Effects of the substitution of Mn for Ni on structures and electrochemical performances of the as-cast and quenched La0.5Ce0.2Mg0.3Co0.4Ni2.6-xMnxLa0.5Ce0.2Mg0.3Co0.4Ni2.6-xMnx(x=0–0.4)(x=0–0.4) electrode alloys

The effects of the substitution of Mn for Ni on the structures and electrochemical characteristics of the as-cast and quenched La0.5Ce0.2Mg0.3Co0.4Ni2.6-xMnxLa0.5Ce0.2Mg0.3Co0.4Ni2.6-xMnx (x=0x=0, 0.1, 0.2, 0.3, 0.4) alloys were studied systematically. The results obtained by XRD, SEM and TEM indicate that the as-cast and quenched alloys mainly consist of two major phases the (La,Mg)Ni3(La,Mg)Ni3 and LaNi5LaNi5 and a residual phase LaNi. With increasing Mn content in the alloys, the abundance of the (La,Mg)Ni3(La,Mg)Ni3 phase decreases and that of the LaNi5LaNi5 phase increases and both the lattice parameters and the cell volumes of major phases (La,Mg)Ni3(La,Mg)Ni3 and LaNi5LaNi5 increase. The as-quenched alloys display a nanocrystalline structure, and the grain sizes of the alloys are in a range of 20–30 nm. The results by the electrochemical measurements indicate that the discharge capacities of the as-cast and quenched alloys first increase and then decrease with the variety of Mn content and obtain the maximum values for a Mn content of x=0.2x=0.2. The substitution of Mn for Ni clearly improves the high rate discharge abilities (HRDs) and the activation capabilities of the as-cast and quenched alloys, but it slightly impairs the cycle stabilities of the as-cast and quenched alloys.