Effects of cooling rate on microstructure and electrochemical performances of superstoichiometric AB 5 alloys with 5 wt.% Co have been investigated. Flakes of thickness ranging from 30 to 100 μm were obtained by melt spinning. The alloy microstructure was characterised using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and energy dispersive X-ray (EDX) microanalysis. Electrochemical evaluation did not show significant effect of the cooling rate on the initial capacity, but a noticeable effect was observed on cycle life and on corrosion rate after cycling. These results are discussed in terms of microstructural observations.