JPH11307092A - Nickel hydroxide powder for alkaline storage battery positive electrode active material and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide nickel hydroxide powder for an alkaline storage battery positive electrode active material together with its manufacturing method, having a filling characteristic close to the closest filling, accordingly, having large tapping density, and resultantly, capable of realizing improvement of an active material utilization factor and increase of alkaline storage battery capacity. SOLUTION: Nickel hydroxide powder for an alkaline storage battery positive electrode active material comprises, (a) first nickel hydroxide particles with surfaces covered with cobalt hydroxide or cobalt oxide, having an average particle size ranging from 1 to 5 μm, and having particle size distribution satisfying σ<0.8D50 , where the particle size distribution is regarded as a normal distribution, σ is a standard deviation, and D50 is an average particle diameter, and (b) second nickel hydroxide particles having an average particle size ranging from 10 to 30 μm and having particle size distribution satisfying σ<0.8D50 , where the particle size distribution is regarded as a normal distribution, σ is a standard deviation, and D50 is an average particle diameter, and tapping density thereof ranges from 2.0 to 3.0 g/cc.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a nickel hydroxide powder for a positive electrode active material of an alkaline storage battery and a method for producing the same.

[0002]

2. Description of the Related Art A positive electrode active material made of nickel hydroxide powder has been used as a positive electrode of alkaline storage batteries such as nickel-cadmium storage batteries and nickel-hydrogen storage batteries, and has conventionally been used in various electronic devices, for example, small devices such as mobile phones and personal computers. In recent years, it has been widely used as a large power supply for electric vehicles. Therefore, recently, there has been a strong demand for higher capacity of such an alkaline storage battery, and in particular, there has been a demand for an improvement in the utilization rate and tapping density of nickel hydroxide, which is a positive electrode active material. Improvements have been proposed.

As a method for improving the utilization rate of nickel hydroxide as an active material, a method has been proposed in which metallic cobalt or cobalt hydroxide is added to nickel hydroxide as a conductive agent. For example, cobalt hydroxide is oxidized to cobalt oxyhydroxide (CoOOH) during charging to form a conductive matrix, and as a result, conductivity between active materials is increased, and utilization can be improved. .

[0004] For example, Japanese Patent Application Laid-Open No. 7-22027 discloses that β-type cobalt hydroxide having a half-width of the peak on the (001) plane of 0.4 ° or more has high reactivity with an alkaline electrolyte. Therefore, it has been shown that by mixing such β-type cobalt hydroxide with nickel hydroxide, the utilization rate of the active material can be further improved as compared with the related art. However, in general, cobalt hydroxide, as a paste together with nickel hydroxide, tends to be ubiquitous in the paste when it is filled into a porous positive electrode substrate for holding the positive electrode active material, and thus, the effective material comprising the active material A difficult conductive network (net) is hardly formed.

[0005] Therefore, a method has been proposed in which the surface of nickel hydroxide or particles mainly composed of nickel hydroxide is coated with a cobalt compound. For example, JP-A-62-234867, JP-A-62-237667, JP-A-62-2
No. 22566 proposes to coat the surface of nickel hydroxide particles with α-type or β-type cobalt hydroxide.

[0006] In particular, Japanese Patent Application Laid-Open No. Hei 7-320737 discloses that an inner layer made of α-type cobalt hydroxide and an outer layer made of β-type cobalt hydroxide are coated with two layers of nickel hydroxide particles to form an unstable α-cobalt hydroxide. It has been proposed that by protecting the type cobalt hydroxide with a relatively stable β-type cobalt hydroxide, a dense conductive network is formed at the time of charging to improve the utilization rate of the active material.

As described above, various methods for coating nickel hydroxide particles with cobalt hydroxide have been proposed to increase the utilization of nickel hydroxide particles. Cobalt hydroxide is coated on nickel hydroxide particles having a diameter of about 10 μm, and in any case, it is necessary to mix a relatively large amount of cobalt hydroxide with nickel hydroxide. Therefore, conventionally, since the tapping density of the nickel hydroxide particles coated with cobalt hydroxide is still insufficient, the amount of the active material charged into the positive electrode substrate is relatively small, and the energy density of the electrode is low. In addition, there is a problem that the manufacturing cost of the electrode is increased.

In order to improve the tapping density of nickel hydroxide particles as an active material, JP-A-63-1
No. 6,555 discloses that the tapping density is increased by mixing two types of nickel hydroxide particles having different particle size distributions. However, according to this method, for the nickel hydroxide powder having a tapping density in the range of 1.70 to 1.85 g / cc, although the tapping density is increased by about 0.2 g / cc, the tapping density is not higher than 1 g / cc. For nickel hydroxide powder as large as around .95 g / cc, the increase in tapping density is less than 0.1 g / cc, and the improvement in tapping density is not satisfactory.

[0009]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned various problems in an active material for a positive electrode of an alkaline storage battery obtained by mixing cobalt metal or a cobalt compound with nickel hydroxide powder. And
It has a filling characteristic close to close packing, and therefore has a large tapping density, and as a result, it is possible to improve the utilization rate of the active material and realize a high capacity of the alkaline storage battery. An object of the present invention is to provide a nickel powder and a method for producing the same.

[0010]

The nickel hydroxide powder for an active material for a positive electrode of an alkaline storage battery according to the present invention has the following features. (A) The surface is coated with cobalt hydroxide or cobalt oxide, and has an average particle diameter of 1 to 5 μm. The first nickel hydroxide particles having a particle size distribution satisfying σ <0.8D ₅₀ when the standard deviation is σ and the average particle size is D ₅₀ by regarding the particle size distribution as a normal distribution. and (b) with an average particle size in the range of 10 to 30 [mu] m, and considers the particle size distribution and a normal distribution, the standard deviation sigma, when the average particle diameter and D _50, sigma satisfy <0.8D ₅₀ The second nickel hydroxide particles having such a particle size distribution, and the tapping density is in the range of 2.0 to 3.0 g / cc.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, the first and second nickel hydroxide particles may be composed only of nickel hydroxide, or may be composed mainly of nickel hydroxide. The one containing nickel hydroxide as a main component means that at least one element selected from cobalt, zinc, cadmium, magnesium, calcium and manganese is 1 to 10% by weight in terms of metal with respect to nickel hydroxide. It is included in the range. Such a particle whose main component is nickel hydroxide is prepared, for example, by preparing an aqueous solution containing a water-soluble salt of the above element together with a water-soluble nickel salt, adding an alkali thereto, and coprecipitating, for example, , Nickel hydroxide containing required elements such as cobalt and zinc can be obtained.

According to the present invention, the first nickel hydroxide particles (hereinafter sometimes referred to as fine particles of nickel hydroxide) have an average particle size in the range of 1 to 5 μm and a particle size distribution of is regarded as a normal distribution, the standard deviation sigma, when the average particle diameter and D _50, sigma <a narrow particle size distribution that satisfies 0.8D _50, with cobalt or cobalt oxide hydroxide is coated on the surface I have. The cobalt hydroxide may be any of α-type cobalt hydroxide and β-type cobalt hydroxide, and the inner layer is made of α-type cobalt hydroxide,
The outer layer may have a two-layer structure made of β-type cobalt hydroxide.

However, the coating amount of the cobalt hydroxide or cobalt oxide is preferably in the range of 1 to 20% by weight based on nickel hydroxide as metal cobalt.
In particular, the content is preferably in the range of 2 to 10% by weight. When the coating amount of cobalt hydroxide or cobalt oxide is less than 1% by weight based on nickel hydroxide as metal cobalt, use of the active material by coating nickel hydroxide particles with cobalt hydroxide or cobalt oxide. When it is not possible to achieve the improvement of the ratio, when it exceeds 20% by weight, the filling amount of the active material into the positive electrode substrate is relatively small,
The energy density of the electrode is small. In addition, the manufacturing cost of the electrode is increased.

According to the present invention, by mixing the first nickel hydroxide particles having such a fine and narrow particle size distribution with the second nickel hydroxide particles having a large average particle size and a narrow particle size distribution, a mixture is obtained. The packing property of the powder is close to the closest packing to increase the tapping density. Therefore, according to the present invention, the second nickel hydroxide particles
The average particle size is in the range of 10 to 30 μm, preferably in the range of 10 to 25 μm, and the particle size distribution is regarded as a normal distribution, the standard deviation is σ, and the average particle size is D.
When _50, having a narrow particle size distribution which satisfies sigma <0.8D _50.

Further, according to the present invention, the mixing ratio of the first nickel hydroxide particles and the second nickel hydroxide particles is
It is preferable that the second nickel hydroxide particles be 95 to 60% by weight with respect to the first nickel hydroxide particles 5 to 40% by weight, and in particular, the first nickel hydroxide particles 10 to 35%.
% Of the second nickel hydroxide particles 90 to 65% by weight.
% By weight.

According to the present invention, if necessary, the surface of the second nickel hydroxide particles may be coated with cobalt hydroxide or oxide in the range of 1 to 20% by weight based on nickel hydroxide as metal cobalt. Cobalt may be coated.

As described above, according to the present invention, the first and second nickel hydroxide particles each have the above-mentioned average particle diameter and have a narrow particle size distribution. It is possible to obtain a nickel hydroxide powder having a packing property close to close packing, and thus having a high tapping density.

The nickel hydroxide powder according to the present invention comprises a first step of producing the first or second nickel hydroxide particles having the above average particle diameter, and a step of removing the obtained nickel hydroxide fine particles from water. And a second step of coating with cobalt oxide or cobalt oxide.

That is, in the first step, an aqueous solution of a water-soluble nickel salt, an aqueous solution of an ammonium ion donor, and an aqueous solution of an alkali metal hydroxide are mixed with a p
By continuously supplying H to the reaction tank while keeping H constant, nickel hydroxide particles can be generated. Here, by adjusting the pH and reaction time of the obtained mixed solution, the first nickel hydroxide particles having an average particle diameter of 1 to 5 μm and the second nickel hydroxide particles having an average particle diameter of 10 to 30 μm are adjusted.
Can easily be obtained. The nickel hydroxide thus obtained is taken out of the reaction tank, and the first nickel hydroxide particles are subjected to the second stage.

Examples of the water-soluble nickel salt include nickel sulfate, nickel chloride and nickel nitrate. Examples of the aqueous ammonium ion donor solution include aqueous ammonia, ammonium chloride and ammonium sulfate. Further, examples of the alkali metal hydroxide include sodium hydroxide, potassium hydroxide, lithium hydroxide and the like.

In the second step, the first nickel hydroxide particles obtained as described above are made into a slurry, and an aqueous solution of a water-soluble cobalt salt, an aqueous solution of an ammonium ion donor, and an aqueous solution of an alkali hydroxide are added to the slurry. The first nickel hydroxide particles coated with cobalt hydroxide can be continuously supplied to obtain the first nickel hydroxide particles.

Here, examples of the water-soluble cobalt salt include cobalt sulfate, cobalt chloride, and cobalt nitrate. The same thing as the above can be mentioned as an ammonium ion supplier and an alkali hydroxide.

In the second step, the coating amount of the cobalt hydroxide or the cobalt oxide on the first nickel hydroxide particles is appropriately determined depending on the amount of the cobalt salt added to the slurry of the first nickel hydroxide particles. Can be adjusted. Usually, the amount of cobalt calculated from the cobalt salt added to the slurry of the first nickel hydroxide particles can be used as the coating amount on the nickel hydroxide particles.

[0024]

EXAMPLES The present invention will be described below with reference to examples.
The present invention is not limited by these examples.

Example 1 (Production of Second Nickel Hydroxide Particles) As a first stage reaction, a reaction vessel with a stirrer having a capacity of 10 L was stirred at a temperature of 50 ° C. while maintaining a temperature of 50 ° C. while having a concentration of 250 g / L. A mixed aqueous solution containing nickel sulfate, 4.0 g / L cobalt sulfate and 11.8 g / L zinc sulfate and 13% by weight ammonia water are continuously supplied, and the pH of the mixed solution is maintained at 12.0. As a result, a 28% by weight aqueous solution of sodium hydroxide is intermittently added to the reaction vessel, and cobalt as metal cobalt is 1.5% by weight.
And second nickel hydroxide particles having an average particle diameter of 13.3 μm and a tapping density of 2.15 g / cc in which 4.5% by weight of zinc was dissolved as zinc metal were obtained.

FIG. 1 shows a scanning electron micrograph of the nickel hydroxide particles, and FIG. 4 shows a particle size distribution diagram. When considering the particle size distribution of the nickel hydroxide particles as a normal distribution,
The standard deviation σ is 5.5, which is smaller than 0.8D ₅₀ (= 10.6).

(Production of First Nickel Hydroxide Particles)
As a step reaction, while maintaining the temperature at 50 ° C. with stirring in a 10 L reaction vessel equipped with a stirrer, nickel sulfate having a concentration of 250 g / L, 4.0 g / L cobalt sulfate and 11.8 g / L were used.
L of zinc sulfate and 13% by weight of aqueous ammonia are continuously supplied. At this time, a 28% by weight aqueous solution of sodium hydroxide is intermittently reacted so as to maintain the pH of the mixture at 12.3. In addition to the tank, 1.5% by weight of cobalt as metallic cobalt and 4.5% by weight of zinc as metallic zinc were dissolved in an average particle diameter of 2.6 μm and a tapping density of 1.80 g / cc.
To obtain nickel hydroxide particles.

FIG. 2 shows a scanning electron micrograph of the nickel hydroxide particles, and FIG. 5 shows a particle size distribution diagram. When considering the particle size distribution of the nickel hydroxide particles as a normal distribution,
The standard deviation σ is 1.2, which is smaller than 0.8D ₅₀ (= 2.1).

After filtering and washing the nickel hydroxide particles, the nickel hydroxide particles were charged into a 5 L reaction tank to form a slurry. As a reaction in the second step, the pH of the mixed solution was adjusted to 12.2 while continuously supplying a 200 g / L aqueous solution of cobalt sulfate and 13% by weight ammonia water to the slurry with stirring.
0 wt% sodium hydroxide aqueous solution is added intermittently so as to maintain the water content at 0%. When the cobalt content reaches 4 wt% with respect to the first nickel hydroxide particles, the aqueous solution of cobalt sulfate, ammonia water and water are added. The supply of the aqueous sodium oxide solution to the reaction tank was stopped, and thereafter, stirring was further continued for 20 minutes. Thereafter, the solid content was filtered, washed with water and dried, and the first metal coated with 4% by weight of cobalt hydroxide as metal cobalt was used.
To obtain nickel hydroxide particles.

(Production of nickel hydroxide powder for positive electrode active material of alkaline storage battery) 80 parts by weight of the first nickel hydroxide particles and 20 parts by weight of the second nickel hydroxide particles were mixed. The obtained mixed powder had an average particle diameter of 11.3 μm and a tapping density of 2.35 g / cc. FIG. 3 shows a scanning electron micrograph of this mixed powder, and FIG. 6 shows a particle size distribution diagram.

Example 2 (Production of second nickel hydroxide particles) In the same manner as in Example 1, an average of 1.5% by weight of cobalt as metal cobalt and 4.5% by weight of zinc as metal zinc was dissolved. Particle size 22.7
Second nickel hydroxide particles having a thickness of 0 μm and a tapping density of 2.08 g / cc were obtained. When the particle size distribution of the nickel hydroxide particles is regarded as a normal distribution, the standard deviation σ is 9.3, which is smaller than 0.8D ₅₀ (= 18.2).

Further, in the same manner as in Example 1,
1.5% by weight of cobalt as zinc and zinc as zinc metal
4.5 wt% solid solution average particle size 12.50 μm, tapping
Nickel hydroxide particles having a density of 2.05 g / cc were obtained.
Was. The nickel hydroxide particles have a regular distribution of the particle size distribution.
When considered as cloth, the standard deviation σ is 5.3 and 0.8D ₅₀
(= 10.0).

(Production of First Nickel Hydroxide Particles)
As a step reaction, while maintaining the temperature at 50 ° C. with stirring in a 10 L reaction vessel equipped with a stirrer, nickel sulfate having a concentration of 250 g / L, 4.0 g / L cobalt sulfate and 11.8 g / L were used.
L of zinc sulfate and 13% by weight of aqueous ammonia are continuously supplied. At this time, a 28% by weight aqueous solution of sodium hydroxide is intermittently reacted so as to maintain the pH of the mixture at 12.3. In addition to the tank, 1.5% by weight of cobalt as metallic cobalt and 4.5% by weight of zinc as metallic zinc were solid-solved, having an average particle size of 3.71 μm and a tapping density of 1.68 g / c.
Thus, nickel hydroxide particles (c) were obtained. When the particle size distribution of the nickel hydroxide particles is regarded as a normal distribution, the standard deviation σ is 1.6, which is smaller than 0.8D ₅₀ (= 2.97).

After the nickel hydroxide particles were filtered and washed with water, they were charged into a 5 L reaction tank to form a slurry. As a reaction in the second step, the pH of the mixed solution was adjusted to 12.2 while continuously supplying an aqueous solution of cobalt sulfate having a concentration of 250 g / L and aqueous ammonia of 13% by weight to the slurry with stirring.
0 wt% sodium hydroxide aqueous solution is added intermittently so as to maintain 0 wt%, and when the amount of cobalt reaches 4 wt% with respect to the first nickel hydroxide particles, aqueous cobalt sulfate solution, aqueous ammonia and water are added. The supply of the aqueous sodium oxide solution to the reaction tank was stopped to terminate the reaction. After the reaction is over,
Stirring was continued for 20 minutes. After this, the solid is filtered, washed with water,
After drying, first nickel hydroxide particles coated with 4% by weight of cobalt hydroxide as metal cobalt were obtained.

(Production of Nickel Hydroxide Powder for Cathode Active Material of Alkaline Storage Battery)
And nickel hydroxide particles in the ratio shown in Table 1,
About the obtained mixed powder, the average particle diameter and the tapping density were measured. Table 1 shows the results.

[0036]

[Table 1]

[0037]

As described above, according to the present invention, the fine first nickel hydroxide particles having an average particle diameter in the range of 1 to 5 μm and having a narrow desired particle size distribution and the average particle diameter Is in the range of 10 to 30 μm, and by mixing the second nickel hydroxide particles having an intended narrow particle size distribution at a predetermined ratio, to bring the packing characteristics of the mixture of these particles closer to the closest packing. Thus, the tapping density can be greatly increased. That is,
According to the present invention, the tapping density is usually 2.0 to 3.0 g.
/ Cc of nickel hydroxide powder can be obtained. Therefore, according to the nickel hydroxide powder of the present invention, the amount of the active material per unit volume of the positive electrode substrate can be increased, and as a result, the capacity of the alkaline storage battery can be increased.

Further, according to the present invention, fine first nickel hydroxide particles coated with cobalt hydroxide or cobalt oxide are arranged around second nickel hydroxide particles having a large average particle diameter. It is possible to enhance the formation of the conductive network and increase the utilization rate of the active material,
Moreover, since only the first nickel hydroxide particles are coated with cobalt hydroxide or cobalt oxide, the amount of cobalt used can be reduced, and the manufacturing cost of the electrode can be reduced.

[Brief description of the drawings]

FIG. 1 is a scanning electron micrograph of the second nickel hydroxide particles obtained in Example 1.

FIG. 2 is a scanning electron micrograph of fine nickel hydroxide particles before coating with cobalt hydroxide obtained in Example 1.

FIG. 3 is a scanning electron micrograph of the nickel hydroxide powder according to the present invention obtained in Example 1.

FIG. 4 is a particle size distribution diagram of the second nickel hydroxide particles shown in FIG.

FIG. 5 is a particle size distribution diagram of the fine nickel hydroxide particles shown in FIG.

FIG. 6 is a particle size distribution diagram of the nickel hydroxide powder according to the present invention shown in FIG.

Continued on the front page (72) Inventor Yasuhiro Okamoto 5-1 Ebisshima-cho, Sakai City, Osaka Sakai Chemical Industry Co., Ltd. Sakai Works Co., Ltd. (72) Inventor Hiroshi Tokunaga 5-1-1 Ebisshima-cho, Sakai City, Osaka Stock Sakai Chemical Co., Ltd. Company Sakai Office

Claims (4)

[Claims] (1) The surface is coated with cobalt hydroxide or cobalt oxide, has an average particle size in the range of 1 to 5 μm, and its particle size distribution is regarded as a normal distribution. when the average particle diameter and D _50, sigma <0.8D
The first nickel hydroxide particles having a particle size distribution satisfying ₅₀ and (b) the average particle size is in the range of 10 to 30 μm, and the particle size distribution is regarded as a normal distribution, the standard deviation is σ, the average particle size is when the diameter and D _50, sigma <consists of a second nickel hydroxide particles having a particle size distribution satisfying the 0.8D _50, alkali tapping density is in the range of 2.0 to 3.0 g / cc Nickel hydroxide powder for storage battery positive electrode active material. 2. The nickel hydroxide according to claim 1, wherein the coating amount of the cobalt hydroxide or the cobalt oxide in the first nickel hydroxide particles is in the range of 1 to 20% by weight based on the nickel hydroxide as the metal cobalt. Powder. 3. 5% to 40% by weight of first nickel hydroxide particles
3. The nickel hydroxide powder according to claim 1, comprising 95 to 60% by weight of the second nickel hydroxide particles. 4. The method according to claim 1, wherein the first nickel hydroxide and / or the second nickel hydroxide is at least one selected from cobalt, zinc, cadmium, magnesium, calcium and manganese in terms of metal with respect to nickel hydroxide. , 1-1
The nickel hydroxide powder according to any one of claims 1 to 3, which is contained in a range of 0% by weight.