JP3498545B2 - 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 an improvement of a current collecting structure from an electrode plate group of an alkaline storage battery.

[0002]

2. Description of the Related Art In recent years, as electric devices have become lighter, thinner, shorter, and smaller, there has been an increasing demand for small high-capacity batteries as their power sources. In alkaline storage batteries, which are highly reliable batteries, along with this trend, the capacity of nickel-cadmium storage batteries has been increased, and improvements have been made in metal oxide-hydrogen storage batteries that use a hydrogen storage alloy with a high energy density for the negative electrode. ing.

Since this type of alkaline storage battery is an aqueous battery, it has a great advantage that it can be charged and discharged with a large current. Generally, in these batteries, a separator is interposed between a positive electrode and a negative electrode to form a spiral electrode plate group, and then a plate-shaped current collector is attached to the electrode plate tips of the positive electrode plate and the negative electrode plate protruding above and below the group. It was welding.

[0004]

When the metal oxide-hydrogen storage battery is used for a large current discharge, the large current discharge characteristic is deteriorated especially at low temperature. This is presumed to be because the decrease in the reactivity of the negative electrode is larger when the hydrogen storage alloy is used as compared with the conventional cadmium.

It is an object of the present invention to provide an alkaline storage battery which has an improved current collecting structure as a battery to suppress a decrease in the reactivity of the negative electrode at a low temperature and which has an excellent large current discharge characteristic even at a low temperature. It is a thing.

[0006]

In order to achieve the above object, the present invention provides an electrode in which a positive electrode plate and a negative electrode plate made of a hydrogen storage alloy are arranged above and below a separator via a separator so that the electrode plate tips protrude. An alkaline storage battery having a plate group, in which plate-shaped current collectors are respectively welded to the electrode plate tip portions projecting up and down of the electrode plate group, wherein the number of welding points between the current collector and the electrode plate tips is It is characterized in that the number of electrodes is larger on the negative electrode side than on the positive electrode side.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The invention according to claim 1 has an electrode plate group in which a positive electrode plate and a negative electrode plate made of a hydrogen storage alloy are arranged above and below a separator via a separator so that the electrode plate tips project respectively. , Which is an alkaline storage battery in which plate-shaped current collectors are welded to the electrode plate tip portions protruding above and below this electrode plate group,
The battery has a configuration in which the number of welding points between the plate-shaped current collector and the electrode plate tips above and below the electrode plate group is larger on the negative electrode side than on the positive electrode side. According to this current collecting structure, it is possible to reduce the electric resistance of the current collecting path of the negative electrode to suppress the decrease in reactivity of the negative electrode at low temperatures, and it is possible to provide an alkaline storage battery having excellent large current discharge characteristics even at low temperatures.

[0008]

The present invention will be described in detail below.

The negative electrode material has a composition of MmNi _3.55 Co
A hydrogen storage alloy of _0.75 Mn _0.4 Al _0.3 (Mm represents a mixture of rare earth elements) was crushed with a wet ball mill,
An average particle size of about 30 μm was used. After stirring the alloy powder in a KOH aqueous solution at 80 ° C., 0.15 parts by weight of carboxymethyl cellulose and 0.3% of carbon black are added to 100 parts by weight of the hydrogen storage alloy powder.
By weight, 0.8 part by weight of a styrene-butadiene copolymer was added, and an appropriate amount of water was added as a dispersant to prepare a paste. This paste was applied on both sides of a punching metal, dried, and then pressed to a predetermined thickness and cut into a predetermined size to obtain a negative electrode plate. A known sinter-type nickel positive electrode was used for the positive electrode plate, and a sulfonated polypropylene nonwoven fabric was used for the separator.

Using these negative / positive electrode plates, separators and negative electrodes, a spiral electrode plate group was prepared so that the electrode plate tips of the positive electrode plate and the negative electrode plate were projected vertically as shown in FIG.
As shown in (Table 1), the number of welding points in the series spot welding of the electrode plate group and the plate-shaped current collector was changed to obtain a capacity of 2500
mAh SC size batteries A, B, C and D were produced.
In the figure, 1 is a nickel positive electrode plate, 2 is a hydrogen storage alloy negative electrode plate, 3
Is a separator, 4 is a battery case, 5a is a plate-shaped positive electrode current collector, and 5b is a plate-shaped negative electrode current collector.

For comparison, an ordinary Cd electrode was used as the negative electrode to form an SC size battery having a capacity of 2000 mAh, and batteries E, F, which were different in the number of welding points, which were the current collecting points between the electrode plate and the current collector, were used. G and H were also created.

A discharge characteristic test was conducted using the batteries A to H. In the discharge characteristic test, the charge was 20 ° C. and the current value was 0.
The battery is charged to 150% of the battery capacity at 1 CmA, left for 1 hour, discharged at 0 ° C., and the current value is 1 CmA to 1.0 V.
The ratio of discharge capacity to battery capacity was evaluated. The results are shown in (Table 1).

[0013]

[Table 1]

As is clear from the results shown in Table 1, the battery using the cadmium electrode as the negative electrode is not significantly affected by the number of welding points between the positive electrode and the negative electrode plate and the current collector.
On the other hand, it was found that the battery using the hydrogen storage alloy is greatly affected by the number of welding points between the positive electrode plate and the negative electrode current collector.

It is presumed that this is due to the influence of the negative electrode because the reactivity of the negative electrode side becomes lower than that of the positive electrode side at low temperatures. In particular, when a hydrogen storage alloy is used for the negative electrode, the reactivity at low temperature is significantly lower than that of cadmium, and it is speculated that the discharge characteristics are significantly reduced.

Generally, the reactivity of the electrode is greatly influenced by the reactivity of the active material itself and the electrode resistance such as contact resistance. Since the equilibrium pressure of the hydrogen storage alloy is lowered at low temperature, the hydrogen releasing ability is lowered and the reactivity of the active material is lowered. In addition, since the electrode resistance such as the contact resistance between the active materials also increases at low temperature, the reactivity of the entire negative electrode is significantly lower than that of the negative electrode using cadmium.

For the above reasons, the nickel-hydrogen storage battery has lower low temperature characteristics than the nickel-cadmium storage battery.

In order to improve the low temperature characteristics of the nickel-hydrogen storage battery, the reactivity of the negative electrode should be improved, that is, the reactivity of the hydrogen storage alloy at low temperature should be improved, or the electrode resistance such as the contact resistance between the active materials should be improved. It is necessary to reduce.

The present invention, in which the number of welding points between the positive electrode plate and the plate-shaped current collector of the negative electrode plate is changed, is one of the measures for reducing the electrode resistance. A nickel-containing hydrogen storage alloy is used for the negative electrode.
It is particularly effective for hydrogen storage batteries.

The relationship between the number of welding points of the negative electrode plate with the current collector and the number of welding points of the positive electrode plate with the current collector is the same or more than that of the negative electrode plate as compared with the number of welding points of the positive electrode plate. In the batteries C and D, the discharge capacity and the discharge voltage were higher than those of the batteries A and B in which the number of welding points on the negative electrode plate side was less than or equal to the number of welding points on the positive electrode plate side. This is because when the number of welding points on the negative electrode plate side is set to be less than that on the positive electrode plate side, not only the reactivity of the hydrogen storage alloy decreases but also the increase of the electrode resistance becomes non-negligible, and the reactivity on the negative electrode plate side is significantly reduced. It is presumed that it is due to

On the other hand, in a battery in which the number of welding points on the negative electrode plate side is more than that on the positive electrode plate side, does the electrode resistance increase?
Or, since the increase is small, the reactivity of the negative electrode substantially only affects the reactivity of the hydrogen storage alloy itself,
It seems that the influence on the discharge characteristics is reduced.

According to the experiments conducted by the present inventors, it was found that the number of welding points on the negative electrode plate side is preferably 1.2 to 1.6 as an index when the number of welding points on the positive electrode plate side is 1. This is because by increasing the number of welding points on the negative electrode plate side, the connection resistance between the negative electrode plate and the plate-shaped current collector can be made extremely small and the negative electrode resistance can be reduced. It should be noted that increasing the number of welding points on the negative electrode plate side to about twice that on the positive electrode plate side should be avoided because it complicates spot welding and tends to cause thermal deterioration of the end portion of the separator.

If the discharge capacity of 1 CmA at low temperature, especially at 0 ° C. is about 70% of the battery capacity at room temperature, there will be no practical problem. Therefore, the number of welding points on the negative electrode plate side is more than that on the positive electrode plate side. Therefore, it is desirable to set 1.2 to 1.6 times.

In the above embodiments, the spiral nickel-hydrogen storage battery has been described as an example, but the current collecting structure of the present invention can be applied to other nickel-hydrogen storage batteries such as prismatic batteries. By adopting this, it is possible to obtain the same effect of improving the large current discharge characteristics at low temperatures.

The form of the positive and negative electrode plates used in the battery of the present invention may be any of a foam metal type, a sintering type, a coating type, etc., and is the same regardless of the electrode plate form. The effect of can be obtained.

[0026]

As described above, according to the present invention, by increasing the number of welding points between the plate-shaped current collector and the tips of the positive and negative electrode plates on the negative electrode side rather than on the positive electrode plate side, It is possible to provide a nickel-hydrogen storage battery that is excellent in large-current discharge even at low temperature by suppressing the decrease in reactivity of the negative electrode plate.

[Brief description of drawings]

FIG. 1 is a cutaway view of a battery according to an embodiment of the present invention.

2A is a top view for explaining an electrode plate group according to an embodiment of the present invention, and FIG. 2B is a bottom view for explaining the same.

[Explanation of symbols]

1 Nickel positive electrode plate 2 Hydrogen storage alloy negative electrode plate 3 separator 4 battery case 5a Positive electrode current collector 5b Negative electrode current collector

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Fumihiko Yoshii 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (56) Reference JP-A-5-190166 (JP, A) JP-A-63- 207059 (JP, A) Actual development 61-80563 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01M 10/28 H01M 10/30 H01M 2/22

Claims (2)

(57) [Claims] 1. An electrode group, in which a nickel positive electrode plate and a negative electrode plate made of a hydrogen storage alloy are arranged above and below a separator via a separator so that the electrode plate tips protrude, respectively, and each electrode plate has a protruding tip portion. An alkaline storage battery in which a plate-shaped current collector is welded, wherein the number of spot-welded spots between the plate-shaped current collector and the electrode plate tip is larger on the negative electrode side than on the positive electrode side. . 2. The alkaline storage battery according to claim 1, wherein the ratio of the number of welding points between the tip of the positive electrode plate and the plate-shaped current collector to that of the negative electrode is 1: 1.2 to 1.6.