Microstructures and electrochemical characteristics of La_(0.7)Ce_(0.3)Ni_(3.75-x)Cu_(0.75)Mn_(0.35)Al_(0.15)(V_(0.81)Fe_(0.19))_x (x = 0-0.20} hydrogen storage alloys

摘要

Microstructures and electrochemical characteristics of La_(0.7)Ce_(0.3)Ni_(3.75-x)Cu_(0.75)Mn_(0.35)Al_(0.15)(V_(0.81)Fe_(0.19))_x, (x = 0-0.20) hydrogen storage alloys have been investigated. X-ray diffraction patterns and Backscatter electron images indicate that La_(0.7)Ce_(0.3)Ni_(3.75-x)Cu_(0.75)Mn_(0.35)Al_(0.15)(V_(0.81)Fe_(0.19))_xalloys consist of a single phase with CaCu_5-type structure. The lattice parameter a and cell volume V increase with increasing x value. Maximum discharge capacity monotonically decreases from 320mAh/g (x = 0) to 299mAh/g (x = 0.20). The high-rate dischargeability at the discharge current density of 1200 mA/g first increases from 52.6% (x = 0) to 55.6% (x = 0.05), and then decreases to 46.7% (x = 0.20). Cycling stability first increases with increasing x from 0 to 0.10 and then decreases when x increases to 0.20. which is resulted from the combined effect of the improvement of the pulverization resistance and the decrease of corrosion resistance.