JPH0722028A - Sealed alkaline zinc storage battery - Google Patents

Abstract

PURPOSE:To prevent a shape change and enhance a charge/discharge cycle life by providing a zinc negative electrode with pores of specific porosities, and arranging a separator in contact with this zinc negative electrode. CONSTITUTION:An electrode group wherein a separator 3 is interposed by liquid holding layers 41, 42 is inserted between a zinc negative electrode 1 and a positive electrode 2 to hold an electrolyte by the electrode group in a battery jar 6, and another separator 5 is provided on a surface of the zinc electrode 1. The zinc electrode 1 is composed of a negative electrode active material having porosities of 40 % or larger, and the positive electrode 2 is a sinter type nickel electrode. The separator 3 is a combination of a porous polypropylene separator and a cellophane separator, and the liquid holding layer is composed of cellulose non-woven fabric. In the separator 5, a cellophane film is coated with a surface active agent.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sealed alkaline zinc storage battery, and more particularly to improvement of the zinc negative electrode.

[0002]

2. Description of the Related Art In recent years, the demand for rechargeable secondary batteries has increased with the spread of portable type and cordless type electronic devices.

As such a secondary battery, attention has been paid to one having a high energy density and easy maintenance as the size and weight of the device are reduced, and in particular, a sealed alkaline zinc storage battery has been attracting attention.

Since the zinc negative electrode in the above-mentioned sealed alkaline zinc storage battery has a high solubility of zinc as a negative electrode active material, it reacts such that the negative electrode active material is dissolved or deposited during the process of discharging or charging, and It is known that phenomena such as shape change and dendrite short circuit occur on the negative electrode.

Conventionally, in order to suppress the occurrence of such shape change and dendrite short circuit, a microporous alkali resistant resin film or cellophane is used as a separator.
It has been proposed that this separator be sandwiched between a cellulosic non-woven fabric or an alkali resistant resin non-woven fabric as a liquid retaining layer.

A conventional example of the above sealed alkaline zinc storage battery will be described with reference to FIG.

The battery shown in FIG. 2 has a zinc negative electrode 1 in which a negative electrode active material mainly containing zinc and zinc oxide is applied to both sides of a current collector made of copper punching metal. A positive electrode 2 made of sintered nickel mainly composed of is prepared from the inside, and the positive electrode 2 is a liquid retaining layer 42 made of nylon non-woven fabric, polypropylene non-woven fabric or cellulose non-woven fabric, a separator 3 made of microporous film, nylon non-woven fabric, and A liquid retaining layer 41 made of a propylene nonwoven fabric or a cellulose nonwoven fabric is surrounded in this order, and the zinc negative electrode 1 is interposed between the liquid retaining layer 41 and the liquid retaining layer 41 surrounding another positive electrode 2, Further, the zinc negative electrode 1 is laminated so as to be positioned, and is housed in the battery case 6 together with the electrolytic solution.

[0008]

The above-mentioned conventional sealed alkaline zinc storage battery has a problem that the negative electrode active material enters the liquid-retaining layer on the negative electrode side with the progress of charge / discharge cycles to cause shape change.

[0009]

In order to solve the above problems, the present invention provides a zinc negative electrode containing at least one of zinc oxide and metallic zinc as a main component, a positive electrode, and a zinc negative electrode and a positive electrode. In a sealed alkaline zinc storage battery having a pole group consisting of an inserted liquid retention layer and a separator, and having an electrolyte solution absorbed and retained in these pole groups,
The negative electrode active material is configured so that the zinc negative electrode has a porosity of 40% or more, and a separator is arranged so as to be in contact with the zinc negative electrode.

[0010]

Therefore, according to the present invention, since the negative electrode active material is constructed so that the zinc negative electrode has a porosity of 40% or more, the zinc negative electrode has 40% or more of holes for holding the electrolytic solution. It can be ensured, and the reaction of the zinc negative electrode during discharge is not limited by the lack of electrolyte.

Further, according to the present invention, since the separator is disposed in contact with the zinc negative electrode, the negative electrode active material does not enter the liquid retaining layer on the negative electrode side.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG.

The sealed alkaline zinc storage battery of the present invention shown in FIG. 1 comprises 20% by weight of metallic zinc powder and 8% zinc oxide powder.
0 wt% and polytetrafluoroethylene used as a binder to obtain a thickness of 1 mm and a porosity of 30% to
Prepared are four 60% zinc negative electrodes 1 and three positive electrode 2 composed of a sinter type nickel electrode, and a separator 3 in which a microporous polypropylene separator and a cellophane separator are combined between the zinc negative electrode 1 and the positive electrode 2. Is sandwiched between the liquid-retaining layers 41 and 42 made of a cellulosic non-woven fabric, and a specific gravity is 1.10 to 1.35 g / cc.
This is obtained by holding an electrolytic solution in which lithium hydroxide is dissolved in an aqueous potassium hydroxide solution, and its capacity is 7 Ah. In addition, the zinc negative electrode 1 of this sealed alkaline zinc storage battery
A microporous polyethylene separator or cellophane film having a thickness of 25 μm, which is coated with a surfactant, is arranged on the surface of the separator 5 as a separator 5.

In contrast to such a sealed alkaline zinc storage battery of the present invention, a conventional sealed alkaline zinc storage battery in which the surface of the zinc negative electrode 1 is in direct contact with the liquid retaining layer 41 was produced.

For each of the sealed alkaline zinc storage batteries described above, in an atmosphere of 25 ° C., at a charging current of 0.1 C
After charging for 5 hours, the discharge capacity when discharged to 1 V per cell with a discharge current of 1 C was investigated, and the results are summarized in Table 1. The discharge capacity is represented by the ratio of the initial capacity to 7 Ah.

[0016]

[Table 1]

From Table 1, when the porosity of the zinc negative electrode 1 is 40% or less, the amount of the electrolytic solution retained in the zinc negative electrode 1 becomes small, so that the reaction of the zinc negative electrode 1 during discharging is rate-determined. It can be seen that the discharge capacity is reduced.

Next, a zinc negative electrode 1 having a porosity of 50% was used, and a microporous alkali-resistant resin film or cellophane film was arranged as a separator 5 on the surface of the zinc negative electrode 1, and the capacity of the present invention was 7 Ah. Of the sealed alkaline zinc zinc storage battery and the conventional sealed alkaline zinc storage battery in which the surface of the zinc negative electrode 1 is in direct contact with the liquid retaining layer 4 in an atmosphere of 25 ° C. and a charging current of 1C of 10.5. After charging for a long time, a charging / discharging cycle of discharging 1V per cell with a discharging current of 1C is continuously performed, and the number of charging / discharging cycles when the discharge capacity reaches 60% at a ratio of 7Ah is summarized in Table 2. Is.

[0019]

[Table 2]

From Table 2, it is understood that the battery of the present invention can improve the number of charge / discharge cycles as compared with the conventional battery.

In the sealed alkaline zinc storage battery described above, a microporous alkali resistant resin film or cellophane film is arranged as the separator 5 on the surface of the zinc negative electrode 1, but a polyethylene separator grafted or other fine particles are used. The same effect can be expected by disposing a porous alkali-resistant resin film on the surface of the zinc negative electrode 1.

[0022]

As described above, according to the present invention, since the amount of the electrolytic solution held in the zinc negative electrode is increased, the reaction of the zinc negative electrode is not rate-determined during discharging.

Further, since the separator is disposed in contact with the zinc negative electrode, it is possible to suppress the movement of zincate ions and thereby suppress the occurrence of shape change, and to improve the charge / discharge cycle life of the sealed alkaline zinc storage battery. Can be improved.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a sealed alkaline zinc storage battery of the present invention.

FIG. 2 is a cross-sectional view of a conventional sealed alkaline zinc storage battery.

[Explanation of symbols]

 1 Zinc negative electrode 2 Positive electrode 3 Separator 4 Liquid retaining layer 5 Separator 6 Battery case

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Kenkichi Fujii 6-6 Josaimachi, Takatsuki City, Osaka Prefecture Yuasa Corporation

Claims (3)

[Claims] 1. A polar group comprising a zinc negative electrode containing at least one of zinc oxide and metallic zinc as a main component, a positive electrode, and a liquid retaining layer and a separator interposed between the zinc negative electrode and the positive electrode. And in a sealed alkaline zinc storage battery having an electrolyte solution absorbed and retained in these pole groups,
A sealed alkaline zinc storage battery, characterized in that a negative electrode active material is constituted so that the zinc negative electrode has a porosity of 40% or more, and a separator is arranged so as to be in contact with the zinc negative electrode. 2. The sealed alkaline zinc storage battery according to claim 1, wherein a microporous film made of an alkali resistant resin is used as the separator in contact with the zinc negative electrode. 3. The sealed alkaline zinc storage battery according to claim 1, wherein a cellophane film is used as a separator in contact with the zinc negative electrode.