SrFeO4: Synthesis, Fe(VI) characterization and the strontium super-iron battery

Cathodes comprised of Fe(VI) salts, and capable of three electron reduction, are useful for the formation of energetic super-iron batteries. This study presents a synthesis procedure for SrFeO4 or strontium super-iron cathodic salts, and also introduces mixed salts containing barium and strontium cations, SrxBa(1-x)FeO4. The X-ray diffraction and first IR spectra of SrFeO4 are presented, and compared to known spectra of K2FeO4 and BaFeO4. The measured solubility of SrFeO4 is low in concentrated KOH electrolytes (0.001 mM in 13.5 M KOH), of use for alkaline cathodic chemistry. AAA batteries were prepared and discharged with this new cathode, and exhibit high discharge energies, approaching, but lower than those previously observed for barium super-iron alkaline batteries. The discharge energy further approaches the barium cell when the mixed cathode salt is employed, particularly for x=0.25¯0.5 in SrxBa(1x)FeO4.