Ultrahigh-energy sodium ion capacitors enabled by the enhanced intercalation pseudocapacitance of self-standing TiNbO/CNF anodes.

In order to increase the capacity and improve the sluggish Na-reaction kinetics of anodes as sodium ion capacitors (SICs), a TiNbO/CNF self-standing film electrode comprised of TiNbO nanosheets and carbon nanofibers has been fabricated electrospinning HTiNbO nanosheets with PAN and subsequent carbonization treatment. The as-prepared TiNbO/CNF film electrode possesses fast Na-ion intercalation kinetics and high conductivity during Na-ion storage, and it displays a high reversible capacity of 324 mA h g at 0.1 A g. Additionally, it also delivers a superior rate capability of 204 mA h g at a high current density of 4 A g, as well as an excellent cycling stability of 97% retention after 2000 cycles at 1 A g in a half-cell test. A prototype TiNbO/CNF//AC SIC full device was assembled by employing the presodiated TiNbO/CNF anode and AC cathode, and it exhibits an high energy density of 129 W h kg at a power density of 75 W kg and a high power density (7560 W kg with 63 W h kg), a good cycling performance of 85% capacitance retention after 10 000 cycles at 1 A g, suggesting that the TiNbO/CNF electrode with excellent performance would be a very promising candidate as the anode for high-performance SICs.