Microstructures and electrochemical hydrogen storage characteristics of La0.7Ce0.3Ni4.2Mn0.9−xCu0.37(Fe0.43B0.57)x (x = 0–0.20) alloys

Abstract Microstructures and electrochemical characteristics of La 0.7 Ce 0.3 Ni 4.2 Mn 0.9− x Cu 0.37 (Fe 0.43 B 0.57 ) x ( x  = 0–0.20) hydrogen storage alloys are investigated. X-ray diffraction and backscattered electron results indicate that the pristine alloy is single LaNi 5 phase while the alloys containing Fe 0.43 B 0.57 consist of LaNi 5 matrix phase and La 3 Ni 13 B 2 secondary phase. The relative abundance of La 3 Ni 13 B 2 phase increases with the increase in x  value. The a and V of LaNi 5 phase increase with increasing x value. Activation property of the alloy electrodes is improved by substituting Mn with Fe 0.43 B 0.57 . Maximum discharge capacity of the alloy electrodes monotonically decreases from 323.3 mAh g −1 ( x  = 0) to 311.3 mAh g −1 ( x  = 0.20). Cycling capacity retention rate at the 100th cycle decreases from 79.3% ( x  = 0) to 68.2% ( x  = 0.20) with increasing x value, which is ascribed to the degradation of corrosion resistance. High-rate dischargeability of the alloy electrodes first increases with increasing x from 0 to 0.10, and then decreases until x increases to 0.20. It demonstrates that the substitution of Mn with Fe 0.43 B 0.57 is an effective approach to improve the overall electrochemical performances of the Co-free high-Mn alloy electrodes.