JP3255078B2 - Method for producing nickel hydroxide - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cathode material for a small secondary battery used in personal computers, mobile phones, etc. and a cathode material for a secondary battery used in electric vehicles and the like. The present invention relates to a method for producing nickel hydroxide particles having a tap density.

[0002]

2. Description of the Related Art Nickel hydroxide is used as a positive electrode material of a nickel-cadmium battery, which is one of secondary batteries, and a positive electrode material of a nickel-hydrogen battery.

[0003] With the advance of the information society, personal computers and mobile phones have been remarkably popularized as media, and the demand for the characteristics of secondary batteries used in these media has also become more sophisticated.
The quality of nickel hydroxide as a positive electrode material is also required to have higher properties than before.

In recent years, as a positive electrode substrate of a secondary battery, instead of a conventional sintered substrate having a porosity of 75 to 80%, 9
A foamed metal substrate having a porosity of 0 to 95% has been developed, and the substrate can be filled with nickel hydroxide as an active material more than ever.

In order to make full use of the function of this foamed metal type substrate, it is required that the tapping density of nickel hydroxide be sufficiently high, for example, 2.30 g / ml or more. However, if the tapping density of nickel hydroxide is not sufficiently high, a high utilization rate and a discharge rate of the active material cannot be obtained, and a sufficient improvement in capacity performance as a secondary battery cannot be obtained.

Accordingly, various production methods for increasing the tapping density of nickel hydroxide have been proposed.

For example, Japanese Patent Application Laid-Open No. 63-16556 discloses that a nickel salt aqueous solution and a caustic alkali aqueous solution are introduced into the same tank and sufficiently stirred to control the supply concentration, the tank temperature, the supply liquid flow rate and the tank pH. To produce nickel hydroxide. However, the tapping density of nickel hydroxide obtained by this method is 1.45 to 1.95 g / ml, and a tapping density sufficient for use as a positive electrode material of a secondary battery cannot be obtained.

Japanese Patent Application Laid-Open No. Hei 7-165428 discloses that a nickel salt aqueous solution, a caustic aqueous solution, and an ammonia aqueous solution are continuously supplied at a constant rate to a reaction tank having a filtering function.
After the volume of the reaction tank reaches a predetermined amount, the fine nickel hydroxide in the reaction tank is removed by a filtration function, and the supply is stopped after adding a predetermined amount of the supply liquid while keeping the volume of the reaction tank constant. Describes a method for producing nickel hydroxide by taking it out of a reaction tank.

However, the tapping density of the nickel hydroxide obtained by this method is 1.93 to 2.08 g / ml, which is not sufficient for use as a positive electrode material of a secondary battery.

[0010]

As described above, in the conventional method for producing nickel hydroxide as a positive electrode material for a secondary battery, a pH control is basically used as a reaction condition, and a delicate control of a supply liquid amount is performed. is necessary. Also, pH
Since the measured value changes sensitively due to temperature changes, deterioration of the pH meter, and surface deposits on the pH meter, it is very difficult to always keep the inside of the reaction system in a steady state. Moreover,
The manufacturing method itself is complicated.

[0011] Therefore, the problem to be solved by the present invention is that the pH only needs to be within a wide range of 9 to 14, and the most suitable shape for filling a foamed metal type substrate which is a positive electrode substrate of a secondary battery. An object of the present invention is to provide a method for continuously and easily producing nickel hydroxide having a particle size and a tapping density with a simple control. The shape is a true sphere, the particle size is in the range of about 5 to 50 μm, and the tapping density is 2.
The purpose is to obtain nickel hydroxide of 30 g / ml or more.

[0012]

That is, the present invention provides an aqueous solution of a nickel salt and 0.5 equivalent of ammonia per equivalent of nickel.
An aqueous ammonia solution equivalent to 6 equivalents and an aqueous caustic alkali solution of 0.9 to 1.5 equivalents of caustic are simultaneously and continuously supplied at a constant rate, and the variation in the supply of these aqueous solutions is within ± 5%. A reaction tank that produces nickel hydroxide under stirring conditions, a ripening tank that continuously overflows and supplies nickel hydroxide particles and an aqueous solution from the reaction tank, and ripens under stirring conditions; This is a method in which nickel hydroxide is produced by a solid-liquid separation tank in which nickel oxide particles and an aqueous solution are continuously overflowed and supplied, and the nickel hydroxide and the aqueous solution are continuously taken out of the system.

[0013] The present invention further provides the above production method,
This is a method for producing nickel hydroxide by continuously recycling and supplying a part of the nickel hydroxide particles taken out of the solid-liquid separation tank to the reaction tank within a fluctuation range of ± 5%.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The manufacturing method of the present invention will be described below in detail with reference to the flowcharts of FIGS.

The nickel salt aqueous solution used in the present invention includes nickel salts such as nickel sulfate, nickel nitrate and nickel chloride, and these salts may be used alone or as a mixture of two or more.

The nickel concentration of the nickel salt aqueous solution is 20
It is desirable to use in the range of about 250 g / l. 2
If the amount is less than 0 g / l, the productivity may decrease,
If it is 50 g / l or more, undissolved nickel salts remain in the aqueous solution, and it becomes impossible to supply a constant amount at a predetermined nickel concentration.

As the aqueous ammonia solution, aqueous ammonia or ammonia gas is used. When used as aqueous ammonia, it is preferable to use an aqueous solution having a concentration of 5 to 28%. Usually, the aqueous ammonia solution is directly supplied to the reaction tank, but a predetermined amount may be mixed with the supplied nickel salt aqueous solution in advance and supplied to the reaction tank. in this case,
The amount of ammonia supplied to the reaction tank is [Ni (N
The X value required to form a nickel ammonium complex of H ₃ ) _x ] ²⁺ is in the range of 0.5 to 6. The reason for this will be described later.

As the aqueous caustic alkali solution, an alkali metal salt such as caustic soda and caustic potassium is used.
It is good to use as a 0% concentration aqueous solution. in this case,
The supply amount of the caustic alkali supplied to the reaction tank is in the range of 0.9 to 1.5 times the equivalent required for producing nickel hydroxide.

The nickel salt is easily converted to a nickel salt with ammonia.
This nickel complex forms a nickel-ammonium complex
When alkali is supplied to water, water is
Nickel oxide is produced. [Ni (NH_Three)_x]²⁺+2 (OH)^- = Ni (OH)_Two↓ + XNH_Three↑ ・ ・ ・ (1)

The reaction for producing nickel hydroxide by this means:
The dissociation of nickel-ammonium complex is rate-limiting
However, when the ammonia supply amount (X) is less than 0.5
Is insufficient due to lack of ammonia
Nickel / ammonium complex salt is not formed and nickel salt
Direct reaction between phenol and alkali, ie, hydroxylation according to equation (2)
Nickel is produced. In the formation of nickel hydroxide
Equation (2) has a higher reaction rate than equation (1). Ni²⁺+2 (OH)^- = Ni (OH)_Two↓ ・ ・ ・ (2)

Therefore, when nickel hydroxide is to be produced by the dissociation reaction of the formula (1), the optimum supply amount of ammonia is such that the X value of the formula (1) is in the range of 0.5 to 6.

If less than 0.5, as described above, (2)
The reaction of the formula occurs preferentially, and the nucleation of nickel hydroxide occurs instantaneously, whereby the crystal growth of nickel hydroxide is inhibited, and only nickel hydroxide particles having a fine particle diameter can be obtained. In this case, even though the nickel hydroxide particles and the aqueous solution are continuously overflowed from the reaction tank and then matured sufficiently in the aging tank, the apparent particle size of the nickel hydroxide increases, but the particle shape is irregular. Only an uneven surface is generated. If it exceeds 6, the nickel-ammonium complex salt becomes saturated and ammonia gas increases, so that it is not economical.

The supply amount of caustic is nickel hydroxide
0.9 to 1.5 equivalents required to produce
It is. . If it is less than 0.9, the yield of nickel hydroxide is low.
Not only do they fall, but also unreacted
Since there is a lot of nickel, this liquid treatment is necessary and economic
Not a target. If it exceeds 1.5, nickel hydroxide is formed during the reaction.
To (OH)^- Nucleation is facilitated by excess
Many ungrown nickel hydroxide particles with a fine particle size
Caustic alkaline unit with respect to nickel
It is not economical because it increases.

In the method of the present invention, the supply amounts of the aqueous nickel salt solution, the aqueous ammonia solution and the aqueous caustic solution to be supplied to the reaction vessel must both be within ± 5%. . When the fluctuation range of these supply amounts exceeds ± 5%, even if the above-mentioned conditions are satisfied, the nickel hydroxide particles having the optimum shape, particle size and tapping density as the cathode material for the secondary battery are used. No production is obtained.

That is, the rate of nucleation of nickel hydroxide and the rate of crystal growth from this nucleus depend on the amount of nickel in the reaction vessel.
It is determined by the amounts of ammonia and alkali, and nucleation and crystal growth can be maintained in a steady state only when the supply amounts of these are kept constant.

Even if the amount of nickel and ammonia in the reaction tank is kept constant, if the amount of alkali frequently increases and decreases and changes, the nucleation increases more than the crystal growth, or the nucleation occurs. Because crystal growth takes precedence over nickel hydroxide particles, nickel hydroxide particles having an optimal shape, particle size and tapping density cannot be obtained.

Even if the amount of nickel and alkali is kept constant, if the amount of ammonia frequently increases and decreases and changes, the amount of nickel-ammonium complex salt changes accordingly, and the dissociation reaction rate at the time of reaction with alkali. And nickel hydroxide particles having the optimum shape, particle size and tapping density cannot be obtained.

Also, even if the amounts of ammonia and alkali are kept constant, if the amount of nickel frequently increases and decreases, the amount of nickel-ammonia complex changes accordingly, and the dissociation reaction rate during the reaction with alkali. , And the balance between nickel and the amount of alkali is also lost, so that the balance between nucleation and crystal growth is also changed, and it is not possible to obtain nickel hydroxide having an optimum shape, grain size and tapping density.

In the method of the present invention, there is further provided an aging tank in which the nickel hydroxide particles produced in the reaction tank and the aqueous solution are continuously overflowed and supplied, and aging is performed under stirring conditions.

By providing this maturation tank, even if unreacted nickel is present in the reaction tank, the reaction can be completed completely. Further, the nickel hydroxide particles present in the aqueous solution come into contact with each other to form particles. The surface becomes smooth and true spherical, making it ideal as a cathode material for secondary batteries.
Nickel hydroxide having shape, particle size and tapping density can be produced.

In the method of the present invention, there is further provided a solid-liquid separation tank in which the nickel hydroxide particles and the aqueous solution are continuously overflowed and supplied from the aging tank, and the nickel hydroxide particles and the aqueous solution are continuously taken out of the system. It is to make.

This solid-liquid separation is easily performed by utilizing the spontaneous sedimentation of the nickel hydroxide particles, continuously taking out the nickel hydroxide slurry from the lower part of the solid-liquid separation tank, and taking out the aqueous solution from the upper part by overflowing. I can. That is, a device such as a thickener can be used.

The capacity of the solid-liquid separation tank is sufficient for a tank having a residence time of about 2 hours with respect to the supply amount from the aging tank. This is because the nickel hydroxide particles produced by the method of the present invention have a high spontaneous sedimentation rate, so that solid-liquid separation can be easily performed.

Another method of the present invention is to continuously supply, that is, recycle, a part of the nickel hydroxide slurry taken out of the solid-liquid separation tank as shown in FIG. Increases the average particle size. The amount of nickel hydroxide to be recycled may be up to about 10 times (by weight) the amount of nickel hydroxide particles generated in the reaction tank. The preferred recycling amount is 0.3 to
It is about 5 times the amount.

In this case, of the amount of nickel hydroxide taken out of the solid-liquid separation tank, the steady state is always maintained by always taking the amount of nickel hydroxide generated in the reaction tank out of the system. Also in this case, the supply fluctuation range of the amount of nickel hydroxide particles supplied to the reaction tank is set to be within ± 5%.

As described above, by continuously recycling the nickel hydroxide particles to the reaction tank, nickel hydroxide particles having a constant history can be always present in the reaction tank. By growing the crystal as a nucleus, it is possible to produce nickel hydroxide having a desired particle size while maintaining the shape and the tapping density, which is optimal as a positive electrode material for a secondary battery. That is, the particle size can be increased by increasing the recycling amount of the nickel hydroxide particles.

The temperature of each tank is set to 0 to 60 ° C. When the temperature exceeds 60 ° C., the volatilization loss of ammonia gas becomes large. The pH may be in the range of 9-14. The pH fluctuates easily in the bath, but pH control is not particularly required within this range.

The residence time of each tank is 1 to 20 hours.
If the time is less than 1 hour, there are many unreacted ones, and the yield of nickel hydroxide deteriorates. It is not economical if it exceeds 20 hours.

Stirring is necessary for uniformly mixing the particles in both the reaction tank and the aging tank. The solid-liquid separation tank may not be stirred. The supply from the reaction tank to the aging tank and from the aging tank to the solid-liquid separation tank may be performed by a metering pump, but the overflow method can supply a fixed amount more easily.

The nickel hydroxide particles obtained in the present invention are intended to have a tapping density of at least 2.30 g / ml. For this purpose, the shape is preferably spherical, and the average particle size is about 5 to 50 μm. It is preferable that the distribution is moderately large and small, and this object is achieved by the present invention.

The tapping density can be measured as A / Bg / ml when a certain amount (Ag) of nickel hydroxide particles is put in a container, and the container is tapped 100 times and the filled volume is Bml.

[0042]

The present invention will be specifically described with reference to the following examples and comparative examples.

[0043]

Example 1 A 60 L capacity reaction tank and an aging tank each having an overflow opening at the top were installed, and nickel hydroxide particles were supplied at the upper opening and the lower part supplied from the overflow opening of the aging tank. An apparatus provided with a 20-L capacity solid-liquid separation tank having a sampling port was used.

A nickel salt solution having a nickel concentration of 12
44.4 ± 0.5 ml of 0 g / L nickel sulfate aqueous solution
Per minute, a 25% aqueous sodium hydroxide solution as a caustic aqueous solution at a supply rate of 13.7 ± 0.2 ml / min as a 25% aqueous ammonia solution.
The mixture was continuously supplied at a supply rate of 5.5 ± 0.3 ml / min into a well-stirred reaction vessel, and reacted for 12 hours.

At this time, the amount of ammonia is [Ni (NH
₃ ) The X value required to form a nickel ammonium complex of _x ] ²⁺ was 2.0, and the amount of sodium hydroxide was 1.13 times the equivalent required to produce nickel hydroxide. .

The nickel hydroxide particles and the aqueous solution produced in the reaction tank are continuously supplied to a well-stirred aging tank through an overflow opening at the top of the reaction tank. , And was continuously supplied to the solid-liquid separation tank.

In the solid-liquid separation tank, the nickel hydroxide particles and the aqueous solution are separated by utilizing the natural sedimentation of the nickel hydroxide particles, and the aqueous solution is continuously drained from the upper part of the solid-liquid separation tank by overflowing. The nickel hydroxide particles were continuously withdrawn from the mixture, washed with water and filtered, and dried to obtain nickel hydroxide particles as a product. The temperature in both the reaction tank and the aging tank is 4
0 ± 1 ° C.

When the nickel concentration of the aqueous solution overflowing from the reaction tank and the aging tank was analyzed, 1.2
6 g / l and 0.02 g / l, and the final nickel recovery was almost 100%.

The water content of the nickel hydroxide after filtration was 8.3%, and the filterability was very good. The shape of the nickel hydroxide thus obtained was observed by an electron microscope and found to be a true sphere. The average particle size is 14.6 μm, and the tapping density is 2.32 g.
/ Ml. FIG. 3 shows an electron micrograph of nickel hydroxide.

[0050]

Example 2 Apparatus for reaction tank, aging tank, solid-liquid separation tank,
The concentrations and supply amounts of the nickel salt aqueous solution, the ammonia aqueous solution, and the caustic aqueous solution were performed under the same conditions as in Example 1.

Further, the nickel hydroxide particles having a slurry concentration of 50% taken out from the lower part of the solid-liquid separation tank were 8.5 ±.
The supply amount of 0.1 ml / min, that is, the recycled amount of nickel hydroxide particles was continuously supplied into the reaction tank at the same amount as the amount of nickel hydroxide generated in the reaction tank.

When the nickel concentration of the aqueous solution overflowing from the reaction tank and the aging tank was analyzed,
4 g / l and 0.01 g / l, and the final nickel recovery was almost 100%.

The water content of the nickel hydroxide after filtration was 7.9%, and the filterability was very good. The shape of the nickel hydroxide thus obtained was observed by an electron microscope and found to be a true sphere. The average particle size is 17.7 μm, and the tapping density is 2.37 g.
/ Ml.

[0054]

Example 3 Example 3 was carried out under the same conditions as in Example 2 except that the supply amount of nickel hydroxide particles having a 50% slurry concentration was 25.5 ± 0.3 ml / min. The amount of nickel hydroxide particles recycled in this example was three times the amount of nickel hydroxide generated in the reaction tank.

When the nickel concentration of the aqueous solution overflowing from the reaction tank and the aging tank was analyzed,
The nickel recovery was 9 g / l and 0.01 g / l, and the final nickel recovery was almost 100%.

The water content of the nickel hydroxide after filtration was 8.5%, and the filterability was very good. When the shape of the nickel hydroxide thus obtained was observed with an electron microscope, it was perfectly spherical. The average particle diameter is 20.0 μm, and the tapping density is 2.33.
g / ml. FIG. 4 shows an electron micrograph of nickel hydroxide.

[0057]

Comparative Example 1 The same tank was used as in Example 1, and the same aqueous solution concentration was used. The supply amounts of the nickel salt aqueous solution and the ammonia aqueous solution were the same as those in Example 1, and the fluctuation range was within ± 5%.
As a result of automatic control to be in the range of 2.5 to 12.6, the supply amount of caustic alkali was 23.5 ± 1.9 ml / min, and the fluctuation range was ± 8%.

The nickel concentration of the aqueous solution overflowing from the reaction tank and the aging tank was analyzed.
At 5 g / l and 0.87 g / l, considerable nickel remained in the overflow aqueous solution.

The water content of the nickel hydroxide after filtration was 14.7%, and it had an average particle diameter of 15.3 μm and a tapping density of 1.84 g / ml.

[0060]

Comparative Example 2 The same tank was used as in Example 1, and the same aqueous solution concentration was used. The supply amount of the aqueous caustic alkali solution and the aqueous ammonia solution and the supply amount of the nickel hydroxide particles were the same as those in Example 2, and the fluctuation range was within ± 5%. As a result of automatic control to be in the range of 5 to 12.6, the supply amount of the nickel salt was 45.5 ± 4.8 ml / min, and the fluctuation range was ± 10.5.
%Met.

When the nickel concentration of the aqueous solution overflowing from the reaction tank and the aging tank was analyzed, it was 2.2.
At 6 g / l and 0.58 g / l, considerable nickel remained in the overflow aqueous solution.

The water content of the nickel hydroxide after filtration was 14.3%, the average particle diameter was 23.3 μm, and the tapping density was 1.86 g / ml. FIG. 5 shows an electron micrograph of nickel hydroxide.

[0063]

According to the method of the present invention, it has a perfect spherical shape and a particle size distribution particularly suitable as a cathode material for a secondary battery, and as a result, a high tapping density of 2.30 g / ml or more is obtained. Nickel hydroxide particles can be produced easily and continuously.

[Brief description of the drawings]

FIG. 1 is a process chart of a nickel hydroxide production process of the present invention.

FIG. 2 is a diagram showing a nickel hydroxide production process of the present invention in which a nickel hydroxide slurry is partially recycled.

FIG. 3 is a photomicrograph of nickel hydroxide obtained in Example 1.

FIG. 4 is a photomicrograph of nickel hydroxide obtained in Example 3.

FIG. 5 is a photomicrograph of nickel hydroxide obtained in Comparative Example 2.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Hiromasa Yakushiji Hachinohe City, Aomori Prefecture Ohara Kawaragi character Toyama Nitta (without address) Taiheiyo Metal Co., Ltd. Hachinohe Works (56) References JP 10-182164 ( JP, A) JP-A-2-6340 (JP, A) JP-A-10-97856 (JP, A) JP-A-7-165428 (JP, A) JP-A-7-245104 (JP, A) JP JP-A-6-191855 (JP, A) JP-A-10-25117 (JP, A) JP-A-10-125319 (JP, A) JP-A-9-139206 (JP, A) JP-A-5-254847 (JP) , A) (58) Field surveyed (Int. Cl. ⁷ , DB name) C01G 1/00-57/00 JICST file (JOIS) WPI (DIALOG)

Claims (5)

(57) [Claims] 1. An aqueous nickel salt solution, an aqueous ammonia solution, and an aqueous caustic solution are simultaneously and continuously supplied to a reaction vessel to produce nickel hydroxide under stirring conditions. The aqueous solution is continuously overflowed and supplied to an aging tank, aged under stirring conditions, and nickel hydroxide particles and an aqueous solution are continuously overflowed from this aging tank and supplied to a solid-liquid separation tank. And continuously taking it out of the system. 2. A nickel salt aqueous solution, an ammonia aqueous solution, and a caustic alkali aqueous solution are simultaneously and continuously supplied to a reaction tank, and nickel hydroxide is generated under stirring conditions. The aqueous solution is continuously overflowed and supplied to an aging tank, aged under stirring conditions, and nickel hydroxide particles and an aqueous solution are continuously overflowed from this aging tank and supplied to a solid-liquid separation tank. Characterized by continuously taking out of the system outside the system and continuously supplying a part of the nickel hydroxide particles taken out of the solid-liquid separation tank to the reaction tank. 3. The amount of aqueous solution supplied to the reactor is 0.5 to 6 equivalents of ammonia and 0.9 to 1.5 equivalents of caustic alkali per 1 equivalent of nickel. The method described in. 4. The method according to claim 1, wherein the variation width of each aqueous solution supplied to the reaction tank is within ± 5%. 5. The method according to claim 2, wherein each of the supply amount of the aqueous solution supplied to the reaction tank and the supply amount of the nickel hydroxide particles supplied to be recycled is within ± 5%. the method of.