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

The structure and properties of new La-Y-Ni system alloys with high hydrogen-storing capacity were investigated using X-ray diffraction (XRD), scanning electron microscope (SEM), solid-H-2 reactions (P-C-I curves) and electrochemical measurements. The LaY2Ni8.2Mn0.5Al0.3 (AB(3)-type), LaY2Ni9.7Mn0.5Al0.3 (A(2)B(7)-type) and LaY2Ni10.6Mn0.5Al0.3 (A(5)B(19)-type) hydrogen storage alloys were prepared with the induction-melting rapid-quenching method and annealed at 1148 K for 16 h. The La-Y-Ni-Mn-Al alloys were also compared with commercial ABs-type hydrogen storage alloy with high capacity. Similarly to La Mg-Ni system hydrogen storage alloy, La-Y-Ni system alloys are multiphase structures and Y element in the La-Y-Ni alloys avoid or delay the hydrogen-induced amorphous (HIA) of the alloys in the hydrogenation/dehydrogenization process. The hydrogen storage capacities of the A(2)B(7)- and A(5)B(19)-type alloys at 313 K are 1.48 wt.% and 1.45 wt.%, respectively, which are larger than that of the AB(5)-type alloy (1.38 wt.%). The maximum discharge capacities of the A(2)B(7)- andA(5)B(19) -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 AB(5)-type alloy (356.1 mAh g(-1)). The maximum discharge capacity of the A(2)B(7)-type alloy exceeds the theoretical capacity (372 mAh g(-1)) of the AB(5)-type alloy. The A(2)B(7)- and A(5)B(19)-type alloy electrodes have better cycling ability than the AB(5)-type alloy. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.