Structural modification of isomorphous SO4 2--doped K2FeO4 for remediating the stability and enhancing the discharge of super-iron battery.

In the paper, the isomorphous S O 4 2 - doped K2FeO4, aimed at the remediation of the discharge and stability of the super-iron battery, was first synthesized for doping and reforming the K2FeO4 crystalline structure via a facile co-precipitation and mechanochemistry. Afterwards, the compared cathodes were assembled by the undoped and doped K2FeO4 for an evaluation of the discharge and stability in the AAA super-iron battery system. The results show that the small amounts of K2SO4 were doped into the K2FeO4 in the calculated form of K2Fe1-xSxO4 by the isomorphous substitution. The doped K2FeO4 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 K2FeO4. Moreover, the stability of the K2FeO4 cathodes was obviously remediated by the isomorphous S O 4 2 - doping. The shelf time of the doped K2FeO4 cathodes was prolonged by an increase of about 10% in comparison of the undoped K2FeO4 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.