The structure and high-temperature (333 K) electrochemical performance of La0.8−xCexMg0.2Ni3.5 (x = 0.00–0.20) hydrogen storage alloys

The microstructures and electrochemical properties of La0.8−xCexMg0.2Ni3.5 (x = 0.00–0.20) hydrogen storage alloys are investigated systematically. XRD and Rietveld analyses indicate that all these alloys mainly consist of two phases: (La, Mg)2Ni7 phase with the hexagonal Ce2Ni7-type structure and LaNi5 phase with the hexagonal CaCu5-type structure. The lattice parameters of the component phases gradually decreased with increasing Ce content. It is concluded that, compared to that of room temperature (298 K), the deterioration in capacity is due to the enhanced corrosion of electrode active material and self-discharge at 333 K. The electrode corrosion was alleviated effectively with the increasing x, whereas the high-temperature dischargeability decreases from 92.7% (x = 0.00) to 80.5% (x = 0.20) accordingly. As the discharge current density is 1000 mA g−1, the high-rate dischargeability (HRD) increases from 77.2% (x = 0.00) to 89.7% (x = 0.10) and then decreases to 73.5% (x = 0.20).