Multifunctional Ti-Mg co-doping strategy to enhance long term cycling performance for Ni-rich cathode materials

The practical application of the Ni-rich cathode materials is restricted by the inevitable structural collapse due to the phase transition and surficial instability during the long-term cycling. The co-doping with different metal ions is a useful way to improve the electrochemical performance of the Ni-rich cathode materials. Here, with different ratio of Ti-Mg co-doping Ni-rich cathode materials were prepared, and the synergetic effects of Ti-Mg co-doping on surface stability, structure reversibility and electrochemical performance of the Ni-rich cathode materials were studied in detail. Compared with the unmodified material and other ratio of Ti-Mg co-doping materials, the Li(Ni0.89Co0.11)0.99Ti0.005Mg0.005O2 delivers an initial discharge capacity of 214 mAh·g-1 at 0.1 C and 86.5% capacity retention after 200 cycles at 1 C with the voltage range of 2.8-4.3 V. Multiple characterizations were applied and revealed that the excellent performance for LiNi0.89Co0.11)0.99Ti0.005Mg0.005O2 is attributed to the uniformly distribution of Mg2+ ions in the bulk and the Ti4+ ions enriched near the surface. This unique distribution of Ti-Mg co-doping in this work could furnish the guidance for the design of doping strategies of Ni-rich cathode materials in the future.