Porous fibers of carbon decorated T-Nb2O5 nanocrystal anchored on three-dimensional rGO composites combined with rGO nanosheets as an anode for high-performance flexible sodium-ion capacitors

Flexible sodium ion capacitors have been developed to overcome the rigid characteristic of traditional rechargeable electronic devices and integrate into next-generation smart fabric system to provide high energy density and high power density. Here, we firstly synthesized nanocomposites of carbon decorated T-Nb2O5 nanocrystals anchored on rGO nanosheets (T-Nb2O5-C-rGO) via a solvothermal method and calcination. Afterwards the obtained nanocomposites were combined with rGO to fabricate T-Nb2O5-C-rGO/rGO porous fibers through restricted hydrothermal treatment. The self-supporting T-Nb2O5-C-rGO/rGO fibers showed a high capacity (≈240 mAh g−1 at 0.1 A g−1), good rate performance and good cycle stability (about 68% retain at 1 A g−1 after 1000 cycles). The excellent electrochemical performance is mainly attributed to the three-dimensional porous rGO fiber structure which enhances the transfer dynamics of ion and electron, and carbon coating layer which improves the stability and compatibility of heterogeneous interface between T-Nb2O5 and rGO. Furthermore, the sodium-ion capacitor using the T-Nb2O5-C-rGO/rGO fiber anode and porous activated carbon composite (AC/rGO) fiber cathode exhibited high energy (≈40 Wh kg−1 at power density of 436 W kg−1) with a long cycle life (about 70% retain at 1 A g−1 after 2000 cycles) in the potential range of 0.1–3.9 V. [Display omitted]