Microstructures and electrochemical properties of La0.7Ce0.3Ni3.75−xCu0.75Mn0.35Al0.15(Fe0.43B0.57)x hydrogen storage alloys

Microstructures and electrochemical characteristics of La0.7Ce0.3Ni3.75−xCu0.75Mn0.35Al0.15(Fe0.43B0.57)x hydrogen storage alloys have been investigated. X-ray diffraction results indicate that the alloys consist of a single phase with CaCu5-type structure, and lattice parameters c, cell volume V and c/a ratio increase with increasing x value. Maximum discharge capacity of the alloy electrodes first increases from 311.0 mAh/g (x = 0) to 316.0 mAh/g (x = 0.15), and then decreases to 311.0 mAh/g (x = 0.20). High-rate dischargeability at the discharge current density of 1200 mA/g first increases from 51.3% (x = 0) to 60.7% (x = 0.15), and then decreases to 53.6% (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 should be ascribed to the improvement of the pulverization resistance and the deterioration of corrosion resistance.