Morphology-controlled Co0.5Ni0.5S2-C double-shell porous microspheres for the construction of high-performance asymmetric supercapacitors

In this research, we develop a facile sulfuration treatment approach to synthesize the carbon doped double-shell porous cobalt nickel sulfide microspheres (Co0.5Ni0.5S2-C DSPMs) using CoNi-MOF yolk-shell microspheres (CoNi-MOF YSMs) as the precursor. The obtained Co0.5Ni0.5S2-C DSPMs exhibits a maximum specific capacity of 2011.3 F g -1 at 1 A g -1 due to the unique double-shell porous structure and amorphous carbon. The density functional theory (DFT) shows that cobalt nickel sulfide with the same molar ratio of cobalt and nickel possesses good absorbability and stability toward OH- ion on the thermodynamics, which significantly improves their electrochemical performance. Furthermore, an asymmetric supercapacitor (ASC) device is fabricated by using Co0.5Ni0.5S2-C DSPMs as the cathode and the activated carbon (AC) as the anode. The ASC device exhibits a supreme specific capacity of 182.4 F g -1 at 1 A g -1, a high energy density of 64.85 Wh kg- 1 at the power density of 800 W kg -1, and excellent cycle stability with 92.78% capacitance retention rate at the current density of 8 A g -1 over 5000 cycles. This research pave the way for the development of next-generation energy storage devices using micro/nanocomposite with double-shell porous structure.