Effects of rapid quenching on the electrochemical performances and microstructures of the Mm(NiMnSiAl)4.3Co0.6−xFex (x = 0–0.6) electrode alloys

In order to improve the electrochemical performance of rare-earth-based AB5-type electrode alloy, the AB5-type Mm(NiMnSiAl)4.3Co0.6−xFex (x = 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6) electrode alloys were quenched by melt-spinning. The phase structures and microstructure morphologies of the as-cast and quenched alloys were analyzed by XRD, SEM and TEM. The effects of the rapid quenching on the microstructures and electrochemical performances of the alloys were investigated in detail. The obtained results show that the as-quenched alloys have an excellent activation performance and can be completely activated through two to five charge–discharge cycles. The effect of the rapid quenching on the capacities of the alloys with Fe content x ≤ 0.2 is minor, and the capacities and high rate discharge abilities of the alloys with Fe content x > 0.2 decrease significantly with the increase of quenching rate. The cycle lives of the alloys increase greatly with the increase of the quenching rate.