Positive Electrode Active Material for Lithium Secondary Battery and Method for Preparing the Same

Abstract

The present invention relates to a positive electrode active material, a method for preparing the same, and a lithium secondary battery including the positive electrode active material. The positive electrode active material is of the formula Li 1+a1 Ni x1 Co y1 M z1 M’ 1-x1-y1-z1 O2 and agglomerated particles represented by the formula Li 1+a2 Ni x2 Co y2 M z2 M’ 1-x2-y2-z2 O2 and single crystal particles, where M is one or two elements selected from Mn and Al, M’ is one or more elements selected from B, F, Mg, Si, P, Ca, Ti, V, Cr, Fe, Ga, Sr, Y, Zr, Nb, Mo, Sn, Ba, La, Ce, and W, -0.03 ≦ a1 ≦ 0.20, 0.30 ≦ x1 ≦ 0.99, 0 ≦ y1 ≦ 0.30, 0 ≦ z1 ≦ 0.30, 0 ≦ 1 - x1 - y1 - z1 ≦ 0.10, -0.03 ≦ a2 ≦ 0.20, 0.31 ≦ x2 ≦ 1.00, 0 ≦ y2 ≦ 0.30, 0 ≦ z2 ≦ 0.30, 0 ≦ 1 - x2 - y2 - z2 ≦ 0.10, provided that 0

Description

Technical Field

[0001] The present invention relates to a positive electrode (anode) active material, a method for preparing the same, and a lithium secondary battery including the positive electrode active material.

Background Art

[0002] In recent years, with the deterioration of the energy and environmental crisis, natural energy sources such as wind power and solar power generation have been actively developed. However, these energy sources are inefficient and cannot compensate for the lack of large-scale energy resource utilization. Lithium-ion batteries are green secondary batteries with significant advantages such as high operating voltage, high energy density, good cycle life, low self-discharge, and no memory effect, and their development has been rapidly advanced.

[0003] In the field of lithium-ion batteries, ternary layer materials (nickel-cobalt-manganese, NCM) have great potential for development due to their high specific capacity and stability. However, as the nickel content in NCM increases, the stability of the material gradually decreases. During the charging process, the reaction between the highly active Ni 4+ generated and the electrolyte generates a NiO-like rock salt phase, which causes serious damage to the structure of the layered material, leads to the collapse of the positive electrode structure, and further induces the dissolution of transition metal ions, phase transition, and precipitation of lattice oxygen. Currently, the conventional aggregated NCM "secondary particles" typically consist of a large number of nanoscale "primary particles". During the charging and discharging processes, microcracks are formed in the secondary particles due to changes in the lattice parameters. The formed microcracks expose new interfaces inside the secondary particles, further accelerating the deterioration of the properties. It is known that the higher the nickel content, the more significant the destructive effect of the cracks. That is, the main cause of the decrease in the cycle life of NCM, especially high-nickel NCM, is microcracks, which simultaneously reduce the thermal stability, structural stability, and cycle stability of the positive electrode material.

[0004] Currently, in order to minimize the generation of microcracks in high-nickel agglomerated materials, in most studies, techniques such as coating and doping are applied to improve the strength of large particles. However, it is very difficult to increase the compression density during battery manufacturing. When the nickel content is the same, the capacity of small agglomerated particles is higher than that of large particles, but characteristics such as cycle life and gas generation deteriorate. The morphology of small single-crystal particles is different from that of small agglomerated particles, and their particle strength is relatively high. However, characteristics such as capacity and gas generation hardly reach the desired levels, and there are also major problems in sorting and pulping.

[0005] Chinese Patent Publication No. 109962221 uses a single-crystal-like material doped with aggregates, and its main components are a lithium manganese iron phosphate material in a single-crystal form and a multi-element material in an aggregated form. The multi-element material and lithium manganese iron phosphate belong to two different cathode materials with different test voltages and usage ranges. Therefore, if the two materials are forcibly mixed, the advantages of each will inevitably be sacrificed, resulting in a waste of resources. As disclosed in Chinese Patent Publication No. 107154491, two materials with different conductivities are mixed, and the capacities of the two materials are considered respectively, but the influence of the Ni content of the two different materials on the final product is not considered. Since the two materials are mixed, the allowable range of particle size is relatively wide, and the influence on the final product can hardly be judged.

Summary of the Invention

[0006] The object of the present invention is to overcome the drawbacks of the prior art and effectively improve the defects of compound products such as low capacity and poor cycle life. The present invention effectively improves the capacity of the cathode active material by making the Ni content in small particles higher than that in large particles. Furthermore, by preparing large agglomerated particles and small single-crystal particles and controlling their different surface characteristics, the generation of microcracks in large agglomerated particles can be effectively suppressed, and the stability of the cathode active material during long-term cycling can be improved. The cathode active material provided by the present invention has characteristics such as high compression density, high capacity, and high stability.

[0007] In one aspect, the present invention provides a cathode active material for a lithium secondary battery, and the cathode active material includes agglomerated particles represented by Formula A1 and single crystal particles represented by Formula A2, A1: Li 1+a1 Ni x1 Co y1 M z1 M’ 1-x1-y1-z1 O2 A2: Li 1+a2 Ni x2 Co y2 M z2 M’ 1-x2-y2-z2 O2

[0008] Here, M is one or two elements selected from Mn and Al, M’ is one or more elements selected from B, F, Mg, Si, P, Ca, Ti, V, Cr, Fe, Ga, Sr, Y, Zr, Nb, Mo, Sn, Ba, La, Ce, and W, -0.03 ≦ a1 ≦ 0.20, 0.30 ≦ x1 ≦ 0.99, 0 ≦ y1 ≦ 0.30, 0 ≦ z1 ≦ 0.30, 0 ≦ 1 - x1 - y1 - z1 ≦ 0.10, -0.03 ≦ a2 ≦ 0.20, 0.31 ≦ x2 ≦ 1.00, 0 ≦ y2 ≦ 0.30, 0 ≦ z2 ≦ 0.30, 0 ≦ 1 - x2 - y2 - z2 ≦ 0.10, provided that 0 < x2 - x1 ≦ 0.5.

[0009] In another aspect, the present invention also provides a method for preparing a cathode active material including the following steps: i) Separately preparing an agglomerated particle precursor represented by Formula A3 and a single crystal particle precursor represented by Formula A4 by a liquid phase coprecipitation method, A3: Ni x1 Co y1 M z1 M’ 1-x1-y1-z1 (OH)2 A4: Ni x2 Co y2 M z2 M’ 1-x2-y2-z2 (OH)2

[0010] Here, M is one or two elements selected from Mn and Al, M' is one or more elements selected from B, F, Mg, Si, P, Ca, Ti, V, Cr, Fe, Ga, Sr, Y, Zr, Nb, Mo, Sn, Ba, La, Ce, and W, 0.30 ≦ x1 ≦ 0.99, 0 ≦ y1 ≦ 0.30, 0 ≦ z1 ≦ 0.30, 0 ≦ 1 - x1 - y1 - z1 ≦ 0.10, 0.31 ≦ x2 ≦ 1.00, 0 ≦ y2 ≦ 0.30, 0 ≦ z2 ≦ 0.30, 0 ≦ 1 - x2 - y2 - z2 ≦ 0.10, provided that 0 < x2 - x1 ≦ 0.5,

[0011] ii) A lithium source is mixed with the agglomerated particle precursor at a molar ratio r1, and M' is optionally incorporated as a doping element, where 0.97 ≦ r1 ≦ 1.20. Then, primary sintering is performed in a sintering atmosphere of air or oxygen at a sintering temperature T1, where 600°C ≦ T1 ≦ 1000°C. Then, after pulverization, agglomerated particles are obtained.

[0012] iii) A lithium source is mixed with the single crystal particle precursor at a molar ratio r2, and M' is optionally incorporated as a doping element, where 0.97 ≦ r2 ≦ 1.20. Then, primary sintering is performed in a sintering atmosphere of air or oxygen at a sintering temperature T2, where 650°C ≦ T2 ≦ 1050°C. Then, after pulverization, single crystal particles are obtained, and iv) The agglomerated particles of step ii) are mixed with the single crystal particles of step iii) to obtain a positive electrode active material.

[0013] In yet another aspect, the present invention also provides a lithium secondary battery including the positive electrode active material according to the present invention, or the positive electrode active material prepared by the preparation method according to the present invention.

Brief Description of the Drawings

[0014]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Mode for Carrying Out the Invention

[0015] Unless otherwise stated, all publications, patent applications, patents, and other references mentioned in this specification are hereby incorporated by reference in their entirety for all purposes as if they were all expressly set forth.

[0016] Unless otherwise defined, all technical and scientific terms used in this specification have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. In case of conflict, the present specification, including definitions, will control.

[0017] When a quantity, concentration, or other value or parameter is given as a range, preferred range, or a series of preferred upper and lower limits, all ranges formed by combinations of any upper limit or preferred value within the range and any lower limit or preferred value within the range or preferred values within the range are specifically disclosed, whether or not the ranges are separately disclosed. When a numerical range is recited, it includes its endpoints and all integers and fractions within the range unless otherwise indicated.

[0018] In one aspect, the present invention provides a positive electrode active material for a lithium secondary battery, and the positive electrode active material includes agglomerated particles represented by Formula A1 and single crystal particles represented by Formula A2, A1: Li 1+a1 Ni x1 Co y1 Mz1 M’ 1-x1-y1-z1 O2 A2: Li 1+a2 Ni x2 Co y2 M z2 M’ 1-x2-y2-z2 O2

[0019] Here, M is one or two elements selected from Mn and Al, M’ is one or more elements selected from B, F, Mg, Si, P, Ca, Ti, V, Cr, Fe, Ga, Sr, Y, Zr, Nb, Mo, Sn, Ba, La, Ce, and W,

[0020] -0.03 ≦ a1 ≦ 0.20, preferably -0.01 ≦ a1 ≦ 0.14, more preferably 0 ≦ a1 ≦ 0.10, and particularly preferably 0.01 ≦ a1 ≦ 0.08, 0.30 ≦ x1 ≦ 0.99, preferably 0.57 ≦ x1 ≦ 0.99, more preferably 0.72 ≦ x1 ≦ 0.99, and particularly preferably 0.80 ≦ x1 ≦ 0.99, 0 ≦ y1 ≦ 0.30, preferably 0 ≦ y1 ≦ 0.21, more preferably 0 ≦ y1 ≦ 0.15, and particularly preferably 0 ≦ y1 ≦ 0.10, 0 ≦ z1 ≦ 0.30, preferably 0 ≦ z1 ≦ 0.18, more preferably 0 ≦ z1 ≦ 0.11, and particularly preferably 0 ≦ z1 ≦ 0.06, 0 ≦ 1 - x1 - y1 - z1 ≦ 0.10, preferably 0 ≦ 1 - x1 - y1 - z1 ≦ 0.08, more preferably 0 ≦ 1 - x1 - y1 - z1 ≦ 0.05, and particularly preferably 0 ≦ 1 - x1 - y1 - z1 ≦ 0.03,

[0021] -0.03 ≦ a2 ≦ 0.20, preferably -0.02 ≦ a2 ≦ 0.16, more preferably -0.01 ≦ a2 ≦ 0.14, and particularly preferably 0 ≦ a2 ≦ 0.08, 0.31 ≦ x2 ≦ 1.00, preferably 0.59 ≦ x2 ≦ 0.995, more preferably 0.75 ≦ x2 ≦ 0.995, and particularly preferably 0.81 ≦ x2 ≦ 0.995, 0 ≤ y2 ≤ 0.30, preferably 0 ≤ y2 ≤ 0.21, more preferably 0 ≤ y2 ≤ 0.15, and particularly preferably 0 ≤ y2 ≤ 0.10, and 0 ≤ z2 ≤ 0.30, preferably 0 ≤ z2 ≤ 0.18, more preferably 0 ≤ z2 ≤ 0.11, and particularly preferably 0 ≤ z2 ≤ 0.08, and 0 ≤ 1 - x2 - y2 - z2 ≤ 0.10, preferably 0 ≤ 1 - x2 - y2 - z2 ≤ 0.08, more preferably 0 ≤ 1 - x2 - y2 - z2 ≤ 0.05, and particularly preferably 0 ≤ 1 - x2 - y2 - z2 ≤ 0.03, and

[0022] provided that 0 < x2 - x1 ≤ 0.5, preferably 0.01 ≤ x2 - x1 ≤ 0.27, more preferably 0.01 ≤ x2 - x1 ≤ 0.2, still more preferably 0.015 ≤ x2 - x1 ≤ 0.20, and particularly preferably 0.02 ≤ x2 - x1 ≤ 0.15.

[0023] According to one aspect of the positive electrode active material of the present invention, a2 > a1, preferably 0.01 ≤ a2 - a1 ≤ 0.20, more preferably 0.01 ≤ a2 - a1 ≤ 0.12, and particularly preferably 0.01 ≤ a2 - a1 ≤ 0.07, and most preferably 0.01 ≤ a2 - a1 ≤ 0.04.

[0024] According to another aspect of the positive electrode active material of the present invention, the aggregated particles have a particle size D of 6 to 30 μm, preferably 8 to 25 μm, more preferably 9 to 20 μm, and particularly preferably 10 to 18 μm 50 and

[0025] According to another aspect of the positive electrode active material of the present invention, the single crystal particles have a particle size D of 0.1 to 10 μm, preferably 0.5 to 8.0 μm, more preferably 1.0 to 6.0 μm, and particularly preferably 1.5 to 4.5 μm 50 and

[0026] According to another aspect of the positive electrode active material of the present invention, based on the weight of the positive electrode active material, the agglomerated particles are present in an amount of 20 to 90%, preferably 45 to 85%, more preferably 50 to 80%, and particularly preferably 60 to 80%, and the single crystal particles are present in an amount of 10 to 80%, preferably 10 to 70%, more preferably 15 to 60%, and particularly preferably 20 to 40%.

[0027] According to another aspect of the positive electrode active material of the present invention, the agglomerated particles have a coating layer containing at least one coating element selected from the group consisting of B, F, Mg, Al, Si, P, Ca, Ti, V, Cr, Fe, Ga, Sr, Y, Zr, Nb, Mo, Sn, Ba, La, Ce, and W, where the coating element is present in an amount of 0.1 to 2 mol%, preferably about 1 mol%, based on the agglomerated particles, and / or the single crystal particles have a coating layer containing at least one coating element selected from the group consisting of B, F, Mg, Al, Si, P, Ca, Ti, V, Cr, Fe, Ga, Sr, Y, Zr, Nb, Mo, Sn, Ba, La, Ce, and W, where the coating element is present in an amount of 0.1 to 2 mol%, preferably about 1 mol%, based on the single crystal particles, provided that the coating element contained in the coating layer of the agglomerated particles is different from the coating element contained in the coating layer of the single crystal particles.

[0028] According to another aspect of the positive electrode active material of the present invention, the BET specific surface area of the positive electrode active material before and after firing at 600 °C for 8 hours in an air atmosphere before and BET after satisfy the following formula: |BET after - BET before | / BET before ≦ 50%, preferably, |BET after - BET before | / BET before ≦ 30%.

[0029] The present invention uses an optimal blend ratio of single crystal particles with rounded surfaces and agglomerated particles with high particle strength, resulting in a controlled finished material that exhibits a stable crystal structure, thereby suppressing changes in the surface porosity of the finished product during further sintering.

[0030] According to another embodiment of the positive electrode active material of the present invention, the specific surface area BET of the aggregated particles before and after firing at 600° C. for 8 hours in an air atmosphere is before and BET after satisfies the following equation: (BET after -BET before ) / BET before ≧15%, Preferably, 40%≧(BET after -BET before ) / BET before ≧20%.

[0031] Agglomerated particles consist of many nanoscale particles. To maintain good cycle performance, there should be no excessive voids on the surface of the nanoparticles, and the BET of the material must be controlled within a certain range. Under normal circumstances, the BET of the material will further decrease after sintering at high temperatures. However, according to the present invention, the crystallinity and orientation of the nanograins on the surface of the material can be controlled to achieve in situ (in situ) By combining this with an in-situ melt surface treatment, good surface / interface protection effects can be achieved. Furthermore, unexpectedly, it was found that the BET of the material surface did not decrease but rather increased. The inventors further found that mixing agglomerated particles with such surface BET properties with single-crystal particles resulted in a positive electrode material that exhibited relatively excellent compression resistance, better discharge capacity, and cycle performance.

[0032] According to another embodiment of the positive electrode active material of the present invention, the specific surface area BET of the single crystal particles before and after sintering at 600°C for 8 hours in an air atmosphere is before and BET after satisfies the following equation: (BET before -BET after ) / BET before ≦15%, Preferably, 0 ≦ (BET before - BET after ) / BET before ≦ 10%.

[0033] The single crystal particles of the present invention have characteristics such as good crystallinity and a rounded surface, and are therefore structurally relatively stable. During high-temperature sintering, the material does not collapse or shrink significantly, and the change in BET is small compared to the BET of the unsintered material.

[0034] According to another aspect of the positive electrode active material of the present invention, the positive electrode active material does not contain a nickel-free active material such as lithium iron manganese phosphate. According to another aspect of the positive electrode active material of the present invention, the positive electrode active material consists of agglomerated particles represented by formula A1 and single crystal particles represented by formula A2.

[0035] In another aspect, the present invention further provides a method for preparing a positive electrode active material, including the following steps: i) separately preparing an agglomerated particle precursor represented by formula A3 and a single crystal particle precursor represented by formula A4 by a liquid phase coprecipitation method, A3: Ni x1 Co y1 M z1 M’ 1-x1-y1-z1 (OH)2 A4: Ni x2 Co y2 M z2 M’ 1-x2-y2-z2 (OH)2

[0036] Here, M is one or two elements selected from Mn and Al, M’ is one or more elements selected from B, F, Mg, Si, P, Ca, Ti, V, Cr, Fe, Ga, Sr, Y, Zr, Nb, Mo, Sn, Ba, La, Ce, and W,

[0037] 0.30 ≦ x1 ≦ 0.99, preferably 0.57 ≦ x1 ≦ 0.99, more preferably 0.72 ≦ x1 ≦ 0.99, and particularly preferably 0.80 ≦ x1 ≦ 0.99, 0 ≤ y1 ≤ 0.30, preferably 0 ≤ y1 ≤ 0.21, more preferably 0 ≤ y1 ≤ 0.15, and particularly preferably 0 ≤ y1 ≤ 0.10, and 0 ≤ z1 ≤ 0.30, preferably 0 ≤ z1 ≤ 0.18, more preferably 0 ≤ z1 ≤ 0.11, and particularly preferably 0 ≤ z1 ≤ 0.06, and

[0038] 0 ≤ 1 - x1 - y1 - z1 ≤ 0.10, preferably 0 ≤ 1 - x1 - y1 - z1 ≤ 0.08, more preferably 0 ≤ 1 - x1 - y1 - z1 ≤ 0.05, and particularly preferably 0 ≤ 1 - x1 - y1 - z1 ≤ 0.03, and

[0039] 0.31 ≤ x2 ≤ 1.00, preferably 0.59 ≤ x2 ≤ 0.995, more preferably 0.75 ≤ x2 ≤ 0.995, and particularly preferably 0.81 ≤ x2 ≤ 0.995, and 0 ≤ y2 ≤ 0.30, preferably 0 ≤ y2 ≤ 0.21, more preferably 0 ≤ y2 ≤ 0.15, and particularly preferably 0 ≤ y2 ≤ 0.10, and 0 ≤ z2 ≤ 0.30, preferably 0 ≤ z2 ≤ 0.18, more preferably 0 ≤ z2 ≤ 0.11, and particularly preferably 0 ≤ z2 ≤ 0.08, and

[0040] 0 ≤ 1 - x2 - y2 - z2 ≤ 0.10, preferably 0 ≤ 1 - x2 - y2 - z2 ≤ 0.08, more preferably 0 ≤ 1 - x2 - y2 - z2 ≤ 0.05, and particularly preferably 0 ≤ 1 - x2 - y2 - z2 ≤ 0.03, and

[0041] However, 0 < x2 - x1 ≤ 0.5, preferably 0.01 ≤ x2 - x1 ≤ 0.27, more preferably 0.01 ≤ x2 - x1 ≤ 0.20, still more preferably 0.015 ≤ x2 - x1 ≤ 0.20, and particularly preferably 0.02 ≤ x2 - x1 ≤ 0.15, and

[0042] ii) Mix the lithium source with the agglomerated particle precursor at a molar ratio r1, optionally incorporating M′ as a doping element, where 0.97 ≤ r1 ≤ 1.20, preferably 0.99 ≤ r1 ≤ 1.14, more preferably 1.00 ≤ r1 ≤ 1.10, and particularly preferably 1.01 ≤ r1 ≤ 1.08. Then, perform primary sintering in a sintering atmosphere of air or oxygen, preferably oxygen, at a sintering temperature T1, where 600°C ≤ T1 ≤ 1000°C, preferably 675°C ≤ T1 ≤ 875°C, more preferably 690°C ≤ T1 ≤ 800°C, and particularly preferably 690°C ≤ T1 ≤ 780°C. Then, obtain agglomerated particles through pulverization.

[0043] iii) Mix the lithium source with the single crystal particle precursor at a molar ratio r2, optionally incorporating M′ as a doping element, where 0.97 ≤ r2 ≤ 1.20, preferably 0.98 ≤ r2 ≤ 1.16, more preferably 0.99 ≤ r2 ≤ 1.14, and particularly preferably 1.00 ≤ r2 ≤ 1.08. Then, perform primary sintering at a sintering temperature T2 in a sintering atmosphere of air or oxygen, preferably oxygen, where 650°C ≤ T2 ≤ 1050°C, preferably 730°C ≤ T2 ≤ 930°C, more preferably 750°C ≤ T2 ≤ 930°C, and particularly preferably 750°C ≤ T2 ≤ 900°C. Then, obtain single crystal particles by pulverization, and

[0044] iv) Mix the agglomerated particles of step ii) with the single crystal particles of step iii) to obtain a cathode active material.

[0045] According to another aspect of the method according to the present invention, r2 > r1, preferably 0.01 ≤ r2 - r1 ≤ 0.20, more preferably 0.01 ≤ r2 - r1 ≤ 0.12, particularly preferably 0.01 ≤ r2 - r1 ≤ 0.07, and especially preferably 0.01 ≤ r2 - r1 ≤ 0.04.

[0046] According to another aspect of the method according to the present invention, the agglomerated particle precursor has a particle size D of 6.5 to 30.5 μm, preferably 8.5 to 25.5 μm, more preferably 9.5 to 20.5 μm, and particularly preferably 10.5 to 18.5 μm. 50It has. The aggregated particles have a particle size D of 6 to 30 μm, preferably 8 to 25 μm, more preferably 9 to 20 μm, and particularly preferably 10 to 18 μm. 50 It has.

[0047] According to another aspect of the method according to the present invention, the single crystal particle precursor has a particle size D of 0.1 to 30.5 μm, preferably 1.0 to 17.3 μm, more preferably 1.0 to 9.3 μm, and particularly preferably 1.0 to 6.0 μm. 50 It has. The single crystal particles have a particle size D of 0.1 to 10 μm, preferably 0.5 to 8.0 μm, more preferably 1.0 to 6.0 μm, and particularly preferably 1.5 to 4.5 μm. 50 It has.

[0048] According to another aspect of the method according to the present invention, based on the weight of the positive electrode active material, the aggregated particles are present in an amount of 20 to 90%, preferably 45 to 85%, more preferably 50 to 80%, and particularly preferably 60 to 80%, and the single crystal particles are present in an amount of 10 to 80%, preferably 10 to 70%, more preferably 15 to 60%, and particularly preferably 20 to 40%.

[0049] According to another aspect of the method according to the present invention, before step iv), the aggregated particles are mixed with a coating precursor containing at least one coating element selected from the group consisting of B, F, Mg, Al, Si, P, Ca, Ti, V, Cr, Fe, Ga, Sr, Y, Zr, Nb, Mo, Sn, Ba, La, Ce, and W, and then secondary sintering is performed at a sintering temperature T3 in a sintering atmosphere of air or oxygen, preferably oxygen, to obtain secondary sintered aggregated particles, where 250 °C ≤ T3 ≤ 800 °C, preferably 250 °C ≤ T3 ≤ 600 °C, more preferably 250 °C ≤ T3 ≤ 480 °C, and particularly preferably 250 °C ≤ T3 ≤ 450 °C, and the coating element is present in an amount of 0.1 to 2 mol%, preferably about 1 mol%, based on the aggregated particles; and / or, in addition, the single crystal particles are mixed with a coating precursor containing at least one coating element selected from the group consisting of B, F, Mg, Al, Si, P, Ca, Ti, V, Cr, Fe, Ga, Sr, Y, Zr, Nb, Mo, Sn, Ba, La, Ce, and W, and then secondary sintering is performed at a sintering temperature T4 in a sintering atmosphere of air or oxygen, preferably oxygen, to obtain secondary sintered single crystal particles, where 300 °C ≤ T4 ≤ 900 °C, preferably 460 °C ≤ T4 ≤ 800 °C, more preferably 550 °C ≤ T4 ≤ 750 °C, and particularly preferably 600 °C ≤ T4 ≤ 750 °C, and the coating element is present in an amount of 0.1 to 2 mol%, preferably about 1 mol%, based on the single crystal particles; provided that the coating element contained in the coating precursor of the aggregated particles is different from the coating element contained in the coating precursor of the single crystal particles.

[0050] In yet another aspect, the present invention further provides a lithium secondary battery comprising the positive electrode active material according to the present invention or the positive electrode active material prepared by the preparation method according to the present invention.

Examples

[0051] Example 1 First, aggregated positive electrode precursor (10.5 μm) having a composition of Ni 0.83 Co 0.11 Mn 0.06 (OH)2 and Ni 0.86 Co 0.08 Mn 0.06Single crystal cathode precursors (4 μm) with the composition of (OH)2 were separately prepared by the liquid phase coprecipitation method.

[0052] LiOH and Ni 0.83 Co 0.11 Mn 0.06 (OH)2 were mixed at a molar ratio of 1.08. For the mixed material, the first sintering was carried out in an oxygen atmosphere at a sintering temperature of 750 °C. The sintered material was pulverized, boric acid containing 1 mol% of B was added to the pulverized material, and the second sintering was carried out at a sintering temperature of 400 °C to obtain an aggregated particle material with D shown in Figure 1 50 having a size of 10.0 μm. When the aggregated material was treated at 600 °C for 8 hours, it had an increased BET with a change rate of 35%.

[0053] LiOH and Ni 0.86 Co 0.08 Mn 0.06 (OH)2 were mixed at a molar ratio of 1.12. For the mixed material, the first sintering was carried out in an oxygen atmosphere at a sintering temperature of 812 °C. The sintered material was pulverized, Al2O3 containing 1 mol% of Al was added to the pulverized material, and the second sintering was carried out at a sintering temperature of 620 °C to obtain a single crystal particle material with D shown in Figure 2 50 having a size of 3.5 μm. When the single crystal material was treated at 600 °C for 8 hours, it had a decreased BET with a change rate of 2%.

[0054] The above-mentioned large aggregated particles and small single crystal particles were mixed at a mass ratio of 7:3 to obtain a cathode active material for a lithium secondary battery shown in Figure 3. When the cathode active material was treated at 600 °C for 8 hours, it had an increased BET with a change rate of 24%.

[0055] Example 2 First, aggregated cathode precursors (10.5 μm) with the composition of Ni 0.83 Co 0.11 Mn 0.06 (OH)2 and single crystal cathode precursors (4 μm) with the composition of Ni 0.86 Co 0.08 Mn 0.06 (OH)2 were separately prepared by the liquid phase coprecipitation method.

[0056] LiOH and Ni 0.83 Co 0.11 Mn 0.06 (OH)2 were mixed at a molar ratio of 1.06. For the mixed material, the first sintering was carried out in an oxygen atmosphere at a sintering temperature of 745 °C. The sintered material was pulverized, boric acid containing 0.8 mol% of B was added to the pulverized material, and the second sintering was carried out at a sintering temperature of 380 °C to obtain an aggregated particle material with D 50 having a size of 10.0 μm. When the aggregated material was treated at 600 °C for 8 hours, it had an increased BET with a change rate of 24%.

[0057] LiOH and Ni 0.86 Co 0.08 Mn 0.06 (OH)2 were mixed at a molar ratio of 1.12. For the mixed material, the first sintering was carried out in an oxygen atmosphere at a sintering temperature of 812 °C. The sintered material was pulverized, Al2O3 containing 1.2 mol% of Al was added to the pulverized material, and the second sintering was carried out at a sintering temperature of 610 °C to obtain a small single crystal particle material with D 50 having a size of 3.5 μm. When the single crystal material was treated at 600 °C for 8 hours, it had a decreased BET with a change rate of 3%.

[0058] The above-mentioned large aggregated particles and small single crystal particles were mixed at a mass ratio of 8:2 to obtain a cathode active material for a lithium secondary battery. When the cathode active material was treated at 600 °C for 8 hours, it had an increased BET with a change rate of 19%.

[0059] Example 3 First, an aggregated cathode precursor (10.5 μm) having a composition of Ni 0.86 Co 0.11 Mn 0.03 (OH)2 and a single crystal cathode precursor (4 μm) having a composition of Ni 0.88 Co 0.08 Mn 0.04 (OH)2 were separately prepared by the liquid phase co-precipitation method.

[0060] LiOH and Ni 0.86 Co 0.11 Mn 0.03(OH)2 was mixed at a molar ratio of 1.06. For the mixed material, the first sintering was carried out in an oxygen atmosphere at a sintering temperature of 725 °C. The sintered material was pulverized, boric acid containing 0.8 mol% of B was added to the pulverized material, and the second sintering was carried out at a sintering temperature of 380 °C to obtain an aggregated particle material with D 50 having a size of 10.0 μm. When the aggregated material was treated at 600 °C for 8 hours, it had an increased BET with a change rate of 26%.

[0061] LiOH and Ni 0.88 Co 0.08 Mn 0.04 (OH)2 was mixed at a molar ratio of 1.11. For the mixed material, the first sintering was carried out in an oxygen atmosphere at a sintering temperature of 805 °C. The sintered material was pulverized, Al2O3 containing 1.0 mol% of Al was added to the pulverized material, and the second sintering was carried out at a sintering temperature of 610 °C to obtain a single crystal particle material with D 50 having a size of 3.5 μm. When the single crystal material was treated at 600 °C for 8 hours, it had a decreased BET with a change rate of 2%.

[0062] The above-mentioned large aggregated particles and small single crystal particles were mixed at a mass ratio of 7:3 to obtain a cathode active material for a lithium secondary battery. When the cathode active material was treated at 600 °C for 8 hours, it had an increased BET with a change rate of 20%.

[0063] Example 4 First, an aggregated cathode precursor (10.5 μm) having the composition of Ni 0.86 Co 0.11 Mn 0.03 (OH)2 and a single crystal cathode precursor (4 μm) having the composition of Ni 0.88 Co 0.08 Mn 0.04 (OH)2 were separately prepared by the liquid phase coprecipitation method.

[0064] LiOH and Ni 0.86 Co 0.11 Mn 0.03(OH)2 was mixed at a molar ratio of 1.06. For the mixed material, the first sintering was carried out in an oxygen atmosphere at a sintering temperature of 685 °C. The sintered material was pulverized, boric acid containing 0.8 mol% of B was added to the pulverized material, and the second sintering was carried out at a sintering temperature of 380 °C to obtain an aggregated particle material with D 50 having an aggregate particle size of 10.0 μm. When the aggregated material was treated at 600 °C for 8 hours, it had an increased BET with a change rate of 26%.

[0065] LiOH and Ni 0.88 Co 0.08 Mn 0.04 (OH)2 was mixed at a molar ratio of 1.11. For the mixed material, the first sintering was carried out in an oxygen atmosphere at a sintering temperature of 805 °C. The sintered material was pulverized, Al2O3 containing 1.0 mol% of Al was added to the pulverized material, and the second sintering was carried out at a sintering temperature of 610 °C to obtain a single crystal particle material with D 50 having a size of 3.5 μm. When the single crystal material was treated at 600 °C for 8 hours, it had a decreased BET with a change rate of 2%.

[0066] The above-mentioned large aggregated particles and small single crystal particles were mixed at a mass ratio of 3:7 to obtain a cathode active material for a lithium secondary battery. When the cathode active material was treated at 600 °C for 8 hours, it had an increased BET with a change rate of 6%.

[0067] Example 5 First, an aggregated cathode precursor (10.5 μm) having a composition of Ni 0.88 Co 0.10 Mn 0.02 (OH)2 and a single crystal cathode precursor (4 μm) having a composition of Ni 0.90 Co 0.08 Mn 0.02 (OH)2 were separately prepared by the liquid phase co-precipitation method.

[0068] LiOH and Ni 0.88 Co 0.10 Mn 0.02(OH)₂ was mixed at a molar ratio of 1.08. For the mixed material, the first sintering was carried out in an oxygen atmosphere at a sintering temperature of 780 °C. The sintered material was pulverized, boric acid containing 1 mol% of B was added to the pulverized material, and the second sintering was carried out at a sintering temperature of 400 °C, and D 50 An aggregated particle material with D being 10.0 μm in size was obtained. When the aggregated material was treated at 600 °C for 8 hours, it had a BET that increased at a change rate of 32%.

[0069] LiOH and Ni 0.90 Co 0.08 Mn 0.02 (OH)₂ was mixed at a molar ratio of 1.12. For the mixed material, the first sintering was carried out in an oxygen atmosphere at a sintering temperature of 812 °C. The sintered material was pulverized, Al₂O₃ containing 1 mol% of Al was added to the pulverized material, and the second sintering was carried out at a sintering temperature of 620 °C, and D 50 A single crystal particle material with D being 3.5 μm in size was obtained. When the single crystal material was treated at 600 °C for 8 hours, it had a BET that decreased at a change rate of 2%.

[0070] The above-mentioned large aggregated particles and small single crystal particles were mixed at a mass ratio of 7:3 to obtain a positive electrode active material for a lithium secondary battery. When the positive electrode active material was treated at 600 °C for 8 hours, it had a BET that increased at a change rate of 22%.

[0071] Example 6 First, an aggregated positive electrode precursor (10.5 μm) having a composition of Ni 0.83 Co 0.11 Mn 0.06 (OH)₂ and a single crystal positive electrode precursor (4 μm) having a composition of Ni 0.86 Co 0.08 Mn 0.06 (OH)₂ were separately prepared by a liquid phase coprecipitation method.

[0072] LiOH and Ni 0.83 Co 0.11 Mn 0.06(OH)2 was mixed at a molar ratio of 1.08. For the mixed material, the first sintering was carried out in an oxygen atmosphere at a sintering temperature of 750 °C. The sintered material was pulverized, boric acid containing 1 mol% of B was added to the pulverized material, and the second sintering was carried out at a sintering temperature of 400 °C, and D 50 an aggregated particle material with D being 10.0 μm in size was obtained. When the aggregated material was treated at 600 °C for 8 hours, it had a BET increased at a change rate of 35%.

[0073] LiOH and Ni 0.86 Co 0.08 Mn 0.06 (OH)2 was mixed at a molar ratio of 1.12. For the mixed material, the first sintering was carried out in an oxygen atmosphere at a sintering temperature of 812 °C. The sintered material was pulverized, boric acid containing 0.4 mol% of B was added to the pulverized material, and the second sintering was carried out at a sintering temperature of 400 °C, and D 50 a small single crystal particle material with D being 3.5 μm in size was obtained. When the single crystal material was treated at 600 °C for 8 hours, it had a BET increased at a change rate of 9%.

[0074] The above-mentioned large aggregated particles and small single crystal particles were mixed at a mass ratio of 7:3 to obtain a positive electrode active material for a lithium secondary battery. When the positive electrode active material was treated at 600 °C for 8 hours, it had a BET increased at a change rate of 27%.

[0075] Example 7 First, an aggregated positive electrode precursor (10.5 μm) having a composition of Ni 0.83 Co 0.11 Mn 0.06 (OH)2 and a single crystal positive electrode precursor (4 μm) having a composition of Ni 0.86 Co 0.08 Mn 0.06 (OH)2 were separately prepared by a liquid phase coprecipitation method.

[0076] LiOH and Ni 0.83 Co 0.11 Mn 0.06(OH)₂ was mixed at a molar ratio of 1.08. For the mixed material, the first sintering was carried out in an oxygen atmosphere at a sintering temperature of 750 °C. The sintered material was pulverized, boric acid containing 0.5 mol% of B was added to the pulverized material, and the second sintering was carried out at a sintering temperature of 400 °C to obtain an aggregated particle material with D 50 having an average particle size of 10.0 μm. When the aggregated material was treated at 600 °C for 8 hours, it had a BET that increased at a change rate of 11%.

[0077] LiOH and Ni 0.86 Co 0.08 Mn 0.06 (OH)₂ was mixed at a molar ratio of 1.12. For the mixed material, the first sintering was carried out in an oxygen atmosphere at a sintering temperature of 812 °C. The sintered material was pulverized, Al₂O₃ containing 1 mol% of Al was added to the pulverized material, and the second sintering was carried out at a sintering temperature of 620 °C to obtain a single crystal particle material with D 50 having an average particle size of 3.5 μm. When the single crystal material was treated at 600 °C for 8 hours, it had a BET that decreased at a change rate of 2%.

[0078] The above-mentioned large aggregated particles and small single crystal particles were mixed at a mass ratio of 7:3 to obtain a positive electrode active material for a lithium secondary battery. When the positive electrode active material was treated at 600 °C for 8 hours, it had a BET that increased at a change rate of 7%.

[0079] Example 8 First, an aggregated positive electrode precursor (10.5 μm) having a composition of Ni 0.83 Co 0.11 Mn 0.06 (OH)₂ and a single crystal positive electrode precursor (4 μm) having a composition of Ni 0.86 Co 0.08 Mn 0.06 (OH)₂ were separately prepared by a liquid phase coprecipitation method.

[0080] LiOH and Ni 0.83 Co 0.11 Mn 0.06(OH)2 was mixed at a molar ratio of 1.08. For the mixed material, the first sintering was carried out in an oxygen atmosphere at a sintering temperature of 750 °C. The sintered material was pulverized, Al2O3 containing 1 mol% of Al was added to the pulverized material, and the second sintering was carried out at a sintering temperature of 620 °C to obtain an aggregated particle material with D 50 having a size of 10.0 μm. When the aggregated material was treated at 600 °C for 8 hours, it had a BET that decreased at a change rate of 3%.

[0081] LiOH and Ni 0.86 Co 0.08 Mn 0.06 (OH)2 was mixed at a molar ratio of 1.12. For the mixed material, the first sintering was carried out in an oxygen atmosphere at a sintering temperature of 812 °C. The sintered material was pulverized, Al2O3 containing 1 mol% of Al was added to the pulverized material, and the second sintering was carried out at a sintering temperature of 620 °C to obtain a single crystal particle material with D 50 having a size of 3.5 μm. When the single crystal material was treated at 600 °C for 8 hours, it had a BET that decreased at a change rate of 2%.

[0082] The above-mentioned large aggregated particles and small single crystal particles were mixed at a mass ratio of 7:3 to obtain a positive electrode active material for a lithium secondary battery. When the positive electrode active material was treated at 600 °C for 8 hours, it had a BET that decreased at a change rate of 3%.

[0083] Example 9 First, an aggregated positive electrode precursor (10.5 μm) having a composition of Ni 0.83 Co 0.11 Mn 0.06 (OH)2 and a single crystal positive electrode precursor (4 μm) having a composition of Ni 0.86 Co 0.08 Mn 0.06 (OH)2 were separately prepared by a liquid phase coprecipitation method.

[0084] LiOH and Ni 0.83 Co 0.11 Mn 0.06(OH)₂ was mixed at a molar ratio of 1.08. For the mixed material, the first sintering was carried out in an oxygen atmosphere at a sintering temperature of 750 °C. The sintered material was pulverized, boric acid containing 0.5 mol% of B was added to the pulverized material, and the second sintering was carried out at a sintering temperature of 400 °C, and D 50 An aggregated particle material with D being 10.0 μm in size was obtained. When the aggregated material was treated at 600 °C for 8 hours, it had a BET that increased at a change rate of 11%.

[0085] LiOH and Ni 0.86 Co 0.08 Mn 0.06 (OH)₂ was mixed at a molar ratio of 1.12. For the mixed material, the first sintering was carried out in an oxygen atmosphere at a sintering temperature of 812 °C. The sintered material was pulverized, boric acid containing 0.4 mol% of B was added to the pulverized material, and the second sintering was carried out at a sintering temperature of 400 °C, and D 50 A single crystal particle material with D being 3.5 μm in size was obtained. When the single crystal material was treated at 600 °C for 8 hours, it had a BET that increased at a change rate of 9%.

[0086] The above-mentioned large aggregated particles and small single crystal particles were mixed at a mass ratio of 7:3 to obtain a cathode active material for a lithium secondary battery. When the cathode active material was treated at 600 °C for 8 hours, it had a BET that increased at a change rate of 10%.

[0087] Example 10 First, an aggregated cathode precursor (10.5 μm) having a composition of Ni 0.83 Co 0.11 Mn 0.06 (OH)₂ and a single crystal cathode precursor (4 μm) having a composition of Ni 0.84 Co 0.08 Mn 0.08 (OH)₂ were separately prepared by the liquid phase co-precipitation method.

[0088] LiOH and Ni 0.83 Co 0.11 Mn 0.06(OH)₂ was mixed at a molar ratio of 1.08. For the mixed material, the first sintering was carried out in an oxygen atmosphere at a sintering temperature of 750 °C. The sintered material was pulverized, boric acid containing 0.5 mol% of B was added to the pulverized material, and the second sintering was carried out at a sintering temperature of 400 °C to obtain an aggregated particle material with D 50 having an aggregate particle size of 10.0 μm. When the aggregated material was treated at 600 °C for 8 hours, it had a BET that increased at a change rate of 35%.

[0089] LiOH and Ni 0.84 Co 0.08 Mn 0.08 (OH)₂ was mixed at a molar ratio of 1.12. For the mixed material, the first sintering was carried out in an oxygen atmosphere at a sintering temperature of 812 °C. The sintered material was pulverized, boric acid containing 0.4 mol% of B was added to the pulverized material, and the second sintering was carried out at a sintering temperature of 400 °C to obtain a single crystal particle material with D 50 having a small single crystal particle size of 3.5 μm. When the single crystal material was treated at 600 °C for 8 hours, it had a BET that decreased at a change rate of 2%.

[0090] The above-mentioned large aggregated particles and small single crystal particles were mixed at a mass ratio of 7:3 to obtain a cathode active material for a lithium secondary battery. When the cathode active material was treated at 600 °C for 8 hours, it had a BET that increased at a change rate of 24%.

[0091] Comparative Example 1 First, an aggregated cathode precursor (10.5 μm) having the composition of Ni 0.83 Co 0.11 Mn 0.06 (OH)₂ and a single crystal cathode precursor (4 μm) having the composition of Ni 0.80 Co 0.11 Mn 0.09 (OH)₂ were separately prepared by the liquid phase co-precipitation method.

[0092] LiOH and Ni 0.83 Co 0.11 Mn 0.06(OH)2 was mixed at a molar ratio of 1.08. For the mixed material, the first sintering was carried out in an oxygen atmosphere at a sintering temperature of 750 °C. The sintered material was pulverized, boric acid containing 1 mol% of B was added to the pulverized material, and the second sintering was carried out at a sintering temperature of 400 °C to obtain an aggregated particle material with D 50 having a size of 10.0 μm. When the aggregated material was treated at 600 °C for 8 hours, it had an increased BET with a change rate of 35%.

[0093] LiOH and Ni 0.80 Co 0.11 Mn 0.09 (OH)2 was mixed at a molar ratio of 1.12. For the mixed material, the first sintering was carried out in an oxygen atmosphere at a sintering temperature of 820 °C. The sintered material was pulverized, Al2O3 containing 1 mol% of Al was added to the pulverized material, and the second sintering was carried out at a sintering temperature of 620 °C to obtain a single crystal particle material with D 50 having a size of 3.5 μm. When the single crystal material was treated at 600 °C for 8 hours, it had a decreased BET with a change rate of 2%.

[0094] The above-mentioned large aggregated particles and small single crystal particles were mixed at a mass ratio of 7:3 to obtain a positive electrode active material for a lithium secondary battery. When the positive electrode active material was treated at 600 °C for 8 hours, the BET increased with a change rate of 25%.

[0095] Comparative Example 2 First, an aggregated positive electrode precursor (10.5 μm) having a composition of Ni 0.83 Co 0.11 Mn 0.06 (OH)2 and a single crystal positive electrode precursor (4 μm) having a composition of Ni 0.83 Co 0.11 Mn 0.06 (OH)2 were separately prepared by the liquid phase coprecipitation method.

[0096] LiOH and Ni 0.83 Co 0.11 Mn 0.06(OH)2 was mixed at a molar ratio of 1.08. For the mixed material, the first sintering was carried out in an oxygen atmosphere at a sintering temperature of 750 °C. The sintered material was pulverized, boric acid containing 1 mol% of B was added to the pulverized material, and the second sintering was carried out at a sintering temperature of 400 °C to obtain an aggregated particle material with D 50 having an average particle size of 10.0 μm. When the aggregated material was treated at 600 °C for 8 hours, it had an increased BET with a change rate of 35%.

[0097] LiOH and Ni 0.83 Co 0.11 Mn 0.06 (OH)2 was mixed at a molar ratio of 1.12. For the mixed material, the first sintering was carried out in an oxygen atmosphere at a sintering temperature of 816 °C. The sintered material was pulverized, Al2O3 containing 1 mol% of Al was added to the pulverized material, and the second sintering was carried out at a sintering temperature of 620 °C to obtain a single crystal particle material with D 50 having an average particle size of 3.5 μm. When the single crystal material was treated at 600 °C for 8 hours, it had a decreased BET with a change rate of 2%.

[0098] The above-mentioned large aggregated particles and small single crystal particles were mixed at a mass ratio of 7:3 to obtain a positive electrode active material for a lithium secondary battery. When the positive electrode active material was treated at 600 °C for 8 hours, the BET increased with a change rate of 25%.

[0099] Specific surface area test: A Tri-star3020 specific surface area analyzer was used for the test. 3 g of the sample was weighed. The sample tube was installed at the vacuum joint of the port of the degassing station. The heating temperature was set to 300 °C, and the degassing time was set to 120 minutes. After degassing, the sample tube was cooled. The mass of the empty sample tube and the mass of the sample and the sample tube after degassing were input through the software interface of the analyzer. The specific surface area data (BET method) calculated and output by the software was recorded, and the specific surface area test of the positive electrode material sample was completed.

[0100] Particle size test: The Mastersizer 2000 laser particle size analyzer was used in the test. The following changes were made to the "Measurement" item in the software. Both the "Sample Measurement Time" and "Background Measurement Time" in the "Measurement Time" item were set to 6 seconds. In the item of "Repeated Measurement", the "Number of Repeats" was set to 3 times and the "Delay Time" was set to 5 seconds. "Generate average result record from measurement values" was clicked. Next, "Start" was clicked to automatically measure the background. After the automatic measurement was completed, first 40 ml of sodium pyrophosphate was added, and then a small amount of the sample was added with a spatula. When the obscuration reached 1 / 2 of the visually recognizable range of 10 - 20%, "Start" was clicked. Finally, the three results and their average value were recorded.

[0101] Preparation of button-type battery: First, a nickel-cobalt-manganese composite multi-element cathode active material for non-aqueous electrolyte secondary batteries, acetylene black, and polyvinylidene fluoride (PVDF) were mixed, coated on an aluminum foil, and dried in an oven. Inside an Ar-filled glove box with both the moisture content and oxygen content less than 5 ppm, the dried cathode sheet, separator, anode sheet, and electrolyte were assembled into a 2025-type button battery.

[0102] Measurement method of initial discharge capacity: The button battery was left standing for 2 hours after production. After the open-circuit voltage stabilized, the cathode was charged at a current density of 0.1C until the cut-off voltage of 4.3V, then charged at a constant voltage for 30 minutes, and subsequently discharged at the same current density until the cut-off voltage of 3.0V. This process was carried out once again in the same way, and the discharge capacity was regarded as the initial discharge capacity. Figure 4 shows the charge-discharge curves of button batteries made from the cathode materials of Example 1, Comparative Examples 1 and 2. It can be seen that the initial discharge capacity of the cathode material of Example 1 is higher than that of the cathode materials of the comparative examples.

[0103] Preparation of full battery and gas generation test: The lithium nickel cobalt manganese oxide as the positive electrode material, graphite as the negative electrode material, carbon black as the conductive agent, and PVDF as the binder were dried in a vacuum oven at 120 °C for 12 hours. The oven-dried positive electrode material, conductive agent carbon black, PVDF, and NMP were uniformly mixed to prepare a positive electrode slurry. This slurry was coated on an aluminum foil using a coater for lithium batteries and dried. The electrode sheet was cut by an electrode sheet cutter and wound by an electrode sheet roller.

[0104] 950 g of dried artificial graphite, 13 g of Super-P, 14 g of CMC, 46 g of SBR solution, and 1200 g of deionized water were uniformly mixed to prepare a negative electrode slurry. This slurry was coated on a copper foil using a coater for lithium batteries and dried. The obtained negative electrode sheet after coating was dried in a vacuum oven, cut by an electrode sheet cutter, and wound by an electrode sheet roller.

[0105] The above-mentioned positive electrode sheet and negative electrode sheet were wound in a conventional manufacturing method, and an electrolytic solution was injected to fabricate a full cell. The initial thickness of the formed full cell was measured, and after storing it in a constant temperature bath at 45 °C for 7 days, the thickness of the full cell was measured again. The increase rate of the thickness was used to show the gas generation characteristics of the positive electrode material in the full cell. Figure 5 shows the change in the cycle life of the full cells fabricated from the positive electrode materials of Example 1, Comparative Examples 1 and 2. It can be seen that the full cell manufactured from the positive electrode material of Example 1 shows better stability and a longer cycle life.

[0106]

Table 1

[0107]

Table 2

[0108] The positive electrode active material and the lithium ion battery provided by the present invention achieve the following beneficial effects.

[0109] 1) When compared with the agglomerated material, the single crystal material with the same nickel content has a longer cycle life and lower gas generation ability. Therefore, by introducing the single crystal material, the characteristics of the hybrid material such as cycle life and gas generation can be effectively improved.

[0110] 2) Due to the unique single crystal morphology of the single crystal material, the capacity per gram is lower than that of the agglomerated material with the same nickel content. Therefore, in the present invention, in order to compensate for the disadvantage of low capacity per gram, a single crystal material with a slightly higher nickel content is adopted. At the same time, characteristics such as cycle life and gas generation are maintained at the same level as those of the agglomerated material with less nickel content.

[0111] 3) The incorporated small particle single crystal material can enter the voids between the large agglomerated particles and exhibit a synergistic effect of mutual support and co-filling with the large agglomerated particles, thereby effectively improving the compression density of the material. And,

[0112] 4) Problems of the single crystal material, such as poor fluidity, difficulty in screening and pulping, etc., can be effectively overcome by adding a small amount of large agglomerated spherical particles to the system mainly composed of small single crystal particles.

[0113] Specific embodiments have been described, but these embodiments are presented for illustrative purposes only and are not intended to limit the scope of the present invention. The appended claims and their equivalents are intended to cover all modifications, substitutions, and changes that fall within the scope and spirit of the present invention.

Claims

1. A positive electrode active material for a lithium secondary battery, wherein the positive electrode active material includes agglomerated particles represented by Formula A1 and single crystal particles represented by Formula A2, the positive electrode active material for a lithium secondary battery. A1: Li １＋ａ１ Ni ｘ１ Co ｙ１ M ｚ１ M' １－ｘ１－ｙ１－ｚ１ O ２ A2: Li １＋ａ２ Ni ｘ２ Co ｙ２ M ｚ２ M' １－ｘ２－ｙ２－ｚ２ O ２ Here, M is one or two elements selected from Mn and Al, M' is one or more elements selected from B, F, Mg, Si, P, Ca, Ti, V, Cr, Fe, Ga, Sr, Y, Zr, Nb, Mo, Sn, Ba, La, Ce, and W, -0.03 ≤ a1 ≤ 0.20, preferably -0.01 ≤ a1 ≤ 0.14, more preferably 0 ≤ a1 ≤ 0.10, and particularly preferably 0.01 ≤ a1 ≤ 0.08, 0.30 ≤ x1 ≤ 0.99, preferably 0.57 ≤ x1 ≤ 0.99, more preferably 0.72 ≤ x1 ≤ 0.99, and particularly preferably 0.80 ≤ x1 ≤ 0.99, 0 ≤ y1 ≤ 0.30, preferably 0 ≤ y1 ≤ 0.21, more preferably 0 ≤ y1 ≤ 0.15, and particularly preferably 0 ≤ y1 ≤ 0.10, 0 ≤ z1 ≤ 0.30, preferably 0 ≤ z1 ≤ 0.18, more preferably 0 ≤ z1 ≤ 0.11, and particularly preferably 0 ≤ z1 ≤ 0.06, 0 ≤ 1 - x1 - y1 - z1 ≤ 0.10, preferably 0 ≤ 1 - x1 - y1 - z1 ≤ 0.08, more preferably 0 ≤ 1 - x1 - y1 - z1 ≤ 0.05, and particularly preferably 0 ≤ 1 - x1 - y1 - z1 ≤ 0.03, -0.03 ≤ a2 ≤ 0.20, preferably -0.02 ≤ a2 ≤ 0.16, more preferably -0.01 ≤ a2 ≤ 0.14, and particularly preferably 0 ≤ a2 ≤ 0.08, 0.31 ≤ x2 ≤ 1.00, preferably 0.59 ≤ x2 ≤ 0.995, more preferably 0.75 ≤ x2 ≤ 0.995, and particularly preferably 0.81 ≤ x2 ≤ 0.995, 0 ≤ y2 ≤ 0.30, preferably 0 ≤ y2 ≤ 0.21, more preferably 0 ≤ y2 ≤ 0.15, and particularly preferably 0 ≤ y2 ≤ 0.10, 0 ≤ z2 ≤ 0.30, preferably 0 ≤ z2 ≤ 0.18, more preferably 0 ≤ z2 ≤ 0.11, and particularly preferably 0 ≤ z2 ≤ 0.08, 0 ≤ 1 - x2 - y2 - z2 ≤ 0.10, preferably 0 ≤ 1 - x2 - y2 - z2 ≤ 0.08, more preferably 0 ≤ 1 - x2 - y2 - z2 ≤ 0.05, and particularly preferably 0 ≤ 1 - x2 - y2 - z2 ≤ 0.03, However, 0 < x2 - x1 ≤ 0.5, preferably 0.01 ≤ x2 - x1 ≤ 0.27, more preferably 0.01 ≤ x2 - x1 ≤ 0.2, still more preferably 0.015 ≤ x2 - x1 ≤ 0.20, and particularly preferably 0.02 ≤ x2 - x1 ≤ 0.

15.

2. The positive electrode active material according to claim 1, wherein a2 > a1, preferably 0.01 ≤ a2 - a1 ≤ 0.20, more preferably 0.01 ≤ a2 - a1 ≤ 0.12, particularly preferably 0.01 ≤ a2 - a1 ≤ 0.07, and most preferably 0.01 ≤ a2 - a1 ≤ 0.

04.

3. The aggregated particles have a particle size D of 6 to 30 μm, preferably 8 to 25 μm, more preferably 9 to 20 μm, and particularly preferably 10 to 18 μm. ５０ The positive electrode active material according to claim 1 or 2, having the same.

4. The single crystal particles have a particle size D of 0.1 to 10 μm, preferably 0.5 to 8.0 μm, more preferably 1.0 to 6.0 μm, and particularly preferably 1.5 to 4.5 μm. ５０ The positive electrode active material according to any one of claims 1 to 3, having ５０ .

5. The positive electrode active material according to any one of claims 1 to 4, wherein the agglomerated particles are present in an amount of 20 to 90%, preferably 45 to 85%, more preferably 50 to 80%, and particularly preferably 60 to 80% based on the weight of the positive electrode active material.

6. The positive electrode active material according to any one of claims 1 to 5, wherein the single crystal particles are present in an amount of 10 to 80%, preferably 10 to 70%, more preferably 15 to 60%, and particularly preferably 20 to 40% based on the weight of the positive electrode active material.

7. The positive electrode active material according to any one of claims 1 to 6, wherein the agglomerated particles have a coating layer containing at least one coating element selected from the group consisting of B, F, Mg, Al, Si, P, Ca, Ti, V, Cr, Fe, Ga, Sr, Y, Zr, Nb, Mo, Sn, Ba, La, Ce, and W, and the coating element is present in an amount of 0.1 to 2 mol%, preferably about 1 mol% based on the agglomerated particles.

8. The positive electrode active material according to any one of claims 1 to 7, wherein the single crystal particles have a coating layer containing at least one coating element selected from the group consisting of B, F, Mg, Al, Si, P, Ca, Ti, V, Cr, Fe, Ga, Sr, Y, Zr, Nb, Mo, Sn, Ba, La, Ce, and W, and the coating element is present in an amount of 0.1 to 2 mol%, preferably about 1 mol% based on the single crystal particles.

9. Both the aggregated particles and the single crystal particles each have a coating layer containing at least one coating element selected from the group consisting of B, F, Mg, Al, Si, P, Ca, Ti, V, Cr, Fe, Ga, Sr, Y, Zr, Nb, Mo, Sn, Ba, La, Ce, and W, where the coating element is present in an amount of 0.1 to 2 mol%, preferably about 1 mol%, based on each of the aggregated particles and the single crystal particles. The positive electrode active material according to any one of claims 1 to 8.

10. The coating element contained in the coating layer of the aggregated particles is different from the coating element contained in the coating layer of the single crystal particles. The positive electrode active material according to claim 9.

11. The specific surface area BET of the positive electrode active material before and after firing at 600 °C for 8 hours in an air atmosphere ｂｅｆｏｒｅ and BET ａｆｔｅｒ satisfy the following formula, the positive electrode active material according to any one of claims 1 to 10: | BET ａｆｔｅｒ - BET ｂｅｆｏｒｅ | / BET ｂｅｆｏｒｅ ≤ 50%, Preferably, |BET ａｆｔｅｒ -BET ｂｅｆｏｒｅ | / BET ｂｅｆｏｒｅ ≤ 30%.

12. The BET specific surface area of the agglomerated particles before and after firing at 600°C for 8 hours in an air atmosphere ｂｅｆｏｒｅ and BET ａｆｔｅｒ satisfies the following formula, the positive electrode active material according to any one of claims 1 to 11: (BET ａｆｔｅｒ - BET ｂｅｆｏｒｅ ) / BET ｂｅｆｏｒｅ ≥ 15%, Preferably, 40% ≥ (BET ａｆｔｅｒ - BET ｂｅｆｏｒｅ ) / BET ｂｅｆｏｒｅ ≥ 20%.

13. The specific surface area BET of the single crystal particles before and after firing at 600°C for 8 hours in an air atmosphere ｂｅｆｏｒｅ and BET ａｆｔｅｒ satisfy the following formula, the positive electrode active material according to any one of claims 1 to 12: (BET ｂｅｆｏｒｅ -BET ａｆｔｅｒ ) / BET ｂｅｆｏｒｅ ≤15%, Preferably, 0 ≤ (BET ｂｅｆｏｒｅ - BET ａｆｔｅｒ ) / BET ｂｅｆｏｒｅ ≤ 10%.

14. The positive electrode active material does not contain a nickel-free active material such as lithium iron manganese phosphate. The positive electrode active material according to any one of claims 1 to 13.

15. The positive electrode active material consists of the aggregated particles represented by formula A1 and the single crystal particles represented by formula A2. The positive electrode active material according to any one of claims 1 to 14.

16. The following steps: i) Separately preparing an aggregated particle precursor represented by formula A3 and a single crystal particle precursor represented by formula A4 by a liquid phase coprecipitation method, A3: Ni ｘ１ Co ｙ１ M ｚ１ M' １－ｘ１－ｙ１－ｚ１ (OH) ２ A4: Ni ｘ２ Co ｙ２ M ｚ２ M' １－ｘ２－ｙ２－ｚ２ (OH) ２ where M is one or two elements selected from Mn and Al, M' is one or more elements selected from B, F, Mg, Si, P, Ca, Ti, V, Cr, Fe, Ga, Sr, Y, Zr, Nb, Mo, Sn, Ba, La, Ce, and W, 0.30 ≤ x1 ≤ 0.99, preferably 0.57 ≤ x1 ≤ 0.99, more preferably 0.72 ≤ x1 ≤ 0.99, and particularly preferably 0.80 ≤ x1 ≤ 0.99, 0 ≤ y1 ≤ 0.30, preferably 0 ≤ y1 ≤ 0.21, more preferably 0 ≤ y1 ≤ 0.15, and particularly preferably 0 ≤ y1 ≤ 0.10, 0 ≤ z1 ≤ 0.30, preferably 0 ≤ z1 ≤ 0.18, more preferably 0 ≤ z1 ≤ 0.11, and particularly preferably 0 ≤ z1 ≤ 0.06, 0 ≤ 1 - x1 - y1 - z1 ≤ 0.10, preferably 0 ≤ 1 - x1 - y1 - z1 ≤ 0.08, more preferably 0 ≤ 1 - x1 - y1 - z1 ≤ 0.05, and particularly preferably 0 ≤ 1 - x1 - y1 - z1 ≤ 0.

03. 0.31 ≤ x2 ≤ 1.00, preferably 0.59 ≤ x2 ≤ 0.995, more preferably 0.75 ≤ x2 ≤ 0.995, and particularly preferably 0.81 ≤ x2 ≤ 0.995, and 0 ≤ y2 ≤ 0.30, preferably 0 ≤ y2 ≤ 0.21, more preferably 0 ≤ y2 ≤ 0.15, and particularly preferably 0 ≤ y2 ≤ 0.10, and 0 ≤ z2 ≤ 0.30, preferably 0 ≤ z2 ≤ 0.18, more preferably 0 ≤ z2 ≤ 0.11, and particularly preferably 0 ≤ z2 ≤ 0.08, and 0 ≤ 1 - x2 - y2 - z2 ≤ 0.10, preferably 0 ≤ 1 - x2 - y2 - z2 ≤ 0.08, more preferably 0 ≤ 1 - x2 - y2 - z2 ≤ 0.05, and particularly preferably 0 ≤ 1 - x2 - y2 - z2 ≤ 0.03, and provided that 0 < x2 - x1 ≤ 0.5, preferably 0.01 ≤ x2 - x1 ≤ 0.27, more preferably 0.01 ≤ x2 - x1 ≤ 0.20, still more preferably 0.015 ≤ x2 - x1 ≤ 0.20, and particularly preferably 0.02 ≤ x2 - x1 ≤ 0.15, and ii) Mix the lithium source with the agglomerated particle precursor at a molar ratio r1, optionally incorporating M' as a doping element, where 0.97 ≤ r1 ≤ 1.20, preferably 0.99 ≤ r1 ≤ 1.14, more preferably 1.00 ≤ r1 ≤ 1.10, and particularly preferably 1.01 ≤ r1 ≤ 1.

08. Then, perform primary sintering in a sintering atmosphere of air or oxygen, preferably oxygen, at a sintering temperature T1, where 600°C ≤ T1 ≤ 1000°C, preferably 675°C ≤ T1 ≤ 875°C, more preferably 690°C ≤ T1 ≤ 800°C, and particularly preferably 690°C ≤ T1 ≤ 780°C. Then, obtain agglomerated particles through pulverization, iii) Mix the lithium source with the single-crystal particle precursor at a molar ratio r2, optionally incorporating M' as a doping element, where 0.97 ≤ r2 ≤ 1.20, preferably 0.98 ≤ r2 ≤ 1.16, more preferably 0.99 ≤ r2 ≤ 1.14, and particularly preferably 1.00 ≤ r2 ≤ 1.

08. Then, perform primary sintering at a sintering temperature T2 in a sintering atmosphere of air or oxygen, preferably oxygen, where 650°C ≤ T2 ≤ 1050°C, preferably 730°C ≤ T2 ≤ 930°C, more preferably 750°C ≤ T2 ≤ 930°C, and particularly preferably 750°C ≤ T2 ≤ 900°C. Then, obtain single-crystal particles by pulverization, and iv) obtaining a positive electrode active material by mixing the aggregated particles of step ii) with the single crystal particles of step iii); A method for preparing a positive electrode active material, comprising:

17. The method according to claim 16, wherein r2 > r1, preferably 0.01 ≦ r2 - r1 ≦ 0.20, more preferably 0.01 ≦ r2 - r1 ≦ 0.12, particularly preferably 0.01 ≦ r2 - r1 ≦ 0.07, and most preferably 0.01 ≦ r2 - r1 ≦ 0.

04.

18. The agglomerated particle precursor has a particle size D of 6.5 to 30.5 μm, preferably 8.5 to 25.5 μm, more preferably 9.5 to 20.5 μm, and particularly preferably 10.5 to 18.5 μm. ５０ The method according to claim 16 or 17, having the above.

19. The agglomerated particles have a particle size D of 6 to 30 μm, preferably 8 to 25 μm, more preferably 9 to 20 μm, and particularly preferably 10 to 18 μm ５０ A method according to any one of claims 16 to 18, having

20. The single crystal particle precursor has a particle size D of 0.1 to 30.5 μm, preferably 1.0 to 17.3 μm, more preferably 1.0 to 9.3 μm, and particularly preferably 1.0 to 6.0 μm. ５０ The method according to any one of claims 16 to 19, having the above characteristics.

21. The single crystal particles have a particle size D of 0.1 to 10 μm, preferably 0.5 to 8.0 μm, more preferably 1.0 to 6.0 μm, and particularly preferably 1.5 to 4.5 μm ５０ The method according to any one of claims 16 to 20, having ５０ .

22. The method according to any one of claims 16 to 21, wherein the aggregated particles are present in an amount of 20 to 90%, preferably 45 to 85%, more preferably 50 to 80%, particularly preferably 60 to 80%, based on the weight of the positive electrode active material.

23. The method according to any one of claims 16 to 22, wherein the single crystal particles are present in an amount of 10 to 80%, preferably 10 to 70%, more preferably 15 to 60%, particularly preferably 20 to 40%, based on the weight of the positive electrode active material.

24. Before step iv), the aggregated particles are mixed with a coating precursor containing at least one coating element selected from the group consisting of B, F, Mg, Al, Si, P, Ca, Ti, V, Cr, Fe, Ga, Sr, Y, Zr, Nb, Mo, Sn, Ba, La, Ce, and W, and then secondary sintering is performed at a sintering temperature T3 in a sintering atmosphere of air or oxygen, preferably oxygen, to obtain secondary sintered aggregated particles, where 250°C ≦ T3 ≦ 800°C, preferably 250°C ≦ T3 ≦ 600°C, more preferably 250°C ≦ T3 ≦ 480°C, and particularly preferably 250°C ≦ T3 ≦ 400°C, and the coating element is present in an amount of 0.1 to 2 mol%, preferably about 1 mol%, based on the aggregated particles. The method according to any one of claims 16 to 23.

25. Before the step iv), the single crystal particles are mixed with a coating precursor containing at least one coating element selected from the group consisting of B, F, Mg, Al, Si, P, Ca, Ti, V, Cr, Fe, Ga, Sr, Y, Zr, Nb, Mo, Sn, Ba, La, Ce, and W, and then secondary sintering is performed at a sintering temperature T4 in a sintering atmosphere of air or oxygen, preferably oxygen, to obtain secondary sintered single crystal particles, where 300 °C ≤ T4 ≤ 900 °C, preferably 460 °C ≤ T4 ≤ 800 °C, more preferably 550 °C ≤ T4 ≤ 750 °C, and particularly preferably 600 °C ≤ T4 ≤ 750 °C, and the coating element is present in an amount of 0.1 to 2 mol%, preferably about 1 mol%, based on the single crystal particles. The method according to any one of claims 16 to 24.

26. Before the step iv), the agglomerated particles are mixed with a coating precursor containing at least one coating element selected from the group consisting of B, F, Mg, Al, Si, P, Ca, Ti, V, Cr, Fe, Ga, Sr, Y, Zr, Nb, Mo, Sn, Ba, La, Ce, and W, and then secondary sintering is performed at a sintering temperature T3 in a sintering atmosphere of air or oxygen, preferably oxygen, to obtain secondary sintered agglomerated particles, where 250 °C ≤ T3 ≤ 800 °C, preferably 250 °C ≤ T3 ≤ 600 °C, more preferably 250 °C ≤ T3 ≤ 480 °C, and particularly preferably 250 °C ≤ T3 ≤ 450 °C, and in addition, the single crystal particles are mixed with a coating precursor containing at least one coating element selected from the group consisting of B, F, Mg, Al, Si, P, Ca, Ti, V, Cr, Fe, Ga, Sr, Y, Zr, Nb, Mo, Sn, Ba, La, Ce, and W, and then secondary sintering is performed at a sintering temperature T4 in a sintering atmosphere of air or oxygen, preferably oxygen, to obtain secondary sintered single crystal particles, where 250 °C ≤ T4 ≤ 900 °C, preferably 250 °C ≤ T4 ≤ 750 °C, more preferably 250 °C ≤ T4 ≤ 700 °C, and particularly preferably 300 °C ≤ T4 ≤ 700 °C, and the coating element is present in an amount of 0.1 to 2 mol%, preferably about 1 mol%, based on the agglomerated particles and the single crystal particles respectively. The method according to any one of claims 16 to 25.

27. The coating element contained in the coating precursor of the agglomerated particles is different from the coating element contained in the coating precursor of the single crystal particles. The method according to claim 26.

28. A lithium secondary battery comprising the positive electrode active material according to any one of claims 1 to 13, or the positive electrode active material produced by the method according to any one of claims 16 to 27.

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