JPS5931177B2 - Zinc electrode for alkaline storage battery - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the improvement of zinc electrodes for alkaline storage batteries in which a zinc active material layer is provided on the surface of a core body, and in particular to the improvement of zinc electrodes for alkaline storage batteries. It has improved IX characteristics and heavy load characteristics.

Hitherto, alkaline storage batteries using zinc as a cathode have been developed, such as Yutskele zinc storage batteries and silver-zinc storage batteries, some of which have already been put into practical use.

The cathode of these alkaline storage batteries is made of a sheet-like metal core with a zinc-based electrode active material layer formed into a sheet shape using a binder and made of an electrode material mainly composed of zinc, zinc oxide, etc., which is bonded to the sheet-like metal core. In this way, an alkaline storage battery whose cathode is an electrode plate with a zinc-based electrode active material layer on a metal core has an operating voltage 0.2 to 0.4 V higher than a nickel-cadmium storage battery whose cathode is cadmium. Despite its superior performance,
It has not yet been put into practical use because of its short discharge cycle life and poor heavy load discharge characteristics. The reason for the short discharge cycle life and poor heavy load characteristics of alkaline storage batteries used as subchain deprived cathodes is that hydrogen gas generated from the cathode during charging cannot be completely suppressed. That is, the zinc cathode has a negative potential compared to the cadmium cathode, and the overvoltage of zinc itself is low, so hydrogen gas is easily generated. Therefore, as a means to prevent the generation of hydrogen gas during charging, it has been proposed to amalgamate about 8 squares of the cathode with mercury, but the overvoltage of the material forming the metal core against hydrogen gas generation is low. Even if hydrogen gas generation is suppressed from the electrode active material layer mainly composed of zinc, hydrogen gas generated from the metal core cannot be completely suppressed.
In this way, even if the amount of hydrogen gas generated from the metal core is small, the zinc active material provided in close contact with the core gradually peels off and entangles, resulting in a decrease in electronic conductivity during charging and discharging. ,
As a result, the discharge cycle life of the storage battery is reduced and the physical properties under heavy load are deteriorated. In view of the above, the present invention has been developed as a result of conducting various studies, and as a result, zinc The object of the present invention is to provide a zinc electrode for an alkaline storage battery that has improved discharge cycle characteristics and heavy load characteristics using a system electrode active material layer. The present invention will be described in detail below based on one embodiment shown in the drawings.

In Figures 1 and 2, 1 is a zinc electrode, and this zinc electrode 1
A conductive resin layer 3 is formed by bonding a conductive material with a higher hydrogen overvoltage than a zinc active material with an alkali-resistant resin on the surface of a metal core body 2 made of a porous metal plate made of silver, copper, or an alloy thereof. A sheet-like zinc-based electrode active material layer 4 is provided. In the figure, 5 is a conductive terminal made of a material with excellent electrical conductivity such as silver foil. Conductive materials such as zinc, amalgamated zinc, and zinc oxide that have a higher hydrogen overvoltage than zinc active materials include metal powders such as bismuth, silver, indium, cadmium, and metal amalgamates, as well as carbon black, acetylene black, and scaly graphite. Graphite powder such as Ruru.

Examples of alkali-resistant resins that bind these conductive material powders include polyvinyl alcohol, polystyrene, and epoxy resins. It is preferable to mix conductive material powder at a weight ratio of 1 to 10 parts per 10 parts of this aqueous solution.If the weight ratio is less than the lower limit of this range, there will be no sufficient suppressing effect on hydrogen gas generation, and if it exceeds the upper limit, the viscosity will increase. becomes high, making it difficult to form a thin conductive resin layer on the surface of the metal core. Further, the thickness of this conductive resin layer 3 may be 5μ or more, and the thickness of the conductive resin layer 3 may be 5μ or more. A thickness of approximately 1OOμ is preferable, but if it is too thick, the volume of the storage battery becomes large, which is not preferable. The zinc electrode 1 having the above structure is used, for example, as the cathode 6 of a nickel-zinc alkaline storage battery as shown in FIG. A separator 8 made of a non-woven fabric of polyamide resin is sandwiched between the anode 7 formed by filling a nickel active material into a porous sintered substrate made of sintered nickel powder for the alkaline storage battery and the zinc cathode 6. is spirally wound to form a cylindrical power generation element 9, and this power generation element 9 is housed in a cylindrical metal container 10 which also serves as a cathode terminal, and an alkaline electrolyte is injected into a sealed nickel-zinc. It forms an alkaline storage battery. In the figure, reference numeral 11 denotes an insulating sealing plate for sealing the opening of the metal container 10, and an anode terminal 12 connected to the conductive terminal 5 is provided in the center of the insulating sealing plate 11.

Further, 13 is a zinc electrode conductive terminal that connects the cathode 6 and the metal container 10, and 14 is an insulating plate. In the alkaline storage battery having the above structure, the cathode 6 has a structure in which a metal core 2 with a low hydrogen overvoltage is coated with a conductive resin layer 3 made of a conductive material with a higher hydrogen overvoltage than zinc and an alkali-resistant resin. Therefore, even during charging, hydrogen gas generation from the metal core 2 can be completely suppressed, and as a result, the zinc-based electrode active material provided on the surface of the metal core 2 via the conductive resin layer 3 can be completely suppressed. This can prevent the layer 4 from peeling off or falling off.

Next, specific examples of the present invention will be described.

A large number of holes are formed in a copper plate having a thickness of 0.15 mu, a width of 33 mm, and a length of 165 mm to form a metal core, and a conductive terminal made of silver foil is welded to this metal core. Next, an alkali-resistant resin prepared by dispersing 3 tons of bismuth metal powder in 10 m 2 of a 5% by weight aqueous polyvinyl alcohol solution is applied to the surface of the metal core to form a conductive resin layer with a thickness of 100 μm. Also 10% by weight amalgamated zinc 107, zinc oxide 70r,
After sufficiently mixing 10 tons of calcium hydroxide and kneading with 30 me of a polytetrafluorethylene dispersion having a content of 20% by weight, the mixture was rolled 8 to 12 times to a thickness of 0.35.
A zinc-based electrode active material layer of mm thickness is created. This electrode active material layer is pressure-bonded to both sides of the metal core on which the conductive resin layer is formed, thereby creating a zinc cathode. This zinc cathode was laminated with a nickel anode through a separator made of polyamide resin to produce a nickel-zinc alkaline storage battery as shown in FIG. This nickel-zinc alkaline storage battery is charged by applying a current of 300 mA at room temperature for 7 hours, and the discharge capacity is the same when the discharge voltage is 1.0 after repeated discharging and charging. We measured how the battery's temperature changes and investigated the cycle characteristics of the storage battery. The results are shown by curve A in the graph of FIG. Further, this storage battery was charged by applying current for 7 hours with a current of VC3OOmA, and then discharged with a current of 1500 mA, and the discharge time until the voltage reached 1.0 was measured to examine heavy load characteristics. The results of this measurement are shown by curve A in the graph of FIG. For comparison with the present invention, a nickel-zinc alkaline storage battery without the conductive resin layer was prepared in the above example, and its cycle characteristics and heavy load characteristics were measured, and the results are shown in FIGS. 4 and 4. Each curve is shown as curve B in Fig. 5.

Although the above-mentioned Example Vc was shown using a porous metal plate as the metal core, the present invention is not limited to this, and it is also possible to use, for example, a wire mesh, engineered scrap pad metal, or the like.

As explained above, according to the zinc electrode for an alkaline storage battery according to the present invention, a conductive material having a higher hydrogen overvoltage than a zinc active material is bonded to the surface of a metal core via a conductive resin layer bound with an alkali-resistant resin. Because it has a structure with a zinc-based active material layer that is rolled and formed into a single bottom shape, it is possible to prevent the generation of hydrogen gas from the metal core, which has a low hydrogen overvoltage, even when charging is performed in an alkaline electrolyte. In addition, together with the binding properties of the alkali-resistant resin, the metal core and the zinc-based active material layer can be firmly bonded over a long period of time. Therefore, even after repeated charge/discharge cycles, the zinc active material does not peel off or fall off from the metal core, improving cycle life. It can have remarkable effects such as being able to significantly improve heavy load characteristics. Brief explanation of the drawings FIG. 1 is a partially cutaway front view of a zinc electrode for an alkaline storage battery according to the present invention, FIG. 2 is a cross-sectional view taken along the line - in FIG. 1, and FIG. 3 is a cross-section of the alkaline storage battery. 4 is a graph showing cycle characteristics, and FIG. 5 is a graph showing heavy load characteristics.

DESCRIPTION OF SYMBOLS 1... Zinc electrode, 2... Metal core, 3... Conductive resin layer, 4-I zinc-based electrode active material layer, 5... Conductive terminal,
6... Cathode, 7... Anode, 8... Separator,
9... Power generation element.

Claims (1)

[Claims] 1. An alkaline electrode characterized in that a zinc-based electrode active material layer is provided on the surface of a metal core via a conductive resin layer in which a conductive material having a higher hydrogen overvoltage than a zinc active material is bound with an alkali-resistant resin. Zinc electrode for storage batteries.