JP3191830B2 - Method for producing nickel electrode for alkaline storage battery - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a nickel electrode for an alkaline storage battery such as a nickel-cadmium battery or a nickel-zinc battery.

[0002]

2. Description of the Related Art Conventional types of nickel electrode substrates include a sintered substrate formed by sintering nickel powder on a perforated steel plate to form a porous body, or electroplating nickel on an organic nonwoven fabric, and then forming a core material. There is a substrate or the like which has been baked to form a porous metal body. However, in the production of nickel electrodes using these substrates, for example, in the former substrate, complicated steps must be repeated a plurality of times to fill a predetermined amount of the active material.
Further, the latter substrate has a problem that the filling process is simple, but the substrate is expensive.

[0003]

Therefore, as a more inexpensive and simpler manufacturing method, there is a nickel electrode formed by using a nickel net or a punched sheet as a substrate and applying an active material thereto. Since the surface area of these substrates is smaller than that of the above-mentioned sintered type substrates and porous metal bodies, in order to obtain a high utilization rate of the active material, the connection between the active material and the substrate must be ensured. As one of the ideas,
There is a method in which nickel hydroxide, which is an active material, and a substrate (current collector) are connected to each other through high-conductivity cobalt oxyhydroxide generated at the time of charging by interposing cobalt on the surface of the substrate. Conventionally, cobalt was coated on the substrate surface by electroless plating or electroplating, but these plating methods require many man-hours, are expensive, and are intended to manufacture inexpensive electrodes, which is the original purpose. From the viewpoint, a simpler method is desired.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and in a positive electrode in which an active material of nickel hydroxide is pasted on an electrode substrate, the utilization factor and the life thereof are improved, and the productivity is reduced. An object of the present invention is to provide an excellent method for producing a paste-type positive electrode.

[0005]

Means for Solving the Problems The present invention, after being Nurigi an aqueous solution obtained by dispersing an oxide of cobalt powder to an electrode substrate surface, and performs coating of the slurry active material.

[0006]

The electrochemical oxidation reaction of cobalt monoxide to cobalt oxyhydroxide is known to occur through the following process. First, cobalt monoxide is chemically dissolved in the alkaline electrolyte. Then, the dissolved bivalent
Cobalt ions are re-deposited in the electrode as cobalt hydroxide
I do. Furthermore, the precipitated cobalt hydroxide is oxidized,
Changes to trivalent cobalt oxyhydroxide. It is known that the produced cobalt oxyhydroxide has high conductivity.

Therefore, when cobalt is interposed in the vicinity of the electrode surface, the deposition of divalent cobalt hydroxide in the above process occurs on the surface of the substrate and the active material, and the substrate and the active material are connected by the cobalt hydroxide layer. You. Since the oxidation of cobalt hydroxide to cobalt oxyhydroxide is a solid-state reaction, the substrate (current collector) and the active material are ultimately firmly connected by conductive cobalt oxyhydroxide. .

Conventionally, it was thought that it was necessary to uniformly coat the substrate surface with cobalt. However, even if a uniform layer was not necessarily formed as in the case of cobalt plating, high cobalt monoxide was deposited near the surface of the substrate. It has been found that the same effect on the improvement of the utilization rate of the active material and the life can be obtained only by interposing the concentration. Also, in the plating method, if the plating layer is too thick, it does not completely change to cobalt oxyhydroxide,
Conversely, a passivation layer of cobalt is formed to cover the entire substrate surface, which causes a reduction in utilization. Therefore, control of the plating thickness is indispensable. However, in the present invention, such a control is not required, and a simple manufacturing process is provided.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described in detail.
1 wt% aqueous solution of carboxymethyl cellulose (CMC), were mixed 45% by weight of an oxide of cobalt powder and flowing liquid, and the 2-5 mg / cm ² to nickel net of 80 mesh by a spray method is Nurigi . Next, after mixing a binder with 80% by weight of nickel hydroxide powder, 10% by weight of cobalt monoxide powder, and 10% by weight of carbon,
An aqueous solution thickened by MC was added to form a slurry.
The slurry of the active material was passed through the nickel net to which the above-mentioned cobalt monoxide was adhered, and the active material was uniformly applied to both surfaces thereof, followed by drying and pressing to produce a paste-type nickel electrode (1).

As a comparative example, a paste-type nickel electrode (II) was prepared in the same manner as described above using an untreated nickel net.
Was prepared. Similarly, a paste-type nickel electrode (III) was prepared using a nickel net plated with cobalt having a thickness of about 3 μm by electroplating as a substrate.

[0011] These paste nickel electrodes (I)
Using (III), a battery was constructed with a cadmium electrode as a counter electrode and a separator interposed therebetween. Specific gravity 1.26 for electrolyte
Was used. These batteries were charged and discharged using a mercury oxide electrode as a reference electrode, and the active material utilization rate and its cycle characteristics were examined. As shown in FIG. ) And cycle characteristics. In Comparative Example (II), the capacity was reduced early.

The present invention can be applied not only to the above-described two-dimensional current collector, but also to a three-dimensional nickel fiber substrate, a nickel foam substrate, and the like. In particular, the present invention has been found to be effective in improving high-rate discharge performance.

[0013]

As described above, according to the present invention, there is an effect that an inexpensive paste-type nickel electrode having the same performance as the conventional one can be provided by a manufacturing process which is much simpler than the conventional plating method. The value is great.

[Brief description of the drawings]

FIG. 1 shows cycle characteristics of a paste type nickel electrode according to one embodiment of the present invention and a comparative example.

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Claims (1)

(57) [Claims] 1. A an aqueous solution obtained by dispersing an oxide of cobalt,
A method for producing a nickel electrode for an alkaline storage battery, comprising applying a slurry-like active material after coating on a surface of an electrode substrate.