JPH07107842B2 - Hydrogen storage battery - Google Patents

Description

TECHNICAL FIELD OF THE INVENTION The present invention relates to a hydrogen storage battery having an improved hydrogen storage electrode as a negative electrode.

[Technical background of the invention and its problems]

A hydrogen storage battery using a hydrogen storage electrode has attracted attention because of its high energy density.

One of the methods for producing the above-mentioned hydrogen storage electrode is a method using a binder. That is, it is a method of mixing a powder of a resin (polytetrafluoroethylene, polyethylene or the like) as a binder and a hydrogen storage alloy, and rolling or heating to form a sheet.

However, the hydrogen storage electrode using this binder has a drawback that becomes an obstacle in practical use. One is that the ability as a storage battery cannot be exhibited from the beginning. That is, in the first few cycles of charging / discharging, a phenomenon occurs in which 100% of the amount of electricity during charging cannot be extracted during discharging.

As one of the causes of this phenomenon, it is considered that the electrolytic solution is not sufficiently permeated into the hydrogen storage electrode. The hydrogen storage alloy is brought into a charged state by decomposing water in the alkaline aqueous solution during storage and storing the generated hydrogen. Therefore, the hydrogen storage alloy particles in the electrode not in contact with the electrolytic solution cannot store hydrogen during charging and cannot be used as an active material. Therefore, even if the amount of hydrogen storage alloy contained in the electrode, which is expected from the amount of hydrogen-absorbing alloy, is charged, while the penetration of the electrolytic solution into the electrode is not sufficient,
Only a part of the amount of electricity supplied is used to store hydrogen in the hydrogen storage alloy, and therefore the same capacity as during charging cannot be taken out during discharging. Therefore, preliminary charge / discharge for activating the battery is required during the manufacturing process.

[Object of the Invention]

An object of the present invention is to provide a hydrogen storage battery capable of extracting a sufficient discharge capacity from the first charge / discharge.

[Outline of Invention]

The present invention is a hydrogen storage battery comprising a positive electrode, an electrolytic solution, and a sheet-shaped hydrogen storage electrode containing an adhesive as a main constituent material of a hydrogen storage alloy, and the area of the negative electrode is larger than that of the positive electrode. The hydrogen storage battery is characterized in that a thin groove is provided on the surface of the negative electrode.

Specifically, in the method of manufacturing the electrode, first, the binder and the hydrogen storage alloy are mixed. The types of hydrogen storage alloys are LaNi ₅ ,
A ternary or quaternary alloy obtained by substituting MnMi ₅ and some of these Ni with other metal elements such as Al, Mn, Fe, Co, Ti, Cu, Zn, Zr and Cr. Alternatively, some or all of La and Mn are replaced with Ca, and further Mg ₂ Ni-based, TiMn-based, TiN
i-based and TiFe-based alloys are shown. However, the present invention is not particularly limited to these, and in the present invention, any material may be used as long as it causes an electrode reaction in an alkaline electrolyte.

Further, as the binder, polytetrafluoroethylene,
Alternatively, polyethylene or the like is used, but the method for producing the electrode differs depending on the type of the binder, so some explanation will be added below. First, when polytetrafluoroethylene is used, it is mixed with a hydrogen storage alloy, kneaded, then formed into a sheet, and the current collector is pressure-bonded to form an electrode. When polyethylene is used, it is mixed with a hydrogen storage alloy and then pressed and heated together with a current collector to form a sheet, which is used as an electrode.

Next, a thin groove is provided in the electrode formed into a sheet as described above.
As this method, it suffices to cut the electrode with a knife or the like, but as an easy method, it can be proposed to use a roller to which a large number of flat blades are attached.

The fine groove provided as described above can promote the permeation of the electrolytic solution into the electrode.

〔The invention's effect〕

According to the hydrogen storage alloy electrode of the present invention, it becomes easy for the electrolytic solution to soak into the electrode, and the discharge capacity can be sufficiently extracted from the initial charge and discharge. Therefore, it can be said that the industrial value is great in that the preliminary charge / discharge for activating the battery can be removed from the manufacturing process.

Example of Invention

Next, the present invention is applied to an AA Ni / H ₂ battery (rated 500 mA) having a nickel oxide (NiOOH) positive electrode and a negative electrode made of a hydrogen storage alloy of LaNi _4.7 Al _{0.3 with} an equilibrium plateau pressure of 0.4 atm at 25 ° C.
An example applied to the production of h) will be described with reference to FIG.

First, LaNi _4.7 Al _0.3 is made into a powder having a particle size of 20 μm or less, and this is mixed with polyethylene particles. Then, put this mixture in a mold together with nickel current collector 3 (wire diameter 0.125 mm, 40 mesh), while heating to 160 ° C,
It was formed into a sheet with a pressure of 0.2 ton / cm ² . Next, this sheet was taken out from the die, and a fine groove 2 was provided on the surface of the sheet with a roller having a large number of flat blades made of stainless steel attached, and the dimensions were set to 80 mm × 40 mm × 0.5 mmt to obtain a hydrogen storage electrode 1 as a negative electrode. Nickel electrode as the positive electrode (dimensions 70 mm x 40 mm x
0.6 mmt) was prepared, and this and the negative electrode were spirally wound with a separator interposed therebetween to produce a unit cell. Subsequently, the unit cell was inserted into a metal battery case, the negative electrode lead 4 was connected to the battery case, and the positive electrode lead was connected to the positive electrode terminal of the sealing plate by resistance welding. Next, 8M-
The KOH aqueous solution was injected into the battery case, and the battery was sealed to complete the battery assembly.

When the ratio of the discharge capacity to the charge capacity in the charge / discharge cycle test of the battery of this example was examined, the characteristic diagram shown in FIG. 2 was obtained. A in FIG. 2 is the characteristic of this embodiment. As a comparative example, a battery having the same specifications as those of the above-described examples was manufactured except that no fine groove was formed on the electrode surface. That is, the battery of this comparative example is a battery based on the conventional manufacturing method. The characteristics of the battery of this comparative example are shown in FIG.
Shown in.

As is apparent from FIG. 2, the battery of the comparative example does not reach 100% up to about 10 cycles, but the battery of this example can discharge almost 100% from the beginning.

〔The invention's effect〕

As described above in detail, according to the present invention, it is possible to provide a hydrogen storage battery that can take out a sufficient discharge capacity from the first charge / discharge cycle.

[Brief description of drawings]

FIG. 1 is a schematic view of a hydrogen storage electrode of the present invention in which a fine groove is provided on the electrode surface, and FIG. 2 shows changes in the ratio of the discharge capacity to the charge capacity in the charge / discharge cycle test of the present example and comparative example. It is a characteristic diagram. 1 ... Hydrogen storage electrode, 2 ... Fine groove, 3 ... Nickel current collector, 4 ... Negative electrode lead.

Claims (1)

[Claims] 1. A hydrogen storage battery comprising a positive electrode, an electrolytic solution, and a sheet-shaped hydrogen storage electrode mainly containing a hydrogen storage alloy as a negative electrode and containing a binder, wherein the area of the negative electrode is greater than that of the positive electrode. A hydrogen storage battery, which is large in size and has a narrow groove formed on the surface of the negative electrode.