JPS63141258A - Manufacture of hydrogen absorption alloy negative electrode - Google Patents

Abstract

PURPOSE:To solve the problem of a powdering and oxidation, and to manufacture a hydrogen absorption alloy in a simple way, by giving a mechanical powdering process to a hydrogen absorption alloy in an alkaline water solution, and then, washing and drying it to make a hydrogen absorption alloy negative electrode. CONSTITUTION:A specific alloy material is put in a ball mill which consists of a pot and balls, and furthermore, a potassium hydroxide solution of the specific gravity 1.30 is added at the ratio 50 ml to to the alloy 100 g. The powdering is carried out by the ball mill in such a condition. The powdered hydrogen absorption alloy power is washed in the water and dried. The hydrogen absorption alloy sample powdered in such an alkaline solution is made into a paste, spread together with polyvinylalcohol or the like over a punching metal plate with a nickel coating, and dried to obtain a negative electrode plate. By applying such a hydrogen absorption alloy to the hydrogen absorption alloy negative electrode for an alkaline storage battery, the conventional problem of powdering or oxidation can be solved, and at the same time, the hydrogen absorption alloy can be produced in a simple way.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for manufacturing a hydrogen storage alloy negative electrode using a hydrogen storage alloy that reversibly stores and releases hydrogen.
A pollution-free, high energy density alkaline storage battery can be provided.

BACKGROUND OF THE INVENTION Among various power sources, lead-acid batteries and alkaline batteries are widely used as secondary batteries.

The most widely used alkaline storage battery is the nickel-cadmium storage battery. Although this battery is quite superior in terms of performance, new battery systems are still being considered with high expectations for high-energy Umbrella TK and pollution-free performance.

For example, zinc has been used as a negative electrode instead of cadmium, but as is well known, it has problems with its lifespan, so it has not been widely put into practical use. & What has recently attracted attention is alkaline storage batteries that use hydrogen storage alloys for the negative electrode that reversibly absorb and release hydrogen. In this case, batteries can be constructed using the same treatment as cadmium, zinc, etc., and the actual dischargeable capacity density can be higher than that of cadmium, and there is no dendrite formation like with zinc, so it has a high energy density and a long life. , is promising as a pollution-free alkaline storage battery.

However, as hydrogen storage alloys repeatedly absorb and release hydrogen, they become more pulverized, and when used as a constituent material for battery electrodes, the electrodes become deformed and fall off. In alkaline storage batteries that absorb gas using the Neumann method, the surface is oxidized by oxygen gas generated from the positive electrode, resulting in a decrease in hydrogen storage and release capacity.

Therefore, when using a hydrogen storage alloy as a negative electrode, it is necessary to pulverize it before making it into an electrode so that it does not become further pulverized even after charging and discharging in the battery, and the performance may be affected by oxygen gas. It is important to improve oxidation resistance so that it does not deteriorate. In order to solve these problems, studies have been conducted to crush the hydrogen storage alloy as finely as possible and to coat the surface of the hydrogen storage alloy with an oxidation-resistant film. It has also been considered to extend the life of the pulverized hydrogen storage alloy by surface treating it with an alkaline aqueous solution.

Problems to be Solved by the Invention Although alkaline storage batteries using hydrogen storage alloys as negative electrodes are effective in improving high energy density, they have problems with pulverization and oxidation.

The purpose of the present invention is to solve the problems of pulverization and oxidation that have hitherto been a problem when this hydrogen storage alloy is used as a hydrogen storage alloy negative electrode for an alkaline storage battery, and at the same time to provide a simple method for manufacturing the hydrogen storage alloy. .

Means for Solving the Problems The present invention provides a hydrogen storage alloy characterized in that a hydrogen storage alloy is mechanically pulverized in an alkaline aqueous solution, and then at least washed with water and dried to form a hydrogen storage alloy negative electrode. This is a method for manufacturing an alloy negative electrode. Preferably, the alkaline aqueous solution is a caustic alkali having a specific gravity of 1.05 to 1.50, and the alkaline aqueous solution is heated to 30 to 80° C., and the hydrogen storage alloy is mechanically pulverized. It is particularly preferable to use the ball mill method.

By carrying out functional grinding in an alkaline aqueous solution, impurity phases that are relatively difficult to grind are dissolved in the alkaline aqueous solution, making it possible to achieve finer grinding in a short time.

Example First, the configuration of the present invention will be conceptually described.

When a hydrogen storage alloy is used as a negative electrode of an alkaline storage battery, the hydrogen storage alloy obtained by melting the alloy has been previously pulverized by hydrogenation or mechanical means.

The present invention employs a wet mechanical pulverization method for this pulverization step, and is characterized in that it is carried out in an alkaline aqueous solution.

Hitherto, after producing a hydrogen storage alloy, it has been pulverized into a fine powder, and then the hydrogen storage alloy powder or the hydrogen storage alloy negative electrode is treated with alkali in an alkaline aqueous solution. This alkali treatment can extend the life of a sealed battery by removing components that are easily soluble in caustic alkali, which is the electrolyte of alkaline storage batteries, and by making the surface of the hydrogen storage alloy powder not compatible with alkali. It has the effect of making it possible.

In other words, it aims to simplify the process by simultaneously performing the pulverization process and the alkali treatment process, which had previously been performed separately, and to make the conventional pulverization more effective by performing the two processes at the same time. It is. What is important here is that the hydrogen storage alloy negative electrode obtained by pulverization in caustic alkali as in the present invention has a longer lifespan than the hydrogen storage alloy negative electrode obtained by simply performing pulverization and alkali treatment separately. It is about demonstrating one's characteristics. The reason for this is presumed to be that the crushed surface of the new alloy immediately comes into contact with caustic alkali when the hydrogen storage alloy is crushed. By performing the pulverization in an alkaline aqueous solution, impurity phases that are relatively difficult to be pulverized are dissolved in the alkaline aqueous solution, making it possible to achieve finer pulverization in a short time.

Furthermore, the heat generated during crushing also has a positive effect.

In other words, pulverization in alkali promotes heating without special heating.

Hereinafter, specific examples of the present invention will be described.

Commercially available Mm (Mitshu Metal) Nil Co.

Each raw material of Mn and AI was weighed to a certain composition ratio and melted into MmN 13,6C00°5M in an argon arc melting furnace.
No. 4A I 0.3 alloy was produced. This alloy was then heat treated in a vacuum heat treatment furnace according to a known method.

This alloy sample was placed in a ball mill consisting of an alumina pot and a ball, and an aqueous potassium hydroxide solution having a specific gravity of 1.30 was added at a ratio of 50 ml per 100 g of the alloy.

In this state, ball mill pulverization was performed at room temperature for 10 hours. The temperature inside the ball mill at the end of this grinding is approximately 40°C.
Met. The pulverized hydrogen storage alloy powder was washed with water and then dried. When the particle size distribution of the alloy samples ground in this alkaline aqueous solution was measured, all of them were found to be fine powders of 50 microns or less.

The hydrogen storage alloy sample pulverized in an alkaline aqueous solution was then made into a paste with a binder such as polyvinyl alcohol, applied to a nickel-plated punched metal plate, and dried to obtain a negative electrode plate A.

The thus obtained negative electrode plate A was incorporated into a battery.
As an example of the battery, a AA cylindrical sealed nickel-metal hydride storage battery was used. Therefore, the negative electrode plate A thus obtained was cut to a width of 3.9 cm and a length of 26 cm, and lead plates were attached to two predetermined locations by spot welding.

For the phase equilibrium, a known sintered nickel electrode was selected and used, also having a width of 3.9 cm and a length of 22 cm. In this case as well, lead plates were attached at two locations.

A polyamide nonwoven fabric was used as the separator, and 20 g/L of lithium hydroxide was dissolved in a caustic potassium aqueous solution having a specific gravity of 1.20 as the electrolyte. The nominal capacity is 3. It is OAh. This battery is called A.

Next, for comparison, the conventional method uses the same M m as before.
N l 3. sCOo, 5M n □, 4A l O
, 3 alloys were selected and the hydrogen storage alloys were mechanically crushed to a particle size of 50 microns or less. The time required was 24 hours.

Thereafter, the negative electrode plate B was obtained by immersing it in an aqueous potassium hydroxide solution having a specific gravity of 1.30 at 40° C. for 10 hours to perform alkali treatment, thereby obtaining a battery B.

Since the capacity law of the positive electrode is used, the nominal capacity of this battery is also 3.
．． It is OAh.

Furthermore, for comparison, we used the same hydrogen storage alloy as before to
Negative electrode plate C was obtained by mechanically grinding for 4 hours to a size of 50 microns or less without alkali treatment, and the nominal capacity was 3.0 A.
A battery C of h was obtained.

The results of evaluating these batteries by ordinary charge/discharge cycle tests will be explained.

Charge up to 130% at 0.2C (5 hour rate) and discharge at 0.50C (2 hour rate) to a final voltage of 1. The battery was set to OV and the charge/discharge cycle was repeated. As a result, the discharge capacity of the three types of batteries A, B, and C was approximately 3.0A until about 100 cycles.
h, and no major difference was found except that the discharge terminal voltage of battery C was slightly lower than that of batteries A and H. However, when this charge/discharge cycle was repeated further, the discharge capacity of battery C suddenly decreased from the 142nd cycle. Further, battery B started to deteriorate from the 356th cycle. On the other hand, in Battery A of the present invention, no abnormality was observed up to 500 cycles.

From this, it became clear that the battery A of the present invention had the best life characteristics.

Effects of the Invention As described above, the method for manufacturing the hydrogen storage alloy negative electrode of the present invention is as follows:
The conventional process of pulverizing the hydrogen storage alloy and the alkali treatment process are performed at the same time, which not only simplifies the manufacturing process, but also particularly improves the charge/discharge life of the battery.

Claims (4)

[Claims] (1) A method for producing a hydrogen storage alloy negative electrode, which comprises mechanically pulverizing the hydrogen storage alloy in an alkaline aqueous solution, followed by at least washing with water and drying to form a hydrogen storage alloy negative electrode. (2) The alkaline aqueous solution is a caustic alkali with a specific gravity of 1.05 to 1.50, and the alkaline aqueous solution has a specific gravity of 30 to 80%.
The method for producing a hydrogen storage alloy negative electrode according to claim 1, wherein the hydrogen storage alloy negative electrode is heated to a temperature of .degree. (3) The method for producing a hydrogen storage alloy negative electrode according to claim 1 or 2, wherein the step of mechanically pulverizing the hydrogen storage alloy is particularly a ball milling method. (4) Hydrogen storage according to claim 1, 2 or 3, characterized in that the hydrogen storage alloy is mechanically pulverized in an alkaline aqueous solution to a particle size of 100 microns or less. Method for manufacturing alloy negative electrode.