JPH05156322A - Production of hydrogen storage alloy and alkaline battery using the alloy - Google Patents

Abstract

PURPOSE:To provide an alkaline battery using a hydrogen storage alloy and excellent in charging and discharging life and discharge characteristics by improving the production process of the hydrogen storage alloy. CONSTITUTION:The molten hydrogen storage alloy 1 is blown by a compressed inert gas into an aq. alkaline soln. 7 and rapidly solidified to obtain the fine alloy powder having 1-100mum average grain diameter. An alkaline battery is formed from this fine alloy powder, and the durable alkaline battery excellent in discharge characteristics is provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a hydrogen storage alloy capable of electrochemically storing and releasing hydrogen, and an alkaline storage battery using the alloy powder as a negative electrode.

[0002]

2. Description of the Related Art Hydrogen storage alloys capable of absorbing and releasing a large amount of hydrogen have attracted attention as electrode materials having high energy density, and have been applied to alkaline storage batteries aiming for high capacity.

The hydrogen storage alloy is used as a negative electrode for an alkaline storage battery by making an alloy lump into a fine powder having an appropriate particle size and applying it as a paste onto a porous steel plate or filling a three-dimensional substrate such as foam metal.

In order to obtain this alloy fine powder, a method of pulverizing the alloy by repeating occlusion / release of hydrogen gas or mechanically crushing an alloy lump is generally used.

[0005]

However, in the pulverization method in which the hydrogen gas is repeatedly stored and released as described above, there is a risk that the alloy powder may ignite when some hydrogen remains in the pulverized alloy. Further, in the mechanical pulverization method, the particle size distribution of the pulverized powder becomes too wide, which may adversely affect the battery characteristics.

That is, when the active material powder having a diameter of 100 μm or more contains a large number of coarse particles, the surface area of the alloy is reduced and the battery voltage during discharge is reduced. On the contrary,
If a large number of fine particles of 1 μm or less are included, the surface area of the alloy becomes too large, and the corrosion resistance in the alkaline electrolyte decreases, resulting in a negative effect on the charge / discharge life characteristics of the battery.

The present invention solves such problems, and provides an alloy powder having a uniform particle size and stable in an alkaline electrolyte by a relatively simple method, and an alkaline storage battery using the same. The purpose is.

[0008]

In order to solve these problems, the present invention is directed to the production of an alloy in which a molten hydrogen-absorbing alloy is blown into an alkaline aqueous solution with a pressurized inert gas and rapidly solidified. The present invention provides an alkaline storage battery using the method and fine powder having an average particle diameter of 1 to 100 μm obtained by this production method.

[0009]

The present invention provides an alkaline storage battery which can efficiently obtain a hydrogen storage alloy powder by the above-described manufacturing method, and by using the powder, the battery voltage during discharge does not decrease and the life is long. Is possible.

That is, by supplying the molten hydrogen-absorbing alloy to an alkaline aqueous solution in an inert gas atmosphere and rapidly solidifying it, it is possible to quickly obtain an alloy powder having a uniform particle size. Therefore, 100 μm or more and 1 μm
As a result of the decrease in the ratio of the powders below, the battery using this powder for the negative electrode does not decrease the voltage during discharge and has a long life.

Further, by supplying the molten alloy to the alkaline aqueous solution, it is possible to remove the components which are easily dissolved in the alkali on the surface of the alloy from the alloy powder at the same time as the rapid solidification, so that the long life of the battery can be promoted.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below with reference to the drawings.

A hydrogen storage alloy powder that electrochemically stores and releases hydrogen as an active material was prepared by the following method.

Cerium about 40 wt%, lanthanum about 30 w
The atomic ratio of misch metal (hereinafter referred to as Mm) containing t% and neodymium of about 13 wt% as main components, nickel, cobalt, aluminum and manganese is 1: 3.5.
Weigh to be 5: 0.75: 0.3: 0.4.
Using the alloy powder manufacturing apparatus shown in FIG.
MmNi _3.55 Mn _0.4 Al _0.3 having a _5- type crystal structure
A hydrogen storage alloy powder of Co _0.75 was prepared.

In the alloy powder manufacturing apparatus of FIG. 1, the metal raw material charged into the apparatus is heated and melted by the heater 2 provided around the melting furnace 3 to form the molten alloy 1. When the high-pressure argon gas is supplied to the melting furnace 3 after the molten metal 1 is secured, the liquid surface of the molten alloy 1 is pressurized, and the molten metal 1 is sprayed from the tip of the pouring nozzle 4 provided in the lower portion of the melting furnace 3. It The sprayed molten metal is blown into the alkaline aqueous solution 7 in the molten metal reservoir 6 and rapidly solidified to produce the hydrogen storage alloy powder 8. Reference numeral 5 in the figure denotes an on-off valve that moves up and down to open and close the pouring nozzle 4.

In the above alloy powder production apparatus, the hydrogen storage alloy powders having different average particle diameters were prepared by changing the nozzle diameter of the pouring nozzle 4 and the supply amount of the high pressure argon gas as the pressure source.

Using the hydrogen storage alloy powder obtained as described above, three types of hydrogen storage alloy electrodes having a width of 39 mm, a length of 80 mm and a chargeable / dischargeable capacity of 1600 mAh were prepared according to the following formulation.

(Example 1) A hydrogen storage alloy powder having an average particle diameter of 20 μm prepared in the above-mentioned alloy powder manufacturing apparatus was used.
A polyvinyl alcohol (hereinafter referred to as PVA) aqueous solution is added to P
0.15 wt% of VA resin is mixed to form a paste. This was filled in a foamed nickel substrate having a porosity of 95%, and then pressed to cut it into the above size.

(Example 2) In the above alloy powder production apparatus, the hydrogen storage alloy powder having an average particle size of 20 μm obtained by cooling with an argon gas without pouring the molten metal into the alkaline aqueous solution in the molten metal reservoir 6 was added to PVA. The aqueous solution was mixed in a PVA resin amount of 0.15 wt% to form a paste. Then, this paste was filled in a foamed nickel substrate having a porosity of 95%, and then pressed to cut into the above size.

(Example 3) A hydrogen storage alloy ingot melted in a high frequency melting furnace and naturally cooled was averaged to a particle size of 2 with a crusher.
It is ground to 0 μm, and the PVA aqueous solution is mixed in 0.15 wt% as the PVA resin amount to form a paste. Then, this paste was filled in a foamed nickel substrate having a porosity of 95%, and then pressed to be cut into the above size.

The above three kinds of hydrogen storage alloy electrodes are used as a negative electrode.
Well-known metal foam nickel with a capacity of 1000 mAh
Sulfonated positive electrode and polypropylene non-woven fabric
Using a phonated polypropylene nonwoven fabric separator
A spiral electrode group is formed. Then, attach this electrode group to the metal case.
Insert into a space, then 7.1 cm KOH aqueous solution 2.2 cm
³After injecting liquid, seal it and seal it with AA (IEC standard R6) size
The prototype battery was manufactured.

Using this battery, a life test and a discharge test were conducted. In the life test, charging was carried out at a current value of 1 A for 1.5 hours in an atmosphere of 20 ° C., and then discharging was repeated at a current value of 1 A to a final voltage of 0.8 V. In the discharge test, charging was performed at a current value of 100 mA for 15 hours in an atmosphere of 20 ° C., and then discharging was performed at a current value of 3 A.

FIG. 2 shows the relationship between the number of charge / discharge cycles and the discharge capacity when a life test was conducted using the batteries of Examples 1 to 3. As is clear from FIG. 3, in Example 1, the discharge capacity was maintained at 900 mAh or more even after repeating the charge / discharge cycle of 500 times, which was a good result. But example 2,
In Example 3, the discharge capacity was about 60% of the initial capacity when the charge and discharge cycles were repeated 300 times and 50 times, respectively.

The improvement of the charge / discharge cycle life in Example 1 is that (1) the proportion of fine particles of 1 μm or less is reduced as compared with the usual mechanically crushed product by the method for producing the alloy powder of the present invention.

(2) Further, since the molten metal is put into an alkaline aqueous solution for rapid solidification treatment, a component easily dissolved in alkali on the surface of the alloy powder produced at the time of solidification is removed from the alloy powder. It is presumed that the corrosion resistance of the alloy in the alkaline electrolyte is improved for the following two reasons.

FIG. 3 shows the relationship between the alloy average particle size and the number of cycles until the discharge capacity reaches 60% of the initial capacity when the average particle size of the hydrogen storage alloy powder of the electrode of Example 1 is changed. .. As shown in FIG. 3, when the average particle diameter of the alloy powder was 1 μm or more, the discharge capacity was maintained at 60% or more of the initial capacity even after repeating 400 charge / discharge cycles, which was a good result. From this, the average particle diameter of the alloy is preferably 1 μm or more from the viewpoint of charge / discharge cycle life.

FIG. 4 shows the average particle size of the alloy powder when the average particle size of the hydrogen storage alloy powder of the electrode of Example 1 was changed, and 2
The relationship with the battery voltage (hereinafter referred to as the intermediate voltage) at the intermediate point of the discharge capacity when discharged to a final voltage of 0.8 V at a current value of 3 A at 0 ° C. is shown.

It can be seen from FIG. 4 that the intermediate voltage during discharge rises as the average particle size of the alloy powder becomes smaller. If the average particle size is 100 μm or less,
The intermediate voltage during 3 A discharge at 20 ° C. was 1.05 V or more, which was good. From this, from the viewpoint of discharge voltage, the average particle diameter of the alloy is preferably 100 μm or less.

Although the nickel-hydrogen storage battery has been described above as an example, it goes without saying that the same effect can be obtained in other alkaline storage batteries using a hydrogen storage alloy such as a manganese dioxide-hydrogen storage battery in the negative electrode.

[0030]

As described above, according to the present invention, the molten hydrogen storage alloy is rapidly solidified by being blown into an alkaline aqueous solution with a pressurized inert gas and having an average particle size of 1 to 100 μm.
By producing a fine powder of m and forming an alkaline storage battery using the fine powder, it is possible to provide an alkaline storage battery having a long life and excellent discharge characteristics.

[Brief description of drawings]

FIG. 1 is a schematic view showing an alloy powder manufacturing apparatus.

FIG. 2 is a diagram showing the relationship between the number of charge / discharge cycles and the discharge capacity.

FIG. 3 Alloy average particle size and discharge capacity are 60% of initial capacity
Diagram showing the relationship with the number of cycles until

Fig. 4 Average alloy particle size and 20 ° C, 0.8 at current value 3A
The figure which shows the relationship with the battery voltage in the middle point of the discharge capacity at the time of discharging to V.

[Explanation of symbols]

 1 molten metal 2 heater 3 melting furnace 4 pouring nozzle 5 pouring nozzle 4 opening / closing valve 6 molten metal reservoir 7 alkaline aqueous solution 8 hydrogen storage alloy powder

Claims (3)

[Claims] 1. A method for producing a hydrogen-absorbing alloy, which comprises pressurizing a molten hydrogen-absorbing alloy with an inert gas, blowing it into an alkaline aqueous solution, and rapidly solidifying it to obtain fine powder. 2. A positive electrode mainly composed of a metal oxide, a negative electrode mainly composed of a hydrogen storage alloy powder capable of electrochemically storing and releasing hydrogen as an active material, a separator, and an alkali. An alkaline storage battery comprising an electrolytic solution, wherein the hydrogen storage alloy powder obtained by the manufacturing method according to claim 1 is used for a negative electrode. 3. The hydrogen storage alloy powder has an average particle diameter of 1 to 10.
It is 0 micrometer, The alkaline storage battery of Claim 2 characterized by the above-mentioned.