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 limited cyclability of LiNiO2 and the high cost of LiCoO2. However, recent studies have demonstrated that LiNiyCo1-yO2 compounds are thermally unstable in their charged state, undergoing exothermic reactions that might cause thermal runaway and safety concern. The stability of the compounds may be greatly controlled by doping with a suitable metal, M=Al, Mg. In this work we further investigate the role of the doping metal on the thermal, electrochemical and structural characteristics of the LiNiyCo1-y-zMzO2 electrode materials. These materials were prepared using a soft chemistry route, to achieve the proper control of the chemical homogeneity and of the microstructural properties of the final samples. The thermal behavior of the doped LiNiyCo1-y-zMzO2, where M=Al, was studied using differential scanning calorimetry. The structural properties upon cycling were investigated by a recently, in-house developed, in situ energy dispersive X-ray diffraction (EDXD) technique. The reversibility and rate capabilities of the cathodes in lithium cells were characterized using electrochemical equipment.