JPH11292549A - Cobalt hydroxide and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain cobalt hydroxide in the form of hexagonal columnar grains having a specified average grain diameter and a specified average grain height by allowing a divalent cobalt compd. to react with an alkali hydroxide and an alkaline ammonium compd. in an aq. medium. SOLUTION: The cobalt hydroxide has 1-30 μm average grain diameter of the base, 0.2-10 μm average grain height, a hexagonal columnar grain form and a large grain volume. The specific surface area of the grains is as small as 0.1-10 m<2> /g, preferably 0.1-5m<2> /g because of the large grain volume and lithium cobaltate produced from the cobalt hydroxide is almost free from the sintering of primary particles. The cobalt hydroxide is obtd. by allowing a divalent cobalt compd. such as cobalt sulfate to react with 0.5-1.5 equiv. sodium hydroxide and 0.5-1.5 equiv. ammonia in the temp. range of 0-80 deg.C, preferably 10-40 deg.C preferably in an inert gaseous atmosphere.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a raw material for synthesizing cobalt oxide used as a semiconductor material, a pigment and a catalyst.
The present invention relates to cobalt hydroxide useful as a raw material for synthesizing lithium cobalt oxide used as a positive electrode active material of a lithium secondary battery, and a method for producing the same.

[0002]

2. Description of the Related Art With the rapid expansion of small electronic devices such as personal computers and mobile phones in recent years, the demand for lithium secondary batteries has been rapidly increasing, and lithium cobalt oxide has been mainly used as a positive electrode active material. I have. In general, when lithium cobalt oxide is used as a positive electrode active material of a lithium secondary battery, the smaller the particle size of lithium cobalt oxide, the better the charge / discharge characteristics at a high current density, but the stability tends to deteriorate. Therefore, in practice, particles having various particle sizes are used depending on the balance between these characteristics and the application and configuration of the battery. However, it is considered that it is desirable that the lithium cobalt oxide particles be in a single crystal and close to a monodispersed state at any particle size. Such a lithium cobalt oxide is prepared by mixing a powder of a cobalt compound such as cobalt hydroxide, tricobalt tetroxide, or cobalt carbonate with a powder of a lithium compound such as lithium carbonate or lithium hydroxide in a dry system, and then mixing the mixture with a powder of 600 to 1100. It is manufactured industrially through a process of firing at a temperature of about ° C and then pulverizing. The properties of the obtained lithium cobalt oxide are, of course, affected by the conditions of these manufacturing processes, but the particle properties of the cobalt hydroxide used as the cobalt raw material also greatly affect the properties of the lithium cobalt oxide. ing.

[0003] Further, with respect to semiconductor materials, pigments, catalysts, and also cobalt oxide used as a raw material of lithium cobalt oxide, the properties of particles of cobalt hydroxide used as a cobalt raw material have a great influence on the characteristics.

The following method is known as a method for producing cobalt hydroxide. A method of obtaining a precipitate of cobalt hydroxide by reacting an aqueous solution of a divalent cobalt salt or a slurry of a divalent cobalt double salt with an alkali hydroxide in an equivalent amount or more has been proposed (Japanese Patent Publication No. 58-25052). Japanese Patent Application Laid-Open No. 9-22692 discloses that the diameter in the fixed direction is 0.1 to 1 mm.
A method for obtaining cobalt hydroxide having a plate shape at 0 μm is described.

[0005]

The cobalt hydroxide obtained by the above-mentioned prior art is fine particles or those having a large particle diameter in the bottom direction but a thickness of less than 0.2 μm in the end surface direction. And only particles with a small volume are obtained. When obtaining cobalt oxide and lithium cobalt oxide having large particles using such cobalt hydroxide as a raw material, the particles must be grown by firing at a high temperature in a firing step, and at this time, the particles strongly adhere to each other. Or there is a problem that the particles are sintered together. Furthermore, in order to make these particles adhere to each other or to make the sintered particles close to a monodispersed state, the degree of pulverization must be strengthened, and at this time, cobalt oxide, cobalt Lithium oxide has a problem that its properties are deteriorated.

[0006]

In order to develop cobalt oxide and lithium cobalt oxide, which have a large particle volume and a large particle size, and have a small sintering, the inventors of the present invention have proposed a raw material, hydroxide As a result of intensive studies on the improvement of cobalt, the average particle diameter of the bottom surface is 1 to 30 μm, the average particle height is 0.2 to 10 μm, the particle shape is a hexagonal column, the particle volume is large, and the large particle size is large. Of cobalt hydroxide, and that such cobalt hydroxide is suitable for producing cobalt oxide and lithium cobalt oxide having a large particle size. The present inventors have found that the above-mentioned cobalt hydroxide can be obtained by reacting a valent cobalt compound, an alkali hydroxide, and an ammonium compound exhibiting alkalinity, and have completed the present invention.

That is, an object of the present invention is to provide cobalt hydroxide having a large particle volume and a large particle size, and a method for producing the same.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION According to the present invention, the average particle diameter of the bottom surface is 1
Cobalt hydroxide characterized by having a particle size of up to 30 μm, an average particle height of 0.2 to 10 μm, and a hexagonal column shape. In the present invention, the hexagonal column shape refers to a shape in which the bottom surface of most particles has a hexagonal shape, and may include a shape in which a part of the bottom surface has a shape other than a hexagon. No problem. In the present invention, the average particle diameter of the bottom surface (the average value of the length of the longest diagonal line of the hexagonal bottom surface of the particles) is 1 to 30 μm, and preferably 1.5 to 30 μm.
m, more preferably 2 to 20 μm. Furthermore, the average particle height (the average value of the thickness of the particles in the end face direction) is 0.2 to
It is 10 μm, preferably 0.3 to 10 μm, more preferably 0.5 to 10 μm. If the average particle diameter and the average particle height of the bottom face are smaller than the above ranges, for example, lithium cobalt oxide particles produced using cobalt hydroxide as a raw material are not preferable because fine primary particles are sintered. Further, the cobalt hydroxide of the present invention has a small specific surface area due to a large particle volume. A preferred specific surface area is 0.1 to 10 m ² / g, and a more preferred specific surface area is 0.1 to ⁵ m ² / g. If the specific surface area is larger than the above range, for example, lithium cobalt oxide particles produced using cobalt hydroxide as a raw material are not preferable because fine primary particles are sintered.

Next, the present invention relates to a method for producing cobalt hydroxide, comprising the steps of: preparing a divalent cobalt compound in an aqueous medium;
This is a method for producing cobalt hydroxide by reacting an alkali hydroxide and an ammonium compound exhibiting alkalinity. The mechanism by which cobalt hydroxide having a large particle volume and a large particle diameter is produced by such a method is not clear, but is presumed as follows. First, it is considered that the cobalt compound reacts with the ammonium compound exhibiting alkalinity to form a complex compound containing ammonia as an intermediate. This compound is ultimately converted to cobalt hydroxide by an alkali containing at least an alkali hydroxide. However, this conversion reaction proceeds very slowly, so that conditions under which the particle growth reaction becomes dominant are taken. It is thought that it is easy.

[0010] As the divalent cobalt compound used in the production method of the present invention, cobalt sulfate, cobalt chloride, cobalt nitrate and the like can be used.

As the alkali hydroxide, sodium hydroxide, potassium hydroxide and the like can be used. The amount of the alkali hydroxide is 0.1 to the divalent cobalt compound.
It is 5 to 1.5 equivalents, preferably 0.7 to 1.3 equivalents, more preferably 0.8 to 1.2 equivalents. If the amount of the alkali hydroxide is less than the above range, the ammonia-containing complex compound is not converted to cobalt hydroxide or it takes an extremely long time, which is not preferable. Further, when the amount is larger than the above range, the conversion from the ammonia-containing complex compound to cobalt hydroxide is too fast to generate fine particles, and even when large particles are generated, the shape thereof is preferably a thin plate-like particle, which is preferable. Absent.

Further, the ammonium compound exhibiting alkalinity is an ammonium compound exhibiting alkalinity when present in an aqueous medium, such as ammonia gas,
Ammonia water, ammonium carbonate, or the like can be used. A neutral or acidic ammonium compound such as ammonium sulfate, ammonium chloride, and ammonium nitrate is not preferable because an ammonia-containing complex compound is not easily formed. The amount of the ammonium compound is 0.5 to 1.5 equivalents, preferably 0.6 to 1.2 equivalents, more preferably 0.7 to 1.1 equivalents to the divalent cobalt compound. If the amount of the ammonium compound is less than the above range, the ammonia-containing complex compound, which is an intermediate product, has a small ammonia content, so that the conversion reaction to cobalt hydroxide is accelerated, and fine particles are easily generated, which is not preferable. On the other hand, if the amount is larger than the above range, the amount of ammonia in the reaction system increases, so that the conversion reaction to cobalt hydroxide is undesirably slow.

The reaction temperature is 0 to 80 ° C., preferably 5 to 80 ° C.
It is preferable to carry out at a temperature of 60 ° C, more preferably 10 to 40 ° C. If the reaction temperature is high, there is an effect on the shape surface such as an increase in the particle diameter in the bottom direction, and there is an effect on the production surface such as the growth rate can be increased, but if the reaction temperature is higher than the above range, the thickness of the particles becomes thin, It is not preferable because particles having a large volume are not generated. In addition, even if it is lower than the above range, there is almost no difference in shape from the product when reacted at around 0 ° C.,
It is not preferable because it is industrially disadvantageous such that it takes a long time to grow.

This reaction is preferably carried out in an atmosphere of an inert gas such as nitrogen in order to prevent oxidation of the divalent cobalt compound in the aqueous medium. If a trivalent cobalt compound is generated during the reaction, it is not converted into cobalt hydroxide, which is a divalent cobalt compound, so that a mixture of divalent cobalt hydroxide and a trivalent cobalt compound is finally obtained. Is not preferred because

In order to react a divalent cobalt compound, an alkali hydroxide and an alkaline ammonium compound in an aqueous medium, specifically, a divalent cobalt compound, an alkali hydroxide and an alkaline ammonium compound are mixed with an aqueous compound. A method of adding and reacting at the same time in a medium, in an aqueous medium containing a divalent cobalt compound,
A method in which an alkali hydroxide and an ammonium compound exhibiting alkalinity are added at the same time to cause a reaction, and a reaction is performed by simultaneously adding a divalent cobalt compound and an alkali hydroxide to an aqueous medium containing an ammonium compound exhibiting alkalinity. A method of adding a divalent cobalt compound, an alkali hydroxide and an ammonium compound exhibiting alkalinity to an aqueous medium to obtain a reaction product, and then reacting the obtained reaction product with an alkali hydroxide. Reacting a divalent cobalt compound with an ammonium compound exhibiting alkalinity in an aqueous medium,
Next, the reaction can be performed by a method of reacting the obtained reaction product with an alkali hydroxide.

In the above methods (1) to (3), the addition time of the divalent cobalt compound, alkali hydroxide and ammonium compound exhibiting alkalinity can be appropriately set, but is usually 10 minutes to 24 hours, preferably 30 minutes to 20 hours, more preferably It is good to carry out for 1 hour to 15 hours. Addition within the above-mentioned time period is preferable because the generation of fine particles can be prevented and cobalt hydroxide can be obtained under the predominant conditions of particle growth. If the addition time is shorter than the above range, the generation of fine particles becomes remarkable, which is not preferable. If the addition time is made longer, the particles become larger. However, if the addition time is longer than the above range, the reaction time becomes longer, and the effect of making the particles larger is not recognized so much. Also, adding two or three kinds of a divalent cobalt compound, an alkali hydroxide and an alkaline ammonium compound at the same time means that the divalent cobalt compound, the alkali hydroxide and the alkaline ammonium compound are reacted during the reaction period. Means that each of them is present in the reaction system.Specifically, the respective predetermined amounts are added in parallel or continuously, intermittently, or after adding one or two types. Or the addition of species that remain in a short time. In the present invention, it is preferable to add a divalent cobalt compound and an alkali hydroxide in the presence of at least a part of a predetermined amount of an ammonium compound exhibiting alkalinity, or at the same time as the ammonium compound.

The above-mentioned methods are primary methods,
Is a method in which a predetermined amount of a divalent cobalt compound, an alkali hydroxide and an ammonium compound exhibiting alkalinity are added to an aqueous medium at the same time and reacted.
Is a method in which a predetermined amount of an alkali hydroxide and an ammonium compound exhibiting alkalinity are added at the same time to an aqueous medium containing a predetermined amount of a divalent cobalt compound to cause a reaction. This is a method in which a predetermined amount of a divalent cobalt compound and a predetermined amount of an alkali hydroxide are simultaneously added to an aqueous medium containing a predetermined amount of an ammonium compound to be reacted.

On the other hand, the above method is a sequential method. In the method, first, predetermined amounts of a divalent cobalt compound, an alkali hydroxide and an ammonium compound exhibiting alkalinity are added to an aqueous medium. (A specific method of addition is preferably according to the above-mentioned methods.),
A method of obtaining a reaction product and then reacting the obtained reaction product with an alkali hydroxide.In the method, first, in an aqueous medium, a divalent cobalt compound and an ammonium compound exhibiting alkalinity are mixed. The reaction is carried out (preferably, the reaction is carried out by adding or containing a divalent cobalt compound and an ammonium compound according to the above-mentioned methods) and then obtained. This is a method of reacting a reaction product with an alkali hydroxide. The method of reacting the obtained reaction product with alkali hydroxide in the method of the above, adding alkali hydroxide to the slurry of the reaction product, or reacting the reaction product in an aqueous medium solution of alkali hydroxide Or the addition of a slurry of a reaction product and an alkali hydroxide in an aqueous medium at the same time. In this reaction, an alkaline ammonium compound may be present in the alkali hydroxide.

The cobalt hydroxide thus obtained may be aged, filtered, washed,
It may be dried. Drying is preferably performed in an atmosphere of an inert gas such as nitrogen gas so as not to oxidize.

[0020]

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

Example 1 In 500 ml of pure water adjusted to a temperature of 20 ° C., 1 liter of an aqueous solution of cobalt sulfate having a divalent cobalt ion concentration of 60 g / l and 17% aqueous ammonia were added so that the pH of the reaction solution was maintained at 8. Ammonia-containing complex compound slurry was prepared by parallel addition in 3 hours, and then, while maintaining the temperature of the slurry at 20 ° C., an aqueous solution of sodium hydroxide having a concentration of 400 g / l was added in 3 hours to adjust the pH to 12. After further aging for one day, cobalt hydroxide (sample A) of the present invention was obtained. The amounts of ammonia and sodium hydroxide used were 0.9 equivalent and 1.0 equivalent, respectively, relative to cobalt. These operations were performed in a nitrogen gas atmosphere.

Example 2 After adjusting 1 L of an aqueous solution of cobalt sulfate having a divalent cobalt ion concentration of 60 g / L to a temperature of 10 ° C., an aqueous ammonia solution was added until the pH of the aqueous solution became 8, and the ammonia-containing complex compound slurry was removed. Then, while maintaining the temperature of the slurry at 10 ° C., an aqueous solution of sodium hydroxide having a concentration of 400 g / l was added in 6 hours to adjust the pH to 12, and the mixture was aged for 2 days. (Sample B) was obtained. The amounts of ammonia and sodium hydroxide used were 0.9 equivalent and 1.0 equivalent, respectively, relative to cobalt. These operations were performed in a nitrogen gas atmosphere.

Example 3 In 700 ml of 5% aqueous ammonia adjusted to a temperature of 30 ° C., 1 l of an aqueous solution of cobalt sulfate having a divalent cobalt ion concentration of 60 g / l and 200 ml of an aqueous solution of sodium hydroxide having a concentration of 400 g / l in parallel for 6 hours. After the addition, the mixture was aged for 3 days to obtain cobalt hydroxide of the present invention (Sample C). The pH of the slurry was 12 during aging. The amounts of ammonia and sodium hydroxide used were 1.0 equivalent and 1.0 equivalent, respectively, relative to cobalt. These operations were performed in a nitrogen gas atmosphere.

Example 4 1 liter of an aqueous solution of cobalt sulfate having a divalent cobalt ion concentration of 60 g / l was adjusted to a temperature of 20 ° C., and 150 ml of a 17% aqueous ammonia solution was added until the pH of the aqueous solution reached 8.
A mixed solution of 50 g of an aqueous sodium hydroxide solution having a concentration of 0 g / l was added to prepare an ammonia-containing complex compound slurry. Then, while maintaining the slurry at a temperature of 20 ° C., 50 ml of a 17% aqueous ammonia solution and 400 g / l were prepared. The pH was adjusted to 12 by adding 150 ml of an aqueous sodium hydroxide solution having a concentration of 6 over 6 hours, and the mixture was aged for 2 days to obtain cobalt hydroxide of the present invention (Sample D). The amounts of ammonia and sodium hydroxide used were 0.9 equivalent and 1.0 equivalent, respectively, relative to cobalt. These operations were performed in a nitrogen gas atmosphere.

COMPARATIVE EXAMPLE 1 After adjusting 1 L of an aqueous solution of cobalt sulfate having a divalent cobalt ion concentration of 60 g / l to a temperature of 20 ° C., an aqueous solution of sodium hydroxide having a concentration of 400 g / l was added until the pH of the aqueous solution reached 8. Then, while maintaining the temperature of the slurry at 20 ° C., an aqueous solution of sodium hydroxide having a concentration of 400 g / l was added over 3 hours to adjust the pH to 12, and
After aging for days, cobalt hydroxide (sample E) was obtained. The amount of sodium hydroxide used was 1.1 equivalents relative to cobalt. These operations were performed in a nitrogen gas atmosphere.

Comparative Example 2 In 500 ml of pure water adjusted to a temperature of 20 ° C., 1 liter of an aqueous solution of cobalt sulfate having a divalent cobalt ion concentration of 60 g / l and 400 g / l of sodium hydroxide were added at a pH of 12
Was added in parallel for 3 hours, and then aged for 1 day to obtain cobalt hydroxide (sample F) as a comparative sample. The amount of sodium hydroxide used was 1.1 equivalents relative to cobalt. These operations were performed in a nitrogen gas atmosphere.

The cobalt hydroxide obtained in Examples 1 to 4 and Comparative Examples 1 and 2 (samples A to F
Table 1 shows the specific surface area according to the BET method, the average particle diameter of the bottom surface and the average particle height read from an electron micrograph. Further, the sample A of Example 1
Electron micrographs of Sample E of Comparative Example 1 are shown in FIGS. 1 and 2, respectively. From Table 1 and FIGS. 1 and 2, the cobalt hydroxide of the present invention has a large average particle diameter and a large average particle height on the bottom surface, a large particle volume, and a substantially hexagonal particle shape on the bottom surface. The shape was found to be hexagonal.

[0028]

[Table 1]

After drying the cobalt hydroxides (Samples A to D) obtained in the above Examples 1 to 4 at a temperature of 120 ° C. in a nitrogen gas, the Co / Li ratio becomes 1/1 (molar ratio). It was confirmed that lithium cobalt oxide was obtained by mixing with lithium carbonate and firing in air at 900 ° C. for 10 hours.

[0030]

According to the present invention, the average particle diameter of the bottom surface is from 1 to 30.
μm, and average particle height is 0.2 to 10 μm, a cobalt hydroxide characterized in that the particle shape is a hexagonal column, using the cobalt hydroxide of the present invention as a raw material for synthesizing lithium cobalt oxide In addition, it is possible to synthesize lithium cobalt oxide having a large particle size and less interparticle sintering by inheriting the shape and aggregation state of cobalt hydroxide, and have characteristics suitable as a positive electrode active material of a lithium battery. It is useful, as shown below. Further, the present invention is a method for producing cobalt hydroxide, comprising reacting a divalent cobalt compound, an alkali hydroxide, and an ammonium compound exhibiting alkalinity in an aqueous medium, wherein water having a large particle diameter is used. This is a method by which cobalt oxide can be obtained efficiently.

[Brief description of the drawings]

FIG. 1 is an electron micrograph (× 10000) showing the particle structure of Sample A obtained in Example 1.

FIG. 2 is an electron micrograph (magnification: 10,000 times) showing the particle structure of Sample E obtained in Comparative Example 1.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Mitsuo Suzuki 1 Ishiharacho, Yokkaichi-shi, Mie Pref. Ishihara Sangyo Co., Ltd. (72) Inventor Yoshiaki Moriyama 1st Ishiharacho, Yokkaichi-shi, Mie Ishihara Sangyo Co., Ltd. Yokkaichi Office

Claims (8)

[Claims] 1. A cobalt hydroxide having an average particle diameter at the bottom surface of 1 to 30 μm, an average particle height of 0.2 to 10 μm, and a hexagonal column shape. 2. The cobalt hydroxide according to claim 1, wherein the specific surface area is 0.1 to 10 m ² / g. 3. A method for producing cobalt hydroxide, comprising reacting a divalent cobalt compound, an alkali hydroxide, and an ammonium compound exhibiting alkalinity in an aqueous medium. 4. The method for producing cobalt hydroxide according to claim 3, wherein a divalent cobalt compound, an alkali hydroxide and an ammonium compound exhibiting alkalinity are added to the aqueous medium at the same time and reacted. . 5. The cobalt hydroxide according to claim 3, wherein an alkali hydroxide and an ammonium compound exhibiting alkalinity are simultaneously added to the aqueous medium containing the divalent cobalt compound and reacted. Manufacturing method. 6. The cobalt hydroxide according to claim 3, wherein a divalent cobalt compound and an alkali hydroxide are simultaneously added to an aqueous medium containing an ammonium compound exhibiting alkalinity and reacted. Manufacturing method. 7. A reaction product is obtained by adding a divalent cobalt compound, an alkali hydroxide and an ammonium compound exhibiting alkalinity to an aqueous medium, and then reacting the obtained reaction product with an alkali hydroxide. The method for producing cobalt hydroxide according to claim 3, wherein: 8. The method according to claim 3, wherein a divalent cobalt compound is reacted with an ammonium compound exhibiting alkalinity in an aqueous medium, and then the obtained reaction product is reacted with an alkali hydroxide. 3. The method for producing cobalt hydroxide according to item 1.