JPH0763006B2 - Method for manufacturing hydrogen storage electrode - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing a hydrogen storage electrode using a hydrogen storage alloy that reversibly stores and releases hydrogen. Can be provided.

2. Description of the Related Art Lead storage batteries and alkaline storage batteries are widely used as secondary batteries among various power sources.

The most widely used alkaline storage battery is the nickel-cadmium storage battery. Although this battery is considerably superior in performance, there are still high expectations for high energy density and pollution-free, and new battery systems are being investigated.

For example, zinc has been picked up in place of cadmium in the negative electrode, but it is not widely used because it has a problem in life as well known.

Recently, attention has been paid to alkaline storage batteries that use a hydrogen storage alloy that reversibly stores and releases hydrogen as the negative electrode. In this case, a battery can be constructed in the same manner as cadmium and zinc, and the actual dischargeable capacity density can be made larger than that of cadmium, and there is no formation of dendrites such as zinc and electrode shape changes. It is a promising alkaline storage battery with high density, long life and no pollution.

As a method for producing a hydrogen storage electrode using this hydrogen storage alloy, conventionally, a hydrogen storage alloy is applied to a three-dimensional metal porous body such as a sintered type or a foamed metal or metal fiber in which a hydrogen storage alloy is sintered to obtain an electrode. The method of filling with a binder and the like was often used.

However, the method for manufacturing a hydrogen storage electrode by these methods has problems such as high material cost and complicated manufacturing process.

On the other hand, a so-called paste-type hydrogen storage electrode obtained by previously kneading a hydrogen storage alloy powder and a binder etc. into a paste, applying this to a metal two-dimensional porous body such as punching metal, expanded metal or metal net and then drying. The manufacturing method of (3) is characterized in that the manufacturing method is simple and an inexpensive electrode can be obtained because an expensive material such as a metal three-dimensional porous body is not used.

Problems to be Solved by the Invention This hydrogen storage alloy powder and a binder or the like are kneaded in advance to form a paste, which is applied to a metal two-dimensional porous body such as punching metal, expanded metal or metal net, and then dried. The method for producing the paste-type hydrogen storage electrode to be obtained is characterized in that an electrode that is originally simple and inexpensive can be obtained, but if an alkaline storage battery is constructed using the electrode obtained by this method, there are the following problems. It was not used much until now.

That is, the main problem is that the conventional hydrogen storage alloy is sintered to obtain an electrode by a sintering method or a method of filling a hydrogen storage alloy with a binder or the like into a metal three-dimensional porous body such as foam metal or metal fiber. The conductivity of the electrode was poorer than that of the electrode, and there was a problem in the large-current charge / discharge characteristics. The discharge voltage was greatly reduced, which was a serious problem in practical use.

INDUSTRIAL APPLICABILITY The present invention improves the conductivity of a paste type hydrogen storage electrode using a metal two-dimensional porous body such as punching metal, expanded metal, metal net, etc., which is easy to manufacture and can be manufactured at low cost, and is excellent in rapid charge / discharge characteristics. Another object of the present invention is to provide a method for manufacturing a hydrogen storage alloy electrode.

Means for Solving the Problems The present invention is to prepare a paste by kneading a hydrogen storage alloy powder, a binder, a paste viscosity modifier, etc. in advance, and use this as a punching metal, expanded metal, metal net or other two-dimensional porous body. On the surface of the electrode plate obtained by applying
Further, the present invention is a method for manufacturing a hydrogen storage electrode, characterized in that a porous conductive layer is formed.

Action Paste-type hydrogen storage electrodes that use a two-dimensional metal porous body such as punching metal, expanded metal, or metal net as a core material are hydrogen storage alloys on a three-dimensional metal porous body such as a sintered type, foam metal, or metal fiber. The conductivity of the electrode is obviously poor as compared with the electrode of the type in which is filled with a binder or the like. However, the present invention can improve the conductivity of the electrode even in a paste type hydrogen storage electrode using a metal two-dimensional porous body as a core material by further forming a porous conductive layer on the surface of this electrode plate. It is possible to obtain a hydrogen storage alloy electrode for an alkaline storage battery, which has excellent characteristics even if it is charged and discharged rapidly. Further, since these conductive layers are porous, the electron conduction between the hydrogen storage alloy powders is improved and the ionic conduction is not adversely affected. Furthermore, the ability to absorb oxygen gas generated during overcharge of the sealed alkaline storage battery, which is an important characteristic of the hydrogen storage electrode, is further improved, and the charge / discharge cycle life is improved.

Examples Examples of the present invention will be described below.

Commercially available Mm (Misch metal), Ni, C as hydrogen storage alloy
Raw materials of o, Mn, and Al were weighed to have a constant composition ratio, and an MmNi _3.8 Co _0.5 Mn _0.4 A _10.3 alloy was manufactured by an argon arc melting furnace. Then, this alloy was heat-treated in a vacuum heat treatment furnace according to a known method, and then this alloy sample was pulverized to have a particle size of 400 mesh or less.

A 5% (by weight) solution of polyvinyl alcohol in ethylene glycol, 0.8% by weight of polyethylene fine powder and 0.5% of vinyl chloride-acrylonitrile short fibers were added to the hydrogen storage alloy thus obtained, and the mixture was kneaded to form a paste. And This paste is applied to a nickel-plated punching metal plate made of iron with a thickness of 0.15 mm, a hole diameter of 1.8 mm, and a porosity of 50%, smoothed through a slit of 0.6 mm width,
Then, it was dried at 120 ° C. for 1 hour to obtain a hydrogen storage electrode.

The hydrogen storage electrode thus produced was further subjected to pressure pressing, and then various porous conductive layers were formed on the surface of the hydrogen storage electrode as the hydrogen storage electrodes A to L as described below. For comparison, a hydrogen storage electrode M that does not form a porous conductive layer was added.

Hydrogen storage electrode A-electroless copper plating Hydrogen storage electrode B-electroless nickel plating Hydrogen storage electrode C-electrolytic copper plating Hydrogen storage electrode D-electrical nickel plating Hydrogen storage electrode E-electrical (copper + nickel) plating Hydrogen storage electrode F -Nickel powder coating Hydrogen storage electrode G-Carbon powder coating Hydrogen storage electrode H- (Carbon + Palladium) powder coating Hydrogen storage electrode I-Palladium deposition Hydrogen storage electrode J-Platinum deposition Hydrogen storage electrode K-Nickel deposition Hydrogen storage electrode L- Copper Vapor Deposition Hydrogen Storage Electrode M-Without Porous Conductive Layer The hydrogen storage electrodes A-M thus obtained were subsequently evaluated as a sealed nickel-hydrogen secondary battery in the C2 form.

That is, each of the above-mentioned hydrogen storage electrodes was cut into a width of 3.9 cm and a length of 26 cm, and lead plates were attached to predetermined two places by spot welding. A well-known foamed nickel electrode was selected as a counter electrode and used with a width of 3.9 cm and a length of 22 cm. Also in this case, the lead plates were attached at two places.

The separator is a polyamide nonwoven fabric, and the electrolyte is 20 g of lithium hydroxide in a caustic potash aqueous solution with a specific gravity of 1.20.
It was dissolved and used. The nominal capacity is 3.0 Ah.

These batteries are tested at 20 ° C by a normal charge / discharge cycle test.
The results evaluated in Section 2 will be explained.

Charge up to 130% at 0.2C (5-hour rate), discharge at 0.5C
(2 hour rate) with a final voltage of 0.8 V and repeating the charge / discharge cycle up to 10 cycles, and then charging at 0.5 C (2 hour rate) up to 150% and discharging at 1.0 C (1 hour rate). The test was conducted.

From the results, the hydrogen discharge electrodes A to M used to construct the AA sealed nickel-hydrogen secondary battery and the battery discharge capacity and the intermediate discharge in the charge / discharge cycle test at 20 cycles and 200 cycles. The potential relationships are summarized in the table.

As is clear from the table, the discharge capacity of the hydrogen storage electrode M, which does not form the porous conductive layer, was significantly lower than the nominal capacity of 3.0 Ah at 200 cycles, and the intermediate discharge potential was also greatly reduced. Furthermore, when the battery internal pressure during charging of this battery was examined, it was found that the maximum internal pressure was 10 kg / cm ² or more, and the gas absorption capacity was insufficient.

On the other hand, the battery composed of the hydrogen storage electrodes A to L is very excellent in both the discharge capacity and the intermediate discharge potential, and the hydrogen storage alloy is bonded to the conventional metal three-dimensional porous body such as foam metal or metal fiber. It had a performance comparable to that of the electrode obtained by the method of filling with the agent. The internal pressure of these batteries when charging is 3.2 to 8.7 at the maximum.
It had a high gas absorption capacity of kg / cm ² , and among them, the one in which the porous conductive layer was formed by electroplating or electroless plating of copper or nickel was particularly excellent.

And as the porous conductive layer, copper, nickel, carbon,
Palladium, platinum, etc. are suitable, and for forming the porous conductive layer, plating method, coating method, spraying method, vapor deposition method,
The spatter method etc. can be applied. Of these, the most effective method is to form the porous conductive layer by electroplating or electroless plating of copper or nickel.

As described above, in the method for producing a hydrogen storage electrode of the present invention, when a sealed battery is configured, the original characteristic of the production is simple and the cost can be reduced, and the conductivity and the gas absorption capacity can be improved. Since the electrode strength is also improved, it is possible to provide a battery having a high capacity, a long life, and an excellent rapid charge / discharge characteristic.

Claims (3)

[Claims] 1. A hydrogen storage alloy powder binder and a paste viscosity modifier are kneaded in advance to form a paste, and the paste is applied to a metal two-dimensional porous body such as punching metal, expanded metal or metal net, and dried. A method for producing a hydrogen storage electrode, characterized in that a porous conductive layer is further formed on the surface of the obtained electrode plate. 2. A porous conductive layer comprising copper, nickel, carbon,
The method for producing a hydrogen storage electrode according to claim 1, wherein the hydrogen storage electrode is formed of at least one of palladium and platinum. 3. The method for producing a hydrogen storage electrode according to claim 1, wherein the porous conductive layer is formed by electroplating or electroless plating of copper or nickel.