Cathode material powder, method for manufacturing the same, lithium secondary battery containing the same

Abstract

The present invention provides a positive electrode material powder, which comprises lithium nickel-based oxide particles represented by the following Chemical Formula 1, and has a single crystallinity represented by formula (1) according to the present invention of 1.85 to 3.00. [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 selected from the group consisting of Ti, Mg, Al, Zr, Y, Ba, Ca, Sr, W, Ta, Nb and Mo, 0.80≦a≦1.20, 0.80≦b<1, 0

Description

[Technical Field]

[0001] This application claims priority under Korean Patent Application No. 10-2023-0124865 dated September 19, 2023, the entirety of which is incorporated herein by reference.

[0002] This invention relates to a positive electrode material powder, a method for producing the same, and a lithium secondary battery containing the same. More specifically, it relates to a positive electrode material powder capable of improving high-temperature characteristics, a method for producing the same, and a lithium secondary battery containing the same. [Background technology]

[0003] A lithium secondary battery generally consists of a positive electrode, a negative electrode, a separator membrane, and an electrolyte, and the positive electrode and negative electrode contain an active material that allows for the insertion and deintercalation of lithium ions.

[0004] Lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), lithium manganese oxide (LiMnO2, 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 advantage of a high operating voltage and excellent capacity characteristics, but the high price and unstable supply of cobalt, the raw material, make it difficult to commercially apply to high-capacity batteries. Lithium nickel oxide has poor structural stability, making it difficult to achieve sufficient lifespan characteristics. On the other hand, lithium manganese oxide has excellent stability but poor capacity characteristics. Therefore, lithium composite transition metal oxides containing two or more transition metals have been developed to complement the problems of lithium transition metal oxides containing Ni, Co, or Mn alone, and 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 oxide generally has a spherical secondary particle morphology formed by agglomeration of several tens to hundreds of primary particles. However, when a lithium nickel cobalt manganese oxide in such a secondary particle morphology with many agglomerated primary particles is applied, particle breakage involving detachment of primary particles is prone to occur during the rolling step in the production of the positive electrode, which causes the problem of cracks generating inside the particles during charge and discharge processes. When particle breakage or cracks occur in the positive electrode active material, the contact area with the electrolyte increases, so gas generation and degradation of the active material due to side reactions with the electrolyte increase, resulting in the problem of poor lifespan characteristics.

[0006] On the other hand, in recent years, there has been an increasing demand for high-output, high-capacity batteries such as those for electric vehicles, which leads to a tendency to increase electrode density for producing high-capacity batteries. However, when the electrode density is increased, although capacity characteristics are improved, the generation of fine powder due to particle breakage increases during rolling of the electrode, which increases the reaction area with the electrolyte, thus causing the disadvantage that the electrolyte is decomposed during charge and discharge and the surface structure of the active material deteriorates.

[0007] In order to solve the above problems, a technique has been proposed to produce a positive electrode active material in the form of single particles instead of secondary particles by increasing the firing temperature during the production of lithium nickel cobalt manganese oxide. In the case of a positive electrode active material in single-particle morphology, the contact area with the electrolyte is smaller than that of a conventional positive electrode active material in secondary-particle morphology, so side reactions with the electrolyte are less. Therefore, when a single-particle morphology positive electrode active material is applied, there are advantages that less gas is generated and the lifespan characteristics are excellent.

[0008] However, conventional single-particle morphology positive electrode active materials have the problems that a large amount of gas is generated at high temperatures, or the lifespan characteristics are low. Summary of the Invention Problem to be Solved by the Invention

[0009] The present invention is devised to solve the problems described above, and provides a positive electrode material powder that generates less gas at high temperatures and has excellent life characteristics, a method for producing the same, and a lithium secondary battery including the same. [Means for Solving the Problem]

[0010] [1] The present invention provides a positive electrode material powder comprising lithium nickel-based oxide particles represented by the following Chemical Formula 1, wherein the degree of single crystallization represented by the following Formula (1) (Mathematical Formula 1) is 1.85 to 3.00.

[0011] [Chemical Formula 1] Li a Ni b Co c M 1 d M' 2 e O₂

[0012] In Chemical Formula 1 above, M 1 is Mn, Al or a combination thereof, and M' 2 may be one or more selected from the group consisting of Ti, Mg, Al, Zr, Y, Ba, Ca, Sr, W, Ta, Nb and Mo, and 0.80≦a≦1.20, 0.80≦b<1, 0<c<0.45, 0<d<0.45, 0≦e≦0.20.

[0013] [Mathematical Formula] In Formula (1) above, Aₖ k is the area of the k-th grain measured when a cross-section of an electrode manufactured using the positive electrode material powder is subjected to ion milling treatment and then analyzed by Electron BackScatter Diffraction (EBSD), and n is the total number of grains measured by the Electron BackScatter Diffraction (EBSD) analysis, and is 200 to 500.

[0014] [2] In the present invention, in [1] above, the chemical formula 1 may be represented by the following chemical formula 1-1.

[0015] [Chemical formula 1-1] Li a1 Ni b1 Co c1 Mn d1 Al d2 M 2 e1 O2

[0016] In the above chemical formula 1-1, M 2 a1 may be one or more elements selected from the group consisting of Ti, Mg, Al, Zr, Y, Ba, Ca, Sr, W, Ta, Nb, and Mo, with 0.80≦a1≦1.20, 0.85≦b1<1, 0 <c1<0.45、0<d1<0.18、0<d2<0.15、0≦e1≦0.20、0<d1+d2<0.33であってもよい。

[0017] [3] In the present invention, in the above [1] or [2], the specific surface area of ​​the positive electrode material powder is 0.40 m². 2 / g~0.75m 2 / g is also acceptable.

[0018] [4] In at least one of the above [1] to [3], the rolling density of the positive electrode material powder may be 2.9 g / cc to 3.2 g / cc.

[0019] [5] In at least one of the above [1] to [4], the positive electrode material powder may have a generation rate of fine particles of 1 μm or less of 6 volume% or less when pressurized at 9 tons.

[0020] [6] In at least one of the above [1] to [5], the present invention relates to the average particle size (D) of the positive electrode material powder. 50 The diameter may be 2 μm to 5 μm.

[0021] [7] In at least one of the above [1] to [6], the positive electrode material powder may have a single crystallinity degree represented by formula (1) of 2.0 to 2.5.

[0022] [8] The present invention provides a method for producing cathode material powder according to at least one of the above [1] to [7], comprising the steps of (S1) primary calcination after mixing a cathode active material precursor and a lithium source, and (S2) secondary calcination of the primary calcined product, wherein the primary calcination step is carried out at 850°C to 960°C for 10 to 20 hours, and the secondary calcination step sequentially includes a first maintenance section maintained at 720°C to 850°C, a second maintenance section maintained at 900°C to 970°C, and a third maintenance section maintained at 720°C to 850°C, and the cathode active material precursor has a nickel content of 80 mol% or more in all metals excluding lithium.

[0023] [9] In the present invention, in the above [8], the primary firing step may be carried out at 870°C to 960°C for 10 to 15 hours.

[0024]

[10] In the present invention, in the above [8] or [9], the first maintenance interval and the third maintenance interval may each be maintained independently for 5 to 10 hours.

[0025]

[11] In at least one of the above [8] to

[10] , the second maintenance interval may be maintained for 5 to 60 minutes.

[0026]

[12] In at least one of the above [8] to

[11] , the total firing time for the secondary firing step may be 10 to 15 hours.

[0027]

[13] The present invention provides a lithium secondary battery comprising a positive electrode containing at least one positive electrode material powder from [1] to [7] above, a negative electrode, a separation membrane, and an electrolyte. [Effects of the Invention]

[0028] The positive electrode material powder according to the present invention is characterized in that the degree of single crystallinity represented by formula (1) is in the range of 1.85 to 3.00. In the case of lithium secondary batteries using positive electrode material powder with a degree of single crystallinity represented by formula (1) of less than 1.85 or greater than 3.00, a large amount of gas is generated during high-temperature storage, and the high-temperature life characteristics deteriorate.

[0029] In contrast, lithium secondary batteries using cathode material powder whose single-crystallinity degree satisfies the range of the present invention exhibit excellent high-temperature life characteristics and high-temperature storage characteristics. [Brief explanation of the drawing]

[0030] [Figure 1] This is an SEM image of a cross-section of an electrode manufactured using the positive electrode material powder produced according to Example 1 of the present invention. [Figure 2] This is an SEM image of a cross-section of an electrode manufactured using the positive electrode material powder produced according to Example 2 of the present invention. [Figure 3] This is an SEM image of a cross-section of an electrode manufactured using the positive electrode material powder produced according to Comparative Example 2 of the present invention. [Figure 4] This image shows an SEM image of a cross-section of an electrode manufactured using the cathode material powder produced according to Example 1 of the present invention, with EBSD analysis performed on the image. [Figure 5] This image shows an SEM image of a cross-section of an electrode manufactured using the cathode material powder produced according to Example 2 of the present invention, with EBSD analysis performed on the image. [Figure 6] This image shows an SEM image of a cross-section of an electrode manufactured using the cathode material powder produced according to Comparative Example 2 of the present invention, with EBSD analysis performed on the image. [Modes for carrying out the invention]

[0031] The present invention will be described in more detail below.

[0032] The terms and words used in this specification and in the claims are not to be interpreted in a manner limited to their ordinary or dictionary meanings, but rather in a manner consistent with the technical concept of the present invention, in accordance with the principle that inventors may appropriately define the concepts of terms in order to best describe their invention.

[0033] In this invention, "grain" is a unit of particles having the same crystal orientation, and is the smallest unit of particles that can be recognized as a single nodule in an electron backscatter diffraction (EBSD) map image. The size of a grain can be measured by image analysis of the EBSD map.

[0034] In this invention, "single particle" means a particle consisting of one nodule, and "pseudo-single particle" means a composite particle consisting of 30 or fewer nodules.

[0035] The aforementioned "nodule" is a lower particle unit that constitutes a single particle or a pseudo-single particle, and may be a single crystal without crystalline grain boundaries, or a polycrystal in which grain boundaries do not appear to exist when observed with a scanning electron microscope at a field of view of 5,000 to 20,000 times.

[0036] In this invention, "secondary particle" means a particle formed by the aggregation of multiple primary particles, for example, tens to hundreds of primary particles. Specifically, a secondary particle may be an aggregate of 50 or more primary particles.

[0037] In the present invention, "particle" is a concept that includes one or all of the following: a single particle, a pseudo-single particle, a primary particle, a nodule, and a secondary particle.

[0038] In this invention, the "specific surface area" is measured by the BET method, and specifically can be calculated from the amount of nitrogen gas adsorbed at liquid nitrogen temperature (77K) using BELSORP-mini II from BEL Japan.

[0039] In this invention, "average particle size (D 50 "50% of the volume cumulative particle size distribution of the cathode material powder" refers to the particle size at 50% of the volume cumulative particle size distribution and can be measured using the laser diffraction method. For example, the cathode material powder is dispersed in a dispersion medium, then introduced into a commercially available laser diffraction particle size analyzer (e.g., Microtrac MT 3000), and irradiated with ultrasound at approximately 28 kHz at an output of 60 W. After obtaining a volume cumulative particle size distribution graph, the particle size corresponding to 50% of the volume cumulative amount is then determined.

[0040] The inventors of this invention conducted extensive research to develop a cathode material with excellent high-temperature characteristics. As a result, they discovered that excellent high-temperature characteristics can be achieved when the ratio of the sum of the squares of the grain areas to the sum of the grain areas in the cathode material powder satisfies a specific relationship, leading to the completion of this invention.

[0041] The present invention will be described in detail below.

[0042] The cathode material powder, method for producing the same, and lithium secondary battery containing the same according to the present invention include at least one of the configurations disclosed below, and may include any combination of technically feasible configurations from the following.

[0043] Cathode material powder The cathode material powder according to the present invention will be described below.

[0044] The cathode material powder according to the present invention has a single crystallinity degree of 1.85 to 3.00, which is represented by the following formula (1)(Equation 2).

[0045]

number

[0046] In the above equation (1), A kThis is the area of ​​the k-th grain measured when the cross-section of an electrode obtained by ion milling an electrode manufactured using the aforementioned positive electrode material powder is analyzed by electron backscatter diffraction (EBSD), and is in μm. 2 The value is measured in units. Specifically, A k The value can be obtained by the software of the EBSD device. k 2 A, obtained by the method described above, k It is the square of the area of ​​the k-th grain.

[0047] On the other hand, A, which is substituted into equation (1) above... k and A k 2 It is a dimensionless number that does not contain units.

[0048] The aforementioned n is the total number of grains measured by the electron backscatter diffraction (EBSD) analysis, which may be 200 to 500, preferably 250 to 450, and more preferably 300 to 400. If the total number of measured grains is too small, it cannot represent the grain size trend in the entire cathode material powder, and if it is too large, the accuracy of the measurement will be low.

[0049] Backscatter electron diffraction (EBSD) analysis is a method of analyzing the crystallographic information of a sample by measuring its crystallographic phase and crystallographic orientation using the diffraction pattern of the sample. When a sample is tilted at a large angle with respect to the direction of incidence of the electron beam using a scanning electron microscope, the incident electron beam is scattered within the sample, causing a diffraction pattern to appear on the surface of the sample. This is called the backscattered electron diffraction pattern (EBSP). Since the backscattered electron diffraction pattern responds to the crystal orientation of the region irradiated by the electron beam, it can be used to accurately measure the crystal orientation of the sample and obtain an EBSD IPF map (inverse pole figure map) which shows the sample partitioned by grains having the same crystal orientation. Furthermore, by using EBSD software to image analyze the IPF map, information such as grain size, pattern, and orientation can be obtained.

[0050] In this invention, for EBSD analysis of positive electrode material powder, an EBSD analysis electrode is manufactured using the positive electrode material powder to be analyzed, the manufactured electrode is cut by ion milling, and then an electron beam is irradiated onto the cut surface of the electrode to perform EBSD analysis. Specifically, the EBSD measurement electrode can be manufactured by mixing the positive electrode material powder to be analyzed with a conductive material and a binder in N-methylpyrrolidone to produce an electrode slurry, coating the electrode slurry onto an aluminum current collector, and then drying it. On the other hand, the rolling process is not performed when manufacturing the EBSD analysis electrode. This is because deformation and fracture may occur in the positive electrode active material particles if the rolling process is performed.

[0051] Figures 4 to 6 show IPF map images obtained by cutting electrodes manufactured using the cathode material powders of Examples 1 and 2 and Comparative Example 2, described later, by ion milling, and then performing EBSD analysis on the cross-sections. As shown in Figures 4 to 6, EBSD analysis can be used to obtain images partitioned by grain units.

[0052] According to the inventors' research, when the degree of single crystallinity represented by formula (1) above satisfies a specific range, it is possible to obtain the effect of simultaneously improving high-temperature storage and high-temperature lifetime characteristics.

[0053] The degree of single crystallinity represented by formula (1) above is between 1.85 and 3.00. Preferably, the degree of single crystallinity represented by formula (1) above is between 1.9 and 2.8, and more preferably between 2.0 and 2.5. Formula (1) above is obtained by dividing the sum of the squares of the grain areas shown during EBSD analysis by the sum of the grain areas. If formula (1) above is less than 1.85, the reaction area of ​​the cathode material powder that reacts with the electrolyte increases, accelerating the decomposition of the electrolyte and deterioration of the surface structure, which leads to problems such as a decrease in high-temperature storage characteristics and lifespan characteristics. If formula (1) above exceeds 3.00, the distance lithium ions travel to diffuse into the inside of the particles increases, resulting in inferior lithium mobility, which causes an imbalance of lithium ions between the inside and outside of the particles during charging / discharging, which leads to problems such as a decrease in high-temperature storage characteristics and lifespan characteristics.Therefore, it was found that when a lithium secondary battery is manufactured using cathode material powder that satisfies the above range, both high-temperature storage characteristics and high-temperature lifespan characteristics are excellent.

[0054] The degree of single crystallinity represented by formula (1) above can be controlled by various methods, but it is preferable to control it by the number of moles of nickel contained in the lithium nickel oxide particles, the type of raw materials used in the production of the cathode material powder, the mixing ratio, the firing step, the firing temperature, the firing time, and the firing atmosphere.

[0055] On the other hand, the cathode material powder according to the present invention contains lithium nickel-based oxide particles represented by the following [Chemical Formula 1].

[0056] [Chemical formula 1] Li a Ni b Co c M 1 d M 2 e O2

[0057] In the above [Chemical Formula 1], M 1 This is Mn, Al, or a combination thereof, preferably Mn or a combination of Mn and Al, and more preferably a combination of Mn and Al.

[0058] Said M 2 It is one or more selected from the group consisting of Ti, Mg, Al, Zr, Y, Ba, Ca, Sr, W, Ta, Nb, and Mo, preferably one or more selected from the group consisting of Ti, Mg, Al, Zr, Y, Sr, W, and Nb, and more preferably one or more selected from the group consisting of Ti, Mg, Al, Zr, and Y. 2 Elements are not essential, but when present in appropriate amounts, they play a role in promoting particle growth or improving the stability of the crystal structure during firing.

[0059] The above 'a' represents the molar ratio of lithium in the lithium nickel oxide particles, 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.

[0060] The aforementioned b represents the molar ratio of nickel in the total metal excluding lithium in the lithium-nickel oxide particles, and may be 0.80 ≤ b < 1, 0.82 ≤ b < 1, or 0.85 ≤ b < 1. When the molar ratio of nickel satisfies the above range, excellent capacity characteristics are achieved, and in particular, when the molar ratio of nickel is 0.80 or higher, even better capacity characteristics can be achieved. However, when the molar ratio of nickel is less than 0.80, there was a problem in that it was difficult to achieve the degree of single crystallinity represented by the above formula (1).

[0061] Wherein c represents the molar ratio of cobalt among all metals excluding lithium in the lithium nickel-based oxide particles, and may satisfy 0 < c < 0.45, 0 < c < 0.40, 0 < c < 0.20, or 0 < c < 0.18.

[0062] Wherein d represents the molar ratio of M 1 element among all metals excluding lithium in the lithium nickel-based oxide particles, and may satisfy 0 < d < 0.45, 0 < d < 0.40, 0 < d < 0.33, 0 < d < 0.25, 0 < d < 0.20, or 0 < d < 0.18.

[0063] Wherein e represents the molar ratio of M 2 element among all metals excluding lithium in the lithium nickel-based oxide particles, and may satisfy 0 ≤ e ≤ 0.20, 0 ≤ e ≤ 0.15, or 0 ≤ e ≤ 0.10.

[0064] It is more preferable that [Chemical Formula 1] is represented by the following [Chemical Formula 1-1].

[0065] [Chemical Formula 1-1] Li a1 Ni b1 Co c1 Mn d1 Al d2 M 2 e1 O2

[0066] In the above Chemical Formula 1-1, M 2is at least one element selected from the group consisting of Ti, Mg, Al, Zr, Y, Ba, Ca, Sr, W, Ta, Nb and Mo, and may satisfy 0.80≦a1≦1.20, 0.80≦b1<1, 0<c1<0.18, 0<d1<0.18, 0<d2<0.15, 0≦e1≦0.20, 0<d1+d2<0.33; preferably satisfies 0.80≦a1≦1.20, 0.82≦b1<1, 0<c1<0.15, 0<d1<0.15, 0<d2<0.10, 0≦e1≦0.10, 0<d1+d2<0.25; and more preferably satisfies 0.80≦a1≦1.20, 0.85≦b1<1, 0<c1<0.15, 0<d1<0.15, 0<d2<0.10, 0≦e1≦0.10, 0<d1+d2<0.25. When the lithium nickel-based oxide particles have the composition of the above [Chemical Formula 1-1], the positive electrode active material is excellent in structural stability and capacity characteristics.

[0067] On the other hand, the positive electrode material powder may further include a coating layer formed on a surface of the lithium nickel-based oxide particles, the coating layer containing at least one coating element 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.

[0068] When a coating layer is present on the surface of the lithium nickel-based oxide particles, the coating layer suppresses contact between the electrolyte and the lithium nickel-based oxide particles, whereby the effect of reducing elution of transition metals and generation of gas caused by side reactions with the electrolyte can be obtained.

[0069] On the other hand, the lithium nickel oxide particles of the present invention described above may be single particles consisting of one nodule and / or pseudo-single particles which are composites of 30 or fewer nodules, preferably 2 to 20, more preferably 2 to 10, or may be in a form containing such. The positive electrode material powder according to the present invention preferably consists of a combination of single-particle and pseudo-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 fracture increases during electrode manufacturing, and the occurrence of internal cracks due to the expansion / contraction of the volume of nodules during charging and discharging increases, which can reduce the improvement effect on high-temperature lifetime characteristics and high-temperature storage characteristics.

[0070] On the other hand, the specific surface area of ​​the positive electrode material powder is 0.40 m². 2 / g~0.75m 2 It may also be / g, 0.45m 2 / g~0.70m 2 It is preferable that it be / g, and 0.50m 2 / g~0.70m 2 It is more preferable that the value is / g. When the BET specific surface area range is met, side reactions with the electrolyte can be appropriately reduced, gas generation can be decreased, and the high-temperature life performance of the battery can be improved.

[0071] On the other hand, the rolling density of the positive electrode material powder may be 2.9 g / cc to 3.2 g / cc, and preferably 2.95 g / cc to 3.1 g / cc. When the rolling density of the positive electrode material powder is satisfied, excellent energy density can be ensured, particle breakage that occurs during electrode rolling can be prevented, side reactions with the electrolyte can be appropriately reduced, and the battery life and stability characteristics can be improved.

[0072] On the other hand, when the positive electrode material powder is pressurized at 9 tons, the generation rate of fine particles smaller than 1 μm may be 6 volume% or less, preferably 5 volume% or less, and more preferably 3 volume% or less. Since the side reactions on the surface of the positive electrode active material are mainly caused by the generation of fine particles of the positive electrode active material, if a large amount of fine particles smaller than 1 μm are generated, the side reactions with the electrolyte become more vigorous, which can lead to a decrease in the lifetime characteristics and storage characteristics at high temperatures.

[0073] On the other hand, the average particle size (D) of the positive electrode material powder 50 The average particle size (D) of the positive electrode material powder may be 2 μm to 5 μm, preferably 2.5 μm to 4.5 μm, more preferably 3 μm to 4 μm, and even more preferably 3.3 μm to 3.7 μm. 50 ) is the particle size when the volume cumulative amount shown in the volume cumulative particle size distribution of the cathode material powder measured using the laser diffraction method is 50%. Here, the average particle size (D) of the cathode material powder is 50 If the above conditions are met, the battery has excellent initial capacity and output characteristics.

[0074] Method for manufacturing positive electrode material powder Next, a method for producing positive electrode material powder according to the present invention will be described.

[0075] The method for producing positive electrode material powder according to the present invention includes (S1) a step of primary calcination after mixing a positive electrode active material precursor and a lithium source, and (S2) a step of secondary calcination of the primary calcined product, wherein the primary calcination step is carried out at 850°C to 960°C for 10 to 20 hours, and the secondary calcination step sequentially includes a first maintenance section maintained at 720°C to 850°C, a second maintenance section maintained at 900°C to 970°C, and a third maintenance section maintained at 720°C to 850°C, and the positive electrode active material precursor has a nickel content of 80 mol% or more in the total metals excluding lithium.

[0076] The cathode material powder according to the present invention described above can be manufactured by appropriately adjusting the type of raw material, mixing ratio, firing step, firing temperature, firing atmosphere, and so on.

[0077] The steps of the present invention will be described in detail below.

[0078] ((S1) Step) The process involves mixing a positive electrode active material precursor and a lithium source, followed by a primary calcination step, which is carried out at 850°C to 960°C for 10 to 20 hours.

[0079] The positive electrode active material precursor is a transition metal precursor having a nickel content of 80 mol% or more in the total metals excluding lithium. Preferably, the nickel content in the total metals excluding lithium is 82 mol% or more, and more preferably, it is 85 mol% or more. If the nickel content in the total metals excluding lithium in the positive electrode active material precursor is less than 80 mol%, a high amount of heat is required to ensure crystallinity due to a decrease in the nickel content or an increase in the content of other elements, and therefore, a high firing temperature is essential to increase the degree of single crystallinity. Thus, if the nickel content in the total metals excluding lithium in the positive electrode active material precursor is less than 80 mol%, it is difficult to control the degree of single crystallinity represented by the above formula (1) to the aforementioned range within the firing temperature range according to the present invention, and even if the positive electrode material powder is produced by performing the primary firing step and secondary firing step according to the present invention, there is a problem in that it is difficult to achieve excellent high-temperature storage characteristics and lifetime characteristics.

[0080] Furthermore, the positive electrode active material precursor may be purchased and used from commercially available nickel-cobalt-manganese hydroxides or nickel-cobalt-manganese-aluminum hydroxides, or it may be manufactured by a precursor manufacturing method known in the art, such as the coprecipitation method.

[0081] For example, a transition metal-containing solution containing nickel (Ni), cobalt (Co), and manganese (Mn) cations can be prepared, and then an ammonium cation-containing complex-forming agent and a basic aqueous solution can be added to the transition metal-containing solution to cause a coprecipitation reaction to produce a cathode active material precursor. If necessary, the transition metal-containing solution may further contain aluminum (Al) cations.

[0082] The transition metal-containing solution may contain nickel-containing raw materials, cobalt-containing raw materials, and manganese-containing raw materials, and may further contain aluminum-containing raw materials as needed.

[0083] The nickel-containing raw material may be, for example, nickel-containing acetates, nitrates, sulfates, halides, sulfides, hydroxides, oxides, oxyhydroxides, etc. Specifically, it may be, but is not limited to, Ni(OH)2, NiO, NiOOH, NiCO3·2Ni(OH)2·4H2O, NiC2O2·2H2O, Ni(NO3)2·6H2O, NiSO4, NiSO4·6H2O, fatty acid nickel salts, nickel halides, or combinations thereof.

[0084] The cobalt-containing raw material may be cobalt-containing acetates, nitrates, sulfates, halides, sulfides, hydroxides, oxides, oxyhydroxides, etc. Specifically, it may be, but is not limited to, Co(OH)2, CoOOH, Co(OCOCH3)2·4H2O, Co(NO3)2·6H2O, CoSO4, Co(SO4)2·7H2O, or combinations thereof.

[0085] The manganese-containing raw material may be, for example, a manganese-containing acetate, nitrate, sulfate, halide, sulfide, hydroxide, oxide, oxyhydroxide, or a combination thereof. Specifically, it may be, but is not limited to, manganese oxides such as Mn2O3, MnO2, Mn3O4; manganese salts such as MnCO3, Mn(NO3)2, MnSO4, manganese acetate, manganese dicarboxylate, manganese citrate, manganese fatty acid salt; manganese oxyhydroxide, manganese chloride, or a combination thereof.

[0086] The aluminum-containing raw material may be, but is not limited to, Al2O3, Al(OH)3, Al(NO3)3, Al2(SO4)3, (HO)2AlCH3CO2, HOAl(CH3CO2)2, Al(CH3CO2)3, aluminum halides, or combinations thereof.

[0087] The transition metal-containing solution may be produced by adding nickel-containing raw materials, cobalt-containing raw materials, manganese-containing raw materials, and aluminum-containing raw materials to a solvent, specifically water, or a mixed solvent of an organic solvent that can be homogeneously mixed with water (e.g., alcohol), or by mixing an aqueous solution of nickel-containing raw materials, an aqueous solution of cobalt-containing raw materials, and manganese-containing raw materials.

[0088] The ammonium cation-containing complex-forming agent may be, for example, NH4OH, (NH4)2SO4, NH4NO3, NH4Cl, CH3COONH4, NH4CO3, or a combination thereof, but is not limited thereto. On the other hand, the ammonium cation-containing complex-forming agent may also be used in aqueous solution form, in which case water or a mixture of water and an organic solvent that can be homogeneously mixed with water (specifically, an alcohol) may be used as the solvent.

[0089] The basic compound may be an alkali metal or alkaline earth metal hydroxide such as NaOH, KOH, or Ca(OH)2, their hydrates, or a combination thereof. The basic compound may also be used in aqueous solution form, in which case water or a mixture of water and an organic solvent that can be homogeneously mixed with water (specifically, an alcohol) may be used as the solvent.

[0090] Basic compounds are added to adjust the pH of the reaction solution, and may be added in an amount that brings the pH of the metal solution to 8-12.

[0091] The coprecipitation reaction may be carried out in an inert atmosphere such as nitrogen or argon, at a temperature range of 35°C to 80°C.

[0092] Through the process described above, positive electrode active material precursor particles of nickel-cobalt-manganese hydroxide or nickel-cobalt-manganese-aluminum hydroxide are generated and precipitate in the reaction solution. By adjusting the concentrations of the nickel-containing raw material, cobalt-containing raw material, manganese-containing raw material, and aluminum-containing raw material, a positive electrode active material precursor can be produced in which the nickel (Ni) content of the total metal content is 55 mol% or more. The positive electrode active material precursor can be produced by separating and drying the precipitated positive electrode active material precursor particles by conventional methods.

[0093] The lithium raw material may be a lithium-containing sulfate, nitrate, acetate, carbonate, oxalate, citrate, halide, hydroxide, oxyhydroxide, etc., and is not particularly limited as long as it is soluble in water. Specifically, the lithium raw material may be Li2CO3, LiNO3, LiNO2, LiOH, LiOH·H2O, LiH, LiF, LiCl, LiBr, LiI, CH3COOLi, Li2O, Li2SO4, CH3COOLi, Li3C6H5O7, etc., and one or more of these may be used as a mixture of two or more.

[0094] The mixing may consist of solid-phase mixing or liquid-phase mixing. If the components are mixed by solid-phase mixing, the calcination process can be carried out without performing a separate drying process. If the components are mixed by liquid-phase mixing, the calcination process is carried out after spray-drying the mixed components.

[0095] Furthermore, doping material may be added as needed.

[0096] As the doping raw material, oxides, hydroxides, sulfides, oxyhydroxides, halides, or mixtures thereof containing one or more elements selected from the group consisting of Ti, Mg, Al, Zr, Y, Ba, Ca, Sr, W, Ta, Nb, and Mo may be used.

[0097] The aforementioned primary firing step may be carried out under an air or oxygen atmosphere.

[0098] The primary firing step may be carried out at a temperature of 850°C to 960°C, preferably 860°C to 960°C, and more preferably 870°C to 960°C. By firing within the above temperature range, it is possible to produce a cathode material powder with improved crystallinity and structural stability, and to adjust the grain area measured in the cross-section of an electrode manufactured using the cathode material powder to an appropriate value to achieve an appropriate degree of single crystallinity.

[0099] Furthermore, the primary firing step may be carried out for 10 to 20 hours, preferably 10 to 18 hours, and more preferably 10 to 15 hours. If the firing time is less than 10 hours, the crystallinity will be inferior, the structural stability will decrease, particle growth will not occur sufficiently, and the degree of single crystallinity will be low. Also, if the firing time exceeds 20 hours, over-firing will occur, and the output characteristics of the battery will decrease.

[0100] ((S2) Step) The process includes a step of secondary firing of the primary fired product, the secondary firing step sequentially comprising a first maintenance interval of 720°C to 850°C, a second maintenance interval of 900°C to 970°C, and a third maintenance interval of 720°C to 850°C. The firing may be carried out in an air or oxygen atmosphere.

[0101] The secondary firing step includes a second maintenance section maintained at a higher temperature than the first and third maintenance sections, thereby allowing for appropriate control of the single crystallinity of the cathode material powder. Specifically, by including a second maintenance section in which heat treatment is performed for a short time at a higher temperature than the first and third maintenance sections, the single crystallinity of particles whose growth is uneven due to insufficient heat can be increased, and cathode material powder with an appropriate single crystallinity can be produced. However, if the first to third maintenance sections are included in the primary firing step instead of the secondary firing step, it may be difficult to obtain an appropriate single crystallinity.

[0102] The temperatures of the first and third maintenance sections may be independently 720°C to 850°C, preferably 730°C to 840°C, and more preferably 750°C to 830°C, or the temperatures of the first and third maintenance sections may be the same. When the above ranges are met, the stability of the surface structure is excellent, improving high-temperature life and high-temperature storage performance, and particle aggregation is reduced, improving the capacity characteristics, output characteristics, and high-temperature life characteristics of the battery.

[0103] The temperature in the second maintenance interval may be 900°C to 970°C, preferably 910°C to 960°C, and more preferably 920°C to 950°C. When the above range is met, particles can be grown with sufficient heat, improving the uneven particle growth caused by low heat, and thus improving the high-temperature life characteristics and high-temperature storage characteristics of the battery.

[0104] The first maintenance interval may be maintained for 5 to 10 hours, preferably 6 to 10 hours, and more preferably 7 to 9 hours. When the above range is met, the particles can be aggregated in an appropriate number, and a preferred range of single crystallinity can be met.

[0105] The second maintenance interval may be maintained for 5 to 60 minutes, preferably 10 to 50 minutes, and more preferably 10 to 40 minutes. When the above range is met, the growth of non-uniform particles can be improved, and an appropriate range for single crystallinity can be achieved.

[0106] The third maintenance interval may be maintained for 5 to 10 hours, preferably 6 to 10 hours, and more preferably 7 to 9 hours. When the above range is met, the particles can be aggregated in an appropriate number, and a preferred range of single crystallinity can be met.

[0107] The total firing time for the secondary firing step may be 10 to 15 hours, preferably 10 to 14 hours, and more preferably 10 to 13 hours. When the above range is met, the surface structure can be sufficiently stabilized, improving the durability of the surface structure, and the electrochemical properties of the battery can be improved because the particles do not aggregate excessively with each other.

[0108] If necessary, the fired product after the secondary firing step can be mixed with the coating raw material and heat-treated to form a coating layer.

[0109] The formation of the coating layer can be carried out using methods known in the art, such as wet coating, dry coating, plasma coating, and ALD (Atomic Layer Deposition).

[0110] The wet coating method can be carried out, for example, by adding the calcined product after the secondary calcination step and the coating raw material to a suitable solvent such as ethanol, water, methanol, or acetone, and then mixing until the solvent is gone.

[0111] The dry coating method described above is a method of mixing lithium composite transition metal oxide and coating raw material in a solid phase without a solvent, and can use methods such as grinder mixing or mechanofusion.

[0112] The coating raw material may be an oxide, hydroxide, oxyhydroxide, carbonate, sulfate, halide, sulfide, acetate, carboxylate, or combination thereof, containing one or more elements selected from the group consisting of Ti, Mg, Al, Zr, Y, Ba, Ca, Zr, Sr, W, Ta, Nb, and Mo.

[0113] positive electrode Next, the positive electrode according to the present invention will be described.

[0114] 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 components other than the positive electrode material powder will be described below.

[0115] In the positive electrode, the positive electrode current collector is not particularly limited as long as it does not cause chemical changes in the battery and is conductive. For example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel with surface treatment using carbon, nickel, titanium, silver, etc., can be used. The positive electrode current collector usually has a thickness of 3 to 500 μm, and fine irregularities can be formed on the surface of the positive electrode current collector to enhance the adhesion of the positive electrode active material. For example, it can be used in various forms such as film, sheet, foil, net, porous material, foam, nonwoven fabric, etc.

[0116] Furthermore, the positive electrode active material layer may also contain a conductive material and a binder, along with the positive electrode material powder mentioned above.

[0117] The conductive material is used to impart conductivity to the electrodes and can be used without particular limitations as long as it does not cause chemical changes in the battery and has electronic conductivity. Specific examples include graphite such as natural graphite and 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 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; and conductive polymers such as polyphenylene derivatives. One of these can be used alone or a mixture of two or more. The conductive material may typically be present in an amount of 1 to 30% by weight, preferably 1 to 20% by weight, and more preferably 1 to 10% by weight, relative to the total weight of the positive electrode active material layer.

[0118] The binder plays a role in improving adhesion between positive electrode active material particles and adhesion 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, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer rubber (EPDM rubber), sulfonated EPDM, styrene-butadiene rubber (SBR), fluororubber, or various copolymers thereof, and one or more of these can be used. The binder may be present in an amount of 1 to 30% by weight, preferably 1 to 20% by weight, and more preferably 1 to 10% by weight, relative to the total weight of the positive electrode active material layer.

[0119] The positive electrode can be manufactured by a conventional method for manufacturing a positive electrode. For example, the positive electrode can be manufactured by mixing a positive electrode material, a binder, and / or a conductive material in a solvent to produce a positive electrode slurry, applying the positive electrode slurry onto a positive electrode current collector, and then drying and rolling it.

[0120] The solvent may be any solvent commonly used in the art, such as dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, or water. One of these may be used alone or in mixtures of two or more. The amount of solvent used should be sufficient to dissolve or disperse the positive electrode active material, conductive material, and binder, taking into consideration the coating thickness and production yield of the slurry, and to provide a viscosity that allows for excellent thickness uniformity during subsequent coating for the production of the positive electrode.

[0121] Alternatively, the positive electrode can be manufactured by casting the positive electrode slurry onto another support, then peeling it off the support and laminating the resulting film onto the positive electrode current collector.

[0122] Lithium-ion rechargeable battery Next, the lithium secondary battery according to the present invention will be described.

[0123] The lithium secondary battery of the present invention includes a positive electrode according to the present invention, and more specifically, a positive electrode comprising a positive electrode material powder according to the present invention. Specifically, the lithium secondary battery may include the positive electrode, a negative electrode, a separator membrane, and an electrolyte, and more specifically, the lithium secondary battery includes a positive electrode, a negative electrode positioned opposite the positive electrode, and a separator membrane and an electrolyte interposed between the positive electrode and the negative electrode, wherein the positive electrode is as described above. The lithium secondary battery may also selectively further include a battery container housing the electrode assembly of the positive electrode, negative electrode, and separator membrane, and a sealing member for sealing the battery container.

[0124] (Negative electrode) In the lithium secondary battery described above, the negative electrode includes a negative electrode current collector and a negative electrode active material layer located on the negative electrode current collector.

[0125] The negative electrode current collector is not particularly limited as long as it does not cause chemical changes in the battery and has high conductivity. For example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., and aluminum-cadmium alloy can be used. The negative electrode current collector usually has a thickness of 3 to 500 μm, and, similar to the positive electrode current collector, fine irregularities can be formed on the surface of the current collector to strengthen the bonding force of the negative electrode active material. For example, it can be used in various forms such as film, sheet, foil, net, porous material, foam, and nonwoven fabric.

[0126] The negative electrode active material layer selectively includes a binder and a conductive material together with the negative electrode active material.

[0127] As the negative electrode active material, compounds capable of reversible intercalation and deintercalation of lithium can 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 alloys, Sn alloys, and Al alloys; and SiO2. β Examples include metal oxides that can be doped and dedoped with lithium, such as (0<β<2), SnO2, vanadium oxide, and lithium vanadium oxide; and composites containing the aforementioned metallic compound and carbonaceous material, such as Si-C composites or Sn-C composites. One or more mixtures of these can be used.

[0128] Furthermore, a metallic lithium thin film can also be used as the negative electrode active material. In addition, all types of carbon materials can be used, including low-crystalline carbon and high-crystalline carbon. Typical low-crystalline carbons include soft carbon and hard carbon, while typical high-crystalline carbons include amorphous, plate-like, flaky, spherical, or fibrous natural or artificial graphite, Kish graphite, pyrolytic carbon, mesophase pitch-based carbon fiber, meso-carbon microbeads, mesophase pitches, and high-temperature calcined carbon such as petroleum or coal tar pitch-derived cokes.

[0129] The conductive material is used to impart conductivity to the electrodes and can be used without particular limitations as long as it does not cause chemical changes in the battery and has electronic conductivity. Specific examples include graphite such as natural graphite and 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 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; and conductive polymers such as polyphenylene derivatives. One of these can be used alone or a mixture of two or more. The conductive material may typically be present in an amount of 1 to 30% by weight, preferably 1 to 20% by weight, and more preferably 1 to 10% by weight, relative to the total weight of the negative electrode active material layer.

[0130] The binder plays a role in improving adhesion between negative electrode active material particles and adhesion 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, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer rubber (EPDM rubber), sulfonated EPDM, styrene-butadiene rubber (SBR), fluororubber, or various copolymers thereof, and one or more of these can be used. The binder may be present in an amount of 1 to 30% by weight, preferably 1 to 20% by weight, and more preferably 1 to 10% by weight, based on the total weight of the negative electrode active material layer.

[0131] The negative electrode active material layer can be manufactured, for example, by applying a negative electrode slurry containing a negative electrode active material, as well as selectively a binder and a conductive material, onto a negative electrode current collector and drying it, or by casting the negative electrode slurry onto another support, then peeling it off the support and laminating the resulting film onto the negative electrode current collector.

[0132] (separation membrane) On the other hand, in the lithium secondary battery, the separation membrane separates the negative electrode and the positive electrode and provides a passage for lithium ions to move. It can be used without particular limitations as long as it is a membrane that is normally used as a separation membrane in lithium secondary batteries, and it is especially preferable that it has low resistance to ion movement of the electrolyte and excellent electrolyte moisture absorption capacity. Specifically, porous polymer films, such as porous polymer films made from polyolefin polymers such as ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer, and ethylene / methacrylate copolymer, or laminated structures of two or more layers thereof can be used. In addition, ordinary porous nonwoven fabrics, such as nonwoven fabrics made of high-melting-point glass fibers and polyethylene terephthalate fibers, can also be used. Furthermore, in order to ensure heat resistance or mechanical strength, coated separation membranes containing ceramic components or polymeric substances can be used, and they can be selectively used as single-layer or multi-layer structures.

[0133] (electrolyte) Furthermore, the electrolytes 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.

[0134] Specifically, the electrolyte may include an organic solvent and a lithium salt.

[0135] The organic solvent can be any solvent that serves as a medium through which ions involved in the electrochemical reaction of the battery can move, without any particular limitations. Specifically, the organic solvents include ester solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, and ε-caprolactone; ether solvents such as dibutyl ether and tetrahydrofuran; ketone solvents such as cyclohexanone; aromatic hydrocarbon solvents such as benzene and fluorobenzene; dimethyl carbonate (DMC), diethyl carbonate (DEC), methylethyl carbonate (MEC), ethylmethyl carbonate (EMC), ethylene carbonate (EC), and propylene carbonate (propylene carbonate). Carbonate solvents such as PC; alcoholic solvents such as ethyl alcohol and isopropyl alcohol; nitriles such as R-CN (where R is a linear, branched, or cyclic hydrocarbon group of C2-C20, which may include a double-bonded aromatic ring or an ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; and sulfolanes can be used. Among these, carbonate solvents are preferred, and a mixture of a cyclic carbonate having high ionic conductivity and high dielectric constant to improve the charge and discharge performance of the battery (e.g., ethylene carbonate, propylene carbonate, etc.) and a low-viscosity linear carbonate compound (e.g., ethyl methyl carbonate, dimethyl carbonate, diethyl carbonate, etc.) is more preferred.

[0136] The lithium salt can be any compound capable of providing lithium ions for use in lithium secondary batteries, without any particular limitations. Specifically, the lithium salt can be LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAlO4, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2, LiCl, LiI, LiB(C2O4)2, etc. The concentration of the lithium salt should be within the range of 0.1 to 5.0 M, preferably 0.1 to 3.0 M. When the concentration of the lithium salt falls within the above range, the electrolyte has appropriate conductivity and viscosity, exhibiting excellent electrolyte performance, and lithium ions can move effectively.

[0137] The electrolyte may further contain additives in addition to the components of the electrolyte, for the purpose of improving the battery's lifespan, suppressing the decrease in battery capacity, and improving the battery's discharge capacity. For example, the additives may include, but are not limited to, haloalkylene carbonate compounds such as difluoroethylene carbonate, pyridine, triethyl phosphite, triethanolamine, cyclic ethers, ethylenediamine, n-glyme, hexamethyl phosphate triamide, nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinone, N,N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salts, pyrrole, 2-methoxyethanol, and aluminum trichloride, either alone or in combination. The additives may be present in an amount of 0.1 to 10% by weight, preferably 0.1 to 5% by weight, relative to the total weight of the electrolyte.

[0138] As described above, the lithium secondary battery containing the positive electrode material powder according to the present invention exhibits excellent discharge capacity, output characteristics, and capacity retention rate stably, making it useful in fields such as portable devices like mobile phones, laptop computers, and digital cameras, as well as electric vehicles such as hybrid electric vehicles (HEVs).

[0139] Therefore, 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.

[0140] The aforementioned battery module or battery pack can be used as a power source for one or more medium-to-large devices, including power tools; electric vehicles (EVs), hybrid electric vehicles, and plug-in hybrid electric vehicles (PHEVs); and power storage systems.

[0141] The following describes in detail embodiments of the present invention so that those with ordinary skill in the art to which the present invention pertains can easily implement it. However, the present invention can be realized in a variety of different forms and is not limited to the embodiments described below.

[0142] Example 1 A primary firing step was performed in which nickel-cobalt-manganese-aluminum hydroxide powder, with a molar ratio of Ni:Co:Mn:Al of 85:7:6:2, and lithium hydroxide were mixed so that the molar ratio of transition metal (Ni+Co+Mn+Al):Li was 1:1.04, and then fired at 950°C for 12 hours.

[0143] Subsequently, a secondary firing step was performed, which involved sequentially maintaining the primary fired product at 820°C for 5 hours in a first maintenance period, at 950°C for 10 minutes in a second maintenance period, and at 820°C for 5 hours in a third maintenance period, thereby producing cathode material powder.

[0144] Example 2 Cathode material powder was produced in the same manner as in Example 1, except that a primary calcination step was performed at 870°C for 12 hours, followed by a secondary calcination step in which the calcined mixture was sequentially maintained at 805°C for 5 hours in a first maintenance period, at 950°C for 10 minutes in a second maintenance period, and at 805°C for 5 hours in a third maintenance period.

[0145] Comparative Example 1 A cathode material powder was produced by mixing nickel-cobalt-manganese-aluminum hydroxide powder, having a molar ratio of Ni:Co:Mn:Al of 85:7:6:2, with lithium hydroxide so that the molar ratio of transition metal (Ni+Co+Mn+Al):Li was 1:1.04, followed by a primary firing step of firing at 830°C for 22 hours.

[0146] Comparative Example 2 Cathode material powder was manufactured in the same manner as in Comparative Example 1, except that a primary firing step of firing at 950°C for 20 hours was performed.

[0147] Comparative Example 3 A nickel-cobalt-manganese-aluminum hydroxide powder with a Ni:Co:Mn:Al molar ratio of 85:7:6:2 and lithium hydroxide were mixed so that the transition metal (Ni+Co+Mn+Al):Li molar ratio was 1:1.04. A primary firing step was then performed, in which the mixture was fired at 950°C for 8 hours, followed by firing at 800°C for 8 hours to produce a cathode material powder.

[0148] Comparative Example 4 Cathode material powder was produced in the same manner as in Comparative Example 3, except that a primary firing step of firing at 965°C for 10 hours was performed, followed by firing at 860°C for 10 hours.

[0149] Comparative Example 5 A cathode material powder was produced by mixing nickel-cobalt-manganese-aluminum hydroxide powder, having a molar ratio of Ni:Co:Mn:Al of 85:7:6:2, with lithium hydroxide so that the molar ratio of transition metal (Ni+Co+Mn+Al):Li was 1:1.04. The mixture was then fired at 920°C for 8 hours, then at 950°C for 10 minutes, and finally at 920°C for 8 hours.

[0150] Comparative Example 6 Cathode material powder was produced in the same manner as in Example 1, except that a primary firing step was performed at 950°C for 12 hours, followed by a secondary firing step in which the fired mixture was sequentially maintained at 820°C for 5 hours in a first maintenance period, at 990°C for 5 minutes in a second maintenance period, and at 820°C for 5 hours in a third maintenance period.

[0151] Comparative Example 7 Cathode material powder was produced in the same manner as in Example 1, except that a primary firing step was performed at 950°C for 12 hours, followed by a secondary firing step in which the fired mixture was sequentially maintained at 820°C for 5 hours in a first maintenance period, at 890°C for 20 minutes in a second maintenance period, and at 820°C for 5 hours in a third maintenance period.

[0152] Comparative Example 8 A cathode material powder was produced in the same manner as in Example 1, except that nickel-cobalt-manganese-aluminum hydroxide powder, having a molar ratio of Ni:Co:Mn:Al of 75:5:18:2, and lithium hydroxide were mixed so that the molar ratio of the transition metal (Ni+Co+Mn+Al):Li was 1:1.04.

[0153] The manufacturing methods for Examples 1-2 and Comparative Examples 1-8 are summarized in Table 1 below.

[0154] [Table 1]

[0155] Experimental Example 1: Measurement of average particle size, BET specific surface area, particle fracture, and rolling density (Average particle size (D 50 (Measurement) 0.03 g each of the cathode material powders produced in Examples 1-2 and Comparative Examples 1-8 was dispersed in a dispersion medium, and then introduced into a laser diffraction particle size analyzer (Microtrac MT 3000) and irradiated with ultrasonic waves at approximately 28 kHz with an output of 60 W to determine the average particle size (D) of each cathode material powder. 50 The following measurements were taken. The measurement results are shown in Table 2 below.

[0156] (Measurement of BET specific surface area) Furthermore, 3g of the cathode material powder produced in Examples 1-2 and Comparative Examples 1-8 was taken and then measured using the BET method with BELSORP-mini II, and the measurement results are shown in Table 2 below.

[0157] (Measurement of particle breakdown) Furthermore, 5 g of the cathode material powder produced in Examples 1-2 and Comparative Examples 1-8 was placed in a cylindrical metal mold with a diameter of 4 cm and pressed with a pressure of 9 tons. The cumulative volume particle size distribution (PSD) was then measured to determine the generation rate of fine particles with a particle size of 1 μm or less. The generation rate of fine particles with a particle size of 1 μm or less, relative to the total volume of cathode material powder, was converted to a volume percentage and is shown in Table 2.

[0158] (Measurement of rolling density) Furthermore, the rolling density was measured using a HANTECH HLP-AC12-T. Specifically, 5 g of the cathode material powder produced in Examples 1-2 and Comparative Examples 1-8 was placed in a cylindrical metal mold with a diameter of 4 cm, pressed with a pressure of 2 tons, and then the height of the pressed mold was measured with a vernier caliber to determine the rolling density, which is shown in Table 2.

[0159] Experimental Example 2: EBSD Analysis and Measurement of Single Crystallinity Electrode slurry was prepared by mixing the respective cathode material powders produced in Examples 1-2 and Comparative Examples 1-8, carbon black as a conductive material, and polyvinylidene fluoride (PVdF) as a binder in a weight ratio of 95:2.5:2.5 in N-methylpyrrolidone (NMP). The electrode slurry was applied to one surface of an aluminum current collector, and then dried at 130°C to produce an electrode for EBSD analysis. No rolling was performed during the production of the cathode.

[0160] The cross-section of the positive electrode was cut using an ion milling device (HITACHI IM-500, accelerating voltage 6kV), and an SEM image was obtained using a FE-SEM (JEOL JSM7900F) equipped with a backscatter electron diffraction pattern analyzer (EBSD). EBSD analysis was then performed on the SEM image. The EBSD analysis was performed on a scale with a total grain count of approximately 400±10 under conditions of accelerating voltage 15kV and a WD of 15mm.

[0161] The area of ​​each grain observed in the cross-section of each cathode was measured using EBSD analysis, and the degree of single crystallinity was calculated by substituting these values ​​into equation (1). The measurement results are shown in Table 2 below.

[0162] Furthermore, Figures 1 to 3 show SEM images of cross-sections of electrodes manufactured using the cathode material powders of Examples 1 and 2 and Comparative Example 2, while Figures 4 to 6 show EBSD analysis images of cross-sections of electrodes manufactured using the cathode material powders of Examples 1 and 2 and Comparative Example 2.

[0163] [Table 2]

[0164] As can be seen from Table 2 above, Examples 1 and 2 satisfy the aforementioned range of single crystallinity compared to Comparative Examples 1 to 8.

[0165] <Manufacturing of lithium-ion secondary batteries> In Examples 1-2 and Comparative Examples 1-8, the cathode material powders prepared, carbon black as a conductive material, and polyvinylidene fluoride (PVDF) as a binder were mixed in N-methyl-2-pyrrolidone (NMP) in a weight ratio of 95:2.5:2.5 to produce a cathode slurry. The cathode slurry was applied to one surface of an aluminum current collector, dried at 130°C, and then rolled to produce a cathode.

[0166] A negative electrode slurry was prepared by mixing artificial graphite as the negative electrode active material, carbon black as the conductive material, and SBR-CMC as the binder in a weight ratio of 95:3.5:1.5. This slurry was then applied to one surface of a copper current collector, dried at 100°C, and then rolled to produce the negative electrode.

[0167] An electrode assembly was manufactured by interposing a separation membrane between the positive and negative electrodes, then positioning it inside a battery case, and subsequently injecting an electrolyte into the case to manufacture a lithium secondary battery. The electrolyte was a mixed organic solvent containing ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a volume ratio of 1:2, to which 1 M of LiPF6 was dissolved.

[0168] Experimental Example 3: Evaluation of High-Temperature Storage Characteristics Each of the lithium secondary batteries manufactured as described above was charged in CC-CV (constant current-constant voltage) mode at 0.5C until it reached 4.2V. The secondary batteries were then disassembled to separate the positive electrode. Next, the positive electrode and 200 μl of electrolyte were placed in a pouch-type battery case and sealed to manufacture a cell. The cell was then stored at 65°C for 8 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 change in water volume. The measurement results are shown in Table 3.

[0169] Experimental Example 4: Evaluation of High-Temperature Lifetime Characteristics For each lithium secondary battery manufactured as described above, one charge cycle was defined as charging at 45°C in CC-CV mode at 1C until the voltage reached 4.2V, and then discharging at a constant current of 2C until the voltage reached 2.5V. After 100 charge-discharge cycles, the capacity retention rate was measured to evaluate the high-temperature life characteristics. The measurement results are shown in Table 3.

[0170] [Table 3]

[0171] From Table 3 above, it can be confirmed that batteries using the cathode material powders of Examples 1 to 2, whose single-crystallinity degree of formula (1) satisfies the range of the present invention, exhibit superior high-temperature life characteristics and high-temperature storage characteristics compared to batteries using the cathode material powders of Comparative Examples 1 to 8.

Claims

1. It contains lithium nickel oxide particles represented by the following chemical formula 1, A cathode material powder having a single crystallinity degree of 1.85 to 3.00, represented by the following formula (1): [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, and M ２ is one or more selected from the group consisting of Ti, Mg, Al, Zr, Y, Ba, Ca, Sr, W, Ta, Nb, and Mo, 0.80≦a≦1.20, 0.80≦b<1, 0<c<0.45, 0<d<0.45, and 0≦e≦0.20, [Math 1] In the above formula (1), A ｋ The positive electrode material powder is characterized by the area of ​​the k-th grain measured when an electrode manufactured using the positive electrode material powder is subjected to ion milling and then the cross-section of the electrode is analyzed by backscattered electron diffraction (EBSD), where n is the total number of grains measured by the backscattered electron diffraction (EBSD) analysis, and is between 200 and 500.

2. The aforementioned chemical formula 1 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 The positive electrode material powder according to claim 1, wherein is one or more selected from the group consisting of Ti, Mg, Al, Zr, Y, Ba, Ca, Sr, W, Ta, Nb, and Mo, and satisfies 0.85 ≤ a1 ≤ 1.20, 0.80 ≤ b1 < 1, 0 < c1 < 0.18, 0 < d1 < 0.18, 0 < d2 < 0.15, 0 ≤ e1 ≤ 0.20, and 0 < d1 + d2 < 0.

33.

3. The specific surface area of ​​the aforementioned positive electrode material powder is 0.40 m². ２ / g ~ 0.75m ２ The positive electrode material powder according to claim 1, wherein the weight is / g.

4. The positive electrode material powder according to claim 1, wherein the rolling density of the positive electrode material powder is 2.9 g / cc to 3.2 g / cc.

5. The positive electrode material powder according to claim 1, wherein when the positive electrode material powder is pressurized at 9 tons, the generation rate of fine particles smaller than 1 μm is 6 volume% or less.

6. The average particle size (D) of the positive electrode material powder ５０ The cathode material powder according to claim 1, wherein the particle size is 2 μm to 5 μm.

7. The cathode material powder according to claim 1, wherein the cathode material powder has a single crystallinity degree represented by formula (1) of 2.0 to 2.

5.

8. A method for producing the positive electrode material powder described in claim 1, (S1) A step of mixing the positive electrode active material precursor and lithium source and then performing primary calcination, (S2) The step of performing a secondary firing on the primary fired product, The aforementioned primary firing step is carried out at 850°C to 960°C for 10 to 20 hours. The aforementioned secondary firing step sequentially includes a first maintenance section maintained at 720°C to 850°C, a second maintenance section maintained at 900°C to 970°C, and a third maintenance section maintained at 720°C to 850°C. A method for producing the positive electrode active material precursor, wherein the nickel content in the total metals excluding lithium is 80 mol% or more.

9. The manufacturing method according to claim 8, wherein the primary firing step is performed at 870°C to 960°C for 10 to 15 hours.

10. The manufacturing method according to claim 8, wherein the first maintenance period and the third maintenance period are each maintained independently for 5 to 10 hours.

11. The manufacturing method according to claim 8, wherein the second maintenance interval is maintained for 5 to 60 minutes.

12. The manufacturing method according to claim 8, wherein the total firing time for the secondary firing step is 10 to 15 hours.

13. A positive electrode comprising the positive electrode material powder described in claim 1, The negative electrode and, Separation membrane and A lithium secondary battery containing an electrolyte.

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