JPS60130054A - Metal-oxide hydrogen battery - Google Patents

Abstract

PURPOSE:To produce a long-life negative electrode which consists of a hydrogen- absorbing alloy and from which the alloy can not be separated by using a noncrystalline hydrogen-absorbing alloy as the hydrogen electrode. CONSTITUTION:An Ni.Zr-system alloy, an AB5-system alloy such as LaNa5 or a ternary alloy represented by the formula AB5-xDx can be used as a noncrystalline hydrogen-absorbing alloy. For the above noncrystalline hydrogen-absorbing alloy, an AB-system alloy such as FeTi and an A2B-system alloy such as Mg2Ni can also be used. Besides, nickel oxyhydroxide, silver oxide or similar compound can be appropriately selected for a metal oxide electrode used as a positive electrode. After NiOOH electrodes 2 used as positive electrodes are placed on both sides of a negative electrode 1 consisting of the above noncrystalline hydrogen- absorbing alloy with separators 3 interposed, the thus formed body is firmly fixed with a holder 4. After that, the thus obtained body is installed in a case 6 containing 8N-KOH solution 5, thereby completing a battery.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a so-called metal oxide/hydrogen battery in which a metal oxide electrode is used as a positive electrode and a hydrogen electrode is used as a negative electrode. It concerns metal oxide/hydrogen batteries that are being formed.

[Technical background of the invention and its problems]

Metal oxide hydrogen batteries that use hydrogen storage alloy negative electrodes are attracting attention as secondary batteries with high energy density.
One of the problems is that the life of the hydrogen storage alloy negative electrode is not necessarily long. In other words, a negative electrode made of a hydrogen storage alloy gradually loses its capacity through repeated charging and discharging. The reason for this is that the alloy particles constituting the negative electrode repeatedly expand and contract due to absorption and release of hydrogen during charging and discharging, and as a result, the alloy particles become even more finely divided and no longer remain in the electrode body and fall off.

This is usually unavoidable when using a hydrogen storage alloy in a crystalline state (forming a metal phase as polycrystals).

[Purpose of the invention]

The present invention has been made to solve the above-mentioned drawbacks.
The object of the present invention is to provide a hydrogen storage alloy negative electrode that does not cause alloy to fall off from the electrode and therefore has a long life, and as a result, to provide a metal oxide/hydrogen battery with excellent life characteristics.

[Summary of the invention]

The present invention is characterized in that a metal oxide hydrogen battery uses an amorphous hydrogen storage alloy for its hydrogen electrode. Unlike polycrystalline alloys, amorphous hydrogen storage alloys do not become pulverized even when they store hydrogen. The reason for this is that the strain caused by hydrogen absorption is alleviated by the extra voids (free volume) present in the amorphous alloy. However, when an amorphous hydrogen storage alloy is used as an electrode, it does not become pulverized even if it absorbs hydrogen through cathodic polarization (charging), so it does not fall off from the electrode support and has a long life. Become.

The amorphous hydrogen storage alloy used in the present invention is Ni-Zr.
It may be an ABlI-based alloy represented by LaNi or a ternary alloy such as ABlI-XDX. Further, an AB-based alloy represented by FeTi, or an A, B-based alloy represented by MgzNt may be used.

Furthermore, as a metal oxide electrode as a positive electrode.

Nickel oxyhydroxide (Ni 0OH), silver oxide (Ag
zO and Ag0), etc. can be selected as appropriate.

Furthermore, as the binder, materials other than PTFE may be used. That is, it may be made of, for example, polyvinyl alcohol, polyethylene, or other fluororesin, as long as it is alkali resistant and has a binding effect. It is permissible to heat the formed electrode body to the extent that the amorphous state does not return to a crystalline state.

[Embodiments of the invention]

Next, the present invention will be explained using examples. A Ni-Zr alloy was used as a hydrogen storage alloy for the negative hydrogen electrode, and a nickel oxide (Ni00H) electrode was used for the positive electrode.

First, a hydrogen storage alloy was created as follows.

Granular nickel with a purity of 99.9% (approximately 1 tea in diameter) and granular zirconium with a purity of 99.7% (approximately 0.2 tea in diameter)
) were mixed at an atomic ratio of 64:36 and heated at about 1000° C. for 2 hours in an arc melting furnace containing argon to uniformly melt the mixture. After this, add a diameter of 0.5 to the tip.
The molten alloy was introduced into a crucible having a tm orifice, and under argon pressure, the alloy was forced out through the orifice at the tip and dropped between two metal rolls. Each of these rolls is made of copper and rotates rapidly in the direction of compressing the molten alloy, which cools the molten alloy rapidly at the same time as it is rolled, resulting in a thickness of 50 μm.
m, it becomes a ribbon-shaped amorphous alloy with a width of 1 mm. At this time, the two rolls are constantly blown with argon gas to prevent the alloy from oxidizing. Sounds good, the cooling rate of the alloy at this time is 10~l Q K7's
It is about ec. It was confirmed that the alloy produced in this way was an amorphous alloy because no clear interplanar spacing was observed in the powder X-ray method.

Next, the above amorphous alloy was mechanically crushed to a particle size of 100 μm.
m or less. Specific gravity 1.5 containing 60 inches of polytetrafluoroethylene (PTFE) for this alloy powder 1001
15 cc of dispersion (13.5 F as PTFE solid content)
) and mixed well to form a sheet-like mixed wire body with a thickness of 0.5 mm. Then, from this point, 3 cm
Two pieces having a size of 5α were cut out, placed on both sides so as to sandwich a nickel net, and then crimped to form an electrode body. The weight of the electrode alloy made of the amorphous hydrogen storage alloy thus produced was 6.02.

Next, as shown in cross section in FIG. 1, Ni0OH electrodes 2 as positive electrodes are placed on both sides of the negative electrode 1 made of this amorphous hydrogen storage alloy with a separator 3 in between, and are firmly fixed with a holder 4. After that, the battery was placed in a case 6 containing an 8N-KOH solution 5 to complete the battery. At this time, N i OOH
The electrode capacitance of the electrode was set to be sufficiently larger than that of the hydrogen storage alloy electrode.

Next, charging and discharging cycles were repeated at room temperature, and the discharge capacity at each cycle was measured. Charging is 3
00mA for 4 hours, discharge at 300mA and battery voltage is 1V
I went until The results are shown in FIG. 2 (curve A). For comparison, curve B shows the results of a battery in which a crystalline alloy instead of an amorphous one was used as a hydrogen electrode.

In this method, metals having the same composition as in this example were mixed, melted in an arc furnace containing argon, and then slowly cooled as they were.The obtained alloy was used as a hydrogen electrode, and the electrode body was prepared. The method is the same as in this example.

As can be seen from Figure 2, there is almost no difference in discharge capacity for the first 20 cycles or so, but as the number of cycles increases, the capacity decreases in the comparative example, whereas the capacity in the inventive example decreases. It is clear that the decrease is slight.

〔Effect of the invention〕

As described above, according to the present invention, a metal oxide hydrogen battery using a long-life hydrogen storage alloy electrode as a hydrogen electrode has been realized, and is said to be extremely useful industrially.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing a configuration example of a metal oxide/hydrogen battery according to the present invention, and FIG. 2 is a curve diagram showing an example of characteristics of a metal oxide/hydrogen battery according to the present invention. Negative electrode) 2... Metal oxide electrode (positive electrode) 3... Separator

Claims (1)

[Claims] A metal oxide/hydrogen battery comprising a positive electrode made of a metal oxide and a hydrogen electrode as a negative electrode. A metal oxide/hydrogen battery characterized by using an amorphous hydrogen storage alloy as a hydrogen electrode.