Synthesis of binder-free nanofibers ZnS/MoS2/NiF electrode material for asymmetric supercapacitor applications

Molybdenum disulfides (MoS2) have layered nanostructures which accomplished as potential electrode materials (E-Ms) for lithium-ion batteries and supercapacitors. Herein, binder-free hierarchical MoS2 and heterostructured ZnS/MoS2 E-Ms are synthesized on nickel foam (NiF) via a simple and homemade chemical vapor deposition (CVD) system. The interconnected nanofibers via nanorods improve the porosity, active sites, surface area, structure stability, chemical stability and volume expansion resulting in fast electron and ions kinetic for excellent electrochemical performance of heterostructured ZnS/MoS2/NiF E-Ms. The heterostructured ZnS/MoS2/NiF E-Ms exhibited a maximum specific capacitance (C-sp) of 3540 F/g in contrast to individual MoS2/NiF E-Ms 1666 F/g (1 A/g) owing to their unique nanofibers/nanorods like surface morphology. The interconnected nanostructures of ZnS/MoS2/NiF offered no charge transfer resistance (absence of semicircle) as compared to MoS2/NiF E-Ms (0.51 Omega cm(2)) during the whole kinetic process. The energy density and power density of ZnS/MoS2/NiF E-Ms from 72 to 122 Wh/kg with power densityranging from 250 to 2500 W/kg. Moreover, after 20,000 cycles, >95 % of C-sp is retained by ZnS/MoS2/NiF E-Ms thereby indicating excellent cyclic stability. The Power law and Dunn's model simulations also indicated that the synthesized ZnS/MoS2/NiF E-Ms have both battery-grade and pseudocapacitive behavior. Additionally, assembled ZnS/MoS2/NiF ASC device exhibited maximum C-sp of 494 F/g, energy density 203-109 Wh/kg, power density 860-17,200 W/kg along with cyclic stability of 97 % for 5000 cycles. The unique electrochemical properties of ZnS/MoS2 E-Ms able them to be used as potential candidate for the next generation of best performing pseudocapacitors.