JPH0318304B2 - - Google Patents

Description

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

Prior Art and its Problems Conventionally, paste-type negative electrode plates have been widely used as negative electrode plates for alkaline storage batteries because they are easy to manufacture. A sintered body of alkali-resistant nickel fiber is used as the core metal of this negative electrode plate.
This nickel fiber was made by adding a small amount of different metals to nickel and cutting it into a fiber body. However, the knife was severely worn out during cutting, making it difficult to always produce fibers with a uniform diameter. As a result, the active material of the negative electrode plate using this fibrous material as a core material often falls off, and when assembled into a battery, variations in the capacity of the negative electrode plate and internal short circuits of the battery occur.

In addition, conventional paste-type negative electrode plates have been produced by applying active materials such as cadmium oxide and cadmium hydroxide, conductive materials such as nickel powder, and organic solvents to a conductive substrate and drying them. This negative electrode plate was subjected to a charging/discharging process called chemical formation in an alkaline electrolyte. As a result of this chemical conversion, some of the cadmium remained and was taken out, washed with water, and dried. This cadmium negative electrode, a separately prepared nickel electrode in the final state of discharge, a separator, etc. were inserted into a battery case, and after pouring an electrolyte solution, the container was sealed to produce a sealed nickel-cadmium battery. The reason why some cadmium remains on the negative electrode plate is to limit the battery capacity on the nickel electrode side when the battery is discharged.

If there is no residual cadmium and all cadmium hydroxide is used during sealing, the cadmium electrode will have a lower utilization rate than the nickel electrode, so the capacity will be limited on the cadmium electrode side. In addition, the nickel electrode side has the characteristic of almost no capacity deterioration as the charge/discharge cycle progresses, whereas the cadmium electrode side has the characteristic of gradually degrading. This allows cadmium to remain. The deterioration of this cadmium electrode stops at about 60 to 80% of the theoretical electrochemical capacity of the active material, and thereafter the 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.
Chemical conversion treatment is necessary to maintain a balance between these two capacities.

However, this process is complicated and has low productivity.
In paste-type cadmium electrode plates, active materials often fall off due to gases generated during formation.

In order to improve this, a manufacturing method must be adopted in which charging is performed for a long time in a low-concentration alkaline electrolyte with low viscosity and at a low current density, and the generated gas is quickly released to the outside of the electrode plate.

This also has the disadvantage of poor productivity.

Purpose of the Invention The present invention has been made in view of the above-mentioned problems of the conventional art, and it provides a method that does not cause shedding of active materials and does not require a chemical conversion process.
The object of the present invention is to provide a paste-type negative electrode plate for alkaline storage batteries with excellent productivity.

Structure of the Invention In order to achieve the above object, the present invention includes a step of adding an organic binder and water to nickel powder or nickel oxide powder to prepare a paste, and then extruding the paste through a micro-hole nozzle to form a fiber. Next, the formed fibrous material is heated to remove the organic binder and water. Next, the fibrous material from which the organic binder and water have been removed is sintered in a reducing atmosphere to form a nickel fiber sintered body. Next, a step of preparing a slurry negative electrode active material from cadmium oxide and metal cadmium with ethylene glycol. Next, a step of filling the nickel fiber sintered body with the slurry negative electrode active material. Next, a step of partially filling the filled electrode plate. A paste type for alkaline storage batteries characterized by comprising the following steps: drying the partially dried electrode plate, adjusting the thickness of the partially dried electrode plate, and then removing ethylene glycol by drying the thickness-adjusted electrode plate. This is a method of manufacturing a negative electrode plate.

Example Hereinafter, details of the present invention will be explained based on one example.

A paste is prepared by adding and mixing an organic binder and water to nickel powder or nickel oxide powder.

This paste is then extruded through a micro-hole nozzle to form fibers. This is heated to approximately 500°C to remove organic binder, water, etc. It is then sintered in a high-temperature reducing atmosphere of about 1000°C. By this,
A nickel fiber sintered body is obtained. This fiber diameter is
The fiber diameter is 4 μm to 50 μm, and the micrographs shown in FIG. 1 a and b show that the fiber diameter is uniform.

Next, 60 to 80% cadmium oxide, with a particle size of several μm.
20 to 40% of metallic cadmium, which has a diameter of ~10-odd μm, is mixed well. A slurry negative electrode active material is prepared by adding 5 to 9% ethylene glycol to this mixture.

Next, the nickel fiber sintered body is passed through the slurry-like negative electrode active material to fill it.

The filled electrode plate is partially dried in a dryer equipped with an infrared lamp at a plate surface temperature of 60 to 80°C.

Next, it is adjusted to a predetermined thickness using a roller press.

Next, ethylene glycol is completely removed using a hot air dryer at a temperature of 250°C. With this, the negative electrode plate is completed.

The negative electrode plate is cut into predetermined dimensions.

On the other hand, the positive electrode plate uses a known sinter type positive electrode plate, and is brought into a fully discharged state by chemical conversion treatment.

Using a separator made of a negative electrode plate, a positive electrode plate, and a polypropylene nonwoven fabric, roll them up and insert them into a battery case.

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 make it compatible with the electrolyte, and then charged and discharged to form a completed battery.

A C-sized sealed nickel-cadmium battery according to the present invention and a sealed nickel-cadmium battery of the same size were created using a negative electrode made by a chemical conversion process using a conventional pasted negative electrode plate using cut nickel fibers. The cycle life characteristics of the batteries and batteries were investigated at room temperature. The results are shown in FIG. Batteries are superior in capacity and lifespan. This is because the active material on the negative electrode plate does not fall off and the capacity is stable.

Further, the negative electrode plate of the present invention does not require a chemical conversion process and is excellent in productivity.

Effects of the Invention As described above, the present invention can provide a paste-type negative electrode plate for alkaline storage batteries that does not cause shedding of active materials, does not require a chemical conversion process, and has excellent productivity, so its industrial value is extremely large. be.

[Brief explanation of drawings]

Figures a and b in Figure 1 are microscopic photographs of the nickel fiber sintered body used in the present invention, and Figure 2 is a characteristic curve diagram comparing the lifespan of the battery of the present invention and a conventional battery. ...battery of the present invention, ...conventional battery.

Claims (1)

[Claims] 1. A step of adding and mixing an organic binder and water to nickel powder or nickel oxide powder to prepare a paste.Next, a step of extruding the paste through a micro-hole nozzle to form it into a fibrous form. Next, the fibrous material from which the organic binder and water have been removed is sintered in a reducing atmosphere to form a nickel fiber sintered body. and metal cadmium with ethylene glycol to prepare a slurry negative electrode active material, then filling the nickel fiber sintered body with the slurry negative electrode active material, then partially drying the filled electrode plate, and then A method for producing a paste-type negative electrode plate for an alkaline storage battery, comprising the steps of: adjusting the thickness of a partially dried electrode plate; and then removing ethylene glycol from the thickness-adjusted electrode plate by drying it.