JPH0693360B2 - Manufacturing method of battery with nickel pole - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing a battery, particularly an alkaline battery, having a non-sintered nickel electrode.

Conventional structure and its problems In general, the positive electrode of an alkaline battery has an electrode that uses silver oxide, manganese dioxide, air, etc. as an active material in addition to the nickel electrode, but it is stable in an alkaline aqueous solution and cannot be charged or discharged. Nickel electrode occupies the main stream because of its excellent reversibility and long life expectancy. In particular, nickel-cadmium batteries are a representative system of alkaline batteries, and it is expected that there will be great demand growth in the future.

In addition, nickel-zinc batteries and nickel-iron batteries are being developed especially for electric vehicles, and nickel-hydrogen batteries are beginning to be used mainly for special applications such as space applications.

As described above, the nickel electrode is widely used, and as the electrode structure thereof, the pocket type and the sintered type have recently been the mainstream. As is well known, the pocket type is obtained by mechanically filling nickel hydroxide with a conductive material such as graphite in a steel container having many holes. Therefore, the electrodes are robust in appearance, but the active material is present only in contact with the conductive material and the container (pocket), so that the polarization is large at a large current discharge and the utilization rate is low. Become. Further, there is a problem that the life is shortened under severe conditions such as rapid charging.

On the other hand, in the sintering method, the active material is firmly adhered to and filled in the sintered body having micropores, so there are few problems such as those seen in the pocket method, and high current Significant improvements have been made in terms of discharge characteristics, rapid charging characteristics, and life.

Therefore, from the characteristics alone, it can be said that the sintering method has reached the ideal stage. However, the process is complicated in both the structure of the sintered body and the filling of the active material, and there is a problem that it is considerably more expensive than the pocket type. A method has been developed in which a sponge-like metal porous body having a large pore size and a large porosity is used as an active material support instead of the sintering type, and a paste-like active material, that is, nickel hydroxide is directly filled into the active material support. The filling process is simplified.

A simpler method is the so-called paste method, in which a two-dimensional porous body such as a net, a perforated plate, or an ex-band metal is used as the core material, and the active material and the binder are mixed to form a paste. The above-mentioned product is applied, smoothed by passing it through slits or rollers, and after drying, pressure is applied if necessary. This method is ideal as a manufacturing method because the core material is extremely inexpensive and the active material is easily filled, and many proposals have been made.
Although the past type electrode has a long history and the manufacturing method is slightly different, the past type lead electrode plate is extremely widely used. Also, the cadmium electrode has been put to practical use.

On the other hand, the reason why the nickel electrode cannot be put to practical use despite the many proposals is as follows.

(1) Nickel, that is, neither nickel oxyhydroxide at the time of charging as an active material nor nickel mercuride at the time of discharging is an excellent conductor. Therefore, it is necessary to add a conductive material separately, and even if it is added, it is difficult to improve the utilization rate. Also, if added too much, the absolute capacity will be reduced.

(2) The volume of the active material changes as a result of repeated charging and discharging, but the nickel electrode swells violently.

Mainly, the above factors hinder the widespread practical use of the paste nickel electrode. That is, various binders have been conventionally considered as a method for increasing the strength and preventing the swelling as in (2) and the dropout of the active material due to the swelling.
Examples of the binder include polyethylene, polypropylene, polyvinyl chloride, polystyrene, fluororesin, polyvinyl alcohol, carboxymethyl cellulose, ethyl cellulose and the like. Of course, the former is superior in terms of electrolytic solution resistance and oxidation resistance, but if a large amount is added to improve the strength, the voltage characteristics will be inferior and the utilization factor will also decrease. Nickel powder or graphite was added to suppress this, but if added in a large amount, the proportion of the active material decreases, and if it is too small, there is a problem in that the utilization rate is small.

The above addition of the binder and other electrolytic solution resistant fibers can improve the characteristics and life of the paste type or pressure type nickel electrode, so-called non-sintered nickel electrode to some extent. Since it is far inferior to the type, it has not been widely used in practice.

An object of the present invention is to improve a non-sintered nickel electrode such as a pocket type electrode, an electrode using a sponge-like metal porous body as an active material support, a paste type electrode using a two-dimensional core material, and the like. Leaving the advantage of being able to be filled with an active material as it is, making it an excellent nickel electrode that brings discharge characteristics and life closer to the sintering type,
Moreover, the present invention provides a method for manufacturing a battery that further improves the characteristics of the battery provided with the battery.

Composition of the Invention The inventors used the active material by mixing nickel and cobalt in a paste positive electrode material mainly composed of nickel hydroxide and leaving it in a paste state preferably while being exposed to air. I proposed earlier that the rate will improve, and therefore, long life will be achieved by charging and discharging under a constant load.
The present invention relates to the improvement. That is, a non-sintered nickel electrode is manufactured using such a paste, and after forming a battery, especially an alkaline battery, which uses this nickel electrode as a positive electrode, it should be left in the battery state again before entering the formation. It is characterized by.

It is not clear why such two-time storage improves the utilization rate of the non-sintered nickel electrode, but
There is no doubt that it is the effect of cobalt, and it can be presumed that this two-time storage is effective because cobalt improves the charge and discharge efficiency of the nickel electrode.

Description of Examples As a specific example, a cylindrical sealed nickel-cadmium battery, which is the most popular among alkaline batteries, will be described below. As the size, a size equivalent to 2 was used. The cadmium negative electrode used was manufactured as follows. First, a cadmium oxide-based paste is applied to both sides of a nickel-plated iron punching metal, passed through a slit set to a predetermined thickness, and after a drying process, a 0.7 mm thick electrode plate is applied. Got Then, it was partially charged in a 10 wt% aqueous solution of caustic potash to change a part of the cadmium oxide into metal cadmium, further washed with water, dried and pressurized to a thickness of 0.63 mm.

A polyamide non-woven fabric was used for the separator, and 6.5 cc of a 25% by weight aqueous solution of potassium hydroxide dissolved in a small amount of lithium hydroxide was used as the electrolyte.

The nickel electrode was of the paste type and was manufactured as follows. The paste composition is 1 Kg of nickel hydroxide and 100 g of carbonyl nickel powder with a particle size that passes through a 200-mesh sieve, 50 g of graphite, 0.1 mm in diameter, 20 g of acrylonitrile-vinyl chloride copolymer fiber with a diameter of 3-5 mm, and carbonyl metal cobalt powder. 50 g and 1 kg of a 3% by weight aqueous solution of carboxymethyl cellulose.

In this example, the paste was left to air dry for 1 week at room temperature. The color changed from light black to dark brown, which is believed to be due to the cobalt being oxidized and diffused into the other mixture.

After that, water corresponding to water evaporated by drying was added and mixed well, and this was used as a paste.

The core material is a 0.11 mm thick iron plate with a hole diameter of 2 mm and a center-to-center pitch of 3 mm.
The punching metal that was perforated with nickel plating was used. Apply the paste on both sides of this core material, let it pass through the slit, and make the thickness after drying 1.0 ± 0.05 mm.
I chose The electrode plate thus obtained was first cut into a width of 120 mm and a length of 680 mm. Then, the mixture was pressed through rollers to impregnate an aqueous dispersion of tetrafluoroethylene resin (solid content: 15% by weight) and dried. The thickness of the electrode was 0.7 mm. This electrode was further cut into a size of 1. In this case, the width was 38 mm and the length was 220 mm. This was combined with the above-mentioned cadmium electrode and separator to form a battery.

After pouring the electrolyte solution into this, it was sealed and completed as a battery. In this example, this battery was left at 10 ° C. for 1,2,3,4,5,6 days. Each battery has A ₁ , A ₂ , A ₃ , A ₄ ,
And A _5, A _6. After that, charge at 0.1C for 15 hours, 0.8V at 0.2C
/ The cell discharge was repeated twice to form a cell.

Further, for comparison, a battery immediately entering the chemical conversion was added and designated as B. In addition, a battery in which the paste was not left and a battery was not left was added as C, and a paste was not left as it was and only left in the battery was left for 6 days at 10 ° C. as D.

The filling capacity of the batteries A to D and the utilization rate at each discharge,
The following table shows the cycle life, which is defined as the life when the charge and discharge were 0.15C and the discharge was 0.5C, and the life was 65% of the initial capacity.

As is clear from this table, even if the paste or the battery is left alone, it is effective in improving the utilization rate and life, but if both are performed, it will make a leap especially with high-rate discharge such as 2C. Improvement is recognized. In this example,
It was carried out at 10 ° C., but it is preferable to carry out the standing at 10 ° C. for about 6 days. It has been found that at lower temperatures, the number of days left is rather long, and at higher temperatures, it may be shorter. For example, at 30 ° C, it takes about 2 days.

Further, although the paste type electrode is described in the examples, it can be similarly applied to the electrode in which the sponge-like metal porous body is filled with the paste, and in the case of the pocket type electrode, a dry state one may be used, After assembling the battery, it may be left as in the other cases.

Effects of the Invention As described above, by using cobalt and graphite left in the presence of at least several hours or more in the presence of water in the coexistence of water and preferably in the paste and leaving them in a battery state, It is of great industrial value that can improve both utilization and life.

Claims (1)

[Claims] 1. A battery comprising nickel hydroxide as a main material, to which at least cobalt powder is added, water is further added, and the mixture is allowed to stand, and the mixture is used as a nickel electrode to form a nickel electrode again before forming the battery. A method for producing a battery having a nickel electrode, which is characterized in that the battery is left as it is.