The origin of cycling enhanced capacity of Ni/NiO species confined on nitrogen doped carbon nanotubes for lithium-ion battery anodes

We demonstrate that the confinement effect of the NiO compound can directly enhance the electrochemical performance upon cycling. Fabricating the core-shell C-coated Ni/NiO nanofibers (e.g., Ni and NiO, nitrogen doped carbon respectively) composite electrode largely increases the capacity (1332 mAh g−1 vs 718 mA h g−1) and improve the long-term cycling stability. The High Angle Annular Dark Field results reveal that the doped pyridine-like nitrogen shell will divide the NiO into smaller nanoparticle during the charging and discharging process. In addition, the density functional theory calculation suggests the confined nanoscale NiO(Ni) will absorb and react with Li ions more easily. With cycling, smaller NiO/Ni nanoparticle will bring more active sites, leading additional interfacial lithiation capacity. At the same time, the confinement effect of the NiO compound further increases the capacity of the nanocomposites.