Study on the structure and electrochemical performance of AB3AB3-type hydrogen storage composite electrode material

The La0.7Mg0.3Ni2.875Co0.525Mn0.1La0.7Mg0.3Ni2.875Co0.525Mn0.1 alloy was synthesized by melting with intermetallic alloy La2Mg17La2Mg17. The composites contained NiB with different weight ratios (4%, 6%, 8%). The XRD analyses showed that all these alloys mainly consist of the (La,Mg)Ni3Ni3 phase with the rhombohedral PuNi3PuNi3-type structure and the LaNi5LaNi5 phase with the hexagonal CaCu5CaCu5-type structure, the lattice parameters and cell volumes of the (La,Mg)Ni3Ni3 phase increased with the increasing NiB weight ratio, while the LaNi5LaNi5 phase kept almost the same value. The electrochemical measurements showed that the maximum discharge capacity of the composites decreased, and the cycling life improved distinctly. At the discharge current density 1500 mA/g, the HRD (high rate discharge ability) increased from 57.0% to 71.3% (6%). Moreover, according to the electrochemical impedance spectroscopy (EIS) and the potentiodynamic polarization, the charge-transfer reaction resistance decreased and the anticorrosion performance improved in the alkali solution.