Structures and electrochemical performances of as-cast and spun RE-Mg-Ni-Mn-based alloys applied to Ni-MH battery

Abstract

The RE-Mg-Ni-Mn-based AB2-type La_1−xCe_xMgNi_3.5Mn_0.5(x = 0−0.4) alloys were prepared by spinning treatment. For obtaining the optimum performance, the effects of Ce content and spinning rate on the hydrogen storage performance of the alloys were studied systematically. The results show that the variations of the spinning rate and Ce content result in noteworthy changes of the phase content without altering phase composition of the alloys. Specifically, the LaMgNi₄ phase increases and LaNi₅ phase decreases when increasing the spinning rate and Ce content. Furthermore, the crystalline grains of Ce-containing alloys prepared by spinning treatment are remarkably refined. The alloys own superior electrochemical performance. All alloys reach the optimal discharge capacity at the initial cycle. Increasing Ce content and spinning rate lead the discharge capacity and electrochemical kinetics rise to an optimal value and then start to reduce. Meanwhile, the electrochemical cycle stability is also improved, which is ascribed to the great enhancement of anti-pulverization and anti-corrosion abilities resulting from the spinning treatment and the substitution of Ce for La.