Co-doped MnO₂ nanorods with oxygen vacancies as anode for Li-ion battery

Doping is a common strategy to enhance the performance of the electrode materials; however, the detailed mechanism is not well analysed by MnO₂ anode-based literatures. In this work, metal-doped β-MnO₂ was prepared by a hydrothermal method and annealing process subsequently. Co and Zn were chosen as the representatives for activity- and non-activity doped metals. It is found the doped metal not only delayed the phase change and enhanced the degree of crystallinity, but also introduced many oxygen vacancies in the surface and bulk phases of the nanorods, as confirmed by characterizations. Oxygen vacancies favored an increase in the conductivity of the nanorods. Compared with Zn doping, Co doping introduced more oxygen vacancies and provided extra redox sites. As a result of these merits, Co-doped β-MnO₂ annealed at 500 °C displayed higher electrochemical performance for using as the anode of Li-ion batteries. At 100 mA/g, the discharge capacity was as high as 648 mAh/g for the 2nd cycle, and after 200 cycles, 68% capacity was retained.