JP2548431B2 - Nickel-metal hydride battery conversion method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a chemical conversion method for a nickel-hydrogen storage battery using a hydrogen storage alloy for a negative electrode.

2. Description of the Related Art Lead-acid batteries and alkaline batteries are widely used as various types of power sources. Among them, the alkaline storage battery can be expected to have high reliability and can be made compact and lightweight. For this reason, the compact type has been used for various portable devices and the large type has been used for industrial purposes.

In most of the alkaline storage batteries, the positive electrode is a nickel electrode. The characteristics have been improved from the pocket type to the sintering type, and the sealing has been made possible and the use has expanded.

On the other hand, cadmium electrodes are mainly used as the negative electrode at present, but nickel-hydrogen storage batteries using metal hydrides, that is, hydrogen storage alloy electrodes have attracted attention in order to achieve a higher energy density, and many proposals have been made for manufacturing methods. ing.

Problems to be Solved by the Invention There are two methods for producing a hydrogen storage alloy electrode: a method of sintering an alloy powder and a method of filling or applying a porous material such as foamed, fibrous, or punched metal. Since hydrogen storage alloys are relatively excellent in electron conductivity in the same manner as cadmium electrodes, the possibility of non-sintered electrodes is great. That is, the hydrogen-absorbing alloy powder is made into a paste together with a binder, and the paste is filled or applied to a porous conductive plate having a three-dimensional or two-dimensional structure. However, in any case, there is room for improvement particularly in the discharge characteristics at the beginning of the charge / discharge cycle.
AB ₂ Lav based on Zr-Ni as a hydrogen storage alloy
In the alloy containing the es phase, the capacity eventually becomes high, but the initial activation is a problem. The present invention solves such a problem, and an object of the present invention is to provide a chemical conversion method for a nickel-hydrogen storage battery that exhibits excellent characteristics from the initial stage.

Means for Solving the Problems In order to solve this problem, the method for chemical conversion of the nickel-hydrogen storage battery of the present invention is to construct a battery using a nickel positive electrode, a hydrogen storage alloy negative electrode and a separator, and insert the battery into a battery case, injecting an electrolytic solution. Later, as it is or as a closed type, it is charged at a temperature of 0 to 10 ° C and discharged at a temperature of 40 to 60 ° C to perform formation. The hydrogen storage alloy used for the negative electrode is preferably an alloy containing AB ₂ Laves phase based on Zr-Ni.

With this configuration, the method for chemical conversion of the nickel-hydrogen storage battery of the present invention is based on the hydrogen storage alloy powder, especially Zr-Ni based AB
Alloys containing ₂ Laves phases will eventually have high capacities but low initial capacities. Therefore, chemical conversion is more important than other battery systems. However, the capacity increase is comparatively small by simply repeating the warm charge and discharge as the formation of a general battery, and many charge and discharge cycles were required until the original capacity was reached.

It conducts formation by charging at a specific low temperature and discharging at a high temperature as described above, and more preferably 3 times the negative electrode capacity.
Since the improvement was achieved by charging a large capacity such as more than double, it is effective to keep the hydrogen generation state from the electrode during charging for a long time for the alloy to function as the electrode. all right. Moreover, the lower the temperature is from 0 to 10 ° C, the better the charging efficiency of the hydrogen storage alloy.

Even if the battery structure is based on the positive electrode law like other batteries, the negative electrode law will occur if a discharge at room temperature is applied during formation where the negative electrode capacity is insufficient. At very high temperatures. As a result, the negative electrode law is not established, and thus oxidation during oxidation is less likely to be unfavorable to the alloy, resulting in a longer life.

In the case of other storage batteries, if the battery is hermetically sealed and hydrogen is generated from the negative electrode, hydrogen is not absorbed unless it is also used as a catalyst, so the internal pressure of the battery rises. However, hydrogen storage alloys, especially those based on Zr-Ni and containing the AB ₂ Laves phase, have the ability to store hydrogen and the catalytic ability to return hydrogen and oxygen to water from the beginning, so the internal pressure of the battery rises and gas No leakage will occur.

Example Hereinafter, a method of forming a nickel-hydrogen storage battery according to an example of the present invention will be described. As a hydrogen storage alloy, ZrMn _0.6 Cr _0.2 Ni _1.2 , which is one of the AB ₂ Laves phase alloys, was crushed and the paste made by adding carboxymethyl cellulose solution was filled in a foam nickel plate with porosity 95% and thickness 1.0 mm. A pressure was applied to obtain a hydrogen storage alloy electrode. After drying under reduced pressure, a 5% fluororesin dispersion was added to reinforce. This hydrogen storage alloy electrode was cut into a width of 33 mm and a length of 210 mm, and a lead plate was attached by spot welding.

A sealed nickel-hydrogen storage battery was constructed using a known foamed nickel electrode as a counter electrode and a hydrophilic non-woven polypropylene separator. The capacity of the negative electrode with respect to the positive electrode was set to 4 Ah (140%). After that, an electrolytic solution in which 25 g / l of lithium hydroxide was dissolved in a caustic potash aqueous solution having a specific gravity of 1.25 was injected. The battery was a Sub C type. The nominal capacity is 2.8Ah.

Using 10 cells of this battery, formation was performed at an ambient temperature of 10 ° C. for 15 hours at a current of 300 mA and discharge at 300 mA at 50 ° C. to a terminal voltage of 0.8 V was repeated twice. This battery is designated as A.

Next, as an example of conventional chemical conversion method, room temperature 20
Charged at 300mA for 15 hours at ℃ -Battery which was discharged at terminal temperature of 0.8V up to 0.8V at room temperature of 300mA was added twice, and was designated as B.

When the discharge voltage and capacity after chemical formation were examined, the average voltage of A was 1.24 V and the discharge capacity was 2.8 to 2.9 Ah. However, in B, it took 8 to 11 cycles to show the same characteristics as in A.

Next, using 10 cells of each battery, we compared the life characteristics under the charge and discharge conditions of 130% charge at 400 mA and discharge to 0.8 V at -1 A. As a result, the discharge capacity of A is 1000 cycles
The ratio of B was 75-78%, while the ratio of 82-85% was shown, and the performance of A was stable over a long period.

Although the closed type is described in the embodiment, the open type has the same effect.

EFFECTS OF THE INVENTION As is clear from the above description of the embodiments, according to the nickel-hydrogen storage battery chemical conversion method of the present invention, excellent characteristics can be obtained from the initial stage of charge and discharge, and the effect of being able to maintain this for a long period of time can be obtained. You can

Front page continuation (72) Inventor Hajime Hajime 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (56) Reference JP-A-2-267872 (JP, A) JP-A-4-61756 ( JP, A) JP-A-4-62763 (JP, A)

Claims (2)

(57) [Claims] 1. A nickel-hydrogen storage battery which is formed by using a nickel positive electrode, a hydrogen storage alloy negative electrode and a separator, and is then charged at a temperature of 0 to 10 ° C. and discharged at a temperature of 40 to 60 ° C. Chemical conversion method. 2. A hydrogen storage alloy of AB ₂ based on Zr-Ni.
The method for forming a nickel-hydrogen storage battery according to claim 1, which comprises a Larvus phase.