JPS6070665A - Electrode which can absorb hydrogen - Google Patents

Abstract

PURPOSE:To increase the life of an electrode for an alkaline storage battery by using as an alloy powder which can absorb and discharge hydrogen and which has specified grain diameters. CONSTITUTION:An alloy consisting of a Ti-Ni alloy or the like composed of Ti and Ni in an atomic ratio of 2:1 and has the property of electrochemically absorbing and discharging hydrogen is prepared by fusion. The thus prepared alloy is crushed into a powder with grain diameters of 25mum or below. The thus prepared alloy powder is mixed with ethyl alcohol to make a muddy mixture which is then packed into a foamy porous nickel body or the like. The thus obtained body is then dried and pressed before being sintered, thereby making an electrode which can absorb hydrogen. By using this electrode, it is possible to constitute a non-polluting alkaline storage battery of a high energy density.

Description

[Detailed description of the invention] Industrial applications The present invention reversibly stores hydrogen as a negative electrode material.

This research relates to a hydrogen storage electrode using a hydrogen-emitting alloy, and is expected to produce a non-polluting, high-energy-density alkaline storage battery.

Conventional configuration and its problems Electrochemically absorbs hydrogen in alkaline electrolyte.

A method has been proposed in which the released alloy is used as a negative electrode material for alkaline storage batteries. In combination with the nickel positive electrode used in nickel-cadmium storage batteries, nickel-iron storage batteries, etc., a nickel-hydrogen alkaline storage battery can be created. This battery is cheap.

Because it does not use Mium, it is non-polluting during manufacturing and disposal after use. In addition, there is little change in the concentration of the electrolyte during charging and discharging, and a long life can be expected.

As negative electrode materials for hydrogen storage electrodes, titanium-nickel alloys, lanthanum-nickel alloys, and the like are generally used. The manufacturing method is to mix alloy powder and binder,
There are two types: non-sintered electrodes that are pressure-formed and sintered electrodes that are obtained by heating in a vacuum or inert atmosphere. Regardless of which method is adopted, the hydrogen storage electrode absorbs hydrogen through charging and discharging.
The discharge is repeated, accompanied by a change in the volume of the electrode plate. As a result,
This may cause cracks in the electrode plates, alloy powder falling off, and a decrease in discharge sensitivity and cycle life.

As a solution to this problem, a method using finely divided alloy powder has been proposed (Japanese Patent Publication No. 53-103910
#). According to this method, a sealed container is filled with alloy,
The alloy is repeatedly hydrogenated and dehydrogenated by pressurization and heating to form a fine hydrogen. Therefore, the grinding process is complicated.

Additionally, once hydrogenated, it is difficult to completely dehydrogenate, and if removed from a closed container in such a state, the finely divided alloy powder is active and there is a risk of ignition in the air. Care must be taken when handling.

OBJECTS OF THE INVENTION It is an object of the present invention to provide a hydrogen storage electrode with a large discharge capacity and a long life, thereby enabling a battery with high energy density.

Components of the Invention The present invention obtains a homogeneous hydrogen storage alloy in an arc melting furnace or a high frequency melting furnace, coarsely crushes the alloy, and then sends compressed air to inject the powder onto a collision plate at supersonic speed. This is a hydrogen storage electrode using an alloy powder with a particle size of .

Description of Examples Commercially available rod-shaped titanium (purity 99.5%) and commercially available nickel (purity 995 or higher) were weighed at a weight ratio of 62:38, and an alloy composition was obtained in which the atomic ratio of titanium to nickel was Make it 2 to 1.

This sample is synthesized into a homogeneous alloy in an arc melting furnace in an argon atmosphere. After that, it is coarsely ground to less than 1 o mesh,
Compressed air was sent through a commercially available supersonic jet mill to pulverize the mixture. The alloy powder obtained using this apparatus had a particle size distribution as shown in FIG. For comparison, an example of the particle size distribution of an alloy powder pulverized by a vibratory pulverizer, which is a type of mechanical pulverizer, is also shown.

These powders were sieved into six grades of alloy powders a to e with particle sizes shown in the table.

On the other hand, a foamed nickel porous body with a nickel lead plate welded in advance (size 50 x 60 mm, thickness 1.0 mm)
, a porosity of 95 cm) was filled with about 6 y of each of the above five types of powders by slurrying them with ethyl alcohol. After drying and pressurizing, vacuum sintering was performed at 960° C. for 1 hour, and the product was placed on a hydrogen storage electrode.

These hydrogen storage electrodes and a known nickel positive electrode are combined to form a nickel-hydrogen storage battery, and alloy powder a-
Batteries obtained from electrodes using e were designated as A to E. In addition, in these batteries, the nickel positive electrode is an electrode with an actual capacity of sAh, so that the capacity decrease occurs at the hydrogen storage electrode.
As the solution, an aqueous potassium solution with a specific gravity of 1 was used.

Next, these batteries were charged at a charging current of 4 o mA for 10
The time and discharge current are 40077ZA and the battery voltage is 0.9■
The discharge continued until FIG. 2 shows the number of charging/discharging cycles and the change in discharge capacity per y of the alloy used when charging and discharging were repeated under these conditions. As is clear from these results, the discharge capacity of the battery A using the active particles is large, and the capacity decrease due to charging and discharging is small.

The reason why the discharge capacity of the battery obtained using the fine alloy powder was increased is considered to be that the specific surface area was increased, and the amount of hydrogen absorbed and released was increased.

Furthermore, it is considered that part of the alloy surface was oxidized due to the micronization in the air. It is thought that this oxidized alloy surface was electrochemically reduced by the initial charge and changed into an alloy with a large specific surface area and high activity. Furthermore, it can be inferred that the reason why the capacity reduction of the electrode using the gauge alloy powder was small is due to the miniaturization.

Normally, when this type of electrode is charged and discharged, the alloy powder becomes finer. The reason why this can reduce the occurrence of cracks in the electrode plate and the phenomenon of alloy powder falling off is that by using a material that has been refined from the beginning, the degree of refinement due to charging and discharging can be reduced. Conceivable. moreover,
It is thought that one of the factors that was effective in reducing the capacity was that due to the miniaturization, the degree of sintering progressed and a strong sintered body was obtained under the same sintering conditions.

The weight ratio of commercially available lanthanum metal and nickel metal is 32.1.
Each was weighed at a ratio of 67.9 to 67.9. Below T i2
An alloy having an atomic ratio of lanthanum to nickel of 1:50 was obtained in the same manner as in the case of Ni, which was pulverized and sieved to the particle size range shown in the table. The electrode manufacturing method was similar to that described for Ti2Ni, and hydrogen storage electrodes were obtained using alloy powders f to j, and nickel-hydrogen storage batteries F and J were produced and charged and discharged. The results are shown in FIG.

Further, commercially available calcium metal and nickel metal were weighed at a weight ratio of 12:88, and melted in a high frequency melting furnace in an Alcon atmosphere to obtain an alloy with an atomic ratio of calcium and nickel of 1:5. Using this alloy, Ti2Ni
According to the method described above, the ~0 alloy powder was sieved into 6 stages.

These were used as hydrogen storage electrodes, and 10'i of nickel-hydrogen storage batteries were fabricated. Figure 4 shows the results of charging and discharging these ponds under similar conditions.

From these results, LaNi5. The hydrogen storage electrode using an alloy of CaNi5 has T shown in the explanation (1) of the implementation column.
Similar to the electrode using the 12N1 alloy, the finer the electrode, the larger the discharge capacity and the better the cycle characteristic. It can be inferred that this is because the characteristics were changed for the same reason as described in the explanation (1) of the embodiment.

In addition, in the description of the embodiment, a method was shown in which compressed air was sent to make the alloy fine, but an inert gas such as nitrogen or carbon dioxide gas may also be used.

According to this method, even if particles are injected at higher speeds, there is no danger of ignition due to atomization as in air. Therefore, further miniaturization became possible and the properties as a hydrogen storage electrode were improved.

Based on the above results, the present invention has developed a hydrogen storage electrode that stores and releases hydrogen by charging and discharging in an alkaline N solution, using a powder obtained by simply pulverizing an alloy in air. It is used as an electrode material and has great industrial value because it has a hydrogen storage electrode structure with excellent electrode properties.

[Brief explanation of drawings]

FIG. 1 is a particle size distribution diagram of alloy powder, and FIGS. 2 to 4 are charging and discharging curves of alkaline storage batteries using hydrogen storage electrodes made of different materials. Name of agent: Patent attorney Toshio Nakao and one other person W,
1 Fig.TizN;)n8'lN8'lN8'lN8'lN8'lN8'lN8'lN8'lN8'lN8'lNunshuTachiko011'') Fig.2 Charging and discharging characteristics of Ti2Ni. Charging and discharging characteristics of LaNt's

Claims (3)

[Claims] (1) Electrochemically absorbing hydrogen with a particle size of 25 μm or less,
A hydrogen storage electrode that uses a releasing alloy powder. (2) The hydrogen storage electrode according to claim 1, wherein the alloy is composed of titanium and nickel, and its composition is represented by an atomic ratio of titanium to nickel of 2:1. (3) The hydrogen storage storage according to claim 1, wherein the alloy is composed of lanthanum or calcium and nickel, and the composition thereof is an alloy in which the atomic ratio of lanthanum to nickel and calcium to nickel is 1 to 5. electrode 0