Flexible asymmetric supercapacitor based on Hyphaene fruit shell-derived multi-heteroatom doped carbon and NiMoO4@NiCo2O4 hybrid structure electrodes

Abstract

In accordance with ecological strategies for the production of renewable energy storage systems, herein, starting from the Hyphaene fruit shell (HFS) as a new carbon precursor, multi-heteroatom (O, N, S, P, and Si) self-doped porous carbon was successfully synthesized through carbonization and chemical activation (KOH) processes. The obtained honeycomb-like carbon structure (HFSC2) as negative electrode exhibited excellent electrochemical performance with high cycling stability and high specific capacitance of 337 F g−1 in 3 M KOH electrolyte solution. Meanwhile, the NiMoO4@NiCo2O4 hybrid nanostructure as a positive electrode was prepared through a simple two-step hydrothermal method followed by the annealing process. The NiMoO4/NiCo2O4 on Ni foam exhibits a very high specific capacitance of 1582 F g−1 at a current density of 0.5 A g−1 and excellent cycling stability of 82% after 3000 cycles. Further, for the practical application, the synthesized asymmetric all-solid-state supercapacitor offered high specific capacitance of 63.38 F g−1 (360.26 mF cm−2), a high energy density of 28.5 Wh kg−1 and a high-power density of 3800 W kg−1 at 14.8 Wh kg−1 within a voltage window of 0–1.8 V. These prominent electrochemical performances suggest that Hyphaene fruit shell-derived multi-heteroatom carbon and NiMoO4@NiCo2O4 hybrid electrodes have considerable applications in the field of energy storage technologies.