A 57Fe Mössbauer spectroscopy study of cobalt ferrite conversion electrodes for Li-ion batteries

The reverse micelles method has been employed to obtain cobalt ferrite samples. The effect of the type of surfactant and volumetric proportion of the aqueous and organic phases on the electrochemical behavior has been evaluated. The sample prepared using Span 80 as a surfactant and equivalent volumes of the aqueous and organic phases showed the highest capacity values and rate capabilities. It has been correlated to the better stability of the faradaic conversion process upon cycling for this sample. Based on the 57Fe Mössbauer spectra of discharged electrodes, this result has been associated to the preservation of reduced iron atoms into the core of the particles. The metallic atoms are ready to be oxidized, thus sustaining the reversible electrochemical reaction in further cycles.