A core/shell structured tubular graphene nanoflake-coated polypyrrole hybrid for all-solid-state flexible supercapacitors

A core/shell tubular structured graphene nanoflake-coated polypyrrole nanotube (GNF/PNT) hybrid is fabricated for all-solid-state flexible supercapacitors. Functionalization of a controlled coating amount of GNFs onto PNTs is achieved via chemical covalent bonds generated by acylation of the N-H positions of the PNT surface with the carboxyl groups of GNFs. The GNF coating not only acts as an efficient surface protector, but also serves as the electron transfer pathway; meanwhile, a controlled coating amount of GNFs optimizes the capacitance of the whole composite. A stable cycling performance and large capacitance as well as high capacitance retention of the GNF/PNT hybrid are therefore achieved. A flexible all-solid-state symmetric supercapacitor device is also assembled, which demonstrates (at 1.8 mA cm^-2) an areal capacitance of 128 mF cm^-2, an energy density of 11.4 μW h cm^-2 at a power density of 720 μW cm^-2, and a cycling stability of over 80% capacitance retention after 5000 cycles. This study demonstrates a facile strategy for designing novel conductive polymers/graphene composites with enhanced cycling stability in all-solid-state flexible supercapacitors and beyond.