Ionic liquid-induced ultrathin and uniform N-doped carbon-wrapped T-Nb_(2)O_(5) microsphere anode for high-performance lithium-ion battery

Orthorhombic-phase Nb_(2)O_(5)(T-Nb_(2)O_(5)) 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-Nb_(2)O_(5) microspheres uniformly via a convenient thermal treatment method with ionic liquid as a carbon precursor.The synthesized T-Nb_(2)O_(5)@N-C exhibits significantly enhanced rate capability(155.5 mAh·g^(-1) at 20 C) than initial T-Nb_(2)O_(5)(110.2 mAh·g^(-1) at 20C).Besides,T-Nb_(2)O_(5)@N-C shows ultralong cycle life,with only a 0.02% decrease in the capacity per cycle at a high current density of 10 C.The corresponding electrochemical tests show that the preferable rate capability of T-Nb_(2)O_(5)@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-Nb_(2)O_(5)@N-C ensures fast Li+ diffusion dynamics and electrolyte penetration.Furthermore,T-Nb_(2)O_(5)@N-C also performs well in a LiNi_(0.5)Mn_(0.3)Co_(0.2)O_(4) llT-Nb_(2)O_(5)@N-C full cell.This work provides a facile method to construct integrated anode materials for potential applications in lithium-ion batteries.