KR20160112766A - Cathode active material for lithium secondary battery with high voltage and Lithium secondary battery comprising the same - Google Patents

Abstract

The present invention relates to a positive electrode active material for a high voltage and, more specifically, to a positive electrode active material, which exhibits excellent high-temperature properties used in a lithium secondary battery having 5 V. The positive electrode active material for a lithium secondary battery is represented by chemical formula 1, Li_(1+a)Ni_bM1_cMn_[2-(b+c)]O_(4-z-d)A_n. A surface layer is represented by chemical formula 2, Li_(1+a)Ni_bM1_cM2_dMn_[2-(b+c+d)]O_(4-z-d)A_n.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cathode active material for a high-voltage lithium secondary battery, and a lithium secondary battery including the cathode active material,

The present invention relates to a cathode active material for a high voltage lithium secondary battery and a lithium secondary battery comprising the same, and more particularly, to a cathode active material for a 5V class lithium secondary battery and a lithium secondary battery comprising the same.

Recently, with regard to the tendency to miniaturize and lighten portable electronic devices, there is an increasing need for high performance and large capacity of batteries used as power sources for these devices.

The lithium secondary battery is manufactured by using a material capable of reversible intercalation / deintercalation of lithium ions as an active material of the positive electrode and the negative electrode, and filling an organic electrolytic solution or a polymer electrolyte between the positive electrode and the negative electrode.

As a cathode active material of a lithium secondary battery, a lithium composite metal compound is used. For example, composite metal oxides such as LiMn ₂ O ₄ , LiMnO ₂ , LiCoO ₂ and LiNiO ₂ have been studied.

Of the above cathode active materials, Mn-based cathode active materials such as LiMn ₂ O ₄ and LiMnO ₂ are easy to synthesize and are relatively inexpensive and have excellent thermal stability compared to other active materials in overcharging, However, it has a disadvantage of low capacity.

LiCoO ₂ has a good electric conductivity, a high battery voltage of about 3.7 V, excellent cycle life characteristics, stability and discharge capacity, and is a typical cathode active material commercially available at present. However, since LiCoO ₂ is an expensive raw material that accounts for more than 30% of the battery price, there is a problem that price competitiveness is poor.

LiNiO ₂ exhibits the battery characteristics of the highest discharge capacity among the above-mentioned cathode active materials, but it has a disadvantage that it is difficult to synthesize. In addition, the high oxidation state of nickel causes a decrease in battery life and electrode life, and there is a problem that self discharge is severe and reversibility is low. In addition, it is difficult to commercialize it because the stability is not completely secured.

The inventors of the present application have found that the lithium composite metal oxide containing both manganese and nickel has a high operating potential of 4.6 V or more and therefore the performance of the battery is deteriorated due to decomposition of the electrolyte and side reactions with the electrolyte, . Further, it was confirmed that elution of Mn ions occurred. This problem was a problem not found in LiMn ₂ O ₄ having an operating voltage of 4V.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a cathode active material for a 5V class high voltage and a method of manufacturing the same.

The present invention also provides a cathode active material for a high-voltage lithium secondary battery that maximizes high-temperature performance, more specifically, a cathode active material used in a 5V-class lithium secondary battery to improve the high-temperature characteristics of the battery and a lithium secondary battery comprising the same.

In one aspect of the present invention, there is provided a cathode active material for a lithium secondary battery represented by the following Chemical Formula 1, wherein the surface layer is represented by Chemical Formula 2:

[Chemical Formula 1]

Li _{1 + a} Ni _b M1 _c Mn _{2 - (b + c)} O _{4 -zda n}

In this formula,

M1 is at least one element selected from the group consisting of Ni, Ti, Co, Al, Cu, Fe, Mg, B, Cr, Zr, Zn and two period transition metals;

A is an anion having a valence of -1 or -2, and is independently at least one selected from the group consisting of halogens such as F, Cl, Br and I, S and N;

0.1? 0.3? B? 0.7, 0? C? 0.1, 0.001? D? 0.02, 0? Z? 0.1, 0? N? 0.1.

(2)

Li _{1 + a} Ni _b M1 _c M2 _d Mn _{2 - (b + c + d)} O _{4 -zda n}

In this formula,

M1 is at least one element selected from the group consisting of Ni, Ti, Co, Al, Cu, Fe, Mg, B, Cr, Zr, Zn and two period transition metals;

M2 is one or more selected from the group consisting of V, Cr, Nb, Mo, Ta and W;

A is an anion having a valence of -1 or -2, and is independently at least one selected from the group consisting of halogens such as F, Cl, Br and I, S and N;

0.1? 0.3? B? 0.7, 0? C? 0.1, 0.001? D? 0.02, 0? Z? 0.1, 0? N? 0.1.

The weight ratio of the transition metal (M2 / positive electrode active material) to the total weight of the positive electrode active material may be 0.05% by weight to 5.0% by weight.

The cathode active material may be primary particles or secondary particles formed by aggregation of primary particles.

The cathode active material may be in the form of a primary particle having an average particle diameter (D50) of 5 to 30 mu m.

The cathode active material may be in the form of a secondary particle having an average particle diameter (D50) of 5 to 30 mu m.

The surface layer may have a thickness greater than 5 nm and less than 100 nm.

In another aspect of the present invention, in a lithium secondary battery including a cathode, a cathode, and an electrolyte, the cathode may include the cathode active material described above.

The lithium secondary battery may be used for a voltage of 5V.

In another embodiment of the present invention, there is provided a process for the preparation of a catalyst, comprising mixing nickel source, manganese source, and transition metal M 1 source in a constant composition and heat treating to obtain the particles of Formula 1, mixing the particles of Formula 1 with a source of transition metal M2, And annealing the heat treated material, wherein each of the heat treatment processes is independently performed at a temperature of 800 to 950 占 폚, and the annealing process is performed at 700 to 1000 占 폚. A manufacturing method is provided.

The cathode active material according to the present invention can be used as a cathode active material for a high voltage lithium secondary battery, more specifically, a cathode active material for a 5V class lithium secondary battery.

The high-voltage lithium secondary battery produced with such a cathode active material exhibits excellent output characteristics, improved high-temperature lifetime characteristics, and excellent high-temperature storage recovery.

Hereinafter, embodiments of the present invention will be described in detail. However, it should be understood that the present invention is not limited thereto, and the present invention is only defined by the scope of the following claims.

In one aspect of the present invention, there is provided a cathode active material for a lithium secondary battery represented by the following Chemical Formula 1, wherein the surface layer is represented by Chemical Formula 2:

[Chemical Formula 1]

Li _{1 + a} Ni _b M1 _c Mn _{2 - (b + c)} O _{4 -zda n}

In this formula,

M1 is at least one element selected from the group consisting of Ni, Ti, Co, Al, Cu, Fe, Mg, B, Cr, Zr, Zn and two period transition metals;

A is an anion having a valence of -1 or -2, and is independently at least one selected from the group consisting of halogens such as F, Cl, Br and I, S and N;

0.1? 0.3? B? 0.7, 0? C? 0.1, 0.001? D? 0.02, 0? Z? 0.1, 0? N? 0.1.

(2)

Li _{1 + a} Ni _b M1 _c M2 _d Mn _{2 - (b + c + d)} O _{4 -zda n}

In this formula,

M1 is at least one selected from the group consisting of Ni, Ti, Co, Al, Cu, Fe, Mg, B, Cr, Zr, Zn and two period transition metals;

M2 is one or more selected from the group consisting of V, Cr, Nb, Mo, Ta and W;

A is an anion having a valence of -1 or -2, and is independently at least one selected from the group consisting of halogens such as F, Cl, Br and I, S and N;

0.1? 0.3? B? 0.7, 0? C? 0.1, 0.001? D? 0.02, 0? Z? 0.1, 0? N? 0.1.

The positive electrode active material is different from LiMn ₂ O ₄ in the 4V region (about 3.7V to 4.3V) in that it has an operating potential of 4.6 V or more and 4.9 V or less. Since the cathode active material has an operating potential of 4.6 V or more and 4.9 V or less, LiMn ₂ O ₄ The high energy density characteristic can be exerted.

In the cathode active material M1, M1 is uniformly distributed throughout the cathode active material particle including the surface layer, while the composition represented by the general formula (2) can act as a protective layer for suppressing the reaction with the electrolyte constituting the surface layer of the cathode active material particle. The protective layer may prevent direct contact between the electrolyte solution and the compound of Formula 1 during high-voltage charging and discharging, thereby suppressing side reactions of the electrolyte solution. As a result, the positive electrode active material according to the present invention can exhibit stable charge / discharge cycle characteristics, thereby increasing the charge / discharge reversible capacity.

Herein, the term "surface layer" means a region in which at least 50% by weight of the total transition metal M2 present in the active material is present, and a thickness region in the center direction with respect to the outermost portion of the active material.

The weight ratio of the transition metal (M2 / positive electrode active material) to the total weight of the positive electrode active material may be 0.05% by weight to 5.0% by weight. If the weight ratio is less than 0.05 wt%, the effect of improving the high-temperature characteristics of M2 can not be sufficiently expected. If the weight ratio is more than 5.0 wt%, the charge / discharge capacity is rapidly lowered.

In the cathode active material, the surface layer may have a thickness of greater than 5 nm and less than 100 nm, and the above-described advantages can be expected only if the thickness is within the above range. When the thickness of the surface layer is as thin as 5 nm or less, it is difficult to expect the effect of the transition metal M2. When the thickness of the surface layer is larger than 100 nm, there is no effect of improving the performance proportional to the thickness increase. . The thickness of the surface layer can be confirmed by X-ray photoelectron spectroscopy (XPS).

The structure of the cathode active material can be confirmed by using a weakly acidic dissolving solution. For more detailed analysis method, refer to KR 2012-0122975A.

The cathode active material may be in the form of primary particles or secondary particles formed by aggregation of primary particles. The secondary particles formed by coagulation of primary particles or primary particles may have a spherical shape. In the present specification, the term 'spherical' is understood not only as a complete spherical shape but also as a concept including a spherical-like shape or a rectangular elliptical shape.

When the cathode active material comprises only primary particles, the average particle diameter (D50) of the cathode active material may range from 3 to 30 mu m.

When the cathode active material is in the form of secondary particles formed by agglomeration of primary particles, the primary particles may have an average particle size (D50) of greater than 0 and less than 3 탆, and the secondary particles may have an average of 5 to 30 탆 (D50) or an average particle diameter (D50) of 8 to 25 mu m.

When the cathode active material particles have an average particle diameter (D50) larger than 30 占 퐉, the charge / discharge capacity is drastically lowered and the electrode processability is drastically lowered. When the cathode active material particle is smaller than 3 占 퐉, the transition metal elution is rapidly increased, .

The method of preparing the cathode active material is not particularly limited as long as it is in accordance with the object of the present invention, but it is preferable to mix the nickel source, the manganese source and the transition metal M 1 source in a predetermined composition and heat- Mixing the transition metal M2 source with a grain of Formula 1, heat treating, and annealing the annealed material, wherein each of the annealing processes is performed independently at a temperature of 800 to 950 < 0 > C, The process may be prepared by a solid phase process carried out at 700-1000 占 폚, see below.

[Preparation of particles represented by Chemical Formula 1]

A nickel source, a manganese source, a lithium source, and a source of transition metal M1 are mixed.

In this case, the nickel source, the manganese source, and the lithium source may be compounds commonly used in the art. For example, NiO or Ni (OH) ₂ may be used as the nickel source, Mn ₃ O ₄ And examples of the lithium source include Li ₂ CO ₃ and LiOH, but the present invention is not limited thereto. As the source of the transition metal M1, M1 group, oxides, hydroxides, carbonates, sulfates, halides, nitrates and the like can be used.

The nickel, manganese, lithium source and transition metal source are mixed and heat-treated to obtain particles represented by the formula (1). The heat treatment at this time is understood as a simple heat treatment distinguished from the annealing described later.

The atmosphere of the heat treatment is not particularly limited and may be arbitrarily selected from an oxidizing atmosphere, a reducing atmosphere, a vacuum, and an inert atmosphere. For convenience of the process, heat treatment can be performed in the atmosphere. Heat treatment may be performed at a temperature in the range of about 500 ° C to about 1200 ° C, or in the range of about 800 ° C to 950 ° C.

[Addition of transition metal M2 source]

The particles of the formula 1 obtained above and the transition metal M2 source are mixed and heat-treated under stirring.

The transition metal M2 source may be an oxide of one or more metals selected from the group consisting of V, Cr, Nb, Mo, Ta and W.

The heat treatment temperature can be determined in consideration of the extent to which the transition metal M2 is dissolved in the particles of the formula (1). For example, a heat treatment may be performed at a temperature in the range of about 500 ° C to about 1200 ° C, or in the range of about 800 to 950 ° C.

 [Annealing]

Then, an annealing process is performed. If the annealing process is not performed, the transition metal M2 is not distributed to the surface layer of the cathode active material. The annealing temperature may be determined in consideration of the kind of the transition metal M2 to be substituted and the heat treatment temperature. For example, when the heat treatment is performed at a temperature of 800 to 950 占 폚, the annealing may be performed at a temperature in the range of 700 to 1000 占 폚.

The cathode active material according to an embodiment of the present invention may be mixed with other lithium-containing transition metal oxides in addition to the above-mentioned cathode active material.

Examples of the other lithium-containing transition metal oxide include a layered compound such as lithium cobalt oxide (LiCoO ₂ ) and lithium nickel oxide (LiNiO ₂ ), a compound represented by the formula Li _{1 + y} Mn _{2 - y} O ₄ (where y is 0 to 0.33 , Lithium manganese oxides such as LiMnO ₃ , LiMn ₂ O ₃ and LiMnO ₂ , lithium copper oxide (Li ₂ CuO ₂ ); A vanadium oxide such as LiV ₃ O ₈ , LiFe ₃ O ₄ , V ₂ O ₅ and Cu ₂ V ₂ O ₇ , a vanadium oxide represented by the formula LiNi _{1 -y} M _y O ₂ (where M = Co, Mn, Al, Mg, B or Ga and y = 0.01 to 0.3), LiMn _{2 - y} M _y O ₂ (M = Co, Ni, Fe, Cr, Zn, or Ta , y = 0.01 to 0.1) or Li ₂ Mn ₃ MO ₈ (where M is Fe, Co, Ni, Cu or Zn), Li manganese complex oxide represented by the formula: Li moiety is substituted with an alkaline earth metal ion LiMn ₂ O ₄ , a disulfide compound Fe ₂ (MoO ₄ ) ₃ , and the like, but the present invention is not limited thereto.

The anode may be prepared by applying a slurry prepared by mixing a cathode mixture containing the cathode active material with a solvent such as N-methylpyrrolidone (NMP), applying the slurry on the cathode collector, followed by drying and rolling.

In addition to the cathode active material, the cathode mixture may optionally include a conductive material, a binder, a filler, and the like.

The cathode current collector generally has a thickness of 3 to 500 mu m. Such a positive electrode current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery, and examples thereof include copper, stainless steel Surface-treated with carbon, nickel, titanium, silver or the like, aluminum-cadmium alloy, or the like can be used. The positive electrode current collector may be formed into various shapes such as a film, a sheet, a foil, a net, a porous body, a foam, a nonwoven fabric, or the like by forming fine irregularities on the surface to enhance the bonding force of the positive electrode active material.

The conductive material is usually added in an amount of 1 to 30% by weight based on the total weight of the mixture including the cathode active material. Such a conductive material is not particularly limited as long as it has electrical conductivity without causing chemical change in the battery. For example, graphite carbon black such as natural graphite or artificial graphite, acetylene black, ketjen black, channel black, , Lamp black, summer black, etc. Carbon fiber fluorinated carbon such as carbon fiber or metal fiber, metal powder such as aluminum and nickel powder Conductive metal oxide such as zinc oxide and conductive whiskey titanium oxide such as potassium titanate Polyphenylene derivative And the like can be used.

The binder is added to the binder in an amount of 1 to 30% by weight, based on the total weight of the mixture containing the cathode active material, as a component that assists in bonding between the active material and the conductive agent and bonding to the current collector. 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, various copolymers and the like.

The filler is not particularly limited as long as it is a fibrous material without causing any chemical change in the battery and is optionally used as a component for suppressing the expansion of the anode. For example, an olefin-based polymer glass such as polyethylene or polypropylene Fibrous materials such as fibers and carbon fibers are used.

Typical examples of the dispersion include isopropyl alcohol, N-methyl pyrrolidone (NMP), and acetone.

The method of applying the paste of the electrode material to the metal material in a uniform manner can be selected from known methods in consideration of the characteristics of the material and the like or can be carried out by a new suitable method. For example, the paste can be uniformly dispersed by using a doctor blade or the like after being distributed on the current collector. In some cases, a method of performing the distribution and dispersion processes in a single process may be used. In addition, a die casting method, a comma coating method, a screen printing method, or the like may be used. Alternatively, the resin may be formed on a separate substrate, and then pressed or laminated by a pressing or laminating method. .

It is preferable that the paste applied on the metal plate is dried in a vacuum oven at 50 to 200 DEG C within one day.

The negative electrode to be used in the lithium secondary battery is manufactured, for example, by coating and drying an anode active material on the negative electrode collector, and if necessary, further includes components such as the conductive agent, the binder and the filler as described above It is possible.

The negative electrode collector is generally made to have a thickness of 3 to 500 mu m. Such an anode current collector is not particularly limited as long as it has conductivity without causing chemical change in the battery, and may be formed of a material such as copper, stainless steel, aluminum, nickel, titanium, fired carbon, surface of copper or stainless steel A surface treated with carbon, nickel, titanium, silver or the like, an 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.

Examples of the negative electrode active material include carbon such as Li _x Fe ₂ O ₃ (0? _X? 1), Li _x WO ₂ (0? _X? 1), Sn _x Me _{1 - x} Me ' _y O _z (Me: Mn, Fe, Pb, Ge; Me': Al, B, P, Si, Group 1, Group 2 and Group 3 elements of the periodic table, y? 3, 1? z? 8) lithium metal lithium alloy silicon-based alloy tin-based alloy SnO, SnO ₂ , PbO, PbO ₂ , Pb ₂ O ₃ , Pb ₃ O ₄ , Sb ₂ O ₃ , A metal oxide such as Sb ₂ O ₄ , Sb ₂ O ₅ , GeO ₂ , GeO ₂ , Bi ₂ O ₃ , Bi ₂ O ₄ and Bi ₂ O ₅ , and other conductive polymer Li-Co-Ni materials can do.

As a separator interposed between an anode and a cathode in a lithium secondary battery to prevent an electrical short, 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. As such a separator, for example, a sheet made of olefin-based polymer glass fiber or polyethylene, such as polypropylene having chemical resistance and hydrophobic property, nonwoven kraft paper, or the like is used. Representative examples currently on the market include Celgard R 2400, 2300 (Hoechest Celanese Corp.), polypropylene separator (Ube Industries Ltd. or Pall RAI), polyethylene series separator (Tonen or Entek) .

In some cases, a gel polymer electrolyte may be coated on the separator to improve the stability of the battery. Representative examples of such a gel polymer include polyethylene oxide, polyvinylidene fluoride, and polyacrylonitrile.

When a solid electrolyte such as a polymer is used as the electrolyte, the solid electrolyte may also serve as a separator.

The lithium salt-containing non-aqueous electrolyte is composed of a non-aqueous electrolyte and a lithium salt. As the non-aqueous electrolyte, a non-aqueous electrolyte, an organic solid electrolyte, an inorganic solid electrolyte and the like are used.

Examples of the nonaqueous electrolyte include N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate , Gamma -butyrolactone, 1,2-dimethoxyethane, 1,2-diethoxyethane, tetrahydroxyfuran, 2-methyltetrahydrofuran, dimethylsulfoxide, 1,3-dioxolane, Diethyl ether, formamide, dimethyl formamide, dioxolane, acetonitrile, nitromethane, methyl formate, methyl acetate, phosphoric acid triester, trimethoxymethane, dioxolane A non-protonic organic solvent such as an ether, a methyl pyrophosphate, or an ethyl propionate is used as the solvent, a sulfone, a methyl sulfolane, a 1,3-dimethyl-2-imidazolidinone, a propylene carbonate derivative, a tetrahydrofuran derivative, .

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, Polymers containing ionic dissociation groups, and the like can 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 , Nitrides, halides and sulfates of Li such as Li ₄ 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, LiSCN, LiC (CF 3 SO 2) 3, (CF 3 SO 2) 2 NLi, chloroborane lithium, lower aliphatic carboxylic acid lithium, 4-phenylborate, imide, and the like can be used.

For the purpose of improving the charge / discharge characteristics and the flame retardancy, the electrolytic solution is preferably mixed with an organic solvent such as pyridine, triethylphosphite, triethanolamine, cyclic ether, ethylenediamine, glyme, 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), FPC (fluoro-propylene carbonate), and the like.

The secondary battery according to the present invention can be used not only in a battery cell used as a power source for a small device but also as a unit cell in a middle or large battery module including a plurality of battery cells.

Also, the present invention provides a battery pack including the battery module as a power source of a middle- or large-sized device, wherein the middle- or large-sized device is an electric vehicle (EV), a hybrid electric vehicle (HEV) An electric vehicle including a plug-in hybrid electric vehicle (PHEV), a power storage device, and the like, but the present invention is not limited thereto.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail with reference to examples. However, the embodiments according to the present invention can be modified into various other forms, and the scope of the present invention should not be construed as being limited to the embodiments described below. Embodiments of the invention are provided to more fully describe the present invention to those skilled in the art.

Example  One

LiNi _{0 .5} Mn _{1 .46} Ti _.04 O ₀ to ₄ in 20 to 50 nm in diameter and then the molybdenum oxide is mixed with 0.5% by weight, a stirrer (Hosokawa Micron Corporation Noblita ^TM) the number of revolutions of the input and, in the 1000 rpm After mixing for 1 hour, the mixture was heat-treated at 500 ° C. for 5 hours in an air atmosphere to prepare LiNi _{0 .5} Mn _{1 .46} Ti _{0 .04} O ₄ that was surface modified with molybdenum as a cathode active material.

The amount of the binder is 95: wherein the surface-modified _{LiNi 0 .5 Mn 1 .46 Ti 0} .04 O 4: conductive material 2.5: after weighing such that the 2.5 into a 2-methyl-pyrrolidone (NMP) mixing ( The cathode mixture was coated on the aluminum foil having a thickness of 20 μm, rolled and dried to prepare a cathode.

A lithium metal foil was used as a cathode, a polyethylene film (Celgard, thickness: 20 占 퐉) was used as a separator, and a non-aqueous electrolyte was prepared using ethylene carbonate, dimethyl carbonate, diethyl carbonate is 1: 2: using the non-aqueous electrolyte in a mixed solvent of a 1 LiPF ₆ is dissolved in 1M, was prepared in 2016 coin cell.

Example  2

A battery was prepared in the same manner as in Example 1, except that tantalum oxide having a diameter of 20 to 70 nm was used in an amount of 0.5 wt% instead of 0.5 wt% of molybdenum oxide.

Comparative Example  One

LiNi _{0 .5} Mn _{1 .46} Ti _{0 .04} O ₄ , which had not undergone any surface modification treatment, was used as a cathode active material.

Manganese flow rate measurement

Coin batteries manufactured in Examples 1 and 2 and Comparative Example 1 were charged and discharged once at a voltage range of 3.5 to 4.9 V at a current of 0.1 C and then charged to 4.9 V at a current of 0.1 C, The battery was disassembled. The anode obtained in the disassembled coin battery was immersed in a container containing 15 mL of the electrolytic solution and then stored in a thermostatic bath at 80 ° C for 2 weeks. The content of manganese dissolved in the electrolytic solution was analyzed by ICP (PerkinElmer 7100 model) .

ICP results Mn elution Mo Ta ppm Ppm ppm Example 1 6200 N / D 190 Example 2 N / D 7130 214 Comparative Example 1 N / D N / D 675

Claims (8)

1. A cathode active material for a lithium secondary battery represented by the following formula (1), wherein the surface layer is represented by the following formula (2)
[Chemical Formula 1]
Li _{1 + a} Ni _b M1 _c Mn _{2 - (b + c)} O _{4 -zda n}
In this formula,
M1 is at least one element selected from the group consisting of Ni, Ti, Co, Al, Cu, Fe, Mg, B, Cr, Zr, Zn and two period transition metals;
A is an anion of -1 or -2,
0.1? 0.3? B? 0.7, 0? C? 0.1, 0.001? D? 0.02, 0? Z? 0.1, 0? N? 0.1.

(2)
Li _{1 + a} Ni _b M1 _c M2 _d Mn _{2 - (b + c + d)} O _{4 -zda n}
In this formula,
M1 is at least one element selected from the group consisting of Ni, Ti, Co, Al, Cu, Fe, Mg, B, Cr, Zr, Zn and two period transition metals;
M2 is one or more selected from the group consisting of V, Cr, Nb, Mo, Ta and W;
A is an anion of -1 or -2;
0.1? 0.3? B? 0.7, 0? C? 0.1, 0.001? D? 0.02, 0? Z? 0.1, 0? N? 0.1.
The method according to claim 1,
Wherein the weight ratio of the transition metal M2 to the total weight of the cathode active material is 0.05 wt% to 5.0 wt%.
The method according to claim 1,
Wherein the cathode active material is a primary particle having an average particle diameter (D50) of 5 to 30 占 퐉.
The method according to claim 1,
Wherein the cathode active material is in the form of a secondary particle having an average particle diameter (D50) of 5 to 30 占 퐉.
The method according to claim 1,
Wherein the surface layer has a thickness of more than 5 nm and a thickness of 100 nm or less.
1. A lithium secondary battery comprising a positive electrode, a negative electrode and an electrolyte,
Wherein the positive electrode comprises the positive electrode active material according to any one of claims 1 to 5.
The method according to claim 6,
Wherein the lithium secondary battery is for 5V voltage.
Mixing a nickel source, a manganese source, and a transition metal M 1 source in a constant composition and heat treating to obtain a particle of Formula 1;
Mixing the particles of formula (I) with a source of transition metal M2 and heat treating,
Annealing the heat treated material,
Each of the heat treatment processes is independently performed at a temperature of 500 to 1250 DEG C,
Characterized in that the annealing step is carried out at 700 to 1000 < RTI ID = 0.0 >
A method for producing the positive electrode active material according to claim 1.