JPH01267966A - Manufacturing method for sealed nickel-metal hydride storage batteries - Google Patents

Abstract

PURPOSE:To raise the activity in initial period and enhance the discharging characteristic by leaving at a temp. over the room temp. in the condition that negative electrode has occluded hydrogen. CONSTITUTION:MnNi3.55Mn0.4Al0.3Co0.75 is used to a hydrogen absorption alloy for negative electrode, and when left in an atmosphere over 30 deg.C in the condition that the negative electrode has occluded hydrogen over 10%, preferably 10-90% of the hydrogen occluding capacity of the alloy, active Ni metal of Co metal is liberated associate with oxidation of rare earth metal on the surface of the alloy of Mn-Ni-Mn-Al-Co. This active Ni or Co metal acts as catalyst in hydrogen occluding and emitting reactions. This promotes the discharging reaction of the negative electrode as battery.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an improvement in the manufacturing method of a sealed nickel-hydrogen storage battery using a hydrogen storage alloy for the negative electrode.

Conventional technology Nickel-hydrogen storage batteries that use a hydrogen-absorbing alloy as the negative electrode material, which stores and releases the active material hydrogen at high density, can be sealed, making them high-energy-density batteries that far exceed those of sealed cylindrical nickel-cadmium storage batteries. It is expected that

However, negative electrodes using hydrogen-absorbing alloys have significantly lower activity in the initial electrochemical reaction than cadmium negative electrodes, so their discharge capacity is low for several cycles after battery construction, and charging and discharging cycles are repeated for more than a dozen cycles. After that, it becomes possible to obtain sufficient discharge capacity. This tendency also shows that at low temperatures,
This is particularly noticeable when high rate discharge is performed. Therefore, in order to enable low-temperature, high-rate discharge even in the initial stage (second cycle) after battery construction, it is necessary to increase the initial activity of the hydrogen storage alloy negative electrode.

For this purpose, (a) prior to battery construction, a hydrogen storage alloy electrode is placed in a high-pressure hydrogen atmosphere to absorb and release hydrogen; 0)) electrolyte injection after battery construction;

Possible methods include a method in which the negative electrode absorbs and releases hydrogen in a high-pressure hydrogen atmosphere before sealing, and (0) a method in which the hydrogen storage alloy negative electrode is charged and discharged in an alkaline aqueous solution before being constructed.

Problems to be Solved by the Invention However, the methods (a) and (b) above require complicated hydrogen storage and release operations. Furthermore, when the activated negative electrode comes into contact with the atmosphere, it is oxidized and loses its activity.

To prevent this, it is necessary to perform the steps up to sealing under a hydrogen or inert gas atmosphere. In the case of (C), (
In addition to the same problems as a) and (b), it requires complicated steps such as charging and discharging in an alkaline aqueous solution and washing and drying the charged and discharged electrodes.

The present invention solves the above problems, and aims to provide a method for manufacturing a sealed nickel-metal hydride storage battery that is capable of high-rate discharge at low temperatures even in the initial stage (second cycle) after battery construction.

Means for Solving the Problems To solve this object, the present invention provides a sealed nickel
The method for manufacturing a hydrogen storage battery includes the step of sealing the battery and leaving the battery unsoldered for 6 days in an atmosphere at a temperature of 30 to 60°C above room temperature while the negative electrode occludes hydrogen.

Effect: This manufacturing method allows active Ni to be deposited on the surface of the hydrogen storage alloy.
The metal and Co metal are liberated, and this acts as a catalyst for the hydrogen storage-release reaction, thereby promoting the charging and discharging reaction of the negative electrode as a battery. Therefore, it is possible to obtain a sealed nickel-hydrogen storage battery that is capable of low-temperature, high-rate discharge from the initial stage (second cycle) after battery construction.

EXAMPLES The present invention will be explained below with reference to Examples. The hydrogen storage alloys used for the negative electrode are yknNi3.55Mno, 4Alo, 3COo, 75
was used. Mm (La:
Approximately 26% by weight, Ce: approximately 62% by weight, Nd
: about 18% by weight, Pr: about 5% by weight, etc.) and Ni,
Each sample of Mn, AI, and Co was placed in an arc melting furnace and 1
After creating a vacuum state to 0 to 10 Torr, arc discharge was performed in an argon gas atmosphere (reduced pressure state) to heat and melt. In order to homogenize the sample, it was heated at 1°C in vacuum at 8°C.
A heat treatment was performed for a period of time. The obtained alloy was coarsely ground, then made into a fine powder of 38 μm or less using a ball mill, and then mixed with a 1.5% by weight aqueous solution of polyvinyl alcohol to form a paste. This paste was filled into a foam metal type nickel substrate, and after drying, it was immersed in an aqueous potassium hydroxide solution with a specific gravity of 1.30 at 80° C. for 12 hours, and then washed with water.

After drying, pressurize and make the dimensions of AA size (39X80Xo, 5
m) to obtain a hydrogen storage alloy negative electrode. This negative electrode is combined with a known nickel oxide positive electrode, and the nominal capacity of the positive electrode capacity is 1. A sealed nickel-metal hydride storage battery of OOOmAh AA size was constructed.

This battery was heated at 0.1C until the hydrogen storage capacity of the negative electrode (relative to the hydrogen storage capacity of the hydrogen storage alloy) reached the value shown in Table 1.
After charging at mA, the batteries were left at each temperature for a predetermined number of days.

Table 1 After being left unused, the remaining capacity of the battery was discharged, and then as a second cycle, it was charged at 20°C and 0.1 CmA for 15 hours.
After being left at ℃ for 1 hour, discharge was performed at 30 mA. In addition, as a comparative example, battery
A discharge of 0 mA was performed. The discharge curve at this time is shown in FIG. Subsequently, the temperature was increased to 0. I CmA X 0.2℃mA after 15 hours of charging.

Discharge was performed until 1.ov. Assuming that the capacity at this time is 100, 1. The ratio to the capacity until Ov is reached is defined as the discharge capacity ratio. FIG. 2 shows the relationship between storage temperature and discharge capacity ratio. Furthermore, FIG. 3 shows the relationship between the standing period and the discharge capacity ratio.

As is clear from the discharge curve in FIG. 1, if the negative electrode is not left to stand, or if it is left to stand with the hydrogen storage capacity of the negative electrode being less than 10%, no discharge occurs at 30 mA at 0°C. Further, when the storage temperature is 20° C., discharge occurs, but the discharge voltage is low and the discharge capacity until reaching 1.0 ov is extremely small.

However, as shown in FIG. 2, by leaving the negative electrode in an atmosphere of 30°C or higher with hydrogen stored at 10% or more, preferably 10 to 90% of the hydrogen storage capacity of the hydrogen storage alloy, 9. In the early stage after battery construction (second cycle), at a lower temperature,
High rate discharge became possible.

This is caused by leaving the battery at a temperature above room temperature.
This is because active Ni metal and Co metal are liberated on the surface of the Mm-Ni-Mn-AI-Co hydrogen storage alloy as the rare earth metal oxidizes. Since these active Ni and Co metals act as a catalyst for the hydrogen storage/release reaction, the discharge reaction of the negative electrode is promoted as a battery. These active metal atoms are likely to be generated when the hydrogen storage alloy is left at high temperature while storing hydrogen. However, if left at extremely high temperatures, there is a risk of deterioration of other components of the battery, such as the separator and the positive electrode.
SoC is desirable. Further, from FIG. 3, it is clear that the effect appears when the period of standing is longer than % days, but as long-term standing causes the manufacturing process to become longer, it is appropriate that the period of standing is between % and 5 days.

In the example, only the case where the first cycle of charging was performed until the predetermined hydrogen storage amount was reached was described, but after fully charging in the first cycle, the battery was discharged to the predetermined hydrogen storage amount and then left. Good too. It also has an effect on the discharge characteristics after several cycles of charging and discharging.

Effects of the Invention As described above, according to the present invention, by leaving a sealed nickel-metal hydride storage battery at a temperature above room temperature with the negative electrode occluding hydrogen, a battery with high initial activity and excellent discharge characteristics can be produced. This has the effect of making it possible to provide a sealed nickel-metal hydride storage battery.

[Brief explanation of the drawing]

Figure 1 shows the 30°C temperature at 0°C after standing (second cycle).
Figure 2 is a diagram showing the discharge curve during mA discharge, Figure 2 is a diagram showing the relationship between battery storage temperature and discharge capacity ratio at 30mA discharge at 0°C after storage, and Figure 3 is the relationship between battery storage temperature and discharge capacity ratio at 30mA discharge. O after
It is a figure which shows the relationship with the discharge capacity ratio of 30 mA discharge at °C. Name of agent: Patent attorney Toshio Nakao and 1 other person - Stomach Mi Figure 2 Cunning! Meng Sha (・C) Figure 3 Membrane 1 period (B)

Claims (2)

[Claims] (1) Sealed type consisting of a negative electrode mainly composed of a hydrogen storage alloy that can electrochemically absorb and release hydrogen as an active material, a positive electrode using nickel oxide as an active material, a separator, and an electrolyte. A method for manufacturing a sealed nickel-hydrogen storage battery, which comprises the step of leaving the negative electrode in an atmosphere of 30 to 60° C. for half a day to five days after sealing, with the negative electrode occluding hydrogen. (2) The method for manufacturing a sealed nickel-hydrogen storage battery according to claim 1, wherein the hydrogen storage capacity of the negative electrode is 10% or more of the hydrogen storage capacity of the hydrogen storage alloy.