JPH08236108A - Manufacture of nickel positive electrode for alkaline storage battery - Google Patents

Abstract

PURPOSE: To manufacture a nickel positive electrode for an alkaline storage battery with low cost, high productivity, and high performance by forming cobalt hydroxide on the surface layer of a nickel hydroxide particle by neutralizing a cobalt salt, then filling it in a conductive substrate. CONSTITUTION: An NiSO4 aqueous solution 3 to which NH4 OH is added and an NaOH aqueous solution 4 are supplied to a reaction bath 1 in which a double separating wall 2 is arranged, and they are stirred and reacted about pH 11 and at around 40 deg.C. Ni(OH)2 particles produced are transferred to a tank 10, and fed to a circulation type filtration and washing device 13 with a pump 5 after pure water is added. The particles are continuously filtered, washed, and dehydrated to obtain slurry containing about 25% water, then the slurry is supplied to an auxiliary tank 15. The Ni(OH)2 slurry is put into a reaction bath 16, and a CoSO4 aqueous solution 17 is added in the bath 16, and while they are stirred, the solution is controlled to about pH 11 with an NaOH aqueous solution 4, and reaction is performed at around 40 deg.C. Co(OH)2 is formed on the surface layer of the Ni(OH)2 , then this slurry is filled in or applied to a conductive substrate as a main active material.

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 nickel positive electrode for an alkaline storage battery used in a nickel-cadmium storage battery or the like.

[0002]

2. Description of the Related Art In recent years, along with the weight reduction of portable devices and the like, there has been a demand for higher energy density of secondary batteries such as nickel-cadmium storage batteries and nickel-hydrogen storage batteries which are power sources thereof. Sintering method is the mainstream for the electrodes of conventional alkaline storage batteries, but the energy density is limited, and the process of manufacturing sintered bodies and filling active materials is complicated. A method has been developed in which a large sponge-like metal porous body is used as an active material support and a paste-like active material mainly composed of nickel hydroxide is directly filled therein.

As a method for producing nickel hydroxide used in this method, a continuous production method has been proposed as shown in Japanese Patent Publication No. 63-16555 and Japanese Patent Publication No. 2-6340. Also, in this paste type electrode plate, since the pore size of the substrate is large, the current collecting ability of the paste type electrode plate for the active material is poorer than that of the substrate. It has the disadvantage of being significantly lower than the formula. In order to solve such a problem, Japanese Examined Patent Publication No. 62-234867 and Japanese Examined Patent Publication No. 63-1528.
As disclosed in Japanese Patent Publication No. 66, a method has been proposed in which a coating layer of cobalt hydroxide is formed on the surface of nickel hydroxide to improve the utilization rate of the active material.

[0004]

However, even if nickel hydroxide is continuously produced, a considerable amount of powder of cobalt or cobalt compound other than nickel hydroxide is used as the active material in order to improve the utilization rate thereof. Need to be added.
In the conventional manufacturing process of the active material for a nickel positive electrode, as shown in FIG. 2, powders of nickel hydroxide, cobalt hydroxide and the like are respectively washed with water, dried, and then added with water and kneaded. The production energy cost per active material is high and, on the other hand, the productivity is low.

The utilization rate of the active material is also improved by forming a coating layer of cobalt hydroxide on the surface of nickel hydroxide, but as shown in FIG. The step of drying and the step of drying after forming the coating layer on the surface are performed. This drying is the most energy consuming process in a series of nickel electrode manufacturing processes, complicates the whole process, and significantly increases the manufacturing cost.

The present invention solves the above problems,
A nickel positive electrode for a high-performance alkaline storage battery that does not require a drying step up to filling and continuously produces nickel hydroxide that has produced cobalt hydroxide on its surface layer and has high productivity at low energy cost. The purpose is to provide a manufacturing method.

[0007]

In order to achieve the above object, the present invention is to produce a nickel positive electrode for an alkaline storage battery as follows. In the first step, a mixed solution prepared by mixing ammonium ions in an aqueous solution of a nickel salt is supplied so as to continuously react an aqueous solution of an alkali metal hydroxide, and the produced nickel hydroxide is continuously taken out. Filter and wash with water. In the second step, the cobalt hydroxide aqueous solution and the alkali metal hydroxide aqueous solution are continuously supplied to the nickel hydroxide slurry obtained in the first step, and the cobalt hydroxide is surface-treated by filtering and washing with water. The nickel hydroxide formed in the layer is continuously obtained. Furthermore, in the third step, the paste obtained by mainly kneading the slurry obtained in the second step with additives is filled or applied inside the metal substrate or the support.

[0008]

According to this manufacturing method, in the step of continuously manufacturing nickel hydroxide in which cobalt hydroxide is generated in the surface layer and filling or coating the conductive layer with the conductive substrate, in the nickel hydroxide powder manufacturing step. It is possible to omit the two drying steps of drying and drying in the nickel hydroxide powder manufacturing step in which the cobalt hydroxide coating layer is formed.

As a result, the energy cost during production can be reduced and a highly productive positive electrode for an alkaline storage battery can be obtained.

[0010]

【Example】

(Embodiment 1) Hereinafter, an embodiment of the present invention will be described with reference to FIG.

In the figure, reference numeral 1 is a reaction tank, here a 100 l tank having a double partition wall. The nickel salt, the alkali metal hydroxide, and the ammonium ion supplier are nickel sulfate aqueous solution having a concentration of 180 g / l,
20% by weight aqueous sodium hydroxide solution, and 18% by weight
Of ammonia water was used. 1.5 l / hr of nickel sulfate aqueous solution and 0.21 l of ammonia water were put into this reaction tank 1.
It is supplied by the pipeline 3 so that the flow rate becomes / hr. On the other hand, the metering pump 5 mixes the pH well in the nozzle
11.5 ± 0.3, while keeping the temperature inside the tank constant at 40 ± 2 ° C, sodium hydroxide was supplied to the inside of the reaction tank 1 through the pipeline 4, and a pH controller with a sensor inside the tank was used. Sodium hydroxide was intermittently added to the reaction liquid while stirring with a stirrer 9 so as to keep the pH in a coordinated manner to generate nickel hydroxide. Reference numeral 7 is a temperature controller having a sensor in the tank. The generated nickel hydroxide overflows to the outside of the double partition and is pipeline 8
It was sucked in and taken out to the tank 10. Pure water 12 is continuously supplied to the rotary filter 1 with a pipe 11.
3, the circulating filtration water washing and dehydration are performed here, the slurry having a water content of 25% is adjusted, and the slurry is supplied to the spare tank 15. The above nickel hydroxide slurry is stored in a preliminary tank 15 in a reaction tank 16 which is the same tank as the reaction tank 1.
After supplying 50 liters from the above, a 12 wt% cobalt sulfate aqueous solution was added by a metering pump 5 at a constant rate of 1.0 liter / hr.
Add H11.5 ± 0.3 into the well-stirred tank with the tank temperature kept constant at 40 ± 2 ° C, and maintain the set pH in conjunction with the pH controller.
A wt% aqueous sodium hydroxide solution was added intermittently.
When 30 l of the cobalt sulfate aqueous solution had been added, the supply of the cobalt sulfate aqueous solution and sodium hydroxide was stopped and the product was taken out.

This was continuously circulated and filtered with a rotary filter, washed with water, adjusted to a slurry having a water content of 25% by dehydration, and 5 g of metallic cobalt powder was mixed with 100 g of nickel hydroxide in the slurry, A foamed nickel porous body (porosity 95%) was obtained by thoroughly stirring the active material slurry in which water was added to make the water content 27%.
Was filled.

The nickel positive electrode thus obtained was dried, pressed under a certain condition, and then cut into 40 × 55 mm to obtain a nickel positive electrode A according to an embodiment of the present invention. Using this positive electrode, in combination with a known negative electrode of cadmium as a negative electrode, a nominal capacity of 700 mAh, which is an example of the present invention, was obtained.
AA size sealed nickel cadmium storage battery A was manufactured.

As a comparative example, nickel hydroxide powder was obtained by carrying out the process in the reaction vessel 1 in the same manner as in the example, that is, producing nickel hydroxide, filtering and washing it, and then drying. To this nickel hydroxide powder, 5 g of metallic cobalt powder was added per 100 g of nickel hydroxide powder, and an equal amount of cobalt hydroxide powder was added per cobalt hydroxide and nickel hydroxide powder produced by the reaction in the reaction vessel 16 of FIG. Then, the positive electrode obtained by filling the one with water added to have a water content of 27% was used as a nickel positive electrode B according to a comparative example, and an AA size sealed nickel cadmium storage battery B was produced in the same manner as in the example.

Further, the second step of filtration and washing with water were carried out in the same manner as in the example, and then dried to obtain a nickel hydroxide powder having cobalt hydroxide on the surface. To 100 g of this powder, 5 g of metallic cobalt was mixed, water was added to form a paste, and the foamed nickel porous body was filled.
After drying, pressurizing and pressing under certain conditions and then cutting to the above dimensions,
A nickel positive electrode C for comparison was obtained. Using this positive electrode, an AA size sealed nickel-cadmium storage battery was produced in the same manner as in the example, and a battery C according to a comparative example was obtained.

The energy consumption per 1 Ah required for producing the nickel positive electrode used for producing these batteries is shown in (Table 1).

[0017]

[Table 1]

As is clear from (Table 1), in the process of producing nickel hydroxide in which cobalt hydroxide is produced in the surface layer, even if the drying process is omitted and only the filling process is performed as a slurry, the energy consumption is reduced to 20. %, It is possible to obtain a positive electrode having high productivity with low energy cost.

Further, these batteries were charged at 0.1 ° C. for 15 hours at a constant temperature of 20 ° C., and the cycle of discharging at 0.2 C to 1.0 V was repeated, and the battery characteristics were evaluated by the discharge capacity at the second cycle. . These results are also shown in (Table 1).
As is clear from (Table 1), in Battery A, since cobalt hydroxide was formed on the nickel hydroxide surface layer, the utilization rate was higher than that of Comparative Battery B in which cobalt hydroxide powder was added alone. This is because by forming cobalt hydroxide on the nickel hydroxide surface layer, the contact area between cobalt and nickel hydroxide is larger than when cobalt powder is added alone to the active material powder. It is considered that the improvement of the utilization rate of is extremely large. Although the foamed nickel porous body is used as the conductive substrate in this embodiment, it is needless to say that the same effect can be obtained even when the punched metal is coated with nickel.

[0020]

INDUSTRIAL APPLICABILITY As described above, the present invention does not require a drying step until filling or coating on a substrate, and further continuously produces nickel hydroxide having cobalt hydroxide formed on its surface layer. It is possible to provide a method for producing a nickel positive electrode for an alkaline storage battery, which has low energy cost, high productivity, and high performance.

[Brief description of drawings]

FIG. 1 is a flowchart showing an example of a reaction apparatus used in the present invention.

FIG. 2 is a flowchart showing a conventional nickel electrode manufacturing process.

[Explanation of symbols]

1 Reaction Tank 2 Double Partition 3 Ammonium Ion Mixed Nickel Salt Aqueous Solution Supply Line 4 Alkali Metal Hydroxide Aqueous Solution Supply Line 5 Metering Pump 6 pH Controller 7 Temperature Controller 8 Nickel Hydroxide Particle-Containing Liquid Extraction Line 9 Stirrer 10 Nickel Hydroxide Particle-containing liquid tank 11 Nickel hydroxide particle-containing liquid supply line 12 Pure water supply line 13 Circulating filtration water washing device 14 Filtrate discharge line 15 Dehydrated nickel hydroxide particle-containing liquid tank 16 Reaction tank 17 Cobalt salt aqueous solution supply line 18 Liquid supply line containing nickel hydroxide particles after dehydration 19 Reaction product take-out line

Claims (1)

[Claims] 1. An alkali metal hydroxide aqueous solution is continuously supplied to an aqueous solution of a nickel salt aqueous solution mixed with ammonium ions, the nickel hydroxide particles produced are continuously taken out, and filtration and washing are continuously performed. A cobalt salt aqueous solution and an alkali metal hydroxide aqueous solution are continuously supplied to the first step and the nickel hydroxide slurry obtained in the first step to add cobalt hydroxide to the surface layer of the nickel hydroxide. Alkali comprising a second step of continuously filtering and washing the produced slurry and water, and a third step of filling or coating the conductive substrate with the active material mainly containing the slurry obtained in the second step Manufacturing method of nickel positive electrode for storage battery.