Microstructures and electrochemical properties of LaNi3.55Co0.2−xMn0.35Al0.15Cu0.75(Fe0.43B0.57)x (x = 0–0.20) hydrogen storage alloys

Microstructures and electrochemical characteristics of LaNi3.55Co0.2−xMn0.35Al0.15Cu0.75(Fe0.43B0.57)x (x = 0–0.20) hydrogen storage alloys were investigated. X-ray diffraction and Backscatter electron results indicate that the pristine alloy is single LaNi5 phase with CaCu5 type hexagonal structure and the alloys containing Fe0.43B0.57 consist of two phases, matrix LaNi5 phase and La3Ni13B2 secondary phase. The abundance of La3Ni13B2 phase increases with the increase of x value. The a and V of LaNi5 phase increase with increasing x value. Maximum discharge capacity of the alloy electrodes monotonically decreases from 330.0 mA h g−1 (x = 0) to 302.2 mA h g−1 (x = 0.20). High-rate dischargeability of the alloy electrodes first increases with increasing x from 0 to 0.10, and then decreases when x increases to 0.20. Both charge-transfer reaction at the electrode/electrolyte interface and hydrogen diffusion in bulky alloys should be responsible for the high-rate dischargeability. Cycling stability decreases with increasing x from 0 to 0.20. The adequate substitution of Co by FeB can improve the overall electrochemical performances and reduce the raw cost of alloy electrode.