JPH07120530B2 - Method for manufacturing sintered nickel substrate for alkaline battery - Google Patents

Description

The present invention relates to a method for manufacturing a sintered nickel substrate for an alkaline battery, and an object thereof is to increase the porosity of the nickel substrate.

The method of manufacturing an alkaline battery electrode is roughly classified into a sintering type,
There are 3 types: paste type and pocket type.

Currently, the most widely used method for small and closed nickel-cadmium storage batteries is the sintering method, which is expensive but has high capacity and long life. Sintered nickel substrates used as a support and a current collector for an active material of a sintered electrode are mainly manufactured by the following method. One of them is to spread carbonyl nickel in a heat-resistant mold such as graphite, then place a core metal such as nickel mesh, and further spread carbonyl nickel powder on both sides of the nickel mesh, and then remove excess powder. It is a loose sintering method in which the surface of powder dispersion is flattened and sintered in a non-oxidizing atmosphere. The other is to coat carbon nickel powder, solvent such as water, binder such as carboxymethyl cellulose or methyl cellulose, and thickening agent, which is a highly viscous nickel slurry, onto a core such as nickel net or nickel-plated perforated steel sheet. It is a slurry method in which after being deposited, it is dried and then sintered.

In the production of a sintered nickel substrate by the loose sintering method, sintering is started from a state in which carbonyl nickel powder is dispersed in a heat-resistant mold, that is, a state in which the bulk specific gravity of carbonyl nickel powder is close. Nickel powder with a large bulk specific gravity that is generally used industrially is Carbonyl Nickel "Type 255" manufactured by Inco, and its bulk specific gravity is 0.5 ~
The porosity of this state is 0.65, and the true density of nickel is 8.
At 85 g / cm ³ , this corresponds to 94.4-92.7%. Since the porosity decreases from this state due to sintering, the maximum value of the porosity of the sintered nickel substrate by the loose sintering method is about
It was 90%.

On the other hand, in the production of a sintered nickel substrate by the slurry method, the carbonyl nickel powder that holds a small bulk specific gravity in a three-dimensionally thinly stretched form during mechanical kneading of the nickel slurry is mechanically destroyed, Due to the large nickel powder, the maximum porosity of the sintered nickel substrate has been about 85%.

As described above, the porosity of the sintered nickel substrate manufactured by the loose sintering method or the slurry method has been conventionally controlled by considering the sintering temperature, the sintering time, the form of the raw nickel powder and the bulk specific gravity.

In order to manufacture a sintered electrode of high capacity density, it is necessary to use a highly porous sintered nickel substrate, and in order to manufacture a highly porous sintered nickel substrate, as described above. The loose sintering method is more advantageous than the slurry method, but industrially, the sintered nickel substrate is mainly manufactured by the slurry method from the viewpoint of workability.

As a method for controlling the porosity of a sintered nickel substrate, the present invention is a result of studying the amount of nickel in the nickel slurry in the slurry method in addition to the sintering temperature, the sintering time, the form and bulk density of the raw nickel powder. This is based on the finding that it is possible to manufacture a substrate having a high porosity of about 90 to 95%, which has not been obtained conventionally, by selecting the sintering conditions.

The result of the study on the amount of nickel in the slurry according to the present invention is shown in FIG. FIG. 1 shows the effect of the amount of nickel in the nickel slurry and the sintering conditions on the porosity of the sintered nickel substrate when using a carbonyl nickel powder having a bulk specific gravity of 0.50. Sintering was performed in H ₂ atmosphere. In the figure, A is a coated product, B is a dried product, and C to E are sintered products (C ...
(800 ℃ for 5 minutes, C… 900 ℃ for 3 minutes, E… 1000 ℃ for 1 minute)
Represents the porosity of the.

In the production of a sintered nickel substrate by a slurry method in which a nickel slurry is applied to a core body such as a perforated steel sheet and then dried and sintered, evaporation of a solvent such as water due to drying and the distance between nickel particles due to sintering are controlled. The shrinkage reduces the porosity of the slurry coating.

The state in which carbonyl nickel powder was sprayed in the mold in the loose sintering method corresponds to the dried state of the nickel slurry coating in the slurry method (B in FIG. 1),
The porosity in this state of the loose sintering method cannot be higher than that corresponding to the bulk specific gravity of nickel powder, but the porosity of this state in the slurry method is affected by gravity due to the action of a binder such as carboxymethyl cellulose or methyl cellulose. Since it can be reduced, it can be made more than that corresponding to the bulk specific gravity.

According to the present invention, for these reasons, a sintered nickel substrate having a high porosity of 90% or more, which could not be produced by the loose sintering method, can be produced by an industrially useful slurry method.

As is clear from the figure, when a carbonyl nickel powder having a volume of 2 to 6% in a nickel slurry is sintered at a temperature of 800 to 950 ° C, a sintered body having a porosity of 90 to 95% can be obtained. . When the volume of the carbonyl nickel powder in the slurry is less than 2%, the dried body can be obtained, but the decomposed binder causes the dried body to collapse during the sintering process. I couldn't do it. Also, the sintering temperature is 10
At temperatures above 00 ° C (E in Fig. 1), the bond between nickel particles grows faster during sintering than at 800 ° C (Fig. 1C) or 900 ° C (Fig. 1D), and In the region where the volume of carbonyl nickel powder is small, the resistance to shrinkage of the distance between nickel particles is also small, so the shrinkage due to sintering is significantly large, and a sintered body with a porosity of 90% or more cannot be obtained. It was

Inco Carbonyl Nickel Powder, Type 255, has a bulk specific gravity of 0.50 to 0.65. Fig. 1 shows the case of using a carbonyl nickel powder having a bulk specific gravity of 0.50, but using a carbonyl nickel powder having a bulk specific gravity of 0.65. Even if there is, a relationship similar to that shown in FIG. 1 can be obtained.

As described above, according to the present invention, the volume of the carbonyl nickel powder in the nickel slurry is 2 to 2 by the slurry method.
It is possible to manufacture a sintered nickel substrate having a high porosity of 90 to 95% by sintering 6% of it at a temperature of 800 to 950 ° C. in a non-oxidizing atmosphere.

Next, production of a sintered nickel substrate for an alkaline battery according to the present invention will be described based on examples.

[Example 1] Carbonyl nickel powder Type 255 (bulk specific gravity) manufactured by Inco
0.50) 3 Kg is slurried with 10% 3% aqueous solution of carboxymethyl cellulose.

The slurry was applied to a perforated steel plate plated with nickel as a core material, dried, and then sintered in an H ₂ atmosphere at 800 ° C. for about 5 minutes to obtain a substrate having a porosity of about 94% (see FIG. 1).

[Example 2] Carbonyl nickel powder Type 255 (bulk specific gravity) manufactured by Inco
0.50) 5 kg are slurried with 10% 3% aqueous solution of carboxymethyl cellulose.

The slurry was applied to a perforated steel plate plated with nickel as a core material, dried, and then sintered in an H ₂ atmosphere at 900 ° C. for about 3 minutes to obtain a substrate having a porosity of about 90% (see FIG. 1).

FIG. 2 shows a process flow chart of a method for producing a typical sintered nickel substrate of the present invention.

Effects of the Invention As described above, according to the method of the present invention, in the production of a sintered nickel substrate by a slurry method, a carbon slurry having a carbonyl nickel powder content of 2 to 6% in a non-oxidizing atmosphere is used in a non-oxidizing atmosphere. 90 ~ 95 by sintering at the temperature of ~ 950 ℃
% High porosity substrates can be obtained. Then, by using this high porosity body and filling the active material by a chemical impregnation method, it becomes possible to obtain an electrode for a high capacity density alkaline battery, which has a great industrial value.

[Brief description of drawings]

FIG. 1 is a diagram showing the effect of the amount of nickel in the nickel slurry and the sintering conditions on the porosity of the sintered nickel substrate according to the present invention, and FIG. 2 is the manufacturing process of the sintered nickel substrate according to the present invention. FIG.

Claims (2)

[Claims] 1. A nickel slurry comprising a mixture of carbonyl nickel powder and an aqueous solution of an organic polymer such as carboxymethyl cellulose or methyl cellulose is applied to both surfaces of a porous metal core, dried, and then baked in a non-oxidizing atmosphere. A method for producing a sintered nickel substrate for an alkaline battery, which is used as an electrode for filling an active material by a chemical impregnation method into a sintered nickel substrate for an alkaline battery, which has a step of bonding, and comprising a volume of carbonyl nickel powder in a slurry. Is 2-6%
A method of manufacturing a sintered nickel substrate for an alkaline storage battery, characterized in that 2. The method for producing a sintered nickel substrate for an alkaline battery according to claim 1, wherein the slurry is sintered at a temperature of 800 to 950 ° C.