JPS5846827B2 - Manufacturing method of hydrogen storage electrode - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a battery negative electrode, a so-called hydrogen storage electrode, using an alloy that reversibly stores and releases hydrogen, which is used as a battery negative electrode active material.

This hydrogen storage electrode is used in storage batteries and fuel cells.

Conventionally, as this type of hydrogen storage electrode, there is a sintered electrode made by sintering a hydrogen storage alloy powder together with a conductive support in an inert air stream or in a vacuum at a temperature below the melting point of the alloy.

Since this electrode has a relatively low sintering strength due to the nature of the alloy, it has the disadvantage that repeated charging and discharging causes the particles to fall off due to the collapse of the bonds between the alloy particles, resulting in a decrease in discharge capacity.

This tendency is particularly remarkable in CaNi5-based alloys and LaNi5-based alloys.

In the present invention, metal powder that does not store hydrogen is mixed with alloy powder, which is an electrode active material that stores hydrogen, and is sintered to form a skeleton that does not participate in charge/discharge reactions caused by the metal. The present invention provides a long-life hydrogen storage electrode that does not come off.

The metal used here is preferably one that is resistant to electrolyte and can be sintered at the sintering temperature of the alloy, and is appropriately selected from transition metals and other conductive metals depending on the alloy used.

The alloy is CaNi5 alloy, LaNi5 alloy, Ni2T
Nickel is suitable for alloys containing nickel, such as i-based alloys.

Hereinafter, the present invention will be explained with reference to examples thereof.

Take commercially available calcium (purity 99.5% or higher) 122 and commercially available nickel (purity 99.5% or higher) 881, put them into an arc melting furnace, and heat the inside of the furnace to 10-5 to 10' Torr.
After reducing the pressure to 100%, argon was flowed, and then an arc was blown to heat and melt.

The sample was inverted several times to homogenize the alloy.

The alloy thus obtained is ground in an argon atmosphere, 10 ft of powder with a particle size of several microns to several tens of microns is taken, and 0.5 to 5.0 m of nickel powder is added to this. O? m and mixed well.

This mixture was made into a size of 25 x 25 mm and a thickness of 2.0 mm.
The electrode was filled in a foamed nickel metal and sintered at a temperature of 1000° C. for 2 hours in an argon gas flow to obtain an electrode.

An alkaline storage battery is constructed by using the above electrode as a negative electrode and a known nickel oxide electrode with a larger capacity as a positive electrode,
I did a charge/discharge test.

The charging/discharging current was 50 mA per mixture 11 of the negative electrode material alloy and nickel powder, the charging/discharging rate was 0.2 C, and the amount of charging electricity was equivalent to 130% of the negative electrode capacity.

The figure shows the relationship between the discharge capacity of the battery and the proportion of nickel powder added to the cathode alloy.

In the figure, the solid line represents the initial value, and the dotted line represents the value at the 50th cycle.

Note that the discharge capacity was expressed in terms of the amount per 11 of the mixture of the negative electrode alloy and nickel powder.

As is clear from the figure, as the amount of nickel added increases, the difference between the initial capacity of charge and discharge and that at the 50th cycle becomes smaller, and therefore, it can be seen that the deterioration of capacity due to charge and discharge cycles becomes smaller.

Furthermore, as the amount of nickel powder added increases, the supply value of the capacity decreases, so taking this point and the life into consideration, the amount of nickel added is preferably in the range of 5 to 30% by weight based on the alloy powder.

Hydrogen storage electrodes store hydrogen during charging and release hydrogen during discharge, so the electrode itself inevitably expands and contracts.
This results in a volume change of the sintered alloy particles.

If the bonding force between the particles is affected by the stress caused by the above-mentioned volume change, the particles will fall off.

In the electrode of the present invention, some of the sintered alloy particles are replaced with nickel particles, which are bonded to the alloy particles, and the nickel particles do not participate in the absorption and release of hydrogen.
It maintains a strong bond.

As described above, the present invention provides a hydrogen storage electrode with a long charge/discharge cycle life.

[Brief explanation of drawings]

The drawing shows the relationship between the discharge capacity of an alkaline storage battery that combines an electrode made of a sintered body of a mixture of alloy powder and nickel powder and a nickel oxide electrode, and the addition ratio of nickel powder to the alloy.

Claims (1)

[Scope of Claims] 1. A method for manufacturing a hydrogen storage electrode, which comprises sintering a mixture of an alloy powder that stores hydrogen and a metal storage powder that does not store hydrogen to form a sintered porous body. 2. The method for manufacturing a hydrogen storage electrode according to claim 1, wherein the alloy is an alloy containing nickel, and the metal is nickel. 3. The method for manufacturing a hydrogen storage electrode according to claim 1 or 2, wherein the mixing ratio of the metal to the alloy is 5 to 30% by weight.