JPH1025117A - Production of nickel hydroxide - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing nickel hydroxide, capable of facili tating its spheroidization and particle size distribution control for the purpose of raising its packing density. SOLUTION: A reaction vessel is continuously fed with an aqueous solution of nickel salt, ammonia water and an aqueous solution of alkali hydroxide at constant rates, respectively, to carry out a reaction under agitation to produce nickel hydroxide; in parallel with the above process, after the liquid volume in the reaction vessel comes to a specified level, part of the reaction solution is pumped and fed to a solid-liquid separator, the medium liquid thereof is then removed continuously, and only the resultant concentrated slurry is returned to the reaction vessel again, thus keeping the liquid level in the reaction vessel constant. After the slurry concentration in the vessel comes to a specified level, part of the nickel hydroxide slurry to be fed to and concentrated in the solid- liquid separator is either continuously or intermittently drawn out of the reaction system so as to control the slurry concentration in the reaction vessel within a specified range.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a Ni-Cd battery and a Ni-Cd battery.
A method for producing nickel hydroxide, which is a positive electrode active material used in a secondary battery such as an MH battery, is proposed. In particular, a method for producing nickel hydroxide that can easily control the particle size distribution to increase the packing density is proposed.

[0002]

2. Description of the Related Art Nickel hydroxide is mixed with a conductive material and a binder, and filled as a nickel hydroxide-containing paste into the pores of a porous metal body to form a non-sintered nickel positive electrode of an alkaline secondary battery. Used as an active material.

[0003] In order to increase the energy density of the nickel positive electrode, such nickel hydroxide needs to be made into a powder having a high packing density. It is advantageous to use a powder in which different particles are mixed. If nickel hydroxide particles having such a high packing density are used, a high utilization rate and a discharge rate as an active material can be obtained.

Hitherto, various proposals have been made as methods for producing nickel hydroxide particles having a high packing density as described above. For example,. A method has been proposed in which a nickel salt aqueous solution, an aqueous ammonia solution and an alkaline aqueous solution are continuously supplied to a reaction tank, and a reaction mixture is overflowed from the reaction tank to produce nickel hydroxide while maintaining a constant volume of the reaction system. (See JP-A-4-68249). However, in this method, since the amount of the reaction solution is large with respect to the generated nickel hydroxide, the reaction tank must be designed large in order to secure the residence time required for the reaction, and the apparatus becomes large. was there.

On the other hand, recently,. A nickel salt aqueous solution, ammonia water and an alkali hydroxide aqueous solution are continuously supplied to the reaction vessel at a constant rate, respectively, and before the reaction system overflows from the reaction vessel, the medium liquid is removed until sufficient stirring can be performed. By repeatedly increasing the capacity of the reaction system by the supply solution for the reaction and decreasing the volume by removing the medium solution, nickel hydroxide is generated, and after adding a predetermined amount of each of the above reaction solutions, the supply of all the reaction solutions is stopped. A method for producing nickel hydroxide particles has been proposed in which the formed particles are taken out of the reaction system and separated (see Japanese Patent Application Laid-Open No. 8-119636).

[0006] Specifically, in this method, as a method for removing the medium liquid before overflowing from the reaction vessel,
The supply of the reaction solution was stopped, and the stirring was made very gentle or stopped, and the formed nickel hydroxide particles were allowed to settle, and the supernatant was taken out of the reaction vessel, or the reaction solution was supplied and stirred. While continuing, a method is employed in which the medium liquid is taken out of the reaction vessel by natural filtration or suction filtration through a filter medium.

However, in the above proposal, the method for producing nickel hydroxide employing the method described above is not an efficient method because it requires time for sedimentation of nickel hydroxide particles. In addition, the method for producing nickel hydroxide adopting the method of (1) uses fine particles (3 to 5) because a filter medium is used.
(μm or less) is difficult to produce, and the particle size distribution cannot be easily controlled. In addition, there is a disadvantage that the filter medium needs to be regenerated or replaced in a relatively short period of time, and maintenance of the apparatus is not easy.

[0008]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned drawbacks of the prior art, and a main object of the present invention is to provide an industrial method for producing nickel hydroxide used in paste form. The object of the present invention is to provide a production method capable of easily performing spheroidization and particle size distribution control for increasing the packing density. Another object of the present invention is to provide a method for efficiently producing nickel hydroxide having a high packing density and a controlled particle size distribution.

[0009]

Means for Solving the Problems The inventors of the present invention have intensively studied for realizing the above-mentioned object, and as a result, have completed the invention having the following contents as the main structure. That is, the present invention provides (1) a nickel salt aqueous solution, an aqueous ammonia solution and an aqueous alkali hydroxide solution which are continuously supplied to a reaction tank at a constant rate, and while the nickel hydroxide is reacted and generated under stirring conditions,
After the liquid volume in the reaction tank reaches a predetermined amount, a part of the reaction solution is pumped up by a pump and supplied to a solid-liquid separation device, and the medium liquid is continuously removed to concentrate only the concentrated slurry again. This is a method for producing nickel hydroxide, wherein the liquid level in the reaction tank is kept constant by returning the liquid to the reaction tank.

(2) An aqueous solution of nickel salt, aqueous ammonia and an aqueous solution of alkali hydroxide are continuously supplied to the reaction tank at a constant rate to generate nickel hydroxide under stirring conditions. After the liquid volume reaches a predetermined amount, a part of the reaction solution is pumped up by a pump and supplied to a solid-liquid separation device, and the medium liquid is continuously removed, and only the concentrated slurry is returned to the reaction tank again. By returning, the liquid level in the reaction tank is kept constant, and after the slurry concentration in the reaction tank reaches a predetermined concentration, a part of the nickel hydroxide slurry to be supplied to the solid-liquid separation device and concentrated is continuously removed. Alternatively, there is provided a method for producing nickel hydroxide, wherein the slurry concentration in the reaction tank is controlled within a predetermined range by taking it out of the reaction system intermittently. In this method, it is desirable to control the slurry concentration in the reaction tank within the range of 200 to 800 g / l.

(3) In the method of the present invention described in (2) above, before the production of nickel hydroxide is completed, the nickel hydroxide slurry taken out of the reaction system for controlling the slurry concentration in the reaction tank is removed. This is a method for producing nickel hydroxide, wherein the particle size distribution of nickel hydroxide is controlled by returning the mixture to the reaction tank again and mixing.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION

(1) In the method for producing nickel hydroxide according to the present invention, after the liquid volume in the reaction tank reaches a predetermined amount, a part of the reaction solution is pumped up by a pump to a solid-liquid separation device provided outside the system. Supply,
It is characterized in that nickel hydroxide is produced by continuously removing the medium liquid and returning only the concentrated slurry to the reaction tank again, while keeping the liquid level in the reaction tank constant. This makes it possible to generate a high-concentration nickel hydroxide slurry in a short time without stopping the supply of the reaction solution and stopping the stirring, so that a spherical nickel hydroxide having a relatively narrow particle size distribution and a high packing density can be obtained. It can be manufactured efficiently.

In such a method of the present invention, it is desirable that the speed at which a part of the reaction solution is pumped up by a pump and supplied to the solid-liquid separation device is at least twice the speed at which the reaction solution is supplied.

In the case of using a thickener, for example, in the case of using a thickener, the reaction solution supplied to the solid-liquid separator is settled down, and only the supernatant is removed from the system and concentrated. Then, the concentrated slurry of nickel hydroxide is returned to the reaction tank by the pump again. At this time, the pump flow rates are set so that the reaction liquid supplied to the reaction tank and the supernatant liquid (medium liquid) removed outside the reaction system are balanced. Thus, nickel hydroxide can be produced while keeping the liquid level in the reaction tank constant.

As such a solid-liquid separation device, a screw decanter or a liquid cyclone can be used in addition to a thickener device.

(2) In the method for producing nickel hydroxide according to the present invention, after the slurry concentration in the reaction tank reaches a predetermined concentration, the nickel hydroxide slurry is supplied to a solid-liquid separation device and concentrated. There is another feature in that nickel hydroxide is produced while continuously or intermittently taking out of the reaction system to control the slurry concentration in the reaction tank within a predetermined range. As a result, the nickel hydroxide particles in the reaction tank grow with the lapse of the reaction time, and spherical nickel hydroxide having a large average particle size and a relatively narrow particle size distribution can be efficiently produced.

In the method of the present invention, when the slurry concentration in the reaction tank reaches about 600 g / l,
Part of the nickel hydroxide slurry to be supplied to the solid-liquid separator and concentrated is taken out of the reaction system continuously or at regular intervals, and the liquid concentration in the reaction tank is in the range of 400 g / l to 800 g / l. It is desirable to keep. The reason is that if the slurry concentration in the reaction tank is too low, low-density nickel hydroxide is likely to be generated, and the densification of the particles becomes insufficient. On the other hand, if the slurry concentration in the reaction tank is too high, fine particles are likely to be generated, and the particle diameter tends to be uneven.

Further, according to the method of the present invention, the slurry of fine nickel hydroxide particles taken out of the reaction tank at an early time is replaced with the slurry of nickel hydroxide particles of large particle size taken out of the reaction tank at a later time. And an arbitrary ratio, followed by filtration, washing and drying to obtain nickel hydroxide having a desired particle size distribution. In particular, in the present invention, before the production of nickel hydroxide as described above is completed, the nickel hydroxide slurry having a small average particle diameter taken out of the reaction system for controlling the slurry concentration in the reaction tank is again added to the reaction tank. If it is mixed back, the particle size distribution of nickel hydroxide for increasing the packing density can be controlled more easily.

In the method of the present invention as described above, the nickel salt used as the reaction solution is not particularly limited as long as it is a salt soluble in water. Acid salts are preferably used. Generally, these nickel salts are 0.5-3.5
The solution is adjusted to an aqueous solution concentration of about mol / l and supplied to the reaction. Further, the supply rate of the nickel salt to the reaction tank is desirably 300 cc / hr to 800 cc / hr per liter of the solution in the reaction tank. The reason for this is that if the supply rate is low, the productivity decreases, while if the supply rate is too high, fine particles are generated and the particles are difficult to grow.

In the method of the present invention, the ammonia water supplied to the reaction vessel as a reaction solution together with the nickel salt is:
It is desirable that the supply amount is in the range of 0.2 to 3 mol per mol of the nickel salt. The reason for this is that if the supply amount of the aqueous ammonia is small, it is difficult for the particles to have a high density, while if the supply amount is too large, a large amount of nickel is dissolved in the solution as an ammine complex. As the ammonia source, ammonium sulfate or ammonium nitrate can be used in addition to the ammonia water.

In the method of the present invention, it is preferable to use NaOH or KOH as the alkali hydroxide supplied to the reaction vessel as a reaction solution. In particular, the amount of the alkali hydroxide to be added is a value measured by a pH meter, and indicates the pH of the reaction solution in the reaction tank.
Is desirably controlled to be constant at a target value ± 0.1 pH at a predetermined value within a range of 10.5-12.5.

In the present invention, further improvement in battery performance can be expected by adding salts such as Zn, Co, and Cd at the same time.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which nickel hydroxide is manufactured according to FIG. 1 will be described below. Example 1 (1) A 2 liter reaction vessel was charged with a 2 mol / l aqueous solution of nickel sulfate and 28% by weight of aqueous ammonia at 500 ml /
The reaction was carried out at a supply rate of hr and 60 ml / hr, and the production reaction of nickel hydroxide was started under stirring conditions while controlling the pH constantly with a 6 mol / l aqueous solution of sodium hydroxide. (2) Next, after the total liquid volume in the reaction tank reaches 1.5 liters, the reaction solution in the reaction tank is pumped at a constant speed of 240 ml / hr by a pump and supplied to a 400 ml capacity thickener.
The supernatant of the reaction solution was continuously overflowed and removed, and the production of nickel hydroxide was continued while returning only the concentrated slurry to the reaction tank at a rate of 120 ml / hr. (3) After 10 hours from the start of the reaction, when the slurry concentration in the reaction tank reached 600 g / l, the reaction was stopped, the slurry was taken out, filtered, washed and dried to obtain spherical nickel hydroxide. Particles were obtained.

The particle size distribution and tap density of the nickel hydroxide particles thus obtained were measured. As a result, the particle size distribution of the nickel hydroxide particles showed a fairly sharp distribution with an average particle size of 7 μm as shown in FIG. 2, while the tap density of the nickel hydroxide particles was 2.12 g / ml.

(Example 2) (1) The reaction for forming nickel hydroxide was started under the same conditions as in Example 1, and when the slurry concentration in the reaction tank reached 600 g / l, the solid-liquid separation device was started. A part (500 ml each) of the nickel hydroxide slurry to be supplied and concentrated is taken out every three hours, so that the slurry concentration in the reaction tank is 400 g / g.
The production of nickel hydroxide was continued at 1 to 600 g / l. (2) After 21 hours from the start of the reaction, the reaction was stopped, and the nickel hydroxide slurry sampled on the way was mixed.Then, the slurry was taken out, filtered, washed and dried to remove spherical nickel hydroxide particles. Obtained.

The particle size distribution and tap density of the nickel hydroxide particles thus obtained were measured. As a result, the particle size distribution of the nickel hydroxide particles showed a slightly broad distribution with an average particle size of 12 μm as shown in FIG. 3, while the tap density of the nickel hydroxide particles was 2.33 g / ml.

[0026]

As described above, according to the present invention, it is possible to produce a high-concentration nickel hydroxide slurry in a short time without stopping the supply of the reaction solution or stopping the stirring, and the relatively narrow particle size can be obtained. It is possible to efficiently produce spherical nickel hydroxide having a distribution and a high packing density. Moreover, by appropriately mixing the nickel hydroxide slurry taken out of the reaction system for controlling the slurry concentration in the reaction tank,
The particle size distribution of nickel hydroxide for increasing the packing density can be easily controlled.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a method for producing nickel hydroxide according to the present invention.

FIG. 2 is a diagram showing a particle size distribution of nickel hydroxide according to Example 1.

FIG. 3 is a diagram showing a particle size distribution of nickel hydroxide according to Example 2.

Claims (4)

[Claims] 1. A nickel salt aqueous solution, an aqueous ammonia solution and an aqueous alkali hydroxide solution are continuously supplied to a reaction tank at a constant rate to generate nickel hydroxide under agitation conditions. After the amount reaches a predetermined amount, a part of the reaction solution is pumped by a pump and supplied to a solid-liquid separator, and the medium liquid is continuously removed, and only the concentrated slurry is returned to the reaction tank again. A method for producing nickel hydroxide, wherein the liquid level in the reaction tank is kept constant. 2. A nickel salt aqueous solution, an aqueous ammonia solution and an aqueous alkali hydroxide solution are continuously supplied to the reaction tank at a constant rate so as to react and generate nickel hydroxide under stirring conditions. After the amount reaches a predetermined amount, a part of the reaction solution is pumped by a pump and supplied to a solid-liquid separator, and the medium liquid is continuously removed, and only the concentrated slurry is returned to the reaction tank again. By keeping the liquid level in the reaction tank constant, after the slurry concentration in the reaction tank reaches a predetermined concentration, a part of the nickel hydroxide slurry to be supplied to the solid-liquid separation device and concentrated is continuously or A method for producing nickel hydroxide, comprising intermittently taking out of a reaction system to control a slurry concentration in a reaction tank within a predetermined range. 3. The slurry concentration in the reaction tank is 200 to 800 g.
3. The method according to claim 2, wherein the control is performed in the range of / l. 4. Before the production of nickel hydroxide is completed,
The method according to claim 2, wherein the nickel hydroxide slurry taken out of the reaction system for controlling the slurry concentration in the reaction vessel is returned to the reaction vessel and mixed to control the particle size distribution of nickel hydroxide. The manufacturing method as described.