JPH07161375A - Sealed alkaline zinc storage battery - Google Patents

Abstract

PURPOSE:To provide a sealed alkaline zinc storage battery in which dendrite growth of zinc at charging time can be suppressed and whose charging and discharging cycle life can be prolonged. CONSTITUTION:Crystal growth of metal zinc, which tends to grow as dendrite, is suppressed by surrounding the crystal of metal zinc by fatty acid ester which has a sorbitan skeleton with 12 or less HLB value and is added to electrode groups. Consequently, since the metal zinc crystal which tends to grow as dendrite can be surrounded, dendrite growth of the crystal at the charging time can be suppressed and a charging and discharging cycle life can be extended.

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 a sealed alkaline zinc storage battery capable of suppressing the growth of zinc dendrites during charging.

[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.

Such secondary batteries have attracted attention because of their high energy density and easy maintenance due to the downsizing and weight reduction of equipment, and particularly the sealed nickel-zinc storage batteries.

The zinc negative electrode in the above-mentioned sealed nickel-zinc storage battery has a problem that the dendrite of zinc grows during charging due to the high solubility of zinc to cause a short circuit through the separator, resulting in a short charge / discharge cycle life. Was the cause.

Conventionally, in order to prevent the generation of such dendrites, it has been proposed to use a microporous polyethylene membrane subjected to a hydrophilization treatment as a separator. The hydrophilization treatment causes migration of zincate ions. Attempts have been made to improve the gas flow rate and the oxygen gas transfer through the micropores.

[0006]

In the above-mentioned conventional sealed nickel-zinc storage battery, the oxygen gas can move well through the fine pores, but zinc is deposited in the fine pores to grow dendrites, which causes a short circuit. However, the generation of dendrites has not been completely prevented.

[0007]

In order to solve the above problems, the present invention has a zinc negative electrode containing zinc oxide and metallic zinc as main components, a positive electrode, and the zinc negative electrode and the positive electrode. A liquid-retaining layer and a separator, and in a sealed alkaline zinc storage battery formed by laminating an electrode group having an electrolyte solution impregnated in the liquid-retaining layer and the separator, in the electrode group is a water-soluble index of the surfactant. Aru Hydrophilic h-Lipo
It is characterized in that a fatty acid ester having a sorbitan skeleton having a phlic-balance (hereinafter referred to as HLB value) of 12 or less is added.

[0008]

[Operation] Therefore, according to the present invention, the crystal of metallic zinc to be grown by dendrite is surrounded by the fatty acid ester having a sorbitan skeleton, so that the growth of the crystal can be suppressed. Further, the HLB value of the fatty acid ester having the sorbitan skeleton can be controlled by the size and type of the polyoxyethylene group and the size and type of the fatty acid ester, so that the dendrite growth of metallic zinc can be performed without increasing the viscosity of the electrolytic solution. Can be suppressed.

[0009]

EXAMPLES The details of the present invention will be described below with reference to examples of sealed nickel-zinc storage batteries.

Examples of the fatty acid ester having a sorbitan skeleton to be added to the above-mentioned sealed nickel-zinc storage battery electrode group include polyoxyethylene sorbitan oleate,
Polyoxyethylene sorbitan laurate, polyoxyethylene sorbitan stearate and polyoxyethylene sorbitan palmitate are preferred.

Then, as a sealed nickel-zinc storage battery for adding the fatty acid ester having the sorbitan skeleton, a binder is added to a negative electrode active material composed of 80% by weight of zinc oxide powder and 20% by weight of metallic zinc powder. 1m thick with mixed polytetrafluoroethylene
Zinc negative electrode 4 having m and density of 2.5 to 3.0 g / cm ^3.
1 sheet and 3 sheets of a sinter-type nickel positive electrode are prepared, a liquid holding layer made of polypropylene nonwoven fabric and a separator made of a microporous polypropylene film are inserted between the zinc negative electrode and the nickel positive electrode, and The specific gravity obtained by adding lithium hydroxide to the liquid layer and the separator is 1.10 to
An aqueous solution of 1.35 potassium hydroxide was impregnated as an electrolytic solution to produce a battery having a capacity of 7 Ah.

Next, the above fatty acid ester having a sorbitan acid skeleton was added to the electrolytic solution of the sealed nickel-zinc battery with various HLB values, and the mixture was added at 25 ° C.
After charging at 0.1C for 10.5 hours in an atmosphere,
The initial capacity when discharged at 1 C until the voltage became 1 V / cell was investigated, and the results are shown in Table 1.

[0013]

[Table 1]

It can be seen from Table 1 that the initial capacity of any fatty acid ester having a sorbitan skeleton decreases when its HLB value is 12 or more. This is H
It is considered that when the LB value increases, the viscosity of the electrolytic solution increases, the utilization rate of the zinc negative electrode or the nickel positive electrode decreases, and the resistance of the electrolytic solution increases.

Next, the above fatty acid ester having a sorbitan skeleton was added to the electrolyte of the sealed nickel-zinc storage battery, the zinc negative electrode and the liquid retaining layer by varying the HLB value, and the atmosphere was maintained at 60 ° C. A charging / discharging cycle test in which the battery was charged at 0.3 C and then discharged at 1 C was conducted, and the number of cycles when the discharge capacity dropped to 4.2 Ah was investigated. The results are shown in Table 2.

[0016]

[Table 2]

It can be seen from Table 2 that the number of cycles of any fatty acid ester having a sorbitan skeleton decreases when its HLB value is 12 or more. Further, when the fatty acid ester having the sorbitan skeleton is added to the electrolytic solution, the solubility is small, so that a sufficient effect is not obtained in terms of improving the number of cycles, but it is added to the zinc negative electrode or the liquid retaining layer. Then, the number of cycles can be greatly improved. This is because the zinc negative electrode or the liquid-retaining layer can be added in a larger amount than the electrolytic solution, and the influence thereof is small even if the amount is decreased by decomposition.

Next, among the above sealed nickel-zinc storage batteries, the one having polyoxyethylene sorbitan monooleate having an HLB value of 10 and having the largest cycle number was added to the liquid retaining layer at 25 ° C. A charge-discharge cycle test of charging at 0.1 C in the atmosphere and then discharging at 1 C was conducted, and when the number of cycles when the discharge capacity dropped to 4.2 Ah was investigated, it was 420 cycles. Further, the same charge / discharge cycle test was conducted on the conventional battery to which nothing was added to examine the number of cycles, and it was 300 cycles.

Although the above examples relate to the sealed nickel-zinc storage battery, the HLB value of the fatty acid ester having the sorbitan skeleton to be added is also in the sealed alkaline zinc storage battery using a positive electrode other than the nickel positive electrode. Since the size and type of the polyoxyethylene group and the size and type of the fatty acid ester can be controlled as appropriate, the control can be performed in the same manner as in the above-mentioned examples.

[0020]

As described above, the sealed alkaline zinc storage battery of the present invention can reduce the decrease in initial capacity and improve the charge / discharge cycle life.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Kenkichi Fujii, 6-6 Josaimachi, Takatsuki-shi, Osaka Prefecture Yuasa Corporation (72) Mitsuo Yamane 6-6, Josaimachi, Takatsuki, Osaka Yu, Ltd. In Asa Corporation (72) Inventor Noriko Matoba 2-6-1, Nishi-Nagasu-cho, Amagasaki-shi, Hyogo Inside Nard Institute Co., Ltd. (72) Inventor Nobuhiro Nakajima 2-6-1-1, Nishi-Nagasu-cho, Amagasaki-shi, Hyogo Incorporated company Nard Institute (72) Inventor Satoru Riki Satoshi Watanabe 2-chome, Chuo-ku, Fukuoka-shi, Fukuoka Prefecture Kyushu Electric Power Co., Inc. (72) Inventor Kazuyuki Adachi Douji Watanabe, Chuo-ku, Fukuoka-shi, Fukuoka 1-82, Kyushu Electric Power Co., Inc.

Claims (4)

[Claims] 1. A zinc negative electrode containing zinc oxide and metallic zinc as main components, a positive electrode, a liquid retention layer and a separator interposed between the zinc negative electrode and the positive electrode, and the liquid retention layer and the separator impregnated. In a sealed alkaline zinc storage battery comprising a stack of electrode groups having a charged electrolyte solution, a fatty acid ester having a sorbitan skeleton having an HLB value of 12 or less is added to the electrode group. Storage battery. 2. The sealed alkaline zinc storage battery according to claim 1, wherein the fatty acid ester having a sorbitan skeleton is added to the electrolytic solution. 3. The sealed alkaline zinc storage battery according to claim 1, wherein the fatty acid ester having a sorbitan skeleton is added to the zinc negative electrode. 4. The sealed alkaline zinc storage battery according to claim 1, wherein the fatty acid ester having a sorbitan skeleton is added to the liquid retaining layer.