JPS61161659A - Manufacture of hydrogen storage electrode - Google Patents

Abstract

PURPOSE:To obtain a hydrogen storage alloy having steady performance for a long time by adding transition metal ion complex to a solution in which a hydrogen storage metal is activated. CONSTITUTION:A substance which dissolves in a solution evolves hydrogen is mixed as an additive in a hydrogen storage alloy. The mixture is immersed in a solution containing transition metal ion complex and stirred. The hydrogen storage alloy is activated by hydrogen generated in the solution. Residual insoluble metal and transition metal are carried on the hydrogen storage alloy and the alloy is washed to obtain a hydrogen storage electrode. By repeating charge and discharge, the transition metal carried on the hydrogen storage alloy covers the surface of hydrogen storage alloy by its migration. The transition metal adsorbs and reduces active gas such as oxygen generated during overcharge. Therefore, the hydrogen storage alloy retains steady reversible hydrogen absorption and desorption for a long time.

Description

[Detailed Description of the Invention] Technical Field The present invention relates to a method for producing a hydrogen storage electrode that is effective for use as a negative electrode of an alkaline storage battery, etc. The present invention relates to a method for producing a hydrogen storage electrode that is effective for use as a negative electrode of an alkaline storage battery, and is directed to a method for producing a hydrogen storage electrode that exhibits stable characteristics over a long period of time. It is planned.

<Prior Art> A MeOx-Me'Hy type storage battery using a metal oxide as a positive electrode active material and a hydrogen storage alloy as a negative electrode active material has been proposed, and its practical use is being promoted.

As the positive electrode active material, Ni0OH, Ag2O, etc., which are used as the positive electrode of conventional alkaline storage batteries, are considered suitable, and as the negative electrode active material, LaNi 5. Ti2Ni
The use of hydrogen storage alloys whose hydrogen equilibrium dissociation pressure at room temperature is IPa to IMPa is being considered.

In order to create an electrode using a hydrogen storage electrode as an active material,
The following steps are required.

(1) Production of hydrogen storage alloy with arbitrary composition.

(2) Mechanical crushing of alloy ingots.

(3) Pulverization of the alloy by hydrogen activation treatment.

(4) Polyethylene, silicate agents such as Teflon, and copper.

Addition and mixing of conductive agents such as nickel.

(5) Support on current collector.

(6) Heat treatment of electrode forming agent.

Among these series of operations, step (3) is performed in a high temperature, high pressure hydrogen atmosphere, and therefore this step alone requires very large-scale equipment. Furthermore, after the hydrogen activation treatment, if the hydrogen storage alloy comes into contact with active gases such as oxygen, the hydrogen absorption and release characteristics of the hydrogen storage alloy will deteriorate, so it must be kept in an inert atmosphere at all times. This deterioration of properties is due to the inert film formed by oxygen, acid carbon oxide, ice water vapor, decrease in the amount of hydrogen that can be reversibly absorbed and released, increase in the hysteresis of the equilibrium dissociation pressure during the hydrogen absorption and release process, Symptoms include a plateau decrease in equilibrium hydrogen dissociation pressure.

In order to restore a degraded hydrogen storage alloy to its original state, hydrogen reduction must be performed in a high temperature and high pressure hydrogen atmosphere, or
Alternatively, electrolytic reduction must be carried out in an electrolytic solution for a long time, which is not an easy task.

When a MeOx-Me'Hy type storage battery is constructed with a fully activated hydrogen storage electrode as the negative electrode and a metal oxide as the positive electrode, and is repeatedly charged and discharged over a long period of time, the discharge capacity gradually decreases. To go. This is also caused by the active gas present in the battery, and the inert film that forms as a result of gas poisoning causes a reduction in the amount of hydrogen that can be reversibly absorbed and released, and a deterioration in the two-polarization characteristics. Such disorders appear. The active gas here is oxygen, which is mixed in when assembling the battery.

- It is thought that it is carbon oxide and oxygen gas generated from the positive electrode during overcharging. If it is an open type storage battery, the negative electrode can be electrolytically reduced by charging for a long time.
The balance between the charge states of the positive and negative electrodes will be disrupted. Furthermore, if the battery is a sealed type, charging for a long time tends to damage the battery, making it impossible to ensure practical reliability.

<Objective of the Invention> The present invention solves the above-mentioned problems, and aims to provide a method for manufacturing a hydrogen storage electrode that is effective as a negative electrode of an alkaline storage battery and can maintain stable characteristics over a long period of time. do.

Description of Structure and Effects> In order to achieve the above object, the present invention provides a hydrogen storage alloy in which a substance such as various Raney alloys such as nickel-aluminum, which dissolves by itself in a solution such as an acid or alkali and generates hydrogen, is added as an additive. By immersing this mixture in a solution containing transition metal ion complexes and stirring, the hydrogen storage alloy is activated with the hydrogen generated in the solution, and the insoluble metals and transition metals that remain after the gas is dissolved are activated. The structure is characterized in that a transition metal obtained from an ion complex is supported on a hydrogen storage alloy, and then washed and molded into an electrode shape, thereby obtaining a hydrogen storage electrode. Hydrogen generated in a solution is obtained through a chemical reaction between the solution and additives, and is called nascent hydrogen, which is extremely active and is said to have an activation force equivalent to several thousand atmospheres of hydrogen gas. There is. Therefore, this nascent hydrogen can be used to easily activate the hydrogen storage alloy in solution in a short time. The insoluble metal remaining after dissolution has a very high activity and can be supported on the hydrogen storage alloy. The transition metal ions in the transition metal complex are easily reduced by hydrogen in the nascent hydrogen or activated hydrogen storage alloy, and can become fine metal particles.

These metal fine particles also have high activity and can be easily deposited and supported on the hydrogen storage alloy.

According to the present invention, the activation of the hydrogen storage alloy is carried out quickly and easily while the surface of the hydrogen storage alloy is cleaned by the cleaning action of the solution, and the activated mixed powder is not dried. It can be compression molded into an electrode shape in a wet state, and there is no need to operate it in an inert atmosphere.
Work efficiency is dramatically improved. The obtained hydrogen storage electrode is
It has a high electrical capacity due to activation treatment, and due to repeated charging and discharging over a long period of time, the transition metal supported on the hydrogen storage alloy causes migration silane in the hydrogen storage electrode and covers the hydrogen storage alloy. Become. These transition metals can adsorb and reduce active gases such as oxygen generated during overcharging, and can protect hydrogen storage alloys from being poisoned by active gases.
A stable and reversible amount of hydrogen absorption and release can be maintained over a long period of time. In addition, this transition metal can increase the contact area between the hydrogen storage alloy and the current collector, leading to improved polarization characteristics and active material utilization. That is,
To establish a manufacturing technology suitable for practical use of hydrogen storage electrodes, since electrodes with good characteristics suitable for storage batteries etc. can be obtained using a simple manufacturing method and equipment, suitable for mass production, and manufacturing costs are low. I can do it.

Ca is a substance used as a hydrogen storage alloy.

Elements that easily combine with hydrogen such as Mg, Ti, Zr, Hf, V, Nb, Ta, Y, or lanthanide elements, and An, C
r.

Alloys with elements that are difficult to bond with hydrogen, such as Fe, Ni, Co, Cu, Mn, and Si, are used, and substances that generate hydrogen by reacting with solutions such as acids and alkalis include alkali metals, Alkaline earth metal I An l F e +
Single elements with higher ionization tendency than hydrogen such as Ni+ Sn or Ni-AI, Ni-S i, Cu-A
Various Raney alloys such as J.

There are various other materials. The transition metal ion complex to be added to the solution has various transition metals as the central metal, and NH3, H2O, CN, SCN, CO and other various inorganic ligands as the ligands, or EDTA, NH2CH2.
Materials such as CH2NH2 and various other organic ligands can be used.

<Example> Below, T1Ni is used as a hydrogen storage alloy, and Cu-AJI is used as a substance that generates hydrogen by reacting with a solution such as acid or alkali.
Raney alloy and transition metal ion complex [Cu
(NH3)4) Hydroxylation power with addition of (OH)z + J S
The details of the production method of the present invention will be explained using an example in which an aqueous solution of silica is used as the reaction solution.

T1Ni alloy powder with a particle size of 44 μm or less and Cu: 50w/
%-A4: 50'v/w% Raney alloy powder was weighed out at a weight ratio of 5:3 and mixed until uniform. The concentration of CCu(NH3)4)(OH)2 is 3
0'I/12 potassium hydroxide aqueous solution at 70''C
The mixture of the T1Ni alloy powder and the Raney alloy powder is gradually added into the solution which has been heated to a temperature and stirred thoroughly. At this time, Aλ in the Cu-A1 alloy reacts with an alkali to generate aluminate ions and hydrogen gas. Even after all the mixtures have been added, the temperature of the solution is kept at 70° C. and stirring is continued until no hydrogen gas is generated. During this operation, the copper ammonia complex is decomposed and copper fine particles are deposited on the active sites of the activated hydrogen storage alloy with the generation of ammonia gas.

After the reaction is completed, the mixture is washed with a large amount of water, and when re-soluble aluminate ions are no longer observed, the supernatant liquid is poured out, and the suspension is added and kneaded so that the fluorine resin becomes 8W/w96. Make a paste. This paste was filled into a punched nickel plate as a current collector, compression molded at a pressure of 1+/ad, and then pre-dried in an argon gas atmosphere for 30 minutes.
An electrode is produced by performing heat treatment at 0° C. for 1 hour. Through the above steps, a hydrogen storage electrode using T1Ni as the negative electrode active material is obtained.

For comparison, a hydrogen storage electrode was fabricated by the process shown in the prior art, and its performance was compared with the hydrogen electrode of this example. In addition, except for the manufacturing method, the T1Ni alloy composition, binder content, conductive agent content, and molding pressure are different.

The heat treatment temperature, etc. are all set to the same conditions.

The attached drawings show the results of characterizing the electrode as a hydrogen storage electrode using a standard mercury-mercury oxide reference electrode in the same electrolytic cell. The figure shows the effect of repeated charge-discharge operations on the discharged tN and capacity of a hydrogen storage electrode. Curve A is the characteristic curve of the hydrogen electrode obtained in this example, and curve B is the characteristic curve of the hydrogen electrode produced by the conventional method. Charging was performed by discharging to -0.75V with respect to hydrogen storage. It can be seen that the hydrogen storage electrode obtained by the manufacturing method of this example has a higher active material utilization rate and a longer life than the hydrogen storage electrode obtained by the conventional method. Therefore, the hydrogen storage electrode of this example is effective as a negative electrode of an alkaline storage battery, and can maintain stable characteristics over a long period of time.

[Brief explanation of drawings]

The drawing is a characteristic diagram showing the relationship between the number of charging and discharging cycles of a hydrogen storage electrode and the discharge capacity.

Claims (1)

[Claims] 1. A mixture consisting of a hydrogen storage alloy mixed with an additive that reacts with a solution to generate hydrogen is immersed in the solution, the hydrogen storage alloy is activated with the generated hydrogen, and then molded into an electrode shape. A method for manufacturing a hydrogen storage electrode, comprising adding a transition metal ion complex to the solution.