JPH0745282A - Nickel electrode for alkaline storage battery - Google Patents

Abstract

PURPOSE:To provide a nickel electrode excellent in charging efficiency at the time of high temperature by preventing oxygen generation which is decomposition reaction of an electrolyte at charging time. CONSTITUTION:In a plate using nickel hydroxide serving as an active material, a metal element of zinc, cadmium, cobalt, lead, copper, ruthenium, indium or tungsten in a corrosion region by an alkaline water solution is contained in a particle fine hole of this nickel hydroxide. In this way, oxygen generating potential is shifted to negative, to obtain high oxygen overvoltage.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nickel electrode for an alkaline storage battery used in a nickel-cadmium battery or a nickel metal hydride battery.

[0002]

2. Description of the Related Art As a positive electrode of an alkaline storage battery such as a nickel-cadmium battery or a nickel metal hydride battery, a sintered electrode plate or a nickel fiber porous body in which a porous nickel sintered body is impregnated with nickel hydroxide as an active material. A paste type electrode plate filled in a substrate such as is used. It is known that when these nickel electrode plates are charged at a high temperature, the oxidation reaction of nickel hydroxide and the decomposition reaction (oxygen generation reaction) of the electrolytic solution proceed at the same time, resulting in an extreme decrease in charging efficiency. . The development of nickel electrodes that have excellent charging efficiency at high temperatures has become a major issue. Conventionally, to prevent this,
Adding solid solution such as zinc or cadmium to nickel hydroxide,
It has been practiced to shift the oxygen generation potential to a noble level and increase the oxygen overvoltage by a method of mixing these compounds or incorporating them into the particle surface.

[0003]

However, since the element added to the solid solution, mixed in the free state or contained in the particle surface does not contribute to the discharge capacity, the capacity per unit volume of the active material is lowered, and the electrolytic capacity is lowered. There is a problem that it is partially dissolved in the liquid and deposited on the negative electrode to cause a short circuit or the like. In view of these problems, the present invention aims to provide a nickel electrode which prevents generation of oxygen, which is a decomposition reaction of an electrolytic solution during charging, and has excellent charging efficiency at high temperatures.

[0004]

The present invention relates to an electrode plate using nickel hydroxide as an active material, which is provided in the pores (internal pores) of the nickel hydroxide particles in a corroded area with an alkaline aqueous solution. Zinc, cadmium, cobalt,
The nickel electrode for an alkaline storage battery is characterized by containing a metal element such as lead, copper, silver, ruthenium, indium or tungsten.

[0005]

[Working] From the measurement of the pore size distribution by the nitrogen adsorption method, the present inventors have found that the nickel hydroxide particles have an average radius of about 50.
It has been found that the porous body has pores of Å and has a pore volume (void volume inside particles) of about 10 to 30%, and most of the surface area of the particles is due to the internal pores. Then, it was found that the metal element in the corroded region (corrosion) in the alkaline aqueous solution was easily diffused and fixed in the pores. In particular, zinc, cadmium, cobalt, lead, copper,
When silver, ruthenium, indium, and tungsten were fixed in the pores of the nickel hydroxide particles, there was an action of nobly shifting the oxygen generation potential during charging, and it became possible to obtain a high oxygen overvoltage. Further, since these metal elements are present in the inner pores of the pores of the particles, there is an advantage that the capacity per unit volume of the active material does not decrease.

[0006]

EXAMPLES Examples of the present invention will be described below. Reference Example 1 The nickel hydroxide powder of Reference Example 1 was prepared by adding ammonium sulfate to an aqueous solution of nickel sulfate.
Stabilized as an ammine complex, and stirred vigorously while adding sodium hydroxide aqueous solution to adjust the pH value during the reaction to 11 to 11.
By controlling to 13, nickel hydroxide was deposited and grown. The nickel hydroxide particles obtained were spherical, and the internal pore volume and pore size distribution were measured by the nitrogen adsorption method. As a result, internal voids of about 0.03 ml / g (corresponding to about 10% of the total particle volume) ), And the average pore radius is 2
It was 0-40Å.

Reference Example 2 The nickel hydroxide powder of Reference Example 2 was produced by a known neutralization method. The obtained nickel hydroxide particles were amorphous particles having larger internal pores. The integrated pore volume curve and integrated pore surface area curve of the nickel hydroxide particles of Reference Examples 1 and 2 are shown in FIGS. 1 and 2. From these, it is understood that the nickel hydroxide particles are a porous body in which microcrystals are aggregated, and the surface area thereof is mostly due to the internal pores of the particles. The pore densities of Reference Example 1 and Reference Example 2 were 10% and 34%, respectively, and the true densities of nickel hydroxide were both 3.6 g / ml.

(Comparative Example) The nickel hydroxide powder of Reference Example 1 was mixed with a conductive agent and made into a paste with a CMC aqueous solution.
A nickel fiber porous body substrate was filled to prepare a paste type nickel electrode. The nickel electrode in this state was used as a comparative example.

(Example) Next, a nickel electrode was formed in a KOH electrolytic solution containing a metal element in a corrosion region (corrosion), such as zinc, cobalt, lead, ruthenium silver, indium or copper, in an alkaline aqueous solution. The nickel electrode of the present invention was obtained by immersing or electrochemically performing redox reduction to contain the metal elements in the internal pores of the nickel hydroxide particles.

Next, the cross sections of the electrodes of the comparative example and the example are shown by E.
As a result of PMA analysis, it was observed that the metal element was not distributed on the surface of the spherical nickel hydroxide particles or between the particles but was localized inside the particles. Further, these metal elements remained fixed in the internal pores without elution into the alkaline electrolyte even after repeated charging and discharging. Alternatively, the electrode of the present invention can be obtained by coexisting nickel hydroxide particles and a compound of the metal element and electrochemically oxidizing and reducing them. In addition, such diffusion or localization of nickel hydroxide particles into the pores was not observed in the case of a metal element which was not present in the corroded region in the alkaline aqueous solution.

FIG. 3 shows the charging characteristics of the nickel electrode of the present invention (example in which zinc is contained in the particles) and the electrode of the comparative example. The charge flow rate was 0.1 C and the ambient temperature was 20 ° C. In the product of the present invention (Example), the oxygen generation potential at the end of charging was significantly shifted. This shift of the oxygen generation potential to noble indicates an increase in oxygen overvoltage, which means improvement in charging efficiency at high temperature.

[0012]

As described above, according to the present invention, it is possible to provide a nickel electrode for an alkaline storage battery which is excellent in charging efficiency at high temperature without causing a decrease in capacity per unit volume of the active material. , Its industrial value is extremely large.

[Brief description of drawings]

FIG. 1 is a cumulative pore volume curve diagram of Reference Example 1 and Reference Example 2.

FIG. 2 is a cumulative surface area curve diagram of Reference Example 1 and Reference Example 2.

FIG. 3 is a graph of charging characteristics of Example and Comparative Example.

Front Page Continuation (72) Inventor Masahiko Oshiya 6-6 Josaimachi, Takatsuki City, Osaka Prefecture Yuasa Corporation

Claims (1)

[Claims] 1. An electrode plate using nickel hydroxide as an active material, wherein zinc, cadmium, cobalt, lead, copper, silver in a corrosive region in an alkaline aqueous solution is contained in pores of the nickel hydroxide particles. A nickel electrode for an alkaline storage battery, which contains a metal element such as ruthenium, indium or tungsten.