Microstructures and electrochemical hydrogen storage properties of novel Mg-A1-Ni amorphous composites

摘要

The amorphous Mg-Al-Ni composites were prepared by mechanical ball-milling of Mg_17Al_12 with χ wt.% Ni (χ = 0, 50, 100, 150, 200). The effects of Ni addition and ball-milling parameters on the electrochemical hydrogen storage properties and microstructures of the prepared composites have been investigated sys_tematically. For the Mg_17A_12 ball-milled without Ni powder, its particle size decreases but the crystal structure does not change even the ball-milling time extending to 120 h, and its discharge capacity is less than 15 mAh g~-1. The Ni addition is advantageous for the formation of Mg-Al-Ni amorphous structure and for the improvement of the electrochemical characteristics of the composites. With the Ni content χ increasing, the composites exhibit higher degree of amorphorization. Moreover, the discharge capacity of the composite increases from 41.3 mAh g~-1 (χ = 50) to 658.2 mAh g~-1 (χ = 200) gradually, and the exchange current density 1o increases from 67.1 mA g~-1 (χ = 50) to 263.8 mA g~-1(χ = 200), which is con_sistent with the variation of high-rate dischargeability (HRD). The ball-milled Mg_17A_l2 + 200 wt.% Ni composite has the highest cycling discharge capacity in the fIrst 50 cycles.