JPS58121557A - Manufacture of nickel electrode for battery - Google Patents

Abstract

PURPOSE:To remain advantage facilitating filling of an active mass and provide discharge performance and a life similar to a sintered type by improving a pocket type electrode, an electrode using a sponge-like metal porous body as an active mass supporting body, or paste type electrode. CONSTITUTION:Cobalt and part of nickel hydroxide are made in a form of paste and the mixture is allowed to stand. This paste is added to nickel and remaining nickel hydroxide to make paste for an electrode. The preferable standing time of the paste is several hours at 30 deg.C and one hour at 20 deg.C. When the paste is stirred continuously, the standing time is shortened to several hours at room temperature.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a non-sintered nickel electrode in which nickel hydroxide is directly exposed to light as a nickel electrode for use in alkaline batteries;
That is, the present invention relates to a method of manufacturing a paste type two-foamed metal type electrode, a pocket type electrode, and the like.

In batteries used as various power supplies, in systems that use alkaline aqueous solutions as electrolytes, positive electrodes include nickel electrodes, silver oxide electrodes, manganese dioxide electrodes, air electrodes, etc., and negative electrodes include cadmium electrodes, iron rods, hydrogen electrodes, etc. There are poles etc. Among positive electrodes, nickel electrodes are the most popular because they are particularly stable in alkaline aqueous solutions, have excellent charge/discharge reversibility, can be expected to have a long life, and are also excellent in terms of utilization. It is used. In particular, nickel-cadmium batteries have been put into practical use as secondary batteries next to lead batteries, and demand is expected to continue to grow significantly in the future. Further, nickel-zinc batteries and nickel-iron batteries are being developed particularly for use in electric vehicles, and nickel-hydrogen batteries have entered the practical stage for special uses, mainly for space use.

As described above, nickel electrodes are widely used, and their electrode structure used to be the pocket type, but recently the sintered type has been the mainstream. As is well known, the pocket type is obtained by mechanically filling a steel container with many holes with nickel hydroxide and a conductive material such as graphite.

Therefore, although the electrode has a robust appearance, the active material exists only in contact with the conductive material and the container (pocket), so polarization during large current discharge is large and the utilization rate is low. Become. However, there were problems such as short lifespan under harsh conditions such as rapid charging.

On the other hand, in the sintered type, the active material is firmly attached and embedded in the sintered body with micropores, so there are fewer problems like the pocket type described above, and it is difficult to handle large currents. Significant improvements have been made in terms of discharge characteristics, rapid charging characteristics, and lifespan.

Therefore, it can be said that the sintered type has reached the ideal stage from the viewpoint of characteristics alone. However, the production of sintered bodies,
The process for filling active materials is complicated.
The problem is that it is considerably more expensive than the pocket type. Instead of the sintering method, a sponge-like porous metal body with large pore size and porosity is used as an active material support, and the active material is made into a paste form to facilitate the active material.

An even simpler method is the so-called paste method, in which a two-dimensional porous material such as a net, perforated plate, or expanded metal is used as the core material, and an active material and a binder are mixed with this material to form a paste. The coated material is applied, smoothed by passing it through slits or between rollers, and after drying, pressure is applied as necessary. This method is ideal as a manufacturing method because the core material is extremely inexpensive and filling with waste active material is easy, and many proposals have been made.

Paste-type electrodes have a long history, and although the manufacturing method is slightly different, paste-type lead electrode plates are extremely widely used. Well, cadmium poles have also been put into practical use.

The following are the reasons why nickel electrodes have not been put into practical use despite many proposals.

(1) Neither nickel oxyhydroxide as an active material during charging nor nickel hydroxide during discharging is an excellent conductor. Therefore, it is necessary to separately add a conductive material, and even if it is added, it is difficult to improve the utilization rate. Don't worry, if you add too much, the absolute capacity will decrease.

(2) Although the volume of the active material naturally changes due to repeated charging and discharging, severe swelling occurs in the nickel electrode.

The above factors are mainly responsible for the widespread practical application of paste type nickel electrodes. Conventionally, various binders have been considered as a method for preventing the active material from falling off due to swelling and twisting as described in (2) by first increasing the strength.

Examples of the binder include polyethylene, polypropylene, polyvinyl chloride, polystyrene, fluorocarbon resin, polyvinyl alcohol, carboxymethyl cellulose, and ethyl cellulose. Of course, the former is superior in terms of electrolyte resistance and oxidation resistance, but if a large amount is added to improve strength, the voltage characteristics will be inferior and the utilization rate will decrease.
cormorant. In order to suppress this, nickel powder, graphite, etc. were added, but if too much was added, the proportion occupied by the active material would decrease, and if a little was added, the utilization rate would be low.

Addition of the above-mentioned binder and other electrolyte-resistant fibers can improve the characteristics and lifespan of paste type or pressurized nickel electrodes, so-called non-Sakai bonded two-Sokel electrodes, to some extent. Since it is far inferior to the conventional sintering method, it has not been widely used in practice.

The present invention improves the pocket-type electrode, the electrode using a sponge-like porous metal material as an active material support, and the above-mentioned paste-type electrode, and maintains the advantage of being easily filled with active material while improving discharge characteristics and service life. This provides an excellent manufacturing method that approaches the sintering method.

The present inventors first mixed nickel and cobalt into a paste positive electrode material mainly composed of nickel hydroxide, and by gradually drying this from a paste state and leaving it to stand, the utilization rate of the active material was increased. The present invention relates to an improvement of the present invention. In other words, it was found that adding nickel and cobalt to nickel hydroxide and leaving it wet with water was effective in improving the utilization rate of nickel hydroxide; In cases where several hours or more are required and the procedure is not carried out continuously7.

It has been found that several days or more is preferable in some cases. This has the drawback of requiring a large amount of equipment, space, and manpower since it is necessary to process a large amount of paste industrially.

Therefore, the present invention improves this by leaving only part of the cobalt and nickel hydroxide in the form of a paste, and then using this to form a paste with nickel and the remaining nickel hydroxide, etc., for use in electrodes. As a result, in terms of quantity, the amount required is less than that of shoes if the entire product is left alone.

The present invention will be explained in detail below.

A AA size sealed nickel-cadmium storage battery was used as a battery for performance comparison. The cadmium negative electrode manufactured as follows was used. First, a paste mainly composed of cadmium oxide is applied to both sides of a nickel-plated iron punching metal, passed through a slit set to a predetermined thickness, and through a drying process.
．． A 7JIM electrode plate was obtained. Thereafter, it was partially charged in a 10% by weight aqueous solution of caustic potassium to change some of the cadmium oxide into metal cadmium, and after washing with water and drying, it was pressurized to a thickness of 0.56 M.

A polyamide nonwoven fabric was used as the separator, and a small amount of lithium hydroxide dissolved in a 25% by weight aqueous solution of caustic potash was used as the electrolytic solution at 6.3 CC per cell.

In this embodiment, a paste type nickel electrode is used. First, as paste materials, nickel hydroxide with a particle size of 1 to 9 that can pass through a 20o menshie sieve, 100g of carbonyl nickel powder, black m1oy, diameter 0.1wtb, length 3
~5 intestinal acrylonitrile-hinyl chloride copolymer 2 og
, 50 g of carbonyl metal cobalt powder, and a 3% by weight aqueous solution of carboxymethyl cellulose.

In the present invention, in advance, 5 og of nickel hydroxide powder and 50 g of cobalt powder used for this paste are mixed with 10 OCC of water.
was added and left at 30°C. It was dried for two days while suppressing water evaporation. The mixture was gently stirred once every 2 hours.

The color changed from pale black to pale blackish brown. This was lightly crushed and used for the above paste.

The core material used was a punched metal plate with holes of 2 diameters and a pitch of 3M between centers on a 0.1M thick iron plate, which was then nickel plated. The above paste is applied to both sides of this core material, passed through a slit, and the thickness after drying is 1. ○±
It was set to 0.051M. Then 200g of cobalt acetate/
After drying, cobalt hydroxide was added by immersing it in an aqueous solution of L and then dipping it in an aqueous solution of caustic potassium to change cobalt acetate into cobalt hydroxide.

The electrode plate thus obtained was first cut into pieces of 120mm wide and 680mm long.

Then, pressure was applied between rollers, and an aqueous dispersion of polytetrafluoroethylene (resin content: 15% by weight) was added, followed by drying. The thickness of the electrode was 0.7 mm. This electrode was further cut into 2 AA size pieces. In this case the width is 38
I made the length 220B with J5.

This was combined with the cadmium electrode and separator to form a daytime battery. This battery is referred to as (A). 10,・
- A battery with a nickel electrode that was used after leaving the entire paste in the same manner as in (A) was designated as CB), and one battery with a nickel electrode moss that was used without being left in this manner was designated as (CB).
Let it be q.

As mentioned above, if a mixture of nickel hydroxide and cobalt is left undisturbed, the entire surface becomes a faint blackish brown color.

The reason for this is not clear, but it is thought that cobalt is mixed and diffused into nickel hydroxide while changing into an oxide. This reaction seems to be accelerated by exposure to oxygen while wet with water, and no significant effect can be expected if it is left in a complete solution or if a mixture of the two is rapidly dried. was recognized.

The charging capacity of these batteries (A) ~ (q and the utilization rate at each discharge, and the case where the capacity decreases to 60% of the initial capacity when charged and discharged under the conditions of 0.15 C for charging and 0.40 C for discharge) The cycle life is shown in the table below.

As is clear from this table, the effects of (A) and (B) that were left to stand were greater than those that were used immediately. It has been found that the present invention has almost the same effect even if the entire paste is not left to stand, and the clutter that accompanies leaving the paste to stand can be significantly reduced.

In addition, in the example, the case of leaving at 30°C is shown, but if the temperature is higher than this, it is necessary to slow down the drying speed, and the drying time may be several hours. The optimum time is about one week.

In addition, when constant stirring is performed, the time for standing can be shortened, and may be about several hours even at room temperature. Additionally, adding cobalt metal to a portion of nickel hydroxide and leaving it as is effective, while adding cobalt oxide from the beginning is preferable in terms of expecting such an effect. do not have.

In the embodiment, a paste type was described, but the same applies when using a sponge-like metal porous body, and in the case of a pocket type, a dry one may be used.

Further, if a part of cobalt and nickel hydroxide is left in the form of a paste and then dried, it can be easily crushed and used in a paste form or a pocket form. That point,
When nickel and cobalt or cobalt alone is wetted with water and left to dry, the powder will coagulate and form a solid lump.
It is difficult to pulverize this, and the present invention does not have this disadvantage.

As described above, according to the present invention, both the utilization rate and the lifespan of a non-sintered nickel electrode can be improved.

Claims (1)

[Claims] A method for producing a nickel electrode comprising the step of turning a mixture containing nickel hydroxide as a main component and nickel powder and cobalt powder into a paste, the method comprising: adding water to a part of the mixture of cobalt and nickel hydroxide, and leaving it to stand. A method for manufacturing a nickel electrode for a battery, which includes the step of drying the nickel electrode.