Influence of preparation methods of non-stoichiometric hydrogen-absorbing alloys on the performance of nickel–metal hydride secondary batteries

Abstract

Mm(Ni 3.8Al 0.2Mn 0.6) ( x−0.4)/4.6 Co 0.4 alloys with stoichiometry 5.0< x<5.8 were prepared through a rapid quenching process. Their microstructural and electrochemical characteristics were examined with regard to discharge capacity and durability of the negative electrode in a Ni–metal hydride (MH) battery. These multi-component alloys exhibited a high electrochemical reactivity and their discharge capacities were dominated by the stoichiometry x. The charge–discharge cycling stability was influenced by both stoichiometry and microstructure. The non-stoichiometry brought microstructural heterogeneity. However, the rapid quenching process homogenized it effectively and enhanced the cycle performance. Consequently, a capacity of 310 mA h g −1 and a durability of up to 500 cycles were obtained in rapidly quenched Mm(Ni 3.8Al 0.2Mn 0.6) ( x−0.4)/4.6 Co 0.4 ( x=5.2).