Optimization of the Composition of the Li_1 − z Ni_1 + z  O ₂ Electrode Materials: Structural, Magnetic, and Electrochemical Studies

Lithium nickel oxide, used as the positive electrode in lithium batteries, crystallizes in the rhombohedral system (SG:R3¯ m) with a layered structure. In fact, stoichiometric has never been reported. The true formula is (0.00 < z < 0.20); z is dependent on the experimental conditions. This nonstoichiometry leads to a strong decrease of the battery performance. Therefore, several methods of preparation were investigated to synthesize stoichiometric . The composition, which is very close to the ideal one, was obtained from a mixture of and NiO heated at 700°C. This quasi‐2D was submitted to several thermal treatments, in order to determine the influence of the temperature on the composition. Purposely lithium deficient phases were also prepared. Correlations between the composition of each material (deduced from the Rietveld refinement of the x‐ray diffraction pattern) and the magnetic and electrochemical behavior are discussed.