Positive electrode active material, positive electrode containing the same, and lithium secondary battery

Abstract

The present invention relates to a lithium nickel-based oxide particle having a pseudo-single particle form, which is a single particle consisting of one nodule or a composite of 30 or less nodules, and a coating layer formed on the surface of the lithium nickel-based oxide particle, the coating layer being composed of lithium, nickel, cobalt, and M. a (where M a relates to a positive electrode active material formed using a nano-sized coating precursor that is a chelate complex containing Mn, Al, or a combination thereof.

Description

[Technical Field]

[0001] This application claims priority under Korean Patent Application No. 10-2021-0187148 dated December 24, 2021, and all content disclosed in the said Korean Patent Application is incorporated herein by reference.

[0002] The present invention relates to a positive electrode active material, a positive electrode containing the same, and a lithium secondary battery, and more particularly to a positive electrode active material in single-particle or pseudo-single-particle form, and a positive electrode containing the same and a lithium secondary battery. [Background technology]

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

[0004] Lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), lithium manganese oxide (LiMnO2 or LiMnO4, etc.), and lithium iron phosphate compounds (LiFePO4) have been used as positive electrode active materials for lithium secondary batteries. Of these, lithium cobalt oxide has the advantage of a high operating voltage and excellent capacity characteristics, but the high price of cobalt, the raw material, and its unstable supply make commercial application to high-capacity batteries difficult. Lithium nickel oxide has poor structural stability, making it difficult to achieve sufficient lifespan characteristics. On the other hand, lithium manganese oxide has excellent stability but suffers from poor capacity characteristics. Therefore, in order to complement the problems of lithium transition metal oxides containing Ni, Co, or Mn alone, lithium composite transition metal oxides containing two or more transition metals have been developed, and among them, lithium nickel cobalt manganese oxide containing Ni, Co, and Mn is widely used in the field of electric vehicle batteries.

[0005] Conventional lithium nickel cobalt manganese oxide typically consists of spherical secondary particles formed by the aggregation of tens to hundreds of primary particles. However, in the case of lithium nickel cobalt manganese oxide with such a secondary particle form, particle cracking occurs during the rolling process in the manufacturing of the positive electrode, causing primary particles to detach, and cracks to develop inside the particles during the charge-discharge process. When particle cracking or cracking occurs in the positive electrode active material, the contact area with the electrolyte increases, leading to increased gas generation due to side reactions with the electrolyte and increased degradation of the active material, resulting in a decrease in lifespan characteristics.

[0006] Furthermore, recently, there has been an increasing demand for high-power, high-capacity batteries, such as those for electric vehicles, and consequently, the nickel content in the positive electrode active material tends to gradually increase. When the nickel content in the positive electrode active material increases, the initial capacity characteristics improve, but the high reactivity of nickel increases with repeated charging and discharging cycles. +4 A large amount of ions are generated, causing the structure of the positive electrode active material to break down. As a result, the degradation rate of the positive electrode active material increases, the lifespan characteristics decrease, and the battery safety deteriorates.

[0007] To solve the aforementioned problems, a technique has been proposed to manufacture lithium nickel cobalt manganese oxide in single-particle form rather than secondary particles by increasing the firing temperature during production. In the case of single-particle form positive electrode active material, the contact area with the electrolyte is smaller compared to conventional secondary-particle form positive electrode active material, resulting in fewer side reactions with the electrolyte, superior particle strength, and less particle cracking during electrode manufacturing. Therefore, applying single-particle form positive electrode active material has the advantage of superior gas generation and lifetime characteristics. However, in the case of conventional single-particle form positive electrode active material, there are fewer interfaces between primary particles that serve as pathways for lithium ion movement within the particle, resulting in reduced lithium mobility. Furthermore, because it is manufactured at a relatively high firing temperature, a rock-salt phase is formed on the particle surface, resulting in high surface resistance. Therefore, conventional single-particle form positive electrode active material has the problem of high resistance and inferior output characteristics. [Overview of the Initiative]

Problems to be Solved by the Invention

[0008] The present invention is for solving the above problems, and by forming a coating layer on the surface of a lithium composite transition metal oxide in single-particle or pseudo-single-particle form using a nano-sized coating precursor, it aims to provide a positive electrode active material having excellent life characteristics and excellent resistance and output characteristics.

[0009] Also, the present invention aims to provide a positive electrode and a secondary battery having excellent life characteristics and resistance characteristics by including the above positive electrode active material.

Means for Solving the Problems

[0010] According to one embodiment, the present invention provides a positive electrode active material including lithium nickel-based oxide particles in single-particle form consisting of 1 nodule or a pseudo-single-particle form which is a composite of 30 or fewer nodules, and a coating layer formed on the surface of the lithium nickel-based oxide particles, wherein the coating layer is formed using a nano-sized coating precursor which is a chelate complex containing lithium, nickel, cobalt, and M a (where M a is Mn, Al, or a combination thereof).

[0011] According to another embodiment, the present invention provides a positive electrode active material including lithium, nickel, cobalt, and M a (where M aThe present invention provides a method for producing a positive electrode active material, comprising: a first step of reacting a metal solution containing Mn, Al, or a combination thereof with a coating precursor production solution containing a chelating agent to produce a nano-sized coating precursor; and a second step of dry mixing lithium nickel-based oxide particles in a pseudo-single particle form, which are single particles consisting of one nodule or composites of 30 or fewer nodules, with the coating precursor, and then firing to form a coating layer.

[0012] According to further embodiments, the present invention provides a positive electrode and a lithium secondary battery comprising the positive electrode active material according to the present invention. [Effects of the Invention]

[0013] The positive electrode active material according to the present invention contains lithium nickel-based oxide particles in single-particle or pseudo-single-particle form with excellent particle strength. During electrode manufacturing, particle cracking and cracking due to rolling are minimized, resulting in less gas generation due to side reactions with the electrolyte and less degradation of the positive electrode active material, thereby achieving excellent lifespan and high-temperature characteristics.

[0014] Furthermore, the positive electrode active material according to the present invention can form a coating layer using a nano-sized coating precursor synthesized by a polyol process, thereby uniformly and thinly forming a coating layer of nano-thickness on the surface of lithium nickel oxide particles. When a uniform and thin coating layer is formed in this way, the contact area with the electrolyte is reduced, and highly reactive Ni is present on the surface of the positive electrode active material. +4 This minimizes ion exposure and improves the structural stability of the positive electrode active material.

[0015] Furthermore, the coating layer according to the present invention is extremely thin, at the nanoscale, and has a layered lithium transition metal oxide composition, containing a relatively high amount of cobalt, which has excellent power and resistance characteristics. This allows for smooth insertion and removal of lithium on the surface of the positive electrode active material, resulting in improved resistance and power characteristics. [Brief explanation of the drawing]

[0016] [Figure 1] This graph shows the resistance characteristics of secondary batteries using the positive electrode active materials produced according to the examples and comparative examples. [Figure 2] This graph shows the life characteristics of secondary batteries using the positive electrode active materials produced according to the examples and comparative examples. [Modes for carrying out the invention]

[0017] The present invention will be described in more detail below.

[0018] The terms and words used herein and in the claims should not be interpreted in a manner limited to their ordinary or dictionary meanings, but rather in a manner consistent with the technical idea of ​​the present invention, in accordance with the principle that inventors may define the concepts of terms as appropriate to best describe their invention.

[0019] In this invention, "single particle" means a particle consisting of one nodule.

[0020] The aforementioned "nodule" refers to a sub-particle unit that constitutes a single particle or pseudo-single particle, and can be either a single crystal without grain boundaries, or a polycrystalline material that appears to have no grain boundaries when observed with a scanning electron microscope at a field of view of 5,000 to 20,000 times magnification.

[0021] The aforementioned "pseudo-single particle" refers to a composite formed by the aggregation of 30 or fewer, preferably 2 to 30, nodules.

[0022] In this invention, "secondary particle" means a particle formed by the aggregation of tens to hundreds of primary particles. Specifically, a secondary particle is an aggregate of 50 or more primary particles. In this invention, "particle" is a concept that includes one or all of the following: single particle, pseudo-single particle, primary particle, nodule, and secondary particle.

[0023] In this invention, "average particle size D 50 " refers to the particle size at the 50% reference level of the volume cumulative particle size distribution of the powder being measured (e.g., coating precursor or cathode active material powder). The average particle size D 50 This can be measured using the laser diffraction method. For example, after dispersing the powder to be measured in a dispersion medium, it can be introduced into a commercially available laser diffraction particle size analyzer (e.g., Microtrac MT 3000), irradiated with ultrasound at approximately 28 kHz with an output of 60 W, and then measured by obtaining a volume-cumulative particle size distribution graph and determining the particle size corresponding to 50% of the volume-cumulative amount.

[0024] In this invention, "crystallite" refers to a particle unit having substantially the same crystal orientation, which can be confirmed by EBSD (Electron Backscatter Diffraction) analysis. Specifically, it refers to the smallest particle unit represented by the same color in an IPF map obtained by EBSD analysis of a cross-section of a positive electrode active material cut by ion milling.

[0025] On the other hand, in this invention, the "average crystallite diameter" can be quantitatively analyzed using X-ray diffraction analysis (XRD) with Cu-Kα X-rays. Specifically, the average crystal grain size can be quantitatively analyzed by placing the particles to be measured in a holder, irradiating the particles with X-rays, and analyzing the diffraction grating output. For sampling, a powder sample of the particles to be measured was placed in the recessed groove in the center of a general powder holder, the surface was made uniform using a glass slide, and the height of the sample was adjusted to match the periphery of the holder. Subsequently, X-ray diffraction analysis was performed using a Bruker D8 Endeavor (light source: Cu Kα, λ=1.54Å) equipped with a LynxEye XE-T position-sensitive detector, under the conditions of FDS 0.5°, 2θ=15°~90°, step size 0.02°, and total scan time of approximately 20 minutes. For the measured data, Rietveld refinement was performed, taking into account the charge at each site (metal ions at transition metal sites were +3, and Ni ions at Li sites were +2) and cation mixing. During grain size analysis, instrumental brodadening was considered using the Fundamental Parameter Approach (FPA) implemented in the Bruker TOPAS program, and the entire peak of the measurement range was used during fitting. For peak shape, only the Lorenzian contribution (FP) was used as the First Principle (FP) among the peak types available in TOPAS for fitting, and stress was not considered.

[0026] In this invention, the "specific surface area" is measured by the BET method, and specifically, it can be calculated from the amount of nitrogen gas adsorbed at liquid nitrogen temperature (77K) using BELSORP-mino II manufactured by BEL Japan.

[0027] positive electrode active material The positive electrode active material according to the present invention will be described below.

[0028] The positive electrode active material according to the present invention comprises (1) lithium nickel-based oxide particles in single particle or pseudo-single particle form, and (2) a coating layer formed on the surface of the lithium nickel-based oxide particles.

[0029] (1) Lithium nickel oxide particles The lithium nickel oxide particles are single particles consisting of one nodule or pseudo-single particles which are composites of 30 or fewer nodules, preferably 2 to 30, more preferably 2 to 20.

[0030] These single-particle or pseudo-single-particle lithium nickel oxide particles have higher particle strength compared to existing secondary-particle lithium nickel oxides in which tens to hundreds of primary particles are aggregated, resulting in less particle cracking during rolling.

[0031] Furthermore, in the case of lithium nickel-based oxides in single-particle or pseudo-single-particle form according to the present invention, the number of nodules constituting the particles is small, resulting in less change due to volume expansion and contraction of the nodules during charging and discharging. This significantly reduces the occurrence of cracks inside the particles.

[0032] On the other hand, the lithium nickel oxide particles may have a composition in which the nickel content of the total metals other than lithium is 70 mol% or more, preferably 80 mol% or more, and more preferably 82 mol% or more. Specifically, they may be lithium nickel cobalt manganese oxides in which the nickel content of the total metals other than lithium is 70 mol% or more, preferably 80 mol% or more, and more preferably 82 mol% or more. When the nickel content in the lithium nickel oxide particles satisfies the above range, a high energy density can be achieved.

[0033] More specifically, the lithium nickel-based oxide particles can have a composition represented by the following [Chemical Formula 1].

[0034] [Chemical Formula 1] Li a Ni b Co c M 1 d M 2 e O2

[0035] In the above Chemical Formula 1, M 1 can be Mn, Al, or a combination thereof, and preferably can be Mn or Mn and Al.

[0036] The M 2 is one or more selected from the group consisting of Zr, W, Y, Ba, Ca, Ti, Mg, Ta, and Nb, and preferably can be one or more selected from the group consisting of Zr, Y, Mg, and Ti, and more preferably can be Zr, Y, or a combination thereof. The M 1 element is not necessarily included, but when included in an appropriate amount, it can play a role in promoting grain growth during firing or improving crystal structure stability.

[0037] The a represents the molar ratio of lithium in the lithium nickel-based oxide, and can be 0.8 ≤ a ≤ 1.2, 0.85 ≤ a ≤ 1.15, or 0.9 ≤ a ≤ 1.2. When the molar ratio of lithium satisfies the above range, the crystal structure of the lithium nickel-based oxide can be stably formed.

[0038] The b represents the molar ratio of nickel among all the metals other than lithium in the lithium nickel-based oxide, and can be 0.7 ≤ b < 1, 0.8 ≤ b < 1, or 0.82 ≤ b < 1. When the molar ratio of nickel satisfies the above range, it shows a high energy density and enables the realization of a high capacity.

[0039] The c represents the molar ratio of cobalt among all the metals other than lithium in the lithium nickel-based oxide, and can be 0 < c < 0.3, 0 < c < 0.2, or 0.01 ≤ c ≤ 0.15. When the molar ratio of cobalt satisfies the above range, good resistance characteristics and output characteristics can be realized.

[0040] The d represents the molar ratio of element M among all the metals other than lithium in the lithium nickel-based oxide, and can be 0 < d < 0.3, 0 < d < 0.2, or 0.01 ≤ d ≤ 0.15. 1 When the molar ratio of element M satisfies the above range, the structural stability of the positive electrode active material 1 is achieved. Excellent

[0041] The e represents the molar ratio of element M among all the metals other than lithium in the lithium nickel-based oxide, and can be 0 ≤ e ≤ 0.2, 0 ≤ e ≤ 0.1, or 0 ≤ e ≤ 0.05. [[ID=I5]] 2

[0042] [[ID=1I9]] (2) Coating layer The positive electrode active material according to the present invention includes a coating layer on the surface of the lithium nickel-based oxide particles in the above-described single particle or pseudo-single particle form.

[0043] The coating layer is formed using a nano-sized coating precursor, where the nano-sized coating precursor is a chelate complex containing lithium, nickel, cobalt, and M a (where M a is Mn, Al, or a combination thereof), and specifically, can be a chelate complex containing lithium, nickel, cobalt, and M a (where M a is Mn, Al, or a combination thereof), and more specifically, can be a chelate complex containing lithium, nickel, cobalt, and manganese. The synthesis method of the coating precursor will be specifically described in the manufacturing method of the positive electrode active material.

[0044] ​​ In the case of high-nickel cathode active materials with a high nickel content, there is a problem in that side reactions with the electrolyte occur on the surface of the cathode active material where it comes into contact with the electrolyte, resulting in the leaching of transition metals and structural collapse. Conventionally, to solve this problem, a method has been used in which metal oxides such as Al or boron are coated on the surface of the high-nickel cathode active material to reduce contact with the electrolyte. However, since such coating layers are electrically inactive, forming a coating layer on the surface of the active material increases the resistance of the cathode active material, and the increase in resistance becomes more severe as the thickness of the coating layer increases. In particular, in the case of single-particle cathode active materials, which are inherently highly resistive, applying a conventional coating layer to the surface of a single-particle cathode active material causes a more serious problem of power reduction due to increased resistance.

[0045] However, according to the inventors' research, lithium, nickel, cobalt, and M synthesized by the polyol process as in the present invention are obtained. a (Here, Ma a It has been shown that when coating is performed using a chelate complex containing Mn, Al, or a combination thereof as a coating precursor, side reactions with the electrolyte can be effectively suppressed and the resistance characteristics of the positive electrode active material can be improved. This is because the chelate complex synthesized by the polyol process has a very small particle size at the nanometer level, and when coating is performed using it, a thin coating layer at the nanometer level is uniformly formed over the entire surface of the lithium nickel oxide particles, blocking contact between the electrolyte and the core portion with a high nickel content. Furthermore, the metal elements contained in the chelate complex form a layered coating layer after firing, which facilitates the insertion and removal of lithium, thereby increasing lithium mobility.

[0046] The coating precursor used in the present invention has an average particle size (D 50The particle size can be 1 nm to 500 nm. The average particle size of the coating precursor is preferably 5 nm to 300 nm, and more preferably 10 nm to 150 nm. When the average particle size of the coating precursor is within the above range, a thin and uniform coating layer can be formed.

[0047] On the other hand, a coating layer formed using the above-mentioned coating precursor may have a layered lithium nickel cobalt oxide composition, where it is preferable that the lithium nickel cobalt oxide has a lower nickel content compared to the lithium nickel oxide particles described above. If the nickel content of the coating layer is high, highly reactive Ni will be present on the surface. +4 This is because a large amount of ions may be generated, potentially reducing the structural stability of the positive electrode active material. Preferably, the nickel content among all metals other than lithium in the coating layer can be 60 mol% or less.

[0048] Specifically, the coating layer may have a composition represented by the following [Chemical Formula 2].

[0049] [Chemical formula 2] Li x Ni y Co z M a w M b p O 2-q

[0050] In the above chemical formula 2, M a This can be Mn, Al, or a combination thereof, preferably Mn or Mn and Al.

[0051] M b This is one or more elements selected from the group consisting of Zr, W, Y, Ba, Ca, Ti, Mg, Ta, and Nb, and preferably one or more elements selected from the group consisting of Al, Zr, Y, Mg, and Ti.

[0052] 0.5 ≤ x ≤ 1.05, 0 <y≦0.6、0<z<0.4、0<w<0.4、0≦p≦0.2、0≦q≦0.5である。

[0053] The aforementioned x represents the molar ratio of lithium in the coating layer and can be 0.5 ≤ x ≤ 1.05, 0.6 ≤ x ≤ 1.05, or 0.6 ≤ x ≤ 1.0.

[0054] The aforementioned y represents the molar ratio of nickel among the total metals other than lithium in the coating layer, and 0 <y≦0.6、0.1≦y≦0.6、または0.3≦y≦0.6であることができる。

[0055] The aforementioned z represents the molar ratio of cobalt among all metals other than lithium in the coating layer, and 0 <z<0.4、0.05≦z<0.4、または0.1≦z<0.4であることができる。

[0056] The aforementioned w is M of the total metals other than lithium in the coating layer. a The molar ratio of the elements is shown, 0 <w<0.4、0.05≦w<0.4、または0.1≦w<0.4であることができる。

[0057] The aforementioned p is M of the total metals other than lithium in the coating layer. b This indicates the molar ratio of elements and can be 0 ≤ p ≤ 0.2, 0 ≤ p ≤ 0.1, or 0 ≤ p ≤ 0.05.

[0058] The aforementioned 2-q represents the molar ratio of oxygen in the coating layer, and can be 0 ≤ q ≤ 0.5 or 0 ≤ q ≤ 0.4.

[0059] When the coating layer has the composition represented by [Chemical Formula 2], the resistance characteristics and lifespan characteristics are superior.

[0060] On the other hand, the coating layer can have a thickness of 1 nm to 500 nm. Preferably, the thickness of the coating layer can be 10 nm to 200 nm, and more preferably 20 nm to 50 nm. When the thickness of the coating layer is within the above range, the coating layer can not act as a low-antibody, and excellent uniformity of the surface coating can be achieved.

[0061] On the other hand, the positive electrode active material according to the present invention can have an average particle size of nodules of 0.5 μm to 3 μm, preferably 0.8 μm to 2.5 μm, and more preferably 0.8 μm to 1.5 μm. When the average particle size of the nodules satisfies the above range, a positive electrode active material in the form of single particles or pseudo-single particles with excellent electrochemical properties can be formed. If the average particle size of the nodules is too small, the number of aggregated nodules forming lithium nickel oxide particles increases, reducing the effect of suppressing particle cracking during rolling. If the average particle size of the nodules is too large, the lithium diffusion path inside the nodule becomes longer, increasing resistance and potentially degrading the output characteristics.

[0062] Furthermore, the positive electrode active material has an average particle size D 50 The diameter can be 2 μm to 6 μm, preferably 2 μm to 5 μm, and more preferably 3 μm to 5 μm. D of the positive electrode active material 50 If it is too small, the specific surface area of ​​the active material increases, which requires an increase in the amount of conductive material, thus reducing the density of the electrode, lowering the solid content of the electrode slurry, which can reduce productivity during electrode manufacturing, and also reduces electrolyte impregnation, leading to a decrease in electrochemical properties. 50 If the value is too large, the resistance increases, leading to a problem of reduced output characteristics.

[0063] Furthermore, the positive electrode active material can have an average crystallite diameter of 150 nm to 300 nm, 200 nm to 280 nm, or 230 nm to 280 nm. When the average crystallite diameter satisfies the above range, the formation of the rock salt phase is reduced during the production of lithium nickel oxide, and a positive electrode active material in the form of a single particle or pseudo-single particle with excellent resistance characteristics can be produced. Generally, positive electrode active materials in the form of a single particle or pseudo-single particle are produced by increasing the firing temperature to increase the size of the nodule. However, if only the size of the nodule is increased while the crystallite diameter is small, there is a problem in that a rock salt phase is formed on the surface of the nodule, increasing the resistance. However, when both the average crystallite diameter and the average particle size of the nodule are increased, the formation of the rock salt phase is minimized, and the effect of suppressing the increase in resistance can be obtained.

[0064] As described above, when a secondary battery is manufactured by applying the positive electrode active material of the present invention, which includes a coating layer formed using a nano-sized coating precursor on the surface of lithium nickel-based oxide particles in single-particle or pseudo-single-particle form, excellent life characteristics, resistance characteristics, and output characteristics can all be achieved.

[0065] Method for manufacturing positive electrode active material Next, a method for producing a positive electrode active material according to the present invention will be described.

[0066] The method for producing a positive electrode active material according to the present invention is (1) lithium, nickel, cobalt, and M a (Here, M a The method comprises (1) a first step of reacting a coating precursor manufacturing solution containing a metal solution (containing Mn, Al, or a combination thereof) and a chelating agent to produce a nano-sized coating precursor, and (2) a second step of dry mixing the coating precursor with lithium nickel-based oxide particles in a pseudo-single particle form, which is a single particle consisting of one nodule or a composite of 30 or fewer nodules, and then firing to form a coating layer.

[0067] The steps of the present invention will be described in detail below.

[0068] (1) Step 1 The first step is to remove metal ions (i.e., lithium, nickel, cobalt, M) contained in the coating layer. a Selectively, M b This step involves reacting a metal solution containing a chelating agent with a coating precursor manufacturing solution to produce a coating precursor, which is a complex in which metal ions and a chelating agent are bound.

[0069] The aforementioned metal solution can be produced by dissolving a metal-containing material, such as a nickel-containing raw material, a cobalt-containing raw material, a manganese-containing raw material, an aluminum-containing raw material, or a lithium-containing raw material, in a solvent such as water.

[0070] Here, the nickel-containing raw material can be nickel acetate, carbonate, nitrate, sulfate, halide, sulfide, or oxide, and the cobalt-containing raw material can be cobalt metal acetate, carbonate, nitrate, sulfate, halide, sulfide, or oxide. Furthermore, the manganese-containing raw material can be manganese acetate, carbonate, nitrate, sulfate, halide, sulfide, or oxide, and the lithium-containing raw material can be lithium acetate, carbonate, nitrate, sulfate, halide, sulfide, or oxide.

[0071] The nickel-containing raw material may, but is not limited to, Ni(CH3COO)2·4H2O, NiO, NiCO3·2Ni(OH)2·4H2O, NiC2O2·2H2O, Ni(NO3)2·6H2O, NiSO4, NiSO4·6H2O, nickel halides, or combinations thereof.

[0072] The cobalt-containing raw material may, but is not limited to, Co(CH3COO)2·4H2O, CoSO4, Co(OCOCH3)2·4H2O, Co(NO3)2·6H2O, CoSO4·7H2O, or a combination thereof.

[0073] The manganese-containing raw material may, but is not limited to, Mn(CH3COO)2·4H2O, Mn2O3, MnO2, Mn3O4, MnCO3, Mn(NO3)2, MnSO4, manganese acetate, manganese halides, or combinations thereof.

[0074] The aluminum-containing raw material can be, for example, Al2O3, Al(OH)3, Al(NO3)3, Al2(SO4)3, (HO)2AlCH3CO2, HOAl(CH3CO2)2, Al(CH3CO2)3 aluminum halides, or combinations thereof.

[0075] The lithium-containing raw material may, but is not limited to, lithium carbonate, lithium hydroxide hydrate (LiOH·H2O), lithium hydroxide, lithium nitrate (LiNO3), lithium chloride (LiCl), or a combination thereof.

[0076] The aforementioned metal solution is M b It may further contain metal-containing raw material substances. Here, the M b The metal can be one or more selected from the group consisting of Zr, W, Y, Ba, Ca, Ti, Mg, Ta, and Nb. Here, the M b Metal-containing raw materials are M b These can be metal acetates, carbonates, nitrates, sulfates, halides, sulfides, or oxides.

[0077] On the other hand, nickel-containing raw materials, cobalt-containing raw materials, manganese-containing raw materials, aluminum-containing raw materials, lithium-containing raw materials, M bThe content of metal-containing raw materials and other substances can be appropriately adjusted considering the composition of the coating layer to be manufactured.

[0078] The chelating agent may be a Lewis acid compound comprising one or more selected from the group consisting of a carboxylic acid group and a nitrogen element. In the case of a carboxylic acid group, the anion of the carboxylate formed by the oxidation of the carboxylic acid group in the coating precursor manufacturing solution can form a complex with a metal ion, and in the case of a nitrogen element, the lone pair of electrons of the nitrogen element can form a complex with a metal ion.

[0079] The chelating agent can preferably be one or more selected from the group consisting of citric acid, polyvinylpyrrolidone, and glycolic acid, and more preferably citric acid and / or polyvinylpyrrolidone. In this case, the formation of a complex with metal ions can be facilitated.

[0080] The coating precursor manufacturing solution can be produced by adding a metal solution containing ions contained in the coating layer and the chelating agent to a solvent and then mixing them. The solvent for the coating precursor manufacturing solution can be one or more selected from the group consisting of ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, and 2,3-butanediol. The solvent for the coating precursor manufacturing solution can preferably be diethylene glycol and / or triethylene glycol.

[0081] Once a coating precursor manufacturing solution containing the metal ions and a chelating agent is prepared, the coating precursor manufacturing solution is reacted at a high temperature under reflux to obtain a solution containing a complex formed by the coordination bonding of the metal ions and the chelating agent. Subsequently, the solution containing the complex is washed with ethanol using a centrifuge to separate only the complex, which is then dried to obtain the coating precursor.

[0082] The reaction in the first step can be carried out at 200°C to 300°C, preferably 200°C to 250°C. Specifically, the coating precursor production solution can be reacted under reflux at 200°C to 300°C, preferably 200°C to 250°C for 1 to 5 hours. When the reaction is carried out at a temperature within this range, a complex can be easily formed.

[0083] On the other hand, when the metal solution contains Ni, Co, Mn, and Li ions, reacting the metal solution with a coating precursor manufacturing solution containing a chelating agent results in the Ni and Co ions being reduced and agglomerating to form clusters, while the Mn and Li ions are located around these clusters. As a result, after the reaction is complete, the product is washed using a centrifuge and then dried to obtain a coating precursor in which Ni and Co are present in the core portion, and Mn, Li, and the chelating agent are bound to the upper part of the core portion.

[0084] The coating precursor produced as described above has an average particle size (D 50 The particle size can be 1 nm to 500 nm. The average particle size of the coating precursor can preferably be 5 nm to 300 nm, and more preferably 10 nm to 150 nm. When the average particle size of the coating precursor is within the above range, excellent uniformity of the surface coating can be achieved.

[0085] (2) Step 2 The second step involves dry mixing the coating precursor produced in the first step with lithium nickel oxide particles in single-particle or pseudo-single-particle form, and then firing the mixture to form a coating layer on the surface of the particles.

[0086] According to the manufacturing method of the present invention, by using a coating precursor which is a nano-sized chelate complex in which metal ions and a chelating agent are bonded, a uniform coating layer can be formed even in a dry coating process.

[0087] Specifically, according to the manufacturing method of the present invention, the surface of the lithium nickel oxide particles can be completely surrounded by the coating layer. That is, the surface of the particles can be formed so that it is not exposed to the outside.

[0088] In the second step, the firing can be carried out at 800°C to 900°C. The firing can be carried out for 5 to 15 hours. In this case, the diffusion between particles is improved, and a uniform coating layer can be formed.

[0089] Specifically, the firing can be carried out by raising the temperature from 800°C to 900°C at a rate of 5°C / min to 10°C / min. The firing can be carried out for 5 to 15 hours. When the temperature is raised all at once while maintaining a constant heating rate to the firing temperature, the coating precursors are not fired independently and individual particles are not formed, and a uniform coating layer can be formed on the surface of the lithium nickel oxide particles.

[0090] By the method described above, it is possible to uniformly form a coating layer having a specific composition, even though it is a dry coating, and to produce a positive electrode active material with improved structural stability.

[0091] positive electrode Next, the positive electrode according to the present invention will be described.

[0092] The positive electrode according to the present invention includes a positive electrode active material layer containing the positive electrode active material according to the present invention. Specifically, the positive electrode includes a positive electrode current collector and a positive electrode active material layer formed on the positive electrode current collector and containing the positive electrode active material.

[0093] In the positive electrode, the positive electrode current collector is not particularly limited as long as it does not cause chemical changes in the battery and is conductive. For example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel with surface treatment using carbon, nickel, titanium, silver, etc., can be used. The positive electrode current collector can usually have a thickness of 3 to 500 μm, and fine irregularities can be formed on the surface of the positive electrode current collector to increase the adhesion strength of the positive electrode active material. For example, it can be used in various forms such as film, sheet, foil, mesh, porous material, foam, nonwoven fabric.

[0094] Furthermore, the positive electrode active material layer may include a conductive material and a binder in addition to the positive electrode active material described above.

[0095] The conductive material is used to impart conductivity to the electrodes and can be used without particular limitations in the battery it is configured in, as long as it does not cause chemical changes and has electronic conductivity. Specific examples include graphite such as natural graphite or artificial graphite; carbon-based materials such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, carbon fiber, and carbon nanotubes; metal powders or metal fibers such as copper, nickel, aluminum, and silver; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives. One of these alone or a mixture of two or more can be used. The conductive material can usually be contained in an amount of 1 to 30% by weight, preferably 1 to 20% by weight, and more preferably 1 to 10% by weight, relative to the total weight of the positive electrode active material layer.

[0096] The binder plays a role in improving the adhesion between positive electrode active material particles and the adhesion between the positive electrode active material and the positive electrode current collector. Specific examples include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer rubber (EPDM rubber), sulfonated EPDM, styrene-butadiene rubber (SBR), fluororubber, or various copolymers thereof, of which one or more can be used. The binder may be present in an amount of 1 to 30% by weight, preferably 1 to 20% by weight, and more preferably 1 to 10% by weight, relative to the total weight of the positive electrode active material layer.

[0097] The positive electrode can be manufactured by a conventional method for manufacturing a positive electrode. For example, the positive electrode can be manufactured by mixing a positive electrode active material, a binder, and / or a conductive material in a solvent to produce a positive electrode slurry, applying the positive electrode slurry onto a positive electrode current collector, and then drying and rolling it.

[0098] The solvent can be any solvent commonly used in the art, such as dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, or water, and one of these alone or a mixture of two or more can be used. The amount of solvent used should be such that it dissolves or disperses the positive electrode active material, conductive material, and binder, and has a viscosity that allows for excellent thickness uniformity when applied for the manufacture of the positive electrode, taking into consideration the coating thickness of the slurry and the manufacturing yield.

[0099] Alternatively, the positive electrode can be manufactured by casting the positive electrode slurry onto another support, peeling it off the support, and then laminating the resulting film onto the positive electrode current collector.

[0100] Lithium-ion battery Next, the lithium secondary battery according to the present invention will be described.

[0101] The lithium secondary battery of the present invention includes the positive electrode according to the present invention. Specifically, the lithium secondary battery includes a positive electrode, a negative electrode positioned opposite the positive electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte, wherein the positive electrode is as described above. The lithium secondary battery may further optionally include a battery container for housing the electrode assembly of the positive electrode, negative electrode, and separator, and a sealing member for sealing the battery container.

[0102] In the lithium secondary battery described above, the negative electrode includes a negative electrode current collector and a negative electrode active material layer located on the negative electrode current collector.

[0103] The negative electrode current collector is not particularly limited as long as it does not cause chemical changes in the battery and has high conductivity. For example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel with surface treatment using carbon, nickel, titanium, silver, etc., and aluminum-cadmium alloys can be used. The negative electrode current collector can usually have a thickness of 3 to 500 μm, and, similar to the positive electrode current collector, fine irregularities can be formed on the surface of the current collector to strengthen the bonding force of the negative electrode active material. For example, it can be used in various forms such as film, sheet, foil, mesh, porous material, foam, and nonwoven fabric.

[0104] The negative electrode active material layer selectively includes a binder and a conductive material together with the negative electrode active material.

[0105] As the negative electrode active material, compounds capable of reversible intercalation and deintercalation of lithium can be used. Specific examples include carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber, and amorphous carbon; metallic compounds capable of alloying with lithium, such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloys, Sn alloys, or Al alloys; and SiO2. β Examples include (0<β<2), SnO2, vanadium oxide, lithium vanadium oxide, and other metal oxides that can be doped and dedoped with lithium; or composites containing the metallic compound and carbonaceous material, such as Si-C composites or Sn-C composites, and one or more mixtures of these can be used.

[0106] Furthermore, a metallic lithium thin film may be used as the negative electrode active material. In addition, both low-crystallinity carbon and high-crystallinity carbon can be used as carbon materials. Typical low-crystallinity carbons include soft carbon and hard carbon, while typical high-crystallinity carbons include amorphous, plate-like, flaky, spherical or fibrous natural or artificial graphite, Kish graphite, pyrolytic carbon, mesophase pitch-based carbon fiber, meso-carbon microbeads, mesophase pitches, and high-temperature calcined carbon such as petroleum or coal tar pitch-derived cokes.

[0107] The conductive material is used to impart conductivity to the electrodes and can be used without particular limitations in the battery it is configured in, as long as it does not cause chemical changes and has electronic conductivity. Specific examples include graphite such as natural graphite or artificial graphite; carbon-based materials such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, carbon fiber, and carbon nanotubes; metal powders or metal fibers such as copper, nickel, aluminum, and silver; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives. One of these alone or a mixture of two or more can be used. The conductive material can usually be contained in an amount of 1 to 30% by weight, preferably 1 to 20% by weight, and more preferably 1 to 10% by weight, relative to the total weight of the negative electrode active material layer.

[0108] The binder plays a role in improving adhesion between negative electrode active material particles and adhesion between the negative electrode active material and the negative electrode current collector. Specific examples include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer rubber (EPDM rubber), sulfonated EPDM, styrene-butadiene rubber (SBR), fluororubber, or various copolymers thereof, of which one or more can be used. The binder may be present in an amount of 1 to 30% by weight, preferably 1 to 20% by weight, and more preferably 1 to 10% by weight, relative to the total weight of the negative electrode active material layer.

[0109] The negative electrode active material layer can also be manufactured, for example, by applying a negative electrode slurry containing a negative electrode active material and selectively a binder and conductive material onto a negative electrode current collector and drying it, or by casting the negative electrode slurry onto another support, peeling it off this support, and then laminating the resulting film onto the negative electrode current collector.

[0110] On the other hand, in the lithium secondary battery, the separator separates the negative electrode and the positive electrode and provides a passage for lithium ions to move. Any separator commonly used in lithium secondary batteries can be used without particular limitations, but those with low resistance to ion movement of the electrolyte and excellent moisture-absorbing capacity for the electrolyte are particularly preferred. Specifically, porous polymer films, such as ethylene homopolymers, propylene homopolymers, ethylene / butene copolymers, ethylene / hexene copolymers, and ethylene / methacrylate copolymers, or laminated structures of two or more layers thereof, can be used. Alternatively, ordinary porous nonwoven fabrics, such as nonwoven fabrics made of high-melting-point glass fibers or polyethylene terephthalate fibers, may be used. Furthermore, coated separators containing ceramic components or polymeric substances may be used to ensure heat resistance or mechanical strength, and can be selectively used as single-layer or multi-layer structures.

[0111] Furthermore, the electrolytes used in the present invention include, but are not limited to, organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel-type polymer electrolytes, solid inorganic electrolytes, and molten inorganic electrolytes that can be used in the manufacture of lithium secondary batteries.

[0112] Specifically, the electrolyte may include an organic solvent and a lithium salt.

[0113] The organic solvent can be used without particular limitations as long as it serves as a medium through which ions involved in the electrochemical reaction of the battery can move. Specifically, the organic solvents 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; dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (MEC), ethyl methyl carbonate (EMC), ethylene carbonate (EC), and propylene carbonate (propylene Carbonate solvents such as carbonate (PC); alcoholic solvents such as ethyl alcohol and isopropyl alcohol; nitriles such as R-CN (where R is a C2-C20 linear, branched, or cyclic hydrocarbon group, which can include a double-bonded aromatic ring or ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; or sulfolanes can be used. Among these, carbonate solvents are preferred, and a mixture of a cyclic carbonate (e.g., ethylene carbonate or propylene carbonate) having high ionic conductivity and high dielectric constant that can improve the charge and discharge performance of the battery, and a low-viscosity linear carbonate compound (e.g., ethyl methyl carbonate, dimethyl carbonate, or diethyl carbonate) is more preferred.

[0114] The lithium salt can be used without particular limitations as long as it is a compound that can provide lithium ions for use in lithium secondary batteries. 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 is preferably used within the range of 0.1 to 5.0 M, more preferably 0.1 to 3.0 M. When the concentration of the lithium salt falls within this range, the electrolyte can exhibit excellent electrolyte performance due to having appropriate conductivity and viscosity, and lithium ions can move effectively.

[0115] In addition to the electrolyte components, the electrolyte may further contain additives for purposes such as improving battery life characteristics, suppressing battery capacity reduction, and improving battery discharge capacity. For example, the additives may be, but are not limited to, haloalkylene carbonate compounds such as difluoroethylene carbonate, pyridine, triethyl phosphite, triethyl alcoholamine, cyclic ether, ethylenediamine, n-glyme, hexamethyl phosphate triamide, nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinone, N,N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2-methoxyethyl alcohol, or aluminum trichloride, either alone or in combination. The additives may be present in an amount of 0.1 to 10% by weight, preferably 0.1 to 5% by weight, relative to the total weight of the electrolyte.

[0116] As described above, lithium secondary batteries containing the positive electrode active material according to the present invention exhibit excellent discharge capacity, output characteristics, and capacity retention rate stably, making them useful in portable devices such as mobile phones, notebook computers, and digital cameras, as well as in the field of electric vehicles such as hybrid electric vehicles (HEVs).

[0117] Accordingly, according to another embodiment of the present invention, a battery module including the lithium secondary battery as a unit cell and a battery pack including the same are provided.

[0118] The aforementioned battery module or battery pack can be used as a power source for one or more medium-to-large devices, including power tools; electric vehicles (EVs), hybrid electric vehicles, and plug-in hybrid electric vehicles (PHEVs); or power storage systems.

[0119] Hereinafter, embodiments of the present invention will be described in detail so that those with ordinary skill in the art to which the present invention pertains can easily implement it. However, the present invention can be realized in a variety of different forms and is not limited to the embodiments described herein.

[0120] Examples <Manufacturing of coating precursors> An aqueous transition metal acetate solution was prepared by mixing 0.012 mol of Ni(CH3COO)2·4H2O, 0.006 mol of Co(CH3COO)2·4H2O, and 0.012 mol of Mn(CH3COO)2·4H2O. 0.0345 mol of LiOH·H2O and 0.045 mol of citric acid (a chelating agent) were added to 80 ml of triethylene glycol as a solvent. After mixing, the mixture was reacted under reflux at 230°C for 3 hours to obtain a solution containing complexes in which Ni, Co, Mn, Li, and the chelating agent were bound. The solution containing the complexes was separated by washing with ethanol using a centrifuge, and then dried at 80°C to obtain an average particle size (D 50 A coating precursor with a density of 100 nm was obtained.

[0121] <Manufacturing of lithium nickel oxides> Four liters of distilled water were placed in a coprecipitation reactor (capacity 20 L), and then 100 mL of a 28 wt% aqueous ammonia solution was added while maintaining a temperature of 50°C. Subsequently, a transition metal solution prepared by mixing NiSO4, CoSO4, and MnSO4 in a nickel:cobalt:manganese molar ratio of 87:5:8, an aqueous ammonia solution, and a sodium hydroxide solution were added to the coprecipitation reactor to form a precursor. The precursor particles were separated and washed, and then dried in an oven at 130°C to produce the precursor.

[0122] The precursor synthesized by the coprecipitation reaction, LiOH, and aluminum hydroxide were mixed so that the molar ratio of Ni+Co+Mn:Al:Li was 99:1:1.05, and the mixture was heat-treated in an oxygen atmosphere at 850°C for 12 hours to obtain Li[Ni 0.86 Co 0.05 Mn 0.08 Al 0.01 O2 was produced. The produced lithium nickel oxide was in single-particle and / or pseudo-single-particle form, with an average primary particle size of 2.1 μm, an average secondary particle size of 4.13 μm, and an average crystallite size of 280 nm.

[0123] After dry mixing the single-particle lithium nickel oxide produced as described above with the coating precursor, the temperature is increased from 25°C to 850°C at a rate of 5°C / min, and then fired at 850°C for 10 hours, thereby coating the surface of the single-particle lithium nickel oxide particles with LiNi 0.4 Co 0.2 Mn 0.4 A positive electrode active material was manufactured in which a coating layer having the following composition was formed.

[0124] The Ni distribution on the surface of the manufactured positive electrode active material was analyzed using TEM-EDS (JEOL), and the thickness up to the point where the Ni concentration changed was measured as the thickness of the coating layer. The measured thickness of the coating layer was approximately 40 nm.

[0125] Comparative Example A lithium nickel-based oxide, manufactured in Example 1 without a coating layer, was prepared as the positive electrode active material.

[0126] <Manufacturing of secondary batteries> The positive electrode active material, conductive material (Super P), and PVDF binder prepared in the examples and comparative examples were mixed in N-methylpyrrolidone in a weight ratio of 95:2:3 to produce a positive electrode slurry. The positive electrode slurry was applied to one surface of an aluminum current collector, dried at 130°C, and then rolled to produce a positive electrode.

[0127] A negative electrode slurry was prepared by mixing graphite as the negative electrode active material, Super C as the conductive material, and SBR / CMC as the binder in a weight ratio of 95.5:2:2.5. This slurry was then applied to one surface of a copper current collector, dried at 130°C, and then rolled to produce the negative electrode.

[0128] After manufacturing an electrode assembly by interposing a separator between the positive and negative electrodes, the assembly was placed inside a battery case, and then an electrolyte was injected into the case to manufacture a lithium secondary battery. The electrolyte was prepared by dissolving 1M LiPF6 in a mixed organic solvent of ethylene carbonate / dimethyl carbonate / diethyl carbonate in a volume ratio of 1:2:1, and adding 2% by weight of vinylene carbonate (VC).

[0129] Experimental Example 1 - Resistance Measurement Results For each lithium secondary battery manufactured as described above, after one charge / discharge cycle at 0.2C / 0.2C, each SOC state was set at 0.2C, and then a current of 2.5C was applied for 10 seconds. The resistance was measured by the change in voltage in response to the application of a current of 2.5C. The measurement results are shown in Figure 1.

[0130] As shown in Figure 1, the lithium secondary battery using the positive electrode active material of the embodiment in which the coating layer was formed by the method of the present invention exhibits superior resistance characteristics, particularly resistance characteristics at the discharge end, compared to the lithium secondary battery using the positive electrode active material of the comparative example.

[0131] Experimental Example 2 - Measurement Results of Lifetime Characteristics For each lithium secondary battery manufactured as described above, one charge cycle was defined as charging at 45°C in CC-CV mode at 1C until the voltage reached 4.25V, and then discharging at a constant current of 0.5C until the voltage reached 2.5V. After 50 charge-discharge cycles, the capacity retention rate was measured to evaluate the lifespan characteristics. The measurement results are shown in Figure 2.

[0132] As shown in Figure 2, the lithium secondary battery using the positive electrode active material of the example in which a coating layer was formed by the method of the present invention showed superior high-temperature life characteristics compared to the lithium secondary battery using the positive electrode active material of the comparative example.

Claims

1. A positive electrode active material comprising lithium nickel-based oxide particles in a pseudo-single particle form, which are single particles consisting of one nodule or composites of 30 or fewer nodules, and a coating layer formed on the surface of the lithium nickel-based oxide particles, The aforementioned coating layer contains lithium, nickel, cobalt, and M ａ (Here, M ａ It is formed using a nano-sized coating precursor which is a chelate complex containing Mn, Al, or a combination thereof. The molar ratio (z) of cobalt among all metals other than lithium in the aforementioned coating layer is 0 < z < 0.

4. The aforementioned coating layer has a layered structure, The coating layer is a positive electrode active material having a lower nickel content compared to the lithium nickel oxide particles.

2. The positive electrode active material according to claim 1, wherein the lithium nickel oxide particles have a nickel content of 70 mol% or more of the total metals other than lithium.

3. The positive electrode active material according to claim 1, wherein the lithium nickel oxide particles have a composition represented by the following [Chemical Formula 1]. [Chemical formula 1] Li ａ Ni ｂ Co ｃ M １ ｄ M ２ ｅ O ２ In the above chemical formula 1, M １ M is Mn, Al, or a combination thereof. ２ is one or more elements selected from the group consisting of Zr, W, Y, Ba, Ca, Ti, Mg, Ta, and Nb, and satisfies the following conditions: 0.8 ≤ a ≤ 1.2, 0.7 ≤ b < 1, 0 < c < 0.3, 0 < d < 0.3, and 0 ≤ e ≤ 0.

2.

4. The positive electrode active material according to claim 1, wherein the coating precursor is a chelate complex containing lithium, nickel, cobalt, and manganese.

5. The coating precursor has an average particle size (D ５０ The positive electrode active material according to claim 1, wherein the wavelength is 1 nm to 500 nm.

6. The positive electrode active material according to claim 1, wherein the coating layer has a composition represented by the following [Chemical Formula 2]. [Chemical formula 2] Li ｘ Ni ｙ Co ｚ M ａ ｗ M ｂ ｐ O ２－ｑ In the above chemical formula 2, M ａ M is Mn, Al, or a combination thereof. ｂ x is one or more elements selected from the group consisting of Zr, W, Y, Ba, Ca, Ti, Mg, Ta, and Nb, and the following conditions apply: 0.5 ≤ x ≤ 1.05, 0 < y ≤ 0.6, 0 < z < 0.4, 0 < w < 0.4, 0 ≤ p ≤ 0.2, and 0 ≤ q ≤ 0.

5.

7. The positive electrode active material according to claim 1, wherein the coating layer has a thickness of 1 nm to 500 nm.

8. Lithium, nickel, cobalt, and M ａ (Here, M ａ The first step involves reacting a coating precursor manufacturing solution containing a metal solution (containing Mn, Al, or a combination thereof) and a chelating agent to produce a nano-sized coating precursor, The process includes a second step of dry mixing lithium nickel-based oxide particles in a pseudo-single particle form, which are single particles consisting of one nodule or composites of 30 or fewer nodules, with the coating precursor, and then firing to form a coating layer. The aforementioned coating layer has a layered structure, The coating layer is a method for producing a positive electrode active material in which the nickel content is lower than that of the lithium nickel oxide particles.

9. The method for producing a positive electrode active material according to claim 8, wherein the chelating agent is a Lewis base compound comprising one or more selected from the group consisting of a carboxylic acid group and a nitrogen element.

10. The method for producing a positive electrode active material according to claim 9, wherein the chelating agent is one or more selected from the group consisting of citric acid, polyvinylpyrrolidone, and glycolic acid.

11. The method for producing a positive electrode active material according to claim 8, wherein the coating precursor production solution is produced by adding a metal solution containing ions contained in the coating layer and the chelating agent to a solvent and then mixing them.

12. The method for producing a positive electrode active material according to claim 11, wherein the solvent of the coating precursor production solution is one or more selected from the group consisting of ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, and 2,3-butanediol.

13. The method for producing a positive electrode active material according to claim 8, wherein the reaction in the first step is carried out at 200°C to 300°C.

14. The method for producing a positive electrode active material according to claim 8, wherein the firing in the second step is carried out at 800°C to 900°C.

15. The method for producing a positive electrode active material according to claim 14, wherein the firing is carried out by raising the temperature to 800°C to 900°C at a rate of 5°C / min to 10°C / min.

16. A positive electrode for a lithium secondary battery, comprising the positive electrode active material described in any one of claims 1 to 7.

17. A lithium secondary battery comprising a positive electrode for a lithium secondary battery as described in claim 16.

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