OXIDATIVE DELITHIATION OF ALKALI NICKEL OXIDE

Provided are methods of preparing an electrochemically active cathode material including the steps of (a) combining an alkali metal-containing layered nickel oxide having a formula A1-aNi1+aO2, wherein A comprises an alkali metal and 0 < a ≤ 0.2, with an oxidant comprising a peroxydisulfate salt and/or a monopersulfate salt to form a mixture, (b) heating the mixture to form a Ni(IV) containing mixture including a Ni(IV) containing electrochemically active cathode material; (c) adding to the Ni(IV) containing mixture of step (b) a mineral acid; and (d) heating the mixture of step (c) to form an additional amount of the Ni(IV) containing electrochemically active cathode material, the Ni(IV) containing electrochemically active cathode material formed in steps (b) and (d) having a general formula AxHyNi1+aO2, wherein A comprises an alkali metal; 0.08 ≤ x < 0.2; 0 ≤ y < 0.3; and 0.02 ≤ a ≤ 0.2.