Nickel carbonate Hydroxide-based Core-Triple-Shelled nanofibers with ultrahigh specific capacity for flexible hybrid supercapacitors

Designing novel efficient electrode materials with controlled hierarchical structure and composition for advanced supercapacitors remains a great challenge. Herein, a core-triple-shelled hierarchical GCNF/PANI/NCO nanostructure has been designed and fabricated by sequential growth of the conductive polyaniline (PANI) layers and nickel carbonate hydroxide (Ni2(CO3)(OH)2) nanosheets on the graphene-coated electrospun carbon nanofibers (GCNF) via a facile wet-chemical strategy. Taking full advantage of the free-standing architecture of graphene-coated electrospun carbon nanofibers, high conductivity and flexibility of the PANI layers, and abundant active sites of Ni2(CO3)(OH)2 nanosheets, the optimal GCNF/PANI/NCO (2 h) electrode exhibits a high specific capacitance of 1565F g-1 at 1 A/g and enhanced rate capability, which are higher than those of the GCNF, GCNF/PANI, and GCNF/NCO (2 h) electrodes at the same situation, and also exceeds most of the reported nickel carbonate hydroxide-based electrodes in literature. The superior performance should be mainly ascribed to the collaborative contribution of each component. Moreover, a self-assembled GCNF/PANI/NCO//AC hybrid supercapacitor delivers a high energy density of 35.4 Wh kg-1@750 W kg-1 and a long cycle lifespan. This strategy enables the controllable synthesis of core-triple-shelled hierarchical materials applicable to advanced electrochemical applications.