Vertically aligned carbon nanotube@MnO₂ nanosheet arrays grown on carbon cloth for high performance flexible electrodes of supercapacitors

Vertical alligned carbon nanotube@MnO₂ (VACNT@MnO₂) arrays grown on carbon cloth were prepared as high performance flexible electrodes for supercapacitors. VACNTs first grew on carbon cloth with the method of plasma enhanced chemical vapor deposition (PECVD) to obtain firm connection between CNTs and carbon cloth, and δ-MnO₂ nanosheets were deposited on the surface of VACNTs to form a VACNT@MnO₂ core-shell structure. The VACNT@MnO₂ on carbon cloth (VACNT@MnO₂/CC) exhibited a remarkable specific capacitance (235 F g^-1 at the scan rate of 2 mV s^-1 based on the total mass of VACNTs and MnO₂), an excellent rate performance with a specific capacitance of 188 F g^-1 at 100 mV s^-1 and a stable cycling ability (nearly 100% retention after 5000 charge/discharge cycles at 5 A g^-1). The fabricated symmetric supercapacitor from the self-supported VACNT@MnO₂/CC without any additive reagents had the same electrochemical energy storage performance when this supercapacitor was bent 180°, revealing the excellent flexibility of our prepared flexible electrodes. The excellent performances in electrochemical properties and flexibility mainly originated from a strong mechanical coupling between CNTs and CC as well as sufficient contact between the electrolyte and the surface of MnO₂ nanosheets in such an arrayed structure.