JPS6266569A - Cathode plate for alkaline storage battery - Google Patents

Abstract

PURPOSE:To retard the formation of gamma-nickel oxyhydroxide in charging to prevent decrease in the strength of electrode plate by containing calcium hydroxide on the surface of a plate containing nickel hydroxide as active material. CONSTITUTION:A sintered nickel hydroxide plate containing nickel hydroxide as active material is immersed in a calcium nitrate solution, then immersed in hot sodium hydroxide solution to contain calcium hydroxide on the surface of the plate. By using this cathode plate, an alkaline storage battery such as nickel-cadmium battery is formed. By adding cadmium hydroxide to only the surface of the plate, the formation of gamma-nickel oxyhydroxide in charging is retarded. Decrease in the strength of the plate caused by swelling and coming-off is prevented and capacity variation in charge-discharge cycling is reduced.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to an anode plate for an alkaline storage battery.
The present invention relates to anode plates used in alkaline storage batteries such as nickel-cadmium storage batteries.

<Prior art> As the anode plate of an alkaline storage battery such as a nickel-cadmium storage battery, a so-called nickel hydroxide electrode plate containing nickel hydroxide as an active material is used. Depending on various manufacturing methods, for example, in the case of a sintered nickel hydroxide electrode plate, nickel nitrate is retained in the micropores of a sintered substrate made of a porous nickel sintered body through a series of impregnation operations, and the retained nitric acid It is made by replacing nickel with the active material nickel hydroxide using a method such as alkali replacement.

<Problems to be Solved by the Invention> By the way, nickel hydroxide contained as an active material in a nickel hydroxide electrode plate normally becomes β-type nickel oxyhydroxide, which is a stable charging product, by charging. In overcharging or charging at a high current density, in addition to β-type nickel oxyhydroxide, γ-type nickel oxyhydroxide, which is unstable in production and existence, also comes to be produced.

Such γ-type nickel oxyhydroxide tends to swell during charging, and also tends to peel off from the electrode plate due to repeated expansion and contraction during charging and discharging cycles, which is one of the factors that deteriorates the cycle characteristics and life of the electrode plate. It has become. In addition, although γ-type nickel oxyhydroxide has a larger capacity ε than β-type nickel oxyhydroxide, it gradually changes to β-type nickel oxyhydroxide through repeated charging and discharging. There is a disadvantage that the initial fluency gradually decreases until about 25 cycles of the electrode plate. In particular, in a sintered nickel hydroxide electrode plate constructed using a sintered substrate, repeated cycles corrode the substrate and turn it into an active material, and this turning into an active material leads to an increase in capacity. The problem is that the capacity gradually decreases, and as the cycle progresses, the capacity increases, making the capacity unstable during the cycle and making it extremely difficult to balance it with a counter electrode such as a cadmium cathode. .

<Means for Solving the Problems> As a result of studies to solve the above problems, the present inventor found that when the following means is used, the generation of γ-type nickel hydroxide during charging can be suppressed to an extremely low level. The present invention was completed based on the knowledge that it was possible to achieve the intended purpose.

That is, the anode plate for an alkaline storage battery of the present invention is an electrode plate containing nickel hydroxide as an active material, and the gist thereof is that the surface of the electrode plate contains calcium hydroxide.

It should be noted that simply adding calcium hydroxide to a nickel hydroxide electrode plate is disclosed in Japanese Patent Publication No. 53-19086, for example.
This is known from the publication No. However, according to the research conducted by the present inventors, it has been found that by simply incorporating calcium hydroxide into the electrode plate, almost no effect of suppressing γ-type nickel hydroxide during charging can be expected; It has been found that significant effects can only be exhibited by incorporating it on the surface.

<Function> By using the above means, the generation of γ-type nickel oxyhydroxide during charging can be suppressed to the lowest possible level, and as a result, embrittlement such as swelling and peeling of the electrode plate due to repeated charging and discharging can be prevented. It can be prevented. In addition, since there is less γ-type nickel oxyhydroxide produced during charging, the capacity drop in the initial cycle is extremely small, and the degree of corrosion of the sintered substrate is also reduced because there is almost no swelling or peeling of the electrode plate. Therefore, the increase in capacity after the initial cycle is also extremely small.

<Example> A sintered substrate prepared by a known method was immersed in a nickel nitrate aqueous solution with a specific gravity of 1.75 at a temperature of 80°C, and then
A sintered nickel hydroxide electrode plate was prepared by repeating a series of impregnation operations five times in which the electrode plate was immersed in a 5% caustic powder solution to form an active material.

This electrode plate was immersed in a calcium nitrate solution with a ratio of 1.3, and then immersed in 25% caustic soda at a temperature of 80'C to contain calcium hydroxide on the electrode plate surface. A nickel electrode plate was obtained. This electrode plate was combined with a known cadmium electrode plate, and a nickel-cadmium storage battery (product A of the present invention) having a nominal capacity of about 1400 mAH was made using pure caustic soda as an electrolyte.

In addition, for comparison, calcium hydroxide was incorporated into the electrode plate by performing the same series of active material impregnation operations using the same nickel nitrate aqueous solution except that 1.5% by weight of calcium nitrate was added. A nickel hydroxide plate was made and combined with a similar cadmium plate to make a nickel-cadmium storage battery (comparative quantity B). Furthermore, a nickel-cadmium storage battery (conventional product C) was made in which a similar cadmium electrode plate was combined with a nickel hydroxide electrode plate without addition of calcium hydroxide to the surface or inside of the electrode plate as described above.

Incidentally, the total amount of calcium hydroxide added to each of the nickel hydroxide electrode plates of the invention product A and the comparison amount B was made to be the same.

Regarding the three nickel-cadmium storage batteries mentioned above, cycle changes in discharge capacity were investigated when each charge/discharge cycle was performed. The results are shown in Figure 2. Inventive product A shows extremely little change in capacity throughout the cycle and has a long cycle life, whereas comparative product B and conventional product C
It can be seen that the capacity fluctuation during the cycle is large and the cycle life is short. This is thought to be because the amount of γ-type nickel oxyhydroxide produced in the nickel hydroxide electrode plate used in product A of the present invention was extremely small, and the weakening of the electrode plate during the cycle was suppressed to a low level.

Incidentally, in order to investigate the amount of γ-type nickel oxyhydroxide produced in each of the nickel hydroxide electrode plates used in these three storage batteries, X-ray diffraction was performed on the active materials in these three electrode plates. The results are shown in FIGS. 1(A) to (C). still,
Figure 1 (A) is the X-ray diffraction diagram of the nickel hydroxide electrode plate used in the invention product A, Figure 1 CB), and (C) are the comparative amounts B, respectively.
, is an X-ray diffraction diagram of the nickel hydroxide electrode plate used in Conventional Product C. From these figures, the electrode plate according to the present invention has a significantly smaller amount of γ-type nickel oxyhydroxide (γ-NiOOH) produced, and a corresponding amount of β-type nickel oxyhydroxide (β-NiOOH).
It can be seen that the amount of I-1) produced is large. Furthermore, as is clear from the comparison between Figure 1 (8) and (B), there is a difference in the effect of suppressing the formation of γ-type nickel oxyhydroxide even though the amount of calcium hydroxide added to the electrode plate remains the same. This is because the suppressing effect varies significantly depending on the position where calcium hydroxide is added, and although the detailed reason is not clear, a reliable and significant suppressing effect can only be obtained by adding calcium hydroxide to the surface of the electrode plate.

<Effects of the Invention> According to the anode plate for an alkaline storage battery of the present invention configured as described above, the addition of calcium hydroxide to the surface of the plate prevents the plate from weakening during charging and discharging, and
This has the effect of minimizing the change in capacity during charge/discharge cycles and contributing to improving the cycle characteristics of the storage battery.

[Brief explanation of drawings]

Figures 1 (A) to (C) are X-ray diffraction diagrams of the active material in the electrode plate according to the present invention, and Figure 2 is the X-ray diffraction diagram of the active material in the electrode plate according to the present invention or the conventional electrode plate. This is a graph showing the cycle characteristics of a nickel-cadmium storage battery.

Claims (1)

[Claims] 1. An anode plate for an alkaline storage battery, which is an electrode plate containing nickel hydroxide as an active material, and is characterized by containing calcium hydroxide on the surface of the electrode plate.