KR20160012772A - Surface-modified cathode active material for a lithium secondary battery, method for manufacturing the same and cathode for lithium secondary battery comprising the surface-modified cathode active material - Google Patents

Abstract

The present invention relates to a surface-modified positive electrode active material, a method for manufacturing the same, and a positive electrode for a lithium secondary battery containing the positive electrode active material. More specifically, provided are a positive electrode active material for a lithium secondary battery comprising: lithium transition metal oxide particles represented by the following chemical formula 1; and an aluminum oxide (mα-Al_2O_3) coating layer formed on the surface of the lithium transition metal oxide particles and having a negative value of surface charge, a method for manufacturing the positive electrode active material, and a positive electrode for a lithium secondary battery containing the positive electrode active material. [Chemical formula 1] Li_(1+x){Ni_aMn_bCo_(1-a-b-x)}O_2 (In the formula, -0.1<=x<=0.1, 0<=a<=1, 0<=x+a+b<=1)

Description

TECHNICAL FIELD [0001] The present invention relates to a surface-modified positive electrode active material, a method for producing the same, and a positive electrode for a lithium secondary battery including the positive electrode active material. BACKGROUND OF THE INVENTION [0001] ACTIVE MATERIAL}

The present invention relates to a surface-modified cathode active material, a method for producing the same, and a cathode for a lithium secondary battery comprising the cathode active material. More particularly, the present invention relates to a surface reformed aluminum oxide (mα-Al ₂ O ₃ ) To a cathode comprising the cathode active material, which can contribute to improvement in performance of a secondary battery, a method for producing the same, and a cathode including the cathode active material.

As technology development and demand for mobile devices increase, the demand for secondary batteries as energy sources is rapidly increasing. Among such secondary batteries, lithium secondary batteries having a high energy density and voltage, a long cycle life, and a low self-discharge rate are commercially available and widely used.

In manufacturing the lithium secondary battery, a material capable of reversibly intercalating / deintercalating lithium ions is used for the positive electrode and the negative electrode.

Lithium transition metal oxides such as LiCoO ₂ , LiMn ₂ O ₄ , LiNiO ₂ and LiMnO ₂ are widely used as cathode active materials for lithium secondary batteries. However, they have been developed to replace them in terms of cost competitiveness, capacity and cycle characteristics Research is emerging.

Recently, a variety of ternary system lithium composite oxides (Li _{1 + x} (Ni _a Mn _b Co _{1 -abx} ) O ₂ (-0.1? X? _0.1 ) in which _a part of nickel in LiNiO ₂ has been replaced with another transition metal , 0? A? 1, 0? X + a + b? 1).

However, the NiMnCo-based ternary cathode active material has an advantage of excellent capacity and cycle characteristics, but has a disadvantage of low stability at high temperature / high voltage. The cathode active material made of such a lithium transition metal oxide can be further improved in characteristics through surface modification. For example, a method of preventing deterioration by modifying the surface of the positive electrode active material by coating a metal oxide such as Al, Mg, Zr, Co, K, Na, Ca and Ti on the surface of the positive electrode active material has been proposed.

Patent Document 1 discloses a method for producing an alumina-coated lithium transition metal oxide using an aqueous process, and Patent Document 2 discloses a method for coating a metal alkoxide on the surface of a cathode active material using a dip coating method, / RTI &gt;

However, the conventional methods have a problem in that the process is complicated, the manufacturing cost is increased, and it is difficult to obtain a uniform coating effect. Therefore, effective surface modification is not achieved, and development of a method capable of effectively modifying the surface of the cathode active material is required.

Korean Patent Publication No. 10-2006-0051055 Korean Patent Publication No. 10-2002-0029218

In order to solve the above problems, the present invention provides a lithium secondary battery having improved safety under high temperature / high voltage by surface-treating a surface of a cathode active material for a lithium secondary battery with aluminum oxide (m? -Al ₂ O ₃ ) Thereby providing a cathode active material.

In addition, the present invention provides a method for producing the cathode active material using a simple weightless mixing process without additional firing process.

The present invention also provides a positive electrode for a lithium secondary battery comprising the positive electrode active material.

Specifically,

In one embodiment of the present invention

A positive electrode active material for a secondary battery,

A lithium transition metal oxide particle represented by the following formula (1)

Providing a secondary battery, the positive electrode active material particle containing, (hereinafter "mα-Al ₂ O _3" referred to as a modified α-Al ₂ O ₃₎ coating the lithium transition oxide has a surface charge negative aluminum formed on the metal oxide particle surface do.

[Chemical Formula 1]

Li _{1 + x} (Ni _a Mn _b Co _{1 -abx} ) O ₂

In this formula, -0.1? X? 0.1, 0? A? 1, 0? X + a + b?

In one embodiment of the present invention, the lithium transition metal oxide particles represented by Formula 1 and the aluminum oxide (m? -Al ₂ O ₃ ) particles having a negative surface charge value are mixed using a zero- A method for producing an active material is provided.

According to another embodiment of the present invention, there is provided a positive electrode for a lithium secondary battery, which further comprises at least one of the positive electrode active material and a conductive material, a binder and a filler.

As described above, according to the present invention, there is provided a lithium secondary battery having improved high-temperature high-voltage stability and cycle characteristics by uniformly forming an aluminum oxide coating layer having negative surface charge values on the surface of the cathode active material particles under the conditions of no- .

1 is a comparative SEM photograph of aluminum oxide (α-Al ₂ O ₃ ) particles having positive surface charge values and aluminum oxide (mα-Al ₂ O ₃ ) particles having negative surface charge values.
2 is a graph showing the surface charge value according to the pH of the aluminum oxide (m? -Al ₂ O ₃ ) coating layer of the present invention.
3 is a graph comparing the results of charging and discharging the secondary battery of Example 1 of the present invention and the secondary battery of Comparative Example 1 at room temperature.
4 is a graph comparing the results of the high-temperature high-voltage charging / discharging lifetime characteristics of the secondary battery of Example 1 of the present invention and the secondary battery of Comparative Example 1. Fig.

Hereinafter, the present invention will be described in detail. Herein, terms and words used in the present specification and claims should not be construed to be limited to ordinary or dictionary meanings, and the inventor may appropriately define the concept of the term to describe its own invention in the best way. It should be construed as meaning and concept consistent with the technical idea of the present invention.

In order to produce a cathode active material for a lithium secondary battery, conventionally, a predetermined amount of a cathode active material particle and an aluminum oxide (α-Al ₂ O ₃ ) particle to be coated are mixed together using a ball mill and a fretner mill ), It is common to carry out an additional baking process at a temperature of approximately 200 to 800 ° C. In this case, there is a problem that the surface of the cathode active material is damaged by a general mixing process accompanied by high-speed rotation, and this damage is further increased during the subsequent high-temperature firing process, which ultimately leads to deterioration of lithium secondary battery capacity, And the risk of safety accidents. Particularly, since aluminum oxide (-Al ₂ O ₃ ) having mostly positive surface charge values is used for the surface modification of the cathode active material in the past, it is difficult to form a film having a uniform thickness on the surface of the cathode active material Since there are other problems, there is a need to solve these problems.

In order to solve the above problems,

A positive electrode active material for a secondary battery,

A lithium transition metal oxide particle represented by the following formula (1)

And an aluminum oxide (m? -Al ₂ O ₃ ) coating layer having a negative surface charge value formed on the surface of the lithium-transition metal oxide particle.

[Chemical Formula 1]

Li _{1 + x} (Ni _a Mn _b Co _{1 -abx} ) O ₂

In this formula, -0.1? X? 0.1, 0? A? 1, 0? X + a + b?

In the present invention, the lithium transition metal oxide may be spinel Li [Ni ₀ . ₅ Mn ₁ . _{5-x Co x] O 4} (0≤x≤0.1), specifically, _{Li (Ni 1/3 Mn 1} /3 Co 1/3 O 2) may be, in addition to the industry conventional in the art for use with conventional positive electrode active material The lithium-containing transition metal complex oxide can be used.

In the present invention, pH of the surface having a negative charge values aluminum (mα-Al ₂ O ₃₎ oxide coating layer is 3 to 11, the surface charge value may be a -40㎷ to -1㎷, specifically At pH 7, the surface charge value can be -20 [mu] m (see Fig. 2).

In the present invention, aluminum (mα-Al ₂ O ₃₎ oxide coating layer having a surface electric charge of the negative value may have a structure of a single-layer or multi-layer form. In this case, the total thickness of the aluminum oxide (mα-Al ₂ O ₃₎ coating layer can be suitably adjusted within a range for increasing the like life characteristics and high-temperature storage characteristics of the battery, and particularly limited, but, too thick if capacity and an output It is preferably 30 nm or less, and more preferably 20 nm or less.

In the present invention, the content of aluminum in the aluminum oxide coating layer having the negative surface charge value may be 5 ppm to 100 ppm based on the total weight of the cathode active material. If the content of aluminum oxide is less than 5 ppm, it may be difficult to form a sufficient coating layer on the surface of the cathode active material because the amount of aluminum oxide used for the surface coating is small. On the other hand, when the aluminum oxide content exceeds 100 ppm, a thick coating layer is formed, which obstructs the mobility of lithium ions and may affect the resistance increase and the output characteristics.

On the other hand, in the case of the coating layer formed on the surface of the cathode active material, the coating pattern may vary depending on the state of the surface charge. That is, in the case of aluminum oxide (-Al ₂ O ₃ ) having the positive (+) surface charge shown in FIG. 1A, the aluminum oxide is coherent with each other and is not uniformly coated on the surface of the cathode active material, There is a problem that occurs. Further, additional firing is inevitable in order to bring aluminum oxide having a positive surface charge value into contact with the surface of the cathode active material. On the contrary, in the case of aluminum oxide (m? -Al ₂ O ₃ ) having a negative (-) surface charge value shown in FIG. 1B, not only is it soft type, but also has excellent spreadability and relatively strong shear force, And has a physical property to adhere well to the surface of the positive electrode active material particles without further firing. Therefore, in the present invention, when the surface of the positive electrode active material is coated with aluminum oxide (-Al ₂ O ₃ ) particles having positive (+) surface charge by surface modification using aluminum oxide having a negative surface charge value , It is possible to form a uniformly distributed aluminum oxide coating layer which does not separate from the surface of the cathode active material particles even if no additional firing process is performed after coating. Therefore, the capacity of the lithium secondary battery can be increased and the cycle life characteristics at a high temperature and a high voltage can be ensured.

In one embodiment of the present invention, a lithium-transition metal oxide particle represented by Formula 1 and aluminum oxide (m? -Al ₂ O ₃ ) having a negative surface charge value are formed through a series of processes using a gravity- And a step of mixing the particles.

That is, in the method of the present invention, the aluminum particles and the lithium-transition metal active material particles are mixed using a gravity-free dry mixing method using a shear force instead of a conventional mixing method. Thus, a ball mill and a frenner mill Problems such as surface damage of the cathode active material that can be generated from the mixing process, and the like can be solved.

Specifically, in the zero-gravity mixing step, the cathode active material particles and aluminum oxide (m? -Al ₂ O ₃ ) particles having negative surface charge values are charged into a zero-gravity mixing apparatus. In this case, the zero-gravity mixing device may include a main aggregate in the form of a rotating spiral and three sub-aggregates. Also, the zero gravity mixing step may be performed such that the three subassemblies joined to the main aggregate are rotated, and the materials are injected from the nozzles through the shear force of the aggregates so as to be mixed in almost zero gravity. Specifically, in the zero gravity mixing step, the tip peripheral speed of the blade is 2 m / s or more, preferably 5 m / s to 30 m / s, the rotation speed is 100 to 2000 rpm, the discharge pressure is 0.1 MPa or more, Preferably 0.1 MPa to 1.47 MPa, under a shear force condition. Further, in the present invention, after the surface of the lithium-transition metal oxide particle surface is treated with aluminum oxide particles, an additional calcination step can be eliminated.

Also, in one embodiment of the present invention, there is provided a cathode for a secondary battery comprising the surface-modified cathode active material. The anode may optionally include a conductive material, a binder, a filler, and the like.

At this time, the conductive material is usually added in an amount of 1 to 30% by weight based on the total weight of the mixture containing the cathode active material.

Such a conductive material is not particularly limited as long as it has electrical conductivity without causing a chemical change in the battery, and includes, for example, graphite; Carbon black such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, and summer black; Conductive fibers such as carbon fiber and metal fiber; Metal powders such as carbon fluoride, aluminum, and nickel powder; Conductive whiskey such as zinc oxide and potassium titanate; Conductive metal oxides such as titanium oxide; Conductive materials such as polyphenylene derivatives and the like can be used. Concrete examples of commercially available conductive materials include acetylene black series such as Chevron Chemical Company, Denka Singapore Private Limited, Gulf Oil Company, etc.), Ketjenblack, EC (Armak Company), Vulcan XC-72 (Cabot Company), and Super P (Timcal).

The binder is a component which assists in bonding of the active material and the conductive material and bonding to the current collector, and is usually added in an amount of 1 to 30% by weight based on the total weight of the mixture containing the cathode active material. Examples of such binders include polyvinylidene fluoride, polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene , Polypropylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene butylene rubber, fluorine rubber, and various copolymers.

The filler is optionally used as a component for suppressing the expansion of the electrode, and is not particularly limited as long as it is a fibrous material without causing any chemical change in the battery. Examples of the filler include olefin-based polymerizers such as polyethylene and polypropylene; Fibrous materials such as glass fibers and carbon fibers are used.

The present invention provides a positive electrode for a secondary battery, which is produced by coating a slurry prepared by mixing the positive electrode material mixture with a solvent such as NMP, and then drying and rolling the slurry.

The cathode current collector is generally made to have a thickness of 3 to 500 mu m. Such a positive electrode collector is not particularly limited as long as it has conductivity without causing chemical change to the battery, and may be formed on the surface of stainless steel, aluminum, nickel, titanium, sintered carbon or aluminum or stainless steel Carbon, nickel, titanium, silver, or the like may be used. The current collector may have fine irregularities on the surface thereof to increase the adhesive force of the cathode active material, and various forms such as a film, a sheet, a foil, a net, a porous body, a foam, and a nonwoven fabric are possible.

The present invention also provides a secondary battery comprising the positive electrode. Preferably, the secondary battery is a lithium secondary battery. The lithium secondary battery is composed of the positive electrode and the negative electrode, a separator, and a lithium-containing non-aqueous electrolyte.

The negative electrode is prepared, for example, by applying a negative electrode mixture containing a negative electrode active material on a negative electrode collector and then drying the same. The negative electrode mixture may contain a conductive material, a binder, a filler or the like &Lt; / RTI &gt;

Examples of the negative electrode active material include carbon and graphite materials such as natural graphite, artificial graphite, expanded graphite, carbon fiber, non-graphitizable carbon, carbon black, carbon nanotube, fullerene and activated carbon; Metals such as Al, Si, Sn, Ag, Bi, Mg, Zn, In, Ge, Pb, Pd, Pt and Ti which can be alloyed with lithium and compounds containing these elements; Complexes of metals and their compounds and carbon and graphite materials; Lithium-containing nitrides, and the like. Among them, a carbon-based active material, a silicon-based active material, a tin-based active material, or a silicon-carbon based active material is more preferable, and these may be used singly or in combination of two or more.

The negative electrode current collector is generally made to have a thickness of 3 to 500 mu m. The negative electrode current collector is not particularly limited as long as it has high conductivity without causing chemical change in the battery. Examples of the negative electrode current collector include copper, stainless steel, aluminum, nickel, titanium, sintered carbon, copper or stainless steel Surface-treated with carbon, nickel, titanium, silver or the like, aluminum-cadmium alloy, or the like can be used. In addition, like the positive electrode collector, fine unevenness can be formed on the surface to enhance the bonding force of the negative electrode active material, and it can be used in various forms such as films, sheets, foils, nets, porous bodies, foams and nonwoven fabrics.

The separation membrane is interposed between the anode and the cathode, and an insulating thin film having high ion permeability and mechanical strength is used. The pore diameter of the separator is generally 0.01 to 10 mu m, and the thickness is generally 5 to 300 mu m. Such separation membranes include, for example, olefinic polymers such as polypropylene, which are chemically resistant and hydrophobic; A sheet or nonwoven fabric made of glass fiber, polyethylene or the like is used. When a solid electrolyte such as a polymer is used as an electrolyte, the solid electrolyte may also serve as a separation membrane.

The lithium salt-containing nonaqueous electrolyte solution is composed of an electrolyte solution and a lithium salt. As the electrolyte solution, a nonaqueous organic solvent, an organic solid electrolyte, and an inorganic solid electrolyte may be used.

Examples of the non-aqueous organic solvent include N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, gamma -Butyrolactone, 1,2-dimethoxyethane, tetrahydroxyfuran, 2-methyltetrahydrofuran, dimethylsulfoxide, 1,3-dioxolane, formamide, dimethylformamide, dioxolane , Acetonitrile, nitromethane, methyl formate, methyl acetate, triester phosphate, trimethoxymethane, dioxolane derivatives, sulfolane, methylsulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate Nonionic organic solvents such as tetrahydrofuran derivatives, ethers, methyl pyrophosphate, ethyl propionate and the like can be used.

Examples of the organic solid electrolyte include a polymer electrolyte such as a polyethylene derivative, a polyethylene oxide derivative, a polypropylene oxide derivative, a phosphate ester polymer, an agitation lysine, a polyester sulfide, a polyvinyl alcohol, a polyvinylidene fluoride, A polymer containing an ionic dissociation group and the like may be used.

Examples of the inorganic solid electrolyte include Li ₃ N, LiI, Li ₅ NI ₂ , Li ₃ N-LiI-LiOH, LiSiO ₄ , LiSiO ₄ -LiI-LiOH, Li ₂ SiS ₃ , Li ₄ SiO ₄ , Li ₄ Nitrides, halides, sulfates and the like of Li such as SiO ₄ -LiI-LiOH and Li ₃ PO ₄ -Li ₂ S-SiS ₂ can be used.

The lithium salt is a material that is readily soluble in the non-aqueous electrolyte, for example, LiCl, LiBr, LiI, LiClO 4, LiBF 4, LiB 10 Cl 10, LiPF 6, LiCF 3 SO 3, LiCF 3 CO 2, LiAsF _{6, LiSbF 6, LiAlCl 4,} CH 3 SO 3 Li, CF 3 SO 3 Li, (CF 3 SO 2) 2 NLi, chloroborane lithium, lower aliphatic carboxylic acid lithium, lithium tetraphenyl borate and imide have.

For the purpose of improving the charge / discharge characteristics and the flame retardancy, the electrolytic solution may be mixed with an organic solvent such as pyridine, triethylphosphite, triethanolamine, cyclic ether, ethylenediamine, glyme, hexaphosphoric triamide, Benzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinones, N, N-substituted imidazolidines, ethylene glycol dialkyl ethers, ammonium salts, pyrrole, 2-methoxyethanol, . In some cases, halogen-containing solvents such as carbon tetrachloride and ethylene trifluoride may be further added to impart nonflammability. In order to improve the high-temperature storage characteristics, carbon dioxide gas may be further added. FEC (Fluoro-Ethylene Carbonate, PRS (Propene sultone), and the like.

Such a secondary battery includes a plurality of battery cells used as a power source for a middle- or large-sized device requiring high temperature stability, long cycle characteristics, and high rate characteristics, And may be suitably used as a unit cell in a middle- or large-sized battery module.

Preferred examples of the above medium to large devices include a power tool that is powered by an electric motor and moves; An electric vehicle including an electric vehicle (EV), a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (PHEV), and the like; An electric motorcycle including an electric bike (E-bike) and an electric scooter (E-scooter); An electric golf cart; Power storage devices, and the like, but the present invention is not limited thereto.

In the foregoing detailed description of the present invention, specific examples have been described. However, various modifications are possible within the scope of the present invention. The technical spirit of the present invention should not be limited to the embodiments of the present invention but should be determined by the claims and equivalents thereof.

Example

Example  One

_{Li (Ni 1/3 Mn 1} /3 Co 1/3 O 2) were weighed to zero gravity the positive electrode active material 100 1 wt% by weight of the negative surface charge value with aluminum (mα-Al ₂ O ₃₎ oxidation of -2mV per unit Weightless mixing process was carried out for 20 minutes using a mixing device (Model NOB-130, wing tip main speed: 5 m / s, discharge pressure: 0.1 MPa, rotation speed: 1200 rpm) To prepare a cathode active material particle (A) surface-treated with aluminum (m? -Al ₂ O ₃ ).

Subsequently, a positive electrode slurry was prepared in such a manner that the ratio of the positive electrode active material: conductive material: binder was 96: 2: 2 based on the weight, and the slurry was applied to an Al foil, rolled and dried to prepare a positive electrode for a secondary battery . The anode was coin type to form a coin type cell. Li-metal was used as an anode active material, and an electrolytic solution in which 1 M of LiPF ₆ was dissolved in a carbonate electrolyte was used.

Comparative Example  One

_{Li (Ni 1/3 Mn 1} /3 Co 1/3 O 2) a cathode active material per 100 parts by weight positive surface charge values for having aluminum oxide (α-Al ₂ O ₃₎ were weighed a 1 wt% 1200rpm , Followed by baking at 600 ° C. to prepare cathode active material particles (B) surface-treated with aluminum oxide (α-Al ₂ O ₃ ) having a positive surface charge value.

Subsequently, a positive electrode slurry was prepared in such a manner that the ratio of the positive electrode active material: conductive material: binder was 96: 2: 2 based on the weight, and the slurry was applied to an Al foil, rolled and dried to prepare a positive electrode for a secondary battery . The anode was coin type to form a coin type cell. Li-metal was used as an anode active material, and an electrolytic solution in which 1 M of LiPF ₆ was dissolved in a carbonate electrolyte was used.

Experimental Example  One.

The secondary batteries prepared in Example 1 and Comparative Example 1 were subjected to a normal temperature charge-discharge test and a high-temperature high-voltage life test, and the results are shown in FIG. 3 and FIG. Specifically, charge and discharge were carried out from 3V to 4.25V at room temperature, and charge / discharge was performed from 3V to 4.25V. The capacity was checked and the charge / discharge test was carried out at room temperature. 100 cycles were carried out at 45C for 1C / 2C 4.35V for high- Respectively.

3 and 4, in the case of a secondary battery using a cathode active material surface-treated with aluminum oxide (m? -Al ₂ O ₃ ) having a negative surface charge value of Example 1 on the basis of 100 cycles, Compared with secondary batteries using a cathode active material surface-treated with aluminum oxide (α-Al ₂ O ₃ ) having an amount of surface charge that has undergone additional firing after coating, the process was simplified and no further firing was performed There was no significant difference in capacity and cycle characteristics. On the contrary, since no further firing was performed, it was confirmed that the surface damage of the cathode active material was improved and the cycle characteristics were further improved.

Claims (12)

A positive electrode active material for a secondary battery,
A lithium transition metal oxide particle represented by the following formula (1)
The lithium transition oxide has a surface charge negative aluminum formed on the metal oxide particle surface (mα-Al ₂ O ₃₎ secondary battery, the positive electrode active material comprises a coating layer.
[Chemical Formula 1]
Li _{1 + x} (Ni _a Mn _b Co _{1 -abx} ) O ₂
In the above formula, -0.1? X? 0.1, 0? A? 1, 0? X + a + b? The method according to claim 1,
The lithium transition metal oxide may be spinel Li [Ni ₀ . ₅ Mn ₁ . _{5 x} Co _x ] O ₄ (0? _X ? 0.1). The method according to claim 1,
Wherein the pH of the aluminum oxide (m? -Al ₂ O ₃ ) coating layer having the negative surface charge value is from 3 to 11, and the surface charge value of the coating layer is from -40 ㎷ to -1 질. . The method of claim 3,
The aluminum oxide (mα-Al ₂ O ₃₎ and the pH of the coating layer 7, the surface charge value is a cathode active material for a lithium secondary battery characterized in that -20㎷. The method according to claim 1,
The aluminum oxide (mα-Al ₂ O ₃₎ coating the cathode active material for a lithium secondary battery characterized by having a structure of a single-layer or multi-layer form. The method according to claim 1,
Wherein the total thickness of the aluminum oxide (m? -Al ₂ O ₃ ) coating layer is 30 nm or less. The method according to claim 1,
Wherein the content of aluminum in the aluminum oxide coating layer is 5 ppm to 100 ppm based on the total weight of the cathode active material. A method for producing a cathode active material according to claim 1, comprising the step of weightless mixing lithium transition metal oxide particles represented by the following formula (1) and aluminum oxide (m? -Al ₂ O ₃ ) particles having a negative surface charge value Manufacturing method;
[Chemical Formula 1]
Li _{1 + x} (Ni _a Mn _b Co _{1 -abx} ) O ₂
In the above formula, -0.1? X? 0.1, 0? A? 1, 0? X + a + b? The method of claim 8,
Wherein the non-gravity mixing step is carried out under a condition that a tip peripheral speed of the blade is 2 m / s or more, a rotation speed is 100 rpm to 2000 rpm, and a discharge pressure is 0.1 MPa or more. The method of claim 9,
Wherein the zero gravity mixing step is carried out under conditions that the tip peripheral speed of the blade is 5 m / s to 30 m / s, the rotation speed is 100 rpm to 2000 rpm, and the discharge pressure is 0.1 MPa to 1.47 MPa. Gt; The positive electrode active material according to claim 1,
Optionally further comprising at least one of a conductive material, a binder and a filler. A lithium secondary battery comprising a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and a non-aqueous electrolyte according to claim 11.

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