Structural modification of isomorphous SO 4 2− -doped K 2 FeO 4 for remediating the stability and enhancing the discharge of super-iron battery

Abstract

In the paper, the isomorphous S O 4 2 − doped K 2 FeO 4 , aimed at the remediation of the discharge and stability of the super-iron battery, was first synthesized for doping and reforming the K 2 FeO 4 crystalline structure via a facile co-precipitation and mechanochemistry. Afterwards, the compared cathodes were assembled by the undoped and doped K 2 FeO 4 for an evaluation of the discharge and stability in the AAA super-iron battery system. The results show that the small amounts of K 2 SO 4 were doped into the K 2 FeO 4 in the calculated form of K 2 Fe 1−x S x O 4 by the isomorphous substitution. The doped K 2 FeO 4 cathodes/batteries exhibited an excellent discharge with a normal discharge profile. The cathodes doped by two techniques had significantly enhanced the discharge capacity of the super-iron battery with an increase of 10–30% compared to the undoped K 2 FeO 4 . Moreover, the stability of the K 2 FeO 4 cathodes was obviously remediated by the isomorphous S O 4 2 − doping. The shelf time of the doped K 2 FeO 4 cathodes was prolonged by an increase of about 10% in comparison of the undoped K 2 FeO 4 cathode. The desirable enhancements could be attributed to doping and reforming the similar building block and isomorphous S O 4 2 − into the Fe O 4 2 − tetrahedral and crystalline in the form of the isomorphous substitution and filling vacancies.