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

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 NiMoO 4 @NiCo 2 O 4 hybrid nanostructure as a positive electrode was prepared through a simple two-step hydrothermal method followed by the annealing process. The NiMoO 4 /NiCo 2 O 4 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 NiMoO 4 @NiCo 2 O 4 hybrid electrodes have considerable applications in the field of energy storage technologies.