Method for preparing positive electrode materials for rechargeable lithium-ion batteries

Abstract

To provide a preparation method of a positive electrode material for a charging type lithium ion battery.SOLUTION: The present invention provides a method for preparing a positive electrode active material for rechargeable lithium ion batteries. The process comprises a sintering step having a short sintering time. Thereby, a production throughput is improved. More specifically, the present method is adopted to positive electrode active material powders having a general formula Li(1+a(NixMnyCozMec)(1-a)O2 [in the formula, Me is comprises at least one element of a group consisting of Al, Mg, Ti, Zr, W, Nb, B, and Sr, with -0.1≤a≤0.1, 0.33≤x≤0.95, 0≤y≤0.35, 0<z≤0.35, and 0≤c≤0.05, and x+y+z+c=1]. The sintering step is performed for a predetermined sintering time ts, expressed in hours, and at a predetermined temperature expressed in °C, such that 0.3≤ts≤6.0, and 1140+50 Log10(6 / t)-580x≤Ts≤1245+50 Log10(6 / ts)-580x.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for preparing cathode materials for lithium-ion batteries that achieves very short sintering times and reduces overall energy input while maintaining the electrochemical performance of the product.

[0002] Introduction The present invention relates to a method for preparing powdered positive electrode active materials for rechargeable lithium-ion batteries. More specifically, the method includes a sintering step with short sintering times, thereby improving production throughput.

[0003] According to Schmuch et al. (Nature Energy, 2018, Vol. 3, pp. 267-278, Fig. 7), cathode active materials based on lithium nickel manganese cobalt metal oxide (hereafter referred to as NMC) account for approximately 50% of the cost of a lithium-ion battery. Therefore, it is important to make the manufacturing process for such materials as cost-effective as possible.

[0004] WO 2018 / 158078 A1 describes state-of-the-art industrial processes for producing powdered NMC materials. Preparation Example 1 describes a conventional direct-sintering process in which a mixture of transition metal hydroxide powder and Li-containing powder is heated to above 800°C for more than 10 hours. Preparation Example 3 teaches a double-sintering process. Both examples demonstrate limitations in production throughput due to the long sintering times of more than 10 hours.

[0005] The complete firing process typically consists of heating, reacting, sintering, and cooling steps. As mentioned above, the bottleneck is the sintering step, which typically requires a residence time of 10 hours or more. This long residence time has been found to be primarily due to the low thermal conductivity of NMC powders, combined with the need for uniform temperature throughout the bulk of the product.

[0006] European Patent No. 3054508 describes a method for preparing cathode active materials. In this method, lithium hydroxide hydrate is added to a hydroxide precursor to prepare a mixed powder with a Li:(Ni, Co, Mn) molar ratio of 101:99. This powder is molded and heated in an air atmosphere under atmospheric pressure from room temperature to 750°C over 10 hours. It is then sintered at 750°C for 4 hours to obtain pellets. After sintering, the heater is turned off and the pellets are left to cool naturally in the furnace. After 5 hours, the furnace temperature is reduced to approximately 200°C. The pellets are then cooled for a further 24 hours to below 100°C before being crushed.

[0007] European Patent No. 2523240 discloses a material used as a positive electrode material for lithium secondary batteries, which reduces costs, improves safety, and improves load characteristics, and further improves high-voltage characteristics and powder handleability due to improved bulk density. This technology relates to a lithium transition metal compound powder for use as a positive electrode material for lithium secondary batteries, which includes secondary particles composed of primary particles having two or more types of composition and a lithium transition metal compound capable of inserting and releasing lithium ions, and the powder exhibits a pore size distribution curve with a peak at a pore radius of 80 nm to 800 nm. The secondary particles include primary particles of a compound represented by a structural formula containing at least one element selected from the group consisting of As, Ge, P, Pb, Sb, Si, and Sn, and the primary particles of the compound are present at least inside the secondary particles.

[0008] European Patent No. 2202828 describes a lithium transition metal compound powder for use as a positive electrode material in lithium secondary batteries, which can achieve both improved load characteristics such as speed and output characteristics and higher density. The lithium transition metal compound powder contains, as its main component, a lithium transition metal compound having a layered crystalline structure that allows for the desorption and insertion of lithium ions. Primary particles aggregate to form secondary particles, with the ratio A / B of the median diameter of the secondary particles to the average diameter (average primary particle diameter B) ranging from 8 to 100, or 0.01·FWHM(110)·0.5. The FWHM(110) is the half-width at half maximum of the (110) diffraction peak, which is located near a diffraction angle 2 of 64.5° in powder X-ray diffraction analysis using CuK± radiation.

[0009] Insufficient sintering time or temperature leads to poor electrochemical performance of the battery due to either insufficient crystallite size or non-uniform growth of the primary particles. Summary of the Invention [Means for solving the problem]

[0010] The present invention provides a solution to at least one of the above-mentioned problems by providing a method for preparing a cathode material for rechargeable lithium-ion batteries as set forth in claim 1. Such a method has the advantage of very short sintering times and reduced overall energy input, while maintaining the electrochemical performance of the product. At the same time, the present invention provides a method for improving production throughput. DETAILED DESCRIPTION OF THE INVENTION

[0011] Unless otherwise defined, all terms used in disclosing the present invention, including technical and scientific terms, have the meanings commonly understood by one of ordinary skill in the art to which this invention belongs. By way of further guidance, term definitions are included to better understand the teachings of the present invention.

[0012] As used herein, the following terms have the following meanings: As used herein, "a," "an," and "the" refer to both singular and plural referents unless the context clearly dictates otherwise. By way of example, "a compartment" refers to one or more compartments.

[0013] As used herein, "about" referring to a measurable value such as a parameter, amount, duration, etc., is meant to encompass a variation from the specified value of no more than ±20%, preferably no more than ±10%, more preferably no more than ±5%, even more preferably no more than ±1%, and still more preferably no more than ±0.1%, to the extent appropriate for practice with the disclosed invention, provided that the value referred to by the "about" modifier is itself specifically disclosed.

[0014] As used herein, "comprise," "comprising," and "comprised of" are synonymous with "include," "includes," or "contain," "containing," and "contains," and are inclusive or open-ended terms that specify the presence of what follows, e.g., a component, but do not exclude or preclude the presence of additional, unlisted components, features, elements, materials, steps that are known in the art or disclosed therein.

[0015] The recitation of numerical ranges by endpoints includes not only the recited endpoints but also all numbers and fractions subsumed within that range. All percentages, unless otherwise defined or unless a different meaning is apparent to one of ordinary skill in the art from their use and the context in which they are used, are understood to be percent by weight, abbreviated as "wt %," or percent by volume, abbreviated as "vol %."

[0016] method In a first aspect, the present invention provides a method for preparing a cathode material for a lithium-ion battery, comprising: step (i) heating in a furnace from a temperature of less than 200° C. to a temperature T s heating a mixed metal compound pM comprising lithium, nickel, and at least one metal selected from cobalt, manganese, and aluminum, or heating a first mixture M1 comprising A1: a mixed metal compound P1 comprising nickel and at least one metal selected from cobalt, manganese, and aluminum, and B1: a lithium compound L1, until step (ii) subjecting the mixed metal compound pM or the first mixture to a temperature T s Time t for 0.3 hours to 6.0 hours s to obtain a heat-treated mixed metal compound M, s and the time t s is the formula: 1140+50.log 10 (6 / t s )-580.x≦T s ≦1200 [wherein x is the atomic ratio of nickel to the total amount of nickel, cobalt, manganese, and aluminum in the mixed metal compound pM or the first mixture, 0.30≦x≦0.99, and 300° C.h≦T s .t s <3000°C.h], and - step (iii) cooling the heat-treated mixed metal compound M obtained in step (ii), The total time for steps (i) and (ii) is 0.3 hours to 12.0 hours.

[0017] The present invention provides a method for preparing cathode active materials with significantly shorter sintering times and reduced overall energy input while maintaining the electrochemical performance of the product, while also providing a method for improving production throughput.

[0018] Preferably, the present invention relates to a method according to the first aspect of the present invention, wherein the total time for steps (i) and (ii) is 0.5 hours to 8.0 hours, preferably 1.0 hours to 6.0 hours, more preferably 1.0 hours to 3.0 hours, even more preferably 1.0 hours to 2.5 hours, and most preferably the total time for steps (i) and (ii) is 1.0 hours to 2.0 hours, and the time t of the sintering step (ii) is s The time t of the sintering step (ii) is preferably 0.3 to 1.5 hours. s is 0.5 hours to 3.0 hours, and further 0.5 hours to 2.0 hours.

[0019] Preferably, the present invention relates to a method according to the first aspect of the present invention, wherein in step (ii), 300°C.h≦T s .t s ≦2800℃.h, preferably 300℃.h≦T s .t s ≦2700℃.h, more preferably 300℃.h≦T s .t s ≦2600°C.h, most preferably 300°C.h≦T s .t s ≦2400°C.h

[0020] More preferably, the present invention relates to a method according to the first aspect of the present invention, wherein in step (ii) 300°C.h≦T s .t s ≦1600°C.h, preferably 300°C.h≦T s .t s ≦1000°C.h, more preferably 300°C.h≦T s .t s ≦600°C.h

[0021] Preferably, the present invention relates to a method according to the first aspect of the present invention, wherein in step (i) the mixed metal compound pM is heated to a temperature below 200° C., preferably below 100° C., more preferably room temperature, to a sintering temperature T s Heating time t His between 0.3 hours and 6 hours, preferably between 0.5 hours and 2 hours, and preferably the mixed metal compound pM is heated in step (i) at a heating rate of at least 5°C / min, preferably at least 8°C / min, more preferably at least 10°C / min. Increasing the heating rate can increase throughput. Preferably, the compound is heated at a rate of at most 50°C / min, preferably at most 25°C / min. Reducing the heating rate can limit temperature differences within the mixed metal compound pM material layer.

[0022] Preferably, the present invention relates to a method according to the first aspect of the present invention, wherein the mixed metal compound pM is obtained by heating a second mixture (M2) containing A2: a mixed metal compound P2 containing nickel and at least one metal selected from cobalt, manganese and aluminum, and B2: a lithium compound L2, and the mixture is heated at a temperature T I Time from 1 hour to 24 hours I Preferably, the temperature T is between 600°C and 1000°C. I 2 to 10 hours I and more preferably for a time t of 2 to 6 hours. I The method further comprises the steps of:

[0023] More preferably, the mixed metal compound pM is provided as a mixture comprising one or more mixed metal compounds pM described herein and one or more lithium compounds L, preferably the mixed metal compound pM is mixed with a predetermined amount of lithium compound L prior to the heat treatment to form a mixture, and upon heat treatment of the mixture, a compound of the general formula Li 1+a M' 1-aA cathode active material is formed according to the formula: O2, where a is -0.5 to 0.5, preferably -0.2 to 0.2, more preferably -0.1 to 0.1, and most preferably -0.05 to 0.05, and M' is the cation portion of the mixed metal compound described herein. Preferably, the mixed metal compound pM is mixed with at least one lithium compound, preferably in a dry mixing process. The lithium compound is preferably selected from Li2O, LiOH, and Li2CO3, either by itself or as a hydrate, e.g., LiOH·H2O. It is also possible to combine two or more lithium compounds. Examples of equipment suitable for mixing the mixed metal compound pM with the lithium compound include a tumbler mixer, a plowshare mixer, and a free-fall mixer. After the heat treatment step in the method of the present invention, the particulate material can be easily removed from the support and subjected to further process steps, such as cooling, sieving, or a combination of crushing and sieving the product.

[0024] In a preferred embodiment, the present invention provides a method according to the first aspect of the invention, wherein the mixture further comprises a compound selected from metal oxides, hydroxides and oxyhydroxides of Zr, Ti, W and, in particular, Al.

[0025] Preferably, the present invention provides a method according to the first aspect of the present invention, wherein the heat-treated mixed metal compound M obtained from step (ii) is discharged from the furnace before step (iii). This allows for a faster cooling rate during production, thereby increasing throughput. Preferably, the present invention provides a method according to the first aspect of the present invention, wherein the heat-treated mixed metal compound M obtained from step (ii) is cooled at an average cooling rate of 2°C / min to 100°C / min, preferably at a cooling rate greater than 4°C / min, more preferably at a cooling rate greater than 10°C / min.

[0026] Preferably, the present invention provides a method according to the first aspect of the invention, wherein the mixed metal compound pM is provided in step (i) as a powder. Preferably, the powder is a metal of general formula Li (i+a) (Ni x Mn y Co z Me c ) (1-a) O2 and has a crystallinity of less than 70 nm, preferably less than 50 nm.

[0027] Preferably, the present invention relates to a method according to the first aspect of the present invention, wherein the sintering temperature is T s ≦1745+50.log 10 (6 / t s )-580.x, preferably, the T s ≦1445+50.log 10 (6 / t s )-580.x, more preferably, the T s ≦1345+50.log 10 (6 / t s )-580.x. Most preferably, the sintering temperature T s ≦1245+50.log 10 (6 / t s )-580.x.

[0028] Preferably, the present invention relates to a method according to the first aspect of the present invention, wherein the sintering temperature is 1170+50.log 10 (6 / t s )-580.x≦T s , preferably 1200+50.log 10 (6 / t s )-580.x≦T s The present invention provides a method for

[0029] Preferably, the present invention provides a method according to the first aspect of the present invention for preparing a positive electrode active material powder having a crystallite size of 34 nm to 46 nm.

[0030] Preferably, the present invention provides compounds of the general formula Li (1+a) (Nix Mn y Co z Me c ) (1-a) O2 [where Me consists of at least one element from the group consisting of Al, Mg, Ti, Zr, W, Nb, B, and Sr, -0.1 ≦ a ≦ 0.1, 0.33 ≦ x ≦ 0.95, 0 ≦ y ≦ 0.35, 0 < z ≦ 0.35, 0 ≦ c ≦ 0.05, and x + y + z + c = 1]. A method according to the first aspect of the present invention for preparing a positive electrode active material powder, including a sintering step having a predetermined sintering time and a predetermined sintering temperature, and a predetermined time t represented in hours s is such that 0.3 ≦ t s ≦ 6.0, and a predetermined temperature T represented in °C s is such that 1140 + 50Log 10 (6 / t s ) - 580.x ≦ T s ≦ 1245 + 50Log 10 (6 / t s ) - 580.x. A method is provided. Preferably, the present invention provides a method according to the first aspect of the present invention, wherein a predetermined time t represented in hours is such that 0.5 ≦ t ≦ 5.0. Preferably, the present invention is generally Li (1+a) (Ni x Mn y Co z Me c ) (1-a) O2 [where -0.01 ≦ a ≦ 0.05, 0.60 ≦ x ≦ 0.95, 0 ≦ y ≦ 0.20, 0 < z ≦ 0.20, 0 ≦ c ≦ 0.05, and x + y + z + c = 1]. A method according to the first aspect of the present invention for preparing a positive electrode active material powder, wherein a predetermined temperature T represented in °C is such that 1175 + 50Log 10 (6 / t) - 580x ≦ T ≦ 1245 + 50Log 10 (6 / t) - 580x. A method is provided. Preferably, the present invention provides a method according to the first aspect of the present invention for preparing a positive electrode active material powder having a crystallite size of 34 nm to 46 nm

[0031] Mixed metal compound pM In one embodiment, the present invention provides a process according to the first aspect of the invention, wherein the mixed metal compound pM is provided in step (i) in the form of a granular material such as a powder or in the form of pellets having dimensions of 0.5 mm to 10.0 mm, preferably 1.0 mm to 5.0 mm.

[0032] In a preferred embodiment, the present invention provides a method according to the first aspect of the present invention, wherein the mixed metal compound pM is composed of particulate matter having a median particle size d50, as determined by laser particle size distribution measurement, of at most 100 μm, preferably at most 50 μm, more preferably 0.5 μm to 25.0 μm, and most preferably 1 μm to 15 μm. In a preferred embodiment of the present invention, the average particle diameter (d50) of the mixed metal compound pM is in the range of 4 to 14 μm, preferably 7 to 10 μm. The median particle size (PD50 or d50) of the compound is obtained by laser particle size distribution measurement. Herein, laser particle size distribution is measured using a Malvern Mastersizer 2000 with a Hydro 2000MU wet dispersion accessory after dispersing the powder in an aqueous medium. To improve the dispersion of the powder in the aqueous medium, sufficient ultrasonic irradiation (typically 1 minute for 12 ultrasonic displacements) and stirring are applied, and a suitable surfactant is introduced.

[0033] In a preferred embodiment, the present invention relates to a method according to the first aspect of the invention, wherein the mixed metal compound pM is comprised of particulate matter and has a density of 0.4 g / cm 3 Apparent density higher than 0.6 g / cm 3 Higher density than 0.8 g / cm 3 a density higher than 1.0 g / cm 3 a density higher than 1.4 g / cm 3 Higher density than 1.5g / cm 3 Preferably, the mixed metal compound pM is comprised of particulate matter and has a density greater than 2.3 g / cm. 3 less than 2.1 g / cm 3 Less than 2.0 g / cm3 It is provided at a density of less than

[0034] The present invention provides a method according to a first aspect of the present invention, wherein the mixed metal compound pM comprises lithium, nickel, and at least one metal selected from cobalt, manganese, and aluminum. In a preferred embodiment, the mixed metal compound pM comprises Ni in an amount of at least 50 mol%, preferably at least 60 mol%, more preferably 60 mol% to 99 mol%, based on the total content of nickel, cobalt, manganese, and aluminum in the mixed metal compound pM. Most preferably, the mixed metal compound pM comprises Ni in an amount of 60 mol% to 95 mol%, even more preferably 80 mol% to 95 mol%, for example, 80 mol%, 85 mol%, 90 mol%, 95 mol%, and all values ​​therebetween.

[0035] In a preferred embodiment, the present invention provides a method according to the first aspect of the invention, wherein the mixed metal compound pM comprises a mixed metal hydroxide, carbonate, oxyhydroxide and / or oxide, and the mixed metal compound pM preferably further comprises one or more metals selected from Ba, Al, Ti, Zr, W, Fe, Cr, Mo, Nb, Mg and V, more preferably selected from Al, Ti, Zr, W and Mg.

[0036] In one preferred embodiment of the invention, the mixed metal compound pM comprises Ni, Co and Al. In another preferred embodiment of the invention, the mixed metal compound pM comprises Ni, Co and Mn.

[0037] In a preferred embodiment of the invention, the mixed metal compound pM is according to general formula (I), where the lithium and counterion(s) have been omitted for clarity. Ni x M” y CO z E d (I) In the formula, x is in the range of 0.15 to 0.95, preferably 0.30 to 0.92, more preferably 0.50 to 0.90, and most preferably 0.60 to 0.85; y is in the range of 0.00 to 0.80, preferably 0.01 to 0.60, and more preferably 0.05 to 0.20; z is in the range of 0.00 to 0.40, preferably 0.01 to 0.30, and more preferably 0.02 to 0.10, and d is in the range of 0.00 to 0.10, preferably 0.001 to 0.005; M″ is one or both of Mn and Al; and E is selected from the group consisting of Ba, Al, T, and the like. and x+y+z+d=1, and y+z+d≧0.05, preferably y+z+d≧0.08, more preferably y+z+d≧0.10. Preferably, E is selected from Al, Mg, W, Ti, Zr, and combinations thereof, more preferably E is selected from Al, Mg, Zr, and combinations thereof.

[0038] Preferred examples of mixed metal compounds pM according to general formula (I) are Ni 1 / 3 Co 1 / 3 Mn 1 / 3 , Ni 0.4 Co 0.2 Mn 0.4 , Ni 0.5 Co 0.2 Mn 0.3 , Ni 0.6 Co 0.2 Mn 0.2 , (Ni 0.85 Co 0.15 ) 0.98 Al 0.02 , (Ni 0.85 Co 0.15 ) 0.97 Al 0.03 , (Ni 0.85 Co 0.15 ) 0.95 Al 0.05 , Ni 0.8 Co 0.1 Mn 0.1 , and Ni 0.7 Co 0.2 Mn0.1 , Ni 0.2 Co 0.1 Mn 0.7 , Ni 0.25 Co 0.15 Mn 0.6 , (Ni 0.6 Co 0.2 Mn 0.2 ) 0.997 Al 0.003 , (Ni 0.6 Co 0.2 Mn 0.2 ) 0.998 AI 0.002 , (Ni 0.7 Co 0.2 Mn 0.1 ) 0.997 Al 0.003 , (Ni 0.7 Co 0.2 Mn 0.1 ) 0.998 Al 0.002 , (Ni 0.8 Co 0.1 Mn 0.1 ) 0.997 Al 0.003 , (Ni 0.8 Co 0.1 Mn 0.1 ) 0.998 Al 0.002 is selected from.

[0039] The mixed metal compound pM may contain trace amounts of other metal ions, e.g., trace amounts of ubiquitous metals such as Na, Ca, or Zn, but such trace amounts are not considered within the context of the present invention. The term "trace amount" in the context of the present invention refers to an amount of 0.05 mol % or less, relative to the total metal content of the mixed metal compound pM.

[0040] The mixed metal compound pM may be a single crystal product or a polycrystalline product. Preferably, the mixed metal compound pM has a polycrystalline structure. The mixed metal compound pM preferably includes secondary particles formed by a plurality of aggregated primary particles. The particle shape of the secondary particles of the mixed metal compound pM is preferably an ellipsoid of revolution, that is, a particle having a spherical shape. The spherical ellipsoid includes not only an exact spherical one but also a particle in which the difference between the maximum diameter and the minimum diameter of at least 90% (number average) of a representative sample is 10% or less.

[0041] In one embodiment of the present invention, the mixed metal compound pM is provided as spherical secondary particles that are aggregates of primary particles. Even more preferably, the mixed metal compound pM is provided as spherical secondary particles that are aggregates of spherical primary particles or aggregates of small plates.

[0042] In a second aspect, the present invention provides a secondary lithium ion battery including a positive electrode active material obtained by the method according to the first aspect of the present invention.

[0043] This object of the present invention is to prepare a positive electrode active material powder having the general formula Li (1+a) (Ni x Mn y Co<000​​​​​​​​​​​​​​​​​​​​For the combination of the above characteristics, the range 0.33≦x≦0.90 is preferred.

[0044] The suffixes a, x, y, z, and c denote atomic ratios.

[0045] As shown in Table 1, EX1-01, it has been observed in practice that a satisfactory first discharge capacity of over 175 mAh / g can be obtained when the product is prepared according to the following method: - the sintering time t is 0.33 hours, - Ni content x is 0.60, The sintering temperature T is 940°C.

[0046] It has also been observed that secondary particles, which are aggregates of primary particles, so-called "polycrystalline NMCs", are generally present in a desirable manner.

[0047] The sintering temperature T is expressed in °C and is defined as the maximum residence temperature during the firing stage. Residence temperature means the temperature at which the powder in question remains for more than 30% of the total sintering time.

[0048] The sintering time t is expressed in hours and is defined as the time that the powder in question remains above the temperature at which sintering is likely to occur (defined as 650° C.).

[0049] In the manufacturing process of powdered NMC materials, both the sintering temperature and sintering time are important process parameters. Powdered NMC materials can achieve good electrochemical properties, such as high first discharge capacity, if they have an appropriate crystallite size. The crystallite size is mainly controlled by the sintering temperature and sintering time.

[0050] The sintering temperature range is 1140+50Log 10 (6 / t)-580x≦T≦1245+50Log 10The optimum range is (6 / t)-580x, which provides the best electrochemical properties for the powdered NMC material. If the sintering temperature is higher or lower than the range of the present invention, the electrochemical properties such as the initial discharge capacity will be deteriorated.

[0051] Ni has been shown to promote sintering. Therefore, if the NMC material has a higher Ni content, a lower sintering temperature is sufficient to obtain the optimum crystallite size. For example, assuming a sintering time t of 3 hours, LiNi 0.34 Mn 0.33 Co 0.33 The minimum sintering temperature T of the material composition with O2 is 958°C, while that of LiNi 0.60 Mn 0.20 Co 0.20 The minimum sintering temperature T for O2 is 807°C.

[0052] The reason for the reduction in sintering time is - The insight that higher temperatures lead to more accelerated reaction rates while still producing electrochemically high performance products; -Optimization of sintering time depending on Ni content.

[0053] On the other hand, sintering times of less than 0.3 hours are undesirable. Such extremely short sintering times would in fact require higher sintering temperatures, which could result in Li evaporation and undesirable Li stoichiometry.

[0054] In a first embodiment, the present invention provides compounds of the general formula Li (1+a) (Ni x Mn y Co z Me c ) (1-a)O2 [where Me consists of at least one element selected from the group consisting of Al, Mg, Ti, Zr, W, Nb, B, and Sr, -0.1 ≦ a ≦ 0.1, 0.33 ≦ x ≦ 0.95, 0 ≦ y ≦ 0.35, 0 < z ≦ 0.35, 0 ≦ c ≦ 0.05, and x + y + z + c = 1], a method for preparing a positive electrode active material powder, including a sintering step having a predetermined sintering time and a predetermined sintering temperature, and a predetermined time t represented in hours s is such that 0.3 ≦ t s ≦ 6.0, and a predetermined temperature T represented in °C s is 1140 + 50Log 10 (6 / t s ) - 580.x ≦ T s ≦ 1245 + 50Log 10 (6 / t s ) - 580.x, and provides a method.

[0055] The term "predetermined" means that the operating temperature and time are determined before starting the process.

[0056] In another embodiment, the above method is applied, and a predetermined sintering time t represented in hours is 0.5 ≦ t ≦ 5.0.

[0057] In another embodiment, the above method is applied to the preparation of a positive electrode active material powder having the general formula Li (1+a) (Ni x Mn y Co z Me c ) (1-a) O2 [where -0.01 ≦ a ≦ 0.05, 0.60 ≦ x ≦ 0.95, 0 ≦ y ≦ 0.20, 0 < z ≦ 0.20, 0 ≦ c ≦ 0.05, and x + y + z + c = 1], and a predetermined temperature T represented in °C is 1175 + 50Log 10 (6 / t) - 580x ≦ T ≦ 1245 + 50Log 10 (6 / t) - 580x.

[0058] In another embodiment, the above method is applied to the preparation in which a positive electrode active material powder having a crystallite size of 34 nm to 46 nm is obtained.

[0059] The following measurements are related to X-ray diffraction.

[0060] X-ray diffraction patterns of powder samples were collected using a Rigaku X-ray diffractometer (Ultima IV) with a Cu Ka radiation source (40 kV, 40 mA) emitting at a wavelength of 1.5418 Å. The instrument configuration was set to a 1° Soller slit (SS), a 10 mm divergent height limiting slit (DHLS), a 1° divergence slit (DS), and a 0.3 mm reception slit (RS). The goniometer diameter was 185 mm. Diffraction patterns were acquired over a 20° range from 15° to 85°, with a scan speed of 0.1° / min and a step size of 0.02° / scan.

[0061] The crystallite size, expressed in nm, is calculated from the diffraction angle and full width at half maximum (FWHM) of the peak corresponding to the (104) plane obtained from the X-ray diffraction pattern using the Scherrer equation. Crystallite size (nm)=Kλ / (β cos θ), where: -K is the Scherrer constant (K=0.9), -λ is the wavelength of the X-ray (CuKa=1.5418Å), -β is the FWHM, expressed in °, -θ is half of 2θ, where 2θ is the center of the peak, and is expressed in rad (radians).

[0062] In the X-ray diffraction pattern, a peak corresponding to the (104) plane, assigned to the crystal structure of space group R-3m, was observed at approximately 44.5±1°. θ and β were calculated using the Lorentzian model in the 2θ range of 43° to 46° by the nonlinear curve fitting method in Origin 9.1. The contribution of Kα-2 was not subtracted.

[0063] LaB6 (lanthanum hexaboride) is used as a standard to calibrate the instrument's diffraction peak broadening. The (011) peak of LaB6 powder, located in the 28°-32° range, has a β of 0.1264° and a 2θ (peak center) of 30.3719°. The (111) peak of LaB6 powder, located in the 36°-39° range, has a β of 0.1357° and a 2θ (peak center) of 37.4318°. Therefore, the crystallite sizes calculated from the (011) and (111) peaks of LaB6 powder are 65.2 nm and 61.9 nm, respectively. Because instrumental peak broadening significantly affects β (FWHM), the instrument must be calibrated to obtain the crystallite size of LaB6 powder shown above.

[0064] The following evaluation methods are for the fabrication of coin cells.

[0065] A solid-containing slurry containing powdered NMC material, a conductor (Super P, Timcal), and a binder (KF#9305, Kureha) in a weight ratio of 90:5:5 was mixed with a solvent (NMP, Sigma-Aldrich) in a high-speed homogenizer to obtain a homogenized slurry. The homogenized slurry was spread onto one side of an aluminum foil using a doctor blade coater with a 230 μm gap. The slurry-coated aluminum foil was dried in an oven at 120 °C, pressed using a calendar tool, and then dried again in a vacuum oven to completely remove the solvent.

[0066] The coin cells are assembled in a glove box filled with inert gas (argon). For discharge capacity analysis, a separator (Celgard) is placed between the positive electrode and a piece of lithium foil used as the negative electrode. 1M LiPF6 in EC:DMC (1:2 by volume) is used as the electrolyte and is dropped between the separator and the electrode. The coin cells are then completely sealed to prevent electrolyte leakage.

[0067] The initial charge / discharge capacities (CQ1 and DQ1) are measured in constant current mode at a rate of 0.1C, where 1C is defined as 160mAh / g, with a charge cutoff voltage of 4.30V and a discharge cutoff voltage of 3.0V.

[0068] Example 1 General formula Ni 0.60 Mn 0.20 Co 0.20 O 0.15 (OH) 1.85 The mixed nickel manganese cobalt oxyhydroxide powder (MTH1) represented by the formula (I) is prepared by coprecipitation in a large continuous stirred tank reactor (CSTR) using a mixed nickel manganese cobalt sulfate solution, a sodium hydroxide solution, and an ammonia solution. MTH1 is mixed with LiOH-H2O to obtain a first mixture (M1) with an atomic ratio of Li / (Ni + Mn + Co) of 1.01. The first mixture (M1) is then heated at 800°C under oxygen flow for 10 hours in a first calcination step (heating and reaction step) to obtain a first intermediate product (INP1). The intermediate product INP1 is then cooled to room temperature.

[0069] Subsequently, the intermediate product INP1 is heated from room temperature to 940°C over one hour. An alumina crucible containing 25 g of the first intermediate product (INP1) is heated to 940°C (sintering temperature T s ) for 0.33 hours (sintering time t s ) sintering. The sintered powder (SP1) is cooled and crushed to separate the agglomerated particles, resulting in a powder of the general formula Li (1+a) (Ni 0.60 Mn 0.20 Co 0.20 ) (1-a) A powdered polycrystalline NMC material EX1-01 of O2 [wherein a=0.050] is obtained.

[0070] Powdered NMC materials EX1-02, EX1-03, EX1-04, EX1-05, and EX1-06 were prepared in the same manner as EX1-01, except that the sintering temperatures and sintering times in Table 1 were applied.

[0071] The method for preparing EX1-01 to EX1-06 is according to the present invention.

[0072] Comparative Example 1 Powdered NMC materials CEX1-01, CEX1-02, CEX1-03, CEX1-04, CEX1-05, and CEX1-06 were prepared in the same manner as EX1-01, except that the sintering temperature and sintering time in Table 1 were used in the sintering process.

[0073] The methods for preparing CEX1-01 to CEX1-06 are not according to the present invention.

[0074] Example 2 In a large-scale continuous stirred tank reactor (CSTR), a mixed nickel manganese cobalt sulfate solution, sodium hydroxide solution, and ammonia solution are co-precipitation-based to obtain Ni 1 / 3 Mn 1 / 3 Co 1 / 3 O 0.33 (OH) 1.67 A mixed nickel manganese cobalt oxyhydroxide powder (MTH2) is prepared. MTH2 is mixed with LiOH-H2O to obtain a first mixture (M2) with an atomic ratio of Li / (Ni + Mn + Co) of 1.10. The first mixture (M2) is heated at 700°C for 10 hours under a flow of oxygen in a first calcination step (heating and reaction step) to obtain a first intermediate product (INP2).

[0075] An alumina crucible containing 10 g of the first intermediate product (INP2) was heated to 990°C (sintering temperature T s ) in a furnace heated to 990°C for 1 hour (sintering time t s ) sintering. The sintered powder (SP2) is cooled and crushed to separate the agglomerated particles, resulting in a powder of the general formula Li (1+a) (Ni 1 / 3 Mn 1 / 3 Co 1 / 3 ) (1-a) Powdered NMC material EX2 of O2 is obtained.

[0076] The method for preparing EX2 is according to the invention.

[0077] Comparative Example 2 Powdered NMC material CEX2 is prepared in the same manner as EX2, except that the sintering time in Table 1 is used in the sintering process.

[0078] The method for preparing CEX2 is not in accordance with the present invention.

[0079] Table 1 shows the sintering conditions for preparing the powdered NMC materials and their physical, chemical, and electrochemical properties. The powdered NMC materials of Example 1 and Comparative Example 1 (EX1-01 to EX1-06, CEX1-01 to CEX1-06) have the same general formula Li (1+a) (Ni 0.60 Mn 0.20 Co 0.20 ) (1-a) O2 [where a=0.050].

[0080] According to conventional sintering conditions, the sintering temperature T s and 10 hours of sintering time t s CEX1-05 was prepared using the method described above. CEX1-05 was considered a satisfactory powdered NMC material, having a good discharge capacity of 174.5 mAh / g and an appropriate crystallite size of 40 nm. It was demonstrated that powdered NMC materials with a crystallite size of 40±1 nm could be prepared using much shorter sintering times: 0.33 hours (EX1-01), 1 hour (EX1-02), and 3 hours (EX1-05) at 940°C, 910°C, and 880°C, respectively. The powdered NMC materials prepared according to the present invention, EX1-01, EX1-02, and EX1-05, have first discharge capacities (DQ1) at least as high as those of CEX1-05, despite the much shorter sintering times.

[0081] The optimal range for the crystallite size of powdered polycrystalline NMC materials is 34 nm to 46 nm. When the sintering time is less than 0.30 h (in the cases of CEX1-01 and CEX1-03), the crystallite size is observed to be less than 34 nm, despite the relatively high sintering temperature. Because the sintering temperature of CEX1-02 is higher than the upper limit of the sintering temperature according to the present invention, the crystallite size of CEX1-02 (50 nm) is larger than optimal.

[0082] The powdered NMC materials of Example 2 and Comparative Example 2 (EX2 and CEX2) have the same general formula Li (1+a) (Ni 1 / 3 Mn 1 / 3 Co 1 / 3 ) (1-a) O2 [where a=0.050]. In Example 1, the Ni content x is much lower, so a higher sintering temperature is required to have the same crystallite size according to the present invention. The sintering time of CEX2 is less than 0.30 hours, so the crystallite size of CEX2 is smaller than the optimum value.

[0083] [Table 1]

Claims

1. 1. A method for preparing a cathode material for a lithium ion battery, comprising: Step (i) in a furnace from a temperature of less than 200° C. to a temperature T ｓ heating a mixed metal compound pM comprising lithium, nickel and at least one metal selected from cobalt, manganese and aluminum at a heating rate of more than 10°C / min to a temperature of 10°C / min, or heating a first mixture M1 comprising A1: a mixed metal compound P1 comprising nickel and at least one metal selected from cobalt, manganese and aluminum, and B1: a lithium compound L1; - step (ii) the mixed metal compound pM or the first mixture is heated to the temperature T ｓ Time t for 0.3 to 2.0 hours ｓ to obtain a heat-treated mixed metal compound M, ｓ and the time t ｓ is expressed by the formula: 1140 + 50 × log １０ (6 / t ｓ ) -580 x x ≦ T ｓ ≦1200 [wherein x is the atomic ratio of nickel to the total amount of nickel, cobalt, manganese, and aluminum in the mixed metal compound pM or the first mixture, 0.60≦x≦0.95, and 300° C.·hours≦T ｓ ×t ｓ <1600°C-hours], - step (iii) cooling the heat-treated mixed metal compound M obtained in step (ii) at an average cooling rate of between 4°C / min and 20°C / min, the total time for steps (i) and (ii) is 0.3 hours to 3.0 hours; The positive electrode active material powder conforms to the general formula Li (a+1) (NixMnyCozMec) (1-a) O 2 , where Me consists of at least one element from the group consisting of Al, Mg, Ti, Zr, W, Nb, B, and Sr, and −0.01≦a≦0.05, 0.60≦x≦0.95, 0≦y≦0.20, 0<z≦0.20, 0≦c≦0.05, and x+y+z+c=1.

2. 2. The method of claim 1, wherein the total time for steps (i) and (ii) is from 1 hour to 3 hours.

3. 3. The method according to claim 1 or 2, wherein the total time for steps (i) and (ii) is from 1 hour to 2 hours.

4. 300°C / time≦T ｓ ×t ｓ 4. The method of claim 1, wherein the heating time is ≦1000° C. / hour.

5. The time t for heating the mixed metal compound pM in step (i) Ｈ The method according to claim 1 or 2, wherein the heating time is from 0.5 hours to 2 hours.

6. The method according to any one of claims 1 to 5, wherein the mixed metal compound pM is obtained by heating a second mixture M2 comprising A2: a mixed metal compound P2 comprising nickel and at least one metal selected from cobalt, manganese and aluminum, and B2: a lithium compound L2.

7. The method according to any one of claims 1 to 6, wherein the heat-treated mixed metal compound M obtained in step (ii) is discharged from the furnace before step (iii).

8. 8. The method according to any one of claims 1 to 7, wherein the mixed metal compound pM is provided in step (i) as a powder having a crystallinity of less than 70 nm.

9. T ｓ ≦1745+50×log １０ (6 / t ｓ 9. The method according to claim 1, wherein the x is 0.5 or 1.

0.

10. 1170 + 50 × log １０ (6 / t ｓ 10. The method according to claim 1, wherein x≦Ts.

11. The method according to any one of claims 1 to 10 for preparing a positive electrode active material powder having a crystallite size of 34 nm to 46 nm.

12. A method for producing a secondary lithium ion battery comprising a positive electrode active material obtained by the method according to any one of claims 1 to 11.

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