JPH0462753A - Hydrogen absorbing alloy pole - Google Patents

Abstract

PURPOSE:To maintain a capacity for a long time by mixing together hydrogen absorbing alloy powder and polypropylene resin powder, and applying heat treatment thereto in vacuum atmosphere around its melting point so as to form a negative pole. CONSTITUTION:A slurry 1 made by adding a methylcellulose aqueous solution 3 to a carbonil nickel powder 2 and mixing them together is applied to both faces of a porous sheet 4. After the slurry 1 is applied to both faces of the porous sheet 4 which is nickel-plated on iron, it is dried and sintered so as to produce a porous nickel sintered substrate 5. A nickel active material 6 is filled into the pores of the porous nickel sintered substrate 5 so as to obtain a required nickel plate 7, then a positive pole 8 is produced by cutting the nickel plate 7. Then, polypropylene resin powder is added to alloy powder 11, which is obtained by hydrogenating LaNi4.7Al0.3 of hydrogen absorbing alloy 10 and pulverizing it, and uniformly mixed together. This is filled into a nickel wire 13, press-molded and rolled so that a hydrogen absorbing alloy pole 14 can be obtained. And the hydrogen absorbing alloy pole, which is obtained by applying heat treatment to the pwole 14 in vacuum atmosphere around its melting point, becomes a negative pole 15.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a negative electrode for an alkaline storage battery that uses hydrogen as a negative electrode active material, and particularly to a hydrogen storage alloy electrode that can absorb and release hydrogen.

(Prior art and problems to be solved by the invention) Hydrogen storage alloys used in electrodes differ from cadmium, iron, etc., which have traditionally been used as negative electrode active materials, and when charged and discharged in an alkaline electrolyte, Absorbs hydrogen, which is an active material,
It is something that is emitted.

In such a hydrogen storage alloy electrode, unsintered PTFE is used as a binder.
(polytetrafluoroethylene), PE (polyethylene), etc. have been used, but they have the disadvantage that the alloy lattice is deformed due to absorption and release of hydrogen, resulting in pulverization of the alloy particles.

In addition, in such conventional hydrogen storage alloy electrodes, the pulverized alloy falls off from the electrode due to the volume change of the hydrogen storage alloy, resulting in a decrease in capacity, and the mechanical strength and conductivity of the electrode decrease due to the effect of pulverization. There was a problem in that it was difficult to maintain the electrode plate capacity over a long period of time.

Therefore, the present invention was made in view of the above circumstances, and an object of the present invention is to provide a hydrogen storage alloy electrode in which hydrogen storage alloy powder and polypropylene (p, p) resin powder are mixed and heat treated at a temperature near the melting point. That is.

(Means for Solving the Problems) Therefore, the present invention was made in view of the above-mentioned circumstances, and consists of hydrogen storage alloy powder and polypropylene (P).

P) It is an object of the present invention to provide a hydrogen storage alloy electrode mixed with resin powder and heat-treated at a temperature near the melting point.

As a means for solving the above object, the present invention is characterized in that a hydrogen storage alloy powder and a polypropylene resin powder used as a binder are mixed and heat treated in a vacuum atmosphere near the melting point to form a negative electrode. It is something to do.

(Function) Polypropylene (p, p) resin powder has a melting point at a relatively low temperature, and if it is uniformly dispersed with the alloy powder, the binding network of polypropylene (p, p) resin powder will be uniform after heat treatment. is formed.

On the other hand, polypropylene (p, p) has good elongation characteristics, so it can cope with expansion and contraction of the alloy volume, and also can prevent falling off, so that the conductivity between the alloys can be maintained.

Therefore, even if pulverization occurs, there will be no falling off, a decrease in capacity is suppressed, and the mechanical strength of the electrode is maintained, so that the electrode plate capacity can be maintained over a long period of time.

(Example) Next, the present example will be described based on FIGS. 1 to 3.

1 to 3 are schematic explanatory diagrams showing one embodiment of the present invention.

Slurry 1 is a mixture of carbonyl nickel powder 2 and methylcellulose (MC) aqueous solution 3, and slurry 1 is applied to both sides of porous sheet 4.

The porous sheet 4 is made of iron plated with nickel.

After applying the slurry 1 to both sides of the porous sheet 4, it is dried and sintered to produce a porous nickel sintered substrate 5.

The pores of the porous nickel sintered substrate 5 are filled with nickel active material 6 to obtain the required nickel electrode plate 7.

The nickel electrode plate 7 is cut to form a positive electrode 8.

The specific dimensions of the positive electrode 8 are approximately 41 mm in width and 70 m in height.
6-order hydrogen storage alloy 10 m, thickness 0.65 mm
LaNi4. tA! LaNi4.lo3 obtained by powdering it by hydrogenation. r Af2o3 hydrogen storage alloy powder 11,
Polypropylene (p, p) resin powder 12 was mixed with LaNi4.
yAI2゜, 5wt, % based on the weight of hydrogen storage alloy powder
Add and mix evenly.

Then, this is filled into a nickel wire mesh 13 of 30 mesh, pressure-molded at a pressure of 1 to 4 ton/am'', and further rolled to obtain a hydrogen storage alloy electrode 14 having a thickness of approximately 0.4 mm.

The thus obtained hydrogen storage alloy electrode 14 was placed in a vacuum atmosphere 1.
A hydrogen storage alloy electrode obtained by heat treatment at 60° C. for 0.5 to 1 hour is referred to as a negative electrode 15.

The specific dimensions of the negative electrode 15 are approximately 41 mm in width and 100 mm in height.
, the thickness is 0.4 mm.

The positive and negative electrode plates 8, 15 and the nylon separator 20 (thickness 0.2 mm) are used to form a rolled-up electrode plate group 21, which is inserted into a nickel-plated iron can 22 to form a cylindrical sealed battery 2.
3.

The battery 23 obtained as described above will be described below as battery A.

On the other hand, the positive electrode 8 is the same as that of battery A, and the negative electrode 15 is made of La
Ni4. tAβ. 5 alloy powder and unsintered PTFE (polytetrafluoroethylene).

Using the positive and negative electrode plates thus obtained, a cylindrical sealed battery similar to that of battery A was produced, and this was designated as battery B.

Furthermore, the same positive electrode 8 as in battery A was used, and the negative electrode 15 was made into a paste by adding a thickener, to which polyethylene powder was added and an electrode plate made by heat treatment at 120'C was used.

Using the positive and negative electrodes thus obtained, a cylindrical sealed battery similar to that of battery A was produced, and this was designated as battery C.

Then, the following charge/discharge cycle test is performed using the A, B, and C batteries.

FIG. 4 is a characteristic diagram showing the relationship between the number of charge/discharge cycles and discharge capacity.

This charge/discharge cycle test consisted of charging at 140mA for 56h.
After charging, the battery was further charged at 70 mA for 2 hours, and then discharged at 140 mA with a final voltage of 1 V.

Cycles are carried out under these charging and discharging conditions, and the results are reported in the fourth
As shown in the figure.

As shown in FIG. 4, as the cycle progresses, the decrease in capacity of batteries B and C increases.

This is because the alloy falls off from the electrode due to the pulverization of the hydrogen storage alloy that is the negative electrode material, and the mechanical strength and conductivity of the electrode are reduced due to this effect.

On the other hand, B and C batteries lose their capacity relatively quickly, whereas A battery maintains a high capacity for a relatively long period of time.

This is because the binding network of polypropylene (P, P) resin powder and the elongation, which is a resin property, effectively absorb volume changes due to expansion and contraction of the two alloys, suppressing falling off due to pulverization, and improving the mechanical strength of the electrode. This is because deterioration in conductivity was also prevented.

(Effects of the Invention) As described above, the hydrogen storage alloy electrode of the present invention retains the hydrogen storage alloy by heat-treating polypropylene (P, P) resin powder, and stores and releases hydrogen as an active material. By doing so, it is possible to significantly prevent the hydrogen storage alloy from becoming pulverized and falling off, and it is possible to maintain the capacity over a long period of time by suppressing the decrease in the capacity of the electrode plate and the decrease in the mechanical strength and conductivity of the electrode.

[Brief explanation of the drawing]

1 to 3 are schematic explanatory diagrams showing one embodiment of the present invention, and FIG. 4 is a characteristic diagram showing the relationship between the number of charge/discharge cycles and discharge capacity. In the figure, 11... Hydrogen storage alloy powder, 12... Polypropylene resin powder, 15... Negative electrode. T, gp;

Claims (1)

[Claims] A hydrogen storage alloy electrode characterized in that a negative electrode is formed by mixing hydrogen storage alloy powder and polypropylene resin powder used as a binder and heat-treating the mixture in a vacuum atmosphere near its melting point.