Design of Nb2O5/graphene hybrid aerogel as polymer binder-free electrodes for lithium-ion capacitors

The imbalance between energy density and power density largely limits lithium-ion hybrid capacitor (Li-HEC) advance for various applications. In this work, we report on the construction of a binder-free and porous electrode, which is self-standing T-Nb2O5/graphene hybrid aerogels, as Li-intercalating pseudocapacitive electrodes of Li-HECs. The aerogels, with ultrafine T-Nb2O5 nanorods (10 40 nm) uniformly growing on the surface of graphene, feature short lithium-ion transport length, large specific surface area, 3D porous structure and good conductivity, and thus demonstrate both reversible specific capacity (190 mAh/g at 1 C) and good rate capability (90 mAh/g at 20 C). Most importantly, Li-HEC devices using activated graphene foam as binder-free cathode can achieve excellent energy densities (53 and 19.7 Wh/kg at power of 355 and 2009 W/kg, respectively) and remarkable cycling performance (capacitance retention of 89% after 3000 cycles), benefitting from good matching between cathode and anode as well as their fascinating microstructures.