JPH07114938A - Manufacture of sealed type metal hydride storage battery - Google Patents

Abstract

PURPOSE:To reduce electric charging/discharging cycles required for activation by discharging, outside of a battery, oxygen gas to be generated after a positive electrode is fully charged in the battery provided with a negative electrode made of a hydrogen storage alloy and the positive electrode having a chargeable capacity smaller than that of the negative electrode. CONSTITUTION:A sealed type metal hydride storage battery is provided with a metal case 1, a metal cover 2, a positive electrode terminal 3, and a negative electrode terminal 4 and a metal pipe 5 provided in the metal cover 2, for injecting an electrolyte. A resin tube 6 is connected to the metal pipe 5, to be led into water 7. Oxygen gas 10 to be generated inside a battery 8 is collected into a cylinder filled with and erected inside the water 7. A predetermined quantity of the oxygen gas 10 is discharged outside of the battery, thus restraining oxygen gas consumption in a negative electrode so as to proceed electric charging of the negative electrode by that quantity. Consequently, it is possible to increase an electrically dischargeable capacity of the negative electrode.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a sealed metal hydride storage battery using a hydrogen storage alloy for a negative electrode.

[0002]

2. Description of the Related Art Nickel-cadmium storage batteries have been often used as rechargeable sealed batteries.
In recent years, as a battery having a higher energy density than this nickel-cadmium storage battery and capable of increasing the battery capacity, a metal hydride storage battery using a hydrogen storage alloy for a negative electrode has come to be used.

In this sealed type metal hydride storage battery, as described in Japanese Patent Application Laid-Open No. 53-111439, usually, when the positive electrode is sufficiently discharged, a dischargeable charging portion remains on the negative electrode. With this configuration, the negative electrode absorbs hydrogen generated in the positive electrode during overdischarge, and
When the positive electrode is sufficiently charged, the negative electrode has a structure in which an uncharged portion remains, so that the negative electrode consumes oxygen generated from the positive electrode during overcharge.

By the way, in this metal hydride storage battery, since the hydrogen storage alloy used for the negative electrode is inactive at the time of battery construction, it is almost a normal battery by one charge / discharge after the battery is constructed like a nickel-cadmium storage battery. You cannot get the capacity. Therefore, it is necessary to charge and discharge the battery for several cycles to more than ten cycles until the predetermined capacity is obtained, thereby activating the battery. Therefore, a lot of time is spent for this activation process, and a large space for arranging equipment for this activation is required.

In order to reduce the number of activation treatments due to charge and discharge after the battery is constructed, in JP-A-1-102861, hydrogen is stored in a hydrogen storage alloy at least once in hydrogen gas before injecting an electrolyte. It has been proposed to occlude and release. However, this method requires a pressure resistant container and a large-scale device for introducing and discharging hydrogen gas in order to store and release hydrogen gas in the hydrogen storage alloy of the negative electrode,
The work is also complicated, and the activation process cannot be sufficiently simplified.

[0006]

DISCLOSURE OF THE INVENTION The present invention is intended to reduce the number of times of charge and discharge for activation performed after the above-mentioned metal hydride storage battery is constructed by adding relatively simple operations and steps. It is a thing.

[0007]

A method for manufacturing a sealed metal hydride storage battery according to the present invention comprises a negative electrode using a hydrogen storage alloy and a positive electrode having a smaller chargeable capacity than the negative electrode, housed in a battery container. By injecting the electrolytic solution and then overcharging, a gas is generated inside the battery and a predetermined amount of this gas is released to the outside of the battery.

[0008]

In the sealed metal hydride storage battery, the reason why the predetermined battery capacity cannot be easily obtained by only the initial few cycles in the charge / discharge cycle for activation after injecting the electrolytic solution is the negative electrode. This is because the hydrogen stored in the hydrogen storage alloy of the negative electrode is not 100% released during discharge at the first charge after the battery is constructed. Therefore, if the amount of hydrogen stored in the hydrogen storage alloy can be increased in the initial charge, the amount of hydrogen that can be released in the subsequent discharge can be relatively increased and the discharge capacity can be increased.

By the way, in the sealed metal hydride storage battery, the chargeable capacity of the positive electrode is designed to be smaller than the chargeable capacity of the negative electrode. For this reason, after the positive electrode is fully charged by charging, the oxygen gas generated from the positive electrode by subsequent charging is returned to water by the hydrogen stored in the negative electrode and consumed in the battery. That is, after the positive electrode is fully charged, hydrogen is stored in the negative electrode by the amount of electricity spent for oxygen gas generation in the positive electrode, but hydrogen stored in the negative electrode corresponding to the amount of hydrogen is Since the oxygen gas generated from the positive electrode is consumed and does not remain stored in the alloy in a stored state, the hydrogen storage amount in the negative electrode does not substantially increase thereafter. Therefore, at the time of initial charging after the battery is configured, even if the battery is simply overcharged, the amount of hydrogen stored in the hydrogen storage alloy of the negative electrode cannot be increased, and thus the discharge capacity of the negative electrode cannot be increased.

In the present invention, at the time of charging after the battery is constructed, a predetermined amount of oxygen gas generated from the positive electrode after the positive electrode is fully charged is released to the outside of the battery,
It is possible to suppress the oxygen gas consumption in the above-mentioned negative electrode and allow the negative electrode to be charged correspondingly. As a result, the dischargeable capacity of the negative electrode can be increased and the number of charge / discharge cycles required for activation can be reduced.

The dischargeable capacity of the negative electrode obtained during the first charge / discharge after the battery is constructed depends on the composition of the hydrogen storage alloy, the manufacturing method, and various pretreatments. It is necessary to set the amount of oxygen gas released to the.

[0012]

EXAMPLES The present invention will now be described with reference to examples. As raw metal of the hydrogen storage alloy used in Example 1 a negative electrode, a commercially available misch metal (Mm, a mixture of rare earth elements) and a nickel, cobalt and aluminum and manganese, the hydrogen storage alloy consisting of MmNi _3.2 CoAl _0.2 Mn _0.6 A powder was made. A paste was prepared by mixing a paste and pure water with this alloy, an iron plate was nickel-plated, and the paste was applied to a punched current collector plate and dried to prepare a negative electrode plate.

The 15 negative electrode plates thus produced and the 14 sintered nickel positive electrode plates were alternately laminated with a nylon non-woven fabric separator interposed therebetween, and then the positive and negative electrode ends arranged on the metal lid. A positive electrode plate and a negative electrode plate were respectively welded to the child, housed in a metal case, and then the metal case and a metal lid were welded to assemble a prismatic battery A having a nominal capacity of 20 Ah. A perspective view of this battery is shown in FIG. 1 in FIG.
Is a metal case, 2 is a metal lid, 3 is a positive electrode terminal, 4 is a negative electrode terminal, and 5 is a metal tube for injecting an electrolytic solution provided on the metal lid 2.

After injecting an electrolytic solution containing potassium hydroxide as a main component from the metal tube 5 of the battery A, the battery was charged at a current of 2A. When charging, as shown in FIG.
Connect the resin tube 6 to the
The gas 10 generated in the battery 8 was collected in a cylinder 9 that was filled with water 7 and was stood in the water 7.

Gas started to be generated from the battery 10 hours after the start of charging, and the charging was stopped when about 1.4 liters of gas could be collected. After that, the battery was taken out of the water, the metal tube 5 of the battery 7 was immediately sealed, and the inside of the battery was sealed. Then, the battery was discharged by connecting a resistance of 0.3Ω, and the discharge was stopped when the battery voltage became 1V.

The battery of the present invention which had been subjected to the above treatment, and the comparative battery which had not been subjected to any treatment after injection of the electrolytic solution in the above-mentioned Examples were each charged with a current of 2 A for 16 hours in a temperature atmosphere of 20 ° C. The battery capacity was measured by discharging the battery at a current of 10 A and repeating charging / discharging 7 cycles under the cycle condition of stopping the discharging when the battery voltage became 1V.
The result is shown in FIG. As is clear from FIG. 3, the battery of the present invention, which has been subjected to the above-mentioned treatment, has been
It can be seen that the capacity exceeding Ah is obtained, and the charge / discharge cycle until the predetermined battery capacity is obtained can be greatly shortened.

Next, each of the batteries whose battery capacity has been measured is charged / discharged under the same cycle condition in a temperature atmosphere of 20 ° C., and further charged / discharged under the same cycle condition in a temperature atmosphere of −5 ° C. The discharge capacities were measured, and Table 1 shows the discharge capacities of the battery of the present invention and the comparative battery in each temperature atmosphere. Further, in the parentheses in the table, the discharge capacity value at 20 ° C. of each battery is 100%, and the discharge capacity at −5 ° C. is shown in%.

[0018]

[Table 1] It can be seen that the battery of the present invention suppresses the decrease in discharge capacity during low temperature charge / discharge as compared with the comparative battery.

Example 2 A negative electrode plate having a larger area than that of Example 1 was prepared, and 17 negative electrodes and 16 sintered nickel positive electrode plates were used in the same manner as the battery A in Example 1, A prismatic battery having a nominal capacity of 35 Ah was assembled.

After injecting an electrolytic solution containing potassium hydroxide as a main component from a metal tube into the battery as in Example 1, the battery was cooled with water at 5 ° C. or lower as shown in FIG. Charging was performed at a current of 3.5A. In FIG. 3, 11
Is a battery, immersed in the cooling water 13 in the cooling tank 12,
A pressure gauge 14 and a valve 15 are connected to the liquid injection pipe of the battery 11, and the valve 15 is always closed. The temperature of the cooling water 13 is kept low by circulating it to the cooling device 16. The reason why charging is performed at a low temperature is to reduce the oxygen gas absorption capacity of the negative electrode with respect to the oxygen gas generated in the positive electrode.

At the time when 10 hours had elapsed after the start of charging, the charging current was increased to 10 A in order to accelerate the generation of oxygen gas from the positive electrode, and then the charging was continued and the pressure gauge was set to 4
When it reaches kg / cm ² (absolute pressure 5 kg / cm ² ),
Open the valve to release the gas inside the battery to the outside of the battery, close the valve when the pressure gauge drops to 0 kg / cm ² (absolute pressure 1 kg / cm ² ), repeat this operation 10 times, and stop charging. did. As a result of calculation from the space volume inside the battery that was measured in advance, 0.2 liters of gas was released in one operation, and a total of 2 liters of gas was released to the outside of the battery by the above operation. It has been done.

After the charging was stopped, the battery was taken out of the cooling water, the pressure gauge and the valve were removed, the metal tube of the battery was immediately sealed, and the inside of the battery was sealed. Then, the battery was discharged by connecting a resistance of 0.3Ω, and the discharge was stopped when the battery voltage became 1V.

The battery of the present invention which was subjected to the above treatment and the comparative battery which was not subjected to any treatment after injection of the electrolytic solution in Example 2 were subjected to an atmosphere of 20.degree.
After charging for 16 hours with a current of A, discharging was performed with a current of 17.5 A, and charging / discharging was repeated under cycle conditions in which discharging was stopped when the battery voltage reached 1 V, and the battery capacity was measured. The result is shown in FIG. As is clear from FIG.
The battery of the present invention that has been subjected to the above treatment, from the initial charge and discharge,
A capacity of more than 35 Ah was obtained, and it can be seen that the charge / discharge cycle until a predetermined battery capacity is obtained can be greatly shortened, as in the case of Example 1.

[0024]

As described above, the method for manufacturing a sealed metal hydride storage battery according to the present invention releases oxygen gas generated in the battery to the outside of the battery by a predetermined amount, thereby generating oxygen gas at the positive electrode during overcharge. However, by suppressing absorption by the negative electrode, the amount of charge of the negative electrode can be increased and the initial battery capacity can be increased. Also, with this,
It is possible to reduce the number of times of charge and discharge required for activation of the battery, and further it is possible to suppress a decrease in discharge capacity even at low temperature.

[Brief description of drawings]

FIG. 1 is a perspective view of a battery of the present invention.

FIG. 2 is a schematic diagram of a processing apparatus of the present invention.

FIG. 3 is a cycle characteristic diagram of the battery of the present invention and a comparative battery.

FIG. 4 is a schematic view of a processing apparatus according to another embodiment of the present invention.

FIG. 5 is a cycle characteristic diagram of the battery of the present invention and the comparative battery.

[Explanation of symbols]

 6 Resin Tube 7 Water 8, 11 Battery 9 Cylinder 10 Gas 12 Cooling Tank 13 Cooling Water 14 Pressure Gauge 15 Valve 16 Cooling Device

Claims (1)

[Claims] 1. A negative electrode using a hydrogen storage alloy and a positive electrode having a chargeable capacity smaller than that of the negative electrode are housed in a battery container, and after injecting an electrolytic solution, overcharging is performed.
A method for producing a sealed metal hydride storage battery, which comprises generating a gas inside the battery and discharging the gas to the outside of the battery by a predetermined amount.