JPS6191873A - Manufacturing method of cadmium negative electrode plate for alkaline storage battery - Google Patents

Abstract

PURPOSE:To improve the workability at manufacturing, the energy density of a plate, and the coefficient of active material utilization by adding a specific acid and its salt to paste applied to a collection body that forms a negative electrode plate. CONSTITUTION:When at least either citric acid or its salt is added to the paste in which the active material powder containing cadmium oxide is kneaded with a binding agent and the solvent mainly made of water, cadmium oxide reacts to water and is prevented from changing into cadmium hydroxide. As a result, if a negative electrode is created by applying this paste to a collection body and drying it, the workability at manufacturing, the energy density of a plate, and the coefficient of active material utilization can be improved in the same way as where an organic acid is used as the solvent.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for manufacturing a paste-type cadmium negative electrode plate for alkaline storage batteries.

Conventional technology and its problems When manufacturing a paste-type cadmium negative electrode plate, metal cadmium, cadmium hydroxide, and cadmium oxide are considered as the raw material active material powder, but metal cadmium:
] Since it has a high concentration of 1- and large n particles and low activity, it cannot be used as a main raw material for active materials. Furthermore, cadmium hydroxide has a disadvantage that it has a lower C density than cadmium oxide, resulting in a lower energy density per electrode plate volume.

For these reasons, it is desirable to use cadmium oxide as the raw material for the active material in terms of gas and energy density.

Organic solvents and water can be considered as solvents, but if water, which is inexpensive, is used, cadmium oxide will react with water and change to cadmium hydroxide, which will not only lower the energy density per electrode plate volume, but also reduce the energy density per plate volume. Conventionally, organic solvents have been used as solvents because the paste hardens within a short period of time, significantly reducing workability. Since the organic solvent does not react with cadmium oxide, it is possible to obtain a paste-type cadmium negative electrode plate with high energy density per electrode plate volume and active material utilization rate, and it is also a raw material that has advantages such as good workability. Not only is the cost higher than that of water, but the conditions for removing it are limited, making the culm complicated to manufacture and increasing the manufacturing cost. There is also a risk of fire.

For these reasons, there has been a desire for a paste-type cadmium zero electrode TA, etc., to have a high energy density per electrode plate volume, a high active material usage rate, and an inexpensive manufacturing method that requires only one stroke.

The present invention is as follows-1-1 among the 41 prior art techniques! The purpose is to solve n points. 1. Means for Solving the Problems The present invention is a 2Wi method for producing paste-type cadmium negative electrode plates for alkaline storage batteries, in which an active vA powder containing cadmium oxide is combined with a solvent containing a binder and water. When kneading it into a paste to form a paste, citric acid and one of its salts are added as part of the eleventh rule.

Effect When kneading the active material powder containing cadmium oxide with a binding agent and a solvent mainly composed of water to form a base 1-, adding 1 + 5 drops of ricinic acid and its salts produces cadmium oxide. Suppresses the reaction of water with water and its transformation into cadmium hydroxide. Despite using water as a solvent, which is a low-cost raw material and manufacturing cost, compared to the conventional water-based manufacturing method that does not add cunic acid or its salts. , Zono 11 work 1 Jiv) Pole plate 1 1
The channel 1'-density 1σ and the active material utilization rate are improved, and the same effects as those obtained by using a stone printing solvent as the solvent can be obtained.

The reason why citric acid and 12;+ have the above effects (,
1 Although it is not clear, the cadmium oxide book “I
+" is stabilized [V, F').

Example i, 1 chemical 711 i'Mi'', / mu (1irl product ¥ 1 powder t) 100 parts, ')!f Leucel I]
-2 parts of binder II! Knead 19 parts of io, 6 parts of water (dissolved 1% l) + 1 part (1 part) to form a paste.
7. This paste 1- was applied to a perforated metal plate made of nickel and iron in 19 predetermined areas. Created and tried it on, 1: L, 1.

2. Tolic acid instead of monophosphoric acid in Example 1 above
A negative electrode plate was prepared using potassium using the method 1) similar to that in Example 1, and this was subjected to a test of 1'il+3.

For comparison, a polar plate was prepared in the same manner as in Example 1 except for the addition of phosphoric acid, and this was designated as Sample C ().

The trial obtained as above is 1Δ, [3, C is 40x 4
After cutting to 0man dimensions, S, G, 1
．． Two sintered nickel positive electrodes of the same size as the sample were used as counter electrodes in 250 (20°C) K O+-1, and when charged and discharged with a current of 0.2 CA for the theoretical capacity ■ of test r1. Figure 1 shows the active material utilization rate during discharge, and Figure 2 shows the active material utilization rate during discharge.

As is clear from these figures, Sample 1'lA, in which citric acid or its salt was added to suppress the conversion of cadmium oxide to no)domium hydroxide, was more extreme than Sample C, in which citric acid or its salt was added. In addition, the pot life until the active material paste hardens was about 70 in the case of Examples 1 and 2 in which phosphoric acid or salt was added.
-24 hours, compared to about 20 minutes without addition. From these facts, the effect of adding citric acid and its salts is clear, and its industrial value is great.

Effects of the Invention As described above, in the present invention, when the active material powder containing cadmium oxide is kneaded with an adhesive and a solvent mainly composed of water to form a paste, at least one of citric acid and its salts is added. By adding J and C, it is possible to suppress the reaction of cadmium oxide with water and change to cadmium hydroxide, thereby preventing a decrease in C workability, making it possible to create pastes and formulas that are energy dense and have a high active material utilization rate. Cadmium negative electrode plates can be obtained.

[Brief explanation of the drawing]

Figure 1 is a diagram comparing the active material utilization rate during discharge during charging hR cycle and P+', and Figure 2 is a diagram comparing the amount of discharged electricity.
This figure shows 67).

Claims (1)

[Claims] 1. An active material powder containing cadmium oxide is kneaded with a binder and a solvent mainly composed of water to form a paste, and the paste is applied to a current collector and dried, in which citric acid and its like are added to the paste. A method for producing a cadmium negative electrode plate for an alkaline storage battery, characterized by adding at least one salt.