Effect of synthesis conditions and composition modification on the structural and electrochemical properties of layered transition metal oxide cathode materials

Novel and promising layered oxide cathode materials Li(Ni,Mn,Co)O₂, with improved capacity and high stability during cycling, were obtained by cationic substitution and by optimization of the synthesis conditions. These cathode materials were prepared by self-combustion method using metal nitrates and sucrose as fuel. Synthesis was then followed by annealing at 900°C during 1h. The temperature and annealing plateau were optimized in order to adjust the average particle size and size distribution. Two annealing atmospheres (argon and air) were used as well to investigate their effect on the structure and morphology of the NMC material. The time between synthesis and annealing was also varied in order to study the aging effect. X-ray diffraction was carried out as first step and showed that all the obtained materials crystallize in the rhombohedral system (α-NaFeO₂ type structure). The obtained results through scanning electron microscopy and galvanostatic cycling proved that the best performances were obtained for the substituted materials that were annealed directly after synthesis, under air atmosphere.