JP2865391B2 - Method for producing nickel hydroxide electrode for alkaline storage battery - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Industrial Field of the Invention The present invention relates to a method for impregnating a porous nickel sintered substrate with an acidic nickel salt such as nickel nitrate, and then subjecting the substrate to an alkali treatment or the like. The present invention relates to a method for producing a nickel hydroxide electrode for an alkaline storage battery filled with an active material.

(B) Conventional technology As a method for manufacturing a nickel hydroxide electrode for an alkaline storage battery, a porous nickel sintered substrate as an active material holding body is immersed in an acidic nickel salt impregnating liquid such as nickel nitrate, and is placed in a hole of the substrate. There is a method of manufacturing a nickel hydroxide electrode by performing an active material filling operation in which a nickel salt is impregnated and then converted into an active material by converting the nickel salt into nickel hydroxide in an alkali. In this active material filling operation, a sufficient amount of the active material cannot be filled in the nickel sintered substrate by one operation, and therefore, the necessary amount of the active material must be filled by repeating the operation several times. Therefore, in order to increase the filling efficiency of the active material and to simplify the manufacturing process, it is necessary to use a molten salt impregnating liquid such as a high-temperature high-concentration nickel nitrate aqueous solution as the impregnating liquid to obtain a required amount of the active material with a small number of impregnations. However, in this case, the impregnating solution has a strong corrosiveness, and the substrate is eroded, and nickel is dissolved, so that the electrode plate becomes brittle and the cycle performance deteriorates.

On the other hand, if the porous nickel sintered substrate is immersed in an aqueous solution of cobalt nitrate and then heat-treated at a temperature of 150 ° C. or higher, the cobalt nitrate changes into cobalt tetroxide, and the corrosion resistance of the substrate can be improved. . However, when cobalt nitrate is heated above 150 ° C, cobalt nitrate is decomposed,
Nitric acid gas is generated. Therefore, it is difficult to control the process, and the heat treatment temperature becomes high, so that the cost required for the process is further increased.

In JP-A-62-37875, a porous nickel sintered substrate is immersed in an aqueous solution of cobalt nitrate, dried sufficiently at 80 ° C., and then immersed in an aqueous solution of sodium hydroxide to produce cobalt hydroxide. Then, a method has been proposed in which the cobalt hydroxide is changed to cobalt oxide by performing anodic oxidation to coat the surface of the porous nickel sintered substrate with a cobalt oxide layer to prevent corrosion of the substrate. However, the drying temperature after immersion in the aqueous solution of cobalt nitrate has a great effect on the electrode performance after the impregnation of the active material, and even when the electrode is dried at the above temperature, a sufficient effect has not yet been obtained.

(C) Problems to be Solved by the Invention The present invention finds an optimum value of a drying temperature after immersing a porous nickel sintered substrate in an aqueous solution of cobalt nitrate, and shows a discharge characteristic with a large battery capacity and a high operating voltage. An object of the present invention is to provide a manufacturing method capable of obtaining a nickel hydroxide electrode for an alkaline storage battery.

(D) Means for Solving the Problems In the method for producing a nickel hydroxide electrode for an alkaline storage battery of the present invention, a porous nickel sintered substrate is immersed in a cobalt salt solution and dried at a temperature of 90 ° C to 100 ° C. Thereafter, the substrate is treated with an alkaline solution to generate cobalt hydroxide, and after oxidizing the cobalt hydroxide, the substrate is subjected to an active material filling operation involving impregnation with an acidic nickel salt.

(E) Action After the porous nickel sintered substrate is immersed in an aqueous solution of cobalt nitrate, dried in a temperature range of 90 ° C to 100 ° C, and treated with an aqueous alkaline solution, the nickel electrode obtained at a temperature other than the above drying temperature Compared with the plate, the nickel plate of the present invention has a higher capacity and a higher operating voltage.

(F) Example [Example] After immersing a porous nickel sintered substrate in an aqueous solution of cobalt nitrate having a specific gravity of about 1.4, the substrate was dried at 90 ° C and 100 ° C, and then immersed in an aqueous solution of sodium hydroxide. To produce cobalt hydroxide. By using the substrate on which the cobalt hydroxide was generated in this manner as an anode and applying an amount of electricity of 150% of the theoretical capacity of the generated cobalt hydroxide to the substrate surface in an alkaline aqueous solution of potassium hydroxide over 30 minutes, The cobalt hydroxide was changed to cobalt oxide, and the surface of the porous nickel sintered substrate was covered with a cobalt oxide layer.

Thereafter, the substrate is immersed in an aqueous solution of nickel nitrate having a specific gravity of 1.75 ° C. at 80 ° C., and a series of active material filling operations for converting nickel nitrate impregnated in the substrate to nickel hydroxide in an aqueous solution of sodium hydroxide to form an active material are performed. This was repeated five times to produce a nickel positive electrode.

Next, the nickel positive electrode was combined with a cadmium negative electrode having a sufficiently larger capacity than the positive electrode, and a nickel-cadmium battery having a nominal capacity of 1200 mAH was prepared using an aqueous solution of potassium hydroxide as an electrolytic solution. Of the batteries thus produced, those having a drying temperature of 90 ° C. after immersion in the above-mentioned cobalt nitrate are referred to as Battery A of the present invention, and those having a drying temperature of 100 ° C. are referred to as Battery B of the present invention.

(Comparative example)

In the above example, the drying temperature after immersion of the substrate in an aqueous solution of cobalt nitrate performed during the preparation of the positive electrode was 60 ° C., 80 ° C. and 120 ° C.
A battery was prepared in the same manner as in the above example except that the temperature was changed to ° C., and the batteries thus prepared were referred to as comparative batteries C, D, and E, respectively.

The batteries A to E are supplied with a current of 0.1 C of nominal capacity (120 m
A) After charging for 16 hours, the nominal capacity of 1C current (1200m
In FIG. 1A, the battery was discharged until the battery voltage reached 1.0 V. The discharge curve of each battery at this time is shown in FIG. In the drawing, reference numerals A to E correspond to batteries A to E, respectively. Table 1 shows the battery capacity and average operating voltage of each battery.

From FIG. 1 and Table 1, it can be seen that the batteries A and B of the present invention have larger battery capacity and higher average operating voltage than the comparative batteries C, D and E, and show excellent discharge characteristics. I understand.

(G) Effect of the Invention The method for producing a nickel hydroxide electrode for an alkaline storage battery of the present invention comprises immersing a porous nickel sintered substrate in a cobalt salt solution and then drying the substrate at a temperature of 90 ° C to 100 ° C. It is possible to provide a nickel hydroxide electrode for an alkaline storage battery, which has a high average operating voltage and excellent discharge characteristics.

[Brief description of the drawings]

FIG. 1 is a view showing a discharge curve of a battery using an electrode according to the present invention and a comparative electrode. A, B: battery of the present invention, C, D, E: comparative battery.

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Claims (1)

(57) [Claims] 1. A porous nickel sintered substrate is immersed in a cobalt salt solution, dried at a temperature of 90.degree. C. to 100.degree. C., and treated with an alkaline solution to produce cobalt hydroxide. Oxidizing the substrate, and then performing an active material filling operation involving impregnation of the substrate with an acidic nickel salt.