Fe–air rechargeable battery using oxide ion conducting electrolyte of Y2O3 stabilized ZrO2

Solid oxide fuel cell concept was applied for Fe–air rechargeable battery by using H2/H2O as a mediator for Fe redox. Oxygen partial pressure in Fe set chamber during discharge was monitored simultaneously with O2 sensor for analysis of discharge mechanism. On the cell consisting of Pt anode, Y2O3 stabilized ZrO2(YSZ) electrolyte, and Pt cathode, 10 cycles of charge and discharge was stably performed, although decrease in capacity was observed at initial cycle. Oxygen partial pressure (PO2)(PO2) was monitored by zirconia oxygen sensor which is used for Fe set chamber. Simultaneous monitoring the oxygen partial pressure during the charge and discharge, the reasonable response of PO2PO2 in Fe set chamber was observed and for discharge, Fe seems to be oxidized to FeO and reduction to Fe was also confirmed. Impedance plots suggested that degradation could be assigned to the increased diffusion overpotential because of the decreased oxidation rate of Fe powder. However, after second cycles, internal resistance of the cell was stable up to 10 cycles examined. Therefore, application of SOFC concept and H2/H2O redox mediator is successfully demonstrated for the Fe–air rechargeable battery.

► SOFC concept was applied for Fe–air rechargeable battery by using H2/H2O as a mediator.
► 10 cycles of charge–discharge were performed over the 250 mAh g−1-Fe.
► Observed PO2 suggested that FeO was formed in discharge and reduced to Fe.
► Impedance analysis suggested that cell was highly stable during charge–discharge.