Nickel-cobalt-molybdenum sulfides with adjustable morphology via coprecipitation and hydrothermal conversion as high-performance electrodes for asymmetric supercapacitors

Abstract

The morphology of a multicomponent transition metal sulfide electrode plays a vital role in the electrochemical properties of advanced supercapacitors. However, the control of hybrid metal sulfide morphology during preparation remains a challenge. This study demonstrated the controlled synthesis of NixCo1-xMoSy (NCMS) nanorods, nanoplate-on-nanoparticles and nanoparticles by adjusting the NaOH concentration of the ethanol-water solution used in the hydrothermal step of a simple coprecipitation-hydrothermal method. The NCMS electrode materials with the nanoplate-on-nanoparticle and nanoparticle morphologies had a higher available surface area for electrolyte penetration and a larger number of pseudocapacitive redox reaction sites during the charge/discharge process in alkaline solution. The NCMS electrode exhibited a high specific capacity of 227 mAh g−1 at 1 A g−1, a good rate capability with 76.7% retention at increasing current densities from 1 to 20 A g−1, and a high cyclability with 70.48% retention at 5 A g−1 after 1000 cycles. An asymmetrical supercapacitor assembled using NCMS as the positive electrode and active carbon as the negative electrode had an energy density of 55 Wh kg−1 at a power density of 850 W kg−1 (1 A g−1). These results demonstrated the excellent applicability of this NCMS electrode material in high-performance supercapacitors.