathode material powders manufactured in the above examples and comparative examples were analyzed using the Rietveld refinement method to measure the degree of crystal deformation, and the cation mixing ratio was obtained using the excess value of Ni confirmed after Rietveld refinement, and the results are shown in Table 1 below. At this time, the X-ray diffraction analysis was performed using a Bruker D8 Endeavor (light source: Cu-Kα, λ=1.54Å) equipped with a LynxEye XE-T-position sensitive detector. The sample was placed in the groove of a general powder holder, the sample surface was leveled using a slide glass, and the sample was filled so that the height of the sample matched the edge of the holder. The analysis was performed under the conditions of FDS 0.5°, 2θ=15° to 90°, step size=0.02°, and total scan time=approximately 20 minutes. Rietveld refinement was performed on the measured data considering the charge at each site (metals at transition metal sites are +3, Ni at Li sites is +2) and cation mixing. Instrumental broadening was performed using the Fundamental Parameter Approach (FPA) implemented in the Bruker TOPAS program, and the entire peaks of the measurement range were used for fitting. The peak shape was fitted using only the Lorenzian contribution as the FP (First Principle) among the peak types available in TOPAS. D 50 Measurement of Each 3g of the cathode powders manufactured in the examples and comparative examples were placed in a circular mold with a diameter of 13mm, and a force equivalent to 9 tons was applied using an automatic pellet press (Auto Pellet Press, Carver, 3887.4) to manufacture pellets. After the manufactured pellets were dispersed again in a dispersion medium, they were introduced into a laser diffraction particle size measuring device (Malvern, Mastersizer 3000) and irradiated with ultrasonic waves of approximately 28kHz at an output of 60W to measure the D of each pressurized cathode powder. 50was measured. The measurement results are shown in Table 1 below. 50 ' It was written as . Calculating particle size reduction rate D of each cathode material measured as above 50 and D 50 ' The particle size reduction rate obtained by substituting the value into the above equation 1 is recorded as K in Table 1 below. (2) Pellet density and tap density Measurement of pellet density Each of 3 g of the cathode powders manufactured in the examples and comparative examples was placed into a circular mold with a diameter of 13 mm, and a force equivalent to 9 tons was applied using an automatic pellet press (Auto Pellet Press, Carver, 3887.4) to manufacture pellets. The height of the manufactured pellets was measured, and the volume of the pellets was calculated based on this. Then, the weight of the cathode powder was divided by the volume of the pellets to obtain the pellet density, which is shown in Table 1 below. Measurement of tap density The tap density of each cathode material powder manufactured in the above examples and comparative examples was measured using a GEOPYC 1360 tap density meter from Micromeritics. Specifically, 10 g of each cathode material powder manufactured in the above examples and comparative examples was filled into a container with a diameter of 19 mm, and the container was vibrated horizontally until a force of 108 N was applied to measure the tap density, which is shown in Table 1 below. D 50 [㎛]D min [㎛]D 10 [㎛]D 90 [㎛]D max [㎛]D 50 ' [㎛] Crystal strain [×10 -6]Cation mixing ratio [at%]K tab density of equation 1 [g / cc]Pellet density [g / cc]Example 15.150.6752.828.13511.23.942590.523.52.353.62Example 25.400.6753.0158.56511.23.892680.128.02.323.61Comparative example 13.960.4052.286.5458.682.902840.726.82.203.54Comparative example 26.040.5942.89510.414.55.023500.916.92.573.68Comparative example 35.420.6753.028.76511.23.773010.930.42.223.57Comparative example 44.690.5232.897.118.683.22741.131.82.383.66 Experimental Example 2. Monocell Performance Evaluation (1) Manufacturing of monocells Each of the cathode material powders manufactured in the above examples and comparative examples, carbon black as a conductive material, and PVDF as a binder were mixed in an NMP solvent at a weight ratio of 96.5:1.5:2.0 to manufacture a cathode slurry. The manufactured cathode slurry was applied to one surface of an aluminum current collector, dried at 130°C, and then rolled to manufacture a cathode. Meanwhile, graphite as an anode active material, carbon black as a conductive material, and styrene-butadiene rubber (SBR) as a binder were added to distilled water at a weight ratio of 95.0:3.5:1.5 to prepare a cathode slurry. The prepared cathode slurry was applied to one surface of a copper current collector, dried at 130°C, and then rolled to prepare a cathode. An electrode assembly was manufactured by interposing a porous polyethylene separator between the manufactured positive and negative electrodes, and then positioning it inside a battery case, and then injecting an electrolyte into the case to manufacture a mono cell. The electrolyte was manufactured by dissolving 0.7 M LiPF6 and 0.3 M LiFSI in a mixed organic solvent containing ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a volume ratio of 3:7. (2) Cycle characteristic evaluation Each mono cell manufactured in the above (1) was charged to 4.2 V with a constant current of 0.3 C, charged with a constant voltage of 0.05 C, and then discharged to 2.5 V with 0.3 C, and the capacity retention rate and resistance increase rate were measured while operating for a total of 600 cycles, which constituted one cycle. Specifically, the discharge capacity and resistance were measured at the 1st, 100th, 300th, and 600th cycles, and the discharge capacity retention rate and resistance increase rate at the 100th, 300th, and 600th cycles compared to the 1st cycle were calculated, and the results are shown in Table 2 below. The measuring device used was CRC (cell cycler) 05-10 (WONIK PNE Co., LTD). (3) Gas generation evaluation For each mono cell manufactured in (1) above, an activation (formation) process was performed, and then the cell was charged at a constant current (CC) of 0.3 C (reference capacity 1 C = 40 mAh / g) at 25°C until the voltage reached 4.20 V, and then charged at a constant voltage (CV) until the charge current reached 0.05 C (cut-off current). Afterwards, the cell was stored in a chamber at 60°C, and the mono cell was taken out of the chamber at weekly intervals and the volume change was calculated using a hydrometer (MATSUHAKU, TWD-150DM) by applying the Archimedes principle. The results are shown in Fig. 6, and the average volume change per week was calculated based on the results measured for 8 weeks and shown in Table 2 below. Cycle characteristics Gas generation [㎕ / week] Capacity maintenance rate (%) Resistance increase rate (%) 100cyc 300cyc 600cyc 100cyc 300cyc 600cyc Example 193.3 286.80 77.18 15.5 440.35 101.46 46.2 Example 293.4 386.5 776.5 214.78 34.2 191.94 5 4.6 Comparative example 193.4 986.20 72.48 8.66 26.46 118.31 575.2 Comparative example 293.0 185.78 74.65 25.20 58.43 182.99 5 7.4 Comparative example 392.5584.3268.0019.7845.93149.5360.7Comparative example 491.9283.5769.2625.4270.57287.0674.3 Through the results in Table 2 and Figure 6 above, D 50 This is 5.0㎛ or more and the crystal strain is 280×10 -6 It can be confirmed that the cells using the cathode materials of Examples 1 and 2 below show superior results in terms of capacity retention rate, resistance increase rate, and gas generation amount compared to the cells using the cathode materials of Comparative Examples 1 to 4. Through comparative examples 1 to 3, the crystal change rate is 280×10 -6 When the value exceeds , it can be confirmed that the life and resistance characteristics are deteriorated and at the same time, the amount of gas generated increases during high-temperature storage. In particular, in the case of Comparative Examples 2 and 3 where the particle size reduction rate exceeds 20-30%, it can be confirmed that the life and resistance characteristics are further deteriorated compared to Comparative Example 1. Meanwhile, D 50 In the case of Comparative Example 1, which is less than 5.0㎛, the crystal deformation is lower than in Comparative Examples 2 and 3, and the particle size reduction rate is within the range of 20 to 30%, so the capacity retention rate is similar to that of the example, but the resistance increase rate is more pronounced as the number of cycles increases, and it can be confirmed that the amount of gas generated increases significantly. Also, D 50 In the case of Comparative Example 4, which is less than 5.0㎛, the crystal strain is 280×10 -6Even below, it can be seen that the life and resistance characteristics are lowered compared to the example, and the amount of gas generated also increases significantly.

Claims

1. Contains a single particle lithium nickel oxide having a nickel content of 80 mol% or more among metals other than lithium, D 50 This is 5.0㎛ or more, The crystal strain is 280×10 -6 Below, positive electrode powder.

2. In claim 1, A cathode material powder having a cation mixing ratio of the cathode material powder of 1.0 at% or less.

3. In claim 1, A cathode material powder having a particle size reduction rate (K) of 20% to 30% according to the following formula 1: [Formula 1] In the above equation 1, D 50 D of the above cathode material powder 50 And, D 50 ’ The above cathode material powder was placed in a circular mold with a diameter of 13 mm and pressed with a force of 9 tons, and then measured. 50 am.

4. In claim 1, D of the above cathode powder min This positive electrode powder is 0.5㎛ or larger.

5. In claim 1, D of the above cathode powder max A cathode material powder having a size of 10㎛ to 20㎛.

6. In claim 1, The pellet density of the above cathode material powder is 3.50 g / cc or more, The above pellet density is a value obtained by dividing the weight of the positive electrode powder by the volume of the pellet after putting the positive electrode powder into a circular mold with a diameter of 13 mm and pressing it with a force of 9 tons to manufacture a pellet.

7. In claim 1, A cathode material powder having a tap density of 2.00 g / cc to 2.50 g / cc.

8. In claim 1, The above lithium nickel-based oxide is a cathode material powder having a composition of the following chemical formula 1: [Chemical Formula 1] Li 1+x (Ni a Co b M 1 c M 2 d )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, Mo, W, Cu, Fe, V, Cr, Zn, In, Y, La, Sr, Ga, Sc, Gd, Sm, Ce and B, x, a, b, c and d are 0≤x≤0.50, 0.80≤a<1, 0 respectively <b≤0.20, 0≤c≤0.20, 0≤d≤0.10, a+b+c+d=1을 만족한다.

9. In claim 1, The above lithium nickel-based oxide is a cathode material powder having a nickel content of 85 mol% or more among metals other than lithium.

10. In claim 1, A cathode material powder comprising a coating layer containing a Co element on the surface of the lithium nickel-based oxide particles.

11. A step of preparing a mixture by mixing a precursor having a nickel content of 80 mol% or more with a lithium raw material; A step of first calcining the above mixture at 750°C to 890°C; and A method for manufacturing a cathode material powder according to claim 1, comprising a step of secondarily firing the first fired sintered body at 660°C to 750°C for 9 to 14 hours.

12. In claim 11, A method for manufacturing a cathode material powder, further comprising a step of milling the secondarily fired sintered body at a speed of 1,000 rpm to 2,500 rpm.

13. In claim 11, A method for manufacturing a cathode material powder, which does not include a washing step after the above-mentioned secondary firing.

14. A cathode comprising the cathode material powder of claim 1.

15. A lithium secondary battery comprising: a positive electrode according to claim 14; a negative electrode including a negative electrode active material; a separator interposed between the positive electrode and the negative electrode; and an electrolyte.

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