Dowa Mining Co., Ltd.

Makiko Yanagisawa

Fumihiro Sato

Kiyoshi Araki

Toshiya Kitamura

Ryo Sakamoto

Yasuhiko Niitsu

Masamitsu Kaga

Noriya Ishida

Takashi Onoue

Zinc powder comprising particles having part or all of their surfaces coated either with copper and/or indium or with silver is used as a battery material or an active material for the negative electrode in a battery. The powder can be used as an anode active material in a secondary battery to achieve a higher discharge capacity and better cycle characteristics.

Zinc powders for use in batteries and a secondary alkaline zinc battery

A novel primary or secondary battery whose active material for the negative electrode is composed of metallic gallium, gallium alloys or gallium oxide has first come into the world. Gallium has an electrochemical equivalent of 23.24, which is smaller than those of zinc (32.70) and cadmium (56.21). This indicates that when used as an active material for the negative electrode in batteries, gallium has larger capacity per unit mass than zinc and cadmium by respective factors of ca. 1.4 and 2.4. The potential of the reaction; Ga+6OH.sup.- =GaO.sub.3.sup.3- +3H.sub.2 O+3e.sup.- is obviously less noble than the voltage of hydrogen evolution and this means that a high-potential battery can be made. Due to the high hydrogen overvoltage of gallium, gallium ions in the solution can be precipitated as metallic gallium by electrodeposition. As a further advantage, no dendrite formation occurs during the electrodeposition unlike in the case of zinc. The high hydrogen overvoltage also contributes to the production of a battery that undergoes only limited self-discharge. What is more, gallium which has no toxicity presents few environmental problems.

Gallium based active material for the negative electrode, a negative

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Tokyo, Japan

Makiko Yanagisawa