Hierarchical carbon nanotube hybrid films for high-performance all-solid-state supercapacitors

Abstract

Electrodes that have high electrical conductivity, large ion-accessible area and good mechanical robustness are highly needed for developing high-performance flexible supercapacitors. Herein, we report the preparation of a carbon nanotube (CNT) hybrid film consisting of large-diameter multi-walled carbon nanotubes (MWCNTs) and small-diameter single-walled carbon nanotubes (SWCNTs) and its application as an electrode for flexible supercapacitors. In the hybrid film, MWCNTs provide a macroporous and robust scaffold while SWCNTs bridge MWCNTs and improve the film's strength and electrical conductivity. Resulting from such a hierarchical structure that could facilitate ion transportation inside of the electrode, the specific capacitance of SWCNTs loaded in hybrid films was increased by about 273% when compared with that of SWCNT films. A thin layer of polyaniline was electrochemically deposited on the hybrid film, forming a composite film with good structural flexibility and high capacitance. Solid-state symmetric supercapacitors assembled using such a composite film electrode showed good rate performance and high cycling stability.