JPH1125965A - Manufacture of positive electrode active material for alkaline storage battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To continuously grow oxide particles of a plurality of metallic elements composed of a plurality of layers from a center part to a surface using Ni as a main metallic element by changing the composition or kind of metallic group salt for forming oxides in the layers of the adjacent stages of a reaction crystallization vessel. SOLUTION: In a reaction vessel 1, a nickel salt aqueous solution supply line 3, a different kind metallic salt aqueous solution supply line 4, a medium crystal material supply line 5 and an alkaline aqueous solution supply line 6 are introduced, and in a reaction vessel 2, a nickel aqueous solution supply line 7, a different kind metallic salt supply line 8 and an alkaline aqueous solution supply line 9 are introduced. The alkaline aqueous solution supply lines 6 and 9 maintains pH within a specified range by a pH state. By performing continuous supplying to a subsequent stage vessel at the same flow speed as that for starting material aqueous solution, a grown oxide made of a plurality of metal elements is taken out. Conditions in the vessel are maintained constant by stirring blades 16 and 17 connected to stirring devices 14 and 15 in the reaction vessels 1 and 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a high-capacity and high-reliability positive electrode active material for an alkaline storage battery using an oxide of a plurality of metal elements as a main material.

[0002]

2. Description of the Related Art In recent years, portable devices have been increasingly miniaturized, and there is inevitably a demand for a high-density secondary battery, which is a power source thereof. In addition, since the applications of the devices are diversifying, batteries with stable performance in a wide temperature range, particularly at a high temperature, have been desired.

To date, nickel oxide has been used as the main active material of the positive electrode for alkaline storage batteries, but the electrode base has been replaced with a sintered electrode using a conventional sintered substrate, and has a high porosity. 2. Description of the Related Art An electrode in which a three-dimensional porous nickel foam is filled with a nickel oxide powder at a high density has been industrialized, and a dramatic increase in capacity has been achieved. Conventionally, the above-mentioned method for producing a nickel oxide powder employs a method in which an aqueous nickel salt solution is allowed to act on an aqueous alkali solution such as sodium hydroxide to precipitate the precipitate, which is then matured, crystal-grown, and then mechanically ground. However, there is a problem that it is difficult to obtain a high packing density because the production method is complicated and the powder shape is irregular.

[0004] However, as disclosed in Japanese Patent Publication No. 4-80513, as another production method, an ammonia is acted on an aqueous nickel salt solution to form an ammonium complex of nickel, and nickel hydroxide is produced in an aqueous alkaline solution. A method for growing sapphire has been proposed, which has enabled a reduction in cost and a high density packing due to the nearly spherical particle shape. However, in this advance, there has been a problem that charging efficiency is reduced by using high-density particles grown to several tens of μm as an active material. It is disclosed that this can be improved by adding Co, its oxide, Ni and the like. (For example, JP-B-61-37733, Electrochemistry, Vol. 54, No. 2, p159 (1986), Power Sources, 12, p2
03 (1988)) Furthermore, with the recent demand for high performance of small secondary batteries described above, further improvement of the positive electrode characteristics,
For example, it has been strongly desired to improve the active material itself for the purpose of (a) improving the utilization factor under a high-temperature atmosphere, (b) suppressing the swelling of the positive electrode, and (c) increasing the energy density.

In order to solve the above problems (a) and / or (b), Japanese Patent Publication No. 3-26903, Japanese Patent Publication No. 3-50384, Electrochemistry, Vol. 54, No. 2, p. 1986), Power Sources
12, p 203 (1988), a method of adding Cd and Co to the inside of a crystal of an active material has conventionally been adopted, but cadmium and cobalt have been used due to increased awareness of battery components from an environmental standpoint. Free batteries have been demanded, and Zn and the like have been proposed as examples of metal elements in place of cadmium, and solid solutions of three elements such as Co, Zn and Ba have also been proposed (for example, US Pat. No. 5,536,831).

On the other hand, in order to increase the energy density in (c), an active material having a high reaction order is required. As described above, most of the positive electrode active materials of industrially used alkaline storage batteries are nickel oxide, and the reaction is said to be a one-electron reaction zone. It has been reported that the addition of an element provides an active material of a high reaction order (for example, J. Power Sour
ces, 35, 294 (1991), Solid State Ionics, 32/33 p10
4 (1989), U.S. Patent No. 5,348,822 (1994)). But,
The active material having a high reaction order has a wide interlayer in a charged state and is not suitable for high-density packing, and has not been put to practical use at present.

[0007] On the other hand, we have newly found that some materials have a high density at the time of electrode construction and promote the formation of high-order oxides at the time of charging (Abstracts of the Autumn Meeting of Electrochemical Science, 2L23 (1995) ). The solid solution in nickel oxide for the purpose of increasing the efficiency of the charge / discharge characteristics is a technique that has been used for sintered electrodes for a long time, and Mg, Ca, Ba, T
Examples of improvements include the use of one or more solid solutions selected from i, Zn, Mn, Co, Fe, Cu, Sc, Y, and the like (JP-A-51-122737).

As described above, interest in oxides of a plurality of metal elements in which a metal element other than nickel is added inside nickel oxide crystals has been increasing. However, the oxide of the plurality of metal elements, depending on the type and composition of the added metal, lowering of charging efficiency at high temperatures due to lowering of oxygen overvoltage,
There were problems such as a decrease in charge / discharge potential and a decrease in chemical or electrochemical stability. In order to solve these problems, it is necessary to improve the physical properties of the interface between the active material and the electrolyte, and therefore, near the surface of the active material, high charge efficiency at high temperature, high charge / discharge potential, An active material coated with an oxide of a plurality of metal elements having characteristics such as high chemical and electrochemical stability has been proposed (Japanese Patent Application No. 08-249496). The oxides of a plurality of metal elements having the above-mentioned characteristics are improved by increasing the ratio of the substitution element, but the amount of nickel, which is responsible for the oxidation-reduction reaction, is reduced. It is not always suitable for improvement.

However, by coating only the vicinity of the surface, it is possible to obtain a highly reliable active material having the above-mentioned characteristics without reducing the number of reaction electrons of an internal oxide occupying most of the active material. Can be. As a method for producing the surface coating material, Japanese Patent Application No. 08-249496, JP-A-8-203
Conventionally, as seen in Japanese Patent Publication No. 517, etc., a batch method has been proposed in which an oxide of an inner layer is first synthesized, washed with water, dried, and then an oxide of a surface layer is grown in another crystallization tank. Have been. However, although different from the above-mentioned nickel-based oxide, a method for producing nickel hydroxide coated with cobalt hydroxide includes a tank for growing internal nickel hydroxide, a tank for washing with water, and a tank for cobalt hydroxide. (Japanese Patent Application No. 07-40853) has been proposed. However, since the application is intended for coating with cobalt hydroxide, a water washing tank is provided between the preceding nickel hydroxide crystallization tank and the cobalt hydroxide crystallization tank, and equipment considered in the present invention. Configuration is different.

[0010]

SUMMARY OF THE INVENTION In a method for producing an oxide containing nickel whose main metal element is different in composition and type between a surface layer and an inner layer, the process is complicated because of a batch system, and mass production is difficult. Lowness is a problem. An object of the present invention is to solve the above-mentioned problems and to provide a high-capacity, high-reliability method for producing an oxide of a plurality of metal elements which is excellent in mass productivity.

[0011]

In order to solve the above-mentioned problems, in the present invention, an aqueous solution of a salt of a plurality of metal elements and an aqueous solution of an alkali are reacted through a plurality of continuous multi-stage reaction crystallization tanks to form oxides of the plurality of metal elements. In the step of continuously growing, the composition or type of the metal element group salt forming an oxide in the tanks adjacent to each other in the reaction crystallization tank is different from each other, a production method is proposed. .

Thus, in each reaction crystallization tank,
Oxides of different composition and / or type, with nickel as the main metal element, can be grown, and it is possible to continuously produce positive electrode active material particles formed from a plurality of layers of the oxide. . Therefore, the process can be simplified as compared with the conventional batch type, and the mass productivity can be improved.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The invention according to claim 1 of the present invention is characterized in that the particles of the positive electrode active material are formed of a plurality of layers from the center toward the surface, and each layer is composed of a plurality of metal elements mainly composed of Ni. A method for producing a positive electrode active material for an alkaline storage battery comprising an oxide of an element, wherein the oxide is reacted with an aqueous solution of a salt of a plurality of metal elements and an aqueous alkali solution through a plurality of continuous multi-stage reaction crystallization tanks to convert the oxide into a desired one. In the step of continuously growing to a particle diameter, the composition and / or type of metal salts for forming an oxide in tanks adjacent to each other in the reaction crystallization tank are different from each other. By connecting a plurality of reaction crystallization tanks, and by reacting an aqueous solution of a salt of a metal element of a different type with an aqueous alkali solution in each tank to grow the metal oxide, the first-stage tank is formed. Grow up The surface of the metal oxide particles, it is possible to form a plurality of layers of the composition at a subsequent stage of the tank, different metal oxides. Further, it becomes possible to continuously produce the oxide as compared with the conventional batch method, and the process can be simplified.

According to a second aspect of the present invention, in the multistage reaction crystallization tank, the metal element group salt in the last tank is Ca, Ti, Zn, Sr, Y, Ba, Cd in addition to Ni. , Co,
It is characterized by containing at least one kind of metal element salt selected from Cr, rare earth metal and Bi in the former tank, and has characteristics such as improvement of oxygen generation overvoltage (improvement of charging efficiency). Thus, a material containing a large amount of the oxide of the metal element in the surface layer can be continuously manufactured, and the process can be simplified.

According to a third aspect of the present invention, the metal element group salt in the tank preceding the final tank of the multiple reaction crystallization tank is at least Al, V, Cr, Mn, Fe, Cu, G
e, Zr, Nb, Mo, Ag, Sn, W, characterized in that it contains more than one kind of metal element salt in the final tank. And a material containing a large amount of an oxide of the metal element in an inner layer having properties such as causing low chemical and / or electrochemical stability can be continuously produced,
The process can be simplified.

Hereinafter, an embodiment of the present invention will be described with reference to FIG. A reaction tank 1 has a nickel salt aqueous solution supply line 3 and a different metal salt aqueous solution supply line 4.
, A habit crystal material supply line 5 and an alkaline aqueous solution supply line 6 are introduced, and a nickel salt aqueous solution supply line 7, a dissimilar metal salt supply line 8, and an alkaline aqueous solution supply line 9 are provided in the reaction tank 2. Has been introduced. The alkaline aqueous solution supply lines 6 and 9 are provided with pH stats to control the supply of the alkaline aqueous solution,
H is within a predetermined range. The reaction tanks 1 and 2 are provided with constant temperature baths 10 and 11, respectively. The reaction tanks 1 and 2 are provided with a line 1 for taking out a liquid containing oxide particles of a plurality of grown metals.
Nos. 2 and 13 are provided, and are continuously supplied to the subsequent tank at the same flow rate as the total supply flow rate of the aqueous solution of the starting material, so that oxides of a plurality of grown metals can be taken out. A stirring device 1 is provided inside each of the reaction tanks 1 and 2.
Stirring blades 16 and 17 connected to the reactors 4 and 15 are provided to keep various conditions in the reactors 1 and 2 constant.

Here, a configuration in which particles are grown through a two-stage reaction crystallization tank has been described. However, a similar configuration can be applied to a three-stage or more-stage reaction tank. Further, in addition to the reaction crystallization tank for growing the oxides of the plural metals, a tank for reacting with an aqueous solution containing a habit modifier such as ammonium ion, a tank for classification, a tank for washing, a conductive material It is good also as a structure which connected the tank etc. for coating Co oxide as the above.

[0018]

Next, a specific example of the present invention will be described with reference to the drawings. (Example 1) First, an object is to obtain active material particles formed from a plurality of metal oxide layers by including more metal salts than Ni in the last tank in the last tank. A method for producing an oxide of a plurality of metal elements in which the inner layer is composed of nickel hydroxide and the surface layer is composed of calcium-dissolved nickel hydroxide will be specifically described. The configuration of the production apparatus was the same as that of the two-stage connected reaction crystallization tanks 1 and 2 shown in FIG. 1, and each had a volume of 3 l. First, 2.
A 4 mol / l nickel sulfate aqueous solution and a 4.8 mol / l ammonia aqueous solution were prepared. And average these solutions
At the same time, feed into the reaction tank 1 at a rate of 0.5 ml / min.
While maintaining the temperature at 0 ° C. and stirring rapidly and uniformly, a 4.8 mol / l aqueous sodium hydroxide solution was added at an average of 0.1%.
It was added at 5 ml / min so that the pH value in the reaction tank was maintained within the range of 12.5 ± 0.2. After the condition in the reaction tank was stabilized, a suspension containing nickel hydroxide particles grown to an average particle size of 12 μm was supplied into the reaction tank 2 at an average rate of 1.5 ml / min, and simultaneously with the suspension, 2.2. mol / l nickel nitrate aqueous solution and 0.2m
ol / l calcium nitrate aqueous solution on average 0.5 ml / min each
4.8 mol / l sodium hydroxide aqueous solution at an average of 0.5 ml / min while the vessel is stirred at a constant temperature of 50 ° C. It was added to keep it within the range of 12 ± 0.2. After the condition in the reaction tank was stabilized, the suspension was allowed to overflow from the upper part of the reaction tank and samples were continuously collected. The obtained suspension was centrifuged, the supernatant was replaced with ion-exchanged water, and subjected to classification in a fluid, so that Ni generated mainly in the powder containing Ca generated in the reaction vessel 2 throughout the reaction tank 2 was mainly contained. After removing the oxide microcrystals, the powder was washed with water and dried to obtain a powder having an average particle size of 12.5 μm.

On the other hand, as a comparative example, an example of a conventional batch-type manufacturing method will be described. The configuration of the production apparatus used the reaction tanks 1 and 2 shown in FIG. 1 independently. First, in the same manner as described above, the nickel hydroxide particles
The suspension was grown to 12 μm, and this suspension was continuously taken out by overflowing from the upper part of the reaction tank. The obtained suspension was centrifuged, and the washing operation of replacing the supernatant with ion-exchanged water was repeated several times, and then dried.
100 g of the obtained dry powder is put into the reaction vessel 2 and 2.2 mol / l
Nickel nitrate aqueous solution, 0.2 mol / l calcium nitrate aqueous solution, 4.8 mol / l ammonia aqueous solution 0.5 mol / min each
At the same time and into the reaction tank 2 while stirring at a constant temperature of 50 ° C. while stirring the 4.8 mol / l aqueous sodium hydroxide solution at an average of 0.5 ml / min. It was added to keep it within the range of 12 ± 0.2. After a lapse of 3 hours, the suspension in the reaction tank is collected and subjected to classification in a fluid in the same manner as described above, so that an oxide mainly containing Ni containing Ca generated in the reaction tank 2 throughout the powder. After removing microcrystals, the product was washed with water and dried to obtain a powder having an average particle size of 12.5 μm.

FIG. 2 shows a characteristic X-ray image of Ca of a cross section of the oxide powder of a plurality of metal elements obtained by the present invention. FIG.
(a) shows a SEM image of a cross section of the same powder, and FIG.
It is the result of detecting the characteristic X-ray of Ca at the same position as (a), and indicates that Ca is present in the portion shown in white. As a result, the composition was different between the surface layer and the inner layer, and it was possible to observe a state in which a large amount of Ca was present in the surface layer of about 0.5 μm. In addition, since the characteristic X-ray image and the result of the composition analysis of the sample obtained by the batch method almost coincided with each other, it was found that a sample similar to the conventional batch method was obtained in the present invention. Furthermore, in the results of evaluating the electrochemical characteristics of both, almost the same results were obtained.

Here, of the two-stage reaction crystallization tank,
The case where the final stage contains more Ca salt than the previous stage is shown, but Ti, Zn, Sr, Y, Ba, Cd, C
Similarly, in the case where more than one metal element salt selected from the group consisting of o, Cr, rare earth metal, and Bi is contained in the former stage, the oxide powder mainly containing nickel whose surface layer contains a large amount of the metal element is continuously produced. I got it.

(Example 2) Next, the active material particles formed of a plurality of metal oxide layers are obtained by containing more metal salts than Ni in the former tank than the last tank in the next tank. As an example, a method for producing an oxide of a plurality of metal elements in which the inner layer is composed of manganese solid solution nickel hydroxide and the surface layer is composed of nickel hydroxide will be specifically described. The configuration of the production apparatus was the same as that of the two-stage connected reaction crystallization tanks 1 and 2 shown in FIG. 1 and each had a volume of 3 l. First, a 2.2 mol / l nickel sulfate aqueous solution,
A 0.2 mol / l manganese sulfate aqueous solution and a 4.8 mol / l ammonia aqueous solution were prepared. Then, these solutions were simultaneously supplied into the reaction tank 1 at an average rate of 0.5 ml / min, and 4.8 mol / l while rapidly and uniformly stirring while keeping the inside of the tank constant at 50 ° C. Average sodium hydroxide solution
It was added at 0.5 ml / min so that the pH value in the reaction tank was maintained within the range of 12.0 ± 0.2. After the condition in the reaction tank was stabilized, a suspension containing manganese-dissolved nickel hydroxide particles grown to an average particle diameter of 12 μm was supplied into the reaction tank 2 at an average speed of 2.0 ml / min. At the same time, a 2.4 mol / l aqueous solution of nickel sulfate is supplied into the reaction tank 2 at an average rate of 0.5 ml / min, and while the inside of the tank is kept constant at 50 ° C., stirring is performed at 4.8 mol / l.
Of sodium hydroxide was added at an average of 0.5 ml / min so that the pH value in the reaction tank was maintained within the range of 12.5 ± 0.2. After the condition in the reaction tank was stabilized, the suspension was allowed to overflow from the upper part of the reaction tank and samples were continuously collected. The obtained suspension was subjected to centrifugation, the supernatant was replaced with ion-exchanged water, and classification was performed in a fluid to remove fine crystals of oxides mainly composed of Ni generated in the reaction tank 2. Thereafter, the resultant was washed with water and dried to obtain a powder having an average particle diameter of 12.5 μm.

On the other hand, as a comparative example, an example of a conventional batch-type manufacturing method will be described. The configuration of the production apparatus used the reaction tanks 1 and 2 shown in FIG. 1 independently. First, manganese-dissolved nickel hydroxide particles were grown to an average particle size of 12 μm in the reaction tank 1 in the same manner as described above, and the suspension was continuously overflowed from the top of the reaction tank and taken out. The obtained suspension was centrifuged, and the washing operation of replacing the supernatant with ion-exchanged water was repeated several times, and then dried. 100 g of the obtained dry powder in the reaction tank 2
Then, a 2.4 mol / l nickel sulfate aqueous solution and a 4.8 mol / l ammonia aqueous solution were added at a rate of 0.5 mol / min to the reaction tank 2.
4.8 mol / l aqueous sodium hydroxide solution on average while stirring while keeping the inside of the tank constant at 50 ° C.
It was added at 0.5 ml / min so that the pH in the reaction tank was maintained within the range of 12.5 ± 0.2. After a lapse of 3 hours, the suspension in the reaction tank was collected and subjected to classification in a fluid in the same manner as described above to remove fine crystals of oxides mainly composed of Ni generated in the reaction tank 2. After washing and drying, a powder having an average particle size of 12.5 μm was obtained.

A comparison of the characteristic X-ray images of the cross-sections of the oxide powders of a plurality of metal elements obtained by the present invention and the conventional method shows that both have different compositions between the surface layer and the inner layer. In the surface layer of 0.5 μm, it was possible to observe a state of nickel hydroxide containing no Mn. From these results, it was found that a sample similar to the conventional batch type can be obtained in the present invention. Furthermore, in the results of evaluating the electrochemical characteristics of both, almost the same results were obtained.

Although the case where the Mn salt is contained more than the final tank is shown here, Al, V, Cr, Fe, Cu, G
Similarly, in the case where more than one kind of metal element salt selected from e, Zr, Nb, Mo, Ag, Sn, and W is contained in the former stage, similarly, an oxide mainly containing nickel containing more of the metal element in the inner layer A powder could be obtained. (Example 3) Next, in an adjacent tank, an example is given in which the type of metal salt other than Ni is changed to obtain active material particles formed from a plurality of metal oxide layers. The inner layer is manganese solid solution nickel hydroxide,
A method for producing an oxide of a plurality of metal elements in which the surface layer is composed of calcium-dissolved nickel hydroxide will be specifically described. The structure of the production apparatus is shown in FIG.
, Each having a volume of 3 l. First, 2.2 mol / l nickel sulfate aqueous solution, 0.2 mol / l
Manganese sulfate aqueous solution and 4.8 mol / l ammonia aqueous solution were prepared. Each of these solutions was averaged 0.5 ml /
At the same time, the solution was fed into the reaction tank 1 at a rate of 50 min.
It was added so that the pH value in the reaction tank was maintained within the range of 12.0 ± 0.2 with n. After the condition in the reactor is stabilized, the average particle size is 12
The suspension containing the manganese-dissolved nickel hydroxide particles grown to μm is supplied into the reaction vessel 2 at an average speed of 2.0 ml / min.
At the same time, 2.2mol / l nickel nitrate aqueous solution, 0.2mol / l
Is supplied into the reaction vessel 2 at an average rate of 0.5 ml / min. While stirring the vessel while keeping the inside of the vessel at 50 ° C., a 4.8 mol / l aqueous solution of sodium hydroxide is added on average to 0.5 ml / min. It was added at a rate of ml / min so that the pH value in the reaction tank was maintained within the range of 12.0 ± 0.2. After the condition in the reaction tank was stabilized, the suspension was allowed to overflow from the upper part of the reaction tank and samples were continuously collected. The obtained suspension is subjected to centrifugal separation, the supernatant is replaced with ion-exchanged water, and subjected to classification in a fluid. After removing fine crystals of the product, the product was washed with water and dried to obtain a powder having an average particle size of 12.5 μm.

On the other hand, as a comparative example, an example of a conventional batch-type manufacturing method will be described. The configuration of the production apparatus used the reaction tanks 1 and 2 shown in FIG. 1 independently. First, manganese-dissolved nickel hydroxide particles were grown to an average particle size of 12 μm in the reaction tank 1 in the same manner as described above, and the suspension was continuously overflowed from the top of the reaction tank and taken out. The obtained suspension was centrifuged, and the washing operation of replacing the supernatant with ion-exchanged water was repeated several times, and then dried. 100 g of the obtained dry powder in the reaction tank 2
Then, a 2.2 mol / l aqueous solution of nickel nitrate, a 0.2 mol / l aqueous solution of calcium nitrate, and a 4.8 mol / l aqueous solution of ammonia were simultaneously supplied into the reaction vessel 2 at a rate of 0.5 mol / min. While stirring at a constant temperature of 4.degree.
An 8 mol / l sodium hydroxide aqueous solution was added at an average of 0.5 ml / min so that the pH in the reaction vessel was maintained within a range of 12.0 ± 0.2. After a lapse of 3 hours, the suspension in the reaction tank was sampled, and classified in a fluid in the same manner as described above.
After removing microcrystals of an oxide mainly containing Ni containing Ca generated inside the powder, the powder was washed with water and dried to obtain a powder having an average particle diameter of 12.5 μm.

Comparison of the characteristic X-ray images of the cross-sections of the oxide powders of a plurality of metal elements obtained by the present invention and the conventional method revealed that both had different compositions between the surface layer and the inner layer. It was observed that the surface layer of 0.5 μm contained a large amount of Ca and the internal layer contained a large amount of Mn. From these results, it was found that a sample similar to the conventional batch type can be obtained in the present invention. Furthermore, in the results of evaluating the electrochemical characteristics of both, almost the same results were obtained.

Here, in the final stage tank, Ca
Although the case where a large amount of salt is contained and a large amount of Mn salt is contained in the preceding stage of the final stage, the case where Ti, Z
n, Sr, Y, Ba, Cd, Co, Cr, rare earth metal,
Bi contains more than one kind of metal element salt selected from Bi, and Al, V, C
r, Fe, Cu, Ge, Zr, Nb, Mo, Ag, S
Similarly, in the case where more than one kind of metal element salt selected from n and W was contained in the final stage, an oxide powder mainly composed of nickel having different compositions in the surface layer and the inner layer could be obtained.

Example 4 Next, active material particles formed from a plurality of metal oxide layers by using three or more stages of reaction crystallization tanks and changing the composition or type of metal salt in each stage. For the purpose of obtaining, as an example, the inner layer is made of manganese solid solution nickel hydroxide, the outer layer is made of aluminum solid solution nickel hydroxide, and the outer layer (surface layer) is made of calcium solid solution nickel hydroxide. A method for producing an oxide of a plurality of metal elements having a three-layer structure will be specifically described. The structure of the manufacturing apparatus is a three-stage connected reaction crystallization tank 1 shown in FIG.
8, 19, and 20, each having a volume of 3
1 was used. First, a 2.2 mol / l nickel sulfate aqueous solution, a 0.2 mol / l manganese sulfate aqueous solution, and a 4.8 mol / l ammonia aqueous solution were prepared. Then, these solutions were simultaneously supplied into the reaction tank 18 at an average rate of 0.5 ml / min, respectively, and stirred at 4.8 mol / l while keeping the inside of the tank constant at 50 ° C. so as to quickly and uniformly. Sodium hydroxide aqueous solution was added at an average of 0.5 ml / min so that the pH value in the reaction tank was kept within a range of 12.0 ± 0.2. After the condition in the reaction tank was stabilized, a suspension containing manganese-dissolved nickel hydroxide particles grown to an average particle diameter of 12 μm was supplied into the reaction tank 19 at an average speed of 2.0 ml / min. At the same time, a 2.2 mol / l aqueous solution of nickel sulfate and a 0.2 mol / l aqueous solution of aluminum sulfate were respectively supplied into the reaction vessel 19 at an average rate of 0.5 ml / min, and the vessel was stirred at a constant temperature of 50 ° C. While 4.
An 8 mol / l sodium hydroxide aqueous solution was added at an average of 0.5 ml / min so that the pH value in the reaction vessel was maintained within a range of 12.5 ± 0.2. After the condition in the reactor is stabilized, the average particle size is 12.5μ
A suspension of manganese-dissolved nickel hydroxide particles with aluminum-dissolved nickel hydroxide grown on the surface layer
The solution was supplied into the reaction vessel 20 at a rate of 3.5 ml / min, and simultaneously with the suspension, a 2.2 mol / l aqueous solution of nickel nitrate and a 0.2 mol / l aqueous solution of calcium nitrate were each supplied at an average rate of 0.5 ml / min. The pH value in the reaction tank is in the range of 12.0 ± 0.2 at an average of 0.5 ml / min while stirring while maintaining the inside of the tank at 50 ° C. while keeping the inside of the tank constant at 50 ° C. It was added so as to keep within. After the condition in the reaction tank was stabilized, the suspension was allowed to overflow from the upper part of the reaction tank and samples were continuously collected. The obtained suspension is centrifuged, the supernatant is replaced with ion-exchanged water, and classification is performed in a fluid, so that oxidation generated mainly in Ni containing Ca generated in the reaction tank 20 throughout the inside of the powder is performed. After removing the fine crystals of the product, the product was washed with water and dried to obtain a powder having an average particle size of 12.7 μm.

On the other hand, an example of a conventional batch-type manufacturing method will be described. The configuration of the manufacturing apparatus is the reaction tank 1 shown in FIG.
8, 19 and 20 were used independently. First, manganese-solid-dissolved nickel hydroxide particles were grown to an average particle size of 12 μm in the reaction tank 18 in the same manner as described above, and the suspension was continuously overflowed from the top of the reaction tank and taken out. The obtained suspension was centrifuged, and the washing operation of replacing the supernatant with ion-exchanged water was repeated several times, and then dried. The obtained dry powder is placed in a reaction vessel 19 for 10 minutes.
0 g, a 2.2 mol / l nickel sulfate aqueous solution, a 0.2 mol / l aluminum sulfate aqueous solution, and a 4.8 mol / l ammonia aqueous solution were simultaneously supplied to the reaction vessel 19 at a rate of 0.5 mol / min, respectively. While stirring at 50 ° C,
A 4.8 mol / l sodium hydroxide aqueous solution was added at an average of 0.5 ml / min so that the pH in the reaction vessel was maintained within a range of 12.5 ± 0.2. After a lapse of 3 hours, the suspension in the reaction tank was collected.
The obtained suspension was centrifuged, and the washing operation of replacing the supernatant with ion-exchanged water was repeated several times, and then dried. 100 g of the obtained dry powder is put into the reaction vessel 20, and a 2.2 mol / l aqueous nickel nitrate solution, a 0.2 mol / l aqueous calcium nitrate solution, and a 4.8 mol / l aqueous ammonia solution are reacted at a rate of 0.5 mol / min each. 4.8 mol / l while simultaneously feeding into the tank 20 and stirring while keeping the inside of the tank constant at 50 ° C.
Of sodium hydroxide was added at an average of 0.5 ml / min so that the pH in the reaction tank was maintained within the range of 12.5 ± 0.2.
After a lapse of 3 hours, the suspension in the reaction tank was collected and subjected to classification in a fluid in the same manner as described above, whereby an oxide mainly containing Ni containing Ca generated in the reaction tank 20 throughout the powder was obtained. After removing microcrystals, the powder was washed with water and dried to obtain a powder having an average particle size of 12.7 μm.

A comparison of the characteristic X-ray images of the cross-sections of the oxide powders of a plurality of metal elements obtained by the present invention and the conventional method shows that both have a three-layer structure, and each layer has a different composition. The surface layer of about 0.2 μm is nickel hydroxide containing a large amount of Ca, the intermediate layer of about 0.5 μm is nickel hydroxide containing a large amount of Al, and the internal layer is nickel hydroxide containing a large amount of Mn. Was observed. From these results, it was found that a sample similar to the conventional batch type can be obtained in the present invention. Furthermore, in the results of evaluating the electrochemical characteristics of both, almost the same results were obtained.

Here, in the final tank, Ca
Although the case where a large amount of salt is contained and the former tank contains a large amount of Al salt and Mn salt is shown, the final tank contains Ti, Z.
n, Sr, Y, Ba, Cd, Co, Cr, rare earth metal,
Bi contains more than one kind of metal element salt selected from Bi, and V, Cr, Fe, Cu,
Similarly, in the case where more than one kind of metal element salt selected from Ge, Zr, Nb, Mo, Ag, Sn, and W is contained in the final stage, similarly, an oxide powder mainly composed of nickel having a three-layer structure and different compositions. Could be obtained.

Also, the case where the particles are grown through a three-stage reaction crystallization tank has been described as an example here, but a multi-layer reaction crystallization tank of a further stage also has a different composition between the inner and surface layers. An oxide powder mainly composed of nickel was obtained. According to the above-described embodiments of the present invention, an active material formed from a plurality of metal oxide layers by using a multi-stage reaction crystallization apparatus and changing the composition or type of the metal group salt in the tanks adjacent to each other is used. Particles can be produced. In addition, since it can be manufactured continuously, mass productivity can be improved as compared with the conventional batch method.

[0034]

As described above, according to the present invention, a plurality of continuous multi-stage reaction crystallization tanks are used, and a metal group salt for forming oxides in adjacent layers of the reaction crystallization tanks is used. By changing the composition or the type of, the oxide particles of a plurality of metal elements having Ni as a main metal element formed from a plurality of layers from the center toward the surface are continuously grown,
The process can be greatly simplified as compared with the conventional batch method, and mass productivity can be improved.

[Brief description of the drawings]

FIG. 1 is a model diagram showing an apparatus for producing a positive electrode active material for an alkaline storage battery according to an embodiment of the present invention (an embodiment in which two reaction crystallization tanks are connected).

FIG. 2 shows that the surface layer obtained by the production method of the present invention is C
(a) An electron micrograph showing the cross-sectional shape of the oxide powder of a plurality of metal elements in which the inner layer is made of solid-solution nickel hydroxide and consisting of nickel hydroxide, and a corresponding X-ray photograph showing the distribution of Ca by characteristic X-rays

FIG. 3 is a model diagram showing an apparatus for manufacturing a positive electrode active material for an alkaline storage battery according to an embodiment of the present invention (an embodiment in which three reaction crystallization tanks are connected).

[Explanation of symbols]

 1. Reaction tank 2. Reaction tank 3. Nickel salt aqueous solution supply line 4. Dissimilar metal salt aqueous solution supply line 5. Habit crystal material supply line 6. Alkaline aqueous solution supply line 7. Nickel salt aqueous solution supply line 8. Foreign metal salt aqueous supply Line 9. Alkaline aqueous solution supply line 10. Constant temperature bath 11. Constant temperature bath 12. Slurry overflow line 13. Slurry outlet line 14. Stirrer 15. Stirrer 16. Stirrer blade 17. Stirrer blade 18. Reaction tank 19. Reaction tank 20 Reaction tank 21. Nickel salt aqueous solution supply line 22. Dissimilar metal salt aqueous solution supply line 23. Medium crystal agent supply line 24. Alkaline aqueous solution supply line 25. Nickel salt aqueous solution supply line 26. Foreign metal salt aqueous solution supply line 27. Alkaline aqueous solution Supply line 28. Nickel salt aqueous solution supply line 29. Dissimilar metal salt aqueous solution supply line 30. Alkaline aqueous solution supply line 31. Slurry overflow line 32. Slurry overflow line 33. Slurry outlet line 34. Constant temperature bath 35. Constant temperature bath 36. Constant temperature bath 37. Stirrer 38. Stirrer 39. Stirrer 40. Stirrer blade 41. Stirrer blade 42. Stirring blade

Continuing on the front page (72) Inventor Yoichi Izumi 1006 Kazuma Kadoma, Osaka Pref. Matsushita Electric Industrial Co., Ltd.

Claims (3)

[Claims] 1. Production of a positive electrode active material for an alkaline storage battery, wherein particles of the positive electrode active material are formed from a plurality of layers from the center to the surface, each layer comprising an oxide of a plurality of metal elements having Ni as a main metal element. A step of reacting an aqueous solution of a salt of a plurality of metal elements with an aqueous alkali solution through a plurality of continuous multi-stage reaction crystallization tanks to continuously grow the oxide to a desired particle size. A method for producing a positive electrode active material for an alkaline storage battery, wherein compositions or types of metal group salts for forming an oxide in tanks adjacent to each other in a deposition tank are different from each other. 2. The metal element group salt in the last tank of the multi-stage reaction crystallization tank is Ca, Ti, Zn, S in addition to Ni.
2. A positive electrode active material for an alkaline storage battery according to claim 1, wherein said positive electrode active material contains at least one metal element salt selected from the group consisting of r, Y, Ba, Cd, Co, Cr, a rare earth metal, and Bi in the former tank. Production method. 3. The multi-stage reaction crystallization tank, wherein the metal element salt in the tank preceding the last one is not only Ni but also Al, V, C
r, Mn, Fe, Cu, Ge, Zr, Nb, Mo, A
The method for producing a positive electrode active material for an alkaline storage battery according to claim 1, wherein at least one kind of metal element salt selected from g, Sn, and W is contained in the next-stage tank.