INFLUENCE OF PREPARATION METHODS OF NONSTOICHIOMETRIC HYDROGEN-ABSORBING ALLOYS ON THE PERFORMANCE OF NICKEL-METAL HYDRIDE SECONDARY BATTERIES

Mm(Ni3.8Al0.2Mn0.6)((x-0.4)/4.6)Co-0.4 alloys with stoichiometry 5.0<x <5.8 were prepared through a rapid quenching process. Their microstruc tural and electrochemical characteristics were examined with regard to discharge capacity and durability of the negative electrode in a Ni-m etal hydride (MH) battery. These multi-component alloys exhibited a hi gh electrochemical reactivity and their discharge capacities were domi nated by the stoichiometry x. The charge-discharge cycling stability w as influenced by both stoichiometry and microstructure. The non-stoich iometry brought microstructural heterogeneity. However, the rapid quen ching process homogenized it effectively and enhanced the cycle perfor mance. Consequently, a capacity of 310 mA h g(-1) and a durability of up to 500 cycles were obtained in rapidly quenched Mm(Ni3.8Al0.2Mn0.6) ((x-0.4)/4/6)Co-0.4 (x=5.2).