JPS603861A - Manufacture of positive plate for alkaline storage battery - Google Patents

Abstract

PURPOSE:To increase the utilization rate of a positive active material and enable the number of pollution-preventing installations to be decreased so as to reduce the manufacturing cost of a positive plate for an alkaline storage battery by decreasing the temperature of thermal decomposition during the process of impregnating a base plate with the positive active material so as to suppress generation of a nitrogen oxide. CONSTITUTION:In the process of impregnating a base plate with an active material to make a positive plate, the temperature of thermal decomposition is decreased in order to suppress generation of a nitrogen oxide. For instance, a porous sintered base plate is immersed in molten nickel nitrate containing cobalt nitrate at 80-100 deg.C for about five minutes so as to cause the holes of the base plate to be impregnated with nickel nitrate. Following that, the thus treated base plate is heated in the air at about 100 deg.C (conventional temperature, 180-250 deg.C) to perform thermal decomposition. After the completion of the decomposition, the base plate is immersed in aqueous alkali solution at 60-70 deg.C so as to cause nickel hydroxide used as an active material to deposit in the holes of the base plate. After that, the base plate is washed with flowing water until the alkali component contained in the holes is removed, then the washed base plate is dried. The above operations are repeated 3-5 times so as to impregnate the base plate with a given amount of the active material.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an impregnation process for anode plates of alkaline storage batteries.

Conventionally, a melt impregnation method has been used as a method for impregnating an anode active material of an anode plate of an alkaline storage battery.

The melt impregnation method is a method in which a molten salt is impregnated and then thermally decomposed, and the impregnation process is simple. That is, the porous sintered substrate was heated to 80-1 containing cobalt nitrate.
The substrate is immersed in molten nickel nitrate at 00° C. for about 5 minutes to impregnate nickel nitrate into the pores of the substrate. Subsequently, this substrate is heated to 180 to 250 C in air to thermally decompose it. After thermal decomposition, the substrate is immersed in an alkaline aqueous solution at 60 to 70°C to impregnate and precipitate the active material nickel hydroxide into the pores of the substrate, washed under running water until the alkaline component in the pores disappears, and dried. Do the following. This operation is repeated 3 to 5 times to impregnate the desired active material.

However, according to this method, during pyrolysis.

Decomposition of nitrate radicals damages the substrate, resulting in a low active material utilization rate and the need for a pollution prevention device to remove nitrogen oxides, which has drawbacks in terms of electrode plate characteristics and manufacturing costs.

The present invention eliminates the above drawbacks and improves the active material utilization rate and reduces manufacturing costs by lowering the intermediate drying temperature.

FIG. 1 is a curve diagram showing the results of differential thermal analysis and thermogravimetric analysis of molten nickel nitrate impregnated into a porous sintered substrate. 1 shows the thermal decomposition curve obtained by thermogravimetric analysis, and 2 shows the differential thermal refraction curve i.

Impregnated nickel nitrate has a thermal decomposition temperature of 180-2
In temperature range 3 of 50° C., it becomes an intermediate compound and generates nitrogen oxide according to the following reaction formula.

2 N j (Now) t・6H10→2Ni (O
H) NOs+2NO,+5H,O+7°・When the temperature reaches 5 or higher, it becomes inactive nickel oxide.

Therefore, in order to compare and study the influence of the difference between the temperature range 3 of 180° to 250°C and the temperature range 4 below this,
Pyrolysis temperatures of 100°C and 200°C were chosen.

FIG. 2 is a curve diagram showing the relationship between the thermal decomposition time and the amount of impregnation. In order to assemble the battery and test the performance of the battery, the battery type is NR-8C, a sealed nickel Φ cadmium storage battery, and the results shown in Figure 2 and below are shown. In the case of the conventional thermal decomposition temperature of 200° C., impregnation occurs in a short time, but the impregnation does not increase even if the thermal decomposition time becomes longer.

However, when the pyrolysis temperature is 100℃, the amount of impregnation increases as the pyrolysis time becomes longer, and at the conventional time of 1 hour, the amount of impregnation is slightly larger when the pyrolysis temperature is 100℃. .

FIG. 3 is a curve diagram showing the relationship between thermal decomposition time and active material utilization rate. Conventional pyrolysis temperature.

In the case of 200°C, as the thermal decomposition time becomes longer, the active material utilization rate decreases, and in the case of a thermal decomposition temperature of 100°C, conversely, the thermal decomposition time becomes longer (and the active material utilization rate increases). In the conventional time, one hour, it is recognized that the difference between the two is about 15%.

Figure 4 shows how a battery is assembled using an anode plate made at pyrolysis temperatures of 100°C and 200°C, a cathode plate with a capacity more than twice that of the anode plate, and an aqueous potassium hydroxide solution as an electrolyte. It is a curve diagram showing the relationship between discharge capacity and thermal decomposition time in 0.2 C discharge.

,,,,□,,1200'C(7)□,2□□,. 1
Although the discharge capacity increases in a short period of time, it is observed that the discharge capacity decreases as the thermal decomposition time increases.When the thermal decomposition temperature is 100°C, the discharge capacity increases as the thermal decomposition time increases. It can be seen that when the thermal decomposition time is 1 hour, the amount is greater than when the temperature is 200°C.

As described above, according to the present invention, the utilization rate of the anode active material is improved, and the battery performance is improved compared to the conventional one.
In addition, production costs are reduced due to the elimination of the production of nitrogen oxides that were previously generated, and the reduction of pollution prevention equipment.
Their effects are enormous.

[Brief explanation of drawings]

Figure 1 is a curve diagram showing the results of differential thermal analysis and thermogravimetric analysis of nickel nitrate, 1 is the thermal decomposition curve by thermogravimetric analysis, 2
3 shows a differential thermal analysis curve, 3 shows a temperature range of 180°C to 250°C, 4 shows a temperature range lower than 3, and 5 shows a temperature range higher than 3. Figure 2 is a curve diagram showing the relationship between thermal decomposition time and amount of impregnation.
The figure is a curve diagram showing the relationship between thermal decomposition time and active material utilization rate.
FIG. 4 is a curve diagram showing the relationship between battery discharge capacity and thermal decomposition time. 1 is the thermal decomposition curve determined by thermogravimetric analysis, 2 is the differential thermal analysis curve, and 3 is the ff! of 180 to 250°C. I't) Solution temperature range, 4 is the temperature range below temperature range 3, 5 is the temperature range above temperature range 3 Patent applicant Figure 2 Time (Tl) Figure 3 Figure 4 Time (Koshiki π)

Claims (1)

[Claims] In the process of impregnating the anode active material of the anode plate of an alkaline storage battery,
A method for producing an anode plate for an alkaline storage battery, which is characterized by lowering the thermal decomposition temperature and suppressing the generation of nitrogen oxides.