Abstract:In this paper, the microstructure and the electrochemical properties of RE(NiCoMnAl) 5 hydride alloy with different composition of rare earth have been investigated. The results show that, for all the samples studied, the crystalline structure is CaCu 5 type hexagonal structure and the metallographic structure is dendrite, while, the unit-cell volume decreases after being substituted part La by other rare earth elements. The effect of the composition of rare earth on the electrochemical properties of RE(NiCoMnAl) 5 alloy is marked. As compared with La(NiCoMnAl) 5 alloy, the electrochemical capacity of RE(NiCoMnAl) 5 alloy decreases, the high-rate dischargeability improves and the cycling life enhances, where La is part substituted by others rare earth including Ce, Pr, Nd. The effect of the composition of rare earth on the electrochemical properties is related to the change of the microstructure of RE(NiCoMnAl) 5 alloy.