JPS62154562A - Hydrogen absorbing alloy electrode - Google Patents

Abstract

PURPOSE:To safely manufacture in a short time without need of treatment with hydrogen and without use of a complicated and expensive manufacturing facility by bonding mechanically crushed hydrogen absorbing alloy powder having a pore size of 20-149mum with a resin. CONSTITUTION:Particle size of hydrogen absorbing alloy powder is specified to 20-149mum. If the powder having a particle size less than 20mum is used, a battery having high performance is cannot obtained. If the particles size of the powder exceeds 149mum, particles in an electrode break and come off f the electrode during repeated charge-discharge to decrease the life of the battery. The amount of resin used as a binder is limited to 0.5-4wt.% based on the alloy powder. If the amount of the resin is less than 0.5wt.%, the strength of the electrode is insufficient, and if it exceeds 4.0wt.%, the capacity of the electrode is insufficient. Use of water repellent fluorine resin is preferable as the binder.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to improvements in hydrogen storage alloy electrodes used in sealed nickel oxide hydrogen storage batteries and the like.

[Technical background of the invention and its problems]

Conventionally, hydrogen storage alloy electrodes used, for example, in sealed nickel oxide/hydrogen storage batteries have been manufactured as follows. First, an ingot of a hydrogen storage alloy is placed in a heat-resistant and pressure-resistant container, and after the pressure inside the container is reduced to, for example, 10' torr, the container is filled with hydrogen at 10 to 30 atm while cooling as necessary. In this way, hydrogen is stored in the alloy, and after reaching saturation, the temperature inside the container is raised to about 60 to 80° C., and the hydrogen in the container is removed by suction with a vacuum pump, thereby releasing the hydrogen stored in the alloy. After hydrogen is completely released, the container is again filled with hydrogen at 10 to 30 atmospheres to cause the alloy to store hydrogen. Such hydrogen storage and
The releasing operation is repeated several times to powderize the hydrogen storage alloy. Next, the hydrogen storage alloy powder is formed into a sheet shape in an inert gas to produce a hydrogen storage alloy electrode.

However, the above-mentioned method requires complicated and expensive production equipment, is dangerous because it uses high-pressure hydrogen gas, and has disadvantages in that it requires a long time for processing.

[Purpose of the invention]

The present invention has been made to eliminate the above-mentioned drawbacks, and aims to provide a hydrogen storage alloy electrode that does not require treatment using hydrogen and can be manufactured safely and in a short time without complex and expensive manufacturing equipment. It is something to do.

[Summary of the invention]

The present inventors have discovered that even hydrogen-absorbing alloy powder mechanically pulverized in air can exhibit high battery performance if a hydrogen-absorbing alloy electrode is manufactured with a defined particle size. It's arrived.

That is, the hydrogen storage alloy electrode of the present invention is characterized in that mechanically pulverized hydrogen storage alloy powder having a particle size of 20 to 149p is bound with a resin.

Such a hydrogen storage alloy electrode does not require powdering treatment using hydrogen, so it does not require complicated and expensive production equipment, can be produced safely and in a short time, and is very inexpensive.

In the present invention, the particle size of the hydrogen storage alloy powder is 20 to 149.
The reason for specifying the IER is that if the particle size is less than 20p, high battery performance cannot be obtained, while if it exceeds 149p, the particles will break and fall off during repeated charging and discharging after making the electrode, shortening the lifespan. . A particularly preferable particle size range is 37 to 14
It is 9p.

Further, in the present invention, the proportion of the resin mixed as a binder is preferably 0.5 to 4% by weight based on the hydrogen storage alloy powder. This is because if the amount of resin is less than 0.5% by weight, the strength of the electrode will not be sufficient, while if it exceeds 4.0% by weight, the capacity of the electrode will not be sufficient. Further, as the resin, it is desirable to use a water-repellent fluororesin or the like.

[Embodiments of the invention]

The present invention will be explained in detail below.

First, LmN i Mn A, +7 (
However, 4.2 0. An ingot of a hydrogen-absorbing alloy with a composition of B O12 Lm (La-rich Mitsushmetal) was placed in a ball mill in the air,
Pulverized for minutes. After that, sift it to 100 to 200
mesh (149-741m), 200-300 mesh (74-46p), 300-400 mesh (4
6-37p), 400-635 pages (37-20
p), 653 mesh passes (20 or less).

Next, 4.0.2.0% polytetrafluoroethylene (PTFE) was added to each particle size of hydrogen storage alloy powder.
．． After mixing at a ratio of 0.5% by weight and forming into a sheet, each was pressed onto a nickel wire mesh current collector at a pressure of 400 kg/α2 to produce a hydrogen storage alloy electrode.

A battery was constructed using these hydrogen storage alloy electrodes and a large capacity nickel electrode as a counter electrode, and a charge/discharge test was conducted.

Note that the discharge capacity when the charge/discharge efficiency was 100% was defined as the performance of the hydrogen storage alloy electrode. The results are shown in the table below.

In addition, considering the actual usage conditions, the batteries produced using the electrodes of Examples 1 to 4 and Comparative Example 1 were charged from the beginning at a current density of 171 mA/g-M per 1 g of alloy for 1 hour, and the discharge capacity was The cycle in which the amount reached 171 mAh/g-M or more was measured. The results are shown in FIG.

As is clear from the above table, when an electrode made of hydrogen storage alloy powder with a particle size of 20- or less is used as in Comparative Examples 1 to 3, the battery performance is extremely low, whereas in Examples 1 to 3, the battery performance is extremely low.
When an electrode made of hydrogen storage alloy powder with a particle size of 20 to 149p as in Example 2 is used, high battery performance is exhibited. Furthermore, there is a tendency for performance to improve as the amount of PTFEffl as a binder decreases. This is considered to be because PTFE is water repellent and the reduced content of PTFE improved contact between the hydrogen storage alloy and the electrolyte.

Furthermore, as is clear from FIG. 1, the battery using the electrode of Comparative Example 1 had a low discharge capacity, whereas the battery with a particle size of 20 to 14
When the electrodes of Examples 1 to 4 made of 9p hydrogen storage alloy powder were used, the output was 171 mA from the second cycle.
It exhibits a discharge capacity exceeding h/g-M, and has extremely high practical value when used as an actual battery.

In addition, in the above explanation, La-Ni-based LmN i Mn A,i? Although only the quaternary alloy 4.2 0.8 0.2 has been described, other Ti-Ni system, Ca-Ni
system, Mg-NL system, Ti-Cr system, Ti-Fe system, Ti
Similar effects can be expected for the -V series and the La-Co series.

〔Effect of the invention〕

As detailed above, according to the present invention, it is possible to provide an inexpensive hydrogen storage alloy electrode that can be manufactured safely and in a short time without requiring complicated and expensive manufacturing equipment.

[Brief explanation of drawings]

FIG. 1 is a characteristic diagram showing the results of a charge/discharge cycle test of batteries manufactured using the hydrogen storage alloy electrodes of Examples 1 to 4 of the present invention and Comparative Example 1.

Claims (3)

[Claims] (1) A hydrogen storage alloy electrode characterized in that mechanically crushed hydrogen storage alloy powder having a particle size of 20 to 149 μm is bound with a resin. (2) The hydrogen storage alloy electrode according to claim 1, wherein the resin is mixed in an amount of 0.5 to 4% by weight based on the hydrogen storage alloy powder. (3) The hydrogen storage alloy is La-Ni type, Ti-Ni type, C
a-Ni series, Mg-Ni series, Ti-Cr series, Ti-Fe
The hydrogen storage alloy electrode according to claim 1, characterized in that the hydrogen storage alloy electrode is mainly composed of at least one type selected from the group consisting of Ti-V, Ti-V, and La-Co.