Novel graphene nanosheet-wrapped polyaniline rectangular-like nanotubes for flexible all-solid-state supercapacitors

For the development of high-capacity flexible supercapacitors (SCs), a reduced graphene oxide/polyaniline (rGO/PANI) hybrid film with a hierarchical three-dimensional structure, in which PANI nanotubes are sandwiched in rGO nanosheet skeleton, is designed and prepared via vacuum filtration. The rectangular-like PANI nanotubes have a hollow structure with a wall thickness of ca. 100 nm, which can increase the accessible surface area and minimize the ion transfer distance. Additionally, rGO nanosheets act as conductive skeleton to improve the conductivity of active materials and provide some capacitance due to EDLC properties of rGO. As a result, the composite electrode shows a remarkable specific capacitance of 850 F g⁻¹ at 1 A g⁻¹, and superior cycling stability with only 6.8% of the specific capacitance loss after 10000 cycles. The assembled flexible all-solid-state SCs give a high specific capacitance of 208 F g⁻¹ (1 A g⁻¹) and a good rate capacitance, as well as outstanding cycling stability with 87.3% of the initial capacitance retained after 10000 cycles. Furthermore, no structure failure or performance loss at various bending angles is observed. This method may provide a new route for the fabrication of flexible energy storage devices.