Structures and hydrogen storage performances of rare earth-Mg-Ni-Mn-based AB2-type alloys applied to Ni-MH battery

The La 1- x Ce x MgNi 3.5 Mn 0.5 ( x = 0, 0.1, 0.2, 0.3, 0.4) alloys were fabricated by melt spinning technology. The effects of Ce content and spinning rate on the structures and electrochemical performances of the alloys were investigated systematically. The identification of X-ray diffraction (XRD) and SEM revealed that the experimental alloys consisted of a major phase LaMgNi 4 and a secondary phase LaNi 5 . The variations of Ce content and spinning rate obviously changed the phase abundance of the alloys, namely LaMgNi 4 phase increasing and LaNi 5 phase decreasing with the increase of Ce content and spinning rate. The electrochemical test showed that the as-cast and as-spun alloys achieved the maximum discharge capacities just at the first cycling without any activation. With the increase of Ce content and spinning rate, the discharge capacity of the alloys first increased and then decreased, and the electrochemical kinetics of the alloys, involving the high rate discharge ability (HRD), hydrogen diffusion coefficient ( D ), limiting current density ( I L ), and charge transfer rate, had a similar variation trend, whereas their cycle stabilities have shown increasing trend.