JPS6280963A - Sealed alkaline storage battery - Google Patents

Abstract

PURPOSE:To increase charge-discharge cycle life by using a negative electrode comprising a specified metal oxide soluble type hydrogen occlusion alloy or hydride, a positive electrode, a separator, and alkaline electrolyte. CONSTITUTION:A negative electrode consists of a metal oxide soluble type hydrogen occlusion alloy in which oxygen is contained as an oxide of metal (element) constituting hydrogen occlusion alloy in the hydrogen occlusion alloy which electrochemically absorbs and desorbs hydrogen. The negative electrode 1 and a nickel positive electrode 2 are spirally wound via a separator 3 and they are accommodated in a case (a negative case) 4, and insulating plates 5, 6 are placed, then the case is sealed with a sealing plate 8 having a safety vent 7. Since oxygen is contained in the alloy in a form of oxide, the swelling of the negative electrode is reduced, and the distribution of electrolyte in the battery is uniformly kept without removing of electrolyte held in the separator. Thereby, a sealed alkaline storage battery in which increase in internal resistance caused by increase in the number of cycles is decreased and cycle life is increased can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a sealed alkaline storage battery using a hydrogen storage alloy that electrochemically stores and releases hydrogen as a negative electrode.

(Prior art) Lead-acid batteries and nickel-cadmium storage batteries are the most widely known secondary batteries, but because these batteries contain a solid active material in the negative electrode, the per unit weight or capacity Energy storage capacity is relatively low. In order to improve this energy storage capacity, storage batteries have been proposed that use a hydrogen storage alloy as the negative electrode and, for example, nickel oxide as the positive electrode (U, S, P 3,874,928).
. This battery system has higher capacity than Mozukeru cadmium storage batteries and is expected to be a low-pollution storage battery.

Batteries using LaNi5 alloy as a negative electrode as a representative example of the prior art have a problem of short cycle life.

Moreover, since La, which is the main constituent metal of the alloy, is expensive, the cost of the electrode itself is naturally high. Therefore, this L
An electrode composition that improves the aNi5 alloy negative electrode and lowers the cost has been proposed (Japanese Patent Laid-Open No. 13934/1983). That is, part or all of La wo MrrI (Mitsushi Metal)
This is a battery using LnNi 5 *LnCo5 system substituted with .

On the other hand, in Japanese Patent Application Laid-Open No. 49-15933, oxygen is introduced at the grain boundary between Ti2Ni and T1Ni, and Ti2N1 and T1
There is a proposal to extend the life by reducing the expansion strain between Ni. However, it is unclear whether this oxygen is added in the form of g, and the text describes a method of mixing oxygen as an oxygen atmosphere during alloy production, but this method does not allow the use of oxygen in the negative electrode of a sealed alkaline storage battery. In this case, the desired results were not obtained.

(Problems to be solved by the invention) Sealed storage batteries using LaNi M+nNi 5 as the negative electrode have problems such as being expensive, having a small discharge capacity, and short cycle life. An alloy system has been proposed in which the negative electrode itself expands with the number of cycles, but the electrolyte distribution within the battery is unbalanced due to the expansion of the negative electrode itself, resulting in an increase in battery resistance and a reduction in discharge voltage, which may lead to performance improvements. It has a certain point.

In view of the above-mentioned problems, the present invention aims to provide a sealed alkaline storage battery in which a negative electrode is constructed using a relatively inexpensive material, an increase in internal resistance of the battery is suppressed, and a charge/discharge cycle life is long.

(Means for Solving the Problems) The present invention provides an unsealed alkaline storage battery having a negative electrode, a positive electrode, a central electrode, and an alkaline electrolyte, in which the negative electrode electrochemically absorbs and releases hydrogen. It is characterized by being made of a metal oxide-dissolved hydrogen storage alloy or hydride in which oxygen is contained in the storage alloy as an oxide of the metal (element) constituting the hydrogen storage alloy.

(Function) When a hydrogen-absorbing alloy electrochemically absorbs hydrogen, it tends to become finer and expand at the same time, as in the case of absorbing hydrogen in a gaseous state. This is because the lattice constant of the alloy itself is different when hydrogen is occluded and when it is not, and it is slightly larger when hydrogen is occluded. In order to suppress this phenomenon as much as possible, in the present invention, oxides of metals (elements) constituting the hydrogen storage alloy are added. If it is an oxide of another metal (element), the metal and oxide may not fuse.
Fusing oxides of the same type as in the present invention has a greater effect.

(Example) Commercially available Mm (missile metal) and La (lantern).

A sample consisting of Ni, nickel) and Co (cobalt) was weighed and mixed at a constant composition ratio, and heated and melted using an arc melting method.

The blood mentioned here is a mixture of rare earth metals that is generally commercially available, and its composition is La (lanthanum): 25 to 35.
Heavy t%, ce (cerium), :40-50 heavy weight%, Nd
(Neodymium): 5 to 15% by weight, 'Pr (praseodymium) = 2 to 10% by weight, and other rare earth metals: 1 to 5% by weight.

In addition, at least one type of L as a metal oxide is added to the above sample.
A2O3+Co0eNiOe was added in a weight ratio of 0.05 to 2 and simultaneously melted to produce a metal oxide dissolving type hydrogen storage alloy.

For comparison, a hydrogen storage alloy without the addition of metal oxides was manufactured and used as a conventional type.

After coarsely grinding these alloys,? - After making it into a fine powder of 38 μm or less using Lumil, etc., mix it with a P, V, A (polyvinyl alcohol) resin solution (approximately 1% by weight), and put this yeast-like alloy into a foamed metal porous body (support). After filling and drying under pressure, the leads were attached as electrodes. Alloy (or hydride) 17! A sealed AA alkaline storage battery (capacity 2.0 Ah) as shown in FIG. In Fig. 1, a negative electrode plate 1 made of a hydrogen storage alloy and a nickel positive electrode 2 are arranged in a spiral shape in a case (→4) via a central plate 3, and an insulating plate 5. It is sealed with a sealing plate 8. 9 is a positive electrode terminal (1) connected to a positive electrode lead 10.

In addition, in order to comply with the positive electrode law, the charging and discharging conditions for a battery with larger positive electrode capacity than negative electrode capacity are 0.2 C (
Charge at 0.2C (400mA) for 7 hours,
) was discharged. The temperature in all charge/discharge cycle tests was room temperature, and the internal resistance of the battery was measured every 20 cycles to examine the state of liquid distribution within the battery.

The batteries used in this example were AA size (standard nominal capacity 1.
65Ah), and is filled with a large amount of co-active material for the positive and negative electrodes to have a higher capacity than the standard capacity, so the balance of the amount of electrolyte has a great effect on the long life. In this example, as an example, the alloy composition is Wkno, 5
Select La Q,5 NI K 5 CO1,5 and add La2O3(A), Coo(
B) After preparing a hydrogen storage alloy using NiO(C), etc., the alloy was mixed in a powder state and remelted. .

Figure 2 shows the relationship between charge/discharge cycles and battery internal resistance.

When the first internal resistance of the battery is measured after the initial cycle test (20 cycles), fA), (B), (C)
, CD).

(E) Both were 6 to 8 mΩ with almost no significant difference. but,
As the number of cycles increases, conventional batteries (F3
The resistance increases gradually, and after 100 cycles it increases sharply. On the other hand, in the batteries according to the present invention, except for (C), the resistance is within the range of 10 to 15 mΩ, and no significant increase in resistance is observed. However, although C) has a higher internal resistance than other batteries, it is still less than 1/3 of the conventional type.

In conventional batteries, the electrodes expand with the number of cycles, and the amount of electrolyte held in the battery cell gradually decreases, causing a change in the distribution of the amount of electrolyte when first injected, resulting in a large internal resistance. It has become. Since the discharge current is 400mA, 1
When the resistance becomes 00 mΩ, the battery voltage decreases by 0.04 V.

If the intermediate voltage is 1.25 V, the voltage will drop to 1.21 V, which will cause a corresponding drop in output, which will be a big problem in practice. Conventional batteries have a major problem from this point of view. On the other hand, in the battery according to the present invention, oxygen is fused in the form of oxide in the alloy, so the expansion of the negative electrode itself is small and the electrolyte held in the separator can be removed. The distribution of the electrolyte within the battery is maintained without any problems. This tendency is particularly strong in batteries designed to increase the capacity, so the influence of the balance of the amount of electrolyte becomes noticeable. Ni0
In the case of (C), the performance is slightly lower than that of other oxides.

This is also influenced by the fact that it is difficult to dissolve homogeneously.

Further, if the amount of La2O3 is less than 0.049% by weight, the effect will be small, and if it is more than 1.01% by weight, the metal oxide will not be dissolved homogeneously and the properties of the alloy itself will change. In other words, 0
．． A weight ratio of 05 to 2 is desirable.

The amount of Coo also has the same properties as La2O3 and shows a similar tendency. On the other hand, NiO is 0.05 to 1.5% by weight.
is desirable, and even if a large amount was added, it did not produce the same effect as La2O3. In addition, alloy powder and metal oxide (here La
It is thought that the alloy obtained by mixing the powder (using 2O3) and remelting it has the best properties, and that the two are homogeneously fused. As the amount of oxide increases, some parts are observed where it does not fuse with the alloy and precipitates, so the range shown in the present invention is considered to be optimal.

Adding metal oxides other than those in the alloy composition has some effect, but it is good if it can be harmoniously fused with the alloy, but if it is not, it can have the opposite effect. As an example, Mm
(La)NiCoAlthough the four elements are listed above, almost the same effect can be expected even if starting from other alloy systems or hydrides.

(Effects of the Invention) As described above, according to the present invention, a sealed alkaline storage battery with a long cycle life and a small increase in battery internal resistance with the number of cycles can be obtained.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the structure of a sealed alkaline storage battery using the negative electrode of the present invention. FIG. 2 is a diagram comparing a conventional battery and a battery of the present invention with respect to the relationship between the number of cycles and the internal resistance of the battery. 1... Negative electrode plate, 2... Positive electrode plate, 3... Separator, 4... Case (→, 5, 6... Insulating plate, 7...
- Safety valve, 8... Sealing plate, 9... Positive electrode lead.

Claims (3)

[Claims] (1) A metal oxide-dissolved hydrogen storage alloy that electrochemically absorbs and releases hydrogen, and which contains oxygen as an oxide of the metal (element) that constitutes the hydrogen storage alloy. Or a sealed alkaline storage battery having a negative electrode made of a hydride, a positive electrode, a separator, and an alkaline electrolyte. (2) The hydrogen storage alloy mainly contains 25 to 70% by weight of La.
It is composed of rare earth metals containing La_2O, nickel, cobalt, etc., and at least one metal oxide contains La_2O.
_3, CoO, NiO, etc., each of which is 0.05~
2% by weight (La_2O_3), 0.05-2% by weight (C
The sealed alkaline storage battery according to claim 1, wherein the amount of NiO is within the range of 0.05 to 1.5% by weight (NiO). (3) Claims in which a metal oxide-dissolved hydrogen storage alloy or hydride, which is obtained by mixing a previously dissolved hydrogen storage alloy and a metal oxide in powder form and then melting the two again, is used as the negative electrode. The sealed alkaline storage battery described in paragraph (1).