JPH061697B2 - Manufacturing method of cadmium plate for alkaline storage battery - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a negative electrode plate for an alkaline storage battery, and more particularly to a slurry-filled cadmium electrode plate.

Conventional technology and its problems Conventionally, as a cadmium negative electrode plate for an alkaline storage battery, a sintered electrode plate in which an active material is filled in a porous substrate obtained by sintering nickel powder into a perforated steel plate or a nickel net is well known. ing. This porous substrate is obtained by sintering nickel powder on a perforated steel plate, a nickel net, or the like, and the bond between the nickel powder particles is weak. It is the limit.

Since these sintered porous substrates have weak bonding between nickel powder particles, there is a drawback that a core metal such as a perforated steel plate and a nickel net is always required, and the amount of the active material filled per unit volume is reduced by the core metal volume. Have

Furthermore, since the pores of the porous body are made of fine pores of 10 μm or less, the filling method is limited to the solution impregnation method in which complicated steps are repeated.

As an attempt to improve these drawbacks, various methods have been investigated, for example, a method of directly filling an active material into a mat-like porous body of an alkali-resistant metal fiber having an average pore size of about 40 μm and having no cored bar. When it was attempted to fill the conventional active material paste into this porous body, the paste liquid was filled only in the vicinity of the surface because of lack of fluidity, and filling inside was impossible.

On the other hand, when the solution impregnation method described above is used, the pore size is 40 μm.
Since it is as large as m, even if it is dipped and impregnated, the solution flows out from the pores and is hardly filled.

Therefore, in order to fill the mat-like porous body with the active material, it was essential to develop a fluid slurry liquid having an appropriate viscosity.

OBJECT OF THE INVENTION It is an object of the present invention to provide a method for producing a cadmium electrode plate having high performance, low cost and high productivity.

In order to achieve the above-mentioned object, the present invention provides cadmium oxide,
An active material containing metal cadmium as a main component is mixed with an ethylene glycol solution in which carboxymethyl cellulose is dissolved at a temperature of 100 to 120 ° C. to form a fluid slurry, and the slurry viscosity is 1000 to 6000 c.
p. As a method for producing a cadmium electrode plate for an alkaline storage battery, which efficiently fills an alkali-resistant metal mat-like porous substrate.

Example Hereinafter, one example of the present invention will be described in detail.

Carboxymethyl cellulose was added and dissolved in an ethylene glycol solution at a high temperature of 100 to 120 ° C. to obtain a viscosity of 20.
~ 350c. p. Adjust the temperature to 25 ° C. (100
c. p. The front and back are the most suitable. ) In this solution, 75 to 90 wt% of cadmium oxide, 5 to 15 wt% of metal cadmium, and 5 to 10 wt% of nickel powder.
The mixture consisting of is added and mixed with stirring. After stirring, number ~
When left to stand for a few dozen hours and aged, 1000-6000 c.
p. It is possible to obtain a stable slurry for a long time within the range. As is well known, the viscosity of the slurry decreases as the temperature increases, but it is preferably 40 ° C. or lower from the viewpoint of stabilizing the characteristics of the slurry. 1000
c. p. The following low-viscosity slurries cause sedimentation and separation of the active material and are in an unfavorable state. A cadmium electrode plate is obtained by continuously passing a band-shaped nickel fiber mat-shaped porous body having a fiber diameter of about 25 μm and a porosity of 95% into the slurry liquid having fluidity, drying and pressing to a predetermined thickness.

FIG. 1 shows the relationship between the packing density of the active material and the slurry viscosity in a negative electrode plate having a final thickness of 0.6 mm. As is clear from FIG. 1, the active material packing density is greatly influenced by the slurry viscosity.

In particular, the slurry viscosity is 6000 c.s. p. When it is above,
The viscosity became too high, and only the surface of the mat-like porous material was filled, and filling inside was impossible.

On the other hand, 1000c. p. In the following cases, the filled slurry flows out during the subsequent process and cannot be filled.

In addition, as a comparative example, a cadmium electrode plate was produced in the same manner as in the above-mentioned example except that carboxymethyl cellulose was not used. When carboxymethyl cellulose is not used, a stable slurry cannot be obtained for a long time, but 1000 to 6000 c. p. It was possible to manufacture the electrode plate of this comparative example because it had a viscosity of 1.

Next, one cadmium electrode plate of the present invention and two ordinary nickel electrode plates were laminated via a separator, respectively, and a specific gravity of 1.
Using an aqueous solution of 24 potassium hydroxide as the electrolyte,
A battery of the present invention having a capacity of about 1000 mAh was produced. Further, in the same manner, a comparative battery having the same capacity was manufactured using the cadmium electrode plate of the comparative example.

FIG. 2 is a diagram showing the relationship between the cycle number and the active material utilization rate of these batteries. As is clear from FIG. 2, the active material utilization rate of the battery of the present invention does not decrease as the number of cycles increases, that is, the discharge capacity of the battery of the comparative example does not decrease.

EFFECTS OF THE INVENTION Generally, it is known that carboxymethyl cellulose is insoluble in ethylene glycol.
The present invention has been completed by finding that it can be dissolved at a high temperature of 0 to 120 ° C. In addition, carboxymethyl cellulose has long been known to prevent capacity deterioration of the negative electrode, but due to its solubility in ethylene glycol, how efficiently carboxymethyl cellulose is dispersed in a slurry liquid using ethylene glycol as a solvent. It was a difficult problem to solve for a long time.

INDUSTRIAL APPLICABILITY As described above, the present invention can produce a high-performance, low-cost and highly productive cadmium electrode plate which can prevent deterioration of the negative electrode capacity at the same time as adjusting the viscosity of the slurry liquid, and therefore its industrial value is extremely large.

[Brief description of drawings]

FIG. 1 is a diagram showing the relationship between slurry viscosity and active material packing density, and FIG. 2 is a diagram showing the relationship between cycle number and active material utilization rate.

Claims (1)

[Claims] 1. An active material containing cadmium oxide or cadmium metal as a main component, and carboxymethyl cellulose as 100%.
Mixed with an ethylene glycol solution dissolved at a temperature of 120 ° C. to 120 ° C. to form a fluid slurry having a viscosity of 1000 to 6000 c. p. A method for producing a cadmium electrode plate for an alkaline storage battery, which comprises filling an alkali-resistant metal porous substrate as the above.