Thermal, electrochemical and structural properties of stabilized LiNiyCo1-y-zMzO2 lithium-ion cathode material prepared by a chemical route

Layered compounds, such as LiNiO2 and LiCoO2, have been extensively studied as active cathodic materials in lithium-ion batteries. Mixed oxides having general formula LiNiyCo1-yO2 represent a good compromise between the limit ed cyclability of LiNiO2 and the high cost of LiCoO2. However, recent studi es have demonstrated that LiNiyCo1-yO2 compounds are thermally unstable in their charged state, undergoing exothermic reactions that might cause therm al runaway and safety concern. The stability of the compounds may be greatl y controlled by doping with a suitable metal, M=Al, Mg. In this work we fur ther investigate the role of the doping metal on the thermal, electrochemic al and structural characteristics of the LiNiyCo1-y-zMzO2 electrode materia ls. These materials were prepared using a soft chemistry route, to achieve the proper control of the chemical homogeneity and of the microstructural p roperties of the final samples. The thermal behavior of the doped LiNiyCo1- y-zMzO2, where M=Al, was studied using differential scanning calorimetry. T he structural properties upon cycling were investigated by a recently, in-h ouse developed, in situ energy dispersive X-ray diffraction (EDXD) techniqu e. The reversibility and rate capabilities of the cathodes in lithium cells were characterized using electrochemical equipment.