JPS6119066A - Manufacture of battery - Google Patents

Abstract

PURPOSE:To obtain a primary battery having high reliability, good performance, and low environmental problem by assembling a hydrogen absorption alloy which absorption and desorption of hydrogen were performed at least once before assembling in a battery. CONSTITUTION:A hydrogen absorption alloy is crushed in an atmosphere of argon in powder having a particle size of 10-100mum. About 1wt% fluorine resin having a particle size of 1mum or less is added to the hydrogen absorption alloy and stirred to give water repellent property to the alloy. The alloy powder is degassed under vacuum at about 200 deg.C, and hydrogen is absorbed into the alloy to nearly saturation at a pressure of 30atm. at room temperature, then hydrogen is completely removed by vacuum. The alloy which absorption and desorption of hydrogen were performed at least once is assembled in a battery. Thereby, a primary battery having high reliability, good performance, and low environmental problem is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is a battery that uses zinc as the main active material of the negative electrode and an aqueous alkaline solution or an aqueous solution of a neutral salt as the electrolyte. The present invention relates to a method for manufacturing a battery 2 containing a built-in hydrogen storage alloy that prevents an increase in battery internal pressure.

Structure of the conventional example and its problems In order to suppress the corrosion reaction caused by the electrolyte of the zinc negative electrode of this type of battery, and to suppress the self-depletion of zinc and the generation of hydrogen gas during storage of the battery, zinc is added at a weight ratio of 6 to 10. Currently, mercury is added to form an amalgam and used as a negative electrode.
This method has been adopted as a general method, and this prevents the internal pressure of the battery from increasing due to storage, ensures leakage resistance, and prevents battery expansion.
It is popular as a practical battery that does not explode and has little performance deterioration.

In recent years, social needs for lower pollution have increased, and research and development is being conducted to reduce the amount of mercury used and to secure the above practical performance without using mercury. Although it is possible to some extent, the current situation is that there is no means that can provide an essential solution. For example, a technology is being considered that could reduce mercury to about 1 to 3 tres by using a corrosion-resistant zinc alloy made by adding lead, indium, gallium, etc. to zinc.
− It is considered extremely difficult to ensure sufficient corrosion resistance for zinc.

On the other hand, as a conventional proposal, a method has been proposed in which the hydrogen gas generated within the battery is absorbed and fixed by a hydrogen storage alloy built into the battery to prevent the internal pressure of the battery from rising. Because it is difficult to absorb hydrogen, a large amount of hydrogen storage alloy is required, sacrificing the internal volume of the battery and reducing capacity, and it is difficult to prevent leakage, expansion, and deterioration of storage performance due to insufficient storage capacity. It was difficult.

Purpose of the Invention The present invention provides a method for preventing an increase in battery internal pressure by storing hydrogen gas generated within a battery using a hydrogen storage alloy, which achieves high reliability and improved performance by increasing the hydrogen storage efficiency of the hydrogen storage alloy. The aim is to obtain an excellent low-pollution primary battery.

Structure of the Invention The present invention provides a battery that uses zinc as the main active material of the negative electrode and an alkaline aqueous solution containing caustic potash, caustic soda, etc. as the main component, or an aqueous solution of a neutral salt such as ammonium chloride or zinc chloride as the electrolyte. A process for storing and releasing hydrogen in advance before incorporating the hydrogen storage alloy into the battery, which is related to the manufacturing method of a primary battery that incorporates a hydrogen storage alloy in order to store hydrogen gas generated inside the battery and prevent an increase in battery internal pressure. The hydrogen storage alloy is incorporated into the battery in a hydrogen-releasing state by providing at least one cycle of It is handled in a vacuum or reduced pressure atmosphere.

First, the reason why the scope of application of the present invention is limited to primary batteries is as follows.
In the case of secondary batteries, the amount of hydrogen gas generated and accumulated during several tens to hundreds of charging and discharging cycles can be extremely large. Since the capacity is insufficient, it is considered impossible to obtain a highly reliable battery.From this point of view, in the case of negative batteries, the amount of gas generated is relatively small, so the hydrogen storage capacity and its reliability can be improved. By doing so, we believe that it is possible to absorb the generated hydrogen gas within the battery and prevent the increase in battery internal pressure.5 In particular, it is possible to reduce the amount of mercury contained in the zinc negative electrode or to suppress it when mercury is not used. This was achieved with the main focus on obtaining a low-pollution battery with excellent practical performance by occluding hydrogen gas that is generated in the battery without increasing the internal pressure of the battery.

Conventionally, in the process of incorporating a hydrogen storage alloy into a battery, metals are first melted and alloyed in a melting furnace in an argon atmosphere in a predetermined composition.
Powdered alloys pulverized to about 0 μm are used as they are, pressure-molded, or filled into porous metal bodies, and if necessary, water-repellent treatment is applied, and these are generally used as breathable materials. It is wrapped in plastic and stored in the empty compartment of the battery.

However, in the conventional method described above, the storage capacity of the hydrogen storage alloy is at best several tens of percent lower than the level expected from the original properties of this material, and furthermore, there are large variations in the storage amount and storage rate. In order to improve reliability, it is necessary to design based on the characteristic value at the lower limit of variation.
In order to incorporate a large amount of hydrogen storage alloy, it becomes necessary to sacrifice battery capacity6-7.To avoid this, reducing the amount of hydrogen storage alloy stored will improve the reliability of the battery's leakage resistance and storage performance. As a result, it was difficult to obtain a battery with excellent overall performance.

In order to solve this problem, the present invention activates the hydrogen storage alloy by activating the hydrogen storage alloy by occluding and releasing hydrogen as a processing step before incorporating the hydrogen storage alloy into the battery, thereby increasing the amount of hydrogen storage and reducing the variation. By using a small amount of hydrogen-absorbing alloy, we succeeded in obtaining a battery with excellent overall performance. Furthermore, in order to store the hydrogen storage alloy in the battery while maintaining its active state, an atmosphere of inert gas such as argon or other It has been found that it is even more effective to store or handle under vacuum or near-vacuum conditions.

It goes without saying that the hydrogen storage alloy used in the present invention needs to be chemically stable with respect to the electrolyte, but it may also cause leakage or expansion of the battery due to an increase in the internal pressure of the battery. To prevent deterioration, it is necessary to use an alloy that absorbs hydrogen at a pressure of 6 atm or less. Considering that batteries are used or stored at high temperatures of about 60"C, it is preferable to use an alloy that absorbs hydrogen at a pressure of 1 atm or less at room temperature. An example is Z rMn , (0< a (3,5).

ZrVβ (0<β<3.6), Ti1-Ti1-1zr
〈γ〈11M=Cr, Co, V, Mn, Ni,
Fe, Cu), CaN1a (3, ei<δ<6
．． 0), etc. In order to increase the hydrogen storage rate and storage amount, it is necessary to increase the number of activated sites in the hydrogen adsorption tank and expand the reaction area, and by adding the hydrogen storage and release steps described above, this purpose cannot be achieved. is,
The difficulty of activation varies depending on the material, but for many materials, 1 to 5 treatments are sufficient. Furthermore, this activation process increases the storage amount by several tens of percent to several times. As a general treatment method, after degassing by heating to about 200° C. while evacuation under reduced pressure, hydrogen is introduced until the pressure reaches about 60 atm at room temperature to occlude hydrogen. Next, a method is adopted in which the hydrogen in the container is evacuated and the process of storing hydrogen again at room temperature is repeated.

DESCRIPTION OF EXAMPLES Next, the details and results of a concrete study of the effects of the present invention will be described. The figure shows a cylindrical alkaline manganese dry battery that was prototyped to confirm the effects of the present invention. In the figure,
1 is a metal outer can, 2 is a positive electrode insulating ring, 3 is a negative electrode insulating ring, 4 is an insulating heat shrink tube, 6 is a metal positive terminal, 6 is a metal negative terminal, 7 is iron plated with nickel. The positive electrode case 8 is a positive electrode formed by pressure molding a mixture of graphite and manganese dioxide, and the reference numeral 9 is a separator formed into a cylindrical shape by double wrapping polypropylene nonwoven fabric. 1o is a powder of a hydrogen storage alloy treated in various ways as described below, and the upper opening 9' of the two-layer separator 9 and the part 9'' in contact with the vicinity of the top of the positive electrode 8 are each thermally welded. Powder 1o is stored in a cavity formed between two layers of separator 9.

11 is a bottom plate made of cellulose, and 12 is a gel-like zinc negative electrode made by dispersing zinc alloy powder in a caustic potassium aqueous solution gelled with carboxymethyl cellulose. A material with relatively good corrosion resistance, in which about 0.05% of the weight of zinc is added, is used, and no icing treatment is applied.

13 is a sealing plate made of polyethylene, and 14 is a brass-type negative electrode current collector whose surface is ice-treated with a small amount of mercury.

When an alkaline manganese dry battery configured as described above is stored, the negative electrode zinc is slightly but gradually corroded by the electrolyte during storage, and hydrogen gas is generated from the negative electrode 12. The hydrogen gas is accumulated in the space above the battery surrounded by the upper part, the sealing plate 13, and the positive electrode case 7, but the accumulated hydrogen gas sequentially passes through the separator 9 and is stored in the hydrogen storage alloy 10, thereby preventing an increase in the internal pressure of the battery. It has become a mechanism.

Next, in order to confirm the effects of the present invention, an AA battery was prototyped with the configuration shown in the figure and the details shown in the table.

In addition, all hydrogen storage alloys are pulverized in an argon atmosphere to a particle size of 10 to 100 μm, and fine powder of fluororesin with a particle size of 1 μm or less is added at a weight ratio of 1% to the hydrogen storage alloy. The mixture was stirred to give water repellency to 1°C. The products to which the present invention is applied include:
At least an activation process for occlusion and desorption is performed, in which hydrogen is degassed at 200°C under reduced pressure, hydrogen is absorbed to an almost saturated amount in hydrogen gas at 30 atm at room temperature, and hydrogen gas is almost completely released by reducing the pressure. The test was repeated once and used. After storing each prototype battery at ω°C for one month, the continuous discharge performance at 20°C and 10Ω, leakage resistance, and expansion were evaluated, and the results are shown in the right column of the table.

As can be seen in the margin table below, in case a, which does not use a hydrogen storage alloy, hydrogen gas generated from the negative electrode increases the internal pressure of the battery, resulting in significant leakage and expansion, and the hydrogen gas inhibits the discharge reaction, resulting in the maintenance voltage. There has been a significant drop in performance, and the connection time has become extremely short. Furthermore, even if a hydrogen storage alloy is used, no activation treatment is performed.

C1 and q also lack hydrogen storage capacity, so a
Similar obstacles remain. On the other hand, in the case of the product of the present invention, it has been shown that even with a very small amount (60 cm) of the hydrogen storage alloy, sufficient effects can be achieved by increasing the number of treatments as shown in e and h.
Even in the case of d and f, which were processed only once, a remarkable effect can be seen compared to the conventional example.

In addition, in the batteries shown in the table, the alloy was handled at room temperature and humidity in all processes up to its incorporation into the battery, including the process of sealing the activated and dehydrogenated hydrogen storage alloy in the upper part of the separator. On the other hand, activation treatment was performed only once, subsequent steps were performed in an argon atmosphere, and storage was performed only once.
When a similar evaluation was conducted for the reduction of 0 mmHy by 13. From this, it has been found that it is more effective to perform the activation treatment on the hydrogen storage alloy under an inert gas or vacuum or a reduced pressure close to this.

Effects of the Invention As described above, the present invention is extremely effective in obtaining a low-pollution primary battery with excellent overall practical performance using a very small amount of hydrogen storage alloy.

[Brief explanation of the drawing]

The figure is a side view with main parts cut away of a battery used in an example of the present invention. 8...Positive electrode, 9...Separator, 1o
...Hydrogen storage alloy, 12...Gel zinc negative electrode.

Claims (2)

[Claims] (1) A method for manufacturing a primary battery in which zinc is used as the main active material of the negative electrode, an alkaline aqueous solution or a neutral salt aqueous solution is used as the electrolyte, and a hydrogen storage alloy is housed in the battery. A method for manufacturing a battery, characterized in that the step of storing and releasing hydrogen is provided at least once beforehand. (2) The method for manufacturing a battery according to claim 1, in which the hydrogen storage alloy is treated in an inert gas, in vacuum, or under reduced pressure in the process after the hydrogen storage and release process is completed until it is incorporated into the battery. .