Synergistic coupling of MnS/Ni3S2 and Co(OH)2 nanosheets as binder-free electrode materials for asymmetric supercapacitors with enhanced performance

The fabrication of electrode materials with a high specific capacitance is essential for the development of enhanced performance supercapacitors. A novel binder-free electrode material, composed of MnS/Ni3S2 and Co(OH)2, was synthesized on nickel foam by hydrothermal, sulfuration, and electrodeposition techniques. The MnS/Ni3S2 exhibited a unique flower-like structure, resulting in a high specific capacitance of 1780 F g−1 at 1 A/g. By optimizing the synthesis conditions through several characterization and electrochemical tests, the MnS/Ni3S2@Co(OH)2 composite was obtained, which displayed an ultrahigh specific capacitance of 2495 F g−1 at 1 A/g and a capacitance retention rate of 86.1% after 5000 cycles at 10 A/g in three-electrode system. The synergistic coupling of MnS/Ni3S2 and Co(OH)2, along with the conductive nickel foam substrate, donated towards the excellent electrochemical performance. Furthermore, the MnS/Ni3S2@Co(OH)2//AC asymmetric supercapacitor (ASC) device was constructed with MnS/Ni3S2@Co(OH)2 as positive electrode, activated carbon (AC) as negative electrode and 1 M KOH solution as electrolyte, demonstrated a high energy density of 68.6 Wh kg−1 at 750 W kg−1 and excellent cycle stability with 91.2% capacitance retention after 10,000 cycles at 15 A/g. The outstanding electrochemical properties observed in both the pre-electrodeposition and post-electrodeposition samples indicate the effectiveness of reasonable design and construction of composite as a pathway for producing electrode materials with exceptional performance.