Rapid growth and improved functions of mobile equipment present the need for an advanced rechargeable battery with extremely high capacity. In this study, we investigated the application of fuel cell technology to an Fe-air rechargeable battery. Because the redox potential of Fe is similar to that of H(2), the combination of H(2) formation by the oxidation of Fe with a fuel cell has led to a new type of metal-air rechargeable battery. By decreasing the operating temperature, a deep oxidation state of Fe can be achieved, resulting in enlarged capacity of the Fe-air battery. We found that the metal Fe is oxidized to Fe(3)O(4) by using H(2)/H(2)O as mediator. The observed discharge capacity is 817 mA h g(-1)-Fe, which is approximately 68% of the theoretical capacity of the formation of Fe(3)O(4), 1200 mA h g(-1)-Fe, at 10 mA cm(-2) and 873 K. Moreover, the cycle stability of this cell is examined. At 1073 K, the cell shows a discharge capacity of ca. 800 mA h g(-1)-Fe with reasonably high discharge capacity sustained over five cycles.

There is a strong demand for the development of a large capacity rechargeable battery in various fields.Recently, we proposed the combination of solid oxide fuel cell technology with Fe-air battery concepts using H 2 /H 2 O as a redox mediator and a LaGaO 3 -based oxide as an electrolyte. Because large internal resistance and large degradation during charge and discharge cycles were observed on the anode, there is a strong demand for improvements in discharge potential and cycle stability. This study investigates the use of a cermet anode consisting of a Ni-Fe alloy combined with an oxide ion conductor. It was observed that by using a cermet anode of Ni-Fe combined with Ce 0.6 Mn 0.3 Fe 0.1 O 2 (CMF), the observed capacity of the cell was improved to 1163 mAh g 21 Fe 21 at 10 mA cm 22 and 873 K. This is about 97% of the theoretical capacity by assuming the formation of Fe 3 O 4 (1200 mAh g 21 Fe 21 ). Cycle stability of the cell was also considerably improved with the use of a Ni-Fe-CMF anode compared to a Ni-Fe anode because of the suppressed aggregation provided by the mixing of Ni with CMF.