JPH05135763A - Alkaline storage battery - Google Patents

Abstract

PURPOSE:To increase the capacity of the negative electrode hydrogen storage alloy of a nickel-hydrogen storage battery and improve the overcharge characteristic and charge/discharge cycle life characteristic of the storage battery. CONSTITUTION:In an alkaline storage battery mainly constituted of a hydrogen storage allay and a positive electrode mainly made of a metal oxide, a negative electrode has a quickly cooled and coagulated CaCu5 structure, and it is mainly made of an alloy expressed by a general formula ABxVy, where A is a mixture of rare earth metals, B is mainly made of Ni and one of Co, Mn, Al, Fe, Cu, Cr or a mixture of them, for the range of the atomic number of elements, Ni>=3.4, Co<=1.0, x<=0.6 for Mn, x<=0.5 for Al, x<=0.3 for Fe, x<=1.0 for Cu, x<=0.3 for Cr, the atomic number (y) for V is 0.02<=y<=0.3, and (x+y) is 4.7-5.3.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art Heretofore, a nickel-hydrogen storage battery using a hydrogen storage alloy as a negative electrode and a nickel electrode as a positive electrode has been expected as a secondary battery capable of higher capacity than a nickel-cadmium storage battery.

Further, this hydrogen storage alloy for negative electrodes has hitherto been
It was manufactured by melting in a melting furnace and then adopting a cooling method as it is or a cooling method similar to that of slow cooling.

C is a typical alloy of the hydrogen storage alloy.
There is a LaNi ₅ alloy with an aCu ₅ structure. This LaN
When the i ₅ alloy is used as the negative electrode, there are problems that the cycle life is good but it is expensive, and the discharge capacity near room temperature is small. La for this problem
It has been proposed to replace Mm (Misch metal), which is a mixture of rare earth metals such as and Ce, with a relatively inexpensive MmNi ₅ alloy as a negative electrode. Further, by substituting a part of Ni with Mn, Al, Co or the like and lowering the horizontal equilibrium pressure, optimization as an electrode material is attempted. An example of these is MmNi _(5-xyz) Co _x Mn
_y M _z has been proposed (Japanese Patent Laid-Open No. 63-164161). Here, Mm is a mixture of at least three kinds of rare earth metals, M is Al, Cr, Fe, Cu, Sn, Sb,
One of Mo, V, Nb, Ta, Zn, Mg, Zr, and Ti, 0 <x ≦ 2, 0 <y ≦ 1.5, 0 <z ≦
It is 1.5.

[0005]

As an example of a conventionally known alloy, MmNi _3.55 Co _0.75 Mn _0.4 Al _0.3
When a sealed battery is constructed by using the MnNi ₅ alloy having the composition of as a negative electrode, a hydroxide is generated on the surface of the negative electrode alloy due to oxygen gas generated from the positive electrode during overcharging as the cycle progresses when charging and discharging are repeated, Since some of the components in the alloy are eluted, the hydrogen storage capacity and oxygen gas absorption capacity of the alloy decrease and the internal pressure of the battery rises. As a result, the safety valve (10 to 15% as in a normal nickel-cadmium battery)
(Operating at kg / cm ² ) and the electrolyte leaks, resulting in a decrease in charge / discharge cycle life characteristics.

Further, when rapid charging such as 1 hour rate is performed, the hydrogen storage capacity of the alloy is not sufficient, so that the internal pressure of the battery rises and the safety valve operates, resulting in the electrolyte leakage.

The present invention solves the above problems.
In particular, by increasing the hydrogen storage capacity of the alloy and improving the oxidation resistance, the battery internal pressure does not rise during rapid charging,
The purpose is to obtain an alkaline storage battery having excellent cycle life.

[0008]

In order to solve this problem, the alkaline storage battery of the present invention has a general formula A which is rapidly solidified.
The hydrogen storage alloy represented by B _x V _y was used as the negative electrode.

In the above general formula AB _x V _y , A is a mixture of rare earth metals selected from La, Ce, etc., B is mainly Ni, and Co, Mn, F
e, Cu, Cr, which is a mixture containing at least one of the elements, and Ni is x ≧ 3.
4, Co x ≦ 1.0, Mn x ≦ 0.6, Al x ≦
0.5, Fe is x ≦ 0.3, Cu is x ≦ 1.0, Cr is x ≦ 0.3, and V has an atomic number y of 0.02 ≦ y ≦.
It is 0.3 and (x + y) is 4.7-5.3.

[0010]

In the hydrogen storage alloy of the present invention, the hydrogen storage amount of the alloy increases when the alloy composition is added with V. Further, by producing the alloy by rapid solidification, the oxidation resistance of the alloy surface is improved. The combination of the alloy composition containing V and the rapid solidification can reduce the internal pressure of the battery at the time of rapid charging, and also suppress the reduction of the hydrogen storage capacity due to the oxidation of the alloy due to the charging / discharging cycle, so that the charging / discharging cycle life is also increased. Can be improved.

[0011]

EXAMPLES As A in the general formula AB _x V _{y of the} alloy of the present invention,
Commercially available misch metal Mm (La: 15% by weight, Ce:
50% by weight, Nd: 20% by weight, other rare earth metals: 15
% By weight), B as nickel (purity 99% or higher), cobalt (purity 99% or higher), manganese (purity 99% or higher)
And select one of aluminum, iron, copper, etc.
(Purity of 99% or more) and each sample were weighed and mixed in a constant composition ratio, put in an arc melting furnace, decompressed to 10 ^-4 to 10 ^-5 Torr, and then arc-discharged in an argon gas atmosphere (decompressed state). It melted by heating. This heat melting was repeated 4 times to prepare alloys of 12 kinds of compositions with symbols A to L as shown in (Table 1).

[0012]

[Table 1]

As a specific example of the rapid solidification, the case of using the ultra-quick roll method will be described below. First, after crushing the alloy produced by the above arc melting method into small pieces of about 5 to 15 mm, they are put into a quartz nozzle (nozzle hole 1.0 mm),
The quartz nozzle was installed in an ultra-quenching roll device, the inside of the device was replaced with argon gas, and then heated by a high-frequency heating coil to melt the alloy. After the alloy was melted, the inside of the quartz nozzle was pressurized with argon gas, the molten alloy was jetted onto a high-speed rotating copper roller, and rapidly cooled on the roller surface to obtain hydrogen storage alloys C to L. Among these hydrogen storage alloys, alloys C to H are alloys of the present invention, and alloys I to L are comparative alloys having different compositions from those of the present invention.

Further, the MmNi _3.6 Co _0.7 Mn _0.4 Al _0.3 alloy was prepared by arc melting method as a comparative example and comparative alloys A, was compared alloy B of _{MmNi 3.6 Co 0.7 Mn 0.3 Al 0.3} V 0.1 alloy.

The following tests were conducted using the above 12 kinds of hydrogen storage alloys. First, in order to investigate the effect of V addition on the discharge capacity, the discharge capacity of the hydrogen storage alloy was measured by an open H-type cell. First, the negative electrode was prepared by binding 1 g of the alloy and 3 g of Ni fine powder with polyethylene. This negative electrode and a nickel positive electrode having an excessive capacity are mixed with H
The battery was set in a mold cell and a charge / discharge test was performed in a state where the cell was sufficiently filled with an alkaline electrolyte. Charge / discharge test is conducted at a current value of
After the battery was charged with mA for 5.5 hours, the quantity of electricity when discharged at a current value of 50 mA to a voltage of 0.8 V was taken as the discharge capacity (mAh / g) of the alloy.

Secondly, a sealed battery was manufactured using these alloys, and the overcharge characteristics of the battery were investigated. First, alloys having the respective compositions shown in (Table 1) were crushed to a particle size of 38 μm or less, and a 1% by weight polyvinyl alcohol aqueous solution was mixed to form a paste. Next, this alloy paste was filled in a foamed nickel porous body, dried, immersed in an aqueous potassium hydroxide solution having a specific gravity of 1.30 at 80 ° C. for 12 hours, washed with water, dried, and pressed to form an electrode. .. An AA size sealed nickel-hydrogen storage battery having a positive electrode capacity regulation (capacity 1000 mAh) was constructed by using a negative electrode using the alloy of each composition shown in (Table 1) and a known foam metal nickel positive electrode.

After the battery was constructed, it was charged at 0.1 ° C mA for 15 hours at 20 ° C and discharged at 0.2 ° C mA. Then, a hole was made at the bottom of the battery case to measure the internal pressure of the battery, and a pressure sensor was attached to the battery at 1 ° C mA. The battery was charged for 1.5 hours, and the internal pressure of the battery during this charging was measured.

Thirdly, a charge / discharge cycle life test of a battery constructed by the same method as described above was conducted. 45 charge / discharge test
At a temperature of 1 ° C., charging was performed at 1 CmA for 1.5 hours, discharging was performed at 1 CmA and a discharging voltage was 0.8 V.

The experimental results of the discharge capacity of the alloy electrode by the H-cell of the half-cell type are shown in (Table 2). As shown in (Table 2), the comparative alloy A to which V was not added was 240 mAh /
Although it was g, it was 290 mAh / g or more in Comparative Alloy B to which V was added and Alloys C to H of the present invention. From this, it is considered that the addition of V has an effect of increasing the hydrogen storage amount, and the use of this alloy enables a high capacity battery. If the alloy capacity is 240 mAh / g, 1
When a battery of 000mAh is constructed, the capacity of the negative electrode with respect to the positive electrode is not sufficient to make rapid charging impossible, but when the alloy capacity is 290mAh / g or more, the capacity of the negative electrode with respect to the positive electrode is sufficient and rapid charging is possible. It is considered to be.

Next, the results of studying the amount of V added by a half-cell type H-type cell will be shown. The hydrogen storage alloy used in the study was produced by the rapid solidification method and its composition was MmN.
i _3. and the value of _{6 Co 0.7 Mn 0.4 Al 0.3-} y V y as atomic number y varied from 0 to 0.3. The hydrogen storage capacity of each alloy was investigated from the relationship between the V substitution amount y and the discharge capacity. The relationship between the substitution amount y of V and the discharge capacity is shown in FIG. As shown in FIG. 1, an alloy in which V is not substituted (MmNi
_The discharge capacity using _3.6 Co _0.7 Mn _0.4 Al _0.3 ) is 240
It was mAh / g. However, only 0.02 atoms of V are Al
When replaced with, the discharge capacity became 290 mAh / g. Further, the substitution of Al for V up to 0.3 atom has an excellent characteristic that the discharge capacity is 300 mAh / g or more. However, when the number of substituted atoms of V becomes 0.4, the discharge capacity becomes 15
It became 0 mAh / g. This is presumably because excessive V substitution deteriorated the uniformity of the alloy and resulted in a decrease in hydrogen storage capacity. Therefore, when substituting V for Al, the range of the number of substituting atoms for V is preferably 0.02 to 0.3. In addition, each element of Ni, Co, Mn, Fe, Cu, Cr is V
The same tendency as in the case of substituting V for Al was obtained when substituting for V.

Next, the results of examining the optimum composition range for each element other than V using a half-cell type H-type cell will be shown. The results of examining the relationship between the alloy composition and the discharge capacity of the alloy C of the present invention and the comparative alloys IL by changing the composition of the hydrogen storage alloy used for the negative electrode as in Comparative alloys IL of Table 1 The results are shown in Table 2). The electrode configuration conditions and charge / discharge test conditions were the same as those described above. As for the alloy compositions of Comparative Alloys H to K, Ni is 3.3 (Comparative Alloy I), Co is 1.1 Mn is 0.7 (Comparative Alloy J), and Mn is Mn.
Is 0.7 (Comparative Alloy K), Al is 0.6 (Comparative Alloy L)
When the alloy of No. 1 was used, the discharge capacity was 250 mAh / g or less even though V was contained.

[0022]

[Table 2]

Although not shown in (Table 2), Fe,
Similarly, when Cu and Cr are added, the number of atoms is 0.
When an alloy of 4,1.1,0.4 was used for the negative electrode, the discharge capacity was 250 mAh / g or less. Therefore, as an optimum composition range, Ni is at least 3.4, Co is at most 1.0, Mn is at most 0.6, Al is at most 0.5, and Fe is at most 0.
3 or less, Cu is preferably 1.0 or less, and Cr is preferably 0.3 or less. Next, FIG. 2 shows changes with time in the battery internal pressure of the battery using each alloy. As is apparent from FIG. 2, when the battery internal pressure of the battery using the negative electrode of Comparative Alloy A was 1 CmA,
At the end of charging, it increased to over 20 kg / cm ² and increased remarkably.
It is considered that this is because a large amount of hydrogen gas was generated at the end of charging due to the low hydrogen storage capacity of the hydrogen storage alloy of the negative electrode.

On the other hand, in the batteries using the comparative alloy B and the alloys C to H of the present invention, the internal pressure of the battery at the end of charging was 1.
It was 0 kg / cm ² or less. It is considered that this is because the increase in hydrogen storage capacity due to the addition of V suppressed the increase in the battery internal pressure at the end of charging.

The results of the charge / discharge cycle test are shown in FIG.
As is clear from FIG. 3, the capacity of the battery using the alloy A of the conventional example decreased at 250 cycles, and the capacity of the battery using the alloy B decreased at 400 cycles. However, the battery was manufactured by the rapid solidification method. 80 for batteries using alloys C to H
No deterioration of capacity was observed even after 0 cycles. It is considered that this is because the rapid solidification method improved the oxidation resistance and prevented the decrease in the oxygen gas absorption capacity at the end of charging.

[0026]

The alloy AB _x V _y rapidly solidified as described above has a low hydrogen equilibrium pressure, an increased hydrogen storage capacity, and excellent corrosion resistance. Therefore, the internal pressure of the battery increases during rapid charging. In addition, an alkaline storage battery having excellent cycle life can be provided.

[Brief description of drawings]

FIG. 1 is a diagram showing a relationship between a substitution amount y of V and a discharge capacity of an alloy of the present invention.

FIG. 2 is a diagram showing test results of battery internal pressure during rapid charging of the alloys of the present invention and comparative alloys.

FIG. 3 is a diagram showing test results of charge / discharge cycles and discharge capacities of the alloy of the present invention and the comparative alloy.

Front page continuation (72) Inventor Isao Matsumoto 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (2)

[Claims] 1. A positive electrode whose main constituent material is a metal oxide, a negative electrode whose main constituent material is a hydrogen storage alloy capable of electrochemically storing and releasing hydrogen as an active material, and an alkaline electrolyte. And a separator, the negative electrode has a rapidly solidified CaCu ₅ structure, and has the general formula AB _x V
An alkaline storage battery characterized by using an alloy represented by _y as a main constituent material. However, in the above general formula, A is a mixture of rare earth metals, B is a mixture containing Ni as a main component and one or more of Co, Mn, Al, Fe, Cu and Cr. Regarding the range of the number of atoms, Ni is x ≧ 3.4, Co is x ≦ 1.0, Mn is x ≦ 0.6, Al is x ≦ 0.5, Fe is x ≦ 0.3, and C is
u is x ≦ 1.0, Cr is x ≦ 0.3, V has an atomic number y of 0.02 ≦ y ≦ 0.3, and (x + y) is 4.7 to 5.3. .. 2. The alkaline storage battery according to claim 1, wherein the rapid solidification is performed by any one of an ultra-quenching roll method, a gas atomizing method and a centrifugal atomizing method.