Synergistic effect for improving the hydrogen storage capability and electrochemical performance of AB2 Laves phase alloys.

The structure of a series AB 2 Laves-type metal hydride alloys, in which Ce was doped into Ti 0.24 Zr 0.76 Ni 1.15 Mn 0.7 V 0.15 and annealed the alloys, was studied and correlated to hydrogen storage properties and electrochemical performances. X-ray diffraction, scanning electron microscope, and energy-dispersive spectroscopy results revealed that Ce formed a CeNi 3 secondary phase instead of entering the Laves phases. The synergistic effect of the CeNi 3 and (Ti,Zr)Ni phase improved the hydrogen storage and electrochemical discharge properties of the Ce-doped (Ce 0.02) alloy. Especially, the secondary phases could decrease the hydrogen absorption plateau, reduce the hysteresis phenomenon, and increase the hydrogen storage capacity (from 0.9 wt% to 1.4 wt% at 25 ℃). The formation of CeNi 3 H x hydride on the surfaces of alloy electrodes led to a higher discharge capacity (∼500 mAh/g) and a faster activation rate. The Ce 0.02 alloy also showed a good cyclic stability ∼82.08%, after 500 charge-discharge cycling, which could be ascribed to the good corrosion resistance of the CeNi 3 phase on the surface of alloy. In addition, annealing treatment promoted the depletion of (Ti,Zr)Ni secondary phase and the transformation from the C14 to C15 phase. The Ce-doped AB 2 alloy can be used as a hydrogen storage and hydride battery electrode material. • Annealing resulted in the transformation from the C14 to C15 Laves phase. • Full discharge capacity of Ce 0.02 alloy as an anode reaches 500 mAh/g at 10 mA/g. • Synergistic effect of the CeNi 3 and (Ti,Zr)Ni phases on the Laves phases. • Secondary phases improves discharge and hydrogen storage capacity, and HRD ability. [ABSTRACT FROM AUTHOR]