Study on the structure and electrochemical performance of AB_3-type hvdrosen storage composite electrode material

摘要

The La_(0.7)Mg_(0.3)Ni_(2.875)Co_(0.525)Mn_(0.1) alloy was synthesized by melting with intermetallic alloy La_2Mg_(17). 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)Ni_3 phase with the rhombohedral PuNi_3-type structure and the LaNi_5 phase with the hexagonal CaCu_5-type structure, the lattice parameters and cell volumes of the (La,Mg)Ni_3 phase increased with the increasing NiB weight ratio, while the LaNi_5 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.