A doping strategy for improving high rates performance of LiNi0.90Co0.05Mn0.05O2 cathode

The Li1-x(Ni0.9Co0.05Mn0.05)MgxO2 (MNCM) cathode materials are prepared by ball milling-drying spray method. XRD and XPS proved that Mg2+ occupied the Li layer, reduced Li/Ni mixture and inhibited phase transition, which stabilized the structure of Li(Ni0.9Co0.05Mn0.05)O2 (NCM). Mg doping can improve capacity and cycling stability by reducing voltage attention at high rate. The Li0.99(Ni0.9Co0.05Mn0.05)Mg0.01O2 (MNCM1) cathode shows an excellent capacity of 164 mAh/g, and the corresponding cycle retention is 89 % at 5C (1C = 200 mAh/g) after 150 cycles, much higher than NCM (144.5 mAh/g and 50.1 %). The results of EIS show that Mg doping can effectively improve the lithium ion diffusion coefficient and reduce the impedance generated during the cycles. In addition, the cycle performance of NCM/graphite full battery is also significantly improved with the help of Mg doping. After cycling, SEM of electrode materials shows that MNCM1 retained more secondary spherical particles, which proved that Mg doping can improve the structural stability of materials during cycles.