Engineering Nanoscale Nickel Sulfide by a “Reduction-Restriction” Strategy for High Performance Hybrid Supercapacitor

Nanostructured materials usually exhibit superior electrical properties than bulk-structured materials, but conventional preparation methods are prone to produce bulk-structured nickel sulfide, leading to unsatisfactory electrochemical properties. In this work, we proposed a novel “reduction-restriction” strategy to synthesize nanoscale β-NiS via a one-step hydrothermal process. We found the introduction of strong reductants accelerates the crystal nucleation and growth of nickel sulfide, and limits further crystal growth, thus generating nanoparticles. Benefiting from the advantages brought by nanoscale effect, both of NS-15mLNaBH4 (β-NiS nanoparticles) and NS-100µLN2H4 (β-NiS nanoparticles) electrodes deliver an outstanding specific capacity of 254.1 mAh g-1 and 256.9 mAh g-1 at 1Ag-1, respectively, obviously higher than bulk-structured NS-0 (β-NiS/Ni3S4) electrode (171.0 mAh g-1 at 1Ag-1). The assembled NS-100µLN2H4//rGO hybrid supercapacitor shows a high energy density of 69.3Whkg-1 at a power density of 399.8Wkg-1. This work offers a novel mechanism and approach for fabrication of nanoscale metal sulfides from the perspective of controlling crystal nucleation and growth.