JPH07254410A - Zinc alkaline secondary battery - Google Patents

Abstract

PURPOSE:To elongate cycle life by supplying electrolyte through nonwoven fabric A provided on the surface of a positive and a negative electrodes, and supplying for a reduced part of the electrolyte by electrode reaction through nonwoven fabric B provided in contact with the nonwoven fabric A under the electrodes. CONSTITUTION:Mix comprising zinc oxide powder by 70 weight %, zinc powder by 25 weight %, and fluorine resin binder by 5% is kneaded, and it is rolled 0.8mm thick to obtain a sheet of negative electrode active material. In this active material, a mesh collector of copper coated with lead is embedded to form a zinc electrode 1, and nonwoven fabric 4 of cellulose, and a micro-pole film separator 3 of polylene are provided like bags around the electrode 1 respectively. In the meanwhile, a nickel electrode 2 is covered with the nonwoven fabric 4 similarly, it is slightly pressed to both sides of the electrode 1 to be fixed, and it is inserted into a case having the nonwoven fabric 4 for holding electrolyte at a bottom. Battery electrolyte is then injected into the case until the nonwoven fabric 4 at the case bottom part is immersed. Form change of the electrodes during long use of a battery can thus be restricted, and its service life can be elongated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a zinc-alkaline secondary battery, such as a nickel-zinc battery or an air-zinc battery, which uses zinc as a negative electrode active material and an alkaline aqueous solution as an electrolytic solution.

[0002]

2. Description of the Related Art Conventionally, alkaline batteries using zinc as a negative electrode active material have a high energy density and are inexpensive.
Moreover, it is attracting attention as a battery for an electric vehicle because it has excellent operating characteristics in a low temperature range as compared with a lead storage battery.

On the other hand, however, zinc oxide (ZnO) produced during discharge dissolves in the electrolyte as zincate ions (Zn (OH) ₄ ²⁻ ) and precipitates as non-uniform metallic zinc during charge, resulting in charge / discharge cycle The electrode shape changes with repetition, and in extreme cases, there is a drawback that zinc grown in a dendritic manner penetrates the separator to reach the positive electrode, causing an internal short circuit.

In order to prevent this dendrite growth, a polyethylene or polypropylene porous film having pores of several tens to several hundreds of angstroms between the positive and negative electrodes is processed into a bag shape, and the positive and negative electrodes are inserted therein. Is a general countermeasure.

Although this method can be improved to some extent, it cannot completely avoid the permeation of zinc dendrite through the porous membrane due to repeated cycles, and a drastic countermeasure cannot be obtained.

Further, attempts have been made to circulate the electrolytic solution with an external pump or the like to suppress the generation of dendrites, but the battery itself becomes large and cannot be applied to electric vehicles and the cost increases. Such a problem occurred.

In order to solve this problem, a so-called sealed type battery is commercially available, which is a sealed type in which a small amount of electrolytic solution is impregnated into a non-woven fabric, but the electrolytic solution is consumed due to electrode reaction with repeated charging and discharging. Electrolyte evaporates due to heat of reaction
Finally, the passivation reaction of the electrode occurs due to the decrease, and the capacity is remarkably decreased, so that the product cannot be put to practical use.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and by supplying the electrolytic solution through a non-woven fabric such as cellulose, the flow of the electrolytic solution can be minimized. The purpose of the present invention is to improve the cycle life of a zinc electrode by suppressing the diffusion of dissolved Zn (OH) ₄ ²⁻ ions and efficiently replenishing an electrolyte solution that decreases with charge and discharge. .

[0009]

The present invention provides an alkaline zinc battery comprising a positive electrode, a separator disposed between a negative electrode using zinc as an active material, and a positive and negative electrodes, and an electrolyte solution. Alkaline zinc battery, characterized in that a non-woven fabric is installed, and an electrolyte is supplied through the Is.

[0010]

[Function] The charge / discharge reaction of the zinc electrode is expressed by the following equation.

[0011]

Embedded image Zn (OH) ₄ ²⁻ + 2e ⁻ = ZnO + 2OH ⁻ + H ₂ O

[0012]

Embedded image Zn + 4OH ⁻ = Zn (OH) ₄ ²⁻ + 2e ⁻

The discharge product, zincate ions (Zn
The specific gravity of the electrolytic solution having a high (OH) ₄ ^2- ) concentration is large and moves to the lower side of the battery as it is, but by installing a non-woven fabric such as cellulose on the electrode surface and supplying the electrolytic solution through it. The diffusion of Zn (OH) ₄ ²⁻ ions can be suppressed, and dendrite growth or electrode shape change during charging can be efficiently prevented.

Further, the electrolytic solution reduced by the electrode reaction or the exothermic reaction due to charging / discharging is replenished from the non-woven fabric placed on the lower part of the electrode to the non-woven fabric placed on the electrode surface by utilizing the capillary phenomenon, which is highly active. The zinc electrode can be maintained for a long time, and as a result, an unprecedented long-life alkaline zinc battery can be realized.

[0015]

Example 1 FIG. 1 shows a structural diagram of a nickel-zinc battery according to the present invention. Zinc oxide powder 70% by weight, zinc powder 25
After kneading a mixture consisting of 5% by weight and a fluororesin binder of 5%, and then using a rolling roll, a negative electrode active material rolled into a sheet having a thickness of 0.8 mm was embedded with lead-coated copper net current collector zinc. The electrode 1 was used.

A cellulosic non-woven fabric 4 was placed around the electrode in a bag shape and then covered with a polypropylene microporous membrane separator (trade name: Celgard) 3 in a bag shape to be used as a zinc electrode.

On the other hand, the nickel electrode 2 was likewise covered with a non-woven cloth in a bag shape, placed on both sides of the zinc electrode, and then fixed by a vinyl chloride holder so as to lightly press both.

Then, the combined electrode was put in a battery case, and a non-woven fabric for holding a replenishing electrolyte was placed at the bottom of the case.

Finally, a battery electrolyte was prepared by adding an aqueous solution containing 30% by weight of potassium hydroxide and 1% by weight of lithium hydroxide to a height at which the nonwoven fabric at the bottom of the case was immersed. Hereinafter, the battery thus created will be referred to as a battery A.

[0020]

Second Embodiment FIG. 2 shows a second embodiment as a modification of the first embodiment. Same as Example 1 except that a separate chamber 5 capable of replenishing the electrolytic solution is installed on the side surface of the battery case, and a further large amount of electrolytic solution can be replenished through the non-woven cloth for replenishing the electrolytic solution installed at the bottom of the case. The battery having the above structure and thus prepared is called a B battery.

[0021]

COMPARATIVE EXAMPLE A battery was prepared in the same manner as in Example 2 except that the whole electrode was immersed in the electrolytic solution 6 instead of supplying the electrolytic solution through the non-woven fabric placed on the positive and negative electrode surfaces. Hereinafter, the battery thus created will be referred to as a C battery.

As shown in FIG. 4, the electrolyte is supplied through a non-woven fabric placed on the surface of the positive and negative electrodes, but has no mechanism for replenishing the decrease in the electrolyte due to charging and discharging, a so-called sealed battery. Is called D battery.

Further, as shown in FIG. 5, a battery in which the D battery is immersed in a small amount of electrolyte for replenishing the reduced electrolyte is called an E battery.

FIG. 6 shows charge-discharge cycle characteristics of a nickel-zinc battery, where A is the A battery having the structure of Example 1 of the present invention,
B is the B battery having the structure of Example 2 of the present invention, C is the C battery of the comparative example, D is the D battery of the comparative example, and E is the E battery of the comparative example.

The initial capacity of each battery was 30 Ah, the current was 4.5 A, the terminal voltage was 2.0 V, and the current was 10
The cycle of discharging the terminal voltage at A to 1.0 V was repeated.

[0026]

As is apparent from the figure, the electrolyte solution is supplied through the non-woven fabric so that the decrease in the electrolyte solution due to the electrode reaction can be replenished.
Penetration of the zinc dendrite into the nickel electrode due to diffusion, and complete prevention of electrode shape change that occurs with repeated charge and discharge cycles, and since the reduced electrolyte can be efficiently replenished while suppressing the diffusion of zincate ions, It has become possible to manufacture an alkaline zinc battery in which the utilization rate of the zinc active material does not decrease.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an alkaline zinc battery of Example 1.

FIG. 2 is a cross-sectional view of an alkaline zinc battery of Example 2.

FIG. 3 is a sectional view of an alkaline zinc battery of Comparative Example C.

FIG. 4 is a sectional view of an alkaline zinc battery of Comparative Example D.

5 is a sectional view of an alkaline zinc battery of Comparative Example E. FIG.

FIG. 6 is a charge / discharge cycle characteristic diagram of the alkaline zinc battery of the present invention.

[Explanation of symbols]

 1 Zinc Electrode 2 Nickel Electrode 3 Separator 4 Nonwoven 5 Electrolyte Supply Separate Room 6 Electrolyte A A Battery according to Example 1 B Battery according to Example 2 C Comparative Example c D Comparative Example d E Comparative Example e

Claims (2)

[Claims] 1. In an alkaline zinc battery comprising a positive electrode, a separator provided between a negative electrode using zinc as an active material and a positive and negative electrodes, and an electrolyte solution, a non-woven fabric or the like is provided on the positive and negative electrode surfaces, and an electrolyte is provided therethrough. The alkaline zinc battery is characterized in that a reduced amount of the electrolytic solution due to the electrode reaction is supplied through a non-woven fabric arranged so as to contact the non-woven fabric at the lower part of the electrode. 2. The alkaline zinc battery according to claim 1, comprising a separate chamber for supplying the electrolytic solution to the lower nonwoven fabric.