JPS6023961A - Manufacture of paste type negative electrode plate for alkaline storage battery - Google Patents

Abstract

PURPOSE:To fully remove an organic solvent that deteriorates the charge efficiency of a positive electrode by filling a nickel fiber sintering body with active material in which cadmium oxide and metallic cadmium are formed into a slurry shape by an ethylene glycol solvent and drying it above the melting point temperature of the solvent. CONSTITUTION:While 60-80% cadmium oxide and 20-40% metallic cadmium are being well mixed, they are formed into a slurry shape by adding 5-9% ethylne glycol to them. Then a high porosity sintering body made of nickel fiber with fiber diameter 4-5mu is filled with active material by continuously passing though and penetrating into this slurry solution. Subsequently, a plate it is partially dried in a drying machine consisting of an infrared lamp that is adjusted so that the vicinity of the plate surface can approach to 60-80 deg.C and is set in a specified thickness by a roller press. After the thickness of the plate is adjusted, the plate passed through a hot air drying machine with 250 deg.C and fully removes ethylene glycol. Finally, the plate is cut in dimensions conforming to the desired battery size. A sealed type nicke cadmium battery with high capacity and life can be obtained by using this negative electrode plate.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a cadmium electrode for a sealed nickel-cadmium secondary battery.

After filling a 2.7 Kel fiber sintered body with a wire diameter of 4μ to 50μ with an active material made of a slurry of cadmium oxide and metal cadmium in an ethylene glycol solvent, it is dried at a temperature of 200°C or higher, which is the boiling point temperature of the solvent, Characterized by complete removal of solvent.

Up until now, the most inexpensive method of manufacturing alkali-resistant nickel fibers has been to cut 2.7 Kel with a small amount of different metals added. However, the knives used during cutting are subject to significant wear and tear, making it difficult to always produce fibers with a uniform diameter. The nickel fiber sintered body used in the present invention is made of nickel powder or nickel oxide powder and an organic binder.

Add water, etc. to make a paste, then extrude it through a micro-hole nozzle to make it into a fiber, and heat it to about 50'C.
The organic binder, water, etc. are removed by heating to . After that, it is sufficiently sintered in a high-temperature reducing atmosphere at about 1000°C, as shown in Figures 1a and 1b (b is an enlarged view of a).

).

Conventionally, active materials such as cadmium oxide and cadmium hydroxide,
Paste-type cadmium electrodes are made by applying conductive materials such as nickel powder and organic solvents to conductive substrates and drying them.
A charging/discharging process called chemical conversion was performed in a 14-potassium electrolyte. After chemical conversion, some of the cadmium was removed, washed with water, and dried. This cadmium electrode, the nickel electrode at the end of discharge, a separator, etc. are rolled up into a battery case, and after pouring an electrolyte solution, the container is sealed to produce a sealed nickel-cadmium battery. As is well known, the purpose of leaving some cadmium behind is to limit the battery capacity on the nickel electrode side during discharge.

If there is no residual cadmium and all cadmium hydroxide is used during sealing, compared to a nickel electrode.

Since the cadmium electrode has a lower utilization rate, the capacity is limited on the cadmium electrode side. In addition, the nickel electrode side has the characteristic that there is almost no capacity deterioration as the charge/discharge cycle progresses.

Since the cadmium electrode side has the characteristic of gradually deteriorating,
Cadmium is left to compensate for this.

The deterioration of this cadmium pole.

It stops at about 60 to 80% of the theoretical electrochemical capacity of the active material, and thereafter deterioration becomes extremely slow. In other words, the utilization rate of the active material is nearly 100% on the nickel electrode side, while it is around 60 to 80% on the cadmium electrode side.
In order to maintain a balance between these two capacities, the chemical conversion treatment described above is repeated. This process is not only complicated.

Unlike sintered cadmium electrodes, paste-type cadmium electrodes often suffer from active material falling off due to gases generated during formation. Therefore, it is necessary to use a solution such as charging with a low concentration alkaline electrolyte with low viscosity and a low current density for a long time so that the generated gas can quickly escape from the electrode plate. Although it is possible to create a paste-type negative electrode plate using a conventional method using a nickel fiber sintered body, the method of the present invention involves filling a nickel fiber sintered body with a slurry consisting of an active material and an organic solvent, and then applying an active material to the nickel fiber sintered body. A sealed nickel-cadmium battery is obtained by completely removing the organic solvent, which is an impurity other than the substance, and rolling it in with nickel electrodes, separators, etc. without undergoing chemical conversion treatment, and sealing the battery after pouring an electrolyte. Since no alkali is used in the process of injecting the electrolyte, there is very little chance of contamination with carbonate radicals, which are harmful to the battery. Furthermore, organic solvents have the disadvantage of deteriorating the charging efficiency of the positive electrode, but can be completely removed by drying at a temperature above the boiling point.The present invention has many advantages in these various points. It is something.

Furthermore, since this nickel fiber sintered body is made by sintering fibers, it has a high porosity of 90%.

It also has excellent strength.

As is well known, today metal cadmium can be produced into fine particles of several microns to several microns and is commercially available at low cost. Also, cadmium oxide.

When in contact with water or alkaline electrolyte, CaO+H2
O−>C(1(OH) 2 ) and changes to cadmium hydroxide, while the change of metal cadmium to Ca (OH) 2 is small.

An explanation will be given below based on one embodiment of the present invention.

Cadmium oxide 60-8D%, metal cadmium 20-4
Add 5 to 9% ethylene glycol to this mixture while mixing well to form a slurry. After that, several pieces of the highly porous sintered body were continuously passed through the slurry liquid.

The active material is filled by osmosis.

Thereafter, it is partially dried in a dryer equipped with an infrared lamp adjusted so that the temperature near the surface of the electrode plate is 60 to 80°C, and then it is made to a predetermined thickness using a roller press. The electrode plate after thickness adjustment.

Ethylene glycol is completely removed by passing through a hot air dryer at a temperature of 250'C. Finally, the plates are cut to size commensurate with the desired battery size.

This negative electrode plate, a sintered positive electrode plate completely discharged by conventional chemical conversion treatment, a separator made of polypropylene nonwoven fabric, etc. are used to automatically write information, and then the information is inserted into the battery case. Thereafter, one or more alkaline aqueous solutions selected from potassium hydroxide, sodium hydroxide, and lithium hydroxide are injected and sealed. After sealing, the battery is left for a day and night to become compatible with the electrolyte, and then charged and discharged to become a completed battery.

The C-sized sealed nickel-cadmium battery (1) completed in this way and the negative electrode plate made using the conventional chemical conversion treatment process are used to produce a compact 12J battery of the same J size.
When the lifespan of the 5-nickel power domiuno battery (1) (h1□) was reduced to one week (-ro), as shown in Figure 2, the uninvented battery was superior in both capacity and lifespan 6θ. It turned out.

As described above, the manufacturing process of the present invention is much simpler than the conventional method, and the manufacturing process of the present invention is much simpler than that of the conventional method.
Since the metal is completely removed, it has excellent characteristics in terms of capacity and lifespan, and its industrial value (+f is extremely large).

[Brief explanation of drawings]

1 II''A, a and b are microscopic photographs of the Nokel fiber & ft sintered body used in the present invention (・5-). (1) Battery of the present invention (11) Conventional Ei, Ike Applicant Asa Battery Co., Ltd. Figure 1 α Figure 1 Figure 2 Figure 100 200 300 Number of charging/discharging γa cycles ( fart)

Claims (1)

[Claims] 4 made from nickel powder or nickel oxide powder
A method for producing a base 1 negative electrode plate for an alkaline storage battery, in which a sintered body made by sintering nickel fibers of μ to 50 μ is filled with a mixed active material of cadmium oxide and metal cadmium.