JP2003242976A - Manufacturing method of positive active material for lithium secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a positive active material for lithium secondary battery that is superior in initial capacity, initial charge and discharge efficiency, charge and discharge cycle durability, and safety or the like. <P>SOLUTION: This is a manufacturing method of a positive active material for lithium secondary battery that is expressed by the formula Li<SB>p</SB>Ni<SB>x</SB>Co<SB>y</SB>Mn<SB>z</SB>O<SB>r</SB>(0.9≤p≤1.3, 0.2≤x<0.5, 0.20<y<0.40, 0.2≤z≤0.5, 0.8≤x+y+z≤1, 1≤r≤2). A mixture of a compound oxide that has a formula Ni<SB>x</SB>Co<SB>y</SB>Mn<SB>z</SB>O<SB>r</SB>and a specific surface area of 10-150 m<SP>2</SP>/g and a lithium compound is fired in the oxygen- containing atmosphere at 600-1000°C. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a lithium secondary battery which can be used in a wide voltage range, has a high initial capacity, a high initial charge / discharge efficiency, and excellent charge / discharge cycle durability and safety. The present invention relates to a method for manufacturing a positive electrode active material.

[0002]

2. Description of the Related Art In recent years, various electronic devices have been made portable.
With the progress of cordless technology, the demand for small, lightweight, high energy density non-aqueous electrolyte secondary batteries has increased, and the development of non-aqueous electrolyte secondary batteries with superior characteristics has been desired. ing.

Generally, a positive electrode active material used in a non-aqueous electrolyte secondary battery is composed of a composite oxide in which transition metal such as cobalt, nickel and manganese is solid-dissolved in lithium which is a main active material. Electrode characteristics such as electric capacity, reversibility, operating voltage, and safety differ depending on the type of transition metal used.

For example, LiCoO ₂ , LiNi _0.8 Co
R-3 with cobalt or nickel dissolved as _0.2 O ₂
Non-aqueous electrolyte secondary batteries using m rhombohedral rock salt layered composite oxide as a positive electrode active material each have a thickness of 140 to 160 mAh / g.
And a relatively high capacity density of 180 to 200 mAh / g can be achieved, and good reversibility is exhibited in a high voltage range of 2.5 to 4.3 V. However, when the battery is heated, there is a problem that the battery is likely to generate heat due to the reaction between the positive electrode active material and the electrolyte solvent during charging.

In Japanese Unexamined Patent Publication No. 10-027611, L
In order to improve the characteristics of iNi _0.8 Co _0.2 O ₂ , for example, Li
The proposal of Ni _0.75 Co _0.20 Mn _0.05 O ₂ and the production method using an ammonium complex of the positive electrode active material intermediate are disclosed. Further, JP-A-10-81521 proposes a production method using a chelating agent of a nickel-manganese binary hydroxide raw material for a lithium battery having a specific particle size distribution. However, none of these conventional positive electrode active materials has yet been obtained, which has a high initial capacity, high initial charge / discharge efficiency, and satisfactory charge / discharge cycle durability and safety at the same time.

On the other hand, a non-aqueous electrolyte secondary battery using a spinel-type composite oxide composed of LiMn ₂ O _{4 made of} relatively inexpensive manganese as a raw material is a positive electrode active material during charging and an electrolyte. It does not generate heat easily depending on the reaction with the solvent. However, its charge / discharge capacity is 100 to 120 mAh / compared with the above cobalt-based and nickel-based active materials.
There is also a problem that it is as low as g and the charge / discharge cycle durability is poor, and there is also a problem that it rapidly deteriorates in a low voltage region of less than 3V.

Further, orthorhombic Pmnm system or monoclinic C
Cells with 2 / m based LiMnO ₂ of, LiMn _{0 .95} Cr _0.05 O ₂ or LiMn _0.9 Al _0.1 O _2, safety is high, although the example in which the initial capacity is highly expressed is, due to charge-discharge cycles There is a problem that the crystal structure is apt to change and the cycle durability becomes insufficient.

[0008]

SUMMARY OF THE INVENTION The present invention has been made to solve the problems of the above-mentioned conventional positive electrode active material for non-aqueous electrolyte secondary batteries, and its purpose is to provide a wide voltage range. Provided is a method for manufacturing a positive electrode for a non-aqueous electrolyte secondary battery, which can be used in a range, has high initial capacity, high initial charge / discharge efficiency, charge / discharge cycle durability, and high safety. To do.

[0009]

In order to achieve the above object, the inventors of the present invention have conducted extensive studies and as a result, as a starting material, a complex oxide containing a specific metal component containing manganese and having specific physical properties. It was found that a positive electrode active material for a lithium secondary battery having a specific composition, which is produced by firing a mixture of the composite oxide and a lithium compound in an oxidizing atmosphere, achieves the above-mentioned object by using The present invention has been accomplished, and the present invention has the following gist. (1) In _{formula, Li p Ni x Co y Mn} z O r (0.9 ≦ p ≦
1.3, 0.2 ≦ x <0.5, 0.20 <y <0.4
0, 0.2 ≦ z ≦ 0.5, 0.8 ≦ x + y + z ≦ 1, 1
A method of manufacturing a positive electrode active material for a lithium secondary battery represented by the formula: ≦ r ≦ 2, which comprises a general formula of Ni _x Co _y Mn _z O _r (p,
x, y, z, and r are the same as above), and a mixture of a composite oxide having a specific surface area of 10 to 150 m ² / g and a lithium compound in an oxygen-containing atmosphere at 600 to 100.
A method for producing a positive electrode active material for a lithium secondary battery, which comprises firing at 0 ° C. (2) A method for producing a positive electrode active material for a lithium secondary battery, wherein y = 0 and 0.9 / 1 ≦ x / z ≦ 1 / 0.9 in the general formula described in (1) above. (3) The composite oxide is powder X using CuKα rays
The method for producing a positive electrode active material for a lithium secondary battery according to (1) or (2), wherein the half value width of the diffraction angle of 2θ = 36.5 ± 1 ° of line diffraction is 0.5 to 2.0 °. . (4) The complex oxide is a complex hydroxide obtained by coprecipitating an aqueous mixed solution containing each metal component contained therein with an alkali at 350 to 600 ° C., and the above (1) to (3). (4) A method for producing a positive electrode active material for a lithium secondary battery according to any one of (1) to (4). (5) The press density of the composite oxide is 2.3 to 3.2 g.
/ Cm ^{3 The} method for producing a positive electrode active material for a lithium secondary battery according to any one of the above (1) to (4). (6) The complex oxide has a spherical shape or an elliptic spherical shape and has an average particle diameter of 2 to 14 μm.
The method for producing a positive electrode active material for a lithium secondary battery according to any one of (5). (7) The method for producing a positive electrode active material for a lithium secondary battery according to any of (1) to (6), wherein the lithium compound is lithium carbonate having an average particle size of 5 to 30 μm. (8) a portion of the oxygen atoms are substituted with fluorine atoms, the general _{formula, Li p Ni x Co y Mn} z O q F a (p, x, y and z is as defined above, 0 <a ≦ 0.40, 1.8 ≦ q ≦ 2.
The method for producing a positive electrode active material for a lithium secondary battery according to any one of (1) to (7) above, which is represented by 2).

Thus, according to the present invention, there is provided a positive electrode active material for a lithium secondary battery having the following characteristics. 1. High initial discharge capacity per unit weight. 2. High initial charge / discharge efficiency. 3. High initial discharge capacity per unit volume (which is proportional to the press density of the positive electrode powder). 4. High charge / discharge cycle stability. 5. High safety.

The mechanism by which the present invention provides a positive electrode active material having the above-mentioned excellent properties is not clear. However, the specific composite oxide used in the present invention has a lithiation reaction activity. It is considered that this is because the lithiation in the aggregate hydroxide progresses uniformly and a dense crystal structure is generated because of the extremely high value. The present invention will be described in more detail below.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The positive electrode active material for a lithium secondary battery produced in the present invention has the following general formula,
Li _p Ni _x Co _y Mn _z O _r . In this general formula, p, x, y, z and r are the same as described above.
Above all, 0.97 ≦ p ≦ 1.05, 0.25 ≦ x ≦
0.45, 0.20 <y <0.40, 0.25 ≦ z ≦
0.45 and 0.95 ≦ x + y + z ≦ 1 are preferable. When y = 0, 0.95 / 1 ≦ x / z ≦ 1/0.
95 is preferred. Furthermore, the positive electrode active material of the present invention may contain other elements within a range that does not hinder its characteristics.

In the present invention, the production of the above-mentioned positive electrode active material for a lithium secondary battery includes, as a starting material, each metal component contained in the composite oxide and has a specific surface area of 10 to 150 m ^2.
A complex oxide of / g is used. The content of each metal component contained in the composite oxide is determined according to the ratio of each component of the target positive electrode active material.

The specific surface area of the above composite oxide is important,
When the specific surface area is less than 10 m ² / g, the discharge capacity per initial unit weight decreases, and conversely, when it exceeds 150 m ² / g, the discharge capacity per initial unit volume decreases,
A positive electrode active material excellent in the object of the present invention cannot be obtained. Among them, the specific surface area is preferably 20 to 100 m ² / g.

Further, the above-mentioned composite oxide further comprises CuK.
2θ = 36.5 ± 1 ° of powder X-ray diffraction using α ray
When the full width at half maximum of the diffraction angle at has a predetermined range,
It was found that excellent properties were obtained in terms of initial volume capacity density, initial weight capacity density, initial charge / discharge efficiency and cycle durability. Thus, in the above-mentioned composite oxide, the half width of the diffraction angle at 2θ = 36.5 ± 1 ° of the powder X-ray diffraction using CuKα ray is preferably 0.5 to 2.0 °, and particularly 0.7 ~ 1.5 ° is preferred.

Further, the above-mentioned composite oxide of the present invention preferably has a press density of 2.3 to 3.2 g / cm ³ . When the press density is less than 2.3 g / cm ³ , the initial volumetric capacity density of the positive electrode after lithiation becomes low, and conversely, when it is higher than 3.2 / cm ³ , the initial volume of the positive electrode after lithiation becomes higher. It is not preferable because the weight capacity density is lowered and the high rate discharge characteristic is lowered.
Above all, the press density of the composite oxide is 2.4 to 3.0.
g / cm ³ is preferred.

In the present invention, the press density means
About 5 g of complex oxide powder or positive electrode powder is 3.14 cm.
^It means the value obtained from the volume and the weight by applying a pressure of 6T for ² . In the present invention, in the particles of the composite oxide, in the SEM observation, innumerable primary particles aggregate and
It is preferable that secondary particles are formed and the shape thereof is spherical or elliptical from the viewpoint of improving battery characteristics and pressing density.

The method for producing the above complex oxide of the present invention is not necessarily limited, and, for example, heating the complex carbonate, complex basic carbonate, complex organic acid salt, or complex oxide produced by the coprecipitation method. Can be manufactured by. Among them, a composite hydroxide obtained by coprecipitating an aqueous mixed solution containing nickel, cobalt, and manganese with an alkali at 350 to 600 ° C. in an oxidizing atmosphere (hereinafter referred to as coprecipitated composite It has been found that an oxide) is also suitable. Such a coprecipitated complex oxide has a specific surface area required for the above complex oxide, CuK, by changing the composition of the mixed aqueous solution, coprecipitation and firing conditions.
2θ = 36.5 ± 1 ° of powder X-ray diffraction using α ray
It is possible to easily satisfy the full width at half maximum of the diffraction angle and the press density.

In the case of producing the above coprecipitated complex oxide, a mixed aqueous solution containing each metal component contained in the complex oxide such as nickel, cobalt and manganese, and an alkali, preferably an aqueous solution of an alkali metal hydroxide. By reacting with and coprecipitating, a composite hydroxide containing Ni _x Co _y Mn _z O ₂ (hereinafter, also referred to as a coprecipitated composite hydroxide) is generated. Examples of the mixed aqueous solution containing each metal component include a sulfate aqueous solution, a nitrate aqueous solution, and an oxalate aqueous solution. The concentration of the metal salt of each metal component in the mixed aqueous solution varies depending on the composition of the positive electrode active material to be produced, but is preferably 0.5 to 2.5 mol / L in each case. The aqueous solution of alkali metal hydroxide is preferably exemplified by an aqueous solution of sodium hydroxide, potassium hydroxide or lithium hydroxide. The concentration of this aqueous solution of alkali metal hydroxide is preferably 15 to 35 mol / L.

In the production of the above coprecipitated composite hydroxide, it is preferable that a dense and spherical composite hydroxide be obtained by coexisting with ammonium ions. Preferred examples of the ammonium ion supplier include aqueous ammonia, aqueous ammonium sulfate solution, ammonium nitrate and the like. Ammonia or ammonium ion concentration is 4
-20 mol / L is preferable.

The production of the coprecipitated composite hydroxide in the present invention will be described more specifically. A mixed aqueous solution containing each metal component contained in the composite oxide, an alkali metal hydroxide aqueous solution, and preferably An ammonium ion supplier is continuously or intermittently supplied to the reaction tank, and the temperature of the slurry in the reaction tank is controlled to preferably 30 to 70 ° C. while vigorously stirring the slurry in the reaction tank. The pH of the slurry in the reaction tank is preferably within a predetermined range of 10 to 13.
It is maintained by controlling the supply rate of the aqueous solution of the alkali hydroxide so that

The residence time in the reaction tank is 0.5 to 30.
Time is preferable, and 5 to 15 hours is particularly preferable. The slurry concentration is preferably 500 to 1200 g / L.
In the present invention, a coprecipitated composite hydroxide having a desired average particle size, particle size distribution, and particle density can be obtained by appropriately controlling the above temperature, pH, residence time, slurry concentration and ion concentration in the slurry. You can The reaction is carried out in multiple steps rather than the reaction in one step, whereby spherical particles having a fine and preferable particle size distribution can be obtained.

The obtained coprecipitated composite hydroxide may be directly calcined to form the coprecipitated composite hydroxide, but the coprecipitated composite hydroxide is treated with an oxidizing agent to form a composite. It is also possible to produce a composite oxide by converting it into a composite oxyhydroxide containing each metal component contained in the oxide and calcining this. As a preferred means for converting the composite hydroxide into a composite oxyhydroxide, air, sodium hypochlorite, hydrogen peroxide solution, potassium persulfate, an oxidizer such as bromine in a composite hydroxide slurry is used. It is supplied and reacted at 20 to 60 ° C. for 5 to 20 hours.

The composite hydroxide or composite oxyhydroxide obtained above is preferably used at a temperature of 350 to 600.
℃, particularly preferably 400 ~ 500 ℃, preferably,
A coprecipitated complex oxide having Ni _x Co _y Mn _z O ₂ can be produced by firing in an oxygen-containing atmosphere for 4 to 24 hours. The composite oxide preferably has an average particle size of 2-14.
It is preferred to have a thickness of .mu.m, especially 3 to 10 .mu.m.

The coprecipitated composite oxide having Ni _x Co _y Mn _z O ₂ thus obtained is then mixed with a lithium compound and calcined. In this case, it is preferable to use lithium carbonate or lithium hydroxide as the lithium compound in order to uniformly perform lithiation. Firing is performed at 600 to 1000 ° C. in an oxidizing atmosphere to produce the intended positive electrode active material. As the oxidizing atmosphere, it is preferable to use an oxygen-containing atmosphere containing an oxygen concentration of preferably 15% by volume or more, particularly 40% by volume or more. Although the firing time depends on the firing temperature, it is preferably 4 to 48 hours, particularly 8 to 20 hours.
It's time.

In the present invention, when the mixture of the composite oxide and the lithium compound is fired, when lithium hydroxide is used, preliminary firing is performed in order to uniformly mix the lithium compound with the composite oxide. preferable. The pre-baking is performed in an oxidizing atmosphere, preferably 450 to 550 ° C.
Therefore, it is suitable to carry out for 4 to 20 hours. When lithium carbonate is used as the lithium compound, a positive electrode active material having good characteristics can be obtained by one-step firing, so that the above pre-firing can be omitted, which is particularly preferable.

Thus, the general formula Li _p Ni _x Co _y Mn _z O
A positive electrode active material represented by _r (p, x, y, z, and r are the same as above) is produced. In the positive electrode active material of the present invention, some of the oxygen atoms can be replaced with fluorine atoms, and the positive electrode active material in this case has the general formula: Li _p Ni _x
Co _y Mn _z O _{q Fa} (a and q are the same as above).
Among them, it is preferable that 0.05 <a ≦ 0.30. The positive electrode active material in which a part of the oxygen atoms is replaced by fluorine atoms has improved safety. The positive electrode active material in which a part of the oxygen atoms are substituted with fluorine atoms can be produced, for example, by mixing the composite oxide, the lithium compound, and lithium fluoride, and firing the mixture.

The method for obtaining a positive electrode for a lithium secondary battery from the positive electrode active material of the present invention can be carried out according to a conventional method.
For example, the positive electrode mixture is formed by mixing the powder of the positive electrode active material of the present invention with a carbon-based conductive material such as acetylene black, graphite, and Ketchen black, and a binder. Polyvinylidene fluoride, polytetrafluoroethylene, polyamide, carboxymethyl cellulose, acrylic resin or the like is used as the binder. A slurry prepared by dispersing the above positive electrode mixture in a dispersion medium such as N-methylpyrrolidone is applied to a positive electrode current collector such as an aluminum foil, dried, and press-rolled to form a positive electrode active material layer on the positive electrode current collector. Form.

In a lithium battery using the positive electrode active material of the present invention as a positive electrode, a carbonate ester is preferable as the solvent of the electrolyte solution. The carbonic acid ester may be cyclic or linear. Examples of the cyclic carbonic acid ester include propylene carbonate and ethylene carbonate (EC). As a chain carbonic acid ester, dimethyl carbonate,
Examples include diethyl carbonate (DEC), ethylmethyl carbonate, methylpropyl carbonate, methylisopropyl carbonate and the like.

The above carbonic acid esters may be used alone or in admixture of two or more. Moreover, you may use it, mixing with another solvent. Further, depending on the material of the negative electrode active material, the combined use of a chain carbonic acid ester and a cyclic carbonic acid ester may improve the discharge characteristics, cycle durability, and charge / discharge efficiency. Further, vinylidene fluoride-hexafluoropropylene copolymer (for example, Atochem Kainer), vinylidene fluoride-perfluoropropyl vinyl ether copolymer are added to these organic solvents, and the following solutes are added to form a gel polymer electrolyte. Is also good.

As the solute of the electrolyte solution, ClO ₄ −,
CF ₃ SO ₃ −, BF ₄ −, PF ₆ −, AsF ₆ −, SbF ₆
-, CF ₃ CO ₂ -, it is preferable to use the (CF ₃ SO _{2) 2} N-, etc. or any one of a lithium salt and anion. The above electrolyte solution or polymer electrolyte is
It is preferable to add an electrolyte composed of a lithium salt to the solvent or the solvent-containing polymer at a concentration of 0.2 to 2.0 mol / L. If it deviates from this range, the ionic conductivity will decrease, and the electric conductivity of the electrolyte will decrease. More preferably, 0.5 to 1.5 mol / L is selected. Porous polyethylene or porous polypropylene film is used for the separator.

The negative electrode active material of a lithium battery using the positive electrode active material of the present invention as a positive electrode is a material capable of absorbing and desorbing lithium ions. The material forming the negative electrode active material is not particularly limited, and examples thereof include lithium metal, lithium alloys, carbon materials, oxides mainly containing metals of Groups 14 and 15 of the periodic table, carbon compounds, silicon carbide compounds, silicon oxide compounds, and sulfides. Examples include titanium and boron carbide compounds.

As the carbon material, those obtained by thermally decomposing organic matter under various thermal decomposition conditions, artificial graphite, natural graphite, soil graphite, expanded graphite, scaly graphite and the like can be used. Further, as the oxide, a compound mainly containing tin oxide can be used. Copper foil, nickel foil, or the like is used as the negative electrode current collector. The shape of the lithium battery using the positive electrode active material in the present invention is not particularly limited. A sheet shape (so-called film shape), a folding shape, a winding type bottomed cylindrical shape, a button shape, etc. are selected according to the application.

[0034]

EXAMPLES Next, the present invention will be described with reference to specific Examples 1 to 8 and Comparative Example 1, but the present invention is not limited to these Examples. In the examples, X-ray diffraction analysis was performed using RINT-2000 type manufactured by Rigaku Co., Ltd. using a Cu-Kα tube, tube voltage of 40 KV, tube current of 40 mA, light receiving slit of 0.15 mm, sampling width of 0.02 °. It went on condition of. In the present invention, particle size analysis is performed by Leed + Northrup M
icrotrac HRA X-100 type was used.

Example 1 A sulfate aqueous solution containing nickel sulfate, cobalt sulfate, and manganese sulfate, an aqueous ammonia solution, and an aqueous sodium hydroxide solution were continuously added to a reaction tank, and the pH of the slurry in the reaction tank was 11, and the temperature was adjusted. It was supplied with vigorous stirring in the reaction tank so that the temperature became 50 ° C. A nickel-cobalt-manganese composite hydroxide powder was obtained by adjusting the amount of liquid in the reaction system by an overflow method, filtering the overflowed coprecipitated slurry, washing with water, and then drying at 120 ° C.

This nickel-cobalt-manganese composite hydroxide powder was fired at 400 ° C. in the atmosphere for 10 hours to obtain nickel-
Cobalt-manganese composite oxide (Ni / Co / Mn atomic ratio 1/1/1)
Got 2θ = 36 of powder X-ray diffraction using Cu-Kα ray.
The full width at half maximum of the diffraction angle at 4 ° was 1.45 °, it had an oxide structure belonging to the cubic system, and diffraction derived from nickel, cobalt or manganese hydroxide was not observed. The specific surface area of this composite oxide powder measured by the nitrogen adsorption method was 55.4 m ² / g. The particle size distribution of this composite oxide was measured by a laser scattering method. As a result, the volume average particle diameter D
50 was 9.6 μm.

About 5 g of this complex oxide powder was added to 3.14c.
The press density was measured from the volume and the weight by applying a pressure of 6 T per m ² , and the result was 2.46 g / cm ³ . In the SEM observation of the composite oxide powder particles, primary particles were aggregated innumerably to form secondary particles, and the shape thereof was spherical or ellipsoidal.

Lithium carbonate powder having an average particle size of 20 μm was mixed with this composite oxide powder, and the mixture was fired at 950 ° C. for 16 hours in the air and mixed and pulverized to obtain LiNi _1/3 Co _1/3 Mn _1/3. O ₂
A powder was obtained. About 5 g of this positive electrode powder is 6T per 3.14 cm ^2.
As a result of measuring the press density from the volume and the weight by applying the pressure of, the result was 3.05 g / cm ³ . The specific surface area of this positive electrode powder measured by the nitrogen adsorption method is 0.44 m ² / g,
Volume average particle diameter D50 is 9.0 μm. Powder X using Cu-Kα rays
The line diffraction spectrum is similar to the rhombohedral system (R-3m), 2θ
The full width at half maximum of the diffraction peak of the (110) plane at = 65 ° is 0.253.
It was °. These positive electrode powder particles were observed by SEM.
The primary particles were innumerable aggregates to form secondary particles, and the shape was spherical or elliptical. This positive electrode powder, acetylene black, and polytetrafluoroethylene powder were mixed at a weight ratio of 80/16/4,
The mixture was kneaded while adding toluene and dried to prepare a positive electrode plate having a thickness of 150 μm.

Then, an aluminum foil having a thickness of 20 μm was used as a positive electrode current collector, a porous polypropylene having a thickness of 25 μm was used as a separator, a lithium metal foil having a thickness of 500 μm was used as a negative electrode, and a nickel foil was used as a negative electrode current collector. 20 μm is used and the electrolyte is 1M LiPF ₆ / EC + DEC
Using (1: 1), a stainless steel simple sealed lithium battery cell was assembled in an argon glove box. Regarding this battery, first, at 25 ° C., per 1 g of positive electrode active material
It was charged with CC-CV up to 4.3 V at a load current of 20 mA, and discharged up to 2.5 V at a load current of 20 mA per 1 g of the positive electrode active material to obtain the initial discharge capacity. Further, the charge / discharge cycle test was performed 30 times. The initial discharge capacity at 2.5 to 4.3 V at 25 ° C. was 159 mAh / g, the initial charge / discharge efficiency was 90%, and the capacity retention rate after 30 charge / discharge cycles was
It was 97.6%.

Example 2 Nickel-cobalt-manganese composite oxide (Ni / Co / Mn atomic ratio 1/1/1 /) was prepared in the same manner as in Example 1 except that the nickel-cobalt-manganese composite hydroxide was calcined at 500 ° C. 1) got. The half width of the diffraction angle at 2θ = 36.2 ° of the powder X-ray diffraction using Cu-Kα line of this nickel-cobalt composite oxide powder was 1.25 °, and it had an oxide structure belonging to the cubic system. No diffraction derived from nickel, cobalt or manganese hydroxide was observed. The specific surface area of this composite oxide powder measured by the nitrogen adsorption method was 38.5 m ² / g. The particle size distribution of this composite oxide was measured by a laser scattering method. As a result, the volume average particle diameter D50 was 8.1 μm.

About 5 g of this complex oxide powder was added to 3.14c.
The press density was measured from the volume and the weight by applying a pressure of 6 T per m ² , and it was 2.51 g / cm ³ . In the SEM observation of the composite oxide powder particles, primary particles were aggregated innumerably to form secondary particles, and the shape thereof was spherical or ellipsoidal.

Lithium carbonate powder was added to this composite oxide powder.
Mix and mix as in Example 1 for LiNi _1/3Co_1/3Mn_1/3O₂powder
I got the end. As a result of measuring the press density of the positive electrode powder, 3.09
g / cm³Met. In addition, in the nitrogen adsorption method of this positive electrode powder
The specific surface area is 0.40m²/ g, and the volume average particle diameter D50 is
It was 9.1 μm. Also, powder X-ray radiation using Cu-Kα radiation
The fold spectrum is similar to the rhombohedral system (R-3m), (110)
The full width at half maximum of the diffraction peak on the surface was 0.233 °. This positive electrode
Using powder, in the same manner as in Example 1
A closed cell was assembled and the charge / discharge performance was evaluated. As a result, 25
The initial discharge capacity at ℃ was 160mAh / g.
The charge / discharge efficiency was 91.0%. In addition, 30 times charge / discharge cycle
The capacity retention rate after the test was 97.3%.

Example 3 Using the composite oxide powder synthesized in Example 1, lithium hydroxide powder was used in place of lithium carbonate, and the mixture was baked in air at 490 ° C. for 10 hours. After mixing again, the air was mixed. 15 at 950 ℃
It was calcined for an hour to obtain LiNi _1/3 Co _1/3 Mn _1/3 O ₂ powder. As a result of measuring the press density of the positive electrode powder, it was 3.02 g / cm ³ . The specific surface area of this positive electrode powder measured by the nitrogen adsorption method is
It was 0.48 m ² / g, and the volume average particle diameter D50 was 9.0 μm. The powder X-ray diffraction spectrum using Cu-Kα ray was similar to the rhombohedral system (R-3m), and the half value width of the diffraction peak of the (110) plane was 0.275 °.

Using this positive electrode powder, a stainless steel simple closed cell was assembled in the same manner as in Example 1 and the charge / discharge performance was evaluated. As a result, the initial discharge capacity at 25 ° C was 159 m.
It was Ah / g, and the initial charge / discharge efficiency was 89%. The capacity retention rate after 30 charge / discharge cycles was 96.8%.

Example 4 Contains nickel sulphate, cobalt sulphate and manganese sulphate
Same as Example 1 except that the composition ratio of the sulfate aqueous solution was changed.
Nickel-cobalt-manganese manganese composite oxide (Ni
/ Co / Mn atomic ratio 0.50 / 0.30 / 0.20) was obtained. This nickel-
Cu-Kα ray of cobalt-manganese-manganese composite oxide powder
Of powder X-ray diffraction at 2θ = 36.3 °
The full width at half maximum of the angle is 1.95 ° and the oxide structure belonging to the cubic system
Structure is the main component, nickel or cobalt or
No diffraction derived from manganese hydroxide was observed. Well
Also, the specific surface area of this composite oxide powder by the nitrogen adsorption method is
84.3m ²It was / g.

About 5 g of this complex oxide powder was added to 3.14c.
The press density was measured from the volume and the weight by applying a pressure of 6 T per m ² , and it was 2.41 g / cm ³ . In the SEM observation of the composite oxide powder particles, primary particles were aggregated innumerably to form secondary particles, and the shape thereof was spherical or ellipsoidal.

Lithium hydroxide monohydrate was mixed with this composite oxide powder, and LiNi _0.50 Co _0.30 Mn was prepared in the same manner as in Example 1.
_0.20 O ₂ powder was obtained. The powder X-ray diffraction spectrum of this positive electrode powder using Cu-Kα ray was similar to the rhombohedral system (R-3m). Using this positive electrode powder, a simple stainless steel closed cell was assembled in the same manner as in Example 1 and the charge / discharge performance was evaluated. As a result, the initial discharge capacity at 25 ° C was 169 mAh / g.
The capacity retention rate after 30 charge / discharge cycles was 96.2%.

Example 5 Nickel-cobalt-manganese-manganese-manganese composite oxide (Ni / C) was used in the same manner as in Example 1 except that the composition ratio of the sulfate aqueous solution containing nickel sulfate, cobalt sulfate and manganese sulfate was changed.
O / Mn atomic ratio 0.20 / 0.30 / 0.50) was obtained. The powder X-ray diffraction of this nickel-cobalt-manganese-manganese-manganese composite oxide powder using Cu-Kα rays has a half width of the diffraction angle at 2θ = 36.5 ° of 1.18 °, which is an oxide structure belonging to the cubic system. , And no diffraction derived from nickel, cobalt, or manganese hydroxide was observed. The specific surface area of this composite oxide powder measured by the nitrogen adsorption method is 39.3 m.
It was ² / g.

About 5 g of this complex oxide powder was added to 3.14c.
The press density was measured from the volume and the weight by applying a pressure of 6 T per m ² , and the result was 2.49 g / cm ³ . In the SEM observation of the composite oxide powder particles, primary particles were aggregated innumerably to form secondary particles, and the shape thereof was spherical or ellipsoidal.

Lithium carbonate powder was added to this composite oxide powder.
Mix and mix as in Example 1 for LiNi _0.20Co_0.30Mn_0.50O₂
A powder was obtained. Powder X using Cu-Kα rays of this positive electrode powder
The line diffraction spectrum was similar to the rhombohedral system (R-3m). This
Made of stainless steel using the same positive electrode powder as in Example 1.
A simple closed cell was assembled and the charge / discharge performance was evaluated. That conclusion
As a result, the initial discharge capacity at 25 ° C was 115 mAh / g.
The capacity retention rate after 30 charge / discharge cycles was 98.5%.
It was

Example 6 Nickel-cobalt-manganese-manganese composite oxide (Ni / C) was used in the same manner as in Example 1 except that the composition ratio of the aqueous sulfate solution containing nickel sulfate, cobalt sulfate and manganese sulfate was changed.
O / Mn atomic ratio 0.38 / 0.24 / 0.38) was obtained. The half-width of the diffraction angle at 2θ = 36.4 ° of the powder X-ray diffraction using Cu-Kα ray of this nickel-cobalt-manganese manganese composite oxide powder is 1.01 °, and the oxide structure belongs to the cubic system. , And no diffraction derived from nickel, cobalt, or manganese hydroxide was observed. Also, the specific surface area of this complex oxide powder by the nitrogen adsorption method is 45.5 m.
It was ² / g.

About 5 g of this complex oxide powder was added to 3.14c.
m²From the volume and weight by applying a pressure of 6T per
As a result of measuring the press density, 2.47 g / cm³Met. This
The composite oxide powder particles of are the primary particles in SEM observation.
Are innumerably aggregated to form secondary particles, and
The shape was spherical or elliptical. This complex oxidation
Lithium carbonate powder was mixed with the product powder and the same as in Example 1.
Then LiNi_0.38Co_0.24Mn _0.38O₂A powder was obtained. This positive electrode powder
Powder X-ray diffraction spectrum using Cu-Kα line of is rhombohedral
The system (R-3m) was similar.

Using this positive electrode powder, a simple stainless closed cell made of stainless steel was assembled in the same manner as in Example 1 and the charge / discharge performance was evaluated. As a result, the initial discharge capacity at 25 ° C was 158 m.
Ah / g, and the capacity retention rate after 30 charge / discharge cycles
It was 96.1%.

Example 7 (Ni / Co / Mn atomic ratio 1/1/1), which is the nickel-cobalt-manganese composite oxide synthesized in Example 1, was used. Lithium fluoride powder was mixed, and Li _1.05 Ni _1/3 Co _1/3 Mn _1/3 was prepared in the same manner as in Example 1.
O _1.98 F _0.02 powder was obtained. The powder X-ray diffraction spectrum using the Cu-Kα ray of the positive electrode powder was similar to the rhombohedral system (R-3m). Using this positive electrode powder, a simple stainless steel closed cell was assembled in the same manner as in Example 1 and the charge / discharge performance was evaluated. Two
The initial discharge capacity at 5 ° C was 156 mAh / g, 30
The capacity retention rate after 9 charge-discharge cycles was 98.0%.

Example 8 A nickel-manganese composite oxide (Ni / Mn atomic ratio 1/1) was synthesized in the same manner as in Example 1 without adding cobalt sulfate. 2θ = 36. Of powder X-ray diffraction using Cu-Kα line of this nickel-manganese composite oxide powder.
The full width at half maximum of the diffraction angle at 6 ° was 0.92 °, it had an oxide structure belonging to the cubic system, and diffraction derived from nickel or manganese hydroxide was not observed.

The specific surface area of this composite oxide powder measured by the nitrogen adsorption method was 47.3 m ² / g. In addition, about 5 g of this complex oxide powder was subjected to a pressure of 6 T per 3.14 cm ² , and the press density was measured from the volume and weight.
It was 45 g / cm ³ . The composite oxide powder particles are SEM
In the observation, the primary particles were aggregated innumerably to form secondary particles, and the shape was spherical or elliptic spherical.

Lithium hydroxide monohydrate was mixed with this composite oxide powder, and LiNi _0.5 Mn _0.5 O ₂ powder was obtained in the same manner as in Example 1. As a result of measuring the press density of the positive electrode powder, it was 2.97 g / cm ³ . The specific surface area of this positive electrode powder measured by the nitrogen adsorption method was 0.83 m ² / g, and the volume average particle diameter D50 was 10.5 μm. The powder X-ray diffraction spectrum using Cu-Kα rays was similar to the rhombohedral system (R-3m), and the full width at half maximum of the diffraction peak on the (110) plane was 0.171 °. Using this positive electrode powder, a simple stainless steel closed cell was assembled in the same manner as in Example 1 and the charge / discharge performance was evaluated. The initial discharge capacity at 25 ° C. was 145 mAh / g, and the initial charge / discharge efficiency was 84.2%. The capacity retention rate after 30 charge / discharge cycles was 92.6%.

Comparative Example 1 A nickel-cobalt-manganese composite hydroxide was prepared in the same manner as in Example 1 except that the nickel-cobalt-manganese composite hydroxide was not fired. (Ni / Co / Mn atomic ratio 1 / 1/1) was obtained. 2θ = 19.2 for powder X-ray diffraction using Cu-Kα line of this nickel-cobalt-manganese composite hydroxide powder
Diffraction peaks were observed at °, 35.1 °, and 37.6 °, confirming that the structure is similar to that of nickel hydroxide structure. No diffraction derived from nickel, cobalt or manganese oxide was observed.

Lithium hydroxide 1 was added to this composite hydroxide powder.
The hydrates were mixed and LiNi _1/3 Co _1/3 Mn was added as in Example 3.
_1/3 O ₂ powder was obtained. As a result of measuring the press density of this positive electrode powder, it was 2.91 g / cm ³ . The powder X-ray diffraction spectrum using Cu-Kα ray was similar to the rhombohedral system (R-3m). Using this positive electrode powder, a simple stainless steel closed cell was assembled in the same manner as in Example 1 and the charge / discharge performance was evaluated. As a result, the initial discharge capacity at 25 ° C was 153 mAh / g.
The initial charge / discharge efficiency was 87%. The capacity retention rate after 30 charge / discharge cycles was 93.2%.

[0060]

According to the present invention, there is provided a novel method for producing a positive electrode active material for a lithium secondary battery having the following characteristics. 1. High initial discharge capacity per unit weight. 2. High initial charge / discharge efficiency. 3. High initial discharge capacity per unit volume (which is proportional to the press density of the positive electrode powder). 4. High charge / discharge cycle stability. 5. High safety.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Atsushi Ito             3-10 Chigasaki, Chigasaki City, Kanagawa Prefecture             Seimi Chemical Co., Ltd. F-term (reference) 4G048 AA04 AB06 AC06 AD04 AE05                 5H029 AJ03 AJ05 AJ12 AK03 AL01                       AL02 AL06 AL07 AL12 AM03                       AM05 AM07 CJ02 CJ08 CJ28                       DJ16 EJ04 EJ12 HJ02 HJ05                       HJ07 HJ08 HJ13 HJ14                 5H050 AA07 AA08 AA15 BA16 BA17                       CA08 CA09 CB01 CB02 CB07                       CB08 CB12 EA10 EA24 GA02                       GA10 GA27 HA02 HA05 HA07                       HA08 HA13 HA14

Claims (8)

[Claims] 1. A general formula, Li _p Ni _x Co _y Mn _z O _r (however,
0.9 ≦ p ≦ 1.3, 0.2 ≦ x <0.5, 0.20 <
y <0.40, 0.2 ≦ z ≦ 0.5, 0.8 ≦ x + y +
A method of manufacturing a positive electrode active material for a lithium secondary battery, represented by the general formula Ni _x Co _y Mn _z
A mixture of a composite oxide having O _r (p, x, y, z, and r are the same as above) and having a specific surface area of 10 to 150 m ² / g and a lithium compound is mixed under an oxygen-containing atmosphere in an amount of 6
A method for producing a positive electrode active material for a lithium secondary battery, which comprises firing at 00 to 1000 ° C. 2. In the general formula of claim 1, y = 0.
And 0.9 / 1 ≦ x / z ≦ 1 / 0.9, the method for producing a positive electrode active material for a lithium secondary battery. 3. The composite oxide has a half width of a diffraction angle of 2θ = 36.5 ± 1 ° of 0.5 to 2.0 ° in powder X-ray diffraction using CuKα rays. Alternatively, the method for producing a positive electrode active material for a lithium secondary battery according to item 2. 4. The composite oxide is a calcined product of a composite hydroxide obtained by coprecipitating an aqueous mixed solution containing respective metal components contained therein with an alkali at 350 to 600 ° C. 5. The method for producing a positive electrode active material for a lithium secondary battery according to any one of 1. 5. The press density of the composite oxide is 2.3 to.
The method for producing a positive electrode active material for a lithium secondary battery according to any one of claims 1 to 4 is 3.2 g / cm ^3. 6. The positive electrode active material for a lithium secondary battery according to claim 1, wherein the composite oxide has a spherical shape or an elliptic spherical shape, and has an average particle diameter of 2 to 14 μm. Production method. 7. The lithium compound has an average particle size of 5 to 30 μm.
m is lithium carbonate, The manufacturing method of the positive electrode active material for lithium secondary batteries in any one of Claims 1-6. 8. Some of the oxygen atoms are substituted with fluorine atoms, the general _{formula, Li p Ni x Co y Mn} z O q F a (p, x, y and z are as defined above, 0 < a ≦ 0.40, 1.8 ≦
The method for producing a positive electrode active material for a lithium secondary battery according to claim 1, wherein q ≦ 2.2).