Fast lithium-ion storage of Nb2O5 nanocrystals in situ grown on carbon nanotubes for high-performance asymmetric supercapacitors

Abstract

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 oxide-based electrodes. 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 an asymmetric lithium-ion supercapacitor composed of an activated carbon cathode and a CNT–Nb₂O₅ composite anode shows significantly improved energy density of ∼50 W h kg⁻¹ with a power of 86.46 W kg⁻¹. Such composite materials with unique architecture hold great promise for future practical applications.