A Novel Active Material for the Negative Electrode in Alkaline Nickel Oxide Secondary Batteries

The charge-discharge characteristics of a series of Co3Mo compound powder electrodes has been investigated at303 K, as possible active materials for a negative lectrode in alkaline nickel oxide batteries. In addition to the compound powders, other Co-Mo alloys, pure Co powder, and mixtures of Co and Mo powders were also examined. On the first or second cycle, the Co3Mo electrodes exhibit a larger discharge capacity, which in some cases exceeds the nominal charge capacity of 450 mAhg- ~ for the alloy, and then the discharge capacity decreased rapidly with cycle number, remaining at about 240 mAhg- ~ ofalloy after 10 cycles. Formation of Co(OH)2 crystals is observed uring the charge-discharge processes, and the negative lectrode is not a conventional hydrogen-absorbing and desorbing metal hydride. The new battery is expressed by cobalt oxidation and nickel oxyhydroxide reduction for an overall battery discharge reaction: Co + 2NiOOH + 2H20- ~ Co(OH) ~ + 2Ni(OH) ~ with Ecell = 1.22 V. The observed larger discharge capacity on the first or second cycle, exceeding the nominal charge capacity is related to the desorption reaction of the electrochemically produced and adsorbed hydrogen atoms on the alloy particles, together with the dissolution reaction of cobalt. Recently, as a replacement for the cadmium negative electrode in rechargeable alkaline nickel oxide-cadmium batteries, many different multicomponent hydrogen stor