JPH08203522A - Nickel active substance for alkaline battery and manufacture thereof - Google Patents

Abstract

PURPOSE: To provide nickel active substance for an alkaline battery and manufacturing method thereof which can enhance electrode capacity by allowing cobalt compound to sufficiently exhibit its function in a nickel hydroxide active material with which the cobalt compound is compounded. CONSTITUTION: A nickel active substance for an alkaline battery is such one in which a part or the whole of the surfaces of basic particles including nickel hydroxide as its main component is covered with metallic compound including at least cobalt hydroxide. This nickel active substance has its average particle diameter caused by laser diffraction method set to 3μm or more and less than 20μm.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nickel hydroxide active material for alkaline storage batteries, and more particularly to a nickel hydroxide active material in which the surface of nickel hydroxide particles is coated with an electronically conductive metal compound.

[0002]

2. Description of the Related Art Conventionally, a so-called sinter type substrate obtained by sintering nickel powder has been mainly used as a substrate of a positive electrode for an alkaline storage battery. In recent years, a non-sintered foamed nickel substrate or the like has been used because the work of filling the substance is complicated.

However, in a high-porosity substrate such as a foamed nickel substrate, a part of the filled active material cannot directly contact the current collector because of its large pore size. In other words, since the non-sintered substrate can be packed at a higher density than the sintered substrate, it is advantageous in terms of higher energy density and improved filling workability, but the relative ratio between the active material and the substrate is high. Since the contact area becomes smaller, the proportion of active material that cannot contribute to the electrode reaction increases.
Therefore, there is a drawback that the utilization rate of the active material is deteriorated.

For the purpose of remedying this drawback, a technique of adding conductive powder or cobalt compound powder to an active material (Japanese Patent Laid-Open No. 53-41449) and further development of this technique, metal nickel powder ( A technique for forming a metal cobalt layer or a trivalent or higher valent cobalt compound layer on the surface of a conductive powder) or a technique for forming an oxide layer of cobalt and nickel on the surface of a metal nickel powder (JP-A-59-1).
8572, JP-A-59-138064, JP-A-1-107453) and the like have been proposed.

When these techniques are used, the conductivity between the active material particles is increased, so that the utilization rate of the active material is improved. However, in order to sufficiently enhance the utilization rate of the active material, a considerable amount relative to nickel hydroxide is used. It is necessary to add the metal compound. However, if the amount of the metal compound added is increased, the content of nickel hydroxide that directly contributes to the electrode reaction is correspondingly reduced, so that the energy density of the active material is reduced.

Therefore, although the above-mentioned conventional technique can improve the utilization rate of the active material, it has a problem that it does not sufficiently lead to the improvement of the electrode capacity.

[0007]

The present invention has been made in order to solve such conflicting technical problems, and it is possible to obtain an active material excellent in conductivity by adding a smaller amount of a cobalt compound. The present invention aims to provide a method for obtaining the nickel active material for an alkaline storage battery, which can remarkably increase both the utilization rate of the active material and the electrode capacity.

[0008]

In order to achieve the above object, the present invention is configured as follows. The invention according to claim 1 is a nickel active material for an alkaline storage battery, wherein a part or all of the surface of the mother particles containing nickel hydroxide as a main component is coated with a metal compound containing at least cobalt hydroxide. The nickel active material is characterized in that the average particle diameter by the laser diffraction method is 3 μm or more and 20 μm or less.

According to a second aspect of the present invention, in the nickel active material for alkaline storage batteries according to the first aspect, the metal compound further contains a lithium compound. According to a third aspect of the present invention, in the nickel active material for alkaline storage batteries according to the first and second aspects, the content of the metal compound is 1% by weight or more and 15% by weight or less based on the mother particles.

According to a fourth aspect of the present invention, in the nickel active material for alkaline storage batteries according to the first to third aspects, the cobalt hydroxide is a higher cobalt hydroxide having a valency higher than 2. To do. According to a fifth aspect of the present invention, mother particles containing nickel hydroxide as a main component having an average particle size of 1 μm or more and less than 20 μm are dispersed in a metal salt solution containing at least a cobalt salt, and then the mother particles are dispersed. The pH of the metal salt solution thus prepared is adjusted with an alkaline solution to deposit at least a cobalt hydroxide precipitate with the mother particles as nuclei, and a coating layer containing a predetermined amount of cobalt hydroxide on the surface of the mother particles. Is formed to prepare a nickel active material having an average particle diameter of 3 μm or more and 20 μm or less by a laser diffraction method, which is a method for producing a nickel active material for an alkaline storage battery.

According to a sixth aspect of the present invention, in the method for producing a nickel active material for an alkaline storage battery according to the fifth aspect, the coating layer containing the predetermined amount of cobalt hydroxide is 1% by weight or more based on the base particles. 15% by weight or less. The invention according to claim 7 is the method for producing a nickel active material for an alkaline storage battery according to claims 5 to 6, wherein after forming a coating layer having at least cobalt hydroxide, the coated particles are impregnated with an alkali metal solution. ,
The heat treatment is performed in the presence of oxygen.

The invention according to claim 8 is the method for producing a nickel active material for an alkaline storage battery according to claim 7, wherein the alkali metal concentration of the alkali metal solution is 15% by weight.
As described above, the content is 40% by weight or less. The invention according to claim 9 is the method for producing a nickel active material for an alkaline storage battery according to claims 7 to 8, characterized in that the alkali metal solution further contains lithium ions.

The invention according to a tenth aspect is the seventh to ninth aspects.
In the method for producing a nickel active material for an alkaline storage battery described above, the temperature of the heat treatment is 50 ° C. or higher and 150 ° C. or lower.

[0014]

[Action]

(1) In the nickel active material for an alkaline storage battery according to the present invention, a part or all of the surface of the mother particles containing nickel hydroxide as a main component is coated with a metal compound containing at least cobalt hydroxide, and The average particle size of the coated active material by the laser diffraction method is specified to be 3 μm or more and 20 μm or less.

With the coated active material particles having a particle diameter in this range, the porous electrode substrate can be easily filled, and the filled active material particles can surely come into contact with each other. The active material particles are brought into contact with each other through the coating layer of cobalt hydroxide having good conductivity. Therefore, it is possible to form a good conductive network in the electrode by the mutual active material particles. In addition, the particles having this size increase the contact area between the particles,
Since the effect of forming the cobalt hydroxide coating layer on the surface of the mother particles that are the active material main body is remarkably exhibited, it is possible to form a good conductive network with a smaller amount of cobalt hydroxide.

That is, according to the present invention, the coating layer is provided by minimizing the negative factor that the nickel hydroxide content is relatively reduced by providing the coating layer and the energy density of the active material is lowered. Since a positive factor (improvement in conductivity) due to this can be effectively taken out, improvement in utilization rate of the active material leads to improvement in electrode capacity. According to the present invention, the following effects are further enhanced by adding the following configuration.

That is, the coating layer is preferably a metal compound containing a cobalt hydroxide and a lithium compound. In this case, since lithium in the coating layer is in the vicinity of nickel hydroxide and acts effectively, overdischarge characteristics of the electrode are significantly improved. The coating layer made of the metal compound is preferably 1% by weight or more and 15% by weight or less based on the nickel hydroxide mother particles. This is because, when a coating layer is formed on the surface of nickel hydroxide, the content of nickel hydroxide is reduced by the amount of the coating layer when viewed per unit weight of active material, and the energy density of the active material (capacity per unit weight of active material is reduced. ) Is decreased, but when the amount of the coating layer is in the above range, the effect of improving the utilization factor of the coating layer exceeds the reduction of the nickel hydroxide content, and thus the energy density is not substantially reduced.

Further, the cobalt hydroxide in the coating layer is preferably a hydroxide of higher cobalt having a valence of more than two. When it is a higher cobalt hydroxide having a valence of more than 2, the conductivity of the coating layer is further increased, the utilization factor of the active material is further improved, and the electrode capacity is increased. (2) In the method for producing a nickel active material for an alkaline storage battery according to the present invention, mother particles having a particle size of 1 μm or more and less than 20 μm are dispersed in a solution in which at least a cobalt salt is dissolved, and pH of the solution is adjusted with alkali. By doing
A method of depositing a cobalt hydroxide precipitate by using the mother particles as nuclei to coat the mother particles was adopted.

According to this method, it is possible to deposit the cobalt hydroxide precipitate so as to surround the mother particle with the mother particle as the nucleus, and moreover, the concentration of the cobalt salt solution and the solution P
By controlling H, temperature, etc., the amount and state of coating can be easily adjusted. Therefore, if the thickness of the coating layer (which can be converted by the coating amount) is set in advance and the mother particles having a particle diameter obtained by subtracting this thickness from the desired active material particle diameter are dispersed in the cobalt salt solution, the coating activity of the desired particle diameter can be obtained. Since substance particles are obtained, the average particle diameter by the laser diffraction method is 3 μm to 20 μm.
The nickel active material of m can be produced with good yield.

The production method of the present invention as described above preferably has the following structure. That is, the amount of cobalt hydroxide coated on the mother particles is 1 to 1 with respect to the mother particles.
It is preferable to carry out so as to be 5% by weight. After the coating step is completed, it is preferable to subject the coated particles to an alkali heat treatment of impregnating with an alkali metal solution and heating and drying in the presence of oxygen. When the coated particles are subjected to an alkali heat treatment, the cobalt compound in the coating layer changes to a higher-order cobalt compound having excellent conductivity, and the microstructure of the coating layer can be changed to a structure in which the electrolytic solution easily penetrates. it can. Therefore, an active material having a higher utilization rate can be obtained.

Further, this alkali heat treatment is carried out for 15 to 40
Using an alkali metal solution having a concentration by weight of 50 to 150 ° C.
It is better to carry out at the heating temperature of 1, and more preferably to carry out the impregnation treatment with an alkali metal solution containing lithium ions. When lithium ions are added to the alkali metal solution to form a lithium-containing coating layer, the utilization rate of the coated active material particles and the overdischarge characteristics can be enhanced very easily. The reason for this is that if lithium ions are present in the vicinity of the surface of nickel hydroxide (base particles), they can act to enhance the over-discharge characteristics most quantitatively and efficiently.

[0022]

EXAMPLES The contents of the present invention will be clarified below based on experiments. The experiment is to produce various nickel active materials, produce various electrodes using these nickel active materials, and compare the performances of these electrodes. In the following, first, an outline of the method for producing the nickel active material and the method for producing the electrode will be described, and then the details of each experiment will be described.

[Preparation of Ni Active Material Coated with Cobalt Hydroxide]
First, add 25% to a nickel sulfate solution with a specific gravity of about 1.33.
A nickel hydroxide mother particle was prepared by a method of gradually adding a sodium hydroxide aqueous solution of wt%, adjusting the pH of this solution to a predetermined PH value with ammonia water, and precipitating nickel hydroxide. In this method, the particle size of nickel hydroxide precipitated from the solution can be changed by adjusting the concentration of nickel sulfate, the amount of sodium hydroxide added, the solution PH, and the solution temperature. Therefore, the reaction temperature is about 50
The nickel hydroxide particles having different particle diameters were prepared by a method of changing the pH mainly within the range of 10 to PH14 at 0 ° C. The deposited nickel hydroxide was thoroughly washed with water and then dried.

With respect to the seven kinds of particles thus produced, a laser diffraction method (Microtrac particle size analyzer;
Leads & Northrup) to measure the average particle size of about 0.6, 2.6, 5.5, 8.4 and 1, respectively.
It was 7.4, 19.1 and 22.5 μm. Hereinafter, these particles are referred to as Ni active material mother particles. Next, about 4 times the amount of water was added to 1 weight of the above Ni active material mother particles, and mixed and dispersed, and the specific gravity of this dispersion (slurry state) was adjusted while maintaining the pH at 10 with sodium hydroxide solution. The cobalt sulfate solution of 1.30 was added dropwise to coat the surface of the Ni active material mother particles with cobalt hydroxide. The coated particles were washed with water and dried to obtain cobalt hydroxide-coated Ni active material particles.

Here, the particle size of the cobalt hydroxide-coated Ni active material particles is determined by the particle size of the Ni active material mother particles and the thickness of the coating layer, and the thickness of the coating layer (which can be grasped by the coating amount) is It can be adjusted by adjusting the concentration or dropping amount of the cobalt sulfate solution. Therefore, in the above, various cobalt hydroxide-coated Ni active material particles shown in Table 1 were produced by the method of adjusting the dropping amount of the cobalt sulfate solution by using each of the above 7 types of Ni active material mother particles.

The method of coating the Ni active material particles in the solution in this manner is called a deposition coating method. [Preparation of Cobalt Hydroxide Simple Mixed Ni Active Material] 7.5 wt% of cobalt hydroxide powder having an average particle size of about 1 μm was added to the Ni active material mother particles having an average particle size of about 8.4 μm prepared above and mixed. As a result, a cobalt hydroxide simple mixed Ni active material was produced. This manufacturing method is called a simple mixing method.

[Preparation of Higher Cobalt-Coated Ni Active Material] (1) The cobalt hydroxide-coated Ni active material particles prepared above are impregnated with an alkaline solution to such an extent that the particles are wet, and dried by heating in the presence of oxygen. By the method described above, the cobalt hydroxide on the surface of the Ni active material particles was changed to a higher cobalt compound having a valence of more than 2. Detailed conditions of the higher-order treatment will be described in Experiment 2, Experiment 4, and Experiment 5 described below, respectively.

Hereinafter, such a higher-order method is referred to as an alkali heat treatment method, and the coating N treated by this alkali heat treatment method is used.
The i active material is referred to as a higher cobalt-coated Ni active material. (2) A high-order cobalt-coated Ni active material containing lithium ions was prepared in the same manner as in the alkaline heat treatment method except that an alkaline aqueous solution containing 0.7 molar concentration of lithium ions was used.

[Production of Nickel Electrode] Various nickel active materials produced above were mixed with a 0.2% by weight aqueous solution of hydroxypropylcellulose at a weight ratio of 1: 1 to prepare an active material slurry. This active material slurry was prepared to have a porosity of 95%,
Various nickel electrodes were prepared by a method in which foamed nickel having a thickness of 1.6 mm was filled, dried and then rolled to a thickness of 0.60 mm.

Table 1 shows a list of various Ni active materials produced as described above.

[0031]

[Table 1] [Experimental Part] A simple open cell was prepared from the various nickel electrodes prepared above, a nickel plate as a counter electrode, and a potassium hydroxide aqueous solution of about 25% by weight. The active material utilization rate and the electric capacity per unit active material weight were examined. The theoretical capacity of the nickel electrode used in the simple cell is 360 mA.

On the other hand, the nickel electrodes B ₁ to
Regarding B ₅ and E, a nickel-hydrogen battery having a nominal capacity of 1200 mAh was prepared by a known method using these electrodes, a hydrogen storage alloy electrode, and an electrolyte solution containing 7 to 8.5 N potassium hydroxide as a main component. The over-discharge characteristics of No. 3 were investigated (Experiments 3 and 6). The active material utilization rate and the electric capacity per unit active material weight were 12 mA until the discharge end voltage became −0.8 V with respect to the nickel plate after continuously filling at 36 mA for 24 hours.
The discharge capacity was measured under the condition that the battery was discharged at 0 mA, and the discharge capacity was calculated according to the numbers 1 and 2 below.

[0033]

[Equation 1]

[0034]

[Equation 2] The overdischarge characteristics were measured under the following conditions. 1) Charge the battery at 1200mA, stop charging when the battery voltage reaches a maximum and then decrease by 10mV (-ΔV),
Pause for 1 hour.

2) After resting for 1 hour, discharge at 1200 mA until the discharge end voltage becomes 1.0V. 3) After the discharge, the battery is forcibly discharged at 60 mA for 16 hours. 4) After repeating the steps 1) to 3) for 10 cycles, the steps 1) to 2) are further repeated for 5 cycles. The discharge capacity in the first cycle and the discharge capacity after the end of the final cycle were measured, and the ratio was defined as the overdischarge characteristic.

Each measured value was compared and examined by an index when a reference active material was defined and the utilization rate of this active material was set to 100. (Experiment 1) In Experiment 1, A _{1 to} A ₇ were used to examine the relationship between the average particle diameter of the Ni active material and the active material utilization rate.

The results are shown in FIG. In addition, in FIG.
A_FourThe utilization rate of is shown as 100, and the broken line
Ni active material obtained by simply mixing cobalt and nickel hydroxide
The utilization index of (S) is shown. In FIG. 1, the average particle size is
Coated Ni active material particles in the range of 3 to 20 μm (A ₂~
A₆) Has a higher utilization rate than the simple mixed Ni active material (S).
Indicates the utilization rate. Further, the diameter of the coated Ni active material particles is 6
Higher utilization rate (over 97%) in the range of ~ 18μm
However, if it goes out of this range, the usage rate will gradually decrease.
It becomes. From this result, the coated Ni produced by the deposition coating method
The particle size of the active material is preferably 3 to 20 μm,
It can be seen that it is more preferably 6 to 18 μm.

The particle size of the nickel hydroxide mother particles is 6 μm.
When it is less than m, the reason why the tendency of decrease in the utilization rate becomes large is not clear, but when it exceeds 18 μm, the decrease in utilization rate becomes large because the contact area between the particles decreases as a result It is considered that this is because the conductivity is deteriorated. (Experiment 2) In Experiment 2, A ₄ , B ₃ , and S were used, and the relationship between the presence or absence of alkali heat treatment and the utilization rate was examined. The result is
Table 2 shows the utilization rate of A ₄ as 100.

[0039]

[Table 2] However, the alkaline heat treatment of B ₃ uses a 25 wt% sodium hydroxide aqueous solution as an alkaline solution, and the heating temperature is 1
It was performed under the condition of drying at 00 ° C. The particle size of the mother particles and the amount of cobalt hydroxide are the same for A ₄ , B ₃ , and S (see Table 1).

The following can be seen from Table 2. A ₄ deposited coating cobalt hydroxide compares the simple mixing Ni active materials S which are simply mixed with nickel hydroxide and cobalt hydroxide, it is highly significant utilization of the active material, B ₃ rather than the A ₄ Furthermore, the utilization rate is high. From this, it is understood that the utilization rate of the active material can be further increased by performing the alkali heat treatment.

(Experiment 3) In Experiment 3, B _{1 to} B ₅ produced by the deposition coating method were used to examine the relationship between the coating amount of the higher order cobalt compound and the electric capacity per unit weight of the active material. The results are shown in FIG. 2 with B ₃ as 100. In FIG. 2, when the amount of the high order cobalt compound is less than 1% by weight and exceeds 15% by weight, the electric capacity index per unit weight of the active material is greatly reduced. From this, the higher cobalt compound coating amount is 1 to 15 with respect to the Ni active material mother particles.
It can be seen that it is preferably in weight%.

In FIG. 2, the reason why the volume index per unit weight of the active material was drastically decreased when the high-order cobalt compound coating amount was less than 1% by weight was that the high-order cobalt compound coating amount was less than 1% by weight. It is considered that the high-order cobalt compound is insufficient and the surface of the mother particle cannot be sufficiently covered, resulting in insufficient conductivity between the Ni active materials. On the other hand, when the amount of higher cobalt compound exceeds 15% by weight, the capacity index per unit weight of active material decreases sharply.
It is considered that the capacity decrease due to the relative decrease in the amount of nickel hydroxide in the Ni active material was larger than the capacity increasing effect due to the higher cobalt compound coating.

(Experiment 4) In Experiment 4, C _{1 to} C ₄ and B ₃ produced by the deposition coating method were used to examine the relationship between the concentration of the alkaline solution and the utilization rate in the alkaline heat treatment. In addition,
A 15 to 45 wt% sodium hydroxide aqueous solution was used as the alkaline solution, the heating temperature was 100 ° C. in common, and the other conditions are as shown in Table 1.

The experimental results are shown in FIG. 3 with the utilization rate of B ₃ being 100. As can be seen from FIG. 3, the utilization index significantly decreased when the alkali metal concentration was less than 15% by weight and more than 40% by weight. The reason for this is considered as follows. When the cobalt hydroxide-coated Ni active material particles are heat-treated in the presence of an alkali, the cobalt hydroxide on the particle surface changes to a compound of cobalt having a valence of more than 2,
The conductivity of the coating layer is increased. As a result, a conductive network between the active material particles is formed, and the utilization rate as a whole is improved. However, if the alkali metal concentration is less than 15% by weight, the solubility of cobalt hydroxide is lowered, and the cobalt hydroxide is unlikely to be converted into a higher-order cobalt compound having good conductivity by heat treatment. Therefore, it is considered that the utilization rate did not improve sufficiently. On the other hand, it is considered that when the alkali metal concentration exceeds 40% by weight, the solution viscosity remarkably increases, and it becomes difficult for the alkali solution to permeate into the coating layer, resulting in nonuniform homogenization reaction.

From the above, the concentration of the alkaline solution is
It is preferably in the range of 15 to 40% by weight. It has been confirmed that the same results as above can be obtained even when other alkali species such as potassium hydroxide is used as the alkali instead of sodium hydroxide.

(Experiment 5) In Experiment 5, using D _{1 to} D ₄ and B ₃ produced by the deposition coating method, the heating temperature was changed and the relationship between the heating temperature and the utilization factor in the alkaline heat treatment was investigated. The detailed conditions are as shown in Table 1. The result is shown in FIG. 4 assuming that the utilization rate of B ₃ is 100. FIG.
As is clear from the above, the heating temperature is less than 50 ° C, and
If the temperature exceeds 0 ° C, the utilization index will decrease significantly. Therefore, the heating temperature in the alkali heat treatment is 50 ° C to
It turns out that it is preferable to carry out in the range of 150 ° C.

At the heating temperature of 50 ° C. to 150 ° C., good results were obtained. When the temperature was within this range, the higher order of cobalt proceeded smoothly, and the produced higher order cobalt compound was the active material. This is because the conductivity is further enhanced. On the other hand, when the heat treatment temperature becomes low, the solubility of cobalt hydroxide decreases, so that the higher order of cobalt does not proceed smoothly,
In addition, the structure of the coating layer cannot be changed appropriately, so that it is considered that the utilization factor decreases. On the other hand, when the heat treatment temperature exceeds 150 ° C., it is considered that the utilization rate decreases because the nickel hydroxide itself, which is the mother particle, changes to inactive nickel oxide.

(Experiment 6) In Experiment 6, the alkali heat treatment was performed.
Lithium ion of 0.7 molar concentration in alkaline solution
Ni active material E, which is obtained by blending
Other than not adding lithium ion to the alkaline solution
Is a Ni active material B prepared in the same manner as in E above. ₃Over discharge with
Compare the characteristics, mix the alkaline solution with lithium ions
The effect in the case of

As a result, the overdischarge characteristic of the E battery in which lithium ions were mixed in the alkaline solution was 105 when the overdischarge characteristic of the B ₃ battery was 100. From this result, when lithium ion is added to the alkaline solution,
It can be seen that the overdischarge characteristics are remarkably improved. The above results are considered as follows. When alkali heat treatment is performed using an alkali metal solution containing lithium ions, lithium can be present in the coating layer. Therefore, it is considered that since the lithium is present in the vicinity of nickel hydroxide where the action and effect can be most efficiently exhibited, the addition amount can at least sufficiently enhance the overdischarge characteristics. From this, in the case of this method, the over-discharge characteristics can be improved with a smaller amount of lithium than in the case of adding lithium to the electrolytic solution.

In the above experiment, particles made of nickel hydroxide were used as the mother particles, but mother particles made by mixing one kind or two or more kinds of other metal compounds forming a solid solution with nickel hydroxide are used. Of course, you can do that. Examples of such metal compounds include compounds such as zinc, cadmium, magnesium and calcium.

[0051]

As is apparent from the above description, the nickel active material particles of the present invention have high conductivity and excellent utilization factor and overdischarge characteristics. Therefore, the alkaline storage battery configured using such a nickel active material is a battery that can exhibit high performance under various usage conditions.

Further, according to the method for producing a nickel active material for alkaline storage batteries of the present invention, the nickel active material having the above-mentioned characteristics can be produced easily and with good yield. Therefore, according to the manufacturing method of the present invention, it is possible to obtain the effect that the nickel active material having excellent utilization factor and overdischarge characteristic can be provided at low cost.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the average particle size of nickel hydroxide mother particles and the active material utilization rate (index).

Fig. 2 Coating amount of higher cobalt compound on nickel hydroxide mother particles and electric capacity (index) per unit active material weight
It is a graph which shows the relationship of.

FIG. 3 is a graph showing the relationship between the concentration of an alkali metal solution and the active material utilization rate (index) in an alkali heat treatment.

FIG. 4 is a graph showing a relationship between a heating temperature and an active material utilization rate (index) in alkali heat treatment.

Claims (10)

[Claims] 1. A nickel active material for an alkaline storage battery, wherein a part or all of the surface of mother particles containing nickel hydroxide as a main component is coated with a metal compound containing at least cobalt hydroxide, The nickel active material is a nickel active material for an alkaline storage battery, which has an average particle diameter of 3 μm or more and 20 μm or less according to a laser diffraction method. 2. The nickel active material for an alkaline storage battery according to claim 1, wherein the metal compound further contains a lithium compound. 3. The nickel active material for an alkaline storage battery according to claim 1, wherein the metal compound is contained in an amount of 1% by weight or more and 15% by weight or less based on the mother particles. 4. The nickel active material for an alkaline storage battery according to claim 1, wherein the hydroxide of cobalt is a high-order cobalt hydroxide having a valence of more than two. 5. A metal salt solution containing at least a cobalt salt, wherein mother particles having an average particle diameter of 1 μm or more and less than 20 μm and containing nickel hydroxide as a main component are dispersed, and then the metal in which the mother particles are dispersed is dispersed. The pH of the salt solution is adjusted with an alkaline solution to deposit at least a cobalt hydroxide precipitate with the mother particles as nuclei to form a coating layer containing a predetermined amount of cobalt hydroxide on the surface of the mother particles. A method for producing a nickel active material for an alkaline storage battery, which comprises preparing a nickel active material having an average particle size of 3 μm or more and 20 μm or less by a laser diffraction method. 6. The nickel active material for an alkaline storage battery according to claim 5, wherein the coating layer containing the predetermined amount of cobalt hydroxide is 1% by weight or more and 15% by weight or less with respect to the mother particles. Method of manufacturing substance. 7. The alkali according to claim 5, wherein after forming a coating layer having at least cobalt hydroxide, the coated particles are impregnated with an alkali metal solution and heat-treated in the presence of oxygen. A method for producing a nickel active material for a storage battery. 8. The method for producing a nickel active material for an alkaline storage battery according to claim 7, wherein the alkali metal concentration of the alkali metal solution is 15% by weight or more and 40% by weight or less. 9. The method for producing a nickel active material for an alkaline storage battery according to claim 7, wherein the alkali metal solution further contains lithium ions. 10. The temperature of the heat treatment is 50 ° C. or higher,
It is 150 degreeC or less, The manufacturing method of the nickel active material for alkaline storage batteries of Claim 7 thru | or 9 characterized by the above-mentioned.