Influences of Substitution of Zr for La on Structures and Electrochemical Performances of A2B7-Type Electrode Alloys by Melt-Spinning

Abstract

Abstract A 2 B 7 -type electrode alloys with a nominal composition of La 0.75- x Zr x Mg 0.25 Ni 3.2 Co 0.2 Al 0.1 ( x = 0, 0.05, 0.1, 0.15, 0.2) were prepared by casting and melt-spinning. The influences of the substitution of Zr for La on the structures as well as the electrochemical performances of the alloys were investigated. The results obtained by XRD, SEM and TEM show that the as-cast and spun alloys have a multiphase structure, consisting of two main phases (La, Mg)Ni 3 and LaNi 5 as well as a residual phase LaNi 2 . The substitution of Zr for La leads to an obvious increase of the LaNi 5 phase in the alloys, and it also helps the formation of a like amorphous structure in the as-spun alloy. The results of the electrochemical measurements indicate that the substitution of Zr for La obviously decreases the discharge capacity of the as-cast and spun alloys, but significantly improves their cycle stability. With increasing the spinning rate, the discharge capacity of the alloys ( x =0.1) first increases and then decreases, while the cycle stability monotonously rises.