Electrochemical Efficacy of a Ni x S y /WS2 Composite as an Efficient Electrode Material for a High Performance Hybrid Supercapacitor and Aqueous Zn-Ni Battery

Transition metal-based chalcogenide (TMX) has multiple valence states, a high surface area, excellent electronic conductivity, and electrochemical activity with various applications. Nickel sulfide/tungsten disulfide (NiS/Ni3S4/WS2) (NWS) composites are synthesized with three different metal ratios (1:1, 1:2, 2:1) by a two-step solvo-hydrothermal method. The binary NWS composites are enriched with numerous metal active sites to enhance their electrochemical behavior. Half-cell configurations help analyze the electrochemical performance of the NWS composite electrode material. Compared to the as-prepared samples, the NWS (1:1) composite electrode showed the highest specific capacitance of 1,475 F g-1 at a specific current of 1 A g-1, respectively. The hybrid supercapacitor (HSC) is fabricated using N-doped graphene (NG) as the negative electrode and NWS (1:1) composite as the positive electrode with an aqueous electrolyte of 3 M KOH. The fabricated NG//NWS (1:1) device exhibits a specific energy of 39.25 Wh kg-1 with a specific power of 750 W kg-1 at a specific current of 1 A g-1. An NWS (1:1) composite is also applied in an aqueous Zn-Ni battery as a positive electrode and a zinc-deposited graphite sheet (Zn@GS) as a negative electrode, which delivers a specific energy of 171 Wh kg-1 at the specific power of 5.7 kW kg-1.