An unusual solubility domain for KIO4 in KOH solution is observed, which is consistent with a potential use of periodate as a cathode for alkaline batteries. With increasing alkalinity, the solubility of KIO4 first increases, then drops from 2.9 M to < 10−4 M with increase from 6 to 10 M KOH. The unusual rapid transition from high to low solubility with increasing KOH is attributed to the formation of insoluble periodate complex. Accompanying the favorable low solubility in concentrated KOH is a high degree of cathodic electroactivity in accord with two electron storage: IO4
− ⊒ IO3
−. Low cathode salt solubility minimizes interference with the anode. Zn anode alkaline batteries are studied with KIO4 and NaIO4 cathodes, have a potential of 1.4-1.5 V and discharge to over 95% of the intrinsic 2e− charge capacity. The cathode also exhibits good quasi reversibility (rechargeability) with an alkaline metal hydride anode.