Positive electrode active material for lithium secondary battery, method for producing the same, and lithium secondary battery including the same

Abstract

The present invention relates to a cathode active material including at least one secondary particle comprising an aggregate of primary macroparticles, a method for producing the same, and a lithium secondary battery including the same. According to one aspect of the present invention, a cathode active material including secondary particles with improved resistance due to simultaneous growth of the average particle size (D50) of the primary macroparticles and growth of the crystal size can be provided. According to one aspect of the present invention, a nickel-based cathode active material can be provided, which has improved rolling strength, long life characteristics, and excellent gas performance.

Description

Technical Field

[0001] The present invention relates to a positive electrode active material for a lithium secondary battery containing primary large particles and a method for manufacturing the same.

[0002] This application claims priority based on Korean Patent Application No. 10-2020-0142376 filed on October 29, 2020, and all of the content disclosed in the specification and drawings of the application is incorporated into this application.

Background Art

[0003] In recent years, with the rapid spread of electronic devices using batteries such as mobile phones, notebook computers, and electric vehicles, the demand for secondary batteries that are small and lightweight but have relatively high capacity has increased rapidly. In particular, lithium secondary batteries are lightweight and have a high energy density, and have been in the spotlight as a driving power source for portable devices. Therefore, research and development for improving the performance of lithium secondary batteries are actively underway.

[0004] A lithium secondary battery generates electrical energy by oxidation and reduction reactions when lithium ions are inserted / desorbed at the positive and negative electrodes in a state where an organic electrolyte or a polymer electrolyte is filled between a positive electrode and a negative electrode made of an active material capable of inserting (intercalation) and desorbing (deintercalation) lithium ions.

[0005] As the positive electrode active material of a lithium secondary battery, lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), lithium manganese oxide (such as LiMnO2 or LiMn2O4), lithium iron phosphate compound (LiFePO4), etc. are used. Among them, lithium cobalt oxide (LiCoO2) is widely used because of its high operating voltage and excellent capacity characteristics, and is applied as a positive electrode active material for high voltage. However, due to the rising price and supply instability of cobalt (Co), there are limitations in its large-scale use as a power source in fields such as electric vehicles, and the development of alternative positive electrode active materials is required.

[0006] Therefore, nickel cobalt manganese-based lithium composite transition metal oxide in which part of cobalt (Co) is replaced with nickel (Ni) and manganese (Mn) (hereinafter simply referred to as "NCM-based lithium composite transition metal oxide") has been developed.

[0007] On the other hand, the conventionally developed NCM-based lithium composite transition metal oxide is in the form of secondary particles in which primary fine (micro) particles are aggregated as shown in FIG. 1, has a large specific surface area, and low particle strength. In addition, when an electrode is manufactured using a positive electrode active material containing secondary particles in which primary fine particles are aggregated as shown in FIG. 1 and then rolled, particle cracking is severe, so there is a risk that the amount of gas generated during cell driving is large and the stability is reduced. In particular, in the case of a high-content nickel (High-Ni) NCM-based lithium composite transition metal oxide in which the content of nickel (Ni) is increased to ensure high capacity, the structural and chemical stability is further reduced, and it is more difficult to ensure thermal stability.

Summary of the Invention

Problems to be Solved by the Invention

[0008] The problem to be solved by the present invention is to provide a positive electrode active material that minimizes particle cracking during rolling of the positive electrode active material by including primary large particles, which is different from the conventional ones, while having secondary particles having an average particle diameter (D50) equal to or similar to the conventional level.

[0009] Thereby, it is to provide a nickel-based positive electrode active material with an increased rolling density of the positive electrode active material, excellent long-life characteristics and gas performance.

Means for Solving the Problems

[0010] One aspect of the present invention provides a positive electrode active material for a lithium secondary battery according to the following embodiments.

[0011] The first embodiment is including at least one secondary particle containing an aggregate of primary large (macro) particles, The average particle size (D50) of the primary large particles is 2 μm or more. The ratio of the average particle size (D50) of the primary large particles to the average crystal size of the primary large particles is 8 or more. The average particle size (D50) of the secondary particles is 3 to 10 μm. The secondary particles contain a nickel-based lithium transition metal oxide. The present invention relates to a positive electrode active material for a lithium secondary battery, characterized in that when at least one of the secondary particles is rolled at 9 tons (ton), the primary large particles themselves do not crack.

[0012] A second embodiment is the first embodiment, The present invention relates to a positive electrode active material for a lithium secondary battery, wherein the average crystal size of the primary large particles is 200 nm or more.

[0013] A third embodiment is the first or second embodiment, The present invention relates to a positive electrode active material for a lithium secondary battery, wherein the ratio of the average particle size (D50) of the secondary particles to the average particle size (D50) of the primary large particles is 2 to 4.

[0014] A fourth embodiment is any one of the first to third embodiments, The nickel-based lithium transition metal oxide is Li a Ni 1-x-y Co x M1 y M2 w O2 (1.0 ≤ a ≤ 1.5, 0 ≤ x ≤ 0.2, 0 ≤ y ≤ 0.2, 0 ≤ w ≤ 0.1, 0 ≤ x + y ≤ 0.2, M1 is at least one selected from the group consisting of Mn and Al, M2 is at least one selected from the group consisting of Ba, Ca, Zr, Ti, Mg, Ta, Nb and Mo), and relates to a positive electrode active material for a lithium secondary battery.

[0015] A fifth embodiment is any one of the first to fourth embodiments, The present invention relates to a positive electrode active material for a lithium secondary battery, wherein the fine particles of 1 μm or less after rolling the positive electrode active material at 9 tons are less than 10%.

[0016] Embodiment 6 is in any one of Embodiments 1 to 5, relates to a positive electrode active material for a lithium secondary battery, wherein the positive electrode active material further contains at least one of zirconium, yttrium, and strontium as a firing additive.

[0017] Embodiment 7 is in any one of Embodiments 1 to 6, relates to a positive electrode active material for a lithium secondary battery, wherein a boron-containing material is further coated on the surface of the positive electrode active material.

[0018] Embodiment 8 is in any one of Embodiments 1 to 7, relates to a positive electrode active material for a lithium secondary battery, wherein a cobalt-containing material is further coated on the surface of the positive electrode active material.

[0019] Another aspect of the present invention provides a positive electrode for a lithium secondary battery according to the following embodiments.

[0020] Embodiment 9 provides a positive electrode for a lithium secondary battery including the above-described positive electrode active material.

[0021] Still another aspect of the present invention provides a lithium secondary battery according to the following embodiments.

[0022] Embodiment 10 provides a lithium secondary battery including the above-described positive electrode active material.

[0023] Still another aspect of the present invention provides a method for manufacturing a positive electrode active material for a lithium secondary battery according to the following embodiments.

[0024] Embodiment 11 is (S1) mixing a nickel-based transition metal oxide precursor having a tap density of 2.0 g / cc or less and a lithium precursor and performing primary firing; and (S2) subjecting the resultant of the primary firing to secondary firing. Provided is a method for manufacturing a positive electrode active material for a lithium secondary battery as described above.

[0025] A twelfth embodiment provides a method for manufacturing a positive electrode active material for a lithium secondary battery, in the eleventh embodiment, wherein the temperature of the first firing is 780 to 900 °C.

[0026] A thirteenth embodiment relates to a method for manufacturing a positive electrode active material for a lithium secondary battery, in the eleventh or twelfth embodiment, wherein the temperature of the second firing is 650 to 800 °C.

[0027] A fourteenth embodiment relates to a method for manufacturing a positive electrode active material for a lithium secondary battery, in any one of the eleventh to thirteenth embodiments, wherein a water washing step is not included between the steps (S1) and (S2).

Advantages of the Invention

[0028] According to one aspect of the present invention, it is possible to provide a positive electrode active material including secondary particles in which the crystal size grows simultaneously with the growth of the average particle diameter (D50) of the primary large particles, and the resistance is improved.

[0029] According to one aspect of the present invention, it is possible to provide a nickel-based positive electrode active material in which the rolling density of the positive electrode active material is increased, and which has excellent long-life characteristics and gas performance.

[0030] The drawings attached to this specification illustrate desirable embodiments of the present invention, and serve to further understand the technical idea of the present invention together with the content of the invention. Therefore, the present invention should not be construed as being limited only to the matters described in the drawings. On the other hand, the shape, size, scale, or ratio of elements in the drawings attached to this specification may be exaggerated for more clear explanation.

Brief Description of the Drawings

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Mode for Carrying Out the Invention

[0032] Hereinafter, embodiments of the present invention will be described in detail. Prior to this, the terms and words used in this specification and the claims should not be construed as being limited to their ordinary and dictionary meanings. The inventor himself must interpret them in accordance with the meaning and concept corresponding to the technical idea of the present invention in accordance with the principle that he can appropriately define the concept of the term in order to explain the invention in the best way. Therefore, it must be understood that the configurations shown in the embodiments described in this specification are merely the most desirable embodiments of the present invention and do not represent all of the technical ideas of the present invention. At the time of this application, there can be various equivalents and modifications that can replace them.

[0033] Throughout this specification, unless otherwise specified, when a part "includes" other components, it means that it may further include other components rather than excluding them.

[0034] In this specification and the claims, "including a number of crystal grains" means a crystal formed by aggregation of two or more crystal particles having an average crystal size within a specific range. At this time, the crystal size of the crystal grains can be quantitatively analyzed using X-ray diffraction analysis (XRD) with CuKα X-rays (Xrα). Specifically, the average crystal size of the crystal grains can be quantitatively analyzed by putting the manufactured particles into a holder and analyzing the diffraction pattern formed by irradiating the particles with X-rays.

[0035] In this specification and the claims, D50 can be defined as the particle diameter at the 50% criterion of the particle size distribution and can be measured using the laser diffraction method. For example, the method for measuring the average particle diameter (D50) of the positive electrode active material is to disperse the particles of the positive electrode active material in a dispersion medium and then introduce them into a commercially available laser diffraction particle size measuring device (for example, Microtrac MT3000), irradiate them with ultrasonic waves of about 28 kHz at an output of 60 W, and then calculate the average particle diameter (D50) corresponding to 50% of the volume cumulative amount in the measuring device.

[0036] In the present invention, "primary particles" mean particles that do not have grain boundaries in appearance when observed at a magnification of 5,000 to 20,000 times using a scanning electron microscope.

[0037] In the present invention, "secondary particles" are particles formed by aggregation of the primary particles.

[0038] In the present invention, "single particles" are particles that exist independently of the secondary particles and do not have grain boundaries in appearance, and for example, mean particles having a particle diameter of 0.5 μm or more.

[0039] In the present invention, when "particles" are described, it may mean that any one or all of single particles, secondary particles, and primary particles are included.

[0040] <Positive electrode active material> One aspect of the present invention provides a positive electrode active material having a secondary particle form different from the conventional one.

[0041] Specifically, 1) It includes at least one secondary particle containing an aggregate of primary large particles, 2) The average particle size (D50) of the primary large particles is 2 μm or more, 3) The ratio of the average particle size (D50) of the primary large particles to the average crystal size of the primary large particles is 8 or more, 4) The average particle size (D50) of the secondary particles is 3 to 10 μm, 5) The secondary particles are a positive electrode active material containing a nickel-based lithium transition metal oxide.

[0042] By having the characteristics of the above 1) to 5), the primary particles and the secondary particles can provide a nickel-based positive electrode active material excellent in long-life characteristics and gas performance.

[0043] Hereinafter, the above 1) to 5) characteristics of the primary particles and the secondary particles will be described in detail.

[0044] <Particle morphology and primary large particles> Generally, nickel-based lithium transition metal oxides are secondary particles. Such secondary particles can be in a form in which primary particles are aggregated.

[0045] Specifically, using dense nickel-based lithium transition metal hydroxide secondary particles produced by the coprecipitation method as a precursor, mixing the precursor with a lithium precursor and firing at a temperature below 960 °C can obtain nickel-based lithium transition metal oxide secondary particles. Such conventional secondary particles are shown in Fig. 1. However, when a positive electrode active material containing such conventional secondary particles is coated on a current collector and then rolled, the particles themselves crack and the specific surface area increases. If the specific surface area increases, there is a problem that a rock salt-type structure is formed on the surface and the resistance decreases.

[0046] In an attempt to solve such problems, single-particle cathode active materials have been developed. Specifically, unlike the conventional method using dense nickel-based lithium transition metal hydroxide secondary particles as a precursor, by using a precursor that is porous compared to the conventional precursor, synthesis can be achieved at a lower firing temperature in comparison with the same nickel content, and nickel-based lithium transition metal oxides that are single-particle and do not have a further secondary particle form can be obtained. However, when a cathode active material containing such single particles is applied onto a current collector and then rolled, although the single particles themselves do not break, there are problems such as other active materials breaking.

[0047] One aspect of the present invention is to solve such problems.

[0048] When firing is carried out by only increasing the firing temperature with a precursor having a high density as in the conventional case, it was inevitable that not only the average particle size (D50) of the primary particles but also the average particle size (D50) of the secondary particles increased.

[0049] On the other hand, the secondary particles according to one aspect of the present invention differ from the conventional single-particle obtaining method in the following points.

[0050] As described above, the conventional single particles were formed by directly using the conventional precursor for secondary particles and only increasing the primary firing temperature to form single particles. On the other hand, for the secondary particles according to one aspect of the present invention, a precursor with a high porosity is separately used. As a result, large primary giant particles with a large particle size can grow without increasing the firing temperature, while on the other hand, the secondary particles grow relatively insufficiently compared to the conventional case.

[0051] As a result, the secondary particles according to one aspect of the present invention have a form in which the average particle size (D50) of the primary particles is large while having the same or similar average particle size (D50) as the conventional case. That is, different from the general form of the conventional cathode active material, that is, the form in which primary particles with a small average particle size gather to form secondary particles, it provides a form of secondary particles in which large primary giant particles with enlarged primary particles are aggregated.

[0052] Specifically, the secondary particles according to one aspect of the present invention mean aggregates of primary giant particles as shown in FIG. 2. In a specific embodiment of the present invention, the secondary particles may be those in which 1 to 10 of the primary giant particles are aggregated. More specifically, the secondary particles may be those in which the primary giant particles are aggregated by 1 or more, 2 or more, 3 or more, or 4 or more within the above numerical range, and those in which the primary giant particles are aggregated by 10 or less, 9 or less, 8 or less, or 7 or less within the above numerical range.

[0053] In the present invention, the "primary giant particle" has an average particle size (D50) of 2 μm or more.

[0054] In a specific embodiment of the present invention, the average particle size of the primary giant particles may be 2 μm or more, 2.5 μm or more, 3 μm or more, or 3.5 μm or more, and may be 5 μm or less, 4.5 μm or less, or 4 μm or less. When the average particle size of the primary giant particles is less than 2 μm, it corresponds to conventional secondary particles, and there may be a problem of particle cracking during rolling.

[0055] On the other hand, in the present invention, the "primary giant particle" means one in which the ratio of the average particle size (D50) to the average crystal size is 8 or more. That is, the primary giant particle is one in which the average particle size and the average crystal size of the primary particles have grown simultaneously when compared with the primary fine particles constituting the conventional secondary particles.

[0056] From the viewpoint of cracks, it is advantageous to have a large average particle size while there is no grain boundary in appearance like conventional single particles. Therefore, the present inventors focused on growing the average particle size (D50) of the primary particles. In the process, it was found that when only the average particle size (D50) of the primary particles is increased by overfiring or the like, there is a problem that a rock salt-type structure is formed on the surface of the primary particles and the initial resistance becomes high. In order to solve such a problem, the present inventors devised a method for reducing the resistance, and confirmed that in order to reduce the resistance, the crystal size of the primary particles must also be grown together.

[0057] Therefore, the primary large particles in the present invention mean particles that have a large average crystal size as well as a large average particle size and do not have grain boundaries in appearance.

[0058] When the average particle size and the average crystal size of the primary particles grow simultaneously in this way, compared with conventional single particles in which a rock salt-type structure is formed on the surface by firing at a high temperature and the resistance increase is large, the resistance is lower and it is also advantageous in terms of long life.

[0059] Thus, in the case of "secondary particles composed of aggregates of primary large particles" used in one aspect of the present invention, compared with conventional single particles, it is advantageous in that the resistance is lowered due to an increase in the size of the primary particles themselves and a decrease in the formation of the rock salt-type structure.

[0060] At this time, the average crystal size of the primary large particles can be quantitatively analyzed using X-ray diffraction analysis (XRD) with CuKα X-ray. Specifically, by putting the manufactured particles in a holder and analyzing the diffraction pattern created by irradiating the particles with X-rays, the average crystal size of the primary large particles can be quantitatively analyzed.

[0061] In a specific embodiment of the present invention, the ratio of the average particle size (D50) to the average crystal size is 8 or more, desirably 10 or more.

[0062] Also, the average crystal size of the primary large particles can be 200 nm or more, 250 nm or more, or 300 nm or more.

[0063] <Secondary particles> The secondary particles according to one aspect of the present invention have a form in which the average particle size (D50) of the primary particles is large while having the same or a similar average particle size (D50) as in the prior art. That is, different from the general form of the conventional positive electrode active material, that is, the form in which primary particles with a small average particle size gather to form secondary particles, it provides a form of secondary particles in which large primary large particles are aggregated.

[0064] The secondary particles according to one aspect of the present invention have an average particle size (D50) of 3 μm to 10 μm. More specifically, it is 3 μm or more, 3.5 μm or more, 4 μm or more, 4.5 μm or more, 5 μm or more, 5.5 μm or more, or 6 μm or more, and 10 μm or less, 9 μm or less, 8 μm or less, 7.5 μm or less, 7 μm or less, or 6.5 μm or less.

[0065] Generally, regardless of the particle morphology, for the same composition, as the firing temperature increases, the particle size and the average crystal size within the particle increase. On the other hand, the secondary particles according to one aspect of the present invention can grow primary giant particles with a large particle size without increasing the firing temperature compared to the prior art. On the other hand, the secondary particles grow relatively insufficiently compared to the prior art.

[0066] As a result, the secondary particles according to one aspect of the present invention are composed of primary giant particles having a larger average particle size and average crystal size than conventional primary fine particles, while having the same or similar average particle size (D50) as conventional secondary particles.

[0067] FIG. 1 and FIG. 2 are SEM photographs respectively taken of conventional secondary particles having the same average particle size (D50) and secondary particles according to one embodiment of the present invention.

[0068] Looking at FIG. 1, secondary particles with an average particle size (D50) of about 5 μm in which dozens of primary fine particles with an average particle size (D50) of about 0.5 μm are aggregated can be confirmed. Such conventional secondary particles have a large specific surface area and a large number of rock salt-type structures are formed. When rolling a positive electrode active material containing such secondary particles, there is a problem of a large amount of particle cracking.

[0069] On the other hand, looking at FIG. 2, secondary particles with an average particle size (D50) of about 5 μm in which 10 or fewer primary giant particles with an average particle size (D50) of about 2.5 μm are aggregated can be confirmed. Such secondary particles have no particle cracking during the rolling of the positive electrode active material, and are characterized in that particle cracking is minimized when blended with other particles and rolled.

[0070] More specifically, when rolling at least one or more of the secondary particles at 9 tons, the primary giant particles fall off, and the primary giant particles themselves do not crack.

[0071] Accordingly, the cathode active material according to one aspect of the present invention has less than 10% of fine particles of 1 μm or less after rolling at 9 tons.

[0072] In a specific embodiment of the present invention, the ratio of the average particle diameter (D50) of the secondary particles to the average particle diameter (D50) of the primary giant particles can be 2 to 4.

[0073] <Composition> The secondary particles contain a nickel-based lithium transition metal oxide.

[0074] At this time, the nickel-based lithium transition metal oxide may contain Li a Ni 1-x-y Co x M1 y M2 w O2 (1.0 ≤ a ≤ 1.5, 0 ≤ x ≤ 0.2, 0 ≤ y ≤ 0.2, 0 ≤ w ≤ 0.1, 0 ≤ x + y ≤ 0.2, M1 is at least one selected from the group consisting of Mn and Al, M2 is at least one selected from the group consisting of Ba, Ca, Zr, Ti, Mg, Ta, Nb, and Mo).

[0075] In the above formula, a, x, y, and w represent the molar ratios of the respective elements in the nickel-based lithium transition metal oxide.

[0076] At this time, the metals M1 and M2 doped in the crystal lattice of the secondary particles may be located only on a part of the surface of the particles according to the site preference of element M1 and / or element M2, may be located while having a concentration gradient decreasing from the surface of the particles toward the center, or may be uniformly present throughout the particles.

[0077] When the secondary particles are doped or coated and doped with metals M1 and M2, the long-life characteristics of the active material can be further improved, particularly by stabilizing the surface structure.

[0078] The positive electrode active material may further contain at least one of zirconium, yttrium, and strontium as a firing additive.

[0079] The positive electrode active material may be coated on the surface with a boron-containing substance, such as lithium borate oxide, at a boron content of 2,000 ppm or less.

[0080] The positive electrode active material may be coated on the surface with a cobalt-containing substance, such as lithium cobalt oxide, at a cobalt content of 20,000 ppm or less.

[0081] <Method for manufacturing positive electrode active material> The positive electrode active material according to one embodiment of the present invention described above can be manufactured by the following method, but is not limited thereto.

[0082] Specifically, it includes (S1) a step of mixing a nickel-based transition metal oxide precursor having a tap density of 2.0 g / cc or less and a lithium precursor and performing primary firing, and (S2) a step of performing secondary firing on the result of the primary firing.

[0083] The manufacturing method of the positive electrode active material will be further described step by step.

[0084] First, a positive electrode active material precursor containing nickel (Ni), cobalt (Co), and manganese (Mn) and having a tap density of 2.0 g / cc or less is prepared.

[0085] At this time, as the precursor for manufacturing the positive electrode active material, a commercially available positive electrode active material precursor may be used, or it may be manufactured by a method for manufacturing a positive electrode active material precursor well known in the art.

[0086] For example, the precursor may be produced by adding an ammonium cation-containing chelating agent and a basic compound to a transition metal solution containing a nickel-containing raw material substance, a cobalt-containing raw material substance, and a manganese-containing raw material substance, and subjecting them to a coprecipitation reaction.

[0087] The nickel-containing raw material substance may be, for example, a nickel-containing acetate, nitrate, sulfate, halide, sulfide, hydroxide, oxide, or oxyhydroxide, etc. Specifically, it may be Ni(OH)2, NiO, NiOOH, NiCO3·2Ni(OH)2·4H2O, NiC2O2·2H2O, Ni(NO3)2·6H2O, NiSO4, NiSO4·6H2O, nickel fatty acid salt, nickel halide, or a combination thereof, but is not limited thereto.

[0088] The cobalt-containing raw material substance may be a cobalt-containing acetate, nitrate, sulfate, halide, sulfide, hydroxide, oxide, or oxyhydroxide, etc. Specifically, it may be Co(OH)2, CoOOH, Co(OCOCH3)2·4H2O, Co(NO3)2·6H2O, CoSO4, Co(SO4)2·7H2O, or a combination thereof, but is not limited thereto.

[0089] The manganese-containing raw material substance may be, for example, a manganese-containing acetate, nitrate, sulfate, halide, sulfide, hydroxide, oxide, oxyhydroxide, or a combination thereof. Specifically, it may be manganese oxides such as Mn2O3, MnO2, Mn3O4, etc.; manganese salts such as MnCO3, Mn(NO3)2, MnSO4, manganese acetate, manganese dicarboxylate salt, manganese citrate, manganese fatty acid salt; manganese oxyhydroxide, manganese chloride, or a combination thereof, but is not limited thereto.

[0090] The transition metal solution is produced by adding a nickel-containing raw material substance, a cobalt-containing raw material substance, and a manganese-containing raw material substance to a solvent, specifically water, or a mixed solvent of water and an organic solvent (such as alcohol, etc.) that can be uniformly mixed with water, or it can be produced by mixing an aqueous solution of a nickel-containing raw material substance, an aqueous solution of a cobalt-containing raw material substance, and a manganese-containing raw material substance.

[0091] The ammonium cation-containing chelating agent can be, for example, NH4OH, (NH4)2SO4, NH4NO3, NH4Cl, CH3COONH4, (NH4)2CO3, or a combination thereof, but is not limited thereto. On the other hand, the ammonium cation-containing chelating agent may be used in the form of an aqueous solution, and as the solvent at this time, water, or a mixture of water and an organic solvent (specifically, alcohol, etc.) that can be uniformly mixed with water can be used.

[0092] The basic compound can be a hydroxide of an alkali metal or alkaline earth metal such as NaOH, KOH, or Ca(OH)2, hydrates thereof, or a combination thereof. The basic compound may also be used in the form of an aqueous solution, and as the solvent at this time, water, or a mixture of water and an organic solvent (specifically, alcohol, etc.) that can be uniformly mixed with water can be used.

[0093] The basic compound is added to adjust the pH of the reaction solution, and can be added in an amount such that the pH of the metal solution becomes 9 to 11.

[0094] On the other hand, the coprecipitation reaction can be carried out at a temperature of 40°C to 70°C in an inert atmosphere such as nitrogen or argon.

[0095] By the above-described process, nickel-cobalt-manganese hydroxide particles are formed and precipitate in the reaction solution. By adjusting the concentrations of the nickel-containing raw material substance, cobalt-containing raw material substance, and manganese-containing raw material substance, a precursor in which the content of nickel (Ni) in the total metal content is 60 mol% or more can be produced. The precipitated nickel-cobalt-manganese hydroxide particles can be separated by a conventional method and dried to obtain a nickel-cobalt-manganese precursor. The precursor may be secondary particles formed by aggregation of primary particles.

[0096] Thereafter, the above-described precursor and a lithium raw material substance are mixed and subjected to primary firing.

[0097] As the lithium raw material substance, lithium-containing sulfates, nitrates, acetates, carbonates, oxalates, citrates, halides, hydroxides, or oxyhydroxides, etc. can be used, and there is no particular limitation as long as it is soluble in water. Specifically, the lithium raw material substance may be Li2CO3, LiNO3, LiNO2, LiOH, LiOH·H2O, LiH, LiF, LiCl, LiBr, LiI, CH3COOLi, Li2O, Li2SO4, CH3COOLi, or Li3C6H5O7, etc., and any one or a mixture of two or more of these can be used.

[0098] In the case of a high-content nickel (high-Ni) NCM-based lithium composite transition metal oxide in which the content of nickel (Ni) is 60 mol% or more, the primary firing can be performed at 700 to 1,000 °C, more preferably at 780 to 980 °C, and even more preferably at 780 to 900 °C. The primary firing can be performed in an air or oxygen atmosphere and can be performed for 10 to 35 hours.

[0099] Next, after the primary firing, additional secondary firing is performed.

[0100] In the case of the secondary firing of a high-content nickel (high-Ni) NCM-based lithium composite transition metal oxide with a nickel (Ni) content of 60 mol% or more, it can be fired at 650 to 800 °C, more desirably at 700 to 800 °C, and even more desirably at 700 to 750 °C. The secondary firing can be carried out in an air or oxygen atmosphere. During or after the secondary firing, cobalt oxide or cobalt hydroxide may be added so that the cobalt content becomes 20,000 ppm or less to coat the surface of the positive electrode active material with a cobalt-containing substance. In addition, during or after firing, boric acid or the like may be added so that the boron content becomes 2,000 ppm or less to coat the surface of the positive electrode active material with a boron-containing substance. Additionally, during firing, it may further contain at least one of zirconium, yttrium, and strontium as a firing additive.

[0101] On the other hand, it is characterized by not including a separate water washing process between the step (S1) and the step (S2).

[0102] Through such a process, a positive electrode active material including secondary particle aggregates containing primary large particles can be manufactured.

[0103] <Positive Electrode and Lithium Secondary Battery> According to still another aspect of the present invention, there are provided a positive electrode for a lithium secondary battery including the positive electrode active material and a lithium secondary battery.

[0104] Specifically, the positive electrode includes a positive electrode current collector and a positive electrode active material layer formed on the positive electrode current collector and including the positive electrode active material.

[0105] In the positive electrode, the positive electrode current collector is not particularly limited as long as it has conductivity without inducing chemical changes in the battery, and examples thereof include stainless steel, aluminum, nickel, titanium, fired carbon, or those obtained by surface treatment of aluminum or stainless steel with carbon, nickel, titanium, silver, etc. The positive electrode current collector may usually have a thickness of 3 to 500 μm, and fine irregularities may be formed on the surface of the positive electrode current collector to enhance the adhesive force of the positive electrode active material. For example, it can be used in various forms such as films, sheets, foils, nets, porous bodies, foams, non-woven fabrics, etc.

[0106] The positive electrode active material layer may contain a conductive material and a binder together with the above-described positive electrode active material.

[0107] At this time, the conductive material is used to impart conductivity to the electrode, and can be used without particular limitation as long as it has electron conductivity without causing chemical changes in the configured battery. Specific examples include graphite such as natural graphite and artificial graphite; carbon-based substances such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black, carbon fiber; metal powders or metal fibers such as copper, nickel, aluminum, silver; conductive whiskers such as zinc oxide, potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives. Among these, one kind alone or a mixture of two or more kinds can be used. The conductive material may usually be contained in an amount of 1 to 30% by weight based on the total weight of the positive electrode active material layer.

[0108] In addition, the binder plays a role in improving the adhesion between the positive electrode active material particles and the adhesive force between the positive electrode active material and the positive electrode current collector. Specific examples include polyvinylidene fluoride (PVdF), vinylidene fluoride-hexafluoropropylene copolymer (PVdF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated EPDM, styrene-butadiene rubber (SBR), fluororubber, or various copolymers thereof. Among these, one kind alone or a mixture of two or more kinds can be used. The binder may be contained in an amount of 1 to 30% by weight based on the total weight of the positive electrode active material layer.

[0109] The positive electrode can be manufactured by a normal positive electrode manufacturing method except for using the positive electrode active material described above. Specifically, it can be manufactured by applying a composition for forming a positive electrode active material layer containing the positive electrode active material, and optionally, a binder and a conductive material, onto a positive electrode current collector, followed by drying and rolling. At this time, the types and contents of the positive electrode active material, binder, and conductive material are as described above.

[0110] The solvent can be a solvent generally used in the art, and examples include dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, or water. Among these, one kind alone or a mixture of two or more kinds can be used. The amount of the solvent used is sufficient as long as it dissolves or disperses the positive electrode active material, conductive material, and binder in consideration of the coating thickness of the slurry and the production yield, and gives a viscosity that shows excellent thickness uniformity during coating for subsequent positive electrode manufacturing.

[0111] As another method, the positive electrode may be manufactured by casting the composition for forming the positive electrode active material layer on a separate support, and then laminating the film obtained by peeling from the support onto the positive electrode current collector.

[0112] According to still another aspect of the present invention, an electrochemical element including the positive electrode is provided. The electrochemical element may specifically be a battery or a capacitor, and more specifically may be a lithium secondary battery.

[0113] The lithium secondary battery specifically includes a positive electrode, a negative electrode positioned opposite to the positive electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte, and the positive electrode is as described above. Further, the lithium secondary battery may selectively further include a battery container for housing the electrode assembly of the positive electrode, the negative electrode, and the separator, and a sealing member for sealing the battery container.

[0114] In the lithium secondary battery, the negative electrode includes a negative electrode current collector and a negative electrode active material layer positioned on the negative electrode current collector.

[0115] The negative electrode current collector is not particularly limited as long as it has high conductivity without inducing a chemical change in the battery. For example, copper, stainless steel, aluminum, nickel, titanium, fired carbon, those surface-treated with carbon, nickel, titanium, silver, etc. on the surface of copper or stainless steel, aluminum-cadmium alloy, etc. can be used. Further, the negative electrode current collector may usually have a thickness of 3 to 500 μm, and similar to the positive electrode current collector, fine irregularities may be formed on the surface of the current collector to enhance the adhesion of the negative electrode active material. For example, it can be used in various forms such as films, sheets, foils, nets, porous bodies, foams, non-woven fabrics.

[0116] The negative electrode active material layer selectively includes a binder and a conductive material together with the negative electrode active material. The negative electrode active material layer is, for example, formed by applying a negative electrode forming composition including a negative electrode active material, and selectively a binder and a conductive material, on the negative electrode current collector and drying it, or by casting the negative electrode forming composition on a separate support, peeling the film obtained from the support, and laminating it on the negative electrode current collector.

[0117] As the negative electrode active material, a compound capable of reversible insertion and deintercalation of lithium can be used. Specific examples include carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber, and amorphous carbon; metallic compounds alloyable with lithium such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloy, Sn alloy, or Al alloy; SiO β (0 < β < 2), metal oxides capable of doping and dedoping lithium such as SnO2, vanadium oxide, and lithium vanadium oxide; or composites containing the metallic compound and the carbonaceous material such as Si-C composites or Sn-C composites, etc. Among these, any one or a mixture of two or more thereof can be used. Further, a thin film of metallic lithium may be used as the negative electrode active material. Also, as the carbon material, all of low-crystalline carbon and high-crystalline carbon can be used. Representative examples of low-crystalline carbon are soft carbon and hard carbon, and representative examples of high-crystalline carbon are amorphous, plate-like, flaky, spherical, or fibrous natural graphite or artificial graphite, kish graphite, pyrolytic carbon, mesophase pitch based carbon fiber, meso-carbon microbeads, mesophase pitches, and high-temperature calcined carbon such as petroleum or coal-based coke.

[0118] Also, the binder and the conductive material are the same as those described above for the positive electrode.

[0119] On the one hand, in the lithium secondary battery, the separator separates the negative electrode and the positive electrode and provides a migration path for lithium ions. It can be used without particular limitation as long as it is usually used as a separator for lithium secondary batteries. In particular, those with low resistance to ion migration of the electrolyte and excellent electrolyte impregnation ability are desirable. Specifically, a porous polymer film, for example, a porous polymer film made of polyolefin-based polymers such as ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer, and ethylene / methacrylate copolymer, or a laminate structure of two or more layers thereof can be used. Also, a normal porous non-woven fabric, for example, a non-woven fabric made of high-melting glass fibers, polyethylene terephthalate fibers, etc. may be used. Further, for ensuring heat resistance or mechanical strength, a coated separator containing a ceramic component or a polymer substance can be used and can be selectively used in a single-layer or multi-layer structure.

[0120] In addition, examples of the electrolyte used in the present invention include, but are not limited to, organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel-type polymer electrolytes, solid inorganic electrolytes, and molten inorganic electrolytes that can be used during the manufacture of lithium secondary batteries.

[0121] Specifically, the electrolyte may contain an organic solvent and a lithium salt.

[0122] As the organic solvent, any solvent can be used without particular limitation as long as it can serve as a medium in which ions involved in the electrochemical reaction of the battery can move. Specifically, examples of the organic solvent include ester solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, and ε-caprolactone; ether solvents such as dibutyl ether or tetrahydrofuran; ketone solvents such as cyclohexanone; aromatic hydrocarbon solvents such as benzene and fluorobenzene; carbonate solvents such as dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), ethylene carbonate (EC), and propylene carbonate (PC); alcohol solvents such as ethyl alcohol and isopropyl alcohol; nitriles such as R-CN (where R is a hydrocarbon group having a linear, branched, or cyclic structure of C2 to C20 and may contain a double bond aromatic ring or an ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; or sulfolanes. Among them, carbonate solvents are desirable, and a mixture of a cyclic carbonate having a high dielectric constant that can improve the charge-discharge performance of the battery (for example, ethylene carbonate or propylene carbonate) and a linear carbonate compound having a low viscosity (for example, ethyl methyl carbonate, dimethyl carbonate, or diethyl carbonate) is more desirable. In this case, it is desirable to mix and use the cyclic carbonate and the linear carbonate at a volume ratio of about 1:1 to about 1:9 for excellent electrolyte performance.

[0123] The lithium salt can be used without particular limitation as long as it is a compound capable of providing lithium ions used in a lithium secondary battery. Specifically, the lithium salt can be LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAlO4, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2, LiCl, LiI, or LiB(C2O4)2, etc. The concentration of the lithium salt can be within the range of 0.1 to 2.0 M. If the concentration of the lithium salt is within the above range, since the electrolyte has appropriate conductivity and viscosity, it exhibits excellent electrolyte performance and lithium ions can move effectively.

[0124] In addition to the above-described electrolyte constituent components, the electrolyte may further contain one or more additives such as haloalkylene carbonate-based compounds such as difluoroethylene carbonate, pyridine, triethyl phosphite, triethanolamine, cyclic ether, ethylenediamine, n-glyme, hexamethylphosphoric triamide, nitrobenzene derivatives, sulfur, quinoneimine dyes, N-substituted oxazolidinone, N,N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salts, pyrrole, 2-methoxyethanol, or aluminum trichloride, etc., for the purpose of improving battery life characteristics, suppressing battery capacity reduction, improving the discharge capacity of the battery, etc. At this time, the additive may be contained in an amount of 0.1 to 5% by weight based on the total weight of the electrolyte.

[0125] The lithium secondary battery containing the positive electrode active material according to the present invention is useful in portable devices such as mobile phones, notebook computers, digital cameras, etc., and in the field of electric vehicles such as hybrid electric vehicles (HEVs).

[0126] Thereby, according to still another aspect of the present invention, a battery module including the lithium secondary battery as a unit cell, and a battery pack including the same are provided.

[0127] The battery module or battery pack can be used as a power source for one or more of the following medium to large-sized devices: power tools; electric vehicles including electric vehicles (EVs), hybrid electric vehicles, and plug-in hybrid electric vehicles (PHEVs); or power storage systems.

[0128] Hereinafter, examples will be given and described in detail so that those with ordinary knowledge in the technical field to which the present invention pertains can easily implement the present invention. However, the present invention can be embodied in various other forms and is not limited to the examples described below.

[0129] <Example 1> Nickel-cobalt-manganese-containing hydroxide (Ni 0.88 Co 0.08 Mn 0.04 (OH)2) cathode active material precursor and lithium raw material LiOH were charged into a Henschel mixer (700L) so that the final Li / M(Ni, Co, Mn) molar ratio was 1.03, and mixed at 300 rpm for 20 minutes at the center. The mixed powder was placed in an alumina crucible with a size of 330 mm × 330 mm, and primary fired at 880 °C for 10 hours in an oxygen (O2) atmosphere to form a primary fired product.

[0130] Thereafter, the primary fired product was ground using a jet mill at a feeding pressure of 80 psi and a grinding pressure of 60 psi.

[0131] The ground primary fired product was placed in an alumina crucible with a size of 330 mm × 330 mm, 10,000 ppm of Co(OH)2 was added in an oxygen (O2) atmosphere, and secondary fired at 700 °C for 5 hours to produce a cathode active material.

[0132] <Example 2> The same procedure as in Example 1 was carried out except that the conditions were changed as shown in Table 1 below.

[0133] <Comparative Example 1> After adding 4 liters of distilled water to a coprecipitation reactor (capacity: 20 L), 100 mL of an aqueous ammonia solution with a concentration of 28% by weight was added while maintaining the temperature at 50°C. Then, a transition metal solution with a concentration of 3.2 mol / L, in which NiSO4, CoSO4, MnSO4, and Al3(SO4)2 were mixed so that the molar ratio of nickel:cobalt:manganese:aluminum was 82:5:11:2, was continuously added to the reactor at a rate of 300 mL / hr, and an aqueous ammonia solution of 28% by weight was added at a rate of 42 mL / hr. Stirring was carried out at an impeller speed of 400 rpm, and to maintain the pH, a 40% by weight sodium hydroxide solution was added so that the pH was maintained at 11.0. A coprecipitation reaction was carried out for 24 hours to form precursor particles. After separating and washing the precursor particles, they were dried in an oven at 130°C to produce a precursor.

[0134] Ni synthesized by coprecipitation reaction 0.82 Co 0.05 Mn 0.11 Al 0.02 (OH)2 precursor was mixed with Li2CO3 so that the Li / Me (Ni, Co, Mn, Al) molar ratio was 1.03, and heat-treated at 800°C for 10 hours in an oxygen atmosphere to produce a cathode active material containing LiNi 0.82 Co 0.05 Mn 0.11 Al 0.02 O2 lithium composite transition metal oxide.

[0135]

Table 1

[0136] [Experimental Example 1: Observation of Cathode Active Material] Photographs of the cathode active materials produced in Comparative Example 1 and Example 1 observed at high magnification with a scanning electron microscope (SEM) are shown in Figures 1 and 2, respectively.

[0137] [Experimental Example 2: Rolling Density] The rolling density was measured using HPRM-1000. Specifically, after 5 g of the cathode active material of Example 1 and Comparative Example 1 were respectively put into a cylindrical mold, the mold filled with the cathode active material was pressed at 63.694 MPa. Then, the height of the pressed mold was measured with a vernier caliper to obtain the rolling density. The results are shown in Table 1.

[0138] [Experimental Example 3: Average Particle Size] D50 is defined as the particle size at the 50% standard of the particle size distribution and was measured using the laser diffraction method.

[0139] [Experimental Example 4: Crystal Size of Primary Particles] Using Endeavor (CuKα, λ = 1.54 Å) manufactured by Bruker with a LynxEye XE-T position detection element, the sample was measured in the FDS 0.5°, 2θ 15° to 90° region at a step size of 0.02° so that the total scan time was 20 minutes.

[0140] For the measured data, Rietveld analysis was performed considering the charge (the metal at the transition metal site is +3, and Ni at the Li site is +2) and cation mixing from each site. During the crystal size analysis, instrumental broadening was considered using the Fundamental Parameter Approach (FPA) implemented in the TOPAS program of Bruker, and the entire peak in the measurement range was used during fitting. The peak shape was fitted using only the Lorenzian contribution of the FP (First Principle) among the peak types available in TOPAS, and strain was not considered at this time. The crystal size results are shown in Table 1.

[0141] [Experimental Example 5: Comparison of Particle Cracks] The particle size distribution of the initial positive electrode active material was measured using a PSD (Particle Size Distribution) S3500 (manufactured by Microtrac). The measurement method was as follows: 0.02 - 0.05 g of the sample was placed in a vial (10 mL), and about 5 drops of 10 wt% (NaPO3)6 as a dispersant were dropped. Then, the vial was filled with H2O. The prepared vial was sonicated for 2 minutes. To compare with the initial particle size distribution, 3 g of the positive electrode active material was placed in an empty cylinder with a diameter of 2 cm and a height of 5 cm, and pressurized using a powder resistance characteristic device manufactured by Carvar up to 9 tons for measurement. After pressurization at 9 tons, the positive electrode active material was recovered and the PSD was measured by the method described above. The percentage (%) of particles (fine particles of 1 μm or less) cracked after pressurization at 9 tons was calculated by comparing the initial PSD and the PSD after pressurization at 9 tons to compare the degree of particle cracking.

[0142] [Experimental Example 6: Electrode Cross-Section Based on Electrode Density of 3.4 g / cc] Photographs of the electrode cross-section at an electrode density of 3.4 g / cc observed at high magnification with a scanning electron microscope (SEM) are shown in FIGS. 6 and 7, respectively.

[0143] [Experimental Example 7: High-Temperature Life Characteristics of Coin-Type Full Cell] For the lithium secondary battery full cells manufactured as follows using the respective positive electrode active materials produced in Examples 1 and 2 and Comparative Example 1, charging was performed at 45 °C in the CC (CONSTANT CURRENT)-CV (CONSTANT VOLTAGE) mode at 0.7C until 4.25V was reached, and discharging was performed at a constant current of 0.5C until 2.5V. The capacity retention rate when a 300-cycle charge-discharge experiment was conducted was measured to evaluate the life characteristics. The results are shown in FIG. 8.

[0144] Specifically, the lithium secondary battery half cells were manufactured as follows.

[0145] The respective cathode active materials, carbon black conductive materials, and PVdF binders produced in Example 1 and Comparative Example 1 were mixed in a weight ratio of 96:2:2 in an N-methylpyrrolidone solvent to produce a cathode mixture, which was applied to one side of an aluminum current collector, dried at 100 °C, and rolled to produce a cathode.

[0146] Lithium metal was used as the anode.

[0147] An electrode assembly was produced with a porous polyethylene separator interposed between the thus-produced cathode and anode. After positioning the electrode assembly inside the case, an electrolyte was injected into the case to produce a lithium secondary battery. At this time, the electrolyte was produced by dissolving lithium hexafluorophosphate (LiPF6) with a concentration of 1.0 M in an organic solvent composed of ethylene carbonate / ethyl methyl carbonate / diethyl carbonate (mixed volume ratio of EC / EMC / DEC = 3 / 4 / 3).

[0148] [Experimental Example 8: Measurement of Gas Generation Amount] The gas generation amounts of the cathode active materials according to Example 1, 2, and Comparative Example 1 were measured and shown in Fig. 9.

[0149] Specifically, the gas generation amounts were measured as follows.

[0150] Two NCM electrodes charged at a voltage of 4.2 V (full cell standard) (loading amount per side: 380 mg / cm 2 ) and two separator membranes were placed on the lower plate of a coin cell and fixed with a gasket. After that, 400 μl of an electrolyte (DEC REF. (EC / PC / DEC = 3 / 1 / 6, VC / PS = 0.5 / 1 Wt%)) was injected once after evacuation, and each side was vacuum-sealed with a thickness of 0.5 cm using an aluminum pouch with a size of 6.5 × 4.5 cm. Here, the vacuum sealing means that the monolithic cell was vacuum-sealed under the conditions of 95 kPa / 93 kPa. Then, after storing in a convection oven at 60 °C for 12 weeks, the gas generation amount inside the battery was measured. The results are shown in Fig. 9.

[0151] [Experimental Example 9: Measurement of Tap Density] The tap density of the precursor was measured using TAP-2S (trade name, manufacturer: LOGAN) based on ASTM B527-06.

Claims

1. A positive electrode active material for a lithium secondary battery, comprising: at least one secondary particle containing an aggregate of primary large particles, the average particle diameter (D50) of the primary large particles being 2 μm or more, the ratio of the average particle diameter (D50) of the primary large particles to the average crystal size of the primary large particles being 8 or more, the average particle diameter (D50) of the secondary particles being 3 to 10 μm, the secondary particles containing a nickel-based lithium transition metal oxide, when at least one of the secondary particles is rolled at 9 tons in an area of 2 cm in diameter, the primary large particles themselves do not crack, the fine particles of 1 μm or less after rolling the positive electrode active material at 9 tons in an area of 2 cm in diameter being less than 10%, wherein the nickel-based lithium transition metal oxide is Li ａ Ni １－ｘ－ｙ Co ｘ M1 ｙ M2 ｗ O ２ (1.0 ≤ a ≤ 1.5, 0 ≤ x ≤ 0.2, 0 ≤ y ≤ 0.2, 0 ≤ w ≤ 0.1, 0 ≤ x + y ≤ 0.2, M1 is at least one selected from the group consisting of Mn and Al, M2 is at least one selected from the group consisting of Ba, Ca, Zr, Ti, Mg, Ta, Nb, and Mo), a positive electrode active material for a lithium secondary battery.

2. The positive electrode active material for a lithium secondary battery according to claim 1, wherein the average crystal size of the primary large particles is 200 nm or more.

3. The positive electrode active material for a lithium secondary battery according to claim 1 or 2, wherein the ratio of the average particle diameter (D50) of the secondary particles to the average particle diameter (D50) of the primary large particles is 2 to 4.

4. The positive electrode active material for a lithium secondary battery according to any one of claims 1 to 3, further comprising at least one of zirconium, yttrium, and strontium as a firing additive.

5. The positive electrode active material for a lithium secondary battery according to any one of claims 1 to 4, wherein the surface of the positive electrode active material is further coated with a boron-containing substance.

6. The positive electrode active material for a lithium secondary battery according to any one of claims 1 to 5, wherein the surface of the positive electrode active material is further coated with a cobalt-containing substance.

7. A positive electrode for a lithium secondary battery comprising the positive electrode active material for a lithium secondary battery according to claim 1.

8. A lithium secondary battery comprising the positive electrode active material for a lithium secondary battery according to claim 1.

9. A method for manufacturing a positive electrode active material for a lithium secondary battery according to claim 1, comprising: (S1) mixing a nickel-based transition metal oxide precursor having a tap density of 2.0 g / cc or less and a lithium precursor and performing primary firing; and (S2) performing secondary firing on the product of the primary firing.

10. The method for manufacturing a positive electrode active material for a lithium secondary battery according to claim 9, wherein the temperature of the primary firing is 780 to 900°C.

11. The method for producing a positive electrode active material for a lithium secondary battery according to claim 9 or 10, wherein the temperature of the secondary firing is 650 to 800 °C.

12. The method for producing a positive electrode active material for a lithium secondary battery according to any one of claims 9 to 11, which does not include a water washing step between the step (S1) and the step (S2).

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