T-Nb 2 O 5 /C Nanofibers Prepared through Electrospinning with Prolonged Cycle Durability for High-Rate Sodium-Ion Batteries Induced by Pseudocapacitance.

Homogeneous ultrasmall T-Nb2 O5 nanocrystallites encapsulated in 1D carbon nanofibers (T-Nb2 O5 /CNFs) are prepared through electrospinning followed by subsequent pyrolysis treatment. In a Na half-cell configuration, the obtained T-Nb2 O5 /CNFs with the merits of unique microstructures and inherent pseudocapacitance, deliver a stable capacity of 150 mAh g-1 at 1 A g-1 over 5000 cycles. Even at an ultrahigh charge-discharge rate of 8 A g-1 , a high reversible capacity of 97 mAh g-1 is still achieved. By means of kinetic analysis, it is demonstrated that the larger ratio of surface Faradaic reactions of Nb2 O5 at high rates is the major factor to achieve excellent rate performance. The prolonged cycle durability and excellent rate performance endows T-Nb2 O5 /CNFs with potentials as anode materials for sodium-ion batteries.