Synergistic Effect of Redox-Active NiS-Co@C Ternary Nanocomposite for Supercapattery Hybrid Energy Storage Devices

A highly redox-active ternary nickel sulfide and cobalt-anchored carbon nanocomposite (NiS-Co@C) electrochemical electrode is synthesized by a two-step pyrolysis-hydrothermal method using biomass-derived carbon. The high-crystalline hierarchical porous nanostructure provides abundant voids and cavities, along with a large specific surface area, to improve the interfacial properties. The as-synthesized electrode achieved a specific capacity of 640 C g−1 at 1 A g−1, with a capacity retention of 93% over 5000 cycles, revealing outstanding electrochemical properties. Nickel sulfide nanoparticles embedded in the cobalt-anchored carbon framework improved redox activity, ion transport, and conductivity, resulting in a dominant diffusion-controlled battery-type behavior. Moreover, a hybrid supercapattery, based on battery-type NiS-Co@C as the positrode and capacitive-type activated carbon as the negatrode, achieved a maximum specific energy/power of 33 Wh kg−1/7.1 kW kg−1 with a 91% capacity retention after 5000 cycles. The synergistic effect of the combinatorial battery–capacitor behavior of the hybrid supercapattery has improved the specific energy–power considerably, leading the development of next-generation energy storage technologies.