JP2003313030A - High tap density basic cobalt carbonate powder and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high tap density basic cobalt carbonate powder suitable as a raw material of lithium cobalt oxide as a positive electrode material of a secondary battery, and a method for producing the same. SOLUTION: The aqueous solution saturated with carbon dioxide gas is stirred while supplying an aqueous solution of a cobalt salt and an alkaline aqueous solution. After the formation and deposition of basic cobalt carbonate, the supply is stopped, and the aggregation of basic cobalt carbonate is broken by stirring. Thereafter, the supply of the aqueous cobalt salt solution and the aqueous alkali solution is restarted, and the stirring is continued to grow the particles to an average particle size of 5 to 20 μm. The resulting basic cobalt carbonate powder has a true spherical or elliptical shape,
Average particle size is 5 to 20 μm and tap density is 1.7
g / cm ³ or more.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a basic cobalt carbonate powder used as a raw material for lithium cobalt oxide, which is a positive electrode material of a lithium battery, particularly a basic tap carbonate powder having a high tap density.

[0002]

2. Description of the Related Art Basic cobalt carbonate is used as a starting material for cobalt oxide and the like, and is also used as a material for lithium cobalt oxide which is a positive electrode material of a lithium battery which is one of secondary batteries.

In recent years, the required characteristics of secondary batteries have become highly functional with the progress of advanced information technology, so that it is also required to improve the quality characteristics of basic cobalt carbonate powder, which is a raw material of the positive electrode material, and particularly the shape thereof. A powder with a spherical shape and a high tap density is required. Incidentally, the tap density of commercially available basic cobalt carbonate is, for example, about 0.5 to 0.7 g / cm ^{3 in} the case of the first grade reagent manufactured by Wako Pure Chemical Industries, Ltd.

[0004]

A conventional method for producing basic cobalt carbonate is, for example, JP-A-7-1876.
As described in Japanese Patent Publication No. 81-81, a method is known in which an aqueous solution of a cobalt salt and an alkali carbonate solution are continuously and simultaneously supplied to a reaction system, and the reaction is performed while controlling the temperature and pH of the reaction system within a predetermined range.

However, the basic cobalt carbonate powder obtained by this method has an irregular shape and an extremely nonuniform particle size, and particles having hollow inside are also mixed, and the tap density is 0. It was about 8 to 1.2 g / cm ³ . Therefore, the tap density of lithium cobalt oxide produced by firing this as a raw material was also 2.0 g / cm ³ or less, which was not sufficient as a positive electrode material for secondary batteries.

The present invention has been made in view of such conventional circumstances.
An object of the present invention is to provide a basic cobalt carbonate powder having a high tap density, which is suitable as a raw material of lithium cobalt oxide which is a positive electrode material of a secondary battery, and a method for producing the same.

[0007]

In order to achieve the above object, the high-tap-density basic cobalt carbonate powder provided by the present invention has a spherical or elliptical shape and an average particle size of 5 to 2.
The tap density is 0 μm and the tap density is 1.7 g / cm ³ or more.

In addition, according to the method for producing a high-tap-density basic cobalt carbonate powder according to the present invention, after the cobalt salt aqueous solution and the alkaline aqueous solution are supplied to the aqueous solution saturated with carbon dioxide while stirring, basic cobalt carbonate is formed and deposited. The supply of the cobalt salt aqueous solution and the alkaline aqueous solution is stopped, the agglomeration of the basic cobalt carbonate is crushed by stirring, and then the supply of the cobalt salt aqueous solution and the alkaline aqueous solution is restarted and the stirring is continued to remove the basic cobalt carbonate. Average particle size 5-20μ
The feature is that grains are grown to m.

In the method for producing the high tap density basic cobalt carbonate powder of the present invention, the reaction temperature is 20 to 80 ° C.
It is preferable to control to a substantially constant value within the range. Further, when crushing aggregates by stirring, it is preferable to adjust the average particle size of basic cobalt carbonate after crushing to 5 μm or less.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION In the method of the present invention, first, an aqueous cobalt salt solution and an alkaline aqueous solution are continuously fed simultaneously to an aqueous solution saturated with carbon dioxide while stirring to form and precipitate basic cobalt carbonate. As the cobalt salt aqueous solution, an aqueous solution of any one of sulfate, chloride and nitrate,
Alternatively, a mixed solution thereof can be used. Further, the reason why an aqueous solution in which carbon dioxide gas is sufficiently saturated is used is that it is generally said that basic cobalt carbonate forms a carbonate complex and dissolves, and therefore it is necessary to contain a high concentration of carbonate ion.

In the step of producing the basic cobalt carbonate, it is preferable to keep the reaction temperature at a substantially constant temperature within the range of 20 to 80 ° C. The reaction temperature is kept constant in order to keep the carbonate ion concentration in the reaction system constant. However, if the reaction temperature is lower than 20 ° C., cooling is required in the summer, which leads to an increase in cost. On the contrary, if the reaction temperature exceeds 80 ° C., the basic cobalt carbonate produced is remarkably oxidized, which is not preferable.

[0012] In the basic cobalt carbonate, primary particles rapidly agglomerate with each other during initial production, the particles become indefinite, and the inside of the particles tends to be hollow. In order to suppress this, after the basic cobalt carbonate is generated, the supply of the aqueous cobalt salt solution and the aqueous alkali solution to the reaction system is stopped, preferably when the particle size is 10 μm or less. The time point at which the particle size becomes approximately there is between 0.5 hours and 3 hours from the start of the reaction, although it depends on the reaction conditions.

By stopping this supply, the growth of the basic cobalt carbonate powder is suppressed, and by further agitating the basic cobalt carbonate during the stop of the supply, the agglomerates of the secondary particles are physically disintegrated. During the physical disintegration of the agglomerates by this stirring,
The average particle size of the basic cobalt carbonate in the liquid is preferably 5 μm or less, more preferably 3 μm or less.

After that, the supply of the aqueous cobalt salt solution and the aqueous ammonia solution to the reaction system is restarted, and the reaction temperature is set to 20-80.
Stirring is performed while keeping the temperature substantially constant within the range of 0 ° C., and grain growth is performed until the average particle size of the basic cobalt carbonate is within the range of 5 to 20 μm. The basic cobalt carbonate powder obtained is filtered, washed with water, and then dried.

The basic cobalt carbonate powder of the present invention thus obtained has a spherical or elliptical shape, a solid interior, and an average particle size of 5 to 20 μm. Further, the tap density of this basic cobalt carbonate powder is as high as 1.7 g / cm ³ or more, and by using this basic cobalt carbonate powder as a raw material, cobalt acid having a satisfactory tap density exceeding 2.0 g / cm ³ can be obtained. Lithium powder can be obtained.

[0016]

【Example】Example 1 Dissolve 236 g of cobalt sulfate heptahydrate in 1 liter of pure water.
After that, an aqueous solution having a cobalt concentration of 50 g / l was prepared.
In addition, 500 ml of 25% solution of ammonia water is added to 500 ml.
Was dissolved in pure water to prepare an aqueous ammonia solution. Outlet
Pour 1.5 liters of pure water into a 2 liter beaker with
Carbon dioxide for 30 minutes at a flow rate of 0.8 liters per minute
Was supplied for a while to obtain an aqueous solution saturated with carbon dioxide.

To the aqueous solution saturated with carbon dioxide gas, while continuously supplying carbon dioxide gas, the cobalt sulfate aqueous solution prepared above and the aqueous ammonia solution are continuously supplied simultaneously, and stirring is continued to form basic cobalt carbonate powder. It was generated and precipitated. At that time, the cobalt sulfate salt aqueous solution 1
The flow rate was 1.2 ml per minute, and the aqueous ammonia solution was supplied with a metering pump at a flow rate of 0.8 ml per minute. The liquid temperature in the beaker was maintained at 50 ° C.

After a lapse of 1.5 hours from the start of the addition of the cobalt sulfate aqueous solution and the ammonia aqueous solution, the supply of the cobalt sulfate aqueous solution and the ammonia aqueous solution was stopped, and the stirring of the solution was continued for 30 minutes. By this stirring, the agglomerates of the secondary particles were physically destroyed, and the average particle size of the basic cobalt carbonate powder was adjusted to 5 μm or less.

After that, continuous supply of the aqueous solution of cobalt sulfate and the aqueous solution of ammonia was restarted, and while continuing stirring, 4
The reaction was carried out for 8 hours. The obtained basic cobalt carbonate powder was suction-filtered, washed with water and washed with repulp, and then dried in the air at 80 ° C. for 12 hours.

The basic cobalt carbonate powder obtained was spherical and had an average particle size of 12.2 μm. When the tap density of this basic cobalt carbonate powder was measured, it was 1.9.
It was 5 g / cm ³ . Moreover, the tap density of the lithium cobalt oxide powder produced by firing this as a raw material is 2.45 g.
It was / cm ^3.

[0021]Comparative Example 1 Under the same conditions as in Example 1 above, basic cobalt carbonate powder
Although it was produced, cobalt sulfate aqueous solution
In the case of Example 1 without stopping the supply of the monia aqueous solution,
Generate basic cobalt carbonate powder for the same time as the total reaction time
It was deposited.

The basic cobalt carbonate powder obtained was indefinite in shape, had a hollow interior, and had an average particle size of 20 μm. The tap density of the basic cobalt carbonate powder was 1.33 g / cm ³ .

[0023]Example 2 Carbon dioxide saturated aqueous solution prepared in the same manner as in Example 1 above
While continuing to supply carbon dioxide to the liquid, the cobalt concentration
50 g / l cobalt chloride salt aqueous solution and 11% sodium hydroxide
Aqueous liquor solution is continuously supplied at the same time, and stirring is continued to remove salt
A basic cobalt carbonate powder was generated and deposited. At that time,
The Baltic salt aqueous solution has a flow rate of 1.2 ml per minute, and water
The aqueous solution of sodium oxide is supplied at a flow rate of 0.8 ml per minute.
I paid. The liquid temperature in the beaker was maintained at 50 ° C.

After a lapse of 1.5 hours from the start of the addition of the cobalt chloride aqueous solution and the sodium hydroxide aqueous solution, the supply of the cobalt chloride aqueous solution and the sodium hydroxide aqueous solution was stopped, and the stirring of the solution was continued for 30 minutes. By this stirring, the agglomerates of the secondary particles were physically destroyed, and the average particle size of the basic cobalt carbonate powder was adjusted to 5 μm or less.

After that, continuous supply of the cobalt sulfate aqueous solution and the sodium hydroxide aqueous solution was restarted, and the reaction was carried out for 48 hours while stirring. The obtained basic cobalt carbonate powder was suction filtered, washed with water and repulp washed, and then dried in the air at 80 ° C. for 12 hours.

The basic cobalt carbonate powder obtained was spherical and had an average particle size of 10.8 μm. When the tap density of this basic cobalt carbonate powder was measured, it was 1.8
It was ³ g / cm ³ . Moreover, the tap density of the lithium cobalt oxide powder produced by firing this as a raw material is 2.35 g.
It was / cm ^3.

[0027]Comparative example 2 Under the same conditions as in Example 2 above, the basic cobalt carbonate powder
Although it was generated, cobalt chloride salt aqueous solution and hydroxy
Total of Example 2 without stopping the supply of the aqueous sodium chloride solution
Generate basic cobalt carbonate powder for the same time as the reaction time
I let it out.

The basic cobalt carbonate powder thus obtained had an irregular shape and a hollow interior, and its average particle size was 20 μm. The tap density of the basic cobalt carbonate powder was 1.26 g / cm ³ .

[0029]Comparative Example 3 Dissolve 223 g of cobalt sulfate heptahydrate in 1 liter of pure water.
After that, cobalt sulfate aqueous solution with a cobalt concentration of 46 g / l
Was adjusted. Also, 150 g of anhydrous sodium carbonate aqueous solution
Is dissolved in 1 liter of pure water and sodium hydrogen carbonate water is added.
The solution was adjusted.

Pure water 0.25 in a 3 liter beaker
The above cobalt sulfate aqueous solution was continuously supplied to a liter at a flow rate of 3 ml per minute by a metering pump, and at the same time, the above sodium hydrogen carbonate solution was intermittently supplied by a metering pump controlled by a pH controller, and the inside of the beaker While maintaining the liquid temperature of 50 ° C., the mixture was stirred for 5 hours.

The obtained basic cobalt carbonate powder is suction-filtered, washed with water and repulped, and then washed in air at 80
It was dried at ° C for 12 hours. The basic cobalt carbonate powder had an irregular shape and had an average particle diameter of 12 μm.
The tap density of this basic cobalt carbonate powder was measured and found to be 1.03 g / cm ³ .

[0032]

According to the present invention, a basic cobalt carbonate powder having a tap density of 1.7 g / cm ³ or more, which is suitable as a raw material for lithium cobalt oxide which is a positive electrode material of a secondary battery, and a method for producing the same are provided. Can be provided.

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Claims (4)

[Claims] 1. A spherical or ellipsoidal shape, an average particle size of 5 to 20 μm, and a tap density of 1.7 g / cm ^3.
A high tap density basic cobalt carbonate powder characterized by the above. 2. A cobalt salt aqueous solution and an alkaline aqueous solution are stirred while being supplied to an aqueous solution saturated with carbon dioxide, and after the basic cobalt carbonate is produced and deposited, the supply of the cobalt salt aqueous solution and the alkaline aqueous solution is stopped, and the base is stirred. By crushing the agglomeration of the basic cobalt carbonate, and then restarting the supply of the cobalt salt aqueous solution and the alkaline aqueous solution, and continuing stirring,
A method for producing a high tap density basic cobalt carbonate powder, which comprises growing basic cobalt carbonate to an average particle size of 5 to 20 μm. 3. The method for producing a high tap density basic cobalt carbonate powder according to claim 2, wherein the reaction temperature is controlled to a substantially constant value within the range of 20 to 80 ° C. 4. The high tap density according to claim 2, wherein the average particle size of the basic cobalt carbonate after crushing is adjusted to 5 μm or less when crushing the agglomerates by stirring. Method for producing basic cobalt carbonate powder.