Facile and controlled deposition of battery-type nickel sulfide nanostructure on Ni foam for a hybrid supercapacitor

Hybrid supercapacitors combining faradaic and non-faradaic electrodes offer a significant improvement in electrochemical performance. Enhancing the energy storage in hybrid supercapacitors requires the development of binder-free hierarchical nanostructures directly on electrode surfaces, using scalable and cost-effective fabrication methods. The present work develops a straightforward technique to deposit highly electroactive nickel sulfide (NiS) nanostructures uniformly on the nickel foam via the Successive Ionic Layer Adsorption and Reaction (SILAR) method at room temperature by optimizing the number of SILAR cycles. From the fabricated NiS electrodes, the electrode deposited for 30 cycles (N-30s) displayed a maximum areal capacity of 2.08C cm⁻² at the 2 mA cm⁻² current density in a 6M KOH aqueous electrolyte. Additionally, a hybrid-supercapacitor (H-SC) was assembled using N-30s and commercial activated carbon (CAC@Ni foam) as the positive electrode and the negative electrode respectively, which demonstrated a considerable specific capacitance of 47 F g⁻¹ at 2 mA cm⁻². Moreover, the H-SC displayed a specific energy of 14.58 Whkg⁻¹ for 0.214 kWkg⁻¹ specific power with an exceptional retention (92 %) after 10000 charge/discharge cycles. These results demonstrated a route to utilize the directly deposited NiS@Ni nanostructure as a feasible positive electrode material for energy storage devices.