Electrochemical hydrogen storage in LaNi4.25Al0.75 alloys: A comparative study between film and powder materials

A comparison is made of the electrochemical and structural properties of LaNi4.25Al0.75 alloys in thin film and powder forms. X-ray diffraction (XRD) revealed that both the LaNi4.25Al0.75 thin film and powder materials are crystalline. Atomic force microscopy (AFM) and focused ion beam microscopy (FIB) proved that the film appeared to have a hill-like surface morphology, but was rather dense with a thickness of about 4.2 μm. Simulated battery tests indicate that both exhibit similar electrochemical behavior, possibly due to their crystal structure, as it requires a primary activation to reach its fully active state. However it took a longer activation period for the film to be activated; an apparent initial decrease of charging voltage with cycle number was observed, as were abnormal discharge processes during activation. After 30 charge/discharge cycles, small needle-shaped aluminium oxide particles were formed on both the powder and film surfaces.