T-Nb O /C Nanofibers Prepared through Electrospinning with Prolonged Cycle Durability for High-Rate Sodium-Ion Batteries Induced by Pseudocapacitance.

Homogeneous ultrasmall T-Nb O nanocrystallites encapsulated in 1D carbon nanofibers (T-Nb O /CNFs) are prepared through electrospinning followed by subsequent pyrolysis treatment. In a Na half-cell configuration, the obtained T-Nb O /CNFs with the merits of unique microstructures and inherent pseudocapacitance, deliver a stable capacity of 150 mAh g at 1 A g over 5000 cycles. Even at an ultrahigh charge-discharge rate of 8 A g , a high reversible capacity of 97 mAh g is still achieved. By means of kinetic analysis, it is demonstrated that the larger ratio of surface Faradaic reactions of Nb O at high rates is the major factor to achieve excellent rate performance. The prolonged cycle durability and excellent rate performance endows T-Nb O /CNFs with potentials as anode materials for sodium-ion batteries.