In the paper, the isomorphous SO42- 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 coprecipitation and mechanochemistry. Afterward, 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 SO42- 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 SO42- into the FeO42- tetrahedral and crystalline in the form of the isomorphous substitution and filling vacancies.