JP2002060225A - Lithium cobaltate aggregate, cobalt oxide aggregate, method for manufacturing the same and lithium cell using lithium cobaltate aggregate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a new lithium cobaltate aggregate having the performance in good balance with improved stability and safeness as a cell material without decreasing the cell characteristics, to provide a new cobalt oxide aggregate to be used for the manufacture of the above aggregate, a method for manufacturing these aggregates, and to provide a lithium cell using the lithium cobaltate aggregate as the positive pole active material. SOLUTION: The lithium cobaltate aggregate having 1 to 30 μm average particle size as the secondary particles is obtained by aggregating primary particles having 0.05 to 5 μm average particle size, and by using the aggregate as the positive pole active material of a lithium cell, the lithium cell is excellent in the cell characteristics, stability and safeness. The cobalt oxide aggregate having 0.5 to 30 μm average particle size as the secondary particles is prepared by aggregating primary particles having 0.01 to 2 μm average particle size and is useful to manufacture the above lithium cobaltate aggregate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lithium cobaltate aggregate useful for a battery material and the like, a cobalt compound aggregate used for the production thereof, a method for producing the same, and a lithium battery using the lithium cobaltate aggregate.

[0002]

2. Description of the Related Art Cobalt compounds are used for various purposes in the industrial field.
Along with the rapid expansion of small electronic devices such as mobile phones, demand for cathode materials for lithium secondary batteries and polymer secondary batteries has been growing rapidly. Lithium cobalt oxide is mainly used as a positive electrode active material of a lithium battery. Lithium cobalt oxide is usually a cobalt compound such as tricobalt tetroxide, cobalt hydroxide or cobalt carbonate, and a lithium compound such as lithium carbonate or lithium hydroxide. It is manufactured by a method of heating and firing at a high temperature after mixing with a compound.

In general, the battery characteristics such as the charge and discharge characteristics of a lithium battery are better as the particle size of lithium cobalt oxide used as a battery material is smaller, but if the particle size is smaller, the stability and safety of the battery are reduced. Therefore, lithium cobaltate that satisfies all the characteristics is required.

[0004]

SUMMARY OF THE INVENTION The present invention overcomes the problems of the prior art, and provides a novel cobalt material having a balanced performance with improved stability and safety without impairing battery characteristics as a battery material. An object of the present invention is to provide a lithium oxide aggregate, a novel cobalt oxide aggregate used for the production thereof, a method for producing the same, and a lithium battery using the above lithium cobalt oxide aggregate as a positive electrode active material.

[0005]

Means for Solving the Problems As a result of intensive studies, the present inventors have found that primary particles of lithium cobaltate having an average particle size of 0.05 to 5 μm are aggregated to form a secondary particle size of 1 to 30 μm. Assuming that the agglomerate has an average particle size of, a lithium battery using this agglomerate as a positive electrode active material was found to have excellent battery characteristics, stability, and safety. Further, the average particle diameter is 0.01 to 2 μm
The cobalt oxide aggregate having an average particle diameter of 0.5 to 30 μm as a secondary particle diameter by aggregating the primary particles of the cobalt oxide is useful for producing such a lithium cobaltate aggregate. The inventors have found that the present invention has been completed.

That is, the present invention provides an average particle size of 0.05 to
Lithium cobaltate aggregates in which 5 μm primary particles form secondary particles having an average particle diameter of 1 to 30 μm and primary particles having an average particle diameter of 0.01 to 2 μm having an average particle diameter of 0.5
The present invention relates to a cobalt oxide aggregate formed by forming secondary particles of about 30 μm, a method for producing the same, and a lithium battery using the lithium cobaltate aggregate.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Lithium cobaltate aggregate The lithium cobaltate aggregate of the present invention is a secondary particle having an average particle size of 1 to 30 μm, in which primary particles of lithium cobaltate having an average particle size of 0.05 to 5 μm are strongly aggregated. Is formed. When the primary particle diameter and the secondary particle diameter are within the above range, when this is used as an electrode material,
A lithium battery having a well-balanced performance excellent in both battery characteristics such as charge / discharge characteristics and stability and safety can be obtained.

The primary and secondary particles of the lithium cobaltate aggregate of the present invention have a more preferable average particle size range of 0.1 to 2 μm and 2 to 10 μm, respectively. Incidentally, the aggregates in the present invention, even if the usual mechanical pulverization used industrially, is not pulverized to primary particles, most remain as secondary particles, primary particles and The average particle diameter of the secondary particles is measured by an electron microscope.

The primary particles and the secondary particles of the lithium cobaltate aggregate are represented by the composition formula LixCoyO2, and the ranges of the values of x and y are respectively 0.8 ≦ x ≦
1.2, 0.8 ≦ y ≦ 1.2, and preferably in the range of 0.9 to 1.1 expressed by x / y, even if it is a single phase of lithium cobalt oxide, It may be a mixture of lithium and cobalt oxide. The shape of the primary particles is spherical and polyhedral, and is not particularly limited. However, secondary particles are advantageous in shape with as small anisotropy as possible in terms of battery characteristics, and agglomerates and spheres are most desirable.

[0010] An aggregate of lithium cobalt oxide can be obtained by mixing a cobalt oxide and a lithium compound, heating and sintering the mixture, but it is difficult to control the primary particle diameter and the secondary particle diameter. A fine particle shape cannot be obtained. In the present invention, for example, a cobalt oxide and a lithium compound having a primary particle diameter within the above range are mixed, and then subjected to agglomeration treatment, followed by heating and firing, or such a cobalt oxide is subjected to an agglomeration treatment to obtain cobalt. After being made into an oxide aggregate, it can be manufactured by mixing this with a lithium compound and heating and firing.

The heating and sintering temperature is preferably not lower than the temperature at which the phase changes to lithium cobalt oxide, and the temperature should be as low as possible so as to prevent sintering of the formed aggregates. Preferably 70
0-900 ° C. The obtained lithium cobaltate aggregate is pulverized using various mills such as a sample mill, a grinding type such as a raikai machine, an impact type such as a hammer mill, and an air flow type such as a jet mill, as necessary. Is also good.

The cobalt oxide referred to in the present invention includes cobalt oxides such as cobalt monoxide, dicobalt trioxide, cobalt dioxide and tricobalt tetroxide, hydrates of cobalt oxides, and cobaltous hydroxide. Of cobalt, cobalt oxyhydroxide, or a mixture of two or more thereof. As the cobalt oxide used in the present invention, tricobalt tetroxide is particularly preferred. As the lithium compound, lithium hydroxide, lithium carbonate, lithium nitrate, or the like can be used.

The cobalt oxide can be obtained by various methods. In the present invention, it is preferable to use one having a uniform particle size distribution. It is obtained by reacting with an alkaline compound, and tricobalt tetroxide, cobalt oxyhydroxide and the like can be obtained by heating and drying or heating and firing the above-mentioned cobalt hydroxide.
Alternatively, while reacting the divalent cobalt compound and the alkaline compound in a medium such as water, an oxidizing agent is added to the medium and oxidized, or after the reaction in the medium, the oxidizing agent is added. It can also be obtained by oxidation.

As a method of coagulating a mixture of a cobalt oxide and a lithium compound, for example, there is a method of spray-drying a slurry containing a cobalt oxide. In this method, first, a slurry containing a cobalt oxide and a lithium compound is prepared, and the slurry is granulated and dried using a spray dryer of a disk type, a pressure nozzle type, a two-fluid nozzle type, or the like. The spray dryer can be appropriately selected according to the properties and processing capacity of the slurry. The control of the secondary particle diameter is performed, for example, by adjusting the number of rotations of the disk in the case of the above-described disk type, or by adjusting the spray pressure or the nozzle diameter in the case of the pressure nozzle type or the two-fluid nozzle type, to thereby adjust the size of the sprayed droplet. It can be done by controlling.

When the viscosity of the slurry is low and granulation is difficult,
To make it easier to control the particle size, various additives such as a binder such as PVA (polyvinyl alcohol) and a surfactant may be used. It is desirable that these additives are organic substances, do not contain a metal component, and decompose and volatilize during spray drying. The drying temperature is preferably about 250 ° C. at the inlet and about 120 ° C. at the outlet.

2. Cobalt oxide aggregate The lithium cobaltate aggregate of the present invention is obtained by heating and calcining the cobalt oxide aggregate and the lithium compound as described above.
It is preferable to use one in which primary particles of cobalt oxide having an average particle diameter of 0.01 to 2 μm are strongly aggregated to form secondary particles having an average particle diameter of 0.5 to 30 μm. Such cobalt oxide aggregates are novel and not only as intermediates for battery materials, but also for electronic materials, catalysts,
It is also useful as a pigment.

The average particle diameter of the primary particles and the secondary particles of the cobalt oxide aggregate of the present invention is 0.02
It is more preferable that they are in the range of 1 to 1 μm and 1 to 20 μm, and particularly that of tricobalt tetroxide for the electrode material is in the range of 0.03 to 0.2 μm and 1 to 10 μm, respectively. The shape of the primary particles includes various shapes such as a sphere, a particle, and a plate, and the shape is not particularly limited. The shape of the secondary particles is also not particularly limited, such as spherical, agglomerate, egg-shaped, polyhedral, and scale-like, and may be partially missing, but a spherical shape is most desirable for batteries.

In the present invention, the primary particles and the secondary particles of the cobalt oxide aggregate are represented by the composition formula CoxOyHz (1 ≦ x
≦ 3, 1 ≦ y ≦ 4, 0 ≦ z ≦ 2), a cobalt oxide, dicobalt trioxide, cobalt dioxide, tricobalt tetroxide and a hydrate of cobalt oxide; Hydroxides of cobalt, such as cobaltous hydroxide;
It means cobalt oxyhydroxide or a mixture of two or more of these. Tricobalt tetroxide is preferable as a raw material of lithium cobalt oxide as a battery material. If tricobalt tetroxide is particularly fine spherical particles, a spherical aggregate having a dense structure is formed by aggregating the particles. Since it is easy, it becomes suitable as a battery material.

The cobalt oxide aggregate of the present invention can be obtained by subjecting a cobalt oxide to an aggregation treatment. The coagulation treatment may be performed by heating and sintering the cobalt compound,
Since it is easy to control the particle size and particle shape of the secondary particles,
For example, (a) a method of spray-drying a slurry containing a cobalt oxide, and (b) a method of aggregating the cobalt oxide by growing particles in a medium such as water are preferable. The method (a) can be produced in the same manner as in the above-mentioned lithium cobaltate aggregate.

In the method (b), the system is oxidized by reacting a divalent cobalt compound with an alkaline compound in a medium such as water in the presence of a cobalt compound in an oxidizing atmosphere to react the divalent cobalt compound with an alkaline compound. In the process of growing the particles, the grown particles aggregate, and the cobalt oxide aggregate of the present invention is synthesized. Even if particles are grown in a non-oxidizing atmosphere in the system, they are generated separately from the cobalt oxide that is initially present, so they do not become agglomerates, just cobalt hydroxide grows in hexagonal plate shape. Aggregates as in the present invention cannot be obtained.

To make the inside of the system an oxidizing atmosphere, an oxidizing agent is added to the medium. As the oxidizing agent, an oxidizing gas such as air, oxygen, and ozone, or an oxidizing compound such as aqueous hydrogen peroxide can be used. However, a method of blowing an oxidizing gas such as air is preferable from the viewpoint of ease of handling and economy. The average particle size of the aggregate of the present invention can be controlled by adjusting the reaction amount between the divalent cobalt compound and the alkali compound.

The reaction temperature during grain growth is 50-100 ° C.
Further, the pH is desirably 5 or more. If the temperature and the pH are out of these ranges, the aggregates having a uniform particle size are not obtained, and the reaction takes a long time. A more preferred temperature range is 70-100 ° C, and a more preferred pH range is 7-14, and even more preferably 9-13.

The average particle diameter as the primary particle diameter is 0.01
２2 μm cobalt oxide can be obtained by various methods. For example, in the case of cobalt hydroxide, when reacting a divalent cobalt compound and an alkaline compound in a medium such as water, the particle size can be controlled to a desired size by adjusting the addition amount of both. . The order of addition of the divalent cobalt compound and the alkaline compound to the medium can be appropriately selected and is not particularly limited. For example, both may be added simultaneously.

Cobalt oxides, cobalt oxyhydroxides and the like can be obtained by heating and drying or calcining the cobalt hydroxide obtained by the above method at 50 to 900 ° C. in the air. . By adjusting the heating temperature and the heating time, a cobalt oxide having a desired composition, such as a single substance, a mixture, or a substance in which a part of the hydroxide remains, can be obtained. Tricobalt tetroxide can be obtained by heating and firing cobalt hydroxide at 150 to 900 ° C. This heat calcination may be performed after the cobalt hydroxide is formed into an aggregate.

In the present invention, fine particles of cobalt oxide are used.
It is more preferable to use tricobalt tetroxide as a spherical particle having an average primary particle diameter of 0.03 to 0.2 μm. Such cobalt trioxide can be oxidized by (1) adding an oxidizing agent while reacting a divalent cobalt compound and an alkaline compound in a medium such as water, or (2) adding a divalent cobalt compound to an alkaline compound. It is obtained by reacting a compound with a medium such as water to obtain cobalt hydroxide, and then adding an oxidizing agent to oxidize the compound.

Examples of the divalent cobalt compound used in the present invention include cobalt sulfate, cobalt chloride, and cobalt nitrate. Alkaline compounds such as alkali metal carbonates and hydroxides such as sodium hydroxide and potassium hydroxide, Ammonia gas, aqueous ammonia, and ammonium such as ammonium carbonate can be used.

3. Lithium Battery Next, the present invention is a lithium battery using the above-described lithium cobaltate aggregate as an electrode active material. In general, battery characteristics such as electromotive force and charge / discharge characteristics are said to be better as the particle size of lithium cobalt oxide as the positive electrode active material is smaller, and stability and safety are better as the particle size of lithium cobalt oxide is larger. Have been done. Therefore, it has been difficult for the conventional lithium battery to satisfy both.

However, in the present invention, by using the above-described lithium cobaltate aggregate, a lithium battery having balanced performance was obtained. A lithium battery as referred to in the present invention is a primary battery using lithium metal for the negative electrode, and a rechargeable secondary battery using lithium metal for the negative electrode, a carbon material for the negative electrode, capable of charging and discharging using a tin compound and the like. Refers to a lithium ion secondary battery.

When the positive electrode for a lithium battery is used for a coin-type battery, the lithium cobaltate aggregate of the present invention may be
A carbon-based conductive agent such as acetylene black, carbon, or graphite powder, or a binder such as polytetrafluoroethylene resin or polyvinylidene fluoride is added, kneaded, and formed into a pellet shape. Furthermore, in the case of a cylindrical or prismatic battery, an organic solvent such as N-methylpyrrolidone is also added to the lithium cobaltate aggregate of the present invention, in addition to these additives, and the mixture is kneaded to form a paste. It can be obtained by coating on a metal current collector such as a foil and drying.

In a lithium battery electrolyte, lithium ions are dissolved in a polar organic solvent which is electrochemically stable, that is, is not oxidized or reduced in a wider range than a potential range in which the lithium ion battery operates. Can be used. As the polar organic solvent, propylene carbonate, ethylene carbonate, diethyl carbonate, dimethoxyethane, tetrahydrofuran, γ-
Butyl lactone or a mixture thereof can be used. As a solute serving as a lithium ion source, lithium perchlorate, lithium hexafluorophosphate, lithium tetrafluoroborate, or the like can be used. A porous polypropylene film or polyethylene film is disposed between the electrodes as a separator.

As for the type of battery, a separator is placed between a positive electrode and a negative electrode in the form of a pellet, pressed into a sealing can with a gasket made of polypropylene, injected with an electrolytic solution, and sealed. Materials include a cylindrical type in which a material or a negative electrode material is applied onto a metal current collector, wound up with a separator interposed therebetween, inserted into a battery can with a gasket, injected with an electrolyte, and sealed. There is also a three-electrode type battery particularly for measuring electrochemical properties.
This battery also has a reference electrode besides the positive and negative electrodes, and by controlling the potential of the other electrodes with respect to the reference electrode,
The purpose is to evaluate the electrochemical characteristics of each electrode.

The performance of the lithium cobaltate aggregate as a positive electrode active material is determined by forming a secondary battery using a lithium metal or the like for the negative electrode and charging / discharging the battery in an appropriate potential range at a constant current. The capacity can be measured.
In addition, the quality of the cycle characteristics can be determined from the change in the electric capacity due to the repeated charge and discharge.

[0033]

EXAMPLES Examples of the present invention will be shown below, but the present invention is not limited to these examples.

(Production of Cobalt Oxide Aggregate) Example 1 1. Synthesis of Cobalt Oxide 20 (l) of an aqueous solution of cobalt sulfate having a divalent cobalt ion concentration of 60 (g / l) was heated to a temperature of 30 ° C, and while blowing nitrogen gas, 100 (g / l) sodium hydroxide was added. Aqueous solution 16.3 (l) was added for 2 hours and then aged for 2 hours to obtain hexagonal plate-like cobalt hydroxide (sample a).
I got

2. Coagulation treatment of cobalt oxide After filtering and washing cobalt hydroxide, it was dispersed in a slurry of 100 (g / l), and the inlet temperature was 230 ° C and the outlet temperature was 120 ° C using a disk rotary spray drier (manufactured by Niro). Was subjected to spray drying to obtain an aggregate (sample A) of the present invention.

Embodiment 2 1. Synthesis of Cobalt Oxide The slurry containing cobalt hydroxide (sample a) synthesized in the first step of Example 1 was heated to 70 ° C., and while adjusting the pH to 12, air was added to the slurry. 15 (l /
), Thereby obtaining spherical tricobalt tetroxide (sample b).

2. Coagulation treatment of cobalt oxide In the same manner as in the second step of Example 1, tricobalt tetroxide was spray-dried to obtain an aggregate (sample B) of the present invention.

Example 3 Sample B obtained in Example 2 was heated and baked at 800 ° C. for 2 hours to obtain an aggregate (Sample C) of the present invention. By heating and sintering, the primary particle diameters aggregated and grew to increase, but the secondary particle diameter was hardly changed.

Embodiment 4 1. Synthesis of Cobalt Oxide A 2 (l) aqueous solution of cobalt sulfate having a divalent cobalt ion concentration of 60 (g / l) was heated to 60 ° C, and air was heated at 2 (l / min).
1.63 (l) of a 100 (g / l) aqueous solution of sodium hydroxide was added over 2 hours while blowing at a flow rate of 2, followed by aging for 18 hours by blowing in air to obtain cobalt hydroxide, cobalt oxyhydroxide and tetrahydrofuran. A mixture of tricobalt oxide (sample d) was obtained.

2. Coagulation Treatment of Cobalt Oxide A mixture of cobalt hydroxide, cobalt oxyhydroxide and tricobalt tetroxide was filtered, washed, and dispersed in a 100 (g / l) slurry containing 1.5% PVA. Spray drying was performed under the same conditions as in the second step to obtain an aggregate (sample D) of the present invention.

Embodiment 5 1. Synthesis of cobalt oxide 5% ammonia water 7 (l) was heated to 40 ° C., and a divalent cobalt ion concentration of 60 (g /
l) of cobalt sulfate aqueous solution 10 (l) and 400 (g /
l) of sodium hydroxide aqueous solution 2 (l) was added simultaneously over 6 hours, aged for 3 days, filtered, washed,
Dry at 20 ° C. for 24 hours. Then, in air 800
Baked at 2 ° C for 2 hours, granular tricobalt tetroxide (sample e)
I got

2. Coagulation treatment of cobalt oxide After filtering and washing tricobalt tetroxide, it was dispersed in a 100 (g / l) slurry containing 0.2% of an ether-based surfactant (Peknol ST-7: manufactured by Toho Chemical). Example 1
Spray-drying was performed under the same conditions as in the second step to obtain an aggregate (sample E) of the present invention.

Embodiment 6 1. Synthesis of cobalt oxide Tricobalt tetroxide was obtained in the same manner as in the first step of Example 2.

2. Coagulation treatment of cobalt oxide A slurry containing 100 g of tricobalt tetroxide and 12 (l) of a cobalt sulfate aqueous solution having a divalent cobalt ion concentration of 60 (g / l) was heated to 70 ° C, and air was discharged at 5 (l / min). ), 2.45 (l) of a 400 (g / l) aqueous sodium hydroxide solution is added over 60 hours while adjusting the pH to 10.0, and tricobalt tetroxide is added to the particles. The aggregate of the present invention (sample F) was obtained by aggregation while growing.

Embodiment 7 1. Synthesis of Cobalt Oxide The cobalt hydroxide obtained by the same method as in the first step of Example 1 was filtered, washed, and dried at 150 ° C. to obtain about 70% of cobalt oxyhydroxide and about A 30% mixture (sample g) was obtained.

2. Coagulation treatment of cobalt oxide The slurry containing 100 g of the mixture was heated to 70 ° C.
While blowing air at a flow rate of 5 (l / min), an aqueous solution of cobalt sulfate having a divalent cobalt ion concentration of 60 (g / l) 1
0.3 (l) and 2.1 (l) of a 400 (g / l) aqueous sodium hydroxide solution were added simultaneously over a period of 56 hours while adjusting the pH to 10.0, and the mixture was subjected to particle growth. Agglomeration was carried out to obtain an aggregate (sample G) of the present invention. The agglomerates were a mixture of about 4% cobalt oxyhydroxide and about 96% tricobalt tetroxide.

Example 8 Sample F obtained in Example 7 was filtered, washed, and calcined by heating at 800 ° C. for 2 hours in the air to obtain tricobalt tetroxide (Sample H) of the present invention.

Example 9 Example 7 was repeated except that tricobalt tetroxide (sample e) obtained in the first step of Example 5 was used instead of the mixture of cobalt oxyhydroxide and tricobalt tetroxide. In the same manner as in the second step, an aggregate of tricobalt tetroxide of the present invention (sample I) was obtained.

Comparative Examples 1 to 5 Cobalt compounds (samples a, b, d, e, and g) obtained in the first step of Examples 1, 2, 4, 5, and 7 before the agglomeration treatment were each used as a comparative example. 1 to 5.

Comparative Example 6 Cobalt hydroxide obtained in the first step of Example 1 (sample a)
If the slurry containing 100 g is heated to 70 ° C. and nitrogen gas is blown, the divalent cobalt ion concentration is 60 (g / l).
8.6 (l) and 400 (g / l) of aqueous cobalt sulfate solution
1.75 (l) of an aqueous sodium hydroxide solution having a concentration of
Sample J was obtained by adding the particles over time and allowing the particles to grow. Sample J
Are large plate-like particles of cobalt hydroxide, and the aggregate of the present invention was not obtained.

Comparative Example 7 The same treatment as in Comparative Example 6 was carried out in the presence of 100 g of tricobalt tetroxide (Sample b) obtained in Example 2 to obtain Sample K.
Sample K was a mixture of a spherical tricobalt tetroxide and a separately formed plate-like cobalt hydroxide, and the aggregate of the present invention was not obtained.

Comparative Example 8 The same treatment as in Comparative Example 6 was performed in the presence of 100 g of tricobalt tetroxide (sample e) obtained in Example 5 to obtain Sample L.
Sample L was a mixture of granular tricobalt tetroxide and a separately formed plate-like cobalt hydroxide, and the aggregate of the present invention was not obtained.

Evaluation 1 Cobalt oxide aggregates obtained in Examples 1 to 9 (sample A
To I) and the average particle diameter of the cobalt oxides (samples a, b, d, e, g and J to L) obtained in Comparative Examples 1 to 5 were measured by the following methods. The results are shown in Tables 1 and 2.

(Measurement Method of Average Particle Size) First, 5 g of a sample of primary particles before the aggregation treatment or secondary particles after the treatment was ground in an automatic mortar (manufactured by Ishikawa) for 10 minutes. Shoot. The particle diameter is measured from the photograph using a particle analyzer (manufactured by Carl Zeiss), and the calculated weight average diameter is defined as the average particle diameter.

[0055]

[Table 1]

[0056]

[Table 2]

The cobalt oxide aggregates (samples B, C, and F) obtained in Examples 2, 3, and 6, and Comparative Examples 1, 2,
Cobalt oxides obtained in 6, 7 (samples a, b, J,
The electron micrograph of K) is shown in FIGS. It has been found that the present invention is an aggregate formed by aggregating small particles.

(Production of Aggregate of Lithium Cobaltate) Example 10 1. Aggregation treatment of mixture of cobalt oxide and lithium compound The cobalt hydroxide (sample a) in Example 1 was filtered, washed, and reslurried, and then the lithium hydroxide was converted to Co / L.
i ratio = 1/1 (molar ratio).
It was adjusted to 00 (g / l). Using a disk type spray drier (manufactured by Niro Corporation), this slurry was heated at an inlet temperature of 230 ° C.
Spray drying was performed at an outlet temperature of 120 ° C. to obtain a scale-like aggregate.

2. Heat Firing The above aggregate was heated and fired in air at 850 ° C. for 10 hours to obtain a lithium cobaltate aggregate (Sample M) of the present invention.

Embodiment 11 1. Aggregation treatment of mixture of cobalt oxide and lithium compound Tricobalt tetroxide (sample b) in Example 2 was filtered,
After washing and reslurrying, the lithium carbonate was removed using Co / L
i ratio = 1/1 (molar ratio).
It was adjusted to 00 (g / l). This slurry was used in Example 1
Spray drying was performed in the same manner as described above to obtain a spherical aggregate.

[0061] 2. Heat calcination The aggregate was heated and baked in air at 800 ° C. for 10 hours to obtain a lithium cobaltate aggregate (Sample N) of the present invention.

Embodiment 12 1. Aggregation treatment of cobalt oxide An aggregate of tricobalt tetroxide was obtained in the same manner as in Example 2.

2. Heat calcination The aggregate and lithium carbonate were mixed at a Co / Li ratio of 1/1.
(Molar ratio), and heated and fired in the same manner as in Example 10 to obtain a lithium cobaltate aggregate (Sample O) of the present invention.

Embodiment 13 1. Aggregation treatment of mixture of cobalt oxide and lithium compound A mixture (sample d) of cobalt hydroxide, cobalt oxyhydroxide and tricobalt tetroxide in Example 1 was filtered, washed, reslurried, and then lithium hydroxide. To Co / L
i ratio = 1/1 (molar ratio)
The concentration containing 1.5% was adjusted to 100 (g / l). This slurry was spray-dried in the same manner as in Example 1,
A spherical aggregate was obtained.

2. Heating and Firing The above aggregate was heated and fired in the same manner as in Example 10 to obtain a lithium cobaltate aggregate (Sample P) of the present invention.

Embodiment 14 1. Aggregation treatment of mixture of cobalt oxide and lithium compound Mixture of tricobalt tetroxide in Example 5 (sample e)
After filtration, washing and reslurrying, lithium hydroxide was added so that the Co / Li ratio = 1/1 (molar ratio), and an ether-based surfactant (Peknol ST-7: manufactured by Toho Chemical) The concentration containing 0.2% was adjusted to 100 (g / l). This slurry was spray-dried in the same manner as in Example 1 to obtain a spherical aggregate.

2. Heating and Firing The above aggregate was heated and fired in the same manner as in Example 10 to obtain a lithium cobaltate aggregate (Sample Q) of the present invention.

Embodiment 15 1. Aggregation treatment of cobalt oxide An aggregate of tricobalt tetroxide was obtained in the same manner as in Example 6.

2. Heat calcination The aggregate and lithium carbonate were mixed at a Co / Li ratio of 1/1.
(Molar ratio) and heated and baked in the same manner as in Example 11 to obtain a lithium cobaltate aggregate (Sample R) of the present invention.

Embodiment 16 Coagulation treatment of cobalt oxide Cobalt oxyhydroxide of about 4 was obtained in the same manner as in Example 7.
% And about 96% of tricobalt tetroxide.

2. Heat calcination The aggregate and lithium carbonate were mixed at a Co / Li ratio of 1/1.
(Molar ratio), and heated and fired in the same manner as in Example 10 to obtain a lithium cobaltate aggregate (Sample S) of the present invention.

Embodiment 17 Aggregation treatment of cobalt oxide An aggregate composed of tricobalt tetroxide was obtained in the same manner as in Example 8.

2. Heat calcination The aggregate and lithium carbonate were mixed at a Co / Li ratio of 1/1.
(Molar ratio), and heated and fired in the same manner as in Example 10 to obtain a lithium cobaltate aggregate (Sample T) of the present invention.

Comparative Example 9 The cobalt hydroxide (sample a) obtained in Example 1 was filtered, washed and dried, and then lithium carbonate was added in a Co / Li ratio of 1/1.
(Molar ratio) and calcined in air at 850 ° C. for 10 hours to obtain lithium cobalt oxide (sample U).

Comparative Example 10 A mixture (sample K) of tricobalt tetroxide and cobalt hydroxide obtained in Comparative Example 7 was filtered, washed and dried, and then lithium carbonate was subjected to Co / Li ratio = 1/1 (molar ratio). ) And baked in air at 850 ° C. for 10 hours to obtain lithium cobaltate (sample V).

Comparative Example 11 A mixture (sample d) of cobalt hydroxide, cobalt oxyhydroxide and tricobalt tetroxide obtained in Example 4 was filtered, washed and dried. 1
(Molar ratio) and calcined in air at 850 ° C. for 10 hours to obtain lithium cobalt oxide (sample W).

Evaluation 2 The average particle size of the lithium cobaltate aggregates (samples MT) obtained in Examples 10 to 17 and the lithium cobaltate aggregates (samples U to V) obtained in Comparative Examples 9 to 11 were determined. It was measured in the same manner as in Evaluation 1. Table 3 shows the results.

[0078]

[Table 3]

Evaluation 3 Samples M to M obtained in Examples 10 to 17 and Comparative Examples 9 to 11
The charge and discharge characteristics and the cycle characteristics of the lithium secondary battery when W was used as the positive electrode active material were evaluated. The battery was a three-electrode cell, and charging and discharging were repeated. The form of the battery and the measurement conditions will be described.

Each of the above samples, graphite powder as a conductive agent, and polytetrafluoroethylene resin as a binder were mixed at a weight ratio of 3: 2: 1 and kneaded in a mortar to form a circle having a diameter of 14 mm. It was molded into a pellet.
The weight of the pellet was 50 mg. This was sandwiched between metal titanium meshes and pressed at a pressure of 14.7 MPa to obtain a positive electrode.

On the other hand, metallic lithium having a thickness of 0.5 mm was formed into a circular shape having a diameter of 14 mm, sandwiched between meshes made of metallic nickel, and pressed to obtain a negative electrode. In addition, a metal lithium foil having a thickness of 0.1 mm was wound around a metal nickel wire to the extent that rice grains were large, and this was used as a reference electrode. As the non-aqueous electrolyte, a mixed solution of 1,2-dimethoxyethane and propylene carbonate in which lithium perchlorate was dissolved at a concentration of 1 mol / liter (mixed at a volume ratio of 1: 1) was used. In addition, the electrode was arrange | positioned in order of the positive electrode, the reference electrode, and the negative electrode, and the porous polypropylene film was put as a separator between them.

The measurement of the charge / discharge cycle was performed by setting the voltage range to 4.
From 3 V to 3.5 V, the charge / discharge current was 0.26 mA (about 1
(Cycles / day) at a constant current. Table 4 shows the average charge / discharge efficiency calculated from the initial discharge capacity and the discharge capacity of the 10th cycle, and the cycle characteristics of the discharge capacity calculated from the discharge capacity at the 10th cycle. Capacity is positive electrode active material 1
It is per g.

[0083]

[Table 4]

The lithium cobaltate aggregate of the present invention, when used as a positive electrode active material of a lithium battery, has a higher initial discharge capacity, an average charge / discharge efficiency, It also has excellent discharge capacity cycle characteristics.

Electron micrographs of the lithium cobaltate aggregate (sample N) obtained in Example 11 and lithium cobaltate (sample U) of Comparative Example 9 are shown in FIGS. It was found that in the present invention, small particles aggregated to form an aggregate.

[0086]

According to the present invention, the average particle size of the primary particles is 0.
And the average particle size of the secondary particles is 1 to 5 μm.
It is a lithium cobaltate aggregate having a size of 30 μm, and is most suitable as a positive electrode active material of a lithium battery. Also,
The present invention relates to a cobalt oxide aggregate having an average particle size of primary particles of 0.01 to 2 μm and an average particle size of secondary particles of 0.5 to 30 μm, and an intermediate of the lithium cobaltate aggregate. It is also useful as an electronic material, a pigment, a catalyst, and the like. The lithium battery using the lithium cobaltate aggregate of the present invention is excellent in both battery characteristics such as cycle characteristics and safety and stability.

[Brief description of the drawings]

FIG. 1 is an electron micrograph of sample B (magnification: 10,000 times).
It is.

FIG. 2 is an electron micrograph of sample C (magnification: 10,000 times).
It is.

FIG. 3 is an electron micrograph of sample F (magnification: 10,000 times).
It is.

FIG. 4 is an electron micrograph of sample a (magnification: 50,000 times).
It is.

FIG. 5 is an electron micrograph of sample b (magnification: 50,000 times).
It is.

FIG. 6 is an electron micrograph of sample J (magnification: 50,000 times).
It is.

FIG. 7 is an electron micrograph of sample K (magnification: 50,000 times).
It is.

FIG. 8 is an electron micrograph of sample N (magnification: 10,000 times).
It is.

FIG. 9 is an electron micrograph of the sample U (magnification: 10,000 times).
It is.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4G048 AA04 AB01 AC06 AD03 AE05 5H029 AJ05 AJ12 AK03 AL12 AM03 AM04 AM05 AM07 CJ02 CJ14 DJ16 HJ02 HJ05 5H050 AA07 AA15 BA17 CA08 EA11 EA12 FA17 GA02 GA06 GA15 HA02 HA05

Claims (20)

[Claims] A lithium cobaltate aggregate comprising primary particles having an average particle size of 0.05 to 5 μm forming secondary particles having an average particle size of 1 to 30 μm. 2. The lithium cobaltate aggregate according to claim 1, wherein the primary particles have an average particle size of 0.1 to 2 μm, and the secondary particles have an average particle size of 2 to 10 μm. 3. The method for producing a lithium cobaltate aggregate according to claim 1, wherein agglomeration treatment of the cobalt oxide and the lithium compound is carried out, followed by heating and firing. 4. The method for producing a lithium cobaltate aggregate according to claim 3, wherein the aggregation treatment comprises spray-drying a slurry containing a cobalt oxide and a lithium compound. 5. The lithium cobaltate coagulant according to claim 4, wherein the cobalt oxide is a reaction product of a divalent cobalt compound and an alkaline compound, or the reaction product is heated and calcined. Manufacturing method of aggregate. 6. The method according to claim 1, wherein the cobalt oxide is oxidized while reacting the divalent cobalt compound and the alkaline compound in a medium, or oxidized after reacting in a medium. Item 5. The method for producing a lithium cobaltate aggregate according to Item 4. 7. The method for producing a lithium cobaltate aggregate according to claim 1, wherein the cobalt oxide aggregate and the lithium compound are heated and calcined. 8. The method according to claim 8, wherein the cobalt oxide aggregate has an average particle size of 0.0
The lithium cobaltate aggregate according to claim 7, wherein primary particles of cobalt oxide of 1 to 2 µm are aggregated to form secondary particles having an average particle diameter of 0.5 to 30 µm. Production method. 9. A lithium battery using the lithium cobaltate aggregate according to claim 1 as a positive electrode active material. 10. A cobalt oxide aggregate comprising primary particles having an average particle size of 0.01 to 2 μm forming secondary particles having an average particle size of 0.5 to 30 μm. 11. The primary particles have an average particle size of 0.02 to 1 μm.
11. The cobalt oxide aggregate according to claim 10, wherein the average particle diameter of the secondary particles is 1 to 20 μm. 12. The method according to claim 1, wherein the primary particles have an average particle size of 0.03 to 0.1.
The cobalt oxide aggregate according to claim 10, wherein the average particle diameter of the secondary particles is 2 μm and the average particle diameter of the secondary particles is 1 to 10 μm. 13. The method according to claim 13, wherein the primary particles and the secondary particles have the composition formula CoxO.
The cobalt oxide aggregate according to claim 10, wherein the aggregate is represented by yHz (1≤x≤3, 1≤y≤4, 0≤z≤2). 14. The method according to claim 1, wherein the primary particles and the secondary particles are at least one selected from cobalt monoxide, dicobalt trioxide, tricobalt tetroxide, cobaltous hydroxide and cobalt oxyhydroxide. Item 11. The cobalt oxide aggregate according to Item 10. 15. The method according to claim 10, wherein the primary particles and the secondary particles are tricobalt tetroxide.
The cobalt oxide aggregate according to the above. 16. The method for producing a cobalt oxide aggregate according to claim 10, wherein the cobalt oxide is subjected to an aggregation treatment. 17. The method for producing a cobalt oxide aggregate according to claim 16, wherein the aggregation treatment comprises spray drying a slurry containing the cobalt oxide to aggregate the cobalt oxide. 18. The cobalt oxide according to claim 16, wherein the coagulation treatment is carried out by oxidizing the divalent cobalt compound and the alkaline compound while reacting them in the presence of the cobalt oxide to coagulate the cobalt oxide. Method for producing aggregates. 19. The cobalt oxide coagulant according to claim 16, wherein the cobalt oxide is a reaction product of a divalent cobalt compound and an alkaline compound, or the reaction product is heated and calcined. Manufacturing method of aggregate. 20. The method according to claim 20, wherein the cobalt oxide is oxidized while reacting the divalent cobalt compound and the alkaline compound in the medium, or oxidized after reacting in the medium. Item 18. The method for producing a cobalt oxide aggregate according to Item 16.