JPS62281268A - Manufacture of cathode plate for alkaline storage battery - Google Patents

Abstract

PURPOSE:To enlarge cathode capacity, by corroding a sintered nickel surface layer in an aqueous solution of raw-material salt so that it becomes an active material. CONSTITUTION:A sintered nickel surface layer is corroded in an aqueous solution of raw-material salt to become an active layer. And corrosion is promoted by heat decomposition of the raw-material salt so that the sintered nickel surface layer becomes an active material. Because the aqueous solution of raw- material salt is strong in acidity, its contact with sintered nickel particles on the sintered substrate causes a corroding reaction to raise PH in the vicinity of the reacting interface and then to generate NiOH(NO3) on the reaction surface, so that it becomes Ni(OH)2 by alkaline substitution. The corrosion layer formed of the sintered nickel particles is hence made to become the active material so that the capacity can be enlarged. Besides, corrosion reaction can be promoted by heating the raw-material salt in the small hole of the substrate after the preceded corrosion reaction.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention Field of Industrial Application The present invention relates to an improvement in a method for manufacturing an anode plate for a high capacity alkaline storage battery.

Conventional Technology As the capacity of alkaline storage batteries increases, it has become essential to increase the capacity of the anode plate. In order to increase the capacity of the anode plate, it is necessary to increase the filling amount of the active material or the utilization rate of the active material, or to improve both. As a countermeasure for the former, methods include increasing the porosity of the sintered nickel substrate to increase the amount of active material filled, and using a metallic nickel porous material with a three-dimensional network structure as an active material holder instead of the sintered nickel substrate. A method has been proposed to increase the amount of active material filled. On the other hand, a method for improving the utilization rate of the active material is to add cobalt to the active material.

Problems to be Solved by the Invention Among the above manufacturing methods, the method of increasing the porosity of the sintered substrate and the metal nickel porous body having a three-dimensional network structure increase the amount of active material filled, but the nickel density within the substrate increases. Because of the low resistance, the mechanical strength of the substrate is not sufficient, and the electrode plate is easily cracked when wound, and the current collecting property is also poor.

Furthermore, when cobalt is added, the amount of cobalt hydroxide in the active material increases, causing swelling of the active material and a decrease in discharge voltage.

Means for Solving the Problems The present invention eliminates the above-mentioned drawbacks by corroding the sintered nickel surface layer in an aqueous raw material salt solution to make it an active material, and increasing the corrosion due to thermal decomposition of the raw material salt. The sintered nickel surface layer is made into an active material.

Since the active raw material salt aqueous solution is strongly acidic and contains C, when it comes into contact with the sintered nickel particles of the sintered substrate, a corrosion reaction occurs, the pH near the reaction interface increases, and NIOH (N
) is formed, and alkali substitution 1 results in N i
(OH) , the corroded layer of the sintered nickel particles becomes an active material and the capacity can be improved.

Furthermore, by heating the raw material salt in the pores of the substrate after the corrosion reaction, the corrosion reaction can be accelerated.

The example raw material salt aqueous solution includes a nickel nitrate aqueous solution containing 1 to 10 wtcfI of cobalt nitrate or cadmium nitrate (
Specific gravity 1.70 at liquid temperature 50'C. PH1), and a 20Wt=1 sodium hydroxide aqueous solution was used as the alkaline aqueous solution.

Experiment 1 A sintered nickel substrate (50
After washing each substrate with water and dissolving the hydroxide, the amount of corrosion of the sintered nickel was measured. This result is shown in the it diagram. It can be seen from the figure that the corrosion rate of sintered nickel increases as the immersion time increases. It can also be seen that the corrosion rate increases further by thermal decomposition.

Note that the effect of immersion time becomes constant at 60 minutes.

Experiment 2 A sintered nickel substrate was immersed in a raw salt aqueous solution for 60 minutes,
A series of chemical impregnation operations including thermal decomposition, alkali substitution, and water washing were repeated several times. After the impregnation was completed, the active material was dissolved and the amount of corrosion of the sintered nickel was measured. The results are shown in FIG. From FIG. 2, it can be seen that the corrosion rate of sintered nickel decreases as the number of impregnations increases, and corrosion of sintered nickel does not occur after the number of impregnations after 4 times.

Experiment 3 An electrode plate impregnated under the same conditions as in Experiment 2 was placed in an excess electrolyte (20 W t 4 sodium hydroxide aqueous solution, 20'C) using a nickel plate as a counter electrode, at a temperature of 0.2 C compared to the theoretical capacity! The battery was charged for 10 hours at a temperature of 0.20, then discharged at a temperature of 0.20, and the capacity was measured.

The results are shown in FIG. From Figure 3, the utilization rate during discharge, including evidence of active material conversion due to corrosion A of sintered nickel, is approximately 1.
16 Unfortunately, if nickel hydroxide is deposited in the pores of a sintered nickel substrate without causing corrosion of the sintered nickel, the discharge rate of 8 needles will be improved by about 40 mm compared to B. According to the present invention, when filling a sintered nickel substrate with an active material, the C sintered nickel is corroded by an aqueous solution of raw material salt, or the raw material salt in the pores of the substrate is removed after corrosion is caused. Thermal decomposition further increases corrosion, thereby significantly increasing the anode capacity, and has extremely great industrial value.

[Brief explanation of the drawing]

Figure 1 is a curve diagram showing the relationship between the immersion time and the corrosion rate of sintered nickel when a sintered nickel substrate is immersed in one raw salt aqueous solution, and Figure 2 is a curve diagram showing the relationship between the number of times of impregnation and the corrosion rate of sintered nickel. FIG. 3 is a curve diagram showing the relationship between the number of impregnations, the capacity of the anode plate, and the utilization rate.

Claims (1)

[Claims] 1. Impregnation of an anode plate for an alkaline storage battery by immersing a sintered nickel substrate in an aqueous raw salt solution, and then depositing the hydroxide of the raw salt as an active material in the pores of the substrate in an aqueous alkaline solution. A method for producing an anode plate for an alkaline storage battery, the process comprising corroding a sintered nickel surface layer in an aqueous solution of raw material salt to convert it into an active material. 2. After the corrosion of the sintered nickel with the raw salt aqueous solution, the substrate is heated above the thermal decomposition temperature of the raw salt to thermally decompose the raw salt in the pores of the substrate, thereby further increasing the corrosion of the sintered nickel surface layer. A method for producing an anode plate for an alkaline storage battery, characterized in that: