JPH0318305B2 - - 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.

Conventional technology and its problems Conventionally, as a cadmium negative electrode plate for alkaline storage batteries, a sintered type electrode plate in which an active material is filled in a porous substrate made by sintering nickel powder into a perforated steel plate or nickel net has been well known. There is. This porous substrate is simply sintered nickel powder into a perforated steel plate, nickel net, etc.
The bond between nickel powder particles is weak, and the porosity is practically 80.
The limit is about %.

In addition, these porous substrates always require a core metal such as a perforated steel plate or nickel net to hold the nickel powder, which has weak interparticle bonds, and the amount of active material filled per unit volume is equal to the volume of the core metal. It has fewer drawbacks. As is well known, this porous body is a sintered body of finely powdered nickel with a diameter of 2 to 3 microns, and most of the pores are 10 microns or smaller. For this reason, the active material filling method is limited to the solution impregnation method, which includes impregnation, neutralization, water washing,
The drying process must be repeated several times to fill the specified amount. This leads to an increase in the cost of the electrode plate or a decrease in energy density.

In an attempt to eliminate this drawback, for example, a solid active material is directly filled into a nickel-plated iron fiber sintered body without a core metal, or a foamed nickel porous body created by electrolytic nickel plating, etc.
A so-called paste filling method has been used.
However, the former has problems such as instability of the plating, and the latter has problems such as low tensile strength.

A method for producing metal fibers has been proposed that improves these drawbacks. This involves moving a nickel wire several millimeters in diameter over a cutting tool while cutting it into even thinner fibers. However, with this manufacturing method,
The drawback was that the cutting tool was severely worn out, and only fibers with uneven diameters could be produced.

In addition, conventional paste-type cadmium electrodes, in which active materials such as cadmium oxide and cadmium hydroxide, conductive materials such as nickel powder, and organic solvents are coated and dried on a conductive substrate made of a perforated steel plate with nickel plating, are used in an alkaline electrolyte. It had undergone chemical charging and discharging treatment. The negative electrode plate, in which metal cadmium remains partially due to chemical formation, the discharged nickel positive electrode plate, and the separator are rolled together, placed in a battery case, filled with electrolyte, and sealed, producing a sealed nickel-cadmium battery. There is. If there is no residual cadmium and all cadmium hydroxide is used during sealing, the cadmium electrode has a lower utilization rate than the nickel electrode, so the capacity is limited on the cadmium electrode side. Also, while the nickel electrode side has almost no capacity deterioration as the charge/discharge cycle progresses, the cadmium electrode side has the characteristic of gradually deteriorating, so extra cadmium is left to compensate for this. . The initial deterioration of the negative electrode capacity is large, but it stops after approximately 60 to 80%, and the deterioration thereafter becomes extremely small.

In other words, while the utilization rate of the active material is apparently close to 100% for the positive electrode, it is only 60% for the cadmium electrode.
~80%.

In order to maintain a balance between these two capacities, the above-mentioned chemical conversion treatment is performed. This process is not only complicated, but unlike sintered cadmium electrodes in conventional paste-type cadmium electrodes, the active material often falls off due to the gas generated during formation. Therefore, due to uninvented incomplete partial chemical formation of gas,
It was necessary to control the amount of residual cadmium.

OBJECTS OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and an object thereof is to provide a paste-type negative electrode plate for alkaline storage batteries that is high-performance, low-cost, and highly productive.

Structure of the Invention In order to achieve the above-mentioned object, the present invention includes a step of producing nickel fibers by cutting a nickel block by vibration vibration, a step of uniformly distributing the nickel fibers by an air-laid method, and then a step of distributing the nickel fibers into a nickel fiber distribution body. A process of sintering in a reducing atmosphere to obtain a nickel fiber sintered body. Next, a process of adding and mixing ethylene glycol and carboxymethyl cellulose to cadmium oxide and metal cadmium to prepare a slurry active material. Next, a process of sintering the nickel fiber. A step of filling the aggregate with a slurry-like active material, a step of partially drying the active material-filled electrode plate, a step of adjusting the thickness of the partially dried electrode plate, and then a process of adjusting the thickness of the electrode A method for producing a paste-type negative electrode plate for an alkaline storage battery, comprising the step of removing ethylene glycol by drying the plate.

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

Nickel fibers with a fiber diameter of 4 to 50 μm are produced by vibration-cutting a nickel block.

The nickel fibers are continuously and uniformly distributed by an air-laid method to form a nickel fiber distribution body.

This nickel fiber distribution body is heated in a reducing atmosphere to approx.
Sinter at 1000℃. As a result, a nickel fiber sintered body was obtained. Figures 1a and 1b (b is an enlarged view of a) show microscopic photographs of the nickel fiber combustion body. The nickel fiber produced by chatter vibration cutting has convex portions called chatter marks on the fiber surface, as shown in FIG. 1b. (Wrinkle-like white area on the fiber surface in FIG. 1b) This allows the fiber to be distinguished from fibers produced by other methods.

The porosity of the fiber sintered body can be adjusted from 85 to 85 by controlling the amount of fiber, sintering temperature, time, etc.
About 98% can be obtained.

Next, cadmium oxide 60-80wt%, particle size 0.5
~ Metallic cadmium 40 consisting of fine particles of 1 μm ~
20wt% and mix well. A slurry active material is prepared by adding 5 to 9 wt% ethylene glycol and 0.6 wt% carboxymethyl cellulose.

A continuous body of several tens of meters of the above-mentioned nickel fiber sintered body is continuously passed through this slurry-like active material, and is filled with the active material by infiltrating the active material.

Thereafter, the electrode plate surface area is partially dried in a dryer equipped with an infrared lamp adjusted to a temperature of 60 to 80°C. Then, it is made to a predetermined thickness using a roller press. After adjusting the thickness, the electrode plates are passed through a hot air dryer at a temperature of 250°C to completely remove ethylene glycol. Finally, the plates are cut to size appropriate for the desired battery size. This negative electrode plate, a sintered positive electrode plate that has been completely left to undergo conventional chemical conversion treatment, and a separator made of polypropylene nonwoven fabric are automatically rolled up and then inserted into a battery case. After that, a potassium hydroxide aqueous solution is poured into the container and the container is sealed. A sealed battery is left for a day and night to develop compatibility with the electrolyte, and then charged and discharged to become a completed battery.

We investigated the lifespan at room temperature of the C-sized sealed nickel-cadmium battery completed in this way and the same-sized sealed nickel-cadmium battery made of a sintered negative electrode plate created by a conventional chemical conversion process. As shown in FIG. 2, it was found that the battery according to the present invention was superior in both capacity and life.

The reason for the improved battery capacity is that while the energy density of conventional sintered negative electrode plates is approximately 550mAh/cc due to the core metal, low porosity, etc., the fiber type negative electrode plate of the present invention has an energy density of 704mAh/cc. Since the capacity density has been significantly improved to /cc, the extra volume can be diverted to the positive electrode side, resulting in a battery with a higher capacity overall. Furthermore, conventional batteries using microporous sintered bodies have a shorter lifespan. The reason for this is that batteries at the end of their lifespan are limited in negative electrode capacity, and conventional sintered batteries have fine pores.
It was found that this was because the pores were blocked due to the agglomeration of cadmium in the electrode plate, worsening internal diffusion of the electrolyte. It was found that the fiber sintered body of the present invention does not have a core metal and has large pores, so that the electrolyte can flow very well, and the negative electrode does not deteriorate much.

The paste-type negative electrode plate for alkaline storage batteries of the present invention does not require a chemical conversion treatment process, has excellent productivity, and is a paste-type negative electrode plate that can be easily filled with active material and can be produced at low cost.

Effects of the Invention As described above, the present invention can provide a paste-type negative electrode plate for alkaline storage batteries that is high-performance, low-cost, and highly productive, and therefore has extremely great industrial value.

[Brief explanation of the drawing]

FIGS. 1a and 1b are micrographs of a nickel fiber sintered body subjected to chatter vibration cutting according to the present invention. FIG. 2 is a life comparison characteristic curve diagram 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 producing nickel fibers by vibration-cutting a nickel block, then a step of uniformly distributing the nickel fibers by an air-laid method, and then sintering the nickel fiber distribution body in a reducing atmosphere. Next, a step of adding and mixing ethylene glycol and carboxymethyl cellulose to cadmium oxide and metal cadmium to prepare a slurry-like active material; Next, adding a slurry-like active material to the nickel fiber sintered body. The step of filling the active material-filled electrode plate with a substance, the step of partially drying the electrode plate filled with the active material, the step of adjusting the thickness of the partially dried electrode plate, and the step of drying the thickness-adjusted electrode plate with ethylene glycol. A method for producing a paste-type negative electrode plate for an alkaline storage battery, comprising the step of removing.