JPS6224562A - Cadmium electrode plate for sealed battery - Google Patents

Abstract

PURPOSE:To reduce cost and increase productivity by filling a negative active material mainly comprising cadmium or cadmium compound in a steel fiber sinter which is not plated. CONSTITUTION:A negative active material mainly comprising cadmium or cadmium compound is filled in a steel fiber sinter which is not plated. For example, paste-like material obtained by mixing active material mainly comprising cadmium oxide with solvent such as ethylene glycol is filled in a sinter having a porosity of 95% obtained by sintering steel fibers having a diameter of 4-50mu in a reducing atmosphere. After removing the solvent at 200 deg.C, they are dried and pressed to a specified thickness to obtain a negative plate.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a cadmium electrode for a sealed nickel-cadmium battery.

Prior Art and Its Problems Conventionally, cadmium electrodes used in sealed nickel-cadmium batteries are classified into two types. One of them is called a sinter set, in which a microporous sintered substrate of ten or more microns is made by sintering fine nickel powder of 2 to 3 microns onto a perforated steel plate, and is impregnated with a cadmium nitrate solution. It is then converted into cadmium hydroxide in an alkaline solution.

The so-called solution impregnation method is used to fill the active material by repeating this operation. This method requires a complicated process and uses a large amount of expensive nickel powder, resulting in an extremely expensive electrode plate.

The other method is to make a paste by adding water and a thickener to a cadmium active material, and directly fill it into a nickel-plated perforated steel plate, nickel fiber sintered body, nickel-plated iron fiber sintered body, etc. This is called a paste type. Compared to a complete sinter set, the manufacturing process is significantly simplified since it starts from the cadmium active material itself. On the other hand, since the iron content in the alkali is not clear, the material used is a nickel plating process, nickel fiber sintered body, etc., so the cost is only slightly lower than the conventional method that does not use nickel powder.

Therefore, in order to significantly reduce costs, it was essential to use cheaper materials.

OBJECTS OF THE INVENTION It is an object of the present invention to provide a cadmium electrode plate with good production efficiency in a low-cost tank.

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention is a cadmium electrode plate in which an unplated iron fiber sintered body is filled with a negative electrode active material containing cadmium or a compound thereof as a main component. That is, a sintered iron fiber paste type negative electrode plate is used in a sealed battery in an oxygen atmosphere in which the iron fibers become passivated (to prevent corrosion of the iron).

Example An embodiment of the present invention will be described in detail below.

An active material mainly composed of cadmium chloride is applied to a sintered body of 95% volume, which is made by sintering iron fibers with a wire diameter of 4 to 50μ in a reducing atmosphere, in the form of a paste using a solvent such as ethylene glycol. No filling. Thereafter, the solvent is removed at a high temperature of 200'C, followed by a drying process and pressing to form a negative electrode plate of a predetermined thickness. This negative plate and the conventional sinter positive plate,
A cylindrical sealed nickel-cadmium battery was created using a nylon non-woven fabric separator, KOH electrolyte, etc. Charge this battery at 0.10 for 15 hours and get 0.20 tej,oO
The battery performance and the degree of corrosion of the negative electrode iron fiber sintered body were investigated by repeating the operation of discharging to V for about 300 cycles A/repetition. The first figure shows an ``AA'' size hermetic seal consisting of a negative electrode plate using sintered nickel fibers and sintered iron fibers! This shows the change in capacity of a nickel-cadmium battery. It was found that the capacity deterioration was actually less in the case of iron fibers. Furthermore, the batteries were disassembled every 100 cycles and the amount of corrosion of the iron fibers was investigated, as shown in Table 1.

Some corrosion is observed in the initial image, but no progress has been made since then. It is generally said that iron corrodes in highly concentrated alkaline solutions, but results contrary to this were obtained. In order to investigate the cause of this, we analyzed the amount of corrosion after leaving iron fibers in an alkaline solution in an oxygen atmosphere and a hydrogen atmosphere.
The amount of corrosion in an oxygen atmosphere is approximately 1/1 of the amount of corrosion in a hydrogen atmosphere.
It was 7. That is, it has been revealed that in an oxygen atmosphere, a passive film (triiron tetroxide film) with electron conductivity is formed on the surface of iron, and corrosion does not proceed. As is well known, the sealing mechanism of a sealed nickel-cadmium battery is an oxygen absorption cycle, and the inside of the battery is always in an oxygen atmosphere. It is thought that for this reason, the corrosion of the iron fibers does not progress. On the other hand, open type Ni-Kel-cadmium cells, which do not undergo sufficient oxygen absorption cycles, require conventional nickel plating.

As mentioned above, the iron fiber sintered body that is not subjected to nickel plating can reduce the price of the material, which has been expensive up to now, and also improves production efficiency since it does not require a nickel plating process.

Effects of the Invention The present invention provides a cadmium electrode with good production efficiency at a low price by using a cadmium electrode plate in which an iron fiber sintered body without plating is filled with a negative electrode active material mainly composed of cadmium or its compound. Since it can provide plates, its industrial value is extremely large.

[Brief explanation of drawings]

FIG. 1 compares the performance of a sealed nickel-cadmium battery using the electrode plate of the present invention and a conventional electrode plate.

Claims (1)

[Claims] A cadmium electrode plate for a sealed battery, characterized in that a negative electrode active material containing cadmium or its compound as a main component is filled into an iron fiber sintered body that is not subjected to plating treatment.