Ionic liquid-induced ultrathin and uniform N-doped carbon-wrapped T-Nb2O5 microsphere anode for high-performance lithium-ion battery

Orthorhombic-phase Nb2O5 (T-Nb2O5) has been widely investigated as an intercalation anode material for Li-ion batteries due to the larger interplanar lattice spacing and high safety. However, its applications are limited by the intrinsic low electric conductivity. Herein, an ultrathin N-doped carbon-coating layer was constructed on porous T-Nb2O5 microspheres uniformly via a convenient thermal treatment method with ionic liquid as a carbon precursor. The synthesized T-Nb2O5@N–C exhibits significantly enhanced rate capability (155.5 mAh·g–1 at 20C) than initial T-Nb2O5 (110.2 mAh·g–1 at 20C). Besides, T-Nb2O5@N–C shows ultralong cycle life, with only a 0.02% decrease in the capacity per cycle at a high current density of 10C. The corresponding electrochemical tests show that the preferable rate capability of T-Nb2O5@N–C electrode is attributed to the increased electronic conductivity and pseudocapacitance contribution induced by ultrathin surface N-doped carbon layer. On the other hand, the mesoporous structure of T-Nb2O5@N–C ensures fast Li+ diffusion dynamics and electrolyte penetration. Furthermore, T-Nb2O5@N–C also performs well in a LiNi0.5Mn0.3Co0.2O4||T-Nb2O5@N–C full cell. This work provides a facile method to construct integrated anode materials for potential applications in lithium-ion batteries.