Crystallographic and Electrochemical Hydrogen Storage Characteristics of La0.7Ce0.3Ni4.2Mn0.9-xCu0.3(W0.42Fe0.58)x alloys

Microstructures and electrochemical characteristics of La0.7Ce0.3Ni4.2Mn0.9-xCu0.3(W0.42Fe0.58) x (x = 0-0.20) hydrogen storage alloys are systematically investigated. X-ray diffraction and backscattered electron results indicate that the pristine alloy is single LaNi5 phase, while the alloys containing W0.42Fe0.58 consist of LaNi5 matrix phase and a trace of W segregate phase. All alloy electrodes show an excellent activation performance and can be completely activated within four charge/discharge cycles. The maximum discharge capacity of alloy electrodes first increases from 327.8 mAh/g (x = 0) to 333.6 mAh/g (x = 0.10), and then decreases to 328.2 mAh/g (x = 0.20) with increasing x value. The high-rate dischargeability the alloy electrodes at the discharge current density of 1200 mA/g first increases from 60.8% (x = 0) to 75.2% (x = 0.15), and then decreases to 63.5% (x = 0.20). The cycling capacity retention rate at the 100th charge/discharge cycle is decrease monotonously from 79.3 % (x = 0) to 59.0 % (x = 0.20) with increasing the content of W0.42Fe0.58 alloy, which should be ascribed to the deterioration of corrosion resistance of alloy electrode in the charging/discharging cycle.