Investigations on AB3-, A2B7- and A5B19-type La[sbnd]Y[sbnd]Ni system hydrogen storage alloys

Abstract

The structure and properties of new LaYNi system alloys with high hydrogen-storing capacity were investigated using X-ray diffraction (XRD), scanning electron microscope (SEM), solid-H2 reactions (P-C-I curves) and electrochemical measurements. The LaY2Ni8.2Mn0.5Al0.3 (AB3-type), LaY2Ni9.7Mn0.5Al0.3 (A2B7-type) and LaY2Ni10.6Mn0.5Al0.3 (A5B19-type) hydrogen storage alloys were prepared with the induction-melting rapid-quenching method and annealed at 1148 K for 16 h. The LaYNiMnAl alloys were also compared with commercial AB5-type hydrogen storage alloy with high capacity. Similarly to LaMgNi system hydrogen storage alloy, LaYNi system alloys are multiphase structures and Y element in the LaYNi alloys avoid or delay the hydrogen-induced amorphous (HIA) of the alloys in the hydrogenation/dehydrogenization process. The hydrogen storage capacities of the A2B7- and A5B19-type alloys at 313 K are 1.48 wt.% and 1.45 wt.%, respectively, which are larger than that of the AB5-type alloy (1.38 wt.%). The maximum discharge capacities of the A2B7- and A5B19-type alloy electrodes at 298 K are 385.7 mAh g−1 and 362.1 mAh g−1, respectively, which are larger than that of the AB5-type alloy (356.1 mAh g−1). The maximum discharge capacity of the A2B7-type alloy exceeds the theoretical capacity (372 mAh g−1) of the AB5-type alloy. The A2B7- and A5B19-type alloy electrodes have better cycling ability than the AB5-type alloy.