Electrochemical impedance spectroscopic characterization on nano-sized Ca₃Co₃FeO₉ electrode with enhanced capacity retention

A Ca₃Co₃FeO₉ electrode exhibiting enhanced cycle-life performance compared to that of Co₃O₄ was presented in this study. In order to examine the mechanism of the improved capacity retention in the Ca₃Co₃FeO₉ electrode, the cycling-induced variation of electrode kinetics was observed using electrochemical impedance spectroscopy. The separable electrochemical reactions using the appropriate equivalent circuit and the goodness-of-fit results demonstrated the superior charge-transfer kinetics of Ca₃Co ₃FeO₉, compared to Co₃O₄, during prolonged cycling. These results clearly demonstrated the benefits of the inactive CaO matrix that is spontaneously formed in Ca₃Co ₃FeO₉ during the first discharge process.