Abstract: Methods of preparing desodiated and oxidized sodium nickelate materials using persulfate solution, and sodium nickelate materials prepared by such methods, are disclosed. Also disclosed are methods of preparing pre-aged beta nickelates using a hydroxide solution, and beta nickelates prepared by such methods. An alkaline cathode composition comprising electrolytic manganese dioxide and the desodiated and oxidized sodium nickelate and beta nickelates are also provided, as are alkaline electrochemical cells comprising these nickelates and compositions.