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Electrochemical synthetic pathways for Fe͑VI͒ salts from an iron anode in alkaline electrolyte were compared, including a novel in situ direct synthesis of solid BaFeO 4 , or an ex situ two-step solution-phase electrochemical synthesis followed by chemical precipitation. A variety of electrolysis conditions including cell configuration, applied current density, temperature, synthesis duration, electrolyte composition and concentration, and the molar ratio between the reactants were probed and optimized. The in situ methodology decreases the complexity and time of synthesis, generating up to 95.9% BaFeO 4 purity, prepared at high current density from anodically biased iron in an aqueous co-electrolyte containing both Ba(OH) 2 and NaOH. In situ electrochemically synthesized BaFeO 4 exhibits near-identical IR absorption spectrum, and powder X-ray diffraction determined crystalline structure, as the chemically synthesized material, and exhibits enhanced stability towards prolonged thermal decomposition. It also supports facile charge transfer when incorporated as a cathode and discharged in nonaqueous lithium anode and aqueous alkaline zinc anode super-iron batteries.

In principle, alkali permanganates represent a substantial cathodic charge source for electrochemical storage, but high rate charge transfer has been inefficient. This study presents a novel Fe(VI) species (super-iron) and manganese redox chemistry synergism. Also presented is the high discharge energies from cathodes which utilize this phenomenon in a conventional cylindrical battery configuration. Batteries formed with a cathode combining BaFeO 4 and KMnO 4 , and using a conventional zinc alkaline anode in an AAA cylindrical cell configuration, exhibit an unusually high discharge capacity of 2.2 Wh. The discharge efficiency of solid alkaline permanganate or manganate cathodes is probed, and improved charge transfer of Mn(VII) redox chemistry in the presence of Fe(VI) is demonstrated. In a reciprocal manner, enhancement of Fe(VI) charge transfer are demonstrated upon inclusion of manganese salts, and also that added cesium further improves the combined Fe(V)/Mn(VII) cathode.