JP3157237B2 - Metal-hydrogen alkaline storage battery - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal-hydrogen alkaline storage battery having a negative electrode mainly composed of a hydrogen storage alloy, a positive electrode composed of a metal oxide, and an alkaline electrolyte.

[0002]

2. Description of the Related Art Conventional storage batteries include alkaline storage batteries such as nickel-cadmium storage batteries and lead storage batteries. However, in recent years, attention has been paid to a metal-hydrogen alkaline storage battery provided with a negative electrode of a hydrogen storage alloy which is lighter, has a higher capacity, and may have a higher energy density than these batteries.

[0003] By the way, this kind of metal-hydrogen alkaline storage
Examples of hydrogen storage alloys used in batteries include, for example,
As shown in JP-A-59-49671, LaNi_FiveAnd
A three element LaNi that is an improvement_FourCo, LaNi_Four
Cu and LaNi_4.8Fe _0.2Etc. are known alloys
You. As shown in Japanese Patent Publication No. 57-30273,
The mixture of the hydrogen storage alloy powder and the conductive agent powder is resistant to
Electrode support with alkaline electrolyte particulate binder
The negative electrode is fixed by a method such as fixing to form a hydrogen storage alloy electrode.
It is made. In addition, in order to reduce manufacturing costs, La
Various rare earth water using Mm (Misch metal) instead
Element storage alloys have also been developed.
No. 558, MmNi_ThreeCo_1.5Al
_0.5Such as aluminum and cobalt
Uses elemental hydrogen storage alloy to improve charge / discharge cycle characteristics
What has been proposed has been proposed.

On the other hand, a sintered nickel electrode used for a nickel-cadmium storage battery is used as a positive electrode. Meanwhile, a potassium hydroxide solution has been conventionally used as an electrolyte for a battery having the positive and negative electrodes having the above structure in consideration of charging and discharging efficiency. However, a battery using this electrolytic solution has a problem that the hydrogen storage alloy is deteriorated and self-discharge cannot be sufficiently suppressed.

[0005] Therefore, as disclosed in Japanese Patent Application Laid-Open No. 61-214370, an electrolytic solution in which a trace amount of lithium hydroxide is added to potassium hydroxide has been proposed. When such an electrolytic solution is used, self-discharge can be suppressed, so that storage characteristics can be improved and charge / discharge efficiency can be improved.

[0006]

However, when the above-mentioned electrolytic solution is used, the conductivity of the electrolytic solution decreases due to an increase in the viscosity of the electrolytic solution. For this reason, there was a problem that the operating voltage at the time of high-rate discharge was reduced. The present invention has been made in view of the current situation, and is capable of increasing the operating voltage during high-rate discharge and improving the cycle characteristics.
It aims to provide hydrogen-alkaline storage batteries.

[0007]

SUMMARY OF THE INVENTION In order to achieve the above-mentioned object, the present invention provides a metal alloy comprising a negative electrode mainly composed of a hydrogen storage alloy, a positive electrode composed of a metal oxide, and an alkaline electrolyte.
In the hydrogen-alkaline storage battery, at least one hydroxide selected from the group consisting of rubidium hydroxide and cesium hydroxide is added in an amount of 0.3 N to 3.5 N in the alkaline electrolyte.

[0008]

With the above construction, rubidium hydroxide and cesium hydroxide added to the electrolytic solution are converted into rubidium ions or cesium ions in the electrolytic solution. In this case, the hydration power of these ions is lower than that of lithium ions (produced from lithium hydroxide that has been conventionally added), so that the conductivity of the electrolytic solution is improved. As a result, the operating voltage can be increased particularly at the time of high-rate discharge affected by the conductivity of the electrolytic solution.

Although the reason is not clear, rubidium ions and cesium ions are adsorbed on the surface of the hydrogen storage alloy, and these ions act as a catalyst. Can be higher. Furthermore, the reason why the addition ratio of rubidium hydroxide or the like is set to 0.3 N to 3.5 N is that if the addition ratio is less than 0.3 N, the effect of addition is not sufficiently exhibited, whereas if it exceeds 3.5 N, the viscosity of the electrolytic solution is reduced. This is because the operating voltage at the time of high-rate discharge is reduced because it is too high.

[0010] In addition, with the above configuration, the amount of water around the hydrogen storage alloy is reduced because the electrolyte has an appropriate hydration power. Therefore, since the pulverization of the hydrogen storage alloy can be suppressed, the cycle characteristics are also improved.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS. Embodiment 1 FIG. 1 is a cross-sectional view of a sealed cylindrical nickel-hydrogen alkaline storage battery according to one embodiment of the present invention, in which a positive electrode 1 made of sintered nickel and a negative electrode 2 containing a hydrogen storage alloy powder and a binder are shown. The electrode body 4 composed of the separator 3 interposed between the positive and negative electrodes 1 and 2 is spirally wound. The electrode body 4 is disposed in an outer can 6 also serving as a negative electrode terminal. The outer can 6 and the negative electrode 2 are connected by a negative electrode conductive tab 5. A sealing body 8 is attached to the upper opening of the outer can 6 via a packing 7, and a coil spring 9 is provided inside the sealing body 8. The coil spring 9 is configured such that when the internal pressure inside the battery rises abnormally, it is pressed in the direction of arrow A and the gas inside is released to the atmosphere. The sealing body 8 and the positive electrode 1 are connected by a positive electrode conductive tab 10.

Here, the electrolyte is KOH
An electrolytic solution obtained by adding RbOH (0.3N) to (6.7N) is used. Next, the sealed cylindrical nickel-hydrogen alkaline storage battery having the above structure was manufactured as follows.
First, as a raw material metal of the hydrogen storage alloy, Mm (mixture of rare earth elements), Ni, Co and A
1 and Mn are in an element ratio of 1: 3.2: 1: 0.2: 0.6.
After being weighed so as to obtain, they are mixed, and further melted and cast in a furnace. Thereby, MmNi _3.2 CoAl
An alloy having a composition of _0.2 Mn _0.6 is produced. Next, the alloy ingot is pulverized and pulverized, and 5% by weight of PTFE (fluororesin) as a binder is added to 95% by weight of the pulverized alloy and uniformly mixed. The above-mentioned PTFE is fiberized, and water is further added thereto to form a paste. Thereafter, the paste was pressure-bonded to both surfaces of a nickel-plated punched metal current collector to produce a negative electrode 2.

The thus-prepared negative electrode 2 and a known positive electrode 1 made of sintered nickel are wound together with an alkali-resistant separator 3 to form a spiral electrode body 4. 4 was inserted into the outer can 6. Thereafter, the electrolytic solution having the above composition was poured into the outer can 6, and the outer can 6 was further sealed to produce a cylindrical sealed nickel-hydrogen battery having a nominal capacity of 1000 mAh.

The battery fabricated in this manner is referred to as (A)
₁ ) Called a battery. [Examples 2 to 6] Batteries were produced in the same manner as in Example 1 except that the composition of the electrolytic solution (ratio between KOH and RbOH) was set as shown in Table 1 below. The batteries fabricated in this manner are hereinafter referred to as (A ₂ ) battery to (A ₆ ) battery, respectively. [Examples 7 and 8] Using CsOH instead of RbOH,
A battery was manufactured in the same manner as in Example 1 except that the ratio between KOH and CsOH was set as shown in Table 1 below.

The batteries fabricated in this manner are hereinafter referred to as (A ₇ ) battery and (A ₈ ) battery, respectively.

[0016]

[Table 1]

Comparative Example 1 A battery was manufactured in the same manner as in Example 1 except that RbOH was not added to the electrolytic solution. The battery fabricated in this manner is hereinafter referred to as (X ₁ ) battery. Comparative Examples 2 and 3 A battery was produced in the same manner as in Example 1 except that the composition of the electrolytic solution (ratio between KOH and RbOH) was set as shown in Table 1 above.

The batteries fabricated in this manner are hereinafter referred to as (X ₂ ) battery and (X ₃ ) battery, respectively. [Experiment 1] The high-rate discharge characteristics of the batteries (A ₁ ) to (A ₈ ) of the present invention and the batteries (X ₁ ) to (X ₃ ) of the comparative example were examined. Shown in The experimental conditions were as follows: after charging at a current of 1000 mA for 1.25 hours,
The condition is that the battery is discharged at a current of 4000 mA until the battery voltage reaches 1.0 V. Further, in Table 2, the discharge capacity when charging and discharging under the above conditions is shown, with the nominal capacity as 100.

[0019]

[Table 2]

As is clear from Table 2, the batteries (A ₁ ) to (A ₈ ) of the present invention have a larger discharge capacity than the batteries (X ₁ ) to (X ₃ ) of the comparative example. Is recognized. In particular, in the (A ₃ ) battery to (A ₅ ) battery, (A ₇ ) battery, and (A ₈ ) battery in which the concentration of RbOH or CsOH is 1 to _3.5 N, the discharge capacity is significantly large. It is recognized that.

Therefore, the concentration of RbOH or CsOH needs to be in the range of 0.3-3.5N, especially 1N.
It is desirable that the number be between three and three. FIG. 2 shows discharge curves of the (A ₂ ) battery, the (A ₄ ) battery of the present invention, and the (X ₁ ) battery of the comparative example at the time of the high-rate discharge. As is clear from FIG. 2, (A ₂ )
It can be seen that the operating voltage of the battery and the (A ₄ ) battery was increased by 20 mV or more as compared with the (X ₁ ) battery of the comparative example. [Experiment 2] The batteries (A ₁ ) to (A ₈ ) of the present invention and the battery (X) of the comparative example
₁ ) The cycle characteristics of the batteries to (X ₃ ) batteries were examined, and the results are also shown in Table 2 above. The experiment conditions were the same as those in Experiment 1, and the cycle life was determined when the discharge capacity reached 50% of the nominal capacity.

As is clear from Table 2, the batteries (A ₁ ) to (A ₈ ) of the present invention have a longer cycle life than the batteries (X ₁ ) to (X ₃ ) of the comparative example. Is recognized. In particular, (A ₃ ) battery to (A ₅ ) battery in which the concentration of RbOH or CsOH is 1N to 3N,
It is recognized that the cycle life of the (A ₇ ) battery and the (A ₈ ) battery is much longer.

Therefore, the concentration of RbOH or CsOH must be in the range of 0.3 to 3.5, not only in terms of high-rate discharge but also in terms of cycle characteristics.
It is desirable that the number be between three and three. [Other Matters] In the above embodiment, rubidium hydroxide and cesium hydroxide are added alone, but the same effect can be obtained by adding both of them. However, also in this case, the total of the rubidium hydroxide and the cesium hydroxide is 0.3N to 3N.
It is necessary to be 5 regulations. In the above embodiment, MmNi _3.2 C was used as the hydrogen storage alloy.
Although oAl _0.2 Mn _0.6 is used, the present invention is not limited to this, and the same effects as described above can be obtained with batteries using other hydrogen storage alloys.

[0024]

As described above, according to the present invention, since the conductivity of the electrolytic solution is improved and rubidium ions and the like act as a catalyst, the operating voltage can be increased during high-rate discharge. In addition, since the electrolyte has an appropriate hydration power, an excellent effect of improving the cycle characteristics of the battery can be obtained.

[Brief description of the drawings]

FIG. 1 is a sectional view of a sealed cylindrical nickel-hydrogen alkaline storage battery according to an example of the present invention.

FIG. 2 is a graph showing the relationship between the discharge capacity and the discharge voltage in the (A ₂ ) battery of the present invention, the (A ₄ ) battery and the (X ₁ ) battery of the comparative example.

[Explanation of symbols]

 1 positive electrode 2 negative electrode 3 separator

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-B-39-977 (JP, B1) JP-T2-502499 (JP, A) (58) Fields surveyed (Int. Cl. ⁷ , DB name) H01M 10/24-10/30

Claims (1)

(57) [Claims] 1. A metal-hydrogen alkaline storage battery comprising a negative electrode mainly composed of a hydrogen storage alloy, a positive electrode made of a metal oxide, and an alkaline electrolyte, wherein the alkaline electrolyte contains rubidium hydroxide and hydroxide. A metal, characterized in that at least one hydroxide of cesium is added in an amount of 0.3 N to 3.5 N.
Hydrogen alkaline storage battery.