A facile strategy for the synthesis of manganese-doped nickel sulfide nanosheets and oxygen, nitrogen-enriched 3D-graphene-like porous carbon for hybrid supercapacitor.

High-performance of supercapacitors mainly depends on their electrode active materials. Herein, the surface morphology and performance of nickel sulfide (NiS) have been engineered by doping with manganese (Mn). The Mn-NiS nanostructure was synthesized using a facile co-precipitation technique. The feeding ratio of Mn/Ni has a significant impact on the properties. When the Mn/Ni feeding ratio is 1:2, a nanosheet structure is formed and it exhibiting a maximum specific capacitance of 815 g−1 at 2 A−1 and remarkable cycle stability. Besides, oxygen (O) and nitrogen (N) enriched 3D-graphene-like porous activated carbon (ONAC) has been derived from biomass. A hybrid supercapacitor (HSC) is built with Mn-NiS NSs serving as the positive electrode, ONAC as the negative electrode, and PVA/KOH gel as a polymer-gel electrolyte. The constructed device has an impressive specific energy of 44.2 W h kg−1 at 825 W kg−1 specific power. The device also showed exceptional cycling durability with specific capacitance retention of 90% after 5000 charge/discharge cycles at 8 A g−1. HSCs, on the other hand, have been successfully lighted by light-emitting diodes (LEDs), displaying greater energy storage performance. Thus, the present work offers a straightforward way to make nanostructure materials with excellent supercapacitor performance. [Display omitted] • Hierarchical Mn-NiS NSs has achieved with optimum of 1:2 Mn/Ni feeding ratio. • 3D-graphene like O,N-enriched porous carbon has derived from lily flower petals. • Assembled HSC device delivered ultrahigh energy density of ∼44 Wh kg−1 at 825 W kg−1. • The device has specific capacitance retention of 90% after 5000 charge/discharge cycles at 8 A g−1. [ABSTRACT FROM AUTHOR]