Influence of Ti and Fe doping on the structural and electrochemical performance of LiCo0.6Ni0.4O2 cathode materials for Li-ion batteries

The combination of lithium cobalt oxide (LCO) and lithium nickel oxide (LNO) property for Li-ion batteries (LIB) brings a very promising cathode material, LiCo1-xNixO2 with a high specific reversible capacity and good cycling behaviour. Nonetheless, high toxic Co content and an instability of Li+/Ni2+ interaction in LiCo1-xNixO2 crystal structure paved the way for some modification for the development of this potential material. In this research, the self-propagating combustion method is used to reduce 40% Co content of LCO by replacing it with 40% Ni content resulting in cathode material with the stoichiometry of LiCo0.6Ni0.4O2 (LCN). To improve the stability of the LiCo0.6Ni0.4O2 structure, 5% of Ti and Fe was substituted at the Co site of the LCN material. The effect of these different cation substitutions (Ti4+ and Fe3+) on the structural and electrochemical performance of layered LiCo0.6Ni0.4O2 cathode materials was investigated. Rietveld refinement revealed that Fe doped material has the longest atomic distance Li-O in the structure that allow better Li+ diffusion during intercalation/deintercalation to give an excellent electrochemical performance (138 mAhg(-1)). After 50th cycle, it is found that the discharge cycling for Ti and Fe substituted materials were improved by more than 5% compared to pristine material. Both Ti and Fe doped materials were also having less than 13% of capacity fading indicates that the substitution of some Co with Ti and Fe are stable and can retain their electrochemical properties.