Preparation of Mg2$minus;xRExNi (RE = La, Ce, Pr, Nd, Y) alloys and their electrochemical characteristics

Abstract

A series of Mg 2− x Nd x Ni ( x =0.05, 0.1, 0.2, 0.3) and Mg 1.95 RE 0.05 Ni (RE=La, Ce, Pr, Nd, Y) ternary alloys were prepared by ball milling of mixed powder of Mg, Ni, RE and sintering under pure argon. XRD analysis shows that Mg 2− x Nd x Ni ( x =0.05, 0.1) and Mg 1.95 RE 0.05 Ni alloys are all single-phase with the same crystal structure as Mg 2 Ni while three phases (including Mg 2 Ni, NdNi and NdMgNi 4 ) were formed in Mg 1.8 Nd 0.2 Ni and Mg 1.7 Nd 0.3 Ni alloys. The lattice constants ( a , c , c / a ) of Mg 2 Ni phase in these ternary alloys were calculated. Calculated values of a and c are strongly influenced by elemental substitution, while no different changes were observed in a / c . The electrochemical characteristics of the alloys were evaluated by simulated battery test. It is found that the initial discharge capacity of Mg 2− x Nd x Ni alloy milled for 10 h was obviously improved with increasing Nd content. A good cycle life was also observed in the Mg 1.7 Nd 0.3 Ni alloy electrode. It is suggested that combined effects contribute to the enhancement in electrochemical characteristics, the presence of NdMgNi 4 being beneficial for the improvement in cycle life of Mg 2− x Nd x Ni ( x =0.2, 0.3), especially for the Mg 1.7 Nd 0.3 Ni alloy electrode. As to Mg 2− x RE x Ni alloys, the effectiveness in improving the discharge capacity increased in the following order: Pr>Nd>Ce>La>Y.