JPS6340255A - Sintered nickel electrode for alkaline storage battery - Google Patents

Abstract

PURPOSE:To increase the capacity and cycle performance of an electrode by covering a nickel active material layer with a cobalt compound or metallic cobalt. CONSTITUTION:A layer 1 of a cobalt compound or metallic cobalt alone is formed between a porous sintered nickel substrate 3 and a cathode active material layer 2 mainly comprising nickel hydroxide. Thereby, oxygen overvoltage in charge is decreased and charging reaction easily proceeds. A layer 5 of a cobalt compound or metallic cobalt alone is formed between the cathode active material layer 2 and an electrolyte layer 4 to cover the nickel active material layer 2. By synergetic effect of two cobalt layers, the retarding effect on theta-NiOOH is heightened and cycle performance is increased.

Description

DETAILED DESCRIPTION OF THE INVENTION (() Industrial Applicability) The present invention relates to a sintered nickel electrode for alkaline storage batteries, which is used as a positive electrode for nickel-cadmium batteries, nickel-zinc batteries, and the like.

1) Conventional technology The nickel electrode used in conventional alkaline storage batteries is a porous material obtained by coating a core with a slurry of carbonyl nickel powder, polymer paste, and sintering this in a reducing atmosphere. The nickel substrate is immersed in an impregnating solution containing nickel nitrate as its main component, then treated with alkali, and the pores of the substrate are filled with nickel hydroxide active material.The process is repeated several times. Various studies have been conducted to improve the battery characteristics of hexa-alkaline storage batteries using this nickel electrode.

In order to improve this battery characteristic, especially to increase the battery capacity by 1, it is necessary to develop a nickel electrode with a high energy density per unit volume, and the basic method for this purpose is to improve the utilization rate of the active material. Various methods have been proposed to improve energy density and obtain high energy density, including a method using hydroxide and nickel and cobalt simultaneously precipitated from a nitric acid solution, as described in Japanese Patent Publication No. 57-5018. Although not described in the publication, a method has been proposed in which a single layer of cobalt is provided using an impregnating liquid in which the cobalt content is higher than the nickel content in an active material impregnation neutralization process u. However, the above method has the problem that the effect of adding Konoruto is still insufficient, and as the cycle progresses, the plate strength decreases, leading to a decrease in cycle performance.

(c) Problems to be Solved by the Invention The present invention increases the electrode capacity by improving the utilization rate of the nickel electrode, and also provides a sintered material for alkaline storage batteries that has high electrode plate strength and excellent cycle characteristics. nickel electrode.

(ii) A means for solving the problem The present invention provides a layer in which a cobalt compound or gold-cobalt exists alone between a porous nickel substrate and a nickel active material layer, and also provides By providing a layer in which a cobalt compound or metallic cobalt exists alone between the electrolyte layer and the electrolyte layer, the above-mentioned nickel active material]
A sintered nickel electrode for an alkaline storage battery characterized by being coated with a cobalt compound or metal cobalt.

Note that methods for forming a layer in which a cobalt compound or metallic cobalt exists alone include chemical impregnation methods;
Any method such as a thermal decomposition method or an electrodeposition method may be used. Further, the cobalt compound is preferably a hydroxide or an oxide.

(e) Function By providing a layer in which a cobalt compound or metallic cobalt exists alone between the sintered porous nickel substrate and the anode active material layer containing nickel hydroxide as a main component, oxygen The overvoltage decreases and the charging reaction progresses more easily. Furthermore, by providing a layer in which a cobalt compound or metallic cobalt exists alone between the cobalt 1, the anode active material layer, and the electrolyte layer, the synergistic effect of these two cobalt layers can be achieved by coating the nickel active material layer. Based on γ-Nio
The suppressing effect of oH is further improved, the generation of γ-NioH is almost eliminated, and β-NioO! ! Furthermore, the presence of the two cobalt layers makes it easier for the charge/discharge reaction to proceed, resulting in a nickel electrode with excellent cycle characteristics.

Sixth, the surface of the porous nickel substrate of the present invention is improved to the extent that a cobalt compound or metallic cobalt exists alone.

(f) Example An embodiment of the present invention will be described in detail below with reference to FIG.

A sintered porous nickel substrate 3 with a porosity of 80 cm and a specific gravity of L3
After being immersed in the aqueous cobalt nitrate solution of No. 8, it is dried in air at 80° C. and then heat treated in air at 210° C. to form the first cobalt oxide layer 1 on the surface of the substrate and the inner surface of the pores. Next, the process of impregnating this substrate with an aqueous nickel nitrate solution, treating it with alkali, and filling it with a nickel active material was repeated six times to form a predetermined amount of active material layer 2, and then it was re-immersed in an aqueous cobalt nitrate solution with a specific gravity of L38. 80℃ in air
After drying with hydroxide at 80° C.), alkali treatment is performed with an aqueous IJ solution to form a second cobalt hydroxide layer 5 covering the nickel active material, which is combined with a known cadmium electrode to a nominal volume of @L, 2 AH's nickel-cadmium battery, and the invention of the battery.

Comparative Example 1 The same substrate as No. 6 used in Example 1 was immersed in a cobalt nitrate aqueous solution with a specific gravity of L38, dried in air at 80°C, and then immersed in air at 2
A cobalt oxide layer was formed by heat treatment at 10° C., and a comparative battery B was assembled in the same manner as in Example 1, using a nickel active material filled with a nickel active material in the same manner as in Example 1, and using only nickel electrodes. Nine points.

Comparative Example 2 The same substrate used in Example 1 was directly filled with a nickel active material in the same manner as in Example 1, then immersed in an aqueous cobalt nitrate solution with a specific gravity of L38, dried in air at 80°C, and then soaked in water at 80°C. Comparative battery C was obtained by performing alkali treatment with an aqueous sodium oxide solution to form a cobalt hydroxide layer, and assembling the battery in the same manner as in Example 1, using a nickel electrode as the base.

Comparative Example 3 The same substrate used in Example 1 was directly filled with nickel active material in the same manner as in Example 1, and a comparative battery was assembled in the same manner as in Example 1 using a nickel electrode without cutting the cobalt layer. Good deal.

FIG. 2 shows the results of X-ray diffraction analysis, and it is clear that the nickel electrode according to the present invention has a charge product γ that is difficult to discharge.
It can be seen that almost no -Ni OOH is generated, and only β-NiOOH, which is easily discharged, is generated, and the utilization rate can be improved.

Furthermore, Table 1 shows the present invention battery A1 and comparative batteries B and C.

Nickel valence and valence change before and after charging and discharging D, and KXm
Diffraction (7) Considering the height ratio of γ-Ni0OH, β-NiOOH and Nohik as the production ratio, the
Expressed as 0OH.

Table 1 From the results, the change in nickel valence of battery A of the present invention was 1.2.
and 1) are also large, indicating that the charge/discharge reaction is progressing even further. Furthermore, γ-NiOOH and β-N
iOOH raw Fi2 ratio γ-LNiOOH//3-Ni
Looking at 0OH, only the β type was produced in the battery A of the present invention, which was washed with Niracool.

The 31st row for masu uses the nickel electrodes of the batteries A, B, C, and II, and the counter electrode is a nickel plate, and the electrolyte specific gravity L
The graph shows the results of a cycle test using a KOH solution of No. 23 and charging at a charging current of 1201 A for 16 hours, followed by a discharge current of 1200 yxA and a final voltage of -1 V with respect to the reference electrode (Hg/111 qO) K. This shows that the electrode of the present invention has excellent cycle characteristics due to the synergistic effect of the two cobalt layers.

On the other hand, FIG. 4 shows the batteries A, B, C, and D at a temperature of 0. This is a graph showing the discharge characteristics when the battery was charged with IC (120% A) for 16 hours and then discharged with IC (1200% A) at 25°C. Since the utilization rate of nickel active material is high, high capacity is being achieved.

Furthermore, Fig. 5 shows a comparison of the cycle characteristics during running using the batteries A, B, C, and D, which were charged at 25°C for 16 hours at Q and Ic, and then discharged at Shima C. Nickel electrodes exhibit excellent cycle characteristics and are durable even when assembled into batteries.

In the examples, the cobalt layer formed on the substrate surface is in the form of an oxide, but even hydroxide (copal) 1 is not inferior in terms of the effects of the present invention.

However, the oxide layer is stronger and superior to the hydroxide layer in terms of the effect of preventing nickel attack during impregnation with the active material.

(G) Effects of the Invention According to the present invention, since the generation of γ-NiOOH can be suppressed very effectively, a sintered nickel electrode for alkaline storage batteries with excellent cycle characteristics and high capacity 1 can be provided, which has industrial value. is extremely large.

[Brief explanation of the drawing]

Figure 1 is an enlarged cross-sectional view of the main part of the nickel electrode of the present invention, Figure 2 is X-ray diffraction 1·η, brush 31i4 is a cycle characteristic comparison diagram of nickel electrodes, Figure 4 is a discharge characteristic ratio diagram, brush 5 is indicates a comparison of battery cycle characteristics m. A...Battery of the present invention, B, C, D...Comparison battery, 1°5...Cobalt layer, 2...Nickel active material layer, 3.
... Sintered porous nickel substrate, 4... Electrolyte layer.

Claims (1)

[Claims] (1) A layer in which a cobalt compound or metallic cobalt exists alone is provided between the porous nickel substrate and the nickel active material layer, and a cobalt compound or metallic cobalt is provided between the nickel active material layer and the electrolyte layer. A sintered nickel electrode for an alkaline storage battery, characterized in that the nickel active material layer is coated with a cobalt compound or metal cobalt by providing a layer that exists alone.