Lithiated nickel dioxide and secondary cells prepared therefrom

Lithiated nickel dioxide cathode-active materials for electrochemical cells having the formula LixNi2-x-yMyO₂, with x being between about 0.8 and about 1.0, M being one or more metals selected from cobalt, iron, chromium, titanium, manganese and vanadium, and y being less than about 0.2, with the proviso that y is less than about 0.5 for cobalt, which material is substantially free of lithium hydroxide and lithium carbonate. The materials are prepared by providing a substantially homogeneous dry intermediate mixture of a starting material containing a nickel compound selected from nickel oxide, nickel hydroxide, and mixtures thereof, and optionally including one or more oxides or hydroxides of a transition metal selected from cobalt, iron, chromium, titanium, manganese and vanadium, together with between about a 10 and about a 25% stoichiometric excess of lithium hydroxide. The mixture is heat treated at a temperature above about 600°C in an atmosphere substantially free of carbon dioxide and having a partial pressure ratio of oxygen to water vapor greater than about 15, after which any lithium hydroxide or lithium carbonate present in the mixture is removed. Thermally stable lithiated nickel dioxide having a BET surface area less than about 3.0 m²/g, and is also disclosed, as well as electrochemical cells prepared from the disclosed lithiated nickel dioxides.