Abstract: The amorphous Mg-Fe-Ni composites have been synthesized by mechanical ball-milling. The microstructure and electrochemical properties of the composites were characterized by XRD, SEM and electrochemical testing. The electrochemical properties of the composites vary greatly with the amount of Mg content and Ni introduced. For the (xMg+Fe)+200% (mass fraction) Ni (x=2, 3) composites, it is found that the maximal discharge capacity increases with increasing Mg content in the composites. The maximal discharge capacities of the composites with x=2, 3 were 391.9 mA•h•g^-1 and 480.8 mA•h•g^-1, respectively. The result also indicates that, for the ball-milled (3Mg+Fe)+y% Ni (y=50, 100, 200) composites, with increasing Ni content in the composites, the discharge capacity increases first and then decreases, and reaches a maximum value of 519.5 mA•h•g^-1 as y=100. In contrast, the discharge capacity of nickel-free (3Mg+Fe) composite is just 23.8 mA•h•g^-1. The microstructure analysis shows that the composites are mix structure composed two single phases with Mg and Fe for the nickel-free composite even after being milled for 120 h, but no new phase is formed. The composites milled with the addition of nickel powder could easily form Mg-Fe amorphous structure. Besides, the nickel powder in the composites plays a role of electro-catalysis, hereby the electrochemical properties of the Mg-Fe-Ni composites are effectively improved.

Key words: Hydrogen storage electrode material, Mechanical alloying, Amorphous, Electrochemical properties, Microstructure