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.