Enhanced electrochemical properties of Ni-rich layered cathode materials via Mg2+ and Ti4+co-doping for lithium-ion batteries.

To optimize the electrochemical performance of Ni-rich cathode materials, the 0.005 mol of Mg2+ and 0.005 mol of Ti4+co-doping LiNi0.83Co0.11Mn0.06O2 composite powders, labeled as NCM-11, are successfully prepared by being calcinated at 750 °C for 15 h following by an appropriate post-treatment, which are confirmed by XRD, EDS and XPS. The results suggest that NCM-11 presents a well-ordered layered structure with a low Li+/Ni2+ mixing degree of 1.46% and Mg2+ and Ti4+ ions are uniformly distributed across the lattice. The cell assembled with NCM-11 can deliver an initial discharge specific capacity of 194.2 mAh g-1 and retain a discharge specific capacity of 163.0 mAh g-1 after 100cycles at 2.0C at 25 °C. Furthermore, it still maintains a discharge specific capacity of 166.7 mAh g-1 after 100cycles at 2.0C at 60 °C. More importantly, it also exhibits a higher discharge specific capacity of about 150.7 mAh g-1 even at 5.0C. Those superior electrochemical performance can be mainly ascribed to the synergistic effect of Mg2+ and Ti4+co-doping, in which Mg2+ ions can occupy the Li+ layer to act as pillar ions and Ti4+ ions can occupy the transition metal ions layer to enlarge the interplane spacing. Thus, the heterovalent cations co-doping strategy can be considered as a simple and practical method to improve the electrochemical performance of Ni-rich layered cathode materials for lithium-ion batteries.