Synthesis of calcium and magnesium periodates for the development of high oxidation state battery cathodes

We present the synthesis of calcium and magnesium periodates using NaIO4 and corresponding CaCl2 and MgCl2 respectively via precipitation reactions. The elemental analysis shows a 1:1 atomic ratio between the metal and iodine. It is also found that during the synthesis, metaperiodate anions are converted to orthoperiodate anions. The synthesized samples are hydrated and have crystalline structures; yet upon heating, the structures of the samples turn amorphous. Periodate-zinc batteries are fabricated which utilize the oxidizing properties of the periodates. The Ca periodate, with an estimated formula of CaOH(H4IO6)⸱5H2O, exhibits a specific capacity of 460 mAh g−1 and a cell voltage of 1.4 V when combines with a zinc anode. Mg periodate is less suitable for electrode formulation due to its higher aqueous solubility and lower stability. [Display omitted] •Calcium and magnesium periodates are synthesized.•The atomic ratio between the alkaline earth metal and iodine is close to 1:1.•The calcium periodate with a Zn anode shows a specific capacity of 460 mAh g−1.•The reported specific capacity is over 50% higher than conventional MnO2 cathodes.