JPS59169065A - Alkaline zinc storage battery - Google Patents

Abstract

PURPOSE:To prevent the deformation of an electrode plate and extend the cycle life for a long time by making the active material filling quantity of a zinc electrode larger at the electrode plate peripheries than at the center of the electrode plate and also making the thickness nearly the same at the peripheries and the center. CONSTITUTION:The first sheets 5 are arranged at both sides of a current collector made of copper, etc. and also the second sheets 6 are arranged over the peripheries 7 of the first sheets 5, then they are molded by pressure so that the thickness is made nearly the same at the peripheries and at the center, and it is dried to form a zinc electrode. Accordingly, the deformation of an electrode plate at its peripheries can be reduced and also the cycle life for a long time can be extended.

Description

DETAILED DESCRIPTION OF THE INVENTION (-r) Industrial Application Field The present invention relates to alkaline zinc storage batteries that use zinc as a negative electrode active material, such as nickel-zinc storage batteries and silver-zinc storage batteries.

(b) Prior Art Zinc as a negative electrode active material has the advantages of high energy density per unit weight and low cost, but on the other hand, zinc dissolves into the alkaline electrolyte during discharge and becomes zincate ions.
During charging, the zincate ions are deposited on the back surface of the zinc electrode in a tree-like or spongy form, so when charging and discharging are repeated, the deposited zinc penetrates the separator and comes into contact with the counter electrode, causing an internal short circuit. The disadvantage is that it has a short lifespan.

In order to improve this cycle life, the cycle life can be considerably improved by regulating the amount of electrolyte to prevent diffusion of zincate ions and using a plurality of organic or inorganic separators. However, once dissolved as zincate ions during discharging, zinc is rarely deposited at its original position during charging, so if charging and discharging are repeated, the deformation of the zinc electrode plate becomes significant, leading to a decrease in capacity. It could no longer withstand long-term charging and discharging.

The plate deformation of the zinc electrode is most significant at the periphery of the plate. In order to prevent the deformation of the electrode plate at the peripheral edge of the electrode plate, as shown in FIG. ) was further pressed to improve its mechanical strength.

This prevents deterioration of the electrode plate due to shedding of the zinc active material, and reduces the porosity of the active material at the edge of the electrode plate, thereby regulating the amount of electrolyte and causing the zinc active material to elute as salivate ions. This prevents deformation at the peripheral edge of the electrode plate. Furthermore, by pressing the peripheral edge of the electrode plate, damage to the peripheral edge of the electrode plate can be prevented during the manufacturing process, and the defect rate of completed storage batteries can also be reduced.

However, it has been found that even if the peripheral edge of the zinc electrode is pressed, it cannot withstand charging and discharging over a longer period of time. That is, in order to press the periphery of the zinc electrode plate,
The peripheral edge of the electrode plate is thinner than the center of the plate, and when a storage battery is assembled by combining such a zinc electrode with a positive electrode via a separator, a space is formed near the peripheral edge of the zinc electrode, and this space Electrolyte tends to accumulate in the area. This causes non-uniform distribution of the electrolyte, and even though the amount of electrolyte is originally regulated, a large amount of electrolyte is present at the periphery of the zinc electrode plate, and the zinc active material is It was eluted as acid ions, and deformation of the electrode plate could not be prevented.

(c) Purpose of the Invention The present invention has been invented in view of the above points, and focuses on the fact that the plate deformation of a lead electrode starts from the plate periphery. The purpose of this invention is to provide an alkaline zinc storage battery that can further reduce the deformation of the zinc electrode plate by changing the amount of active material filled in the central portion, and can withstand a longer cycle life.

B) Structure of the Invention In order to achieve the above object, the alkaline zinc storage battery according to the present invention has an electrode plate containing zinc and zinc oxide as active materials, and the amount of active material filling in the peripheral part of the electrode plate is smaller than that in the center part of the plate. It is constructed with a zinc electrode which is large in size and has approximately the same thickness at the periphery of the plate and at the center of the plate.

(E) Example Hereinafter, an example of the present invention will be described, and a comparison with a comparative example will be mentioned.

〔Example〕

After adding water to a mixed powder consisting of 5% by weight of fluororesin powder and kneading, the mixture was pressurized with rollers to form a powder of 50 m long + 4 m wide.
A first sheet of 0 mm was created.

A frame-shaped second sheet was prepared on the same side as this first sheet, and had vertical bars with a width of 4 m and horizontal bars with a width of 5 m.

Once the first sheet is placed, a second sheet is placed on the periphery of the first sheet, pressure molded so that the thickness of the periphery and the center are approximately the same, and dried to create a zinc electrode. did. Second
The figure is a front view of this zinc electrode, and FIG. 3 is a sectional view taken along the line mm in FIG. 2. In these drawings, (5) is the first sea)
, is) is the second sheet and overlaps the peripheral edge (7) of the first sheet (5). FIG. 3 schematically shows this overlapping state. (8) is a current collector, and (9) is a current collector lead portion.

A square nickel-zinc storage battery (A) was prepared by combining the zinc electrode obtained as described above and a known sintered nickel electrode.

[Comparative Example 1] For comparison, only the first sheet of the example was attached to the current collector of the example to create a zinc electrode having the same external shape and thickness as the example. A comparative cell (container) was prepared which was otherwise the same as in the example except for the following.

[Comparative Example 2] A zinc electrode obtained by pressing the peripheral edges of the zinc electrode obtained in Comparative Example 1, that is, the frame-shaped portions of 4 pieces on the left and right sides and 5 pieces on the top and bottom edges, to a thickness approximately equal to that of the other parts. A comparative battery (C) was produced which was the same as the example except that this zinc electrode was used. The packing density of the zinc active material in the peripheral press area of the zinc electrode used in this comparative battery (9 traps) is the filling density of the zinc active material in the overlapping part of the first and second sheets at the peripheral edge of the zinc electrode used in the example. The density is approximately the same as that of the zinc active material, and is approximately twice the packing density of the zinc active material in the center of the zinc electrode.

[Comparison]

Figure 2 shows a storage battery according to the present invention) and a comparison battery) (C)
The cycle characteristic diagram shows the initial capacity of the storage battery at 100%.
Shown as Symbols in FIG. 2 indicate cycle characteristics of storage batteries with the same symbol. The cycle conditions were to charge at 150mA for 5 hours and then discharge at 1501nA until the battery voltage was 1.27.
The discharge will stop when the temperature reaches . As is clear from this figure, the storage battery (A) according to the present invention is different from the comparative battery (
B) (C) It can be seen that the cycle life is improved compared to K.

There are three possible reasons for this: That is, firstly,
In the zinc electrode of the example, since the thickness of the central part of the plate and the thickness of the peripheral part of the plate are approximately the same, a space is often formed between the peripheral part of the plate and the positive electrode when assembling a storage battery. Therefore, the electrolyte is less likely to accumulate on the periphery of the electrode plate. Second, in the zinc electrode of the example, the peripheral edge of the electrode plate is the first sheet (5) and the second sheet (5).
6), the porosity is reduced from the central part of the electrode plate consisting only of the first sheet (5), and penetration of the electrolyte is restricted. Thirdly, in the zinc electrode of the example, the amount of zinc active material filled in the peripheral portion of the electrode plate is larger than the amount of zinc active material filled in the center portion of the electrode plate, so even if the zinc active material in the peripheral portion of the electrode plate is Even if it is eluted as ions, the zinc active material at the periphery of the electrode plate becomes difficult to elute, and as in comparative batteries (B) and (C), the charging and discharging efficiency decreases due to gas generation from the periphery of the zinc electrode plate. Alternatively, the storage battery is less likely to be destroyed by gas pressure.

Accordingly, in the present invention, as a method of increasing the filling amount of the zinc active material in the peripheral portion of the electrode plate of the zinc electrode, the zinc concentration in the zinc active material may be particularly increased. As a method for producing the zinc electrode, the content of zinc powder at the periphery of the electrode plate may be increased, or the content of zinc powder in the second sheet (6) in the example may be increased. Increasing the zinc content at the periphery of the electrode plate in this way creates a large amount of zinc that can become the nucleus of electrodeposition during charging, so electrodeposition occurs smoothly and improves charging and discharging efficiency. There are also possible benefits.

In addition, in the embodiment, the width of the second sheet is set to 100 mm, which is the width of the electrode plate, but it is conceivable that the width of the second sheet is set to 100 mm or T depending on the shape of the electrode plate. The applicability is clear.

(F) Effects of the Invention As described above, the present invention provides an electrode plate using zinc and zinc oxide as active materials, in which the amount of active material filled in the peripheral portion of the electrode plate is larger than that in the central portion of the electrode plate, and Since it is equipped with a zinc electrode with approximately the same thickness at the center of the electrode plate, there is less deformation of the electrode plate at the periphery of the zinc electrode than in comparison batteries, and a longer cycle life is achieved. It is possible to provide an alkaline zinc storage battery that can withstand

[Brief Description of the Drawings] Fig. 1 is a cross-sectional view of a conventional zinc electrode, Fig. 2 is a front view of a zinc electrode according to an embodiment of the present invention, and Fig. 3 is a cross-sectional view taken along line mm in Fig. 2. FIG. 4 is a cycle characteristic diagram of the storage battery according to the example and the comparative battery.

Claims (1)

[Claims] fil An electrode plate using zinc and zinc oxide as active materials, in which the amount of active material filled at the peripheral edge of the plate is larger than that at the center of the plate, and the thickness of the peripheral edge and the center of the plate are approximately the same. Alkaline zinc storage battery with zinc electrodes.