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

In the paper, the isomorphous [Formula: see text] 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 [Formula: see text] 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 [Formula: see text] into the [Formula: see text] tetrahedral and crystalline in the form of the isomorphous substitution and filling vacancies.