Study on a low-cobalt Ml0.8Mg0.2Ni3.2Co0.3Al0.3 alloy

A low-Co Ml0.8Mg0.2Ni3.2Co0.3Al0.3 alloy was prepared and investigated by examining the alloy structure, phase composition, hydrogen absorption/desorption and electrochemical properties. The alloy is composed of Mg-free LaNi5 phase as matrix and Mg-contained LaNi3 phase as secondary phase. The hydrogen storage capacity (1.37 wt%) at 298 K, discharge capacity (320 mA h/g) and cycling stability (where 88% of the initial capacity remained after 300 charge/discharge cycles) of the alloy are as good as those of the commercial MmNi3.55Co0.75Mn0.4Al0.3 alloy. However, the high-rate discharge ability is better than that of the commercial alloy. The Mn-free composition is advantageous to the oxidization-resistant performance of the alloy. The secondary phase is tougher than the matrix, which not only contributes to the high-rate discharge ability, but also improves the fracture ductility and depresses the disintegration during charge/discharge cycle.