JPS6199278A - Metal-hydrogen alkaline storage battery - Google Patents

Abstract

PURPOSE:To suppress capacity drop at a negative electrode by brining a negative electrode, equipped with hydrogen occluding alloy, into contact with the inner face of an armored cell can either directly or through heat conductive material of grease. CONSTITUTION:A negative electrode 2, situated at the outer face of an electrode body and equipped with hydrogen occluding alloy, is brought into contact with the inner face of an armored cell can 4 either directly or through conductive material of grease. Then heat generating at the negative electrode during charge is conducted from the negative electrode, which is situated at the outer face of the electrode body, to the metal armored cell can 4, and the heat is quickly released from the surface of the can 4, being the negative electrode cooled. Contact of the negative electrode 2 and the can 4 through heat conductive material of grease increases cooling effect since heat generating at the negative electrode becomes particularly easy to conduct to the can 4. Therefore capacity deterioration at the negative electrode can be suppressed.

Description

Detailed Description of the Invention (-r) Industrial Application Field The present invention uses an electrode provided with a hydrogen storage alloy having the ability to absorb and release hydrogen as a negative electrode, and an electrode provided with a metal oxide as a positive electrode. This invention relates to the structure of metal-hydrogen alkaline storage batteries such as nickel-hydrogen batteries.

(b) Conventional technology Lead-acid batteries and nickel-cadmium batteries have traditionally been commonly used storage batteries, but in recent years they have been developed to be lighter than these batteries and have the potential to have higher capacities, so negative electrodes have been developed, especially at low pressure. An electrode with a hydrogen storage alloy such as LaNi5 or CaNi5 that can reversibly absorb and release hydrogen as an active material is used as the negative electrode, and an electrode with a metal oxide such as nickel hydroxide as the positive electrode active material is used as the positive electrode. The metal-hydrogen alkaline storage battery used for this purpose is attracting attention. and,.

This hydrogen storage electrode comprising a metal hydride, which is a hydrogen storage alloy, is produced by sintering a hydrogen storage alloy powder together with a conductive material powder, as proposed in Japanese Patent Publication No. 58-46827. A method of producing a porous body and using it as a hydrogen storage electrode, or a method of bonding a hydrogen storage alloy powder and a conductive material powder with a binder as proposed in JP-A-53-103541. It is produced by a method that makes it a hydrogen storage electrode.

It is well known that the charging efficiency of the electrodes that make up a battery typically decreases when the temperature of the electrodes becomes high. However, in metal-hydrogen alkaline earth metals that use the hydrogen storage electrode as the negative electrode as described above, charging progresses by storing hydrogen, which is an active material, at the negative electrode, and the electrode plate capacity is determined by the absorption of hydrogen. Therefore, the higher the hydrogen storage capacity, the better, but since the reaction in which the hydrogen storage alloy stores hydrogen is an exothermic reaction, it has the disadvantage that the hydrogen storage capacity in particular decreases significantly at high temperatures. At the terminal stage or during high-temperature operation, sufficient hydrogen could not be absorbed and a satisfactory electrode plate capacity could not be obtained.

eX) Problems to be Solved by the Invention The present invention makes it possible to smoothly dissipate heat from the hydrogen storage electrode of the negative electrode, so that hydrogen can be sufficiently stored in the negative electrode even at the end of charging and during high-temperature operation, thereby preventing a decrease in capacity. It is something that we are trying to suppress.

2) Means for Solving the Problems The present invention provides a negative electrode equipped with a hydrogen storage alloy located on the outer surface of the electrode body, which is brought into contact with the inner surface of the battery outer can either directly or through a grease-like thermally conductive material. It is what it is.

) When a negative electrode equipped with a hydrogen storage alloy is placed on the outer surface of the working electrode body and this negative electrode is brought into contact with the inner surface of the battery outer can, the heat generated at the negative electrode is quickly transferred to the battery outer can number, and the battery outer can is heated. Heat can be radiated from the entire surface of the electrode, and temperature rise of the negative electrode can be suppressed.

(F) Example: LaNi5 having hydrogen storage capacity is mechanically crushed into a fine powder, and polytetrafluoroethylene powder, whose particles easily become fibers and plastically deform with a small shearing force, is added to the LaNi5 powder to reduce the weight of the LaNi5 powder. The polytetrafluoroethylene is added in an amount of 1 to 5% and mixed uniformly with a mixer, and the polytetrafluoroethylene is made into fibers. Next, water is added to the polytetrafluoroethylene fiber mixture to form a paste, which is then pasted on both sides of a nibkel plate to obtain a hydrogen storage electrode. The hydrogen storage electrode produced in this way has a discharge capacity of 1
It is wound around a 200 mAH sintered nickel positive electrode with a separator interposed therebetween to form a spiral electrode body in which the hydrogen storage electrode is located at the outermost periphery. This electrode body is inserted into a battery case made of nickel-plated iron, and the hydrogen storage electrode on the outermost periphery of the electrode body is brought into contact with the inner surface of the battery case. After that, an alkaline electrolyte is injected and the cap is sealed. Hydrogen battery (
Al was produced. FIG. 1 is a vertical cross-sectional view of this battery. The spiral electrode body is inserted into a battery exterior can made of nickel-plated iron with thermally conductive silicone grease arranged on the inner circumferential surface in advance, and the hydrogen storage electrode located on the outermost periphery of the electrode body and the battery exterior can are inserted. A mixture of the LaN i 5 powder and fibrous polytetrafluoroethylene is filled along the inner surface of the battery outer can, and this mixture is sealed inside the battery outer can. After contact with the inner surface, the four-part space of this filled mixture,
That is, a battery tc+ was prepared by filling the center of a battery outer can with a mixture consisting of a nickel active material, a conductive material, and a viscous agent via a separator. FIG. 2 shows the battery (B
), FIG. 3 is a vertical cross-sectional view of the battery (C1),
In the figure, (1) to (4) indicate components with the same symbols as shown in FIG. 1, (5) is a current collector rod, and (6) is a thermal
:Mini conductive silicone grease. Furthermore, for comparison, a comparative battery CD+ was prepared in which the nickel electrode was located on the outermost periphery of the electrode body in the same manner as in the battery thus prepared, and a battery in which the positions of the nickel electrode and the hydrogen electrode were reversed in the same manner as in battery (0) (El was Created.

FIG. 4 ("l and (bl are the above-mentioned batteries (AHBIpI
Figure 5 (al and (bl) shows the same measurement results as for the above-mentioned battery (C1fEl).

Note that the temperature of the negative electrode indicates the temperature when the negative electrode is charged to a shrine charge. From FIG. 4 (λ) and FIG. 5 (a), the batteries of the present invention (within the battery of the present invention) and Machi exhibited better characteristics than the comparative battery (1)1, and the battery of the present invention (C1 also exhibited better properties than the comparative battery (El). It can be seen that this shows that

Usually, metal hydrides, which are hydrogen storage alloys, generate heat when storing hydrogen, and have the property that hydrogen and coercive pressure increase at high temperatures.

Therefore, in order to advance the hydrogen storage reaction corresponding to charging reaction 1ζ, it is necessary to lower the temperature of the battery negative electrode. Therefore, in the comparative batteries (D+ and (E)), the positive electrode is located on the outer surface of the negative electrode, making it difficult for the heat generated at the negative electrode to escape, and the temperature of the negative electrode increases, resulting in a decrease in capacity. In contrast, the batteries of the present invention ^) (Bl and (C1) are shown in Fig. jI4 (bl and Fig. 5 f).
As is clear from bl, the temperature of the negative electrode is higher than the comparative battery IDI.
and (is kept lower than E+.

This is because the heat generated at the negative electrode during charging is transmitted from the negative electrode located on the outer surface of the electrode body to the metal battery case, and is quickly released from the surface of the battery case to cool the negative electrode. When the negative electrode and the battery case are brought into contact with each other through a grease-like thermally conductive substance, the heat of the negative electrode is particularly easily transferred to the battery case, resulting in a large cooling effect. It is thought that capacity deterioration was suppressed.Also, when charging and discharging are repeated, metallic hydrogen compounds become pulverized and heat tends to accumulate in the negative electrode, but as in the battery of the present invention, heat generated in the negative electrode is Batteries that can dissipate heat by quickly discharging heat can dissipate heat smoothly even after repeated charging and discharging, which is highly effective.

(G) Effects of the Invention The metal-hydrogen alkaline storage battery of the present invention has a negative electrode equipped with a hydrogen storage alloy located on the outer surface of the electrode body, which is attached directly to the inner surface of the metal battery outer case or through a grease-like thermally conductive material. Since they are in contact with each other, heat generated at the negative electrode during charging can be smoothly released to the outside of the battery, and a decrease in negative electrode capacity can be suppressed. In addition, in the battery of the present invention, it is preferable that the negative electrode be located on the outer metal surface of the electrode body that comes into contact with the battery outer can, but the same effect can be obtained even if the negative electrode is not placed at all positions in contact with the battery outer can. .

[Brief explanation of drawings]

Figures 1 to 3 are longitudinal sectional views of the battery of the present invention, and Figure 4 fa
t and FIG. 5 (2L) are drawings showing the negative electrode capacity with respect to the outside temperature of the battery of the present invention and the comparison battery, fJ4, fbl, and
Figure fb) is a diagram showing the temperature of the negative electrode with respect to the outside temperature of the battery of the present invention and the comparative battery. +11...Nickel electrode, +21...Hydrogen electrode, (31
... Separator, (4) ... Battery exterior can, (5).
... Current collector rod, (6) ... Thermal conductive silicon (D) CE) Congres, 4FBlfC1 ... Invention battery, Monthly
・Comparison battery.

Claims (1)

[Claims] (1) A battery comprising an electrode body configured with a separator interposed between a negative electrode and a positive electrode comprising a hydrogen storage alloy and housed in a metal battery case, the negative electrode being located on the outer surface of the electrode body. is in contact with the inner surface of the battery outer can directly or via a grease-like thermally conductive substance.