Flexible Nb2O5 nanowires/graphene film electrode for high-performance hybrid Li-ion supercapacitors

The hybrid Li-ion electrochemical supercapacitor (Li-HSC) combining the battery-like anode with capacitive cathode is a promising energy storage device boasting large energy and power densities. Orthorhombic Nb2O5 is a good anode material in Li-HSCs because of its large pseudocapacitive Li-ion intercalation capacity. Herein, we report a high-performance, binder-free and flexible anode consisting of long Nb2O5 nanowires and graphene (L-Nb2O5 NVVs/rGO). The paper-like L-Nb2O5 NWs/rGO film electrode has a large mass loading of Nb2O5 of 93.5 wt% as well as short solid-state ion diffusion length, and enhanced conductivity (5.1 S cm(-1)). The hybrid L-Nb2O5 NVVs/rGO paper electrode shows a high reversible specific capacity of 160 mA h g(-1) at a current density of 0.2 A g(-1), superior rate capability with capacitance retention of 60% when the current density increases from 0.2 to 5 A g(-1), as well as excellent cycle stability. The Li-HSC device based on the L-Nb2O5/rGO anode and the cathode of biomass-derived carbon nanosheets delivers an energy density of 106 Wh kg(-1) at 580 W kg(-1) and 32 Wh kg(-1) at a large power density of 14 kW kg(-1). Moreover, the Li-HSC device exhibits excellent cycling performance without obvious capacitance decay after 1000 cycles. (C) 2016 Elsevier B.V. All rights reserved.