Abstract: 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.

Abstract: Provided are methods of preparing an electrochemically active cathode material including the steps of combining an alkali metal-containing nickel oxide having a formula A1?aNi1+aO2, wherein A comprises an alkali metal and 0<a?0.2, with a fluid composition including an oxidant comprising a peroxydisulfate salt, a monopersulfate salt, or a combination thereof to form a mixture, heating the mixture to a temperature of 50° C. or greater; and maintaining the mixture at the temperature for at least a period of time sufficient to form an alkali metal-deficient nickel oxide electrochemically active cathode material having a general formula AxHyNi1+aO2.nH2O, wherein A comprises an alkali metal; 0.08?x<0.2; 0?y<0.3; 0.02?a?0.2; and 0<n<2.