Abstract:

The microstructure and electrochemical properties of (2Mg+Fe)+x%Ni(mass fraction)  composites(x=0, 50, 100, 200) prepared by using the ball milling method have been investigated. The results show that there are still Mg and Fe single phase for the nickel-free mixtures of Mg and Fe powders milled for 120 h, and the discharge capacity of the nickel-free composite is less than 20 mA·h/g. However, increasing the Ni content and enhancing the milling power make it easy to form amorphous Mg-Fe structure and to reduce the crystal size. The Mg-Fe composites could reach higher amorphorization extent and the  better electrochemical properties with introducing more amount of Ni. Compared with the composites obtained by milling with the uniform balls, the composites milled with mixed balls have a higher amorphorization extent, much more homogeneous and smaller particle sizes. As x=100, the maximal discharge capacities of the composite milled for 120 h with the balls of  different sizes and the uniform balls are 542.0 and 455.3 mA·h/g, respectively.

Key words: Mg-based hydrogen storage electrode; Mechanical alloying; Amorphism; Electrochemical property; Ball-milling parameter