Uniform nanocrystalline AB 5-type hydrogen storage alloy: Preparation and properties as negative materials of Ni/MH battery

Abstract

AB 5-type nanocrystalline hydrogen storage alloy was prepared by a twin-roll process. X-ray diffraction (XRD), scanning electron microscope (SEM), pressure–composition isotherms (PCT), and charge–discharge cycling were used to characterize its performances. The alloy has a hexagonal CaCu 5-type structure and a uniform crystallite size of about 40 nm. It shows good high-rate discharge ability (HRD). The initial discharge capacity of the alloy is high up to 312 mAh/g, and its capacity loss is low, only about 20% after 400 cycles under 640 mA/g. At the discharge current density of 2000 mA/g, the high-rate discharge ability (HRD) is 90% and the discharge capacity 211mAh/g after 400 cycles, 85% of the initial capacity.