Facile synthesis of T-Nb2O5 nanosheets/nitrogen and sulfur co-doped graphene for high performance lithium-ion hybrid supercapacitors

Li-ion hybrid supercapacitors (Li-HSCs) have attracted increasing attention as a promising energy storage device with both high power and energy densities. We report a facile two-step hydrothermal method to prepare the orthorhombic niobium oxide (T-Nb2O5) nanosheets supported on nitrogen and sulfur co-doped graphene (T-Nb2O5/NS-G) as anode for Li-HSCs. X-ray diffraction and morphological analysis show that the T-Nb2O5 nanosheets successfully and uniformly distributed on the NS-G sheets. The T-Nb2O5/NS-G hybrid exhibits great rate capability (capacity retention of 63.1% from 0.05 to 5 A g(-1)) and superior cycling stability (a low capacity fading of similar to 6.4% after 1000 cycles at 0.5 A g(-1)). The full-cell consisting of T-Nb2O5/NS-G and active carbon (AC) results in high energy density (69.2 W h kg(-1) at 0.1 A g(-1)), high power density (9.17 kW kg(-1)) and excellent cycling stability (95% of the initial energy after 3000 cycles). This excellent performance is mainly attributed to the highly conductive NS-G sheets, the uniformly distributed T-Nb2O5 nanosheets and the synergetic effects between them. These encouraging performances confirm that the obtained TNb2O5/NS-G has promising prospect as the anode for Li-HSCs.