JPS6139461A - Manufacture of enclosed alkaline battery - Google Patents

Abstract

PURPOSE:To make a part of the negative pole consisting of a hydrogen occluded alloy chargeable so effectively during a manufacturing process, by letting the negative pole inside a car occlude hydrogen under a hydrogen ambience, while injecting an electrolyte into the case under the hydrogen ambience, and successively sealing a mouth of the cell case. CONSTITUTION:A case 9 in which an elementary cell is inset is put into a pressure vessel 1 and, after exhaust takes place with a vacuum pump, hydrogen gas is led into this vessel 1. Successively, hydrogen is drained out of the vessel 1 and, after hydrogen pressure inside the vessel 1 is made to drop to the extent of atmospheric pressure, an electrolyte is injected in the cell case 9 as much as necessary. Next, with an inert gas led into the pressure vessel 1, the cell case 9 is taken out after the hydrogen gas entirely exhausted, sealing it at once. The amount of hydrogen discharged out of a hydrogen occluded alloy cathode during whiles from an intake of the inert gas to sealing is an negligible as small because the cathode is wetted with the electrolyte, thus a battery in a sound condition is manufacturable.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a method for manufacturing a sealed alkaline storage battery using a hydrogen storage alloy as a negative electrode.

[Technical background of the invention and its problems]

Alkaline storage batteries that use hydrogen for the negative electrode active material and metal oxide for the positive electrode are called metal oxide-hydrogen storage batteries, and have recently attracted attention as high energy density batteries. However, such batteries require the use of high pressure hydrogen gas. For this reason, it has been considered to use an electrode made of a hydrogen-absorbing alloy as the negative electrode, and several studies have recently begun to appear.

The reaction of the hydrogen storage alloy with hydrogen can be considered as shown in the following formula [1].

M + H2: M (Hatm)2 [1
] Here, M is a hydrogen storage alloy, and M (Hatm)2 indicates that two hydrogen atoms are present in M as atomic hydrogen. When this hydrogen storage alloy is used as an electrode in an alkaline aqueous solution, it is thought that the reaction of the following formula [2] occurs.

That is, since gaseous hydrogen is not involved here, by using a hydrogen storage alloy for the negative electrode, it is basically possible to fabricate a battery that does not require consideration of battery internal pressure. However, M (Hatm)2 obtained from the above formula [2]
is in an equilibrium relationship with gaseous hydrogen as shown in equation [1] above.

Therefore, in reality, it is necessary to use a hydrogen storage alloy with a low equilibrium hydrogen pressure for the negative electrode.

By the way, when assembling a sealed alkaline storage battery,
Normally, the capacitance of the positive and negative electrodes inserted into the device is larger for the negative electrode than for the positive electrode. At this time, it is necessary that a part of the excess capacity of the negative electrode be in a charged state, and the remaining part be in an uncharged state. Such a state is
Only when a battery is in a healthy condition can it operate normally and have a long cycle life.

In order to ensure the above-mentioned healthy condition, ■ Before assembling the negative electrode to be used into a unit cell (for example, in the chemical process)
Oxygen is generated from the positive electrode by leaving a part of the battery in a charged state, or by inserting the battery into the battery case, injecting electrolyte into it, and then overcharging the battery without sealing it. It is conceivable to carry out an operation in which the negative electrode is charged more than the positive electrode by the amount that has escaped to the outside.

However, when trying to apply the above method to a negative electrode of a hydrogen storage alloy, the following problems arise. The method of ■ above,
In other words, it is possible to charge the battery in advance through a chemical formation process, but the hydrogen in the hydrogen storage alloy of the negative electrode is released by the reverse reaction of formula [1] above before it is assembled into a unit cell and inserted into the battery case. As a result, it is not possible to assemble a storage battery in a healthy condition. In addition, in the method (2) above, since the oxygen generated from the positive electrode during overcharging reacts extremely quickly with hydrogen in the negative electrode of the hydrogen storage alloy, only a small amount is released to the outside.

As a result, even method (2) cannot bring the device into a healthy state.

[Purpose of the invention]

The present invention aims to provide a method for manufacturing a sealed alkaline storage battery that can effectively charge a portion of the negative electrode made of a hydrogen storage alloy during the manufacturing process.

[Summary of the invention]

In the present invention, a negative electrode and a positive electrode made of a hydrogen storage alloy are spirally wound through a separator to form a unit cell, and after inserting this into a battery case, the hydrogen storage alloy inside the case is removed under a hydrogen atmosphere. The battery case is characterized in that hydrogen is occluded in the negative electrode, an electrolytic solution is injected into the case under the same hydrogen atmosphere, and the battery case is subsequently sealed.

According to the method of the present invention, the hydrogen storage alloy negative electrode stores hydrogen within the battery case, and the electrolyte is immediately injected under a hydrogen atmosphere, so that an electrochemical state of charge is achieved, and the battery case is then removed. Since the cap is sealed, no hydrogen gas is released during these processes, allowing the battery to be manufactured in a healthy state.

Specifically, after first inserting the unit battery into the battery case,
This case is placed in a pressure-resistant container, and the inside of the container is maintained at approximately 10-3 to 10-5 torr by exhaustion using a vacuum pump. Subsequently, exhaustion is stopped and hydrogen gas is introduced into the container. The pressure at this time is changed depending on the type and history of the hydrogen storage alloy used for the electrode and the amount of hydrogen to be stored (gauge pressure 40~
hg/In2). The same applies to the time of exposure to hydrogen atmosphere. -Subsequently, after removing hydrogen from the container and lowering the hydrogen pressure in the container to atmospheric pressure, the required amount of electrolyte is injected into the battery case. Next, while introducing an inert gas into the pressure container, after completely discharging the hydrogen gas, take out the battery case and seal it immediately. Since the negative electrode is already wet with the electrolyte, the amount of hydrogen released is small, making it possible to manufacture a battery in a healthy bottle state.

[Embodiments of the invention]

Next, the present invention is applied to a positive electrode of nickel oxide (Ni00H),
L aN with equilibrium plateau pressure 0.4 atm at 25°C
l AA ffi Nip2m with a negative electrode made of a hydrogen storage alloy of 4,7Atc3! Pond (rated 500 mAh
) An example in which an OR-built IC is applied will be explained.

First, LaN147At is made into a powder with a particle size of 20 μm or less, and this? Litetrafluoroethylene (PT)
A suspension of FE) was added so that its solid content was 4 parts of the total, and then mixed and kneaded. Next, this mixed material was rolled into a sheet-like material with a thickness of about 0.5 degrees, and then
Nickel mesh (wire diameter 0.125I+oI!1) from one side
40 mesh,) fully abutted, crimped and 80 pieces x 40. X
A negative electrode of 5 mm and 5 mm was prepared, and a lead wire was attached to the nickel mesh body.

Although this negative electrode has a theoretical capacity of about 1000 mAh, it is not charged at all at this point. Next, 2.ke/l/ is in a discharge state with a theoretical capacity of 600 mAh.
A pole (dimensions 70. Subsequently, this unit cell was inserted into a metal battery case, and the negative electrode lead was connected to the battery case, and the positive electrode lead was connected to the positive electrode terminal of the sealing plate, respectively, by resistance connection.

Next, the battery case was placed in a pressure-resistant container of a processing apparatus shown in FIG. This processing apparatus has a pressure-resistant container 1, which includes an exhaust port 2 connected to a rotary pump (not shown), an exhaust port 3 for gas inside the container 1, a hydrogen gas inlet 4, and an inert gas inlet 4. An inlet 5 and a pressure gauge 6 are provided. Also, at the upper center of the container 1, there is a silicone rubber &7. ! :, a stop cap 8 for the Fl stopper 7 is provided.

Note that 9 is a battery case. After the battery case 9 was placed in the pressure container 1, the rotary pump was operated to reduce the pressure in the container 1 to 10-'torr, and this was maintained for 30 minutes. Subsequently, hydrogen gas was introduced into the container 1 through the inlet 4, the pressure was set to 20ψj2, and the container was left for 30 minutes to cause the hydrogen storage alloy negative electrode in the battery case 9 to store hydrogen. Subsequently, hydrogen gas is released from the discharge port 3 and the internal pressure (gauge pressure) measured by the pressure gauge 6 is set to Okg/crn2, and then the stop cap 8 is removed and the microsyringe is inserted into the silicone rubber stopper 7, and the electrolyte is removed. An 8 M-KOH aqueous solution was injected into the battery case 9 of the pressure container 1 . After that, inert gas is introduced into the container 1 from the inlet 5, and when the inside of the container 1 is completely replaced with the inert gas (about 10 minutes), the container 1 is
The battery case 9 was taken out and sealed immediately to complete battery assembly.

Therefore, the electrode capacity charged in the hydrogen storage alloy negative electrode of the obtained battery in the above process was investigated.

In this test, before the sealing process, the unit cell was removed from the battery case and placed in a beaker filled with 8M-KOH aqueous solution.
Discharge was performed using a combination of a separately prepared charged nickel electrode and a hydrogen storage alloy negative electrode. The result is 280mAh
Met. This means that after battery assembly is complete, the hydrogen storage alloy negative electrode has a total capacity of 280 mAh out of a total capacity of Hk 1000 mAh.
This means that Ah is being charged.

Further, when the discharge capacity of the battery of this example was examined in a charge/discharge cycle test, the characteristic diagram shown in FIG. 2 was obtained. In addition, A in FIG. 2 is the characteristic line of this example, and B is the characteristic line of the hydrogen storage alloy negative electrode charged to 100% in the chemical formation process, followed by the water washing process, stem drying process, winding process, battery case insertion process, and liquid injection process. , Characteristic curve of the battery of Comparative Example 1 assembled through the sealing process (all the above processes were performed in Ar gas); This is a characteristic line of a battery of Comparative Example 2 assembled by a battery case insertion process, a liquid injection process, an overcharging process of charging to 200% of the battery rating (1000mAh), and a sealing process. However, in Comparative Examples 1 and 2, the amount of extra charge in the negative electrode relative to the positive electrode after battery assembly was completed was 5.
mAh, 25 mAh.

As is clear from FIG. 2, the capacity of the batteries of Comparative Examples 1' and 2 (characteristic lines B and C) decreases after about 30 and 70 cycles, respectively, whereas the battery of this example (characteristic line A ), no decrease in capacity was observed even after 200 cycles. This is because the amount of excess charge of the hydrogen storage alloy negative electrode in the battery of this example was a sufficient 280 mAh, whereas the amount of excess charge in the batteries of Comparative Examples 1 and 2 was almost negligible.

〔Effect of the invention〕

As described in detail above, according to the present invention, it is possible to reliably carry out the necessary overcharging of the hydrogen storage alloy negative electrode, and to provide a method for manufacturing a sealed alkaline storage battery with good cycle life.

[Brief explanation of the drawing]

Figure 1 shows hydrogen storage in the negative electrode in the battery production of the present invention.
FIG. 2 is a schematic diagram of a processing apparatus used in the electrolyte injection process, and a characteristic diagram showing changes in discharge capacity in a charge/discharge cycle test of batteries of the present example and comparative example 1.2. 1...Pressure vessel, 2...Exhaust port, 3...Discharge port,
6...Pressure gauge, 7...Silicone rubber stopper, 9...Battery case. Applicant's agent Patent attorney Takeshi Suzue 2. Figure 1 Figure 2.

Claims (1)

[Claims] After forming a unit cell by spirally winding a negative electrode and a positive electrode made of a hydrogen storage alloy with a separator interposed between them, the unit cell is housed in a battery case, and the hydrogen in the case is removed under a hydrogen atmosphere. Hydrogen is stored in a negative electrode made of a storage alloy,
A method for manufacturing a sealed alkaline storage battery, further comprising the steps of injecting an electrolyte into the case under the same hydrogen atmosphere, and sealing the case.