Nb₂O₅ nanotubes on carbon cloth for high performance sodium-ion capacitors

Hybrid sodiumion capacitors (SICs) bridge the gap between the supercapacitors (SCs) and batteries and have huge potential applications in large-scale energy storage. However, designing appropriate anode materials with fast kinetics behavior as well as long cycle life to match with the cathode electrodes remains a crucial challenge. Herein, Nb₂O₅ nanotubes and nanowire-to-nanotube homo-junctions were directly grown on the carbon cloth (CC) via a simple hydrothermal process through regulating the pH value of solution. The as-prepared Nb₂O_s@CC nanotubes displayed a high reversible capacity of 175 mA h g at the current density of 1 A g with the coulombic efficiency of 97% after 1500 cycles. Besides, the SICs fabricated with Nb₂O_s@CC and activated carbon (AC) electrode materials showed a high energy density of 195 W h kg ' at 120 W kg”1, a power density of 7328 W kg ' at 28 W h kg and 80% of the capacitance retention after 5000 cycles. Additionally, the flexible SIC devices can operate normally at various bendable conditions. The Nb₂O_s@CC nanotubes in this work can be promising electrode materials in flexible and wearable energy storage devices.