Improvement on cyclic stability of AB4-type La–Mg–Ni-based hydrogen storage alloys via merging Y element for nickel-metal hydride batteries

Abstract

The newly discovered AB4-type superlattice structure of rare earth–Mg–Ni-based (RE–Mg–Ni) alloys have extended cycle life and power performance, which are a promising anode material for nickel-metal hydride (Ni/MH) battery. However, the cycling stability still needs to be enhanced to meet the requirement of utilization. Herein, we design low cost single-phase AB4-type alloys and clarify the effect of merging Y on Mg on the electrochemical performance. Studies show that the cycling stability of the alloy is significantly enhanced after partial replacement of Y on Mg, where the discharge capacity of the La0.65Sm0.12Y0.10Mg0.13Ni3.60Al0.15 alloy maintains 234.5 mAh g−1 after cycling 500 times with a capacity retention of 61.8%, in contrast to 191.6 mAh g−1 with 50.6% of the La0.65Sm0.12Mg0.23Ni3.60Al0.15 alloy. The prolonged cycling life relates to the reduction of pulverization due to the increased matching degree of the sublattice structure, and the prevention of oxidation in terms of the oxide film of Y. Whereas, the discharge ability at high rates and low temperatures of the alloy are deteriorated after Y replacement. The results pave the way to the component design of the RE–Mg–Ni-based alloys for long-life Ni/MH batteries.