Electrochemical performance of the ball-milled La_2Mg_(14-x)Ti_xNi_3 alloys with Ni powders (x = l and 2)

摘要

The structure and electrochemical properties of the ball-milled La_2Mg_(14-x)Ti_xNi_3 (x=1 and 2) alloys with 200 wt.% Ni powders were systematically investigated. The XRD results show that the substitution of Ti for Mg in the as-cast alloys leads to the appearance of a second phase TiNi, whose contents increase with x value. The electrochemical results show that the substitution of Ti for Mg results in the enhancement of maximum discharge capacity and exchange current density due to the existence of TiNi phase, which can increase the electrocatalytic activity and reduce the electrochemical reaction resistance. With the increase of x value, the maximum discharge capacity increases from 704.8 mAh/g (x=0) to 815.2 mAh/g (x = 1) and 843.1 mAh/g (x=2). But the partial substitution of Ti for Mg also leads to the deterioration of cycling stability and high-rate dischargeability. The high-rate dischargeability of the ball-milled composites is mainly determined by the hydrogen diffusion rate in the alloy bulk.