KR101952249B1 - Positive active material for rechargeable lithium battery and rechargeable lithium battery including the same - Google Patents

Abstract

The present invention relates to a cathode active material for a secondary battery and a lithium secondary battery including the same, which can improve the electrochemical characteristics by modifying a pretreated cathode active material subjected to a first heat treatment for a lithium secondary battery, and more particularly, to a lithium secondary battery including a pre- And a lithium secondary battery including the pre-treated cathode active material.

Description

TECHNICAL FIELD [0001] The present invention relates to a positive active material for a lithium secondary battery, and a lithium secondary battery including the positive active material and a lithium secondary battery including the same. BACKGROUND OF THE INVENTION 1. Field of the Invention [0001]

The present invention relates to a cathode active material for a secondary battery and a lithium secondary battery including the same, which can improve electrochemical characteristics by modifying a precursor for a lithium secondary battery, and more particularly, to a lithium secondary battery including the lithium secondary battery, And a lithium secondary battery including the precursor.

As the technology development and demand for mobile devices have increased, the demand for secondary batteries has increased sharply as an energy source. Among such secondary batteries, lithium secondary batteries having high energy density and operating potential, long cycle life, Have been commercialized and widely used.

The lithium secondary battery uses a carbon material such as carbon or graphite as a negative electrode, a chacogenide compound as a positive electrode active material, a porous polypropylene / polyethylene as a separator, and a carbonate-based organic solvent as an electrolyte do.

Typical examples of the chalcogenide compound used as the anode include LiCoO ₂ , LiMn ₂ O ₄ , LiMnO ₂ , LiNiO ₂ , and LiNi _{1 - x} Co _x O ₂ (0 <x <1). Of these, LiCoO ₂ has a good electric conductivity, a high battery voltage of about 3.7 V, excellent lifetime characteristics and stability characteristics, and a discharge capacity of 160 mAh / g, which is commercially available from Sony Corporation It is a typical anode material. However, since LiCoO ₂ is expensive, LiCoO ₂ costs about 30% or more of components in the battery, resulting in poor price competitiveness.

Mn-based electrode materials such as LiMn ₂ O ₄ and LiMnO ₂ are easy to synthesize, are relatively cheap, have less pollution to the environment, and have a battery voltage of 3.9 V or more, which is more attractive than LiCoO _2. Is about 120 mAh / g, which is about 20% smaller than that of LiCoO ₂ , so that it is a problem to manufacture a relatively high capacity, flaky battery. LiNiO ₂ has a disadvantage in that it is cheap in the above-mentioned cathode active material and exhibits the battery characteristic of the highest discharge capacity, but is difficult to synthesize. In the case of LiNi _{1 - x} Co _x O ₂ (o <x <1) powder, the discharge capacity shows a relatively large value ( ₂₀₀ mAh / g) compared to LiCoO ₂ , but the discharge potential is lowered. The battery is relatively inferior to the battery using LiCoO ₂ and has not been fully commercialized since its safety is not completely secured.

Korean Patent Laid-Open No. 10-2001-0004898 discloses a method for increasing the content of nickel in order to increase the capacity per unit volume or increasing the density of the mixture of the cathode active material in the case of the nickel-based composite oxide. However, such a compound has poor processability after heat treatment at a high temperature (600 캜 or higher), and is difficult to apply to a uniform current collector in a battery manufacturing process (slurrying). In addition, , Spherical particles are broken and the performance of the battery is deteriorated, and a cathode active material capable of simultaneously satisfying thermal stability and capacity is required. In the case of the positive electrode active material disclosed in Korean Registered Patent Publication No. 10-0912786, there is a limit in capacity when the content of nickel is low, and a side reaction occurs due to the generation of residual lithium when the lithium source is overcharged for capacity improvement.

Conventionally, in order to optimize the distribution of different kinds of powder, the size ratio of large particles and small particles should be as large as possible. However, as the particle size increases, the thermal stability becomes high. However, Can not be increased. On the contrary, when the particle size is reduced, the capacity is increased, but the thermal stability is deteriorated due to the increase of the specific surface area.

On the other hand, the cathode active material includes a first lithium-nickel composite oxide having a different volume particle distribution and a second lithium-nickel composite oxide, which can improve the filling density compared to the conventional cathode active material, Nickel complex oxide is difficult to solve the deterioration problem. In the case of a process for treating a metal oxide or a composite metal oxide layer formed on the surface of a lithium-nickel composite oxide, the process is not easy.

KR 10-2001-0004898 A1 (2001.10.23) KR 10-0912786 B1 (2009.08.12)

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In order to solve the problems of the prior art as described above, the present invention provides a positive electrode active material for a lithium secondary battery, which improves the structural characteristics of the pretreated positive electrode active material to solve the problem of rate characteristics and deterioration, .
Another object of the present invention is to provide a lithium secondary battery including the above-described cathode active material for a lithium secondary battery.

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In order to achieve the above object, the present invention provides a positive electrode for a lithium secondary battery, which is made of a pre-treated pre-treated positive electrode active material represented by Li _x Ni _0.75 Mn _0.25 O _{2 + y} (0 <x <0.1, 0 ≦ y <2) Thereby providing an active material.
The present invention also provides a lithium secondary battery comprising the above-described cathode active material for a lithium secondary battery.

The present invention improves the stability and capacity of a secondary battery by improving the structure of a cathode active material for a lithium secondary battery by mixing lithium and a small amount of nickel and manganese complex hydroxide with a primary heat treatment to improve the stability and high capacity characteristics of the secondary battery, A cathode active material for a battery, and a lithium secondary battery using the same.

1 is a graph showing the relationship between the mixing ratio of the nickel and manganese complex hydroxide precursors of the present invention mixed with LiOH of Production Example 1 at a molar ratio of 1: 0.1, the pretreated cathode active material subjected to the first heat treatment, and LiOH of Production Example 1 at a molar ratio of 1: , The cathode active material of Comparative Example 2, LiNi _0.8 Mn _0.2 O _2, and Ni (OH) 2 in the X-ray diffraction pattern.

Hereinafter, the present invention will be described in detail.

The present invention relates to a cathode active material for a lithium secondary battery comprising a pre-treated pre-treated cathode active material represented by Li _x Ni _0.75 Mn _0.25 O _{2 + y} (0 <x <0.1, 0 ≦ y <2)

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On the other hand, in the pre-treated cathode active material of the first heat treatment, the x-ray diffraction image of the crystal structure has a peak P ₄₀₀ attributed to the (400) plane, a peak P ₄₄₀ attributed to the (440) has a _222, and included in the X-ray diffraction intensity ratio P ₄₀₀ / P ₂₂₂ is, is included in the range of 1.5 ~ 2.3 P ₄₀₀ / P ₄₄₀ in the range of 1.6 to 2.4 by the primary heat-treated pre-processing the positive electrode active material, P ₂₂₂ / P ₄₄₀ may be included in the range of 0.5 to 1.4.

The pre-treated cathode active material subjected to the first heat treatment may be mixed and subjected to a first heat treatment so that the molar ratio of lithium to the manganese ratio of the nickel manganese precursor (Li: Me) is 0.01 to 1.49: 1, and the first heat treatment is 300 to 800 Lt; 0 &gt; C, at least one of air and air mixture gas, oxygen gas, and oxygen mixture gas. Specifically, the first heat treatment may be performed in an oxygen gas atmosphere at 400 to 700 ° C.

The average particle diameter of the pre-treated cathode active material subjected to the first heat treatment may be 0.01 to 200 탆. Specifically, it may be 0.05 to 100 mu m. When the average particle size of the pre-treated cathode active material subjected to the first heat treatment is smaller than 0.01 탆, the thermal stability is lowered, and when it is larger than 200 탆, the capacity and rate characteristics are deteriorated.

The pre-treated cathode active material subjected to the first heat treatment may be subjected to a second heat treatment at 750 to 1100 ° C in an atmosphere of at least one of air and air mixture gas, oxygen gas, and oxygen mixture gas. Specifically, the precursor may be subjected to a secondary heat treatment in an atmosphere of oxygen gas at 800 to 1000 ° C.

In addition, the pre-treated cathode active material of the first heat treatment is further added with lithium so that the molar ratio of lithium and the molar ratio (Li: LiMe) of the pre-treated cathode active material to the first heat treatment is 0.01 to 1.49: Treated by an atmosphere of at least one of air and air mixed gas, oxygen gas and oxygen mixed gas. Specifically, the pre-treated cathode active material subjected to the first heat treatment may be subjected to a second heat treatment in an atmosphere of oxygen gas at 800 to 1000 ° C.

The cathode active material for a lithium secondary battery produced from the pre-treated pre-treated cathode active material of the present invention improves the structure of a cathode active material for a lithium secondary battery made of nickel and manganese composite oxides to improve the stability and high capacity characteristics of the battery, And the like, and a lithium secondary battery using the positive electrode active material.

The positive electrode active material for a lithium secondary battery of the present invention improves the structure of a pre-treated positive electrode active material made of a nickel or manganese composite oxide to improve the stability and high capacity characteristics of the battery and has excellent cell characteristics such as cycle life.

The present invention also relates to a lithium secondary battery including the above-mentioned cathode active material for a lithium secondary battery. Specifically, the cathode active material for a lithium secondary battery may be represented by the following chemical formula.

[Chemical Formula 1]

LiNi _x Mn _y M _z O ₂

Each M is independently at least one metal selected from Co, Al, Mg, Cr, Fe, Ti, Zr, Mo and alloys thereof.

x = 1-y-z, 0.1? y? 0.9 and 0? z? 0.5

The lithium secondary battery may be composed of a cathode, a cathode, a separator, and an electrolytic solution containing a lithium salt.

The positive electrode is prepared, for example, by applying a mixture of a positive electrode active material for a lithium secondary battery, a conductive material and a binder on a positive electrode current collector, and then drying the resultant. Optionally, a filler may be further added to the mixture.

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 change in the battery, and may be formed of a material such as stainless steel, aluminum, nickel, titanium, sintered carbon, or a surface of aluminum or stainless steel Treated with 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 conductive material is usually added in an amount of 1 to 50% 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 changes in the battery, for example, graphite such as natural graphite or artificial 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.

The binder is a component that 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 50 wt% 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, various copolymers and the like.

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

The negative electrode is manufactured by applying and drying an anode active material on an anode current collector, and if necessary, may further include the above-described components.

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 non-graphitized carbon and graphite carbon; Al, B, P, Si, Group 1 of the periodic table, LieFe2O3 (0? Y? 1), LiyWO2 (0? Y? 1), SnxMe1-xMe'yOz (Me: Mn, Fe, Pb, 2 group, Group 3 element, and halogen; 0? X? 1; 0? Y? 1; 1? Z? 8); Lithium metal; Lithium alloy; Silicon-based alloys; Tin alloy; Metal oxides such as SnO, SnO2, PbO, PbO2, Pb2O3, Pb3O4, Sb2O3, Sb2O4, Sb2O5, GeO, GeO2, Bi2O3, Bi2O4, and Bi2O5; Conductive polymers such as polyacetylene; Li-Co-Ni-based materials and the like can be used.

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 a 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 electrolyte solution containing a lithium salt is composed of an electrolyte solution and a lithium salt. Specifically, the electrolyte solution may be a non-aqueous organic solvent, an organic solid electrolyte, an inorganic solid electrolyte, or the like.

The non-aqueous organic solvent may specifically be selected from the group consisting of vinylene carbonate, vinylethylene carbonate, phosphazene and fluorobenzene, and more specifically, N-methyl-2-pyrrolidinone, propylene carbonate, ethylene But are not limited to, carbonates, butylene carbonate, dimethyl carbonate, diethyl carbonate, gamma-butylolactone, 1,2-dimethoxyethane, tetrahydroxyfuran, 2-methyltetrahydrofuran, Dimethylsulfoxide, 1,3-dioxolane, formamide, dimethylformamide, dioxolane, acetonitrile, nitromethane, methyl formate, methyl acetate, triester phosphate, trimethoxymethane, dioxolane derivative, Propanecarbonate derivatives, tetrahydrofuran derivatives, ethers, methyl pyrophosphate, ethyl propionate, and the like may be used. There.

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, such as Li3N, LiI, Li5NI2, Li3N-LiI-LiOH, LiSiO4, LiSiO4- LiI- LiOH, Li2SiS3, Li4SiO4, Li4SiO4- LiI- LiOH, Li3PO4- Li2S- Nitrides, halides, sulfates and the like can be used

The lithium salt is a substance that is soluble in the non-aqueous electrolyte. For example, LiCl, LiBr, LiI, LiClO4, LiBF4, LiB10Cl10, LiPF6, LiCF3SO3, LiCF3CO2, LiAsF6, LiSbF6, LiAlCl4, CH3SO3Li, CF3SO3Li, 2NLi, chloroborane lithium, lower aliphatic carboxylic acid lithium, 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, aluminum trichloride, . In some cases, a halogen-containing solvent such as carbon tetrachloride, ethylene trifluoride or the like may be further added to impart flammability, and a carbon dioxide gas may be further added to improve the high-temperature storage characteristics.

The lithium secondary battery can be manufactured by a known method. Specifically, in order to produce a positive electrode, a positive electrode active material, a positive electrode conductive agent, and a binder are suspended in a suitable solvent, and the suspended slurry is applied to a positive electrode current collector and dried to produce a positive electrode active material- Can be produced. More specifically, the suspended slurry is coated on an aluminum foil to a thickness of 25 mu m to form a thin electrode plate, dried at 110 to 135 DEG C for 2 hours or more, and then pressed to produce a positive electrode. As the conductive agent, it is preferable to use carbon black. Examples of the binder include polytetrafluoroethylene, polyvinylidene fluoride, polyvinyl fluoride, polyacrylonitrile, nitrile rubber, polybutadiene, polystyrene, styrene butadiene rubber, , Butyl rubber, hydrogenated styrene-butadiene rubber, nitrocellulose, and carboxymethylcellulose. At this time, the content of the cathode active material, the conductive agent, the binder and the solvent can be used at a level commonly used in a lithium secondary battery.

On the other hand, any separator can be used as long as it is commonly used in a lithium secondary battery. Specifically, any insulating film having a porosity of 30 to 60 vol% electrochemically stable in a lithium secondary battery can be used.

The organic electrolytic solution may include a lithium salt and an organic solvent. LiBF 4, LiClO 4, LiN (CF 3 SO 2) 2, LICF 3 SO 3, LIC (CF 3 SO 3) 2, LiCF 3 SO 3, and LiCF 3 SO 3 are preferably used as the lithium salt, 3, and LiAsF6 may be used. The concentration of the lithium salt is preferably 0.4M to 1.5M, and the concentration of the lithium salt in the above range is highest in the ionic conductivity of the lithium salt in the organic electrolyte solution.

The organic solvent may be one having a high dielectric constant (polarity) and a low viscosity as well as a low reactivity with lithium metal in order to increase ion dissociation and smooth ion conduction. Concretely, it is preferable to use two or more mixed solutions composed of a solvent having a high dielectric constant and a high viscosity and a solvent having a low dielectric constant and a low viscosity. For example, it is preferable to use two or more mixed solutions of a cyclic type selected from the group consisting of polyethylene carbonate, ethylene carbonate, Carbonate, and a mixture of a chain carbonate selected from the group consisting of dimethyl carbonate and diethyl carbonate.

Hereinafter, the present invention will be described in more detail with reference to Examples. However, the embodiments are only examples of the present invention, and the scope of the present invention is not limited to the scope of the embodiments.

[Example]

Reaction 1: Synthesis of cathode active material (Li / Me 1.1M) after the first heat treated pretreatment cathode active material synthesis (Li / Me 0.1M)

Li-containing compound as a NiSO4-xH2O as a Mn-containing compound and a compound containing LiOH, Ni was used for MnSO ₄ -H ₂ O,

Ni sulfide and Mn sulfide were prepared by coprecipitation method. Specifically, 0.75 mol and 0.25 mol of Ni and Mn sulfides were respectively dissolved in distilled water to prepare a 2.3 M nickel manganese precursor solution.

Then, 2 to 4 M sodium hydroxide aqueous solution and ammonia water were mixed and stirred at a pH of 11 to 14 at a temperature of 55 to 65 ° C at a speed of 700 to 1000 rpm, but the average residence time of the solution was coprecipitated for 6 to 15 hours.

The coprecipitated precursor was washed with water, dried, mixed with LiOH in a molar ratio of 1: 0.1, and then subjected to a first heat treatment at 600 ° C for 10 hours at a rate of 1 to 5 ° C / min in an oxygen atmosphere.

The pre-treated cathode active material subjected to the first heat treatment was mixed with LiOH at a molar ratio of 1: 1.1, and then subjected to a secondary heat treatment at 800 to 1000 ° C for 4 to 15 hours at a temperature rising rate of 1 to 5 ° C / min in an oxygen atmosphere, Thereby preparing LiNi _0.75 Mn _0.25 O ₂ .

Preparation Example 2: Synthesis of cathode active material (Li / Me 0.6M) and secondary heat-treated cathode active material synthesis (Li / Me 0.6M)

The cathode-treated precursor was mixed with LiOH at a molar ratio of 1: 0.6 and mixed in a molar ratio of 1: 0.6 of the pre-treated cathode active material and LiOH to prepare a secondary heat-treated cathode active material .

Preparation Example 3: Synthesis of Li / Me 0.1M Secondary Heat-treated Cathode Active Material Synthesis After Pretreatment Cathode Active Material Synthesis (Li / Me 1.1M)

The same procedure as in Preparation Example 1 was repeated except that the coprecipitated precursor was mixed at a molar ratio of LiOH to 1: 1.1 and mixed at a molar ratio of 1: 0.1 of LiOH to the pre-treated cathode active material subjected to the first heat treatment. To prepare an active material.

Comparative Example 1: Synthesis of Lithium composite cathode active material (Li / Me 1.0M)

LiOH as the Li-containing compound, NiSO ₄ -xH ₂ O as the Ni-containing compound and MnSO ₄ -H ₂ O as the Mn-containing compound,

Ni sulfide and Mn sulfide were prepared by coprecipitation method. Specifically, 0.75 mol and 0.25 mol of Ni and Mn sulfides were respectively dissolved in distilled water to prepare a 2.3 M nickel manganese precursor solution.

Then, 2 to 4 M sodium hydroxide aqueous solution and ammonia water were mixed and stirred at a pH of 11 to 14 at a temperature of 55 to 65 ° C at a speed of 700 to 1000 rpm, but the average residence time of the solution was coprecipitated for 6 to 15 hours.

The coprecipitated precursor was washed with water, dried and mixed with LiOH at a molar ratio of 1: 1, and then subjected to a first heat treatment at 600 ° C for 10 hours under an oxygen atmosphere at a rate of 1 to 5 ° C / min. LiNi _0.75 Mn _0.25 O ₂ was prepared by secondary heat treatment at 800-1000 캜 for 4-15 hours at a heating rate of 캜 / min.

Comparative Example 2: Synthesis of Lithium composite cathode active material having no precursor 2-stage annealing (Li / Me 1.2M)

A cathode active material for a lithium secondary battery was prepared in the same manner as in Comparative Example 1 except that the coprecipitated precursor and LiOH were mixed in a molar ratio of 1: 1.2.

Comparative Example 3: Synthesis of Lithium composite cathode active material having no precursory two-stage annealing (Li / Me 1.4M)

A cathode active material for a lithium secondary battery was prepared in the same manner as in Comparative Example 1, except that the coprecipitated precursor and LiOH were mixed at a molar ratio of 1: 1.4.

Experimental Example 1: Comparison of chemical characteristics of the present invention and conventional cathode active materials at room temperature (25 ° C)

In order to compare the battery chemical characteristics of the precursor heat treatment of the present invention and the conventional non-heat-treated applied positive electrode active material at room temperature, a lithium secondary battery comprising the cathode active materials of Production Examples 1 to 3 and Comparative Examples 1 to 3 was tested under the following conditions Were measured and compared. The results are shown in Table 1. &lt; tb &gt; &lt; TABLE &gt;

Comparison of chemical properties at room temperature (25 ℃) Item 0.2C / 1.0C (3.0-4.3V) 0.2C / 1.0C (3.0-4.4V) Discharge capacity (mAh / g) efficiency(%) Discharge capacity (mAh / g) efficiency(%) Manufacturing example One 155.2 99.26 178.8 99.17 2 148.7 99.58 169.7 99.12 3 140.4 99.04 161.4 98.84 Comparative Example One 152.7 99.11 173.9 99.24 2 149.6 99.66 169.1 99.38 3 127.8 99.26 139.2 99.05

As shown in Table 1, the lithium secondary battery including the cathode active material of Production Example 1 of the present invention had a discharge capacity at 0.2C / 1.0C (3.0 to 4.3V) and a discharge capacity at 0.2C / 1.0C ), And it was confirmed that the efficiency at 0.2C / 1.0C (3.0 to 4.3V) and the efficiency at 0.2C / 1.0C (3.0 to 4.4V) were also excellent levels .

Experimental Example 2: X-ray diffraction analysis of the precursor of the present invention and various compounds

The precursor of the present invention and the LiOH of Production Example 1 were mixed at a molar ratio of 1: 0.1, followed by mixing at a molar ratio of 1: 1.1 with LiOH of Preparation Example 1, a pre-treated cathode active material subjected to a first heat treatment, , A positive electrode active material of Comparative Example 2, a Ni _0.8 Mn _0.2 O ₂ and a Ni (OH) 2 were subjected to X-ray diffraction analysis using an X-ray diffraction method (Ultima, Rigaku) 3 mA, 10 to 90 deg, a step width of 0.01 deg, and a step scan. The results of the analysis are shown in Fig.
As shown in FIG. 1, the pre-treated cathode active material of the present invention has a peak P ₄₀₀ attributed to the (400) plane, a peak P ₄₄₀ attributed to the (440) plane, and a peak P ₂₂₂ attributed to the (222) Lt; / RTI &gt;
A primary X-rays by the heat-treated pre-processing the positive electrode active material diffraction intensity ratio P ₄₀₀ / P _222, and is included in the range of 1.5 to 2.3 P ₄₀₀ / P ₄₄₀ contained in the range of 1.6 to 2.4, the P ₂₂₂ / P ₄₄₀ 0.5 to 1.4. &Lt; tb &gt;&lt; TABLE &gt;

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Claims (11)

A positive electrode active material for a lithium secondary battery, which is produced from a pre-treated pre-treated positive electrode active material represented by Li _x Ni _0.75 Mn _0.25 O _{2 + y} (0 <x <0.1, 0 ≦ y <2)
And the primary heat-treated pre-processing the positive electrode active material is an average particle diameter of 0.05 ~ 100μm, the crystal structure of x-ray diffraction is, the peak P ₄₄₀ and 222 attributable to the peak P _400, (440) plane attributed to surface 400 Gt; P &_lt; / RTI &gt;
Wherein the X-ray diffraction intensity ratio P ₄₀₀ / P ₂₂₂ of the pre-treated cathode active material subjected to the first heat treatment is in the range of 1.5 to 2.3, P ₄₀₀ / P ₄₄₀ is in the range of 1.6 to 2.4, P ₂₂₂ / P ₄₄₀ is in the range of 0.5 To 1.4. &Lt; RTI ID = 0.0 &gt; 1. &lt; / RTI &gt; 1) preparing a precursor by coprecipitation of a nickel manganese precursor solution with an aqueous solution of sodium hydroxide and ammonia water;
2) mixing the lithium and the nickel manganese precursor at a molar ratio (Li: Me) of 0.1: 1, and performing a first heat treatment in an atmosphere of at least one of air and air mixture gas, oxygen gas and oxygen mixture gas at 300 to 800 ° C step;
3) Lithium is further mixed so that the mole ratio (Li: LiMe) of lithium and the pre-treated cathode active material subjected to the first heat treatment is 1.1: 1, and at least one of air and air mixture gas, oxygen gas, And a second heat treatment step of subjecting the resultant mixture to an atmospheric heat treatment.
delete delete delete delete delete delete A lithium secondary battery comprising the cathode active material for a lithium secondary battery of claim 1 or a cathode active material for a lithium secondary battery produced by the method of claim 2. 10. The method of claim 9,
Wherein the positive electrode active material for a lithium secondary battery is represented by the following formula.
[Chemical Formula 1]
LiNi _x Mn _y MzO ₂
Each M is independently at least one metal selected from Co, Al, Mg, Cr, Fe, Ti, Zr, Mo and alloys thereof.
x = 1-yz, 0.1? y? 0.9, 0? z? 0.5 10. The method of claim 9,
Wherein the lithium secondary battery comprises at least one non-aqueous liquid electrolyte selected from the group consisting of vinylene carbonate, vinylethylene carbonate, phosphazene, and fluorobenzene.

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