Facile Synthesis of Ni_xCo_3−xS₄ Microspheres for High-Performance Supercapacitors and Alkaline Aqueous Rechargeable NiCo-Zn Batteries

Abstract

Electrochemical energy storage devices (EESDs) have caused widespread concern, ascribed to the increasing depletion of traditional fossil energy and environmental pollution. In recent years, nickel cobalt bimetallic sulfides have been regarded as the most attractive electrode materials for super-performance EESDs due to their relatively low cost and multiple electrochemical reaction sites. In this work, NiCo-bimetallic sulfide NixCo3−xS4 particles were synthesized in a mixed solvent system with different proportion of Ni and Co salts added. In order to improve the electrochemical performance of optimized Ni2.5Co0.5S4 electrode, the Ni2.5Co0.5S4 particles were annealed at 350 °C for 60 min (denoted as Ni2.5Co0.5S4-350), and the capacity and rate performance of Ni2.5Co0.5S4-350 was greatly improved. An aqueous NiCo-Zn battery was assembled by utilizing Ni2.5Co0.5S4-350 pressed onto Ni form as cathode and commercial Zn sheet as anode. The NiCo-Zn battery based on Ni2.5Co0.5S4-350 cathode electrode delivers a high specific capacity of 232 mAh g−1 at 1 A g−1 and satisfactory cycling performance (65% capacity retention after 1000 repeated cycles at 8 A g−1). The as-assembled NiCo-Zn battery deliver a high specific energy of 394.6 Wh kg−1 and long-term cycling ability. The results suggest that Ni2.5Co0.5S4-350 electrode has possible applications in the field of alkaline aqueous rechargeable electrochemical energy storage devices for supercapacitor and NiCo-Zn battery.

Keywords

• Ni_xCo_3−xS₄ structures
• micro/nanostructures
• supercapacitors
• Ni-Zn batteries