Lithium-ion supercapacitors have been attracting tremendous research interest due to significantly increased energy density. However, the power density and cycling stability are often sacrificed by poor conductivity and sluggish kinetics of transition metal oxides-based electrode. Herein, we report a composite material based on Nb2O5 nanocrystals in-situ grown on carbon nanotubes (CNTs) with a unique architecture exhibiting superior rate capability and long cycling stability. Even at 100 C-rate with charge/discharge time of 12 s, the composite still possesses a capacitance of ~160 C g-1. A prototype of asymmetric lithium-ion supercapacitor composed of activated carbon cathode and CNT-Nb2O5 composite anode shows significantly improved energy density of ~50 Wh kg-1 with a power of 86.46 W kg-1. Such composite materials with unique architecture hold great promise for future practical applications.